What is Power?

Click the "play" button below and observe what happens. (Note: The video has no audio.)

Power vs. Energy

Both cyclists did the same amount of work (they both pedaled 10 miles), and used the same amount of energy (218 calories). The blue cyclist, however, demonstrated the most power, because he did the equivalent amount of work as the red cyclist, but in a faster time.

Measuring Power

Units of Power are not the same as units of energy (i.e., Btus, calories). Units of power are measured in terms of units of energy used per some unit of time.

Examples of Units of Power include:

• Watt (W) = 1 joule of energy per second or 1 J/S
• BTU per hour (BTUs/h) = 1,055J
• Horsepower (hp) = 550 foot-pounds per second or 550 ft lb/S
• Calories per second (cal/sec)
• Kilowatt (kW) = 1,000 watts

Calculating Power

Power can be determined by the following formula:

Power & Cost of Energy

We can also use a version of the Power formula to determine Cost of Energy:

Calculating Energy Use

How is energy use of Home Appliances calculated?

You just learned in a previous discussion on power that:

By modifying this formula slightly, we can determine Energy Consumption per Day:

Where:

• Energy Consumption will be measured in Kilowatt hours (kWh) - like on your utility bills.
• Power Consumption will be measured in Watts
• Hours used per Day will be the actual time you use the appliance.

Since we want to measure Energy Consumption in Kilowatt hours, we must change the way Power Consumption is measured from Watts to Kilowatts (kWh). We know that 1 kilowatt hour (kWh) = 1,000 Watts hours, so we can adjust the formula above to:

What is the energy consumption of a refrigerator with a wattage rating of 700 Watts when it is operated for 24 hours a day?

Step 1

To solve, use the following formula:

Where:

Energy Consumption = Watt Hours (Wh) or KiloWatt Hours (kWh)

Power Consumption = Watts (W) or kW (KiloWatts)

Number of Hours Operated = Hours (h) For the example above:

Energy Consumption = 700 W x 24 h

Energy Consumption = 16800 W h

Step 2

To convert from Wh to kWh, remember that 1kWh = 1000 Wh

To solve, set up as a ratio and use linear algebra to solve for ?.

Locating Wattage

You can usually find the wattage of most appliances stamped on the bottom or back of the appliance, or on its "nameplate." The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time.

You can find the wattage information on the bottom or back of many appliances.

Credit: thefamily8 from flickr is licensed under BY CC 2.0

A refrigerator, although turned "on" all the time, actually cycles on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals.

To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.

The table below shows wattage of some typical household appliances.

Amperes and Voltage

Credit: © Penn State
is licensed under CC BY-NC-SA 4.0

Click for a description
of the amp meter.

The image shows an ammeter cycling through five different measurements. 118.9 Volts, 7.49 Amps, 885 Watts, 59.9 Hertz, and 0.01 Kilowat Hours.

If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amperes) and multiplying that by the voltage used by the appliance.

Most appliances in the United States use 120 volts. Larger appliances, such as clothes dryers and electric cooktops, use 240 volts. The amperes might be stamped on the unit in place of the wattage.

If not, find an ammeter to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment.

Take a reading while the device is running; this is the actual amount of current being used at that instant.

Phantom Loads

Also note that many appliances continue to draw a small amount of power when they are switched "off."

These "phantom loads" occur in most appliances that use electricity, such as VCR, televisions, stereos, computers, and kitchen appliances.

Most phantom loads will increase the appliance's energy consumption a few watts per hour. These loads can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance.

Review

Watch this 3 minute 41 second video review Lesson 1

Extra Resources

For more information on topics discussed in Lesson 1, see these selected references:

• Energy Information Administration ("Energy Kid's Page")
• A Consumer's Guide to Energy Efficiency and Renewable Energy

Welcome to Lesson 2!

You are already to Lesson 2: Energy Supply and Demand. These energy supply and demand lessons will explore more about energy resources. Basically, you will be able to appreciate global and national consumption patterns. We will go over what kinds of energy we have been consuming, how much we have been consuming, and how we compare with the rest of the world, etc., over the past few decades. Based on those patterns, we can also deduce some information about how much energy we use to do a job; energy intensity. What kind of energy sources we will be needing, and how much we will be needing based on the past trends?

We will also look at energy reserves. Do we have those? Will we need more renewables, batteries, coal, more oil, or more gas? Can we (sustainably) use any of those resources? If we can, great, if not, what do we do? We will be doing those kinds of energy analysis. So, obviously, you are going to see a lot of numbers and statistics. One of the questions that I always get is: Hey, do I have to remember all these numbers? In 2019, petroleum and natural gas accounted for 69 % of energy consumption in this country, and renewables accounted for 11% of the electricity generated by utility companies.

Do we have to remember these numbers? My advice is, you don’t have to remember everything but you need to get the main message behind these numbers. In other words, you have to know the fact that petroleum and natural gas are the main energy sources. Similarly, over 75% of our oil products or petroleum products are used for transportation. So, we need to know that transportation is basically run by petroleum; petroleum is mostly used for transportation. That is the message. You don’t need to remember the exact numbers. But if there is something that has very insignificant or significant quantities, you should note that. For example, renewable energy sources supply about 10% of our energy source (although the exact number is about 11%). That is the message. You don’t need to worry about whether it is 9.2 or 9.5 or 8.5 or 11.2%. So just to give you a clue, you don’t have to worry about the exact numbers, but the message that is conveyed using these numbers is what you have to concentrate on. And we will also have one numerical type of problem in this lesson. That problem will be predicting the energy needed for the future. The problem follows an exponential function, and we will talk about that, and there will be a few numerical problems for you to practice.

See the Calendar tab in Canvas for due dates/times.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

Energy consumption numbers are always reported a few years behind, so we are always looking into the past before we plan for the future. As of 2021, The world's total primary energy consumption was about 176,000 TWhs (580 Quadrillion Btus).

Table 2.1 below shows various regions and total primary energy consumption history.

From the Table 2.1, it can be seen that the energy consumption is high for the Far East and Oceania. The amount of energy used depends on the economic prosperity of the nation and the population of the country. The North American region includes Canada, the United States, and Mexico. The Far East and Oceania include developed nations such as Japan and Australia, and densely populated developing nations such as China and India. Obviously, due to highly populated countries like China and India, total energy consumption does not reflect the quality of life of the people in those countries. Figure 2.1 shows the energy per capita consumption over the last 30 years. As can be seen from the graph that Far East and Oceania used a lot of energy as a region, but per capita energy consumption is relatively low implying that if each person in that region would consume as much as in North America, that Region's energy consumption would skyrocket.

Per Capita Energy Consumption (MMBTU/person) every ten years.

Credit: Sarma Pisupati

The productivity of a country is measured by the total value (dollars) of goods and services, called Gross Domestic Product (GDP), produced by its people. Therefore, the average value of goods and services produced by each person - the GDP per capita of a country - is an indicator of the quality of life.

Energy intensity is the relationship between energy consumption and growth in gross domestic product (GDP), and it is an important factor that affects changes in energy consumption over time.

• In industrialized countries, history shows the link between energy consumption and economic growth to be a relatively weak one, with growth in energy demand lagging behind economic growth.
• In developing countries, however, the link between energy consumption and economic growth have been more closely correlated with energy demand growing in parallel with economic expansion.

The total primary energy consumption of the world in 2015 was 570 Quadrillion Btus and in 2017 it increased to 582.4

Energy Consumption as a Function of Quality of Life in Industrialized Countries

Credit: Sarma Pisupati

Energy Consumption as a Function of Quality of Life in Developing Countries

Credit: Sarma Pisupati

Global Energy Consumption and GDP per person

In general, as the GDP (Gross Domestic Product) per person of any country increases, the amount of energy that is consumed is also expected to increase.

• For developing nations, the correlation is much stronger.
• For developed nations, the correlation is weak.

For example, Iceland, Finland, the United States, and the Netherlands, with similar GDP per capita, have significant differences in energy consumption per capita. In other words, to produce one dollar's worth of goods and services, the U.S. uses twice the energy of the Netherlands. Similarly, Iceland uses four times the energy of the Netherlands.

Energy Intensity

Credit: Sarma Pisupati

Energy Consumption Differences

The differences in energy consumption among countries are the result of:

• efficiency of industrial, transportation, commercial, and residential energy,
• climatic and geographical areas of a country,
• lifestyles (use of more gas guzzling cars and SUVs and bigger sized houses), and
• the nature of the products produced by the nation's industries.

New York City

Credit: Superheros and Villains by Andreas Komodromo is licensed under CC BY-NC 2.0

Bangladesh

Credit: Signs on the river bank by abrinsky is licensed under  BY-NC-SA-2.0

Click here to see Global Average Change in Energy Production by Fuel 

and determine production of energy which energy sources decreased over the last 5 decades.

The world energy requirements are projected by several energy companies such as British Petroleum and Exxon Mobil and international agencies like International Energy Agency (IEA) and US Energy Information Administration (EIA). The United States Department of Energy projects strong growth for worldwide energy demand over the 28-year projection period from 2012 to 2040. Although these projections or forecasts are based on the same principles, they differ slightly. They are also often wrong! For example, the rate of renewable adoption is continuously underestimated. Detailed projections of each organization can be seen through the following external links.

