Understanding Solar EnergySunlight can be used to create heat or generate electrical power. This is referred to as solar energy. It is a clean form of energy production, which doesn't pollute the environment. There are two forms of solar energy: 1. The first is solar thermal conversion, which uses sunlight to create heat. 2. The second is photovoltaic conversion, which uses sheets of special materials to create electricity from the sun. Photo- means "light," and voltaic means "producing electricity." Solar Thermal Conversion A technology for harnessing solar energy for thermal energy (heat). Solar Thermal Systems Evacuated Tube Collectors These collectors are very efficient and can achieve very high temperatures. They contain several rows of parallel transparent glass tubes each containing an absorber tube which are connected to a heater pipe. Each tube has the air removed from it (evacuated) to eliminate any heat loss through convection and radiation. Inside the glass tubes, a flat or curved aluminum or copper fin is attached to a metal pipe. The fin is covered with a selective coating that transfers heat to the fluid that is circulating through the pipe. There are two types of evacuated tube collectors: Direct-flow evacuated-tube collectors and Heat pipe evacuated-tube collectors. We will concentrate on the Heat pipe evacuated-tube collectors. Heat Pipe Evacuated-Tube Collectors Heat pipe evacuated tube collectors contain a copper heat pipe, which is attached to an absorber plate, inside a vacuum sealed solar tube. The heat pipe is hollow and the space inside is also evacuated. Inside the heat pipe is a small quantity of liquid, such as alcohol or purified water plus special additives. The vacuum enables the liquid to boil at lower temperatures than it would at normal atmospheric pressure. When sunlight falls the surface of the absorber, the liquid in the heat tube quickly turns to hot vapor and rises to the top of the pipe. Water or glycol, flows through a manifold and picks up the heat. The fluid in the heat pipe condenses and flows back down the tube. This process continues, as long as the sun shines. They have a number of significant advantages: · The collector remains heating in cloudy conditions and low temperatures. · The circular tubes mean that the sun shining directly on the absorber for most of the day. · Evacuated-tube collectors have the ability to heat water to heat water much faster than flat plate collectors. · Evacuated-tubes can be added or removed as easily without the need to drain the system.
Other Main Components The other main components of a solar thermal system are the hot water storage tank, regulation and safety controls. Some systems come with all components integrated, such as the gravity drain system. Why use a solar thermal water heater? · To save money, to avoid pollution and to guarantee future energy costs. · To use renewable energy in a visible manner. · To be seen as environmentally conscious. · To satisfy laws mandating the use of renewable energy.
What is the difference between flat plates and evacuated tubes? Older style flat plates with water tubes attached to the metal were the first active systems. Flat plate collectors do not perform well in cold climates. Newer technology evacuated tubes have higher efficiency, no heat loss across a vacuum and quasi-tracking of the sun because some part of the round tube is always directly facing the sun. As cost is now almost equal, vacuum tubes are supplementing the older style flat plates. Also, the ambient air temperature has little affect on the performance of the evacuated tubes. |
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Learn About |
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Solar Energy Works |
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Renewable Energy Products |
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902.315.0754 |
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Specializing in Solar Boilers |
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For more information call Grant MacDonald 902.315.0754 Email : info@solarenergyworks.ca |
