fixmyplumbing

What Are The Components of a Solar Thermal System?

What makes up a solar thermal system?

The components of a solar thermal system are:

Hot water storage tank (cylinder).
Control panel.
Solar collector panel (normally on the roof).
Solar fluid (glycol).
Pumping station.
Temperature sensor in collector panel
Temperature sensor in hot water tank (cylinder).
Expansion vessel
Container for any release of solar fluid
Pipework.
Overheat thermostat for unvented cylinders.

Hot water storage tank (cylinder).

The hot water cylinder used in solar thermal is different to most normal cylinders.

A normal cylinder has a single coil that is heated by the boiler.

Solar thermal cylinders have two coils. The first is heated by the boiler. The second is heated just by the solar thermal system.

A solar hot water tank from Viridian solar.

The upper coil is fed by the boiler. As water is heated by convection the boiler can only heat the volume above the coil.

The lower coil is connected to the solar system. This is at the bottom of the cylinder so the solar thermal can heat the entire volume.

The volume below the boiler coil is called the “solar dedicated volume”. This must be either 80% of the properties hot water demand or 25L per sq m of solar panel area.

Solar dedicated volume is an important part of the install. It gives the solar thermal panels somewhere to heat up if the boiler has already heated the tank up.

This helps reduce the impact of not using the system in the most efficient way.

Control panel.

The control panel is the brains of the system. It senses the temperatures and decides when the pump should run.

Solar collector panel (normally on the roof).

There are two types of solar collector:

Flat panel
Evacuated tubes

Solar fluid (glycol).

As the solar thermal panels are constantly outside they must withstand cold conditions.

Instead of water the panels and pipework are filled with a specific type of antifreeze.

Pumping station.

The pumping station is used to circulate the solar fluid around the panels and hot water cylinder.

Temperature sensor in collector panel

This tells the control panel how hot the collector panel is in the solar thermal system.

Temperature sensor in hot water tank (cylinder).

This tells the control panel the temperature in the hot water cylinder.

Expansion vessel

All fluid expand as they heat up. As solar thermal systems are normally sealed there has to be somewhere for the expansion to go.

Container for any release of solar fluid

If the pressure inside the solar thermal system gets too high a safety valve automatically opens. As solar fluid can be harmful it is recommended to catch any released by the safety valve.

Pipework.

The pipework carries the heat from the panel to the hot water cylinder. It is normally 22mm and has to be properly insulated and supported.

The temperature of solar thermal systems can be higher than normal. This means some methods of connecting pipes are not recommended. It also means that the pipework has to be properly supported with metal clips. Plastic clips melt on solar thermal systems.

Overheat thermostat for unvented cylinders.

Unvented cylinders must have controls to prevent overheating. Solar thermal systems must have a dedicated overheat thermostat if using an unvented hot water cylinder.

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