Chapter 17 Energy: Some Basics

Earth's Energy Balance High-grade: Sun –electromagnetic spectrum: all wavelengths –albedo: reflectivity Low-grade: Earth –earthshine: heat energy radiated back into space Negative Feedback

Energy Crises Greece and Rome (60 A.D.) –wood and coal –solar heating and laws to protect California (2001) –“ rolling blackouts” –energy demand grew due to economic growth –buy “emergency power” –hard path vs. alternative

Energy Basics Energy: the ability to do work - can be converted or transformed, but total energy is always conserved - joules and Btu's Potential Energy: energy that is stored - gravitational (dams); chemical (coal); nuclear Kinetic Energy: energy of motion Work: Force x Distance Power: Work in given amount of time - watts; kilowatts

Energy Efficiency First Law Efficiency –Neither created not destroyed; always preserved –The amount of energy without any consideration of the quality of availability of the energy; ratio of actual amount delivered to amount supplied Second Law Efficiency –How well matched the energy end use is with the quality of the energy source –High to low quality

Worldwide Energy Use Today 13.8 terawatts Population growth and higher standard of living U.S. - 5% of world's population yet 25% of energy consumed –heat engines

Fossil Fuels and Alternative Energy Sources 90%: Fossil fuels –petroleum; natural gas; coal (electricity!) –non-renewable Alternative: might replace fossil fuels in the future; some renewable –geothermal- solar –nuclear- wind –hydropower

Energy Losses Largest losses are associated with the production of electricity and with transportation –burning of fossil fuels in engines; waste heat (low-grade) –every step in converting energy to a different form is less than 100% efficient

Energy Conservation, Increased Efficiency and Cogeneration Conservation: getting by with less demand for energy Energy Efficiency: designing equipment to yield more energy output from a given amount of input energy Cogeneration: a number of processes designed to capture and use waste heat rather than simply to release it into the atmosphere

Improving Efficiency 60% of total energy use: –space heating and cooling –water heating –industrial processes (to produce steam) To improve efficiency, must address: –building design –industrial energy use –auto design

Energy Policy Hard Path vs. Soft Path –Hard Path: finding greater amounts of fossil fuels and building larger power plants centralized requires no new thinking; no realignment of political, economic, or social conditions; little anticipation of coming reductions in oil production –Soft Path: involves energy alternatives that emphasize energy quality and flexibility localized sustainable energy sources integrating high technology solutions diverse energy sources

Energy Policy Energy for Tomorrow –Difficult to predict due to economic, political and social assumptions as well as seasonal and regional variations in energy consumption Integrated, Sustainable Energy Management –Integrated Energy Management: no single energy source can provide all the energy required by the world –Sustainable Energy Management: provides reliable sources of energy without causing serious harm, all while ensuring that future generations inherit a fair share of Earth’s resources

To meet our energy needs... Energy efficient land-use planning –maximizes accessibility of services –minimizes need for transportation Agricultural practices and personal choices –eating locally grown foods (lower trophic level) Industrial guidelines for factories –promote energy conservation –minimize production of waste