Chapter 12 Renewable Energy

Heating Buildings and Water  Passive solar energy- no machines used

Heating Buildings and Water  Active Solar Energy  Collecting and absorbing the sun’s energy, and using pumps or fans distribute heat  Ex:  Large solar plants- can create very hot environments overhead and can incinerate animals that fly over. Solar Thermal Electric Generation Photovoltaic Solar Cells

Biomass  Advantages  Reduces dependence on fossil fuels  Often uses waste materials  Can be renewable  Disadvantages  Requires land, water and fossil fuel energy  Can lead to  Deforestation  Desertification  Soil erosion

Wind Energy  No waste - clean source of energy  Biggest constraints:  Cost  Public resistance (NIMBY)  Few environmental problems  Kills birds and bats

Hydropower

Hydrogen as a Fuel Source  Hydrogen gas (H 2 )  Comprised of two hydrogen molecules  Large amounts of available energy  Explodes when combined with oxygen releasing energy and forming water

Geothermal and Tidal Energy  Other forms of renewable energy (not from solar)  Geothermal energy- energy from the Earth’s interior  Tidal energy- relies on ebb and flow of the tides

Energy Savings in Commercial Buildings

Saving Energy at Home

Atoms and Radioactivity  Nucleus  Comprised of protons (+) and neutrons (neutral)  Electrons (–) orbit around nucleus

Introduction to Nuclear Energy  Nuclear energy  Energy released by nuclear fission or fusion  Nuclear fission  Splitting of an atomic nucleus into two smaller fragments, accompanied by the release of a large amount of energy  Nuclear fusion  Joining of two lightweight atomic nuclei into a single, heavier nucleus, accompanied by the release of a large amount of energy

Radioactive Isotope  Unstable isotope  Radioactive Decay  Emission of energetic particles or rays from unstable atomic nuclei  Example  Uranium (U-235) decays over time to lead (Pb-207)  Each isotope decays based on its own half-life

Radioactive Isotope Half-lives

Nuclear Fission

How Electricity is Produced

Pros and Cons of Nuclear Energy  Pros  Less of an immediate environmental impact compared to fossil fuels  Carbon-free source of electricity  May be able to generate H-fuel  Cons  Generates radioactive waste  Many steps require fossil fuels (mining and disposal)  Expensive

Pros and Cons of Nuclear Energy

Cost of Electricity from Nuclear Energy  Cost is very high  20% of US electricity is from Nuclear Energy  Affordable due to government subsidies  Expensive to build nuclear power plants  Fixing technical and safety issues in existing plants is expensive

Safety Issues in Nuclear Power Plants  Meltdown  At high temperatures the metal encasing the uranium fuel can melt, releasing radiation  Probability of meltdown is low  Public perception is that nuclear power is not safe  Sites of major accidents:  Three Mile Island  Chornobyl (Ukraine)

Chornobyl  worst accident in history  Large amounts of radiation escaped into atmosphere

Chornobyl  Radiation spread was unpredictable and uneven

Radioactive Wastes  Long term solution to waste  Deep geologic burial – Yucca Mountain  As of 2004, site must meet EPA million year standard

Radioactive Waste  Temporary storage solutions  In nuclear plant facility (require high security)  Under water storage  Above ground concrete and steel casks  Need approved permanent options soon.