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[report整理] SENEWS-2011-04-25

提高英语听力能力 找对方法很重要!

[Homework]SENEWS-2011-04-25

this is the voa special english technology report. solar water heaters are used around the world and are not very difficult to build. the system we are going to describe is based on a design developed a few years ago in afghanistan. since then, it has been built and used in many countries. it can heat 70 meters of water to 60 degrees celsius. it can do this between sunrise and noon on a clear day with an average air temperature of 32 degrees celsius. there are two parts to the solar water heater. one part is made of a sheet of metal painted black. black services become the potter in the sun and services painted in any other color. this black metal part is called a collector. the collector is placed in contact with the water. there are several kinds of metal can be used for the collector. corrugated metal will work very well. corrugated sheets are often used as roofs on the housing. once the water is heated, it's kept apart with insulation material. this allows the water to stay warm all the time. the second part of solar water heater holds the water for the system. this storage tank can be a container that holds about 100 meters. two rubber pipes are attached to the water storage tank. one pipe lets water flow into the system; the other lets water flow out. when the water heater is working correctly, water will flow from the storage 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 desired. this solar water heater is easy to build and operate. it will last about two years before the rubber pipes need to be replaced. there is also something else you will need to make the solar water heater work--the sun. as you might imagine, the heater will heat water only on sunny days. you can get more information about solar water heaters and other projects from enterprises works provider. this group works internationally to fight poverty. the website is enterprisesworks.com. 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 the solar water heater, or have ideas for improvements. post your comments at voaspecialenglish.com, where you can also find transcripts, mp3s and podcast of our programmes. we also offer english teaching activities in the classroom section of our website. i'm steve vemble.
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