Solar Thermal/Hot Water

Reliable heating and return on investment are central to our specification

Solar hot water (SHW) systems are the most suitable solar thermal application in the UK, as our climate doesn't generally support solar space heating. Perpetual Energy SHW systems offer the following opportunities:

• Significant carbon saving benefits in the production of hot water that can often meet planning requirements for renewable energy in new build projects
• Can usually be retro-fitted to hot water systems in existing buildings
• Relatively fast return on investment
• Highly visible technology that demonstrates corporate environmental responsibility to staff and members of the public

Perpetual Energy can offer specialist design services that ensure the SHW systems we deliver:

• Integrate reliably with existing or back-up hot water systems to provide a constant service
• Have a high energy output-to-cost ratio for a rapid return on investment
• Are designed using sophisticated modelling software to ensure a good output-to-demand ratio
• Are reliable in operation - we specialise in designing the 'vapour tolerant' systems recently developed in Germany that operate reliably under all conditions
• Meet the highest standards of temperature and bacterial safety
• Give long service life with low maintenance costs
• Use materials that meet the highest environmental standards

In this and other renewable solutions, Perpetual Energy's USP is our in-depth knowledge of the technology. Our team's experience has led to membership of the British Standards Institute's technical committee for solar thermal, and inspecting duties for the DTI's grant scheme as expert witnesses. It is specialist know-how that drives our projects from feasibility through detailed design to construction, and it also underpins our long-term maintenance packages.

Equally, Perpetual Energy is adept at accurately modelling cost and carbon savings and designing systems for maximum benefit. Our economic models can also include an investment appraisal that's specific to your business.

The bottom line is that most commercial buildings will benefit from a SHW system, particularly if hot water demand is high.

Please contact us if you would like to discuss your ideas - initial consultations are free. We would be happy to offer our experience and knowledge, to help establish if your organisation can benefit from this technology.

Solar thermal technology: how it works

It's surprising just how much solar energy is available in the UK. Even with cloud cover, useful solar energy is present; in fact this 'diffuse radiation' comprises 50% of the UK's solar resource.

Modern solar collectors (solar panels) are designed to collect both direct and diffuse radiation very efficiently. The differences between summer and winter are of course reflected in the output of the system, with around 70% of output occurring in the summer months.

This seasonal difference requires careful matching of system output to hot water use. If well designed, a system can meet 50-70% of hot water requirements (averaged over the year).

The type of collector used is usually dictated by nature of the roof or other structure that the collectors will be mounted on:

• Evacuated tube collectors offer greater efficiency than flat plate collectors - therefore less space is needed. This can be an important consideration on roof sites where space may be limited
• Flat plate collectors cost less and may offer greater reliability and so are favoured by Perpetual Energy for larger systems

The entire system must be designed to handle the maximum temperature that can be generated by the collectors - this can be in excess of 300°C. Just as importantly, the system must be able to guarantee safe temperatures for users.

Assuring long term reliability and return on investment in thermal systems is all about attention to detail - the system control strategy and how to retain vapour when at maximum temperatures has to be comprehensively thought through.