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Solar Thermal

Solar Thermal


The Concept


Thermal energy is absorbed by a specially coated heat-absorbent collector panel, which transfers the sun's heat energy to a hot water system.  Thermal energy systems do not require direct sunlight to absorb solar energy making them efficient even on overcast days. Solar thermal systems can be connected to a range of water heating systems from hot water cylinders to swimming pools, reducing fuel bills and reliance on fossil fuels.


Solar thermal systems can provide around 60% of annual hot water, rising to almost 100% during the summer months and falling to nearer 25% during winter.  Suitable for the UK and other sunny climates, these systems are very cost effective.


In addition to a traditional on roof installation, we also offer a unique roof integrated solution that is fitted like a roof light or Dorma window.  Available as a PV or thermal panel these innovative panels are worth considering if roof weight or aesthetics are important to you.


























The Technology


Direct systems divert the actual hot water used by a system through the panel.


Direct systems tend to only work with vented hot water cylinders and connect to the existing pipe work. This has the advantage of not requiring the replacement of the hot water plumbing.


Indirect systems pump solar-heated fluid round a closed circuit.  They heat water via a coil in a hot water cylinder or similar system.


Indirect systems rely on circulating heat via a dedicated solar coil in the hot water cylinder. This circulation is powered by a small electric pump triggered by temperature sensors. These sensors ensure that the fluid only circulates when it is beneficial to do so.  You may need to replace the hot water system with a solar compatible one.


Pressurised indirect systems connect to rectangular flat plate panels or vacuum tubes and can start collecting energy at very low inputs from the sun by modulating the circulation rate down to 30%.


Flat-plated designs are highly insulated and have a copper absorber plate beneath a transparent cover, which reduces heat loss. The solar heat is transferred to a series of pipes containing an anti-freeze solution, which becomes heated and circulates in the system. Flat plate panels must be mounted on a pitched surface or A-frames.


Vacuum tubes


The evacuated tube collectors consist of rows of parallel transparent glass tubes, each containing an absorber plate. As sunlight strikes the absorber, heat is transferred to fluid flowing through pipes in the glass tubes. The vacuum tubes guarantee highly effective thermal insulation and thus lose less heat by convection making them more efficient than some flat plate designs.  They can supply more energy per square meter, especially in colder weather.  Vacuum tubes may also be positioned horizontally on flat roof tops but with each tube angled optimally towards the sun.


Central Heating


It is possible to make a contribution to central heating from solar energy although our general advice is to concentrate purely on hot water preparation.


Orientation and Positioning


The positioning of solar panels is similar to that of PV panels.  However, the degree of offset from due South is not as critical.  The panel is usually positioned on top of existing roof tiles or it may be integrated into the roof within 45 degrees of due South to provide a significant contribution to hot water demand and angled at 45 degrees from the horizontal.  An A-frame may be constructed to set the panel at the correct angle on flat roof tops or, with vacuum tubes, each tube may be laid horizontal but with the collector tilted optimally towards the sun.




Virtually maintenance free once installed, although some customers choose to have an annual service for peace of mind. With conventional indirect systems the only service requirement is to change the circulation fluid every five to six years.


Renewable Heat Incentive and Premium Payments both apply to this technology. Energy Savings Trust loans are also available. For more information on funding please click here.




Contact our team on 0121 241 5250 or email: to discuss the implications for your system


KM Renewable Energy UK

Renewable Energy, Prefab Construction,

Energy Efficiency & Finance

25 Lee Bank Business Centre

Holloway Head


B1 1HP

0121 241 5250


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