Chapter 18 Renewable Energy 18 1 Renewable Energy

Chapter 18 Renewable Energy

18. 1: Renewable Energy Today

Renewable Energy Definition • Energy from sources that are constantly being formed • Types: – Solar Energy – Wind Energy – Power of Moving Water – Earth’s Heat • All energy sources (renewable and nonrenewable) will affect the environment

Solar Energy • Almost all renewable energy comes directly or indirectly from the sun • Directly: Used every day, like when the sun shines on a window and heats the room • Indirectly: Electricity can be generated in solar cells

Passive Solar Heating • Definition: the use of sunlight to heat buildings directly = reduces energy bills

Active Solar Heating • Definition: The gathering of solar energy by collectors that are used to heat water or a building • Usually mounted on a roof, in >1 million US homes • About 8% of the energy used in the US is used to heat water, so ASH could save a lot of energy

Photovoltaic Cells • Solar cells that convert the sun’s energy into electricity • Positive: No moving parts and do not pollute • Negative: Produce a small electrical current – a LOT are needed (small city=hundreds of acres of solar panels)

Wind Power • Sun energy warms the Earth unevenly, which causes air to flow in the atmosphere (wind) • Wind Turbines convert wind into electrical energy • The fastest growing energy source in the world! • Take little space so can be installed on farmland with little impact • Becoming less expensive and more efficient

Problems/Future of Wind Power • Problems: Electricity transport from rural to urban areas, eye sores • Future: – Scientists estimate that the windiest spots on Earth could generate more than 10 times the energy used worldwide – Could be used to produce hydrogen from water – All large energy companies have wind power plans in their futures • Time lapse building of a wind turbine: https: //www. youtube. com/watch? v=84 Be. Vq 2 Jm 88

Biomass • Biomass fuel: consists of plant material, manure, or any other organic material used as an energy source • Major sources of energy in developing countries (wood/dung) • >1/2 of all wood cut in the world is used as fuel for heating/cooking • Negatives: Deforestation and air pollution

Biomass: Methane • Methane gas is produced when bacteria decompose organic waste • Methane can be burned to generate heat/electricity • China = more than 6 million households use biogas digesters to ferment manure and produce gas to heat/cook with • Some US landfills: use methane from trash decomposition to generate electricity

Biomass: Alcohol • Biomass can create liquid fuels like ethanol from fermenting fruit/agricultural waste/corn • Ethanol (gasohol) can run cars/trucks with less air pollution than a typical car

Hydroelectricity • Electrical energy produced by falling water • Accounts for 20% of the world’s electricity • Dams are used to hold back a reservoir of water which is released to turn a turbine, generating electricity

Hydroelectricity Benefits • • Expensive to build, but inexpensive to use No air pollutants that cause acid rain Last longer than fossil fueled-powered plants Other benefits like flood control, drinking/agricultural/industrial/recreational water sources

Hydroelectricity Disadvantages • River flow is changed = BAD… • Flooded habitats above the dam, reduced water below the dam which disrupts ecosystems (ex: salmon fisheries in the NW US destroyed because salmon can’t swim upstream to spawn) • People living behind the dam experience floods • Burst dam = death • River sediment build-up behind the dam makes farmland below the dam less productive • Decaying, trapped plant matter can release tons of greenhouse gases

Future of Hydroelectricity • Developing countries continue to build dams • US trending towards micro-hydropower (in small stream, sometimes even floating in the water) • Micro-hydropower is much cheaper and allows energy to be generated in smaller streams in more remote areas

Geothermal Energy • Energy produced by heat within the Earth • US = largest producer in the world • STEPS: (1) Steam rises through a well (2) Steam drives turbines, generating electricity (3) Leftover liquid water is pumped back into the hot rock to be reheated and used again

Geothermal Heat Pumps • Disadvantage: Water used must be managed carefully so it is not depleted

18. 2: Alternative Energy and Conservation Still in development…looking for something cost effective and with “acceptable” environmental effects

Tidal Power • Kind of like a hydroelectric dam • As the tide rises, water enters a bay behind a dam • Gate closes and reopens during low tide, allowing water to rush through, spinning a turbine which generates electricity • Positives: renewable and nonpolluting • Negatives: expensive, not many suitable locations

Tidal Power: Diagram

Ocean Thermal Energy Conversion • In the tropics, there can be a large difference in ocean surface water and deep water temperatures (as much as 43°F) • This temperature difference can be used to produce electricity • Steps for energy production…

Ocean Thermal Energy Conversion (OTEC) Plant 1. Warm surface water is boiled in a vacuum chamber 2. Steam produced drives a turbine to produce electricity 3. Cold, deep-ocean water will condense steam 4. Steam turned water is used again

OTEC Power • US and Japan have experimented, but have not been able to make this energy source cost effective • Inefficient: 1/3 of the electricity produced is used to pump cold water up from the deep ocean • Unknown environmental effects of pumping large amounts of cold water to the surface

Hydrogen • The most abundant element in the universe • Does not release pollutants when burned (unlike burning fossil fuels/biomass) • When hydrogen is burned, it combines with oxygen to make water vapor and small amounts of nitrogen oxides • Made by using electricity to split H 2 O molecules or through the use of any material containing a lot of hydrogen • Future: plants grown to produce hydrogen cost effectively

Hydrogen: Challenge/Solution • Hydrogen takes a lot of energy to produce • If this energy came from burning fossil fuels, generating hydrogen would be expensive and would be polluting • Solar cells could use electricity generated to split water molecules – Hydrogen could be stored in pressurized tanks and transported in pipelines – Hydrogen could be used as it is produced, in fuel cells

Fuel Cells • Device that produces electricity chemically by combining hydrogen fuel with oxygen from the air • Creates energy with water as the only byproduct • Can be fueled by anything that contains plenty of hydrogen, including natural gas, alcohol, or even gasoline

Energy Efficiency • Reduce Energy Use: lifestyle changes, increase energy efficiency • Energy Efficiency: percentage of energy put into a system that does useful work • Most devices are fairly inefficient: more than 40% of all commercial energy used in the US is wasted • Increasing efficiency may involve sacrifices or investments in new technology

Efficient Transportation • Most vehicles have pretty inefficient engines and produce a lot of pollution • Engine design may change radically to meet the need for more efficient transportation • Increasing the use of public transportation systems would also help increase energy efficiency of American life

Hybrid Cars: Energy Efficient Vehicles • Use small, efficient gasoline engines, and also use electric motors when extra power is needed (like when accelerating) • Don’t cost too much more than conventional vehicles, cost less to refuel, and produce less pollution

Hybrid Cars • Convert energy of braking into electricity, which is stored in the battery • Gasoline engine can shut off to save fuel (like when stopped at a red light) • Aerodynamic and need less energy to accelerate

Cogeneration • Definition: the production of two useful forms of energy from the same fuel source – Ex: waste heat from an industrial furnace can power a steam turbine that produces electricity • Have been used for years to supply heat and electricity to multiple buildings at specific sites

Energy Conservation • The process of saving energy by reducing energy use and waste • Use energy efficient devices • Waste less energy • DOES make a difference (between 1975 and 1985, conservation made more energy available in the US than all alternative energy sources combined did)

YOUR Home • The average household in the US spends more than $1200 on energy bills each year • A lot of that energy is wasted through poorly insulated windows, doors, walls, and the roof • There are dozens of ways to reduce energy use around the home • Using less of any resource usually translates into saved energy