Best of Best: assignment 2
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overview_2.docxOverview
Energy Sources and Measurement
Everyone who studies energy should be familiar with the first and second laws of thermodynamics, which explain the existence and movement of energy.
There are many types of energy: primary and secondary energy sources, renewable and non-renewable energy sources, and sustainable energy sources. It is important to understand the distinction between these, as well as the world’s growing appetite for energy consumption.
Learning Objectives
Upon completion of this module, you should be able to:
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2A |
state and apply the laws of thermodynamics. |
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2B |
calculate BTUs per hour. |
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2C |
discuss the differences between primary and secondary energy sources. |
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2D |
recall techniques used to protect the environment. |
Module 2 Reading Assignment
Krigger, J., & Dorsi, C. (2012). Residential Energy: Cost Savings and Comfort for Existing Buildings (6th ed.). Helena: Saturn Resource Management, Inc. Chapter 1.
Supplemental Reading Assignments (Required):
Department of Energy. (2012, May). Energy in brief: What are the major sources and users of energy in the United States? Washington, DC: U.S. Energy Information Administration (pp. 1-5).
DOE. (Ed.) (2010). Energy Scenario . Available from Department of Energy (pp 1-37).
Environmental Protection Agency (2011, March). Energy star performance ratings; Methodology for incorporating source energy use . Washington, DC: Environmental Protection Agency, (pp. 1-17).
U.S. Energy Information Administration (2012, March). Energy brief: how to compare or add up our energy consumption? Washington, DC: Department of Energy (pp. 1-3).
Lecture Notes
Energy
It is important to understand the different types of energy sources. Sources of energy can be primary, secondary, renewable, and non-renewable.
Primary Energy Sources
Primary energy sources exist in nature and can be used directly or may be converted and redirected into a form of energy that satisfies a need. When primary energy sources go through the energy conversion process, they are converted into more convenient forms of energy, such as electrical energy, hydrogen, and cleaner fuels. Primary sources of energy include both renewable and non-renewable sources, such as coal, oil, natural gas, nuclear power, hydropower, biomass, geothermal power, solar power, and wind power.
Secondary Energy Sources
Secondary energy sources can be obtained from the conversion of other, less convenient and beneficial sources of energy. Secondary energy sources include those that are made available for use in a home.
Secondary energy sources:
· Electricity
· Heating oil and gasoline
· Hydrogen
These energy sources are used to power, heat, and cool a house, as well as to cook. Liquid fuels, such as gasoline, methanol, and other hybrids that are used for transportation are also considered secondary energy sources.
Electricity
People are fortunate to enjoy the benefits of electricity. Electricity can be generated from coal, natural gas, solar, geothermal, biomass, landfill gas, wind, hydropower, municipal solid waste, nuclear power, and oil.
About 39 percent of the total energy consumed in America is used to generate electricity. Therefore, electricity consumption is an important part of a consumer’s environmental footprint.
All forms of electricity generation have some level of environmental impact. Most of the electricity in the United States is generated from fossil fuels (i.e., coal, natural gas, and oil).
Fuel Mix for U.S. Electricity Generation, 2005
Heating Oil and Gasoline
Heating oil, which is converted from crude oil in a distillation process, is used primarily in the domestic environment. Gasoline, of course, is another product refined from crude oil and is the primary fuel used in the internal combustion engine in cars. It has been proven that gasoline causes much harm to the environment, including releasing unburned hydrocarbons, nitrogen oxide, and carbon monoxide. Hydrocarbons are the main source of ground-level ozone that causes respiratory problems and other health issues. Nitrogen oxide is the main source of smog. Carbon monoxide is a poisonous gas.
Hydrogen
Hydrogen is the simplest element and the lightest gas in the atmosphere. Because of this, hydrogen as a gas is not found by itself in the Earth’s atmosphere. It is always in combination with other elements, such as water (H2O). The electrolysis of water is the process of splitting hydrogen from oxygen. Countless products, including food products, cleaning agents, and vitamins, are produced using hydrogen.
Renewable and Non-renewable Energy Sources
Energy sources may be renewable, non-renewable, or sustainable. Renewable energy sources can be replenished with little or no human intervention. Solar power is a good example of renewable energy. Regardless of the amount of solar energy used, the energy from the sun cannot be depleted.
Over 85% of the world’s energy is produced using non-renewable energy sources. Oil and coal are good examples of non-renewable energy sources. Non-renewable energy sources are those that do not replenish themselves within a time frame that is relevant to the human life span. Eventually these energy sources will replenish themselves, but not for hundreds, thousands, or perhaps millions of years. Based on the Hubbert peak theory, the world has nearly reached peak oil status. Peak oil is the point in time when the maximum rate of worldwide petroleum extraction is reached and the rate of petroleum extraction enters terminal decline.
