Thermosyphon System for Solar Hot Water

One of your solar hot water options is known as a thermosyphon system. It is a passive system that requires no power, pumps or controls, making it one of the least expensive solar hot water systems. There are several different types of solar hot water systems, differentiated at a number of levels. The first is at the system level. A system can be active or passive. The second is the type of circulation is uses–direct or indirect. The third point of differentiation is the type of solar collector it uses. A thermosyphon solar hot water system is a passive direct system that most often uses a flat plate collector.

Active vs. Passive

Of solar hot water systems, the main difference is between active and passive systems. Active systems use electric powered pumps and controls to move water into the solar collector and back into the storage tank. Passive systems, on the other hand, do not need power to operate. Rather, they rely on the physical properties inherent in water whereby heated water becomes less dense and rises on its own.

Direct vs. Indirect Circulation

Direct circulation refers to the fact that the potable water itself passes through the solar collector directly, heats up and moves to the storage tank for use. Indirect systems use a heat transfer liquid–sometimes water, sometimes oil or refrigerant–to pass through the solar collector. This heat transfer liquid is, in turn pumped to a heat exchanger where it heats the waiting potable water.

Solar Collectors

There are three main types of solar collectors: flat plate, integral collector storage tanks and evacuated tube collectors. Flat plate collectors are the most common, consisting of a large metal plate that absorbs the sun’s energy and transfers it to either water or a heat transfer liquid passing through adjacent pipes. The whole plate is contained in a sealed, insulated box. Integral collector storage tanks are also in a sealed box, but water is essentially pumped into a small tank and is heated in batches before it is moved to the storage tank. Evacuated tube collectors use parallel glass tubes containing solar absorbing metal fins to transfer heat to the passing liquid.

Thermosyphon Systems

As stated, a thermosyphon system is a direct, passive system that will most likely use a flat plate collector. Because it relies on the physical properties of water to move it to the storage tank, the solar collector must be below the tank. As the sun hits the flat plate collector, it heats up the potable water directly. As it heats up, it becomes less dense and rises through piping into the insulate storage tank for use. A thermosyphon solar hot water system is thus one of the least expensive and requires the least amount of maintenance. This is because there are no pumps or control to break down, and it requires no electricity for its operation.

If you are looking for a way to generate solar hot water, consider a thermosyphon system. It is the least expensive means of using the sun to heat water for your home, yet it is effective. There are a few basic requirements to the system, but it is relatively easy to set up and maintain.