Microgeneration Solar technologies
New legislation introduced earlier this year has made it more attractive for UK businesses to invest in solar technology. Kerry Burns gives the low-down on the way to get the best out of your investment
become an incredibly attractive invest- ment opportunity since the feed in tariffs (FITs) came into force earlier this year. But, as with any investment, it pays to understand the principles before committing. The PV effect was discovered by Henri Becquerel in 1839, and refined through to mass-market emergence in the mid 1970s with recent laboratory performances claimed at around 42%. Intensive research will yield increasing future efficiencies. However, the real-life efficiency of most modules (panels) varies from 7-20%, at the lower end of which are emerging technologies such as organic or dye-sensitised cells. Thin film PV (8-10%) can be seen in some roof-integrated products like PV roof membranes, which are often suited to commercial or industrial premises where available area is not the limiting factor. The most prevalent PV technology is poly- crystalline, which has the ‘crushed’ texture and blue colour most often seen on UK instal- lations, with an efficiency range of 13-16%. These panels are often most suited to FITs installations because of their low purchase cost, high availability (polycrystalline is likely to be in oversupply for at least 12 months hence) and bankable performance. Monocrystalline PV (16-18%) can deliver a faster payback in some situations than its polycrystalline equivalent, and purchase costs are only marginally higher. However, those seeking higher than ‘average’ performance could swap to more expensive hybrid mod- ules, which can reach efficiencies of 19-21% and are often chosen in the UK where roof space is limited or where a prestige product is needed to reach building energy targets. In most sales pitches that UK businesses might encounter, the seller is likely to be offering one of a range of polycrystalline PV modules; their performance will be similar and prices will be comparable, so the choice may be down to factors such as length of guaran- tees, country of origin, CSR or brand aware-
Power points A
s many businesses now realise, solar photovoltaic
(PV) technology has A 200kWp PV installation on the cowsheds at Worthy Farm, home of the Glastonbury Festival
ness. The modules must be registered for the FITs on the Microgeneration Certification Scheme (MCS) website (www.microgenera-
tioncertification.org) as without this regula- tory approval your organisation will not be able to claim the FITs.
The solar panels are the bit everyone sees, and the array is a vital part of a PV generator. To fix an array to the roof, there are a variety of systems; some allow the solar panels to form the waterproof surface itself, known as roof integrated or building integrated PV (BIPV); others place the panels on top of the existing roof material, by using roof hooks and penetrative and non-penetrative fixings. The latter is often cheaper where the roof already exists, but BIPV can be economically pragmatic where employed on a new-build. BIPV offerings include glass-glass PV, facades, brises-soleils, louvres or canopies. Whichever roof fixing system you choose, the power is generated in direct current (DC) and needs to be ‘inverted’ to 240V AC for use in the home or transport across the grid. The inverter should come with a five year guar- antee as a minimum, but it is worth spending more to extend the warranty to cover any failures for up to 20 years. This guarantee will be with the manufacturer, not the installer.
10 | Sustainable Business | Microgeneration | October 2010
There are all sorts of displays available to highlight what the system is producing – from physical wall-mounted LED readouts, to online real-time monitoring with the choice usually being governed by the inverter itself. The energy produced by the array will feed into the consumer unit in your building and then into the building electrical system if demand requires it, or will pass via an export meter to the grid if the system is generating more than your requirement. You are paid per unit produced, at a rate dependent on the size of the installed system in kWp (kilowatts peak). You get this generated tariff whether you use the energy or not and the energy itself either displaces what you would normally buy from your energy supplier – so you save for example, £0.10 per unit displaced – or when exported, it attracts another £0.03 per unit. As far as paybacks are concerned, a good unshaded and south-facing PV array will yield between 8 and 10% a year through FITs, pos- sibly more for larger systems. A good installer will be able to provide a range of quotations to match your needs.
Kerry Burns is general manager at Solarsense, an installer of solar technologies based in Bristol >
solarsense-uk.com
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