is the VOA Special English Development Report.
water heaters are devices that use energy from the sun to heat water. Solar
water heating is used around the world.
solar water heater described here is based on a design developed some years ago
in Afghanistan. Since then, it has been built and used in many countries. It
can heat seventy liters of water to sixty degrees Celsius. It can do this
between sunrise and noon on a clear day with an average outside temperature of
thirty-two degrees Celsius.
are two parts to the solar water heater. One part is made of a sheet of metal
painted black. This metal surface, placed in contact with the water, will heat
the water. Black-painted surfaces that receive the sun's heat become hotter
than surfaces of any other color.
black metal plate is called a collector. There are several kinds of metal
sheets that can be used for the collector. Metal sheets that have raised
sections will work very well. These corrugated sheets often are used to make
the roofs of houses.
Once the water is heated, it is kept hot with material called
insulation. This allows the water to stay warm for a long time.
second part of the solar water heater holds the water for the system. This
storage tank can be a container that holds about one hundred liters. 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.
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
expect, the heater will heat water only on sunny days.
can get more information about projects like solar water heaters from
EnterpriseWorks/VITA. This nonprofit group works to fights poverty in many
countries. The Web site is enterpriseworks.org. Choose the link for News &
Resources, then click on Publications.
MP3s and podcasts of our reports are at voaspecialenglish.com.
that's the VOA Special English Development Report. I'm Steve Ember.