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7.5 Renewable energy-alternative energy sources, Screen Shot 2020-04-27 at…
7.5 Renewable energy-alternative energy sources
Solar energy
A building that has enough access to sunclight can get all or most of its heat throu a passive solar heating system
Such system abosrbs and stores heat from the sun directly within a well-insulated, airtight structure
Active solar heating system captures energy from he sun by pumping a heat-absorbing flud such as water through special collectors
We can use indirect solar energy to help cool buildings
Solar thermal systems, CSP, use different methods to collect and concentrate solar energy to boil water and produce stem for generating electricity
Two systems: Parabolic mirrors and moving mirrors
We can convert solar energy directly intro electrical energy usinf photocoltaic cells, commanly called solar cells
Most solar cells are thin transparent wafers of purifies silicon or polycrystalline silicon with trace amounts of metals that allow them to conduct electricity
Advantages:
Solar cells emit no greenhouse gases or pollutants
Contain n toxic materials that must be recovered when the cells wear ot after 20-25 years of use
Simple, easy to use, low maintenance equipment helps bring power to remote areas
Disadvantages:
Low energy efficiency - typically convertonly 15-20% of icoming solar eergy into electricity
Solar cells cannot produce electricity at night, and storing energy in large atteries for use at night and on cloudy day is expensive
Wind power
Wind is air in motion. Wind is an indirect form of solar energy
Wind turbine and wind farms
Can be 60 stories tall and have 70 meter long blades- height exposes them to stronger and more constant winds found at higher altitudes. Blades spin turn an electric geerator which produces electricity
Groups of wind turbines called wind farms transmit electrical energy to electrical grids
Wind power use is increasing
Wind poer has been the world's second fastest growing source of electricity after solar cells
Wind powe has the potential to produce 40 times the world's current use for electricity
Advantages:
Wind is abundanr, widely distributed, and inexhaustible
Wind powe is mostly carbon free and pollution free
Fast and relativeley cheap to build and expand
Although wind famrs can cver large areas of land, the turbines themselves occupy only a small portion of the land
Disadvantages: Birds and bats: collision with turbines kill 234,000 birds and 600,000 bats each year in the us
Even so, new turbines and farms are placed and designed to reduce bird and bat deaths:
Positioned away from migration routes and nesting areas
Slowe blade rotation
UV coatings and ultrasonic devices to deter birds and bats
Geothermal
Energy is heat stores in soil, underground rocks, and fluids in the earth's mantle
A geothermal heat pump system can heat and cool a house almost anywhere in the world
According to the EPA, a geothermal heat pump system is the most energy efficient, reliable, environmentally clean, and cost effective way to heat or cool a space
Hydrothermal reservoires can be used for mass heating or generatig electricity
Hydrothermal reservoires are deeer, more concentrated sources of geothermal energy
Advantages:
Medium net energy
Low CO2 emissions
Disadvantages:
Drilling geothermal wells is expensive and risky
Not many hydrothermal sites with concentration of heat high enough to make it affordable
Cn be non renewable if heat is extracted faster than can be restored
Biomass
Energy can be produced by burning the solid biomass or organic matter found in plants or plant related material
Biomass can also be converted into liquid biofueld for use in motor vehicles
The two most commont liquid biofuels are:
Ethanol
Biodiesel
Biofueld crops can be grown throughout much of the world, no net increase in CO2 emissions, an are easy to store and transport
Some biofuels acturally produce 20% more greenhouse gases to atmosphere
Crops requires a huge amount of wte, and ethanol distilleries produce large volumes of watewater
In many areas, tropical rainforest, grasslands, and wetlands are being destroyed to make way for biofuel cash crops, especially palm oil, because it is more profitable than food crops
Hydropower is any techlogy that uses kinetic energy of flowing and dalling water to produce electricity
They use potential kinetic energy from flowing rivers
Dams: store up water and allow it to flow through a turbine to generate electricity
Least expensive renewable energy resource
Reservoirs fill with slit and become useless
Flood and destroy terrestrial habitats upstream
Reduce flow of water and sediments deltas and estuaries
Hydrogen
Advantages:
Only producr is water- no C02 emissions or air pollutants
Fuel cells are more efficient than an internal combustion engine
Fule cells have no moving parts - require little maintenance
