How solar thermal systems work

Solar collectors harvest solar energy from the sun and transfer the heat into the cool water in the storage tank. This means the cold water entering your boiler requires less heat to bring it up to temperature, or often none at all as it is already hot enough for normal use. This reduces the amount of fuel needed to heat the water for your home by 50-60%, and helps save the environment by reducing nasty greenhouse gas (CO2) emissions. An illustration of a conventional solar hot water system is shown below.

How a solar thermal system works

There are two primary types of solar collectors, flat solar panels and evacuated tubes.

Flat plate solar collectors

Flat solar panel systems use a special metal surface under a layer of glass to transfer absorbed heat into water within pipes inside the collector, which is then circulated around the hot water storage tank. Since the collectors are outdoors and contain water, anti-freeze solution (glycol) is required in the water to prevent freezing.

Evacuated tube collectors

The Atmos Ephesus has 24 tubes, and each tube comprises an outer tube and an inner heat pipe, with a vacuum in between just like a thermos flask. A special selective coating on the outer surface of the inner tube absorbs solar radiation,  which causes the small volume of liquid inside to change into a hot gas which rises up the tube to the water tank. The hot gas then transfers its heat into the water, which then turns back into a liquid and runs back down the tube to collect more solar heat. The fluid in the tube is a very small volume, so the tubes will never break due to freezing weather. Evacuated tube systems are suited to cooler climates like the UK where there is a larger difference in the outside temperature and the hot water temperature.

In a conventional system as illustrated above, the solar station includes a circulation pump which pumps glycol fluid to transfer the solar heat to the hot water tank. The Atmos Ephesus 24 heats water directly which eliminates the need for a transfer circuit containing glycol and eliminates the need for a pump, which saves expensive electrical energy and makes the system simple to install and care for.

The solar storage tank wrapped in a highly advanced insulation in a white case to keep heat loss to an absolute minimum. An integrated thermostat on the pipework keeps an eye on the weather, and if the temperature of the insulated cold and hot water connecting pipes drop below 5 degrees C, a 12-volt pump operates briefly to send warm water through the pipes to keep them from freezing, and also to protect the tank from frost. An electric immersion heater is fitted on all Atmos Ephesus 24 tanks to provide back up heat where there is no other form of back up heat.

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