• International Energy Agency
• British Petroleum
• Exxon Mobil
• US Energy Information Administration (EIA)

According to International Energy Outlook 2019,

• Manufacturing centers are shifting toward Africa and South Asia, especially India, resulting in energy consumption growth. Most economic growth happens in non-OECD countries, where GDP per person nearly triples from 2018 to 2050.
• The total world energy consumption is likely to increase from 591 quadrillion Btus in 2016 to 910 quadrillion Btus in 2040, an increase of 54%.
• Most economic growth happens in non-OECD countries, where GDP per person nearly triples from 2018 to 2050. Most energy-intensive manufacturing shifts to non-OECD Asia and, increasingly, to India.

The world's GDP (expressed in purchasing power parity terms) rises by 2.4%/year from 2018 to 2040. The fastest rates of growth are projected for the emerging, non-OECD countries, where combined GDP increases by 3.5%/year. In OECD countries, GDP grows at a much slower rate of 1.5%/year over the projection period.

The World’s energy supply sources

Before the global pandemic, the World’s energy supply sources followed long-term trends, with new fuels increasing in share and old fuels losing ground. Below, you can see consumption history for the years 1990 to 2018.

Figure 2.3. Global Energy Supply by Source. ktoe means kiltons of oil equilivents.

Credit: “World total energy supply by source, 1971-2018”  International Energy Agency. August 27, 2020.

Here we can see the role of renewables and natural gas quickly growing.

Figure 2.3a. Global Energy Supply By Percent.

Credit: International Energy Agency

Three of the world’s largest energy sources

Energy Consumption and Electricity Projections

According to International Energy Outlook 2019, the strongest growth in electricity generation is projected to occur among the developing, non-OECD nations. Increases in non-OECD electricity generation average 2.5%/year from 2012 to 2040, as rising living standards increase demand for home appliances and electronic devices, as well as for commercial services, including hospitals, schools, office buildings, and shopping malls. In the OECD nations, where infrastructures are more mature and population growth is relatively slow or declining, electric power generation increases by an average of 1.2%/year from 2012 to 2040.

Fig 2.5 World energy consumption by type.

Credit: “Primary Energy Consumption by Fuel, World.”
US Energy Information Administration, International Energy Agency. 2010.

Projections of Energy consumption by use.

mage credit here

Credit: “Primary Energy Consumption, World and Consumption by Fuel for Power Generation, World.”
US Energy Information Administration, International Energy Agency. 2010.

As can be seen from the figures, the role of renewables is expected to change dramatically in the coming years.  What a transition!

Nuclear Power

Worldwide, electricity generation from nuclear power is projected to remain largely unchanged into 2040.

According to International Energy Outlook projections by US Department of Energy (US DOE), there is still considerable uncertainty about the future of nuclear power, and a number of issues could slow the development of new nuclear power plants. Issues related to plant safety, radioactive waste disposal, and proliferation of nuclear materials continue to raise public concerns in many countries and may hinder plans for new installations. Although the long-term implications of the disaster at Japan's Fukushima Daiichi nuclear power plant for world nuclear power development are unknown, Germany, Switzerland, and Italy have already announced plans to phase out or cancel all their existing and future reactors. In contrast, developing Asia is poised for a robust expansion of nuclear generation. Most of the increase is by China's addition of 139 gigawatts (GW) of nuclear capacity from 2012 to 2040.

In a nuclear plant, heat is produced by nuclear fission (splitting of an atom's nucleus into many new atoms) inside uranium fuel. As a result of fission, heat energy is released and the steam spins a turbine generator to produce electricity.

Renewables

Sizable growth in the world’s consumption of renewable energy resources is projected over the next 25 years. Much of the projected growth in renewable generation is expected to result from the completion of solar installations all throughout the world. Dramatic reductions in the cost of solar panels has led to this source being one of the cheapest forms of electric power generation as of 2020. In 2020, 90 % of all new electric power generation installations were renewable across the globe.

In hydroelectricity, mechanical energy from the water being pulled downward by gravity is converted to electrical energy. More specifically, a hydroelectric generator directs the flow of water through a turbine, which extracts the kinetic energy from the movement of the water and turns it into electricity through the rotation of electrical generators. Hydropower is the largest single renewable electricity source today, providing 16% of world electricity at competitive prices. It dominates the electricity mix in several countries, developed, emerging, or developing. However, wind and solar are quickly catching up.

For a long time, growth in the world and the U. S. energy consumption as a function of time, follow what is known as exponential function. Now it looks like we have switched to linear growth, but time will tell if this is a permanent change.  The exponential increase is characterized as follows. The amount of change (increase in energy consumption) per unit time is proportional to the quantity (or consumption) at that time.

$$\frac{\Delta N}{\Delta t}\propto N$$

or

$$\frac{\Delta N}{\Delta t}=\lambda N$$

Where Greek letter Δ(delta) is the change or increment of the variable and λ (lambda) is the growth rate. After some mathematical methods, it can be shown that the equation changes to the form

$$N=N_0{e}^{\lambda t}$$
where e is a constant = 2.71

We can determine how long it takes for N0 to become 2N0 (twice its original number or double). That time period is called doubling time. After some mathematical steps it can be written as:

Until so far that the energy requirement is going to increase in the future and also that the U.S. and the rest of the world will depend to some extent on fossil fuels. These fossil fuels are non-renewable fuels with a finite lifetime. So, the question is: Will we have enough supply for future energy requirements?

The answer to this question depends on the quantity of fossil fuels we have in the ground. Energy sources that have been discovered but not produced cannot be easily measured. Trapped several feet below the surface, they cannot be measured with precision. There are several terms used to report the estimates of the energy resources. The most commonly used terms are “reserves” and “resources.”

• "Reserves" represent that portion of demonstrated resources that can be recovered economically with the application of extraction technology available currently or in the foreseeable future. Reserves include only recoverable energy.
• “Resources” represent that portion of the energy that is known to exist or even suspected to exist, irrespective of technical or economic viability. So reserves are a subset of resources.

As of 2016, total world proved recoverable reserves of coal were estimated at 948 billion short tons.

Five countries have nearly 73% of the world's coal reserves:

• United States—28%
• Russia—18%
• China—13%
• Australia—9%
• India—7%

Based on data from OPEC (Oil Producing and Exporting Countries), the highest proved oil reserves including non-conventional oil deposits are shown in the graphic below.

OPEC share of world crude oil reserves, 2018

Source: Opec

Based on data from BP (British Petroleum), proved gas reserves were dominated by three countries: Iran, Russia, and Qatar, which together held nearly half the world's proven reserves. According to the US CIA The World Factbook, the US has the 5th largest reserves of natural gas. Due to constant updates about the shale gas estimates, these are difficult to say with certainty.

How Long Will the Reserves Last?

How long these reserves do last depends on the rate at which we consume these reserves. For example, let’s assume that we have $100,000 in the bank (reserves) and if we draw 10,000 dollars every year (consumption) the reserve will last for 10 years (\$100,000/\$10,000 per year). However, in this case, we are assuming that we do not add any money to our deposit, and we do not increase our withdrawal.

This is generally not true in the case of life of an energy reserve. We may find new reserves, and our energy consumption or production can also increase. In the case of energy reserve, although we know that we might find new resources, we do not know how much we could find. But the consumption can be predicted with some accuracy based on the past rates.

Lifetime of current reserves at constant consumption

We can calculate the life of current petroleum reserves by dividing the current reserves by current consumption.

• At the current rate of consumption, the approximate lifetime of the world’s petroleum, natural gas, and coal reserves is 50 years, 52.8 years, and 153 years, respectively. (BP Statistical Review of World Energy)
• At the current rate of consumption, the current U. S. petroleum, natural gas, and coal reserves will last approximately for 4.88 years, 12.2 years, and 258 years, respectively.

It is important to note that the entire U.S. petroleum consumption is not coming from the U.S. reserves because we import more than one half of the consumption. Because we import more than one half of the consumption, the petroleum reserves at the current rate will last about 11 years. If the consumption increases in the future, the life will be less. However, there is also a chance of adding more reserves with more exploration and discoveries. The increase in consumption can change depending on the price of petroleum and other alternative fuels. Likewise, us moving to electric cars and harnessing unconventional oil reserves can extend the lifetime of these reserves.

Therefore, these lifetimes are not carved in stone. It can be debated whether the U.S. reserves will last for 6 years or 10 years or even 20 years, or we may never run out! But there is increasing consensus that we must change our lifestyle. Even if we won't run out, the environmental consequences of continued use are pushing us to change anyway, but more on that later..

The R/P ratio can change from year to year, similar to our bank balance. We can add more if we make more or consume more. That changes the time we can draw on the balance.

The following figures illustrate that these ratios changed.

Fig Variation of R/P ratio Over Time for Oil

Credit: Data from BP Statistical Review of World Energy

Therefore, we must conserve, innovate (get more with less), or learn to live without these resources.

US Energy Supply and Demand

When focusing on the energy supply and demand, it can be helpful to see where the energy is going. Which of our daily activities consume the most energy? Several agencies track this very closely.

The 2019 energy flow chart released by Lawrence Livermore National Laboratory details the sources of energy production, how Americans are using energy and how much waste exists.

