Cambridge solar inverter start-up Enecsys has revealed £2.5 million more in first round funding, bringing its total to £8.5m, this time from renewable energy capital firm Good Energies.
In June last year, Enecsys announced a £6m first round from Wellington Partners and BankInvest.
"When we closed the first round, we were in discussion with Good Energies. Their funding arrived in November and now we are talking about it," Enecsys CEO Paul Engle told Electronics Weekly.
In exchange, Good Energies' MD George Coelho has joined the board of Enecsys.
Since June, the cash has allowed Enecsys to get its product, a 'microinverter' - see below, ready for production.
"A significant part of the money has been used to complete the product. It is currently in certification," said Engle. "The rest of the money will allow us to expand and take production to volume in the market place world wide."
This includes setting up sales, marketing and customer support in Europe and North America.
Microinverters are a one-per-panel alternative to having a central inverter and series strings of solar panels connected to a single high-voltage inverter.
The microinverters deliver 240Vac directly to the mains, effectively connecting the panels in parallel.
At the cost of multiple inverters, this parallel connection side-steps the problem of shading, where one panel in shade shuts down an entire series string.
Enecsys claims: "Lowest lifetime costs and easier installation of solar PV systems."
Compared to series string inverters which can be sited remote from the actual panels, microinverters have to survive a harsher environment.
Californian inverter firm Enphase popularised microinverters.
Enphase's modules are designed to be attached to the racking beneath each solar panel, and as such are specified to +65°C.
Engle sees his advantage in being able to bolt Enecsys microinverters directly to the panel.
"Enphase established the first significant deployment of microinverters. We will be a competitor," he acknowledged. "The back of a solar panel can be 85°C and we bring the advantages of 85°C operation."
The basis of Enecsys' technology came from the PhD work of co-founder Lesley Chisenga under Professor Gehan Amaratunga at the University of Cambridge.
Its intellectual property is in high-temperature operation and an undisclosed topology.
"Older topologies have major issues in needing components that have low lifetime," claimed Engle. "They go a couple of summers and then have a huge fall-out in failure."
The Enecsys inverter is 150x100x25mm, rated around 250W, and produces "a sine wave that meets all grid specs for 240V single phase", said Engle. "They can be deployed in one panel installations or thousand panel installations."
A 240V output is applicable to both Europe and the US as, although US systems are nominally 110V, almost all buildings are actually fed with split-phase supplies from a transformer that delivers 220V with a grounded central tap.
The inverter is grid-only, not being suitable for stand-alone applications with no grid connections.
Although its content is still under-wraps, the microinverter is known to include the 'peak power tracking' - the technology needed to match loads into the variable source impedance presented by solar panels.
It also includes a ZigBee wireless node for data communication, which reports to a aggregator that puts the data onto the web.
The inverter will be on sale in 2010.