口语能力标准
英音05: Solar Power
2014-02-24
Which form of energy is free during the day, produces no dangerous waste products and will be available for the next 4 billion years? Solar power, of course.
Here are just some of the things you can do with it, with a bit of simple technology
Cooking
Get a metal box and put some mirrors and a pot inside. Hey presto, you’ve got an oven! The mirrors focus the sunlight onto the pot to cook the food. The temperature can go to at least 200ºC. Somebody first invented a solar oven in Europea few centuries ago. They are very useful these days in places where there is lots of sunlight, likeAfrica. The alternative is to cut down more and more trees to make fires.
Heating water
This is the most common use of solar energy at the moment. It works like this. A system of tubes heats up in contact with sunlight. The tubes go into a tank with water in it. A few hours sunshine will give most houses enough hot water for a whole day. Swimming pools can be heated this way, too.
Lighting
Many shops now sell small lights which collect the sun’s energy during the day using a small solar panel. At night they can illuminate your garden. The lights on a mobile phone work on a similar principle. Recently, a university student used this idea in a common women’s accessory--she invented the solar-powered handbag. When you open it, a light comes on. Now it is much easier to look for your door key when you get home at night.
Operating small devices
If you put a small photovoltaic cell on top of a parking meter, an emergency telephone or a calculator, there is no need to be near an electricity supply. Photovoltaic cells are also used to operate satellites in space. There is a problem--they are expensive because they are made from silicon.