Source for a clearer image: Lawrence Livermore National Laboratory (LLNL)

Globally, many interesting transitions are occurring. While the U.S. was once the top consumer of energy, China claimed this title in 2009.

As a result of innovations in oil and gas extraction, U.S. imports have dropped considerably. 

US Energy Imports between 1950 and 2019

Credit: EIA Energy Explained

Looking at the U.S. Energy Profile,  It can be seen from the imports profile that the US Crude oil imports have significantly reduced between 2005 and 2019 from a peak of 25 Quadrillion BTUs. Another significant change that can be noted is that the US is now exporting natural gas (below zero on the y axis) instead of importing it. Although crude oil is imported, US exports finished petroleum products resulting in less net imports. As a matter of fact, US total energy exports exceeded the imports in 2019 since 1950.

The top five countries (sources) of US total petroleum in 2019 were Canada (49%), Mexico (7%), Saudi Arabia (6%), Russia (6%) and Columbia (4%).

The U.S. also ranks:

• first in worldwide reserves of coal;
• sixth in worldwide reserves of natural gas;
• eleventh in worldwide reserves of oil.

US Energy Consumption by Source and the chart of the US Energy consumption by source and user sector shows each energy source and the amount of energy it supplies in British thermal units (BTU). Petroleum is the leading source of energy in the US in 2019 with 36.72 quadrillion BTUs. Next is natural gas with 32.10 quadrillion BTUs. Coal supplies 11.31 quadrillion BTUs of energy. Renewable energy and nuclear power are responsible for 11.46 and 8.46 quadrillion BTUs respectively. Of the total petroleum consumption, 72% is used for transportation and another 23% is used by the industrial sector. Similarly, 35% of the natural gas (largest fraction) is used for power generation. On the other hand, 76% of the residential and commercial energy needs are met by natural gas. The actual percentages are not required to be memorized but answers to the questions such as: Which fuel is most used by power plants for power generation? Which sector uses petroleum the most? Approximately what fraction of the electricity is generated by renewable energy? (10, 25, 50 or 90) What is the primary purpose of coal use? etc. need to be answered.

US Energy Consumption by Source and Sector

The graph shows how dependent the U.S. is on our petroleum supply, as it accounts for almost 37% of our energy. Our next two highest sources of energy, like petroleum, are non-renewable and include natural gas and coal. Only about 11%  of our energy comes from renewable energy sources such as wood and water (hydroelectricity). According to Energy Information Administration, US renewable energy consumption surpassed coal for the first time in over 130 years in 2019. Of the 4.12 trillion kWh of electricity generated in the US, 38% was from natural gas, coal accounted for about 23% and nuclear adding another 20%. Renewable sources contributed to 17% of the total electricity generated.

In 2019, fossil fuels made up 81% of total U.S. energy consumption, the lowest fossil fuel share in the past century. According to EIA projections, the percentage declines to 76.6% by 2040. Policy changes or technology breakthroughs that go beyond the trend improvements could significantly change that projection. In 2019, the renewable share of energy consumption in the United States was its largest since the 1930s at nearly 11.7%. The greatest growth in renewables over the past decade has been in solar and wind electricity generation. Liquid biofuels have also increased in recent years, contributing to the growing renewable share of total energy consumption. 2020 was the first year that renewables surpassed coal consumption in the U.S.

US Energy Consumption Over Time

US Primary Energy Consumption History in Quadrillion BTUs

Credit: US EIA, Energy Monthly Review Jan. 2021

The most significant decline in recent years has been coal: U.S. coal consumption fell by 41% since 2009 in a decade, from 997 million tons to 587 million tons. Biomass, which includes wood as well as liquid biofuels like ethanol and biodiesel, remain relatively flat, as wood use declines and biofuel use increases slightly. In contrast, wind and solar are among the fastest-growing energy sources in the projection, ultimately surpassing biomass and nuclear.

Net U.S. imports of energy declined from 30% of total energy consumption in 2005 to 13% in 2013 and down to 7.6 % in 2017, as a result of strong growth in domestic oil and dry natural gas production from tight formations and slow growth of total energy consumption.

US Energy Consumption History

The plot of US energy consumption shows the relative amounts of each type of energy that was consumed for each year.  The history of the energy consumption profile of the United States indicates that petroleum makes the largest part of the energy demand over the past seven decades. Natural gas has taken the second over the past decade with the production of gas from shale. Coal has been replaced by renewable energy and natural gas for electricity generation. Among the renewable energy sources, biomass has the larger share followed by wind energy. Wind energy and solar energy are the fastest growing energy sources.

Growth of Renewables in the U.S.

Credit: US EIA

U.S. energy consumption projections by source and by sector.

Credit: EIA Annual Energy Outlook 2021

Answers to the following questions need to be looked for in the material presented above.

• Of all the renewable energy sources, which renewable source is used most?
• Which of the renewable sources is used most for transportation?
• Approximately what fraction of the electricity is generated by nuclear energy? (10, 20, 50 or 90)

US Vehicle Fuel Consumption

The table below shows the vehicle fuel consumption and travel between 1960 and 2018.

Electricity

US electricity generation is expected to grow from 3.7 trillion kilowatthours in 2015 to 4558 trillion kilowatthours in 2035. Visit the webpage US electricity explained - Sources and profiles

Examine for 

• Sources of U,.S electricity generation
• What are the notable changes in the major sources for  electricity generation between 1950 and 2019?
• Role of renewable energy in the electricity generation.

Growth in electricity use for computers, office equipment, and electrical appliances in the residential and commercial sectors is partially offset by improved efficiency in these and other, more traditional electrical applications, by the effects of demand-side management programs, and by slower growth in electricity demand for some applications, such as air conditioning.

Most capacity additions over the next 10 years are renewables and natural gas, increasing the natural gas share to 26 percent and lowering the coal share to under 20 percent.  The nuclear generation (about 9 percent of total electricity supply in 2012) is projected to remain at about 9 percent in 2050.

Review

Watch the following 4 minute 50 second video Review for Lesson 2.

Some of the fuel (hydrocarbon) may not completely burn during combustion and therefore is released into the atmosphere along with the products. The products that are formed during combustion of fossil fuels are shown in the image below:

Products formed during combustion of fossil fuels

Credit: © Penn State is licensed under CC BY-NC-SA 4.0 

Click to expand to provide more information.

Fossil fuels consisting mainly of carbon, hydrogen, nitrogen, sulfur, and oxygen produce the following products during combustion:

The primary pollutants are Carbon Monoxide (CO), Carbon Dioxide (CO2), Sulfur (SO2), Nitrogen Dioxide (NOx), Nitric Oxide (N2O), Volatile organic compounds (VOCs), and Hydrocarbons (HCs).

The particulate matter produced are Course particles less than 10 microns (PM10), Fine particles less than 2 microns (PM2.5), and Ammonia (NH3).

We will now look at six products of combustion:

1. Carbon Dioxide
2. Carbon Monoxide
3. Sulfur Dioxide
4. Nitrogen Oxides
5. Lead
6. Particulate Matter

Carbon Dioxide (CO₂)

Carbon dioxide is one of the maor products of combustion with fossil fuels since carbon accounts for 60–90 percent of the mass of fuels that we burn.

China has emerged as the largest single emitter of energy-related CO₂ emissions, surpassing the U.S. in  carbon dioxide emissions back in 2010.  Now, China emits more than 10 million metric tons while the U.S. hovers around 5 million metric tons. The chart below shows the trend in carbon dioxide emissions since 1980. For Asia and Oceania, and particularly for China and India, emissions can be seen to have increased significantly in the past two decades.

In 2019, 29 % of CO2 emissions were from transportation, 25 % were from electricity production, 23 % were from industry processes the remaining quarter are from commercial, residential and agricultural applications.

Carbon Monoxide (CO)

If a carbon-based fuel and its products are not completely oxidized (i.e. not burned completely), carbon monoxide will be formed. Carbon monoxide, or CO, is a colorless, odorless gas. The figure below shows the contribution of various sources to the emissions of CO:

Carbon Monoxide is a component of motor vehicle exhaust, which contributes about 55 percent of all CO emissions nationwide. Other non-road engines and vehicles (such as construction equipment and boats) contribute about 22 percent of all CO emissions nationwide. Higher levels of CO generally occur in areas with heavy traffic congestion. In cities, 85 to 95 percent of all CO emissions may come from motor vehicle exhaust.

Other sources of CO emissions include industrial processes (such as metals processing and chemical manufacturing), residential wood burning, as well as natural sources such as forest fires. Woodstoves, gas stoves, cigarette smoke, and unvented gas and kerosene space heaters are sources of CO indoors.

The highest levels of CO in the outside air typically occur during the colder months of the year, when inversion conditions are more frequent. An inversion is an atmospheric condition that occurs when the air pollutants are trapped near the ground beneath a layer of warm air.

Sulfur Dioxide (SO₂)

Sulfur dioxide, or SO₂, belongs to the family of sulfur oxide gases (SO_x). These gases dissolve easily in water. Sulfur is prevalent in all raw materials, including crude oil, coal, and ores that contain common metals, such as aluminum, copper, zinc, lead, and iron.

