Saturday, December 8, 2007

Renewable Energy Sources

Renewable energy systems use resources that are constantly replaced and are usually less polluting. All renewable energy sources – solar energy, hydro power, biomass and wind energy have their origin in activity of the Sun. Geothermal energy which, because of its inexhaustible potential, is sometimes considered as renewable source is getting energy from the heat of the earth. In using each of renewable sources have advantages as well as disadvantages. Table below resume generally advantages and disadvantages of some renewable energy resources.

Renewable energy is a domestic resource that has the potential to contribute to or provide complete security of energy supply. Countries that depend on imports of fossil fuel resources are in danger due to the risk of sharp rise of the cost of imported energy (mainly oil). This is particularly so for developing countries, where the oil import bill adds every year to the problem of financing an already large external deficit.

Renewables are virtually uninterruptible and is of infinite availability because of its wide spread of complementary technologies - thus fitting well into a policy of diversification of energy supplies. Renewable resources are well-recognized as a good way to protect the economy against price fluctuations and against future environmental costs. Technologies based on renewables are largely pollution-free and make zero or little contribution to the greenhouse effect with its predicted drastic climatic changes. In addition, they produce no nuclear waste and are thus consistent with environmental protection policies, building towards a better environment and sustainable development.

Type of renewable energy

Advantages

Disadvantages

Solar

Always there; no pollution

Low efficiency (5-15%); very high initial costs; lack of adequate storage materials (batteries); high cost to the consumer

Hydro

No pollution; very high efficiency (80%);little waste heat; low cost per kWh; can adjust kWh output to peak loads.

Fish are endangered species; sediment build up and dam failure; changes watershed characteristics; alters hydrological cycle

Geothermal

Very high efficiency; low initial costs since already yields steam

Non-renewable (more is taken out than can be put in by nature); highly local resource

Ocean Thermal Energy Conversion

Enormous energy flows; steady flow for decades; can be used on large scale; exploits natural in the ocean

Enormous engineering effort; extremely high cost; damage to coastal environments

Tidal Energy

Steady source; energy extracted from the potential and kinetic energy of the earth-sun-moon system; can exploit bore tides for maximum efficiency

Low duty cycle due to intermittent tidal flow; huge modification of coastal environment; very high costs for low duty cycle source

Wind

None on large scale; supplemental power in windy areas; best alternative for individual homeowner

Highly variable source; relatively low efficiency (30%); more power than is needed is produced when the wind blows; efficient energy storage is thus required

Hydrogen Burning

No waste products; very high energy density; good for space heating

No naturally occurring sources of hydrogen; needs to be separated from water via electrolysis that takes a lot of energy; hydrogen needs to be liquefied for transport - takes more energy.

Biomass Burning

Biomass waste (wood products, sewage, paper, etc) are natural by products of our society; reuse as an energy source would be good. Definite co-generation possibilities. Maybe practical for individual landowner.

Particulate pollution from biomass burners; transport not possible due to moisture content; unclear if growing biomass just for burning use is energy efficient; large scale facilities are likely impractical.

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