Cambridge-based Polysolar has launched a semi-transparent photovoltaic (PV) greenhouse, with view to rolling out other integrated PV building structures.
The panels selectively filter sunlight to allow through part of the spectrum used for photosynthesis, while utilising other parts for power generation and reflecting infrared and ultraviolet for better temperature control.
‘We’ve developed a product specifically for building and creation,’ said Polysolar’s chief executive officer Hamish Watson. ‘So it deals with heat, it’s less position dependent — quite frankly, it makes virtually no difference whether you’re east, west [or] south, so it’s ideal for vertical positioning on a building and it also avoids a lot of the shading issues.’
The technology is based on amorphous silicon, with thin-film zinc oxide as the conductive layer rather than the traditional indium tin oxide.
‘In terms of the cell design, what’s different about our thin-film modules compared with conventional PV is that the active material is put onto a large piece of glass. It is then scribed into cells, and those cells are linked in series, which builds up the voltage. So our modules are up to 140V each, which means that at two modules you’re already at mains voltage,’ said Watson.
‘The advantage is there’s less power loss in the system but, more importantly, you link the modules in parallel and overcome a lot of the shading issues that are a problem with conventional PV — we don’t use microinverters to control each panel because each panel is operating at its optimum anyway in a parallel connection.’
Three greenhouse modules are currently under test at Sheffield University’s solar farm, and data suggests that a 5.5m version could generate around 900kWh per year, which the company claims represents a 25 per cent increase over a similar array of traditional solar panels.