SO_x gases are formed when fuel containing sulfur, such as coal and oil, is burned, and when gasoline is extracted from oil, or metals are extracted from ore. SO₂ dissolves in water vapor to form acid and interacts with other gases and particles in the air to form sulfates and other products that can be harmful to people and their environment.

Nitrogen Oxides (NO_x)

Nitrogen oxides, or NO_x, is the generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. Many of the nitrogen oxides are colorless and odorless.

Nitrogen oxides form when fuel is burned at high temperatures, as in a combustion process. The primary sources of NO_x are motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels as shown in the figure below.

Although many of the nitrogen oxides are colorless and odorless, one common pollutant, nitrogen dioxide (NO₂) along with particles in the air can often be seen as a reddish-brown layer over many urban areas.

Smog over Los Angeles

Credit: Los Angeles from the Getty Center by Nick Thompson is licensed under CC BY-NC-SA 2.0

Lead (Pb)

The major sources of lead emissions have historically been motor vehicles (such as cars and trucks) and industrial sources.

Due to the phase-out of leaded gasoline, metals processing is the major source of lead emissions to the air today. The highest levels of lead in air are generally found near lead smelters (devices that process lead ores). Other stationary sources are waste incinerators, utilities, and lead-acid battery manufacturers.

Lead is a metal found naturally in the environment as well as in manufactured products.
A man is pictured in a protective suit as he removes lead-based paint from the US Capitol Dome.

Credit: Architect of the Capitol

Lead is used in the manufacturing of many items, including
glass, rubber, paint, batteries, insecticides, plumbing, and
protective shielding for X-rays.

Particulate Matter (PM)

Particulate matter (PM) is the general term used to describe a mixture of solid particles and liquid droplets found in the air. Some particles are large enough to be seen as dust or dirt. Others are so small they can be detected only with an electron microscope.

Different sizes of Particles include:

• PM 2.5 describes the “fine” particles that are less than or equal to 2.5 µm (micro meter) in diameter.
• “Coarse fraction” particles are greater than 2.5 µm, but less than or equal to 10 µm in diameter.
• PM 10 refers to all particles less than or equal to 10 µm in diameter (about one-seventh the diameter of a human hair). PM can be emitted directly or formed in the atmosphere.

Different Sources of Particles include:

• "Primary" particles are formed from combustion sources and are emitted directly into the atmosphere. Examples of primary particles are dust from roads or black carbon (soot).
• "Secondary" particles are formed in the atmosphere from primary gaseous emissions. Examples of secondary particles are sulfates formed from SO₂ emissions from power plants and industrial facilities; nitrates formed from NO_x emissions from power plants, automobiles, and other combustion sources; and carbon formed from organic gas emissions from automobiles and industrial facilities.

The chemical composition of PM depends on location, time of year, and weather. Generally, primary particles make up coarse PM and secondary particles make up most of fine PM.

The pollutants that are emitted directly from a combustion process – or the products of combustion - are called “primary pollutants.” We just described these products earlier in the lesson, now we will look at their impact on the environment and human health.

Carbon Dioxide (CO₂)

Carbon dioxide (CO₂) is not a pollutant in the sense that would directly harm our health, but it is a proven greenhouse gas. It has an ability to absorb infrared radiation that is escaping from the surface of the earth, causing the atmosphere to warm up. Excessive emission of CO₂ along with other greenhouse gases are linked to climate change, which is reaching a critical point.

Carbon Monoxide (CO)

As we learned earlier, Carbon monoxide, or CO, is a colorless, odorless and tasteless gas that is formed when carbon in fuel is not burned completely.

At much higher levels of exposure not commonly found in ambient air, CO can be poisonous, and even healthy individuals can be affected. Exposure to elevated levels of CO may result in:

• visual impairment;
• reduced work capacity;
• reduced manual dexterity;
• poor learning ability;
• difficulty in performing complex tasks.

The health threat from levels of CO sometimes found in the ambient air is most serious for those who suffer from cardiovascular disease such as angina pectoris.

Sulfur Dioxide (SO₂)

High concentrations of SO₂ can result in the following health problems:

Short-term exposure

• Adults and children with asthma who are active outdoors will experience temporary breathing impairment.
• Individuals with asthma may experience breathing difficulties with moderate activity and may exhibit symptoms such as wheezing, chest tightness, or shortness of breath.

Long-term exposure (along with high levels of PM)

• Aggravation of existing cardiovascular disease
• Respiratory illness
• Alterations in the lungs’ defenses

The subgroups of the population that may be affected under these conditions include individuals with heart or lung disease, as well as the elderly and children.

The body's reaction to regular and acidic air

Instructions: Click on the types of air and observe what happens for each. (Note: The animation has no audio.)

Together, SO₂ and NO_x (discussed on the next page) are the major precursors to acidic deposition (acid rain), which is associated with the acidification of soils, lakes, and streams and accelerated corrosion of buildings and monuments. We will talk more about this in the next section. SO₂ also is a major precursor to PM 2.5, which is a significant health concern, and a main contributor to poor visibility.

Nitrogen Oxides (NO_x)

Nitric oxide (NO) and nitrogen dioxide (NO₂) together are represented by NO_x. Most of the emissions from combustion devices (approximately 90%) are in the form of NO.

NO_x react in the air to form ground-level ozone and fine particulates, which are associated with adverse health effects.

• Short-term exposures (e.g., less than 3 hours) to low levels of NO₂ may lead to changes in airway responsiveness and lung function in individuals with preexisting respiratory illnesses. These exposures may also increase respiratory illnesses in children.
• Long-term exposures to NO₂ may lead to increased susceptibility to respiratory infection and may cause irreversible alterations in lung structure.

NO_x contributes to a wide range of environmental effects directly and when combined with other precursors in acid rain and ozone.

• Increased nitrogen inputs to terrestrial and wetland systems can lead to changes in plant species composition and diversity.
• Direct nitrogen inputs to aquatic ecosystems such as those found in estuarine and coastal waters (e.g., Chesapeake Bay) can lead to eutrophication (a condition that promotes excessive algae growth, which can lead to a severe depletion of dissolved oxygen and increased levels of toxins harmful to aquatic life).
• Nitrogen, alone or in acid rain, also can acidify soils and surface waters.

Particulate Matter (PM)

Particles smaller than or equal to 10 µm (micro meter or millionth of a meter) in diameter can get into the lungs and can cause numerous health problems. Inhalation of these tiny particles has been linked with illness and death from heart and lung disease. Various health problems have been associated with long-term (e.g., multi-year) exposures to these particles. Shorter-term daily and potentially even shorter term peak (e.g., 1-hour) exposures to these particles can also be associated with health problems.

Particles can aggravate respiratory conditions, such as asthma and bronchitis, and have been associated with cardiac arrhythmias (heartbeat irregularities) and heart attacks. People with heart or lung disease, the elderly, and children are at highest risk from exposure to particles.

Particles of concern can include both fine and coarse-fraction particles, although fine particles have been more clearly linked to the most serious health effects.

• Particles larger than 2 micro meters (µm) do not penetrate beyond the nasal cavity or trachea.
• Particles smaller than 0.1 µm tend to deposit in tracheobronchia tree and are removed when exhaling.
• Particles between 0.1 and 2.0 µm penetrate deep into the lungs and settle in respiratory bronchioles or alveolar sacs

How particulate matter is breathed into the human body

Instructions: See what happens when the name of each size of particulate matter is clicked on. (Note: The animation has no audio.)

Lead

Exposure to lead occurs mainly through inhalation of air and ingestion of lead in food, water, soil, or dust. It accumulates in the blood, bones, and soft tissues and can adversely affect the kidneys, liver, nervous system, and other organs.

• Excessive exposure to lead may cause neurological impairments such as seizures, mental retardation, and behavioral disorders.
• Even at low doses, lead exposure is associated with damage to the nervous systems of fetuses and young children, resulting in learning deficits and lowered IQ.
• Recent studies indicated that lead may be a factor in high blood pressure and subsequent heart disease.
• Lead can also be deposited on the leaves of plants, presenting a hazard to grazing animals and to humans through ingestion.

Instructions: Click the "play" button to see the impact of using unleaded rather than leaded gasoline. (Note: The animation has no audio.)

The pollutants that are emitted directly from a combustion process are called “primary pollutants.” When emitted into the atmosphere, these primary pollutants combine with other reactants and form “secondary” pollutants.

An example of a secondary pollutant would be ozone. When hydrocarbons are emitted, and they react with NO_x in presence of sunlight, they form ozone. Health and environmental effects of secondary pollutants are discussed in the next section: Global and Regional Effects of Pollutants.

Ozone is a form of oxygen and also a poisonous gas. However, when in the earth's atmosphere, ozone acts as a protective shield against ultraviolet radiation in space.

The Earth is continuously receiving energy from the sun. Energy also leaves the Earth at night (of course in the form of invisible infrared energy!). Otherwise, the Earth would be continuously warming up. This delicate balance between the energy coming in and leaving due to natural greenhouse effect is what keeps the planet warm enough for us to live on.

