How a solar water heater is made

We explain how it is one of the solar systems with better use of the sun

A little history

The solar water heater is one of the most primitive forms of exploitation of solar energy. Its use was first popularized in the ’20s and ’30s in South Miami, due to the high cost of heating the water, because natural gas is not then reached those parts, and coal supply was hampered for access to all households. At the same time, electricity was comparatively the current price, about 8 times more expensive. Which led to a flourishing industry of this technology. See the ad that appeared in the press in the 30s:

Cartel placas solares antiguo

Newspaper Ad of the 30s included in the book: A golden thread: 2500 years of architecture and solar technology, Tutti and John Ken Perlin.

The industry disappeared a few years with cheaper electricity and gas influx strongly comeback from the 90s.

At present only in Europe are installed over 43 million square meters of collectors, with a rate of over 3 million square meters of collectors annual installation, according to data from ESTIF (European Solar Thermal Industry Federation).

How a solar water heater works

The main element of a solar water heater is the solar collector. This allows you to use the sun’s energy to heat a fluid flowing through it.

The general scheme of operation of an installation of a solar water heater is as follows:

Functional diagram of a solar water heater

The collector collects solar energy heating a fluid flowing through it. With this fluid warmed other fluid that allows us to heat water or water directly (depending on configuration). This hot water and optionally there may be a support heater to elevate the temperature needed in case of solar energy is not sufficient at any given moment.

In this general configuration there are many variations, depending on the needs of each project. In small projects exchanger is not used, causing the heated fluid to circulate water within the tank through a coil, so giving up its heat directly to water. In simple domestic installations where you want to minimize maintenance, you opt for computers without recirculation pump of the primary fluid, flowing east by natural circulation; are called thermosyphon.

How a solar collector heats

The principle of operation is based on the maximum absorption of solar radiation and minimal heat emission to the atmosphere captured.

This is achieved thanks to the greenhouse effect. Sunlight passes through a special glass designed to be very permissive to the passage of light, but also prevent the emission of heat through it. This crystal is responsible for causing the greenhouse under it, thus increasing the amount of thermal energy that is drained fluid.

Within the manifold, a network of copper pipe, through which the fluid to be heated, is welded to fins of different materials that cover the whole surface where it can influence the sunlight. The simplest is aluminum painted black, but there are multiple selective treatment can increase the performance of heat absorption. The entire assembly is finished with an insulating case which decreases fluid losses and heat.

Scheme of components of a solar thermal collector

So simple are the basic principles of solar water heater, which permits very robust facilities and a very long life if proper care is given.

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