Magazine article Geographical

The Technologies: When It Comes to Selecting the Best Alternatives Available in the Renewable-Energy Market, Not All of Them Can Be Applied to Every Situation; Each of the Contenders Comes with Its Own Pros and Cons. (Renewable-Energy Special)

Magazine article Geographical

The Technologies: When It Comes to Selecting the Best Alternatives Available in the Renewable-Energy Market, Not All of Them Can Be Applied to Every Situation; Each of the Contenders Comes with Its Own Pros and Cons. (Renewable-Energy Special)

Article excerpt

Solar power--an inexpensive source of off-grid renewable energy

Each day, the Earth is bathed in vast quantities of solar energy; the difficulty lies in harnessing it. At present, the main practical uses for direct sunlight are in heating and electricity production.

Practical solar water heating comes from flat-plate collectors that pump water through a metal panel topped by glass and into a hot-water tank. Home systems can be reasonably cheap and simple to use. Commercial systems are less cost-effective unless they are used for a significant hot-water load such as a swimming pool or laundry.

Solar photovoltaic (SPV) technology originated in the space programme, when NASA needed to develop lightweight power sources for satellites and space vehicles. It's based around silicon and thin-film cells. Rates of conversion of sunlight into electricity have been creeping to beyond 23 per cent in the lab for silicon cells; thin-film efficiencies are much lower but so are production costs. With sustained 35 per cent per annum growth, huge markets in Germany and Japan, subsidy programmes starting elsewhere and great potential in developing countries, the SPV business is looking healthy.

Today, SPV is widely used in parking meters and traffic signs, where the costs of laying electricity cables would be prohibitive. It provides competitively priced off-grid power, where the alternative is a diesel generator. The technology is already competitive in countries such as Kenya, Sri Lanka, Brazil, South Africa and Vietnam. Pioneering companies such as the Solar Electric Light Company provide innovative leasing of solar-powered lighting systems to people in developing countries as an alternative to candles and kerosene. The World Bank has been copying this approach in recent SPV commercialisation programmes in such areas.

Integrating SPV technology into new buildings is a growing trend in North America, Japan and Europe, but on-grid, solar power is still relatively expensive and usually requires subsidies to make it viable. As production increases, however, there should be a significant breakthrough in price, which is why Jerry Leggett, CEO of UK-based Solar Century, describes it as "a subversive technology".

Wind power--aerospace technology tapping into an unlimited resource

Wind power is the most successful of the new renewable technologies. Although the wind has long been used for pumping water, it's through generating electricity that wind power has broken into the mainstream. Modern wind turbines use aerospace technology, are computer controlled and are cheaper than nuclear power on good sites. Wind is now a US$8billion a year industry, growing at 20-25 per cent per annum. European Wind Energy Association boss Corin Millais told an oil and gas conference audience that it was time to stop calling wind power "alternative energy" and accept that it was "now mainstream".

The size of modern wind turbines has been steadily increasing. A few years ago, 750-kilowatt to one-megawatt systems were the norm. Today, 2MW is typical, while 3MW systems are being readied for offshore use. These turbines sit on towers up to 50 metres tall.

Wind farms feed electricity into the grid and can be controlled remotely. …

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