It is very obvious that if more energy comes in than the energy that leaves, the planet will become warm. Similarly, if the energy that leaves is more than the energy that comes in, the planet will become cool. The atmospheric temperature fluctuates over centuries due to certain natural causes. However, our "recent" (on a geological timescale) use of fuels that have been trapped underground are quickly changing the environment outside of these natural norms.

Go to the next screen to view an animation of the greenhouse effect.

In the first lesson, we saw that energy can be transformed from one form to another, and during this conversion, all the energy that we put into a device comes out. However, all the energy that we put in may not come out in the desired form. Please watch the following presentation:

As can be seen from the Figure below, the amount of CO2 currently in the atmosphere is dramatically higher than previous levels even if we go back 800,000 years!

The onset of this dramatic rise corresponds to the industrial revolution and humanities increased use of CO2 producing fuels.

Our relationships with the greenhouse effect and greenhouse gases are complicated. A little bit is a good thing, and it plays a big role in what keeps us comfortable. However, too many greenhouse gases will heat up our planet and dramatically change climates throughout the world. It's also worth mentioning that CO₂ is not the only greenhouse gas being produced by human activity.

The concentration of greenhouse gases in the atmosphere has been changing over the past 150 years. Since pre-industrial times, atmospheric concentrations of the gases have increased:

• CO₂ has climbed over 31 percent.
• CH₄ has climbed over 151 percent.
• N₂O has climbed 17 percent.

Scientists have confirmed that this is primarily due to human activities, which include burning coal, oil, and gas, and cutting down forests.

Lumberjack climbing a tree

Credit: Timber Feller, Lake of the Woods, Oregon by Michael McCullough is licensed under CC BY-NC-ND 2.0

Check this out!

Hold your mouse over the pie chart to see what percentage each gas accounts for in the total greenhouse emissions in the United States, and look at the table below for information about the sources of the gasses.

Greenhouse Gases

Credit: Distribution of Emissions by Greenhouse Gases © Penn State is licensed under CC BY-NC-SA 4.0 

Click here to see the data in a table

Distribution of emissions by greenhouse gases

Greenhouse Gas	Percent of Total Greenhouse Gases
Carbon Dioxide (C02) - Energy Related	82%
Carbon Dioxide (C02) - Other	2%
Methane (CH4)	9%
Nitrous Oxide (N2O)	5%
Other Gases (CFC-12, HCFC-22, CF4, SF6)	2%

The following list shows the greenhouse gasses and the source of emission:

• Carbon dioxide (CO2): Energy related CO2: 82% and Other CO2: 2%.
  Produced by combustion of solid waste, fossil fuels, and wood and wood products.
• Methane (CH4): 9%.
  Source is the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock.
• Nitrous Oxide (N2O): 5%.
  Produced by agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels.
• Other gases (SO₂, CFC-12, HCFC-22, Perfluoromethane [CF4], and Sulfur Hexaflouride [SF6]): 2%.
  Produced by industrial processes.

As you can see, energy related CO₂ and CH₄ accounts for 90 percent of the total greenhouse gas emissions in the United States. This highlights the impact of energy use on the environment.

Atmospheric lifetime is the period of time during which a gas changes and is either transformed or removed from the atmosphere.

GWP is an index defined as the cumulative radiative forcing (infrared radiation absorption) between the present and some chosen time horizon caused by a unit mass of gas emitted now, expressed relative to a reference gas such as CO₂, as is used here. GWP is an attempt to provide a simple measure of the relative radiative effects of different greenhouse gases. In terms of GWP, methane is a much stronger greenhouse gas (~30x more potent) compared to CO2.

How Has CO₂ Concentration Changed?

As you can see from the graph below, CO2 values have risen dramatically in a very short amount of time. These changes correspond to our increased reliance on fossil fuels which took off in the 1900s.

The image features two line graphs depicting global atmospheric concentrations of carbon dioxide over time. The left graph spans from 804,000 BCE to 2019 CE, showing fluctuations and an eventual steep increase in carbon dioxide levels reaching over 400 ppm. The right graph zooms in on the years 1950 to 2019 CE, illustrating a continuous rise in carbon dioxide concentrations from 300 ppm to over 400 ppm.

Credit:“Global Atmospheric Concentrations of Carbon Dioxide Over Time.” US EPA. June, 2024.

Try This!

Instructions: In the graph below, observe how CO₂ concentration in the atmosphere has changed over the past 50 years. Based on your observations, answer the questions that follow.

Data from the graph above was obtained from ice core samples of trapped air. More specifically, ice in the Polar Regions traps air from that particular time period, and then new ice is deposited over the previously deposited ice, trapping more air from the past. Thus, the analysis of ice core samples provides the composition of past air, which can be used to determine the past temperatures.

The increase in the greenhouse gases between 1950 and 2020 is believed to have caused an increase in the global temperature. The mean increase in the global temperature over the past one century is about 1 degree Celsius. However, this is the global average, which does not distinguish between ocean surface and land surface temperatures.  The ocean surface increased by about 0.77 C whereas land temperatures increased by a staggering 1.43 C compared to pre-1900 temperatures. In other words, land areas are heating up about twice as fast!

Instructions: Review the graph below, showing the Annual mean for the Global surface temperature between years 1960 and 2020. The annual mean will show the detailed fluctuations.

Global annual surface temperature change from the average over the last 100 or so years.

Source: NASA

Since 1880, about when the industrial age first started, the average increase in global temperature has been 1 degree Celsius.Not only has there been an increase in temperatures with the increase of greenhouse gasses, there has also been an increase in CO₂ emissions from fossil fuels – this has been apparent over the last 150 years (since about 1850).

If we overlay the temperature plot with CO₂ emissions, you can see a strong correlation between the rise in temperature and increased CO2 production.

Global temperature and CO₂ concentration changes since the 1900s. 

Credit: “Atmospheric Carbon Dioxide and Earth's Surface Temperature (1880-2020).” NOAA. May 16, 2024.

So what will happen in the next few decades? Well, it is hard to say because it depends on what we do in the future. Do we continue to replace fossil fuels with renewables, or do we hold onto our existing practices a bit longer? Experts have tried to predict what will happen to global temperatures based on what we currently know about our climate. A key variable is how much additional CO₂ we emit over the next few decades.

CO₂ emissions predictions based on different renewable energy adoption trends.

Credit: B. C. O’Neill. "Carbon Dioxide Emissions." Nature. 2016.

These assumptions are used within climate models to predict possible temperature changes into the year 2100.

Temperature predictions based on different renewable energy adoption scenarios.

Credit: B. C. O’Neill. "Carbon Dioxide Emissions." Nature. 2016.

Though a few degrees doesn't seem like much, this is only the average temperature across the whole planet. In practice, many regions on land will have temperature increases far beyond a few degrees. As such, many predict an increase in the frequency and magnitude of heat waves, forest fires and other nature disasters. These factors are pushing societies to weigh the consequences of cheap fuels with their environmental impacts.  

Human activities change the earth's atmosphere.

Scientists know for certain that human activities are changing the composition of Earth's atmosphere. Increasing levels of greenhouse gases in the atmosphere, like carbon dioxide (CO₂), have been well documented since pre-industrial times. There is no doubt this atmospheric buildup of carbon dioxide and other greenhouse gases is largely the result of human activities.

It's well accepted by scientists that greenhouse gases trap heat in the Earth's atmosphere and tend to warm the planet. By increasing the levels of greenhouse gases in the atmosphere, human activities are strengthening Earth's natural greenhouse effect. The key greenhouse gases emitted by human activities remain in the atmosphere for periods ranging from decades to centuries.

A warming trend of about 1^oC has been recorded since the late 19^th century. Warming has occurred in both the northern and southern hemispheres, and over the oceans. Confirmation of twentieth-century global warming is further substantiated by melting glaciers, decreased snow cover in the Northern Hemisphere, and even warming below ground.

Impact of Global Warming on such things as health, water resources, polar regions, coastal zones, and forests is likely, but it is uncertain to what extent.

Health

The most direct effect of climate change would be the impacts of the hotter temperatures, themselves. Extremely hot temperatures increase the number of people who die on a given day for many reasons:

• People with heart problems are vulnerable because one's cardiovascular system must work harder to keep the body cool during hot weather.
• Heat exhaustion and some respiratory problems increase.
• Higher air temperatures also increase the concentration of ozone at ground level.
• Diseases that are spread by mosquitoes and other insects could become more prevalent if warmer temperatures enabled those insects to become established farther north; such "vector-borne" diseases include malaria, dengue fever, yellow fever, and encephalitis.

Water Resources

Changing climate is expected to increase both evaporation and precipitation in most areas of the United States. In those areas where evaporation increases more than precipitation, soil will become drier, lake levels will drop, and rivers will carry less water. Lower river flows and lower lake levels could impair navigation, hydroelectric power generation, and water quality, and reduce the supplies of water available for agricultural, residential, and industrial uses. Some areas may experience increased flooding during winter and spring, as well as lower supplies during summer.

Polar Regions

Climate models indicate that global warming will be felt most acutely at high latitudes, especially in the Arctic, where reductions in sea ice and snow cover are expected to lead to the greatest relative temperature increases. Ice and snow cool the climate by reflecting solar energy back to space, so a reduction in their extent would lead to greater warming in the region.

