Wind Turbines

What it looks like

A solar heating system is made up of a number of components, both internally and externally. These components are common to all systems, whether it is a domestic system or a large commercial system.

Below gives an overview of the main components you are likely to see.

Evacuated Tube Collector

Evacuated tube collectors are made up of a number of tubes, depending on the size of the system and the size of the panel. Each glass tube is a vacuum, thus retaining the heat absorbed and improving its efficiency. As such, it is widely accepted that evacuated tube collectors are more efficient than flat plate collectors.

In order to gain maximum performance, it needs to be positioned as southerly facing as possible, pitched between 30 – 50 degrees, with minimum over-shadowing.

The modules are usually installed on a sloping roof or mounted on an “a-frame” in the case of flat roofs. However, it is also possible to install on a “stand-alone” structure which can be orientated and pitched to optimise performance.

Click here download technical specification (PDF)

Flat Plate Collector

Flat plate collectors use a simpler technology to evacuated tube collectors. They are based on a thin absorber sheet that transfers the sun’s energy to a fluid tubing system. The absorber is usually copper and the fluid tubing system is insulated to reduce the energy loss. Fluid is then circulated through tubing, absorbing the energy and transferring this to the heat exchanger.

The insulation case ensures that the heat loss from the collector is minimal, offering efficiencies of 75-80%.

The transparent cover, usually toughened glass, protects against weather damage and minimises heat loss from windy conditions

Twin Coil Cylinder

This is the cheapest and simplest form of cylinder and the most common found in domestic systems. The energy from the modules is transferred via a finned coil at the bottom of the tank. There is also another coil towards the top of the tank to be connected to the boiler, hence “Twin coil”.

A twin coil cylinder can either be open-vented, where a cold water store is required in the roof space, or pressurised, where the cylinder is being fed by the incoming mains.

A pressurised twin coil cylinder is more expensive than an open-vented cylinder, but may improve the flow water of the system, enhancing it’s performance. It is a requirement for pressuirsed systems to be installed by an engineer qualified in pressurized systems and be annually maintained.

Twin coiled systems start around 160 ltrs for domestic systems, but can be much large for bigger commercial size systems.

Thermal Store

More advanced than a Twin coiled system, a thermal store is again more suited to domestic or small / medium sized commercial systems. The solar energy is transferred from the solar modules in the same way, via a finned heat exchanger coil at the bottom of the store. However, a thermal store normally has additional heat exchangers to accept additional heat sources, such as gas boilers, wood burner and heat pumps. The hot water is also run through a heat exchanger to provide mains-pressure hot water, similar to a pressurised twin-coil cylinder. It is also possible to link a thermal store into existing heating systems, both underfloor and radiators. As such, energy from renewable sources can contriute towards heating the house.

The benefit of a thermal store is that the energy from the solar panels can be stored at a higher temperature, therefore increasing their efficiency.

Pre-heaters / Heat Exchangers

For larger hot water users, such as hospitals, nursing homes or the food industry, solar thermal systems can be incorporated using a heat exchanger or a “pre-heater”. The benefit of this is that it can be incorporated into existing systems without the need to replace the califiyer. If the system is run on a pumped secondary return loop, a heat exchanger can be installed on the return prior to being heated. The heat exchanger, which is linked to the solar modules, will then heat up the water before being topped up by the boiler.

Solar Controller

The solar controller is the brains of a solar thermal system. It measures the temperature of the collectors and compares this with the temperature of the store. If the collectors are hotter than the store, it turns on the pumping station. Once the store is the same temperature as the collectors it stops the pumping station. There is additional functionality that can be incorprated and controlled by the controller and could be used in conjunction with other heat requirements such as a swimming pool or central heating.

Pumping Station

A puming station works in conjuntion with the control unit. When the control unit detects that there is energy available from the collectors it switches on the pumping station to pump the energy from the collectors to the hot water store.

Safety Features

There are a number of components and functionalities that are incorporated within a solar thermal system to ensure that it runs efficiently and safely. These incluced the solar controller, a pressure relief valve and expansion vessel.

The solar controller constantly monitors the system and tells the pumping station when to turn on and off. Once the cylinder / store is up to temperature, the controller will not turn on the pumping station so the store will not over heat.

If the store is up to temperature, the expansion vessel is used to regulate the pressure within the system. Should the pressure within the system expand beyond the regulation of the expansion vessel, the pressure relief value will reduce this by releasing some of the heat transfer fluid.

A well designed solar thermal system will mean that this occurance will be minimum.

 
All enquiries   tel: 0844 800 3353   email: sales@greenheart.co.uk
The Solar Trade Association