World Oil Production to Date (The vertical line indicates the probable midpoint of depletion) Source: The Hubbert Peak for World Oil (December 2003)
Sustainable Energy Sources
Sustainable energy is energy that is renewable and is used efficiently in an environmentally friendly way.
Using sustainable energy sources keeps Earth’s ecosystems functioning continuously without adversely affecting the environment or future generations. Part of sustainability is using renewable forms of energy, such as solar, firewood, water, and wind power.
Renewable Resources and Sustainability
The term renewable does not necessarily imply effective environmentalism. Firewood, which is a renewable energy source, expels pollutants into the air in the forms of particulates and unburned hydrocarbons. In addition, chopping down trees without considering the effect it will have on the environment is not an example of environmental consciousness.
This is why sustainability is important. The Environmental Protection Agency says this about sustainability:
“Sustainable development marries two important insights: environmental protection does not preclude economic development; and economic development must be ecologically viable now and in the long run.
Common use of the term “sustainability,” in the context of modern environmentalism, began with the publication of the World Commission on Environment and Development report, Our Common Future, in 1987. This report characterized sustainable development as ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs.'”
The FDIC states this about sustainability:
“This concept of sustainability encompasses ideas, aspirations, and values that continue to inspire public and private organizations to become better stewards of the environment and that promote positive economic growth and social objectives. The principles of sustainability can stimulate technological innovation, advance competitiveness, and improve our quality of life.”
People and Sustainability
Individuals and organizations, both public and private, pursue development with an eye toward sustainability and the future. They consider the environmental impact of their actions, as well as whether the materials used for a project are renewable and if they can be used without taking away from future generations in terms of supply or environmental degradation.
Measuring Energy
There are various laws and formulas that are essential to the measurement of energy and its usage.
First Law of Thermodynamics
The first law of thermodynamics states that energy is neither created nor destroyed. This is also known as the law of the conservation of energy. This law states that the overall total energy remains the same any time energy is converted from one form to another. Therefore energy only moves from one place to another or changes form.
For example, the chemical reaction for the combustion of natural gas is:
CH4 + O2 → CO2 + H2O + CO + O2
In nature, when this process occurs, the number of carbon, hydrogen, and oxygen atoms on the left side of the equation equals the atoms of these elements on the right side of the equation. Besides just the chemical reaction above, heat is another part of the overall process.
Second Law of Thermodynamics
The second law of thermodynamics states that heat always moves from areas of high temperature to areas of lower temperature. There must be a temperature difference (referred to as Delta T or ΔT) for heat transmission to occur. Simply stated, heat moves from hot to cold.
Example: During a typical summer, heat will move from the outside to the inside of buildings. This process is reversed during winter. Knowing the way heat moves through walls and ceilings helps people diagnosing heat loss and gain problems in homes.
British Thermal Unit
A British thermal unit (BTU, Btu) is a measurement of heat or energy. A BTU is the amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit at 1 atmosphere of pressure. A wooden kitchen match releases approximately one BTU when ignited. Another term associated with BTU is BTUH, which is a measurement of power. BTUH stands for BTU per hour.
This term is often used as a measurement for sizing the capacity of a piece of heating or cooling equipment, the number of BTUs delivered by the equipment in one hour, and the amount of heating or cooling required for a house as determined when load calculations are performed.
For example, a three-ton air conditioner, as a rule of thumb, will have 12,000 BTUH per ton or 36,000 BTUH of cooling power or capacity.
Heat transmission is also measured in BTUH and defined by the following equation:
q = U x A x ΔT U = U-factor of a component of assembly A = Area (in square feet) ΔT = Temperature difference across the component or assembly
Example: What will be the BTUH of a ceiling with U-factor of 0.033 (the equivalent of an R-value of 30), an area of 1,200 square feet, and a ΔT of 58ºF?
q = .033 x 1,200 x 58 q = 39.6 x 58 q = 2296.8 BTUs in one hour
Sensible and Latent Heat
When looking at the heating and cooling needs of a building, both the sensible and latent needs must be taken into account. Sensible heat is merely the heat absorbed or released when a substance of a component undergoes a change in temperature. As above, add 20 BTUs to one pound of water with a temperature of 72ºF and the end result is water with a temperature of 92ºF.
Latent heat, on the other hand, has to do with a change of phase and, in building science and HVAC, this is typically the removal of moisture from the air in a house. This phase change for water requires 970 BTU to change water vapor in the air to liquid as part of the air conditioning cycle. This process is called dehumidification.
Air conditioning units in the dry southwestern United States deserts can be sized properly at perhaps 1,000-1,200 square feet per ton compared to 700-850 square feet per ton in the more humid Midwestern United States plains. Keep in mind that sizing an air conditioner can only be done correctly by performing load calculations.
The current standard for determining heating and cooling loads on a structure is Manual J Version 8, which is published by the Air Conditioning Contractors of America (ACCA). Load calculations are normally performed with a software program. Building components are installed into the software, which then determines the heating and cooling needs of the building.