Coastal Zones

Sea level is rising more rapidly along the U.S. coast than worldwide. Studies by EPA and others have estimated that along the Gulf and Atlantic coasts, a one-foot (30 cm) rise in sea level is likely by 2050.
In the next century, a two-foot rise is most likely, but a four-foot rise is possible. Rising sea level inundates wetlands and other low-lying lands, erodes beaches, intensifies flooding, and increases the salinity of rivers, bays, and groundwater tables. Low-lying countries like the Maldives located in the Indian Ocean and Bangladesh may be severely affected. The world may see global warming refugees from these impacts.

Forests

The projected 2°C (3.6°F) warming could shift the ideal range for many North American forest species by about 300 km (200 mi.) to the north.

• If the climate changes slowly enough, warmer temperatures may enable the trees to colonize north into areas that are currently too cold, at about the same rate as southern areas became too hot and dry for the species to survive. If the Earth warms 2°C (3.6°F) in 100 years, however, the species would have to migrate about 2 miles every year.
• Poor soils may also limit the rate at which tree species can spread north.
• Several other impacts associated with changing climate further complicate the picture:
  • On the positive side, CO₂ has a beneficial fertilization effect on plants, and also enables plants to use water more efficiently. These effects might enable some species to resist the adverse effects of warmer temperatures or drier soils.
  • On the negative side, forest fires are likely to become more frequent and severe if soils become drier.

The long-term effects of global warming

Scientists have identified that our health, agriculture, water resources, forests, wildlife, and coastal areas are vulnerable to the changes that global warming may bring. But projecting what the exact impacts will be over the twenty-first century remains very difficult. This is especially true when one asks how a local region will be affected.

Scientists are more confident about their projections for large-scale areas (e.g., global temperature and precipitation change, average sea level rise) and less confident about the ones for small-scale areas (e.g., local temperature and precipitation changes, altered weather patterns, soil moisture changes). This is largely because the computer models used to forecast global climate change are still ill-equipped to simulate how things may change at smaller scales.

Some of the largest uncertainties are associated with events that pose the greatest risk to human societies. IPCC cautions, "Complex systems, such as the climate system, can respond in non-linear ways and produce surprises." There is the possibility that a warmer world could lead to more frequent and intense storms, including hurricanes. Preliminary evidence suggests that, once hurricanes do form, they will be stronger if the oceans are warmer due to global warming.  Stil, the net result appears to be a more complex environment that is less hospitable compared to what we are accustomed.

IPCC stands for The Intergovernmental Panel on Climate change. Its role is to assess scientific, technical and socio-economic information to determine the risk of human-induced climate change and the options available for adapting to these changes.

Today, there is no single action that will reverse the course of climate change. The main question is whether we want to wait and adapt to a new environment, or whether we want to start to do something now?

There is certainty that human activities are rapidly adding greenhouse gases to the atmosphere, and that these gases warm our planet. This is the basis for concern about global warming.

The fundamental scientific uncertainties are these: How much more warming will occur? How fast will this warming occur? And what are the potential adverse effects? These uncertainties will be with us for some time, but many suspect that point of no return is well past us. If we don't change our habits soon, we will be stuck with a warmer world until we find a way to reduce the concentration of greenhouse gases in our atmosphere.

Global warming poses real risks, and those risks increase as we continue to change the composition of the atmosphere. Ultimately, this is why we have to use our best judgment—guided by the current state of science—to determine what the most appropriate response to global warming should be.

What difference can I make?

When faced with this question, individuals should recognize that, collectively, they can make a difference. In some cases, it only takes a little change in lifestyle and behavior to make some big changes in greenhouse gas reductions. For other types of actions, the changes are more significant.

When that action is multiplied by the 300 million people in the U.S. or the 7 billion people worldwide, the savings are significant. The actions include being energy efficient in the house, in the yard, in the car, and in the store.

Everyone's contribution counts, so why not do your share?

Energy Efficiency Means Doing the Same (or More) with less Energy. When individual action is multiplied by the 300 million people in the U.S., or the 6 billion people worldwide, the savings can be significant.

How Can I Save the Environment?

Instructions: You can help save the environment by making changes from the top to the bottom of your home. Click on the hot spots below to see how you can make a difference:

Review

To review, these are the things you can do in your home – from top to bottom - to protect from the environment:

1. Purchase "Green Power" - electricity that is generated from renewable sources such as solar, wind, geothermal, or biomass - for your home's electricity, if available from your utility company. Although the cost may be slightly higher, you'll know that you are buying power from an environmentally friendly energy source.
2. Insulate your home – you’ll learn more about this in Home Activity Three.
3. Use low-flow faucets in your showers and sinks.
4. Replace toilets with water-saving lavatories.
5. Purchase home products—appliances, new home computers, copiers, fax machines, that display the ENERGY STAR® label - You can reduce your energy consumption by up to 30 percent and lower your utility bills! Remember, the average house is responsible for more air pollution and carbon dioxide emissions than is the average car.
6. When your lights burn out, replace them with energy-efficient compact fluorescent lights.
7. Lower the temperature on your hot water tank to 120 degrees.
8. Tune up your furnace.
9. Insulate your water heater and all water pipes to reduce heat loss.

When you remodel, build, or buy a new home, incorporate all of these energy efficiency measures—and others.

Each of us, in the U.S., contributes about 22 tons of carbon dioxide emissions per year, whereas the world average per capita is about 6 tons.

The good news is that there are many ways you and your family can help reduce carbon dioxide pollution and improve the environment for you and your children.

Acid rain is a serious environmental problem around the world, particularly affecting Asia, Europe, and large parts of the U.S. and Canada. The acidic pollutants such as SO₂ and NO_x are emitted into the environment by combustion of fossil fuels.

Most of the sulfur in any fuel combines with oxygen and forms SO₂ in the combustion chamber. This SO₂ when emitted into the atmosphere slowly oxidizes to SO₃. SO₃ is readily soluble in water in the clouds and forms H₂SO₄ (sulfuric acid).

$$S+O_2\to S{O}_2+\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.O_2(\text{in the atmosphere})\to S{O}_3+H_{2}O\to H_{2}S{O}_4(\text{sulfuric acid})$$
Most of the NO_x that is emitted is in the form of NO. This NO is oxidized in the atmosphere to NO₂. NO₂ is soluble in water and forms HNO₃ (nitric acid).

$$NO+\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.O_2(\text{in the atmosphere})\to N{O}_2+H_{2}O\to HN{O}_3(\text{nitric acid})$$

Sunlight increases the rate of most of the SO₂ and NO reactions. The result is a mild solution of sulfuric acid and nitric acid. "Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry.

• Wet deposition - refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depend on many factors, including:
  • the acidity of the water;
  • the chemistry and buffering capacity of the soils involved;
  • the types of fish, trees, and other living things that rely on the water.

• Dry deposition - refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition.
  • Acidic particles and gases are blown by the wind onto buildings, cars, homes, and trees.
  • Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone.

Process of Acid Deposition

Prevailing winds blow the compounds that cause both wet and dry acid deposition across state and national borders, and sometimes over hundreds of miles. Please watch the 1:22 presentation below to learn more about the process of acid deposition.

An estimated one million residential and 200,000 commercial solar water-heating systems have been installed in the United States. Although there are a large number of different types of solar water-heating systems, the basic technology is very simple.

Sunlight strikes and heats an "absorber" surface within a "solar collector" or an actual storage tank. These roof-mounted solar heaters supply about 80% of the hot water for the home. Either a heat-transfer fluid or the actual potable water to be used flows through tubes attached to the absorber and picks up the heat from it. (Systems with a separate heat-transfer-fluid loop include a heat exchanger that then heats the potable water.) The heated water is stored in a separate preheat tank or a conventional water heater tank until needed.

If additional heat is needed, it is provided by electricity or fossil-fuel energy by the conventional water-heating system.

A roof mounted solar water heater.

Credit: Thermodynamic Panels Installed by KVDP from Wikimedia (Public Domain) 

How a Solar Water Heater Works

Click the “play” button to see how a solar water heater operates.

By reducing the amount of heat that must be provided by conventional water heating, solar water-heating systems directly substitute renewable energy for conventional energy, reducing the use of electricity or fossil fuels by as much as 80%.

Today's solar water-heating systems are proven reliable when correctly matched to climate and load. The current market consists of a relatively small number of manufacturers and installers that provide reliable equipment and quality system design.

A quality assurance and performance-rating program for solar water-heating systems, instituted by a voluntary association of the solar industry and various consumer groups, makes it easier to select reliable equipment with confidence.

Building owners should investigate installing solar hot water-heating systems to reduce energy use. However, before sizing a solar system, water-use reduction strategies should be put into practice.

