1. Energy Efficiency and Renewable Energy Chapter 16

2. Energy Efficiency ► The percent of the total energy input that is converted into useful work and is not lost as waste heat. ► 84% of commercial energy in the US is wasted.  Remember the second law of thermodynamics ► WAYS TO IMPROVE EFFICIENCY  Insulation  Elimination of air leaks  Cogeneration (combined heat and power – 2 useful forms of energy like steam & electricity are produced from the same fuel source)  Efficient electric motors  High-efficiency lighting  Increased fuel economy

3. Laws of Thermodynamics ► 1 st Law: Energy can be neither created nor destroyed ► 2 nd Law: When energy is changed from one form to another, some of the useful energy is always degraded to lower quality, more dispersed, less useful energy

4. Efficiencies of some common energy conversion devices

5. Using Solar Energy to Provide Heat and Electricity  Passive solar heating – heat is absorbed and stored directly from the sun and released slowly throughout the day and night; a small backup heating system may be used  Active solar heating – collectors absorb solar energy, and a fan or pump supplies part of a building’s space-heating or water-heating needs

6. Using Solar Energy to Provide High- Temperature Heat and Electricity  Solar thermal systems  Photovoltaic (PV) cells

7. Hydroelectric Power Generation ► The energy of flowing water can be harnessed to generate electricity.  Large Scale Dams  Small Scale Dams (no reservoir behind it)  Waterfalls (natural phenomena) ► Renewable ► Environmental Problems  Flooding behind dams  Fish are blocked

8. Wind Power ► Cheap. ► Only certain areas have potential to generate a economically viable amount of power from winds. ► Concerns about impact on bird populations. ► Concerns about aesthetics. ► Fastest growing source of energy since 1990.

10. Using Biomass to Produce Energy ► Biomass: plant materials & animal wastes used as sources of energy.  Wood  Dung  Paper ► Can be burned directly or converted into synthetic natural gas (biogas) or liquid biofuels (ethanol, methanol). ► Biodiesel: made from plant oils and can be used in diesel engines. ► Problem with using biomass is that during the combustion CO 2 is released. CO 2 is a major contributor to global warming.

11. Goodbye Oil and Smog, Hello Hydrogen ► Efficient method for generation of hydrogen (the trick is to do this cleanly) ► Store hydrogen – in compressed tanks (expensive); too heavy for cars but ok for buses and trucks ► Use fuel cells to generate electricity ► Only water vapor is released from the fuel cell – which is a greenhouse gas, but would be contributing insignificant amounts

12. The Solar-Hydrogen Revolution

14. Geothermal Energy ► Electricity generated by utilizing naturally occurring geological heat sources. ► Large scale electrical generation is possible in areas near geysers or hot springs by utilizing naturally occurring steam ► Provides relatively low quality energy, perfectly good for heating and cooling. ► Small scale use of geothermal energy includes laying pipes down deep enough that the ground is warmer than the air in winter and cooler than the air in summer. This is called a heat pump.

15. Entering the Age of Decentralized Micropower  Centralized power systems – easy targets for power outages  Decentralized power systems – dispersed small scale micro power plants  Micropower systems – produce 1-10,000 kilowatts of power; examples include wind turbines, fuel cells and solar panels on homes

16. Solutions: A Sustainable Energy Strategy Fig. 16-44 p. 414