renewable energy notes
The four primary consumers of energy in the US in 2007 were
- Industrial: 32%
- Transportation: 28%
- Residential: 22%
- Commercial: 18%
- the sun is free
- In principle, the amount of solar energy that reaches the Earths surface could provide for all huan energy needs forever
- The distribution of solar energy over the continental U.S. in watts per square meter
- The desert regions of the southwest U.S. receive the most sunlight
- clean energy
- produces no hazardous liquid, or waste
- does not create water or air pollution
- The two areas in which solar energy can make the greatest contribution are in space heating and in the generation of electricity
- These are uses that account for two-thirds of U.S. energy consumption
- The simplest approach to solar heating is passive-solar heating
- The building design should allow the maximum amount of sunlight to stream in through south and west windows during the cooler months
- This heats the house and materials inside
- Trees can be positioned to shade the house in summer
- Wide eaves can shade windows in summer, but allow winter sunlight to enter
- Drapes and shutters can insulate window areas in winter
- It has been estimated that 40 to 90% of most homes’ heating requirements could be supplied by passive-solar heating systems
- 100% solar homes have been built, but such homes usually cost many tens of thousands of dollars more to build
- Retrofitting older homes to be solar efficient can be too costly
- Over insulation can aggravate indoor pollution
- Direct production of electricity using sunlight is accomplished using photovoltaic cells, also called solar cells
- They have no moving parts and are “clean” energy
- They are used to power the space station and to provide electricity in remote areas on Earth
- A major limitation is cost, which greatly exceeds the cost of producing electricity using fossil fuels or nuclear power
- The best solar cells are only 20% efficient and only provide 50 watts of electricity per square meter of cell size
- energy is free
- Net energy is moderate (active) to high (passive)
- Quick installation
- No CO2 emissions Very low air and water pollution
- Very low land disturbance (built into roof or windows)
- Moderate cost (passive)
- need access to sun 60% of time
- Sun can be blocked by trees and other structures
- Environmental costs not included in market price
- Need heat storage system
- High cost(active)
- active system needs maintenance and repair
- Active collectors unattractive
- Magma rising from the mantles brings unusually hot material near the surface
- Heat from the magma, in turn, heats any groundwater
- his is basis for generating geothermal energy
- The steam and or hot water is used to create electricity or for heating
- Flash plants take super heated water, usually at temperatures over 200°C, out of the ground, allowing it to boil as it rises to the surface, then separates the steam from the water and uses the steam to turn a turbine generator
- In binary plants, the hot water flows through heat exchangers, boiling an organic fluid that spins the turbine
- very high efficiency
- moderate net energy at accessible sites
- lower CO2 emissions than fossil fuels
- low cost at favorable sites
- low land use and disturbance
- Moderate environmental impact
- scarcity of suitable sites
- can be depleted if used to rapidly
- environmental costs not included in market price
- CO2 emissions
- moderate to high local air pollution
- noise and odor
- High cost except at the most concentrated and accessible sources
- Water use for generating hydroelectric power is totally dependent on the available water (duh!!)
- The Glen Canyon Dam in Utah is the classic example of building too big of dam for not enough water
- moderate to high net energy
- high efficiency (80%)
- large untapped potential
- low-cost electricity
- long life span
- no CO2 emissions during operation in temperature areas
- Can provide flood control below dam
- Provides irrigation water
- Reservoir useful for fishing and recreation
- High construction costs
- High environmental impact from flooding land to form a reservoir
- environmental costs not include in market price
- High CO2 emissions from rapid biomass decay in shallow tropical reservoirs danger of collapse
- Uproots people
- Decreases fish harvest below dam
- Decreases flow of natural fertilizer (silt) to land below dam
- All large bodies of water, including the oceans and large lakes, have tides
- Tidal power captures the energy contained in moving water mass due to tides
- You can use the flowing water between low and high tides to generate electricity, similar to hydropower
- Turbines can be place on the ocean floor, for example at the entrance of a bay, where the flowing water can turn the fan to generate electricity
- Another option is to use under water turbines, which is like an underwater wind farm
- This is currently being tested offshore of Scotland’s Orkney Islands
- The ebbing and surging tidal flows turn 100 foot propellers, which each produce 1 megawatts of electricity
- OTEC
- an energy thermal conversion (OTEC) is a new, clean technology that is still in the developmental stage
- The wind is free, commonly available and can provide clean, pollution-free energy
- Today’s wind-turbines are very high tech
- It would take about 1000 one-million watt windmills to equal the energy output of one sizable fossil fuel power plant
- The windmills can be noisy
- And they are hard on migrating birds
- moderate to high net energy yield
- High efficiency
- Moderate capital cost
- Low electricity cost and falling
- Low environmental impact
- quick construction
- easily expanded
- Can be located at sea
- Land below turbines can be used to grow crops or graze livestock
- steady winds needed
- Backup systems needed when winds are low
- Plastic components produced from oil
- environmental costs not included in market price
- high land use for wind farm
- visual pollution
- noise when located near populated areas
- can kill birds and interfere with flights of migratory birds
- Biomass energy is derived from organic matter
- Stoves that burn wood are the classic example
- In fact, there had been a 20-25% increase in the use of wood stoves over the past several decades
- reduced CO2 emissions
- high net energy yield for oil palms crops
- moderate net energy yield for rapeseed crops
- reduced hydrocarbon emissions
- better gas mileage
- potentially renewable
- increases NOx emissions and more smog
- high cost than regular diesel
- environmental costs not included in market price
- low net energy yield for soybean crops
- may compete with growing food on cropland and raise food prices
- loss and dehydration of biodiversity from crop plantations
- can make engines hard to start in cold weather
- high octane
- some reduction in CO2 emissions
- High net energy yield
- reduced CO emissions
- Can be sold as E85 or pure ethanol
- potentially renewable
- lower driving range
- low net energy yield
- high CO2 emissions (corn)
- much high cost
- environmental costs not included with growing food and raise food prices
- high NOx emissions and more smog
- Corrosive
- Can make engines hard to start in cold weather