Types of Solar Hot Water Heaters

There are five types of solar hot water systems:

• Thermosiphon Systems. These systems heat water or an antifreeze fluid, such as glycol. The fluid rises by natural convection from collectors to the storage tank, which is placed at a higher level. No pumps are required. In thermosiphon systems, fluid movement, and therefore heat transfer, increases with temperature, so these systems are most efficient in areas with high levels of solar radiation.
• Direct-Circulation Systems. These systems pump water from storage to collectors during sunny hours. Freeze protection is obtained by recirculating hot water from the storage tank, or by flushing the collectors (drain-down). Since the recirculation system increases energy use, while flushing reduces the hours of operation, direct-circulation systems are used only in areas where freezing temperatures are infrequent.
• Drain-Down Systems. These systems are generally indirect water-heating systems. Treated or untreated water is circulated through a closed loop, and heat is transferred to potable water through a heat exchanger. When no solar heat is available, the collector fluid is drained by gravity to avoid freezing and convection loops, in which cool collector water reduces the temperature of the stored water.
• Indirect Water-Heating Systems. In these systems, freeze-protected fluid is circulated through a closed loop and its heat is transferred to potable water through a heat exchanger with 80 to 90 percent efficiency. The most commonly used fluids for freeze protection are water-ethylene glycol solutions and water-propylene glycol solutions.
• Air Systems. In this indirect system, the collectors heat the air, which is moved by a fan through an air-to-water heat exchanger. The water is then used for domestic or service needs. The efficiency of the heat exchanger is in the 50% range.

Direct-circulation, thermosiphon, or pump-activated systems require higher maintenance in freezing climates. For most of the United States, indirect air and water systems are the most appropriate. Air solar systems, while not as efficient as water systems, should be considered if maintenance is a primary concern since they do not leak or burst.

Heat pumps are a well-established technology for space heating. The same principle of transferring heat is at work in heat pump water heaters (HPWHs) except that they extract heat from air (indoor, exhaust, or outdoor air) and deliver it to water. Some models come as a complete package, including tank and back-up resistance heating elements, while others work as an adjunct to a conventional water heater.

The simplest HPWH is the ambient air-source unit, which removes heat from surrounding air, providing the additional benefit of space cooling. Exhaust air units extract heat from a continuously exhausted air stream and work better in heating-dominated climates because they do not cool ambient air. Some units can even be converted between the two modes of operation for optimum operation in either summer or winter.

In mild climates, you can place ambient air-source units in unheated but protected spaces such as garages, essentially using outdoor air as a heat source.

Because it extracts heat from air, the HPWH delivers about twice the heat for the same electricity cost as a conventional electric resistance water heater.

 

Parts of a Heat Pump Water Heater (HPWH)

Heat Pump Water Heater Parts

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Desuperheaters

The Desuperheater feature is available on some central air conditioners and is a variation of the stand-alone HPWH. It provides economical supplemental water heating as a byproduct of air conditioning.

Desuperheater water heating can be part of an integrated package with a heat pump or air conditioner system. In most such systems, the heat pump water heating only occurs during normal demand for space conditioning, with resistance electric coils providing water heating the rest of the time.

During the cooling season, the Desuperheater actually improves the efficiency of the air conditioning system while heating water at no direct cost. In an average climate, a desuperheater might meet 20 to 40 percent of annual water heating demand.

Heat pump water heaters can provide up to 60 percent energy savings over conventional water heaters.

How a Heat Pump Water Heater Works

The Heat Pump Water Heater (HPWH) consists of three circuits. The HPWH consists of three circuits. Watch the video below to learn more about how a HPWH works. (30 seconds)

Note: The concept shown in the animation is applicable to all HPWH: heat is picked up and delivered into some source – which could either be the ground, air, or water.

Most of the heat delivered to the water comes from the evaporator of the unit, not through the electrical input to the machine. Consequently, the efficiency of the HPWH is much higher than for direct-fired gas or electric storage water heaters.

The installed cost of commercial HPWH systems is typically several times that of gas or electric water heaters; yet the low operating costs can often offset the higher total installed cost, making the HPWH the economic choice for water heating.

The HPWH becomes increasingly attractive in building applications where energy costs are high, and where there is a steady demand for hot water. This attractiveness is less a function of building type than it is of water demand and utility cost.

The federal efficiency standards for water heaters took effect in 1990, assuring consumers that all new water heaters meet certain minimum-efficiency levels. New standards, which took effect in January 2004, will increase the minimum efficiency levels of these products.

Water heater efficiency is reported in terms of the energy factor (EF). EF is an efficiency ratio of the energy supplied in heated water divided by the energy input to the water heater, and it is based on recovery efficiency, standby losses, and cycling losses. The higher the EF, the more efficient the water heater.

• Electric resistance water heaters have EFs ranging from 0.7 and 0.95.
• Gas water heaters from 0.5 and 0.6, with some high-efficiency models ranging around 0.8.
• Oil water heaters from 0.7 and 0.85.
• Heat-pump water heaters from 1.5 to 2.0.

There is little difference between the most efficient electric resistance storage water heaters and the minimum-efficiency standard that will take effect in January 2004. If you need to rely on electricity to heat your water, keep your eye out for the further development of heat-pump water heaters. This technology uses one-third to one-half as much electricity as a conventional electric resistance water heater.

Energy Efficiency Recommendations

Everything else being equal, select a water heater with the highest energy factor (EF). Below is a table with energy efficiency recommendations.

The higher the EF, the more efficient the water heater.

Other Considerations

In addition to EF, also look for a water heater with at least one-and-a-half inches of tank insulation and a heat trap.

In addition, capacity of a water heater is an important consideration. The water heater should provide enough hot water at the busiest time of the day. For example, a household of two adults may never use more than 30 gallons of hot water in an hour, but a family of six may use as much as 70 gallons in an hour.

The ability of a water heater to meet peak demands for hot water is indicated by its "first hour rating." This rating accounts for the effects of tank size and the speed by which cold water is heated. Water heaters must be sized properly. Over-sized water heaters not only cost more but increase energy use due to excessive cycling and higher standby losses.

Let’s use the Energy Guide to perform a life-cycle analysis to help choose a water heater. Different models of water heaters with the same capacity can vary dramatically in the amount of electricity they use.

Instructions: Use the two EnergyGuide Labels for the different water heaters, to answer questions 1-8.

Sold for $380.00

Sold for $335.00

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Click here to open a text description comparing the two Energy Guide Labels.

Compare the Two EnergyGuide Labels

Water Heater #1:

• Water heater: Electric
• Capacity (first hour rating): 58 gallons
• This model uses 4622 kwh/year
• Energy use range of all similar models (kwh/year): 4624 (uses least energy) - 5109 (uses most energy)
• This model's estimated yearly operating cost is $388
• Based on a 1994 U.S. Government national average cost of $0.0841 per kWh for electricity. Your actual operating cost will vary depending on your local utility rates and your use of the product.
• Sold for $380

Water Heater #2:

• Water heater: Electric
• Capacity (first hour rating): 58 gallons
• This model uses 4989kwh/year
• Energy use range of all similar models (kwh/year): 4624 (uses least energy) - 5109 (uses most energy)
• This model's estimated yearly operating cost is $419
• Based on a 1994 U.S. Government national average cost of $0.0841 per kWh for electricity. Your actual operating cost will vary depending on your local utility rates and your use of the product.
• Sold for $335

Compare the Two Models

Determine Savings

Determine the Pay Back Period

Still trying to figure out the payback period? The price difference between the two models was $45, and your annual monetary savings was $33.76. So after one year, you got back $33.76 out of the $45 extra you spent on the superior model. How much longer would it take you to get back the remaining $11.24? Since $11.24 is about a third of $33.76, it would take you about a third of a year. Thus, your payback period is 1.33 years.

Obviously, it pays to buy an energy-efficient water heater by saving $393.96. It also helps the environment by not using 4,771 kWh of electrical energy and thereby not emitting 9,652 lb of CO₂, 21 lb of NO_x, 75 lb of SO₂ and 1 lb of CO and particulate matter each and into the environment. See the individual’s power!

• Do as much cleaning as possible with cold water to save the energy used to heat water.
• Check your faucets for leaks. They waste both water and energy!
• Conserve hot water by installing water-saving showerheads. A new showerhead can save as much as $10 a year in water and energy.
• Once your water is hot, insulate to help keep it that way. Wrapping exposed hot water pipes with insulation will minimize heat loss. So will installing an R-12 insulation blanket around your water heater, unless the manufacturer does not recommend it.
• Reduce your water heater's temperature to 120 degrees Fahrenheit. That will produce plenty of hot water and still save energy. For homes with a dishwasher, a setting of 140 degrees is required to clean properly, but most of the new dishwashers have a built-in water temperature booster.
• Many new water heaters have a "vacation" setting you can use to save energy if you're away for more than a few days. Turn the thermostat "down" or "off" when you're gone for more than three days.

Most of the energy used by a refrigerator is used to pump heat out of the cabinet. A small amount is used to keep the cabinet from sweating, to defrost the refrigerator, and to illuminate the interior.

The efficiency of a refrigerator is based on the energy consumed per year for a given size. The efficiency of a refrigerator is expressed in volume cooled per unit electric energy per day. Volume is measured in cubic feet and electrical energy is measured in kilowatt-hours.

The energy efficiency of refrigerators and freezers has improved dramatically over the past three decades. For example, the energy bill for a typical new refrigerator with automatic defrost and top-mounted freezer will be about 55 dollars / year, whereas a typical model sold in 1973 will cost nearly 160 dollars / year (almost three times the energy consumption).

The Department of Energy (DOE) standards set maximum allowable annual energy consumption for different sizes and classes of refrigerators. These Federal efficiency standards first took effect in 1993, requiring new refrigerators and freezers to be more efficient than ever before. A new set of stricter standards took effect July 1, 2001.

