RENEWABLE ENERGY SOURCES

Transcription

1 RENEWABLE ENERGY SOURCES

2 State of Renewable Energy Only 6% of energy used in U.S.; 18% of world s energy use Why so low, if most renewable energies are environmentally friendly and potentially limitless? Lack of subsidies in past to develop them (most subsidies still go to oil, coal and nuclear growth) Inaccurate energy pricing if one includes environmental clean-up costs in the pricing of fossil fuels, then they are more expensive than renewables.

3 Energy Source 1 - Biogas Biogas is gas collected from decomposition of organic materials. Most biogas is primarily made of methane but contains many other gases from decomposition Gas could be burned to generate heat or electricity.

4 How do you make biogas? Most commonly you put it in a methane or waste digester. This is a bin that is anaerobic (area with no oxygen). These conditions are ideal for decomposing bacteria to eat the wastes. By-product is gas (mainly methane), which is collected and then can be burned.

5 Biogas Advantages Cleaner burning emissions Reduces amount of methane and nitrous oxide that goes into air Reduces volumes of waste Can be set up anywhere were there is waste stream Reduces need for other fuel sources Burning methane converts it to carbon, which is less powerful greenhouse gas Disadvantages Not likely able to provide large-scale energy needs to a nation Can have an odor Biogas is not pure; impurities corrode equipment Impure gas requires effort and energy to clean for use in burning Not really able to use leftover waste for fertilizer

6 Energy Source 2 - Hydroelectric Using the power of falling/moving water to make electricity Electricity Generation: Water behind the dam falls down the spillway of the dam and turns a turbine which is connected to generator Largest Hydropower Development Areas: Canada, China, Brazil, United States, Russia Norway gets 99% of its power from hydropower

7 Tidal Power A small number of plants exist in which tidal action of the ocean turns turbines. Where?: Alaska, France, England Only a few places, since there are limited sites that have the tidal flow needed to make enough energy. Tidal power is expensive and difficult to build.

8 Hydroelectric Power Advantages Efficient in production Non-polluting Low greenhouse gas emissions Dams can help in preventing floods Provides source of water Reservoir of dam can be used for recreation Long life span of energy infrastructure Disadvantages High construction costs Danger of collapse or terrorism on dams Upstream flooding of habitats and displacement of human populations Major impact on abiotic and biotic parts of dammed river Lots of CO 2 in tropical reservoirs (due to decomposition of submerged biomass)

9 Energy Source 3 - Geothermal Energy from the Earth s interior Electricity Production: Drill and pump dry steam directly from ground to turn a turbine which is connected to a generator Pump high pressure hot water from ground and put into low pressure container to make steam. Steam is used to turn a turbine. Turbine runs a generator Major Producers: United States (creates the most, even though it is less than 1% of our power needs), Iceland, Philippines, New Zealand, Japan Notice most places are near plate tectonic boundaries

10 Geothermal Heat Pumps Another way to use geothermal energy is as a heating medium in homes The Earth s crust maintains a much more constant temperature than on the surface (around F) Can build systems to pump this air from interior to surface and back into the ground again In summer, the pumped ground air cools house In winter, the pumped ground air warms the house

11 Geothermal Energy Advantages Low greenhouse gas emissions No air pollution Low land use and disturbance Efficient Low cost to run, once plants are established Disadvantages Expensive to build power plants Limited sites with accessible sources of energy Some greenhouse gas emissions (released from underground) Often has an odor (due to hydrogen sulfide stinky egg smell) Can overpump steam or water from an area, leading to loss of resource over time

12 Energy Source 4 - Solar Energy Passive Solar Energy -- solar energy that requires no mechanical power (pumps/fans) to collect and/or distribute the energy Examples: Having water tank directly placed in the sun to heat water Solar Cookers cooking food in a solar radiation reflecting oven Orienting building to receive sun (like south-facing windows) Installation of skylights in homes Use of stone or concrete walls/floors that absorb solar energy in the day and release at night

13 Energy Source 4 Solar Power Active Solar Energy solar energy that is collected or distributed via mechanical power Example: Collector absorbs solar radiation which transfers heat to a heat absorbing fluid which is pumped to places to spread the heat energy.

