Solar Thermal (Solar Hot Water)

Exothermic Installations Ltd - Installation and maintenance of solar thermal systems in the Swindon, Newbury and surrounding areas.

There are basically 3 types of Solar panel, Flat Plate, Direct Flow, Evacuated tube.

Flat Plate


As its name suggest, its a flat panel, comprising of loops of pipework in an insulated frame with a glass cover. They can be sited on a roof above the tiles, or in the tiles like a Velux window, or mounted on a frame on a flat roof, or at ground level. A heat transfer fluid within the panel pipework is heated by solar radiation, it is then pumped through a coil in a special twin coil cylinder where it transfers its heat to the stored water. It is then pumped back to the panel to be reheated. The whole process is controlled by a solar controller that only circulates fluid when there is sufficient solar gain. The panels are robust and heavy and less efficient by comparison to other panels.

Direct Flow


A Panel comprising of a manifold with several large glass tubes. Within the glass tubes there are smaller copper or glass capillary tubes to allow the flow in and out of heat transfer fluid within the main tube. As the pump forces the fluid through the capillaries they gain heat from the suns radiation, they are pumped back through the manifold to the twin coil cylinder to heat the water. As they have a forced flow, they are very versatile in their installation. They can be fitted vertically or horizontally on a roof or a wall or a freestanding frame. They are lighter and more efficient than flat plates, so use a smaller overall area to generate required heat.

Evacuated Tubes


A panel comprising of a manifold with several glass vacuum tubes. Within these vacuum tubes are specially coated copper conductors which get heated by solar radiation. Within the conductors there is a liquid. As it is heated it turns to vapour and rises up the conductor capillary to a phial located at its top. This phial sits within the manifold. As heat transfer fluid within the manifold is passed over the phial, it conducts the heat and transports it to the solar coil within the twin coil cylinder, to heat the water. The vapour within the phial condenses back to liquid, sinks back down the conductor, where it is reheated and the process begins again. Evacuated tubes are very efficient and also versatile in their installation. They can be fitted vertically or horizontally on a roof or a wall or a freestanding frame. They are light, efficient and use a minimal area to generate required heat.


In general - all panels need to be installed in conjunction with a suitably sized twin coil cylinder. These can be open vented, unvented or thermal stores. They are usually about twice the size of a standard cylinder. Domestic Solar cylinders vary between about 170 - 300 litre in size. The lower coil is heated via the Solar Thermal system and the top coil by the boiler or heat pump.

Solar Thermal Installation costs and benefits

The average installation is approximately £4000 - £7000 installed and cost are affected by type and size of panels chosen, location of panels, roof construction and the condition of the existing plumbing and heating system - which is normally the biggest variable. If sized correctly they will provide 50% - 60% of total annual hot water heat requirement.This reduces household fuel costs and cuts carbon emissions, saving money and the environment. It can give a property a higher score on its energy performance rating and help achieve a higher level on the code for sustainable homes.
Our Best advice is that you should ALWAYS improve your boiler or heat source and upgrade your system controls and insulation BEFORE you consider installing Solar Thermal (also known as solar hot water). We believe it should be mandatory! You can always Install a solar cylinder and bolt on a Solar Thermal system at a later date! Investing in a Solar Thermal system is a long term investment. Always buy the best you can afford. Quality doesn't cost - It pays! Get in touch today to see how we can help you with installation or maintenance of your Solar Thermal system
Average cost savings for a family with an already highly efficient condensing Gas or Oil boiler is - Approximate annual hot water heating energy requirement 3000kWh. Saving 50% = 1500kWh. But requires burning 1666kWh of gas or oil as boiler is only 90% efficient.

So 1666kWh x (approx cost of gas) 4.5p/kWh = £74.97 saved per annum

So 1666kWh x (approx cost of Oil) 6.5p/kWh = £108.29 saver per annum

What about Carbon Savings?

The forgotten part is the annual Carbon saving of approximately (based on 50% hot water saving)
For Gas is 1666kWh x 0.183kg CO2/kWh = 306.52kg CO2 saved per annum.
For Oil is 1666kWh x 0.246kg CO2/kWh = 409.83kg CO2 saved per annum.
Further yield increases, Carbon savings and financial benefits can be achieved by upgrading the system specification and reducing hot water consumption.
Please note that this is a very conservative figure for a family with a modern boiler system and low cost fuel. Those with old boilers and Oil or Electric heating will have greater savings and Carbon reductions as there is a greater inefficiency in old boilers and a higher amount of CO2/kg per kWh for Oil and Grid Electricity. Thats why you should ALWAYS upgrade your boiler source or even change fuel source and boiler type first.

Qualified and experienced Solar Thermal Installers

We provide a complete installation service from start to finish, as experienced solar installers and as Registered Heating Professionals (RHP) and Registered Plumbers (RP) with the Chartered Institute of Plumbing and Heating Engineers (CIPHE). We take on full responsibility for the design, supply, Installation, set to work, commissioning, handover and maintenance of Solar Thermal systems. We are fully Insured and guarantee all our work, parts and labour for at least 12 months.
Solar Thermal systems are deemed a "a controlled service" in the building regulations (law) and as such can only be legally fitted by those who are legally competent and registered to be able to certify and notify the installation. For more information on this please visit our Competency page

If you're interested in solar thermal installation or maintenance in the Swindon, Newbury and the surrounding areas, Call us today to see how we can help you!

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