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[report整理] SENEWS-2011-04-25

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[Homework]【整理】SENEWS-2011-04-25

this is the VOA Special English Techonology Report,solar water heaters are used around the world and not very difficult to build,the system we are going to describe is based on the design developed some years ago in Afhanstan,since then,it has been built and used in many countries,it can heat 70 litters of water to 60 degrees s     ,it can do this between sunrise and noon on a clear day with an average air temperature of 32 degrees s   ,there are two parts of the solar water heaters,one part is made of a sheet of a metal painted black,black surfaces become hotter in the sun than surfaces painted in other colours,this black metal plate is called a collector,the collector is placed in contact with the water,there are several kinds of sheets metal that can be used for the collector,corrigated metal will work very well,corrigated sheets are often used as roofs on housing,once the water is heated,it is kept hot with inserlation material,this allows the water to stay warm for a long time,the second part of the solar water heater holds the water for the system,this storege tank can be a container that holds about one hundred litters, two rappered pipes are attached to the water's storege tank,one pipe let the water flow into the system,the other let the water flow out,when the water heater is working correctly,the water will flow from the storege tank to the collector and back again,you can use the hot water at the top of the tank for washing and cleaning,you can change the flow of water so that the temperature is hot or warm as you desire,this solar water heater is easily to build and operate,it will last about two years before the rapper pipes need to be replaced,there is also something else you need to make the solar water heater work,the sun,as you might imagine,the heater will heat the water only on sunny days,you can get more informations about solar water heaters and other projects from enterprise works viter,these groups works internationally to fight poverty,the website is enterpriseworks.org,choose the link for news and resources then click on publications,and that's the VOA Special English Technology report.tell us if you ever build a solar water heater or if have any ideas for improvement,put your comments at voaspecialenglish.com.
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