14 Energy Source 4 Solar Power Active Solar Energy solar energy that is collected or distributed via mechanical power Example: Photovoltaic Cells (solar panels) Made of silicon and other trace amounts of metals Sun hits the silicon, causes electrons in silicon atoms to move Electrons move into embedded wires of the panel and out the panel as electricity Development Areas for Solar: Germany, Spain, Portugal, southwestern U.S., Japan

15 Solar (Photovoltaic Electricity) Advantages Can work on cloudy days Fairly easy installation process No greenhouse gas emissions Non-polluting to air or water No use of fossil fuels to directly run them Can be moved or changed easily Can be placed on homes and roofs Disadvantages Need sunny areas to be useful Inefficient Need a storage system to hold excess created energy High costs for panels High land use to place panels Panels make DC current, which needs to be changed to AC Toxic materials used to make panels Difficulty in disposing of toxic panel materials Materials used to make panels need to be mined

16 Energy Source 5 - Wind Having wind move a turbine for the generation of electricity Only produces 1% of U.S. electricity (goals to make it up to 20% of U.S. power in future) Major Development Areas: U.S. Great Plains (Saudi Arabia for wind), Germany, Denmark (20% of its power from wind), Spain, China, India

17 Wind Power Advantages No air pollution or greenhouse gases Efficient Understood on how to build Fairly easily built Can be on land or sea (offshore wind farms!) Land in between turbines could be used for other purposes General public interest Disadvantages Need for places with steady winds Hard to store excess electricity made Need alternate power source for when winds are low Wind power is made in rural areas away from cities where the power is needed power needs to be transported! Visual pollution to some Can be noisy to some people Can interfere with migratory patterns and flight paths of small birds, birds of prey, and bats Requires lots of money upfront for initial construction

18 Energy Source 6 - Biomass Biomass fuel is plant materials or animal wastes used in some way to make energy Examples of using solid biomass: Burning fuelwood wood burned for direct heat Burning animal dung for fuel Solid biomass is renewable and can be grown quickly Growing too much biomass for burning could sap soil of nutrients over long term.

19 Biofuels Liquid or gas conversions of biomass solids to fuel Two main types of liquid biofuels are ethanol and biodiesel Countries that use a LOT of biofuels: Brazil (make ethanol from sugarcane crop 40% of vehicles run on this) U.S. (ethanol from corn) European Union China

20 Ethanol Any organic material with sugar is broken down into simple sugars (using enzymes) Sugars are fermented Alcohol is created and separated. Often mixed with gasoline to make gasohol Example: E85 (85% ethanol, 15% gas) Used in flex fuel vehicles vehicles that can use a variety of fuels in the engine Ethanol produced from sugarcane makes a LOT more energy compared to ethanol made from corn This is why Brazil s ethanol production is cheaper than the U.S. production.

21 Biodiesel Diesel fuel primarily made from vegetable oils from soybeans, sunflowers, palms, and fats from vegetable oils These oils will undergo transesterification which separates biodiesel from the glycerin in the oils. Diesel is considered cleaner burning than ethanol however most domestic vehicles are not set up for its use Trucking fleets however do use diesel fuel Biodiesel is more energy efficient to produce and delivers more energy than ethanol.

22 Biofuels Advantages Cleaner burning than fossil fuels for some air pollutants less CO and PM (especially biodiesel) No net carbon, if growing of fuel material is sustainable Can use a variety of any organic materials/wastes Can be used in a variety of ways Reduce use of fossil fuels Disadvantages Could be nonrenewable, if overharvesting of materials occur Using food products for fuel Still have greenhouse gas emissions (if not properly managed) Need land to grow fuel material High cost on land (farming, erosion, water use) Biodiesel can increase NOx and smog emissions Higher cost Can corrode engines Low energy yield from certain crops (like corn actually use more energy in making it then what you get from it)