Can solar catch up PV?
With the Renewable Heat Premium Payments (RHPP) for solar thermal increasing to £600, there is a strong chance that this traditional solar technology will now be rejuvenated in the domestic market.
Hence, this will inevitably lead to a reappraisal of the merits of solar thermal for non-domestic properties as well. So how can solar energy companies win customers’ business in this particularly competitive industry?
It is partly to do with communicating the benefits of solar thermal over other renewable energy options. It was only a few years ago, prior to the feed-in tariffs, that grid-connected photovoltaic (PV) arrays were merely a passing interest to academics. These days it is hard to find a street without at least one large money-generating roof-mounted PV array. And in recent years, PV has knocked solar thermal for six in terms of sales, with the feed-in tariff being its trump card. In the background lurks the much-vaunted Renewable Heat Incentive (RHI), which is poised to bring a renaissance back to solar thermal.
While traditional thinking directs that electricity and plumbing do not mix, there are now many installation companies offering a choice of both these technologies for customers’ roofs. These in turn have to compete for space on the roof with chimneys, roof skylights and vents. Indeed, there is no reason why both technologies cannot be fitted onto one roof providing that space permits and they are made visually pleasing. After all, the PV tariff rates drop noticeably over 4kWp so over-filling a roof with one technology is not always suitable. Computer simulation software now easily permits photo-realistic visualisations of a customer’s property, so comparisons can be made of a roof before and after the installation of solar energy systems. Roofing companies use this computer-based technology to show customers what their building will look like after a makeover, showing different roof tiles or skylights along with renewable technologies.
In order to gain best advantage of the sun’s energy, careful consideration must be made to the placement of solar thermal collectors. While shading should be avoided where possible, even the best locations will effectively lose part of the sky to the nearby landscape. Objects are particularly troublesome when they case hard shadows over the collector temperature sensors, as this causes useful solar energy to be lost and can even lead to localised boiling of the transfer fluid within the collector. Simulation software remains at the core of successful design by giving rapid shading impact estimations and sizing calculations.
Performance prediction is not all about the engineering. Anticipating financial payback remains a key factor in winning business. Currently the devolving governments around the country offer different types of subsidies, some national and some regional. With the existing RHPP and forthcoming RHI for households, there is already some complexity between capital grants and ongoing revenues to analyse. The commercial RHI is already up and running, with the complexity here lying in how to calculate the relative generated energy of both solar thermal and the eligible back-up heat. Hence, there can be multiple income streams also from biomass or heat-pumps as well as solar thermal. While solar thermal technology has remained fairly consistent over the last decade, the presentation and design of systems has had to shift up a gear. With so many iterative calculations to be made across different potential scenarios, and customers increasingly expecting attractive property visualisations and impressive reports, professional software tools offer the ability to gain advantage over the competition.
Enter XXX
Software aids solar visualisation
A multi-occupancy building, located in mid-Wales, was being considered for solar thermal DHW and space heating combined with PV, in order to take advantage of the commercial Renewable Heat Incentive and the feed-in tariff. It had a west-facing roof split in two parallel roof sections. It was important to take into account the overall appearance of the installation, as the building was located on a key road junction in a rural town. Various options of sizing and orientation for each array needed to be compared, with particular consideration given to the revenue generated from each subsidy scheme.
In order to best visualise the options, a photograph was taken and imported into T*SOL Pro. Using the program’s database, a range of solar thermal collector options was digitally rendered on to the roofs. The proposed location of the storage tanks meant that the length of pipe runs needed to be minimised in order to reduce heat loss. It was also necessary to ensure sufficient clearances on the roof for future maintenance.
Using the companion software PV*SOL Pro, a photovoltaic array was then digitally added to the image and configured to a suitable inverter. It was also necessary to anticipate the risk of shading caused by the height difference between the roofs. By inputting assumptions such as electrical loads, DHW consumption and space heating, the overall subsidy revenues were then calculated. Using 30m2 evacuated tube collectors with 9kWp PV, an acceptable appearance was suggested with the software calculating a total net present value to the owner of over £50,000 after 20 years.
Chris Laughton is managing director of The Solar Design Company
