By Bianca Foitzik

When my colleague first mentioned solar greenhouses, I had visions of being able to boil a kettle or recharge a cordless electric screwdriver (which, let’s face it, are only good for a couple of turns before they need re-charging) down at my allotment.

Okay – I may have a very non-technical perception of how solar energy can be used (though there are those here who are very knowledgeable indeed) – my own solar experience being limited to the installation, or rather, stringing up of solar fairy lights in the garden – but it did get me thinking that this would be a great idea for people who were keen to reduce reliance on the grid for their energy, but can’t for whatever reason put solar panels on their homes.

Polysolar and New Horizons Solar both seem to be producing a range or greenhouses (and other structures) using a patented tinted transparent PV glass.

Checking out Polysolar’s website, it says they have developed a “transparent glazing photovoltaic (PV) module, specifically designed to be used as an integrated building material and is a cost effective alternative to conventional cladding materials.”

To me this sounds a bit like building with Lego, with the added bonus that modules can be used to substitute other materials. Who knows what will happen to solar subsidies in the future, but it sounds like these modules could still make sense if you plan to build anyway, without having to rely on Feed-in-Tariffs.

So what’s the science? According to an article in The Engineer, “the panels selectively filter sunlight to allow through part of the (light) spectrum used for photosynthesis, while utilising other parts for power generation and reflecting infrared and ultraviolet for better temperature control”.  And you don’t have to be facing south for them to work (unlike conventional rooftop panels).

The same publication says that tests at Sheffield University’s solar farm suggest that a 5.5m version could generate around 900kwh per year, which Polysolar claims represents a 25 per cent increase over a similar array of traditional solar panels. What’s not to like?

Of course the reality is that in my corner of London, our allotments suffer from vandalism and theft, so for most of us, Freecycle and recycling more generally are the wise gardener’s source of garden accoutrements.

And this new technology doesn’t come cheap (upwards of £4000 for a greenhouse at Polysolar, and Which? last year reviewed New Horizon’s Energy Grow model which costs around £9000) – so for most people this would be a huge extravagance at any time.

But… if I had space in my garden and money was no object, and we didn’t intend ever to move, I think a solar greenhouse could be well worth the investment. And of course, as with most technologies, if you wait a bit, these are likely to become cheaper – it’s all about, ahem, growing the market…