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Harness the sun and power up

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Springtime in Hong Kong marks the start of an eight-month battle between your air-conditioner and the sun. Your air-conditioner usually wins, leaving you to pick up the power bill.

But why not turn the sun's rays into fuel rather than a furnace? Every year, 1,000 sq km of Hong Kong soaks up 2.2 billion megawatt-hours (MWh) of clean energy - from the sun. Last year, the city chewed its way through 42 million MWh, just 2 per cent of the solar energy supply.

Until recently, high costs meant solar power was restricted to niche applications such as remote transmission aerials and lighthouses, or experimental units. But the price of solar generating systems has fallen substantially.

Many developed nations, especially Japan, Germany and the US, have programmes to encourage the use of renewable resources. Farmers sell power from windmills or biomass generators, while factories use waste heat to drive turbines.

Households can install photovoltaic (PV) panels on their roofs. They can sell any surplus, often produced when homes are empty, to their utility company.

Utilities buying power from small-scale generators and customers is known as distributed generation and is used in many developed countries and at least one developing one, Thailand.

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