I. I.Energy B. B.Renewable 1. 1.Hydroelectric Currently supplies ~20% of electricity production worldwide a. a.Small (<30 MW) Less impact but less power than large facilities b. b.Large (>30 MW) Includes immense dams with potentially large impacts Ex – Itaipu Dam (Brazil, Paraguay, Argentina) = 12,600 MW Ex – Three Gorges Dam (China) = 18,200 MW Benefits Inexpensive, once facility exists Minimal environmental impact – Little pollution, no GHGs Many facilities already in place May permit flood control Relatively efficient and nondestructive Concerns Limited use geographically Environmental degradation in flooded areas Environmental degradation downstream Detrimental to some aquatic animals (Ex – salmon) Tropical dams trap organic material  methane Rainfall variation can reduce reliability

I. I.Energy B. B.Renewable 2. 2.Wind Power captured with wind turbines The Dakotas and Texas have sufficient wind capacity to supply energy needs of entire United States Benefits “Free” Minimal environmental impact – Little pollution, no GHGs Can produce electricity without being connected to power grid Multiple uses of land Concerns Limited use geographically Inconsistent energy source Expensive to maintain May be dangerous to birds/bats Low power density Eyesores (offshore?) Weather effects? Skegness

I. I.Energy B. B.Renewable 3. 3.Solar Can be generated by a. a.Focusing heat of sun on central point that heats up; heat used to produce steam, which turns turbine b. b.Photovoltaic (PV) cells – Convert energy from sun directly to electricity; each PV panel typically produces small amount of electricity, but panels can be grouped Benefits Abundant – “The amount of solar radiation striking the earth over a three-day period is equivalent to the energy stored in all fossil energy sources.” “Free” Minimal environmental impact – Little pollution, no GHGs PV systems have no moving parts, need little maintenance Can produce electricity without being connected to power grid Concerns Limited use geographically Inconsistent energy source Expensive: $ /kWh vs. $ /kWh on latest bill Requires special materials to harvest energy Low power density; long-term storage of energy

I. I.Energy B. B.Renewable 4. 4.Biomass and Waste Biomass fuels include residues from logging; mill operations; processing of wood, pulp, paper, fiberboard; agricultural crops; livestock and poultry operations; food processing; demolition (urban wood waste) Waste fuels include combustible residues from industrial processes, municipal solid & liquid wastes Currently supplies ~15% of electricity production worldwide, more in developing countries Benefits Readily available fuel Inexpensive Reduces waste stream Concerns Emissions – Especially for waste combustion Low fuel density Technology still being developed (mainly emissions)

I. I.Energy B. B.Renewable 5. 5.Geothermal Heat from deep within earth captured and used to turn an electric generation turbine Benefits Inexpensive Minimal environmental impact – Little pollution Energy security – US has extensive resources Concerns Limited use geographically Not truly renewable (water injection can prolong life of geyser field) Geothermal emissions may include CO 2 and H 2 S, as well as various toxic compounds Not economically viable in most areas Geological risks

I. I.Energy B. B.Renewable 6. 6.Biofuels Bioalcohols Biodiesel Biogas Benefits Renewable Energy security Reduced waste stream for raw materials Reduced environmental impacts vs. other energy sources Concerns “Food vs. Fuel” – Elevated food prices Not carbon neutral or carbon negative Growing crops & processing for fuel requires land and water Pesticides may contaminate local aquifers Emissions from biofuels (air pollution)

Gibbs et al. 2008

Righelato and Spracklen 2007