Solar air Heaters can be made easily at home with recyclable materials. In this article, we will try to explain what are the best practices for making efficient solar air heaters.
Solar Air Heaters are a very cost effective way of achieving heating and ventilation. With so many packaging materials ending up in waste it is very easy to make a solar air heater almost free of cost.
To make a heater that is efficient, one has to understand the mechanism, which we will try to explain in this article.
There are many designs for solar air heaters available on the internet. Many of them employ used tin cans for creating absorber pipes. The advantage of tin cans is firstly they are readily available and secondly, their wall thickness is small. This means that the air inside can get hot efficiently. There are three basic components of a solar air heater. They are the absorber, transparent cover and the enclosure.
The absorber needs to be of dark colour to soak up most of the radiation it receives. You can use matt black spray paint for this purpose. A shiny black paint will have a tendency to reflect part of the radiation. The layer of paint needs to be thin otherwise it will become a barrier for heat to flow into the absorber section.
The absorber pipe is usually metallic which allows it to transfer heat effectively to the air on the inside of the pipe. If you have copper tubing lying around, you can make the absorber pipes out of that. You can also place the copper pipe on a metal plate and paint that black to enhance the area of absorber section. The longer the absorber pipes, the more will be the temperature of the air at the outlet.
The second segment of the solar air heater is the transparent cover. The ideal choice for the transparent cover is the low iron glass. This type of glass allows most of the radiation through and is everlasting (unless broken). One can also use transparent plastic sheet or plexiglass. However, plastic cover has a tendency of getting hazy overtime. The transparent cover serves two purposes, it allows most solar radiation inside and also blocks heat from getting away through greenhouse effect. Thus it acts as a blanket for the absorber pipes which can get really hot. It has been reported that the distance between the absorber plate and transparent cover should be at around 1 inch for best results.
The enclosure around the absorber pipes provides structural stability and protects the pipes from the elements. It also provides thermal insulation and blocks the heat from escaping through the backside. One can also place a layer of news paper, loft insolation, or any kind of foam in between the enclosure and the absorber pipe to increase the efficacy of the system. For a solar air heater there is a slot cut at the bottom of the enclosure to allow the air to come in. You can also attach an air duct from your house to this inlet of the heater. This is will recirculate the air that was already inside and make it warmer.
The solar air heater works best when placed at the right angle, and in direct sun.
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