Solar thermal – A shared responsibility
While there has been a growth in solar suppliers, and increasing awareness of the need for quality solutions, there is a need for widespread education both among distributors and installer engineers.
The burgeoning green industry has led to a steady stream of companies putting together solar thermal packages. However, it has been reported that over 80% of the solar thermal systems installed don’t reach part L and I estimate that over 60% of installations don’t function effectively.
The failure of these systems is not because of poor equipment, but it is the combination of components along with poor design and installation.
A large proportion of current installations are ‘pick and mix’ solutions with flat plates, tube collectors, pump stations and controls sourced from different manufacturers. While the headline brand for the solution may have an established track record, the pedigree of the system’s individual elements is often less impressive. Fortunately, there is growing awareness that a mixed source approach to solar systems should be avoided, as elements of the system need to complement one another to maximise heating efficiency.
However, while there have been areas of improved knowledge, more education is needed regarding solar thermal technology.
It is important to be aware that solar systems have evolved dramatically and it is no longer the simple procedure of putting a black collector or radiator on the roof.
It is also essential that it is understood that a solar thermal system does not function like a boiler. A solar solution draws on the continuous heat source of the sun and is designed to perform on an uninterrupted basis: the longer it runs, the more efficient it becomes and an on/off heat source is not an option.
Additionally, it is imperative to avoid solar collectors heating a vessel then becoming stagnant for long periods. With the solar thermal process, if the water isn’t used, the system retains its heat and this will increase until all fluid in the collector turns to steam. We have seen some designs reaching summer temperatures inside the collector of up to 240°C. Particular care therefore needs to be taken when dealing with an installation where there will be a summer shut-down period, such as schools or Universities. A building that closes for the hottest part of the year needs heat dumps to dispose of excess energy to ensure that the system doesn’t fail.
Avoiding carbon copies
Anyone who thinks a carbon copy of another installation will overcome the need for education should think again. It is all too easy to believe that simply by installing the appropriate combination of components, a satisfactory solar thermal heating solution will be provided. Increasingly, we are being asked to remedy the work of first generation solar thermal systems and I can cite the recent example of a UK nursing home installation. In the belief that copying a system installed at a similar nursing home would produce the same solar thermal heating results, a like-for-like solution was installed. Strangely, the owners and residents of the home were entirely happy, saying that it looked very impressive and they were pleased with the results. This was interesting because the system had, in fact, never been operated. However, because the nursing home was brand new and using a large quantity of water with gas fired heaters there was no benchmark to gauge the success of the solar thermal solution. The result was an ‘emperor’s new clothes’ scenario – the owners thought the new boiler room looked fantastic, the residents thought they were being green and everyone believed the system was effective.
I am not saying that these are instances of solar suppliers deliberately intending to mislead, but the examples given highlight the need for education and installer training.
The science of solar
There is a science behind solar thermal – it is not possible to be a plumber one day and a solar installer the next. Unlike standard window or plumbing projects, individual calculations are required for each installation; the process is entirely different from traditional boiler water heaters and glycol is involved which, in the wrong hands, is a dangerous chemical.
A number of manufacturers run their own installation courses but these tend to be geared towards two panel domestic installations and rarely focus on commercial design and install. For industrial sector training, it is important to work closely with M&E consultants and major contractors to provide training courses that cover both the theoretical and practical aspects of installation.
Accreditation, such as NICEIC, is important for any manufacturer offering training as this ensures that a proven and formalised procedure is adopted. It is not enough for engineer installers to simply sit in a room for a defined period and leave with a certificate and tee-shirt. It is essential that anyone selling a system not only provides an educational programme for installers but appropriate skill levels are demonstrated and validated.
The design process
With regard to solar thermal calculations, there are established software programmes, such as T Sol that is used by the Roth organisation. Such software products provide solar fraction analysis and energy performance data. Comparative analysis tools are also included with customised features for collectors, stores and boilers. At Roth, we have invested in T Sol Pro, a popular choice for engineers as this caters for large system modules.
However, it is imperative that anyone using such a software programme fully understands its complexities. Buying a programme doesn’t mean you will be able to use it effectively and, particularly with regard to commercial systems, training is required to facilitate competent use. It is also important to emphasise that software is only one part of the design process. The person operating the software has to be an experienced and qualified mechanical engineer as pages of configurations are produced providing base information which has to be reviewed to provide the most effective design.
But the industry shouldn’t rely on software: any areas that aren’t satisfactorily addressed should be discussed including the location, angle of the roof, how much hot water is used per day, the profile of the system’s users and how much water can be stored. It is also important to probe to establish the objective of the solar thermal system – is it contributing to a scheme or is it the sole heat source that therefore needs to be as efficient as possible, pushing boundaries to achieve a carbon saving.
In conclusion, manufacturer experience in the field of mechanical engineering is essential in ensuring that the building services industry provides the necessary support required for the installation of safe and effective solar thermal solutions. It is not enough to invest in software and expect the automated solution to answer all the questions – this has to be supported by training, both of manufacturer personnel and installers.
The industry has a shared responsibility to provide adequate education that is both comprehensive and validated: insisting on proven knowledge levels, and providing the necessary infrastructure to achieve this, is therefore key to manufacturer support for installers.