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[report整理] SENEWS-2011-04-25

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[Homework]SENEWS-2011-04-25

homework
This is the VOA Special English Technology report.Solar water heaters are used around the world and are not very difficult to built.The system awe are going to describe is based on the design developed some years ago in the Africa Scan.Since then it has been built and used in many countries.It can heat 70 littres of water to 60 degrees **.It can do this between sunrise and noon on the clear day with average air temperature of 62 degrees **.
Their are too parts to the solar water heater.One part is made of the sheet of metal painted black.Black surfaces become hotter in the sun than surfaces painted any other courlor.This black metal plate is called a collector.The collector is placed in contact with the water.Their are sveral kinds of metal sheets that can be used for the collector.** metal will work very well.Coveragated sheets are often used as roofs on house.Once the water is heated,it is cant hot within serlation materal.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 storage tank can be a container that holds about 100 littres.2 rubber pumps are retouch to water storage tech.1 pump let water flow into the system.The other lets water flow out.When the water heator 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 of the flow of water so that the temperature is hold were warmed as desired.This solar water heater is easy to built and operat.It release about 2 years before the rubber pumps need to be replaced.There is also something else you will need to make the solar water heater work ,the sun.As you maight imagin, the heater will heat water only on sunny days.
You can get more information about solar water heaters and other project from interprise works **.This group works internationally to fight property.The website is interpriseworks.org.Choose the link for news and resources then collect on pubilications.And thats the VOA Special English Technology report.Tell us,if you ever built the solar water heater or have ideas for improvements.Post your comments at voaspecialenglish.com,where you can also find transcripts,mp3s and portcasts about programs.We also offer english teaching activities in the classroom section of our site.Im Steve Ember.

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