Topic 7: Alternative Energy Flashcards
1
Q
How have we used wind as technology in historical contexts?
A
- sailing ships
- windmills to pump water, milling grain
- wind pumps, pump groundwater for ranching
2
Q
How is atmospheric circulation of wind driven?
A
- driven by gradient in radiation receipt between equator and poles, differential heating and cooling of continents and oceans
- 3 main atmospheric pressure cells; hadley, ferrel, polar
- wind blows from high to low pressure, deflected by coriolis effect
- surface friction reduces wind speeds and causes wind to blow diagonally across isobars
3
Q
describe the distribution if wind energy. Is it consistent?
A
- variable wind speed and wind strength across the planet
- energy comes in short bursts, and so there is no consistent output
4
Q
What are wind farms?
A
- areas that contain up to several hundred wind turbines,
- can cover several hundred square km, but land inbetween can still be used
- siting of turbines are very important to maximize wind speeds
5
Q
How do wind farms generate power? Are there issues with this?
A
- turbines connection to substation, voltage increased with a transformer and connected to the grid
- problems of variability and intermittency of power production from turbines
- the power production needs to match consumption for grid stability
-pumped storage hydroelectricity used for on-grid storage during peak wind powere production intervals
6
Q
What are the economic costs of wind energy?
A
- near zero fuel costs
- high capital costs, from construction maintenance, etc.
7
Q
What are the environmental effects of wind energy?
A
- zero fuel consumption, no emissions of greenhouse gasses or other pollutants during operation
- some CO2 emissions from producing concrete foundations
- neodymium used in wind turbines does have some pollution concerns due to way they are manufactured
- no land use concerns, often built on previously cleared land so no tree clearing, and land still used for crops or grazing
- bird kills are a major criticism of wind power, however evidence suggests bird kills are very low
- bats killing is more of a concern, they are attracted to the low pressure zones, and more susceptible to wind turbine kills than birds
8
Q
What energy do we receive from the sun? how much is reflected back?
A
- receive insolation radiation from the sun to the earth atmosphere, huge amount received every second
- 30% of solar energy is reflected back into space
- remaining is absorbed into clouds, oceans, land masses
9
Q
What kind of energy from the sun is available for us? What are variables to consider with this availability?
A
- solar energy is renewable and a huge energy source
- annular solar energy budget is twice as much as total energy available from all known non-renewable energy reserves
- however, availability varies with distances from the equator and cloud cover patterns
- solar energy is most efficient with high sun angles, consistent day lengths, and low cloudiness
10
Q
What are the types of solar power?
A
- passive solar energy
- active solar energy
11
Q
What is passive solar energy?
A
- solar energy where you are not extracting electricity, simply taking the solar energy in, absorbing the sunlight as heat, and holding the heat in
- considerations are building orientations, thermal properties of materials, etc.
- ex. greenhouses
12
Q
What is active solar energy?
A
- solar energy that is actively gathers and
- ex. photovoltaic panels, solar thermal collectors
13
Q
What are solar thermal collectors?
A
- flat plate collectors of evacuated tube collectors for domestic hot water
- provides small scale houses with hot water
tubes collect/absorb heat, transfers heat to container holding water, heats the water
14
Q
What are solar ovens?
A
- type of active solar power
- device that concentrates sunlight via a reflective surface into a small cooking area
- light-absorbing black inner surface to convert light to heat
- enclosed to prevent heat loss
- no fuel needed, non polluting
- limited by cloudy weather and wind, takes a long time to cook
15
Q
What are heliostats?
A
- type of active solar energy that actually produces electricity
- similar to light focused by a magnifying glass
- extensive array of mirrors used to focus sunlight onto central tower-mounted receiver
- mirrors computer is controlled to maximize solar reflectance as sun moves across the sky
- receiver is either a direct steam-producing boiler to drive electric turbine directly or a thermal storage facility of liquid sodium linked to heat exchanger and turbine
16
Q
what are some types of active solar energy?
A
- solar thermal collectors
- solar ovens
- heliostats and parabolic reflectors
- photovoltaic cells
17
Q
What are parabolic through reflectors?
A
- similar idea to heliostat, but has no central receiver
- mirrors focused on a central tube, that contains a heat transfer medium
- heat transfer medium (hydrocarbon, molten metal, or salts) is passed through central tube surrounded by curved reflector
- fluid is circulated through the system to heat transfer, steam is generated by heat exchanger to drive turbines
18
Q
What are photovoltaic cells
A
- type of active solar power
- solar panels. Direct conversion of radiation to electricity
- sunlight interacts with a semi-conductor to produce an electric current
- does not gather heat, directly converts it instead
- cells are arranged in panels, and panels arranged in arrays
19
Q
What are some advantages of photovoltaic cells?
A
- power production is pollution free
- low maintenance
- rapidly increasing efficiency with decreasing costs
20
Q
What are some disadvantages to photovoltaic cells?
A
- may contain environmentally toxic metals (lead, mercury,)
- cadmium telluride (a semi-conductor used) is toxic if dust is inhaled or ingested
- high capital costs to source semi-conductors/mine for them