Energy Guide Labels

Refrigerators now come with an EnergyGuide label that tells you in kilowatt-hours (kWh) how much electricity a particular model uses in a year. The smaller the number, the less energy the refrigerator uses and the less it will cost you to operate.

• Full-sized refrigerators that exceed the federal standard by 15% or more (and full-sized freezers that exceed it by 10%) qualify for the ENERGY STAR label.
• Compact refrigerators and freezers must exceed the standard by 20% to qualify for ENERGY STAR.

Energy Guide Label.

Credit: Energy Guide Label by Federal Trade Commission

ENERGY STAR qualified refrigerators provide energy savings without sacrificing the features you want. ENERGY STAR–qualified models have

• High-efficiency compressors
• Improved insulation
• More precise temperature
• More precise defrost mechanisms

These models also use at least 15% less energy than required by current federal standards, and 40% less energy than the conventional models sold in 2001.

Many ENERGY STAR qualified models include automatic ice-maker and through-the-door ice dispensers. Qualified models are also available with top, bottom, and side-by-side freezers.

What to look for in a Refrigerator

When selecting a refrigerator, remember the following:

• Refrigerators with the freezer on either the bottom or top are the most efficient. Bottom freezer models use approximately 16 percent less energy than side-by-side models, and top freezer models use about 13 percent less than side-by-side.
• Through-the-door ice makers and water dispensers are convenient and reduce the need to open the door, which helps maintain a more constant temperature; however, these convenient items will increase your refrigerator's energy use by 14 to 20 percent.
• Mini-doors give you easy access to items most often used. The main door is opened less often, which saves energy.
• Too large a refrigerator may waste space and energy. One that's too small can mean extra trips to the grocery store. Your best bet is to decide which size fits your needs, and then compare the EnergyGuide label on each, so you can purchase the most energy efficient make and model. (filling your refrigerator helps with efficiency, so long as it's not overfilled!)
• A manual defrost refrigerator uses half the energy of an automatic defrost model, but must be defrosted regularly to stay energy efficient.
• Refrigerators with anti-sweat heaters consume 5 percent to 10 percent more energy. Look for models with an "energy saver" switch that lets you turn down—or off—the heating coils (which prevent condensation).

Technology Improvements

The improvement in the energy efficiency over the past three decades is due to the:

• addition of vacuum insulation panels around the freezer section to reduce heat transfer;
• addition of polyurethane foam to the doors to double insulation thickness;
• replacement of AC motors with more efficient DC motors;
• replacement of automatic defrost control with an adaptive defrost that operates only when needed.

Refrigerators: Your “Power” in the Environmental Protection

• Keep your refrigerator or freezer at the following temperatures: 37–40°F for the fresh food compartment of the refrigerator, 0–5°F for the freezer section. Use a thermometer to check inside temperatures.
• Regularly defrost manual-defrost refrigerators and freezers; don't allow frost to build up more than 1/4 inch.
• Make sure your refrigerator and freezer door seals are airtight. Check the seal on door gaskets periodically by closing the door on a dollar bill. If it pulls out easily, you may need a new gasket.
• Keep the doors closed as much as possible and make sure they are closed tightly.
• To ensure proper cooling of its contents, don't crowd food items. Too many dishes obstruct air circulation.
• Cover liquids and wrap foods stored in the refrigerator. Uncovered foods release moisture and make the compressor work harder.
• Replace paper wrappings on food items with aluminum foil or plastic wrap. Paper is an insulator.
• Consider turning off the butter conditioner, since it is a little heater inside your refrigerator.
• Experiment with the "energy saver" switch in your refrigerator—it allows you to adjust the heating coil under the "skin" of the refrigerator (the purpose of the heating coils is to prevent condensation on your refrigerator).
• Placement of the refrigerator is very important. Direct sunlight and close contact with hot appliances will make the compressor work harder. More importantly, heat from the compressor and condensing coil must be able to escape freely, or it will cause the same problem. Don't suffocate the refrigerator by enclosing it tightly in cabinets or against the wall. The proper breathing space will vary depending on the location of the coils and compressor on each model—something important to know before the cabinets are redesigned.
• Regularly brush off or vacuum the refrigerator coils on the back or bottom of the unit.
• Because most refrigerators reject heat from the bottom and/or back, they need adequate clearance to allow sufficient airflow. While no specific studies have been done to calculate the optimum clearance space, one general rule-of-thumb is to double the space recommended by manufacturers for refrigerator installation. Another rule-of-thumb is to allow 2 inches of air flow around the refrigerator.
• Don't keep that old, inefficient fridge running day and night in the garage for those few occasions when you need extra refreshments. A 15-year-old refrigerator could cost \$100–\$150 per year.

Stricter new federal standards for clothes washers took effect in two stages. The first stage was in force as of January 2004. Then in 2007, the second stage further strengthened the standard. Three factors are used in determining the federal standards:

• Energy Factor is a metric that was previously used to compare relative efficiencies of clothes washers. The higher the Energy Factor is, the more efficient the clothes washer is. For clothes washers, Energy Factor is calculated using the following formula:
   
  $$\text{Energy Factor }=392\times \text{ Volume }\left({\text{ft}}^{\text{3}}\right)/\text{ Annual Energy Use }\left(\text{KWh}\right)$$

• Water Factor is the number of gallons per cycle per cubic foot that the clothes washer uses. The lower the water factor, the more efficient the washer is. So, if a clothes washer uses 30 gallons per cycle and has a tub volume of 3.0 cubic feet, then the water factor is 10.0. Note: the energy factor for washers does not indicate the real energy efficiency because of the tub size and other factors. Therefore, the Energy Factor is modified to include the tub size and drying characteristics.
• Modified Energy Factor (MEF) is a new equation that replaced Energy Factor as a way to compare the relative efficiency of different units' clothes washers. MEF takes into account the amount of dryer energy used to remove the remaining moisture content in washed items.
   
  $${\text{MEF = ft}}^{\text{3}}\text{ /KWh/Cycle}$$

For more information about MEF circulation, please see the August 27, 1997 Federal Register entry regarding 10 CFR Part 430.

 

Clothes Washers: Your “Power” in the Environmental Protection

• Wash full loads—Clothes washers are most efficient when operated with full loads.
• Wash clothes in cold water – It will conserve energy and is also recommended for colored and many delicate fabrics.

In addition:

• Consider Front loaders – Since they use less water, they use less energy. The most efficient front loaders use less than half the amount of water used in the average top loaders.
• Purchase washing machines with the Energy Star designation – They are 50 percent more energy efficient than the current minimal allowable standard.

Many new energy-efficient, water-conserving clothes washers have been introduced over the past few years. These resource-efficient washers are available in a variety of sizes and configurations, offering consumers a wide range of front-loading and top-loading styles in many different price ranges.

Energy Factor (EF) is the dishwasher energy performance metric. EF is expressed in cycles per kWh and is the reciprocal of the sum of the machine electrical energy per cycle, M, plus the water heating energy consumption per cycle, W.

This equation may vary based on dishwasher features such as water-heating boosters or truncated cycles. The greater the EF, the more efficient the dishwasher is.

The EF is the energy performance metric of both the federal standard and the ENERGY STAR qualified dishwasher program. The federal EnergyGuide label on dishwashers shows the annual energy consumption and cost. These figures use the energy factor, average cycles per year, and the average cost of energy to make the energy and cost estimates. The EF may not appear on the EnergyGuide label.

Test Criteria for ENERGY STAR Qualified Dishwashers

Dishwasher manufacturers must self-test their equipment according to the new Department of Energy (DOE) test procedure defined in 10 CFR 430, Subpart B, Appendix C. This DOE test procedure was announced on August 29, 2003, and all models had to be tested using the new procedure by February 25, 2004.

This test procedure establishes a separate test for soil-sensing machines. Included in the final rule was a decision to add standby energy consumption to the annual energy and cost calculation, but not to the energy factor calculation. Also, the average cycles per year has been lowered from 264 cycles per year to 215 cycles per year. Energy Star dishwashers are at least 25 percent more energy efficient than minimum federal government standards.

The table below lists the standard and the ENERGY STAR approved dishwasher energy factors.

The current ENERGY STAR criteria for dishwashers became effective January 1, 2001. This criteria of at least 25 percent above the federal standard and applies only to models manufactured after January 1, 2001. The previous ENERGY STAR criterion was 13 percent above the federal standard.

Dishwashers: Your “Power” in the Environmental Protection

Buying the correct size appliance for your needs is critical to saving money, energy, and water. In dishwashers, there are compact and standard-capacity units. Compact models use less energy and water per load, but you may actually consume more energy operating them more frequently. The following tips help you to save even more:

• Avoid rinsing dishes before you load them in the dishwasher or, if you must rinse, use cold water.
• Run your dishwasher with a full load. Most of the energy used by a dishwasher goes to heat water. Since you can't decrease the amount of water used per cycle, fill your dishwasher to get the most from the energy used to run it.
• Avoid using the heat-dry, rinse-hold, and pre-rinse features. Instead, use your dishwasher's air-dry option. If your dishwasher does not have an air-dry option, prop the door open after the final rinse to dry the dishes.