Even the early autumn sunshine fails to please our grumpy old man. Instead he takes a pot shot at solar power companies that don’t tell us about the key factor in getting payback
Time I think, as our unfeasibly warm early autumn has taken on its more familiar chill, to discuss the Great British fascination with weather. Specifically I want to address the thorny topic of solar power.
The press has been packed with stories over the past six months about the Government’s incentives to install domestic solar power – rendering it one of the boom sectors in an otherwise pretty miserable building services market. Generous feed in tariffs and offers from generators such as free installations with a few hundred pounds a year payback have further fuelled interest.
I do have a couple of gripes though (oh really? – Ed.). The first is a concern about mis-selling of systems. Here, I mainly refer to solar water heating systems that are increasingly being installed by plumbers and heating engineers. Don’t get me wrong, solar water heating can be brilliant. My brother in law (an electrician) has a solar water heating system at his summer apartment in Cyprus and the water comes out hot enough to scald you. My worry is that to achieve those sorts of results, one does need lots of lovely scorching hot sun. Fit a system to a north facing roof that’s partly shaded and just south of Newcastle and the results will be sadly somewhat different. Will a plumbing engineer tell the customer that?
No, it’s the idea of small scale domestic power generation that fascinates me because I have always been at best rather sceptical about it. I have been rather more convinced since the introduction of the feed in tariff because it gives a fighting chance of achieving a payback to the end user. I know the Grid has some issues relating to “islanding” and the potential for exacerbated problems in the event of line failures and so forth. But, unfortunately for the Grid, that remains their problem currently.
What I have learned recently is one of those blindingly obvious considerations that I suspect many others that should know better have overlooked. The key to domestic solar energy generation lies not so much in the panels that capture the sunlight, but in the manner in which that power is converted. If power is to be fed back to the Grid to profit from the feed in tariff, then payback is directly affected by how much power actually can be used.
Key to this is not the panel arrangement – although generally unshaded south facing roofs are favoured – but in the inverter technology that converts the DC current from the panels into the useable AC for the domestic supply and the Grid. This is generally not for plumbers!
I had a brief look into who does what at the power conversion end and discovered that just about none of the solar installers make mention of how they convert the power generated. This may be because they believe the general public will not understand such matters. They’re probably right, but then I don’t understand ABS really, but I sure want it on my car; I don’t know how Intel’s latest processors work, but I’m likely to want one in my laptop. I’m surprised solar installers don’t make some reference to the inverter even if only to quote efficiency.
I spoke to the world’s biggest specialist solar power inverter manufacturer – a German company called SMA – whose specialist in the firm’s posh new centre in Milton Keynes, unsurprisingly confirmed success is all in the way the power is handled. What I didn’t realise is the variance of efficiencies from the devices. SMA claims it can achieve up to 99% conversion efficiency from its products, which when compared with a device providing, say 85%, gives a dramatically quicker amortisation. In short, it’s the inverter, not the panels, which dictate the viability of a domestic solar generation system.
But, how much of the great British public is aware of that?
