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[report整理] SENEWS-2011-04-25

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HW:
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 the design developed some years ago in Afghanistan.
Since then, it has been built and used in many countries.
It can heat 70 litters of water to 60 degrees Celsius
It can do this between sunrise and noon on a clear day with average air temperature of 32 degrees Celsius.
There are two parts of the solar water heater.
One part is made of sheet of metal painted black.
Black surfaces become hotter in the sun than surfaces painted in the other color.
This black metal clit is called a collector.
The collector is placed in contact with the water.
There are several kinds of metal sheets that can be used for the collector.
Corigated metal will work very well.
corigated sheets are often used as roofs on the housing.
Once the water is heated, it is kept hot with isolation 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 storage tank can be a container that holds about 100 litters.
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 2 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 enterprise works vital
This group works internationally to find 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 have ideas for improvements.
Post your comments at voaspecialenglish.com where you can also find transcripts, mp3s and podcasts about programs.
We also offer English teaching activities in the classroom section about our site.
I'm Steven M*.
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