Getting the best from solar thermal
Solar thermal is an accepted part of the micro-generation market — but how do you get the best from it? Paul Honeyman offers his advice.
Solar thermal has come a long way in a very short space of time. Only five years ago it was still seen as in the realm of the energy-conservation enthusiast and not destined for the UK mass market. After a succession of increases in the price of gas and electricity prices and a series of Government and political motivations to make it happen, solar thermal has now began to be considered in a new light.
Everyone really is taking solar thermal very seriously as a viable addition to conventional heating fuels. A well designed system-based solution should be able to contribute up to 60% of an annual domestic-hot-water bill.
It is not too extravagant to claim that solar thermal has entered the mainstream of commercial and domestic heating systems. Consumers, contractors, developers and local authorities are all convinced by the proposition of solar thermal solutions as viable and cost effective — especially in today’s economic climate.
The Government has played a major part in this acceptance. The much mooted ‘Code for sustainable homes’ sets out some ambitious targets for pushing the residential market along a much greener pathway. Contractors have been quick to grasp the potential of this new and fast developing market as a way of increasing their skills base and their own portfolio of services to differentiate them from competitors.
But there is one point of caution. Because the solar thermal market is still developing, almost on a daily basis, there are fewer acknowledged and widespread benchmarks of quality. Dedicated installation teams appear to be gaining most of this new business area. But there needs to be close attention paid to the supply side of the industry for solar thermal products and components.
Many small fringe companies from all over Europe and the world are supplying products to the UK as we embrace this new era of micro-generation solutions. Contractors and developers need to be cautious. Integrated systems comprising solar collectors, pump station, twin-coil cylinders and, especially, the controls, all need to work together in harmony. ‘Simple’ is clearly the best solution.
One supplier should be the single point of supply, information and delivery. Another thing to remember is that just one point of contact will include any warranty issues or delivery problems.
For a contractor there are stark and clear advantages of having one simple supply route for all component parts. One supplier, after appraisal, should be able to offer one single delivery and just one point of contact. Who wants a logistical and administrative nightmare of solar collectors supplied from one source and the cylinder from another?
All components that make up the system will be designed to work as an integrated system. For example, intelligent controls can hold off a boiler when solar energy is available, despite the boiler being timed as being ‘on’, to maximise on efficiency and the solar yield. More importantly, the approval of the system as a whole will rely on all component parts of a given system being utilised.
There will be no issues with chasing round trying to find parts to adapt a seemingly cheaper cylinder to accommodate the solar components that it is clearly not designed to accept.
All safety devices should be included when sourcing from a single, approved supplier — such as an adequately sized expansion vessel and protection vessel for the solar circuit.
Requirements for unvented storage water heating systems and their installation are laid down in Part G3 of the UK Building Regulations. Thy state that unvented hot water storage systems with a storage capacity greater than 15 litres must be safely installed by a ‘competent person’ who holds a current Registered Operative Identity Card.
The card can be obtained by attending a CITB (Construction Industry Training Board), BPEC (British Plumbing Employers Council), European Registration Scheme or BPEC Certification approved training course. Unvented training is available through colleges and manufacturers, who may be able to combine this with product-specific training.
Guidance on system design and sizing can be sought from the Domestic Heating Compliance guide. Using this guide, in conjunction with Part L energy-efficiency training, installers and specifiers can be sure that the solar coil is adequately sized, that the solar cylinder has adequate volume to maximise solar gain and that the cylinder is properly insulated.
With a fully approved solar system and cylinder, much of this work is taken care of by the manufacturer. Provided the installer makes necessary provision to counter solar shaded areas, takes account of roof orientation where a perfectly south- facing roof is not available and sizes the system for the needs of the application, the integrated system approach offers as near a ‘plug-in-and-play’ solution as you are likely to find.
Most of the established manufacturers have complete and integrated systems, and they are usually backed up by a nationwide service organization or network should any issues arise. There are huge ‘solar’ gains to be made, but integrated systems, all from one manufacturer, are obviously the way ahead.
Paul Honeyman is a product manager with Glow-worm
===================
As part of its Clearly Solar product offering, Glow-Worm has launched a new range of flat-plate collectors that are smaller, lighter, less obtrusive and easier and quicker to install.
These collectors have a 3.2 mm low-iron safety-glass and serpentine copper absorber. Their dry weight is just 38 kg.
A new A frame for flat roofs can be assembled in less than a minute, with minimal tools. Other mounting options include roof brackets for slate and flat concrete tiles, brackets for profiled tiles and a kit to integrate panels into the roof instead of tiles.
These collectors are available in packs containing various combinations of one, two and three panels. They come in horizontal and vertical formats and can be installed with a Glow-worm open-vent or system boiler and the Glow-work unvented twin-coil cylinder to create a Clearly Solar system.
