Renewable energy
From Envirowiki
Renewable energy resources may be used directly, such as solar heating or sailing ships, or used to create other more convenient forms of energy such as electricity.
Most renewable energy sources are also clean (and therefore environmentally friendly), in that the energy source produces no or only harmless by-products. One exception is biodiesel, which produces carbon dioxide when burnt, however in this case the carbon dioxide produced is already part of the active biocycle as it was captured from the atmosphere by the vegetation that the biodiesel was produced from. (This is in contrast to fossil fuels, in which the carbon has been removed from the biocycle for millions of years).
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[edit] Global renewable energy
Renewable energy world wide in 2007 was estimated at 240Gigawatts, an increase of 50% in 3 years. Renewable sources represent 5 percent of global power capacity and 3.4 percent of global power generation. Large hydropower is not included in these figures, but generated 15% of global power[1].
[edit] Renewable energy supply
Renewables, unlike coal or nuclear, can be used at any level, depending on the actual technology in question. From the small scale individual installations, to massive producers that feed into the electricity grid. Smaller scale is often better, as it can be situated locally, and thus has a greater efficiency due to reduced transmission loss. Larger scale renewables bought through the grid as green power are sometimes destructive in other ways (such as large dams for hydro)
[edit] Technologies
The table below compares common renewable energy sources. The capacity column refers to the total electrical generation capacity of the source. The utilisation column refers to electrical generation only; some sources are currently also utilised in other ways, such as direct solar heating. For comparison, current total global electricity demand is approximately 1.7 TW [2] (Tera Watts, 1,000,000,000 KW).
| Source | By-products | Capacity (TW) | Utilisation (TW) | Cost (US$/KWh) |
|---|---|---|---|---|
| Wind | None | 72 [2] 1 | 0.06 | $0.06 [3] |
| Solar thermal | None or steam | 366 2 | ~0.002 | $0.06 [4] |
| Photovoltaic (solar cells) | None | |||
| Geothermal | Steam | ? 3 | 0.008 | $0.03 [5] |
| Hydro | None | |||
| Biodiesel | carbon dioxide | |||
| Ocean thermal | None | |||
| Tidal | None | |||
| Wave | None |
[edit] table notes
1 Conservative estimate for current technology for land and near-shore deployment. Off-shore and high-altitude wind turbines can contribute substantially more energy.
2 Conservative estimate assuming 5% land use and 20% efficiency. Current solar thermal electricity technology achieves between 20 and 30% efficiency [6]. Off-shore deployment greatly increases available area.
3 Current technology can reach the deep, hot, dry rock formations of the Earth's crust. As the technology improves the deeper, practically unlimited energy in Earth's magma may be tapped.
According to an report by the Cooperative Research Centre for Coal in Sustainable Development (CCSD), Solar Thermal is the only renewable technology capable of producing australia's entire electricity demand[7]
[edit] Sources
- ↑ REN21 - Renewables 2007 Global Status Report, World Watch. (Executive summary).
- ↑ 2.0 2.1 Archer, Cristina L.; Mark Z. Jacobson. "Evaluation of global wind power"
- ↑ British Wind Energy Association web site, retrieved 2006
- ↑ Global Environment Facility, "Solar Thermal Thematic Review", 2001
- ↑ Geodynamics Limited Australia web site, retrieved 2006.
- ↑ Sandia National Laboratories. "Sandia, Stirling to build solar dish engine power plant." Press release, 2004.
- ↑ Climate of fear silencing scientists when they must be heard, Rosslyn Beeby, Canberra.yourguide.com.au
- Smil, Vaclav. "Energy at the Crossroads"
[edit] dodgy sources
these sources are probably factual to some extent, but may hide data, or misrepresent data, as they have a vested interest (usually monetary) in doing so.
- Renewable Energy and Electricity - Nuclear Issues Briefing Paper 38, Uranium Information Centre.