Conduction, Convection, and Radiation
How is energy or heat transported from one place to another? There must be a temperature difference for heat transfer to occur. There are three primary means of heat transmission.
Conduction is the transfer of heat through a solid or the flow of heat from one object or component to another with which it is in direct physical contact.
Convection is heat movement that is always associated with a fluid such as air or water. This occurs as a result of density changes within the fluid due to the introduction of heat. It should be noted that air and water behave alike. For example, both will always take the path of least resistance.
An example of this is the stack effect, in which heated air rises to the top of a building and is replaced by cooler air at the bottom of the structure.
Radiation is the transfer of heat from a warmer object to a cooler one through space. The most obvious and best example is the sun’s energy warming the earth. Radiant energy can be absorbed, transmitted, or reflected. The key to radiation is that a direct line of sight is required for heat transfer to occur.
If a person stands beside a window in winter, heat will radiate from the person to the window and the result is that the person will feel cold. The introduction of the heat can cause convective loops. Convective loops occur when air is heated on the warm side of the wall cavity, rises, is cooled on the cold side of the cavity, and falls.
Energy Units
There are numerous terms used to define and measure energy. Electrical energy is often measured in kilowatt-hours (kWh). A kilowatt-hour is a unit or measure of electricity supply or the consumption of 1,000 Watts over the period of one hour. One kilowatt hour is equal to about 3,412 BTUs or, in reverse, one BTU is equal to 0.000293 kWh.
There are several terms used in conjunction with natural gas. A hundred cubic feet (written as 1 ccf or 100 cf) or a thousand cubic feet (1 mcf or 1,000 cf) are often used. 1 ccf is approximately equal to 1 therm, which in turn equals 100,000 BTUs. An mcf is approximately equal to 1 million BTUs (written as MMBTU).
Environmental Impact
One of the most common ways to measure the environmental impact of a building, vehicle, or appliance is to measure the amount of carbon dioxide that item puts into the air annually.
Example: In 2005, the national average carbon dioxide output rate for electricity was 1,329 lbs CO2 per megawatt-hour (EPA). That translates to 7.21 metric tons of carbon dioxide emitted per home in one year.
Example: In the same year, the average amount a passenger vehicle emitted was 5.46 metric tons of carbon dioxide equivalents.
Buildings that are made of sustainable resources and operate using energy efficient technologies can be made to emit little or no carbon dioxide when in use. This not only lessens environmental impact, it saves money on energy costs over the long term.
Importance of Conservation
Conservation is important because the majority of sources of energy that people use today are not renewable or sustainable. In addition, these sources of energy often contribute large amounts of pollution to the environment.
It is our responsibility to conserve so that future generations will have the opportunity to enjoy the Earth’s diverse plant and wildlife and to access their share of the resources that the planet provides.
The U.S. Environmental Protection Agency (EPA) encourages people to conserve by advocating a Pick 5 for the Environment program. People are asked to pick 5 items from the EPA’s list of 10 items to protect the environment. Here is their list of ways to conserve:
1. Use less water – Take showers instead of baths, fix leaks, and turn off the tap when brushing your teeth. Buy efficient fixtures by looking for the WaterSense label.
2. Commute without polluting – Use public transportation, carpool, walk, or bike whenever possible to reduce air pollution and save on fuel costs.
3. Save electricity – Do a home energy audit, get programmable thermostats, buy Energy Star products, turn electronic items off when you are done using them, and change light bulbs to compact fluorescent bulbs.
4. Reduce, reuse, recycle – Try to find products with less packaging, take reusable bags on shopping trips, creatively reuse other products, and recycle whatever is left.
5. Test your home for radon – Radon is discussed further in Module 8.
6. Check the local air quality – When exercising outdoors, use the local air quality forecast to help plan the best time for a workout.
7. Use chemicals safely – Read pesticide labels carefully. Lock up pesticides, paints, and cleaners where children cannot reach them.
8. eCycle – Take old computers, DVD players, and other electronics to a recycling center. This helps keep hazardous substances out of landfills.
9. Enjoy the outdoors safely – Find out the quality of beach water from state offices and get the UV index to protect yourself from the sun.
10. Spread the word – Teach others at work, school, and home. Encourage them to Pick 5 for the Environment.
Visit the U.S. Environmental Protection Agency website for more information
Required Videos:
When we look at weatherization projects, we are always looking at how heat and energy are being transferred from one area to another. This is important because we want to gain a greater understanding of our structure and the weatherization concept we should employ to maximize our weatherization efforts. The first YouTube video presentation will provide you with a greater understanding of conduction, convection, and radiation principles, and the second video presentation will address the concepts of temperature and energy and role it plays in heat transfer.
Conduction, convection, and radiation
Required Presentation:
