THE BLOG

Has London's First Concentrating Solar Plant Just Gone Live?

05/09/2013 13:52 BST | Updated 03/11/2013 10:12 GMT

Necessity is the mother of innovation, and unconventional problems call for unconventional solutions. The building world has been stunned this week, by announcements that 20 Fenchurch Street - previously given the moniker of 'The Walkie Talkie', has now been rechristened 'The Walkie Scorchie' after news emerged that the building's concave shape has been concentrating solar energy onto the nearby streetscene; melting the plastic of several vehicles, burning bicycle seats, setting fire to carpets and blinding people walking along Eastcheap near Monument station. Journalists have been frying eggs in the sunlight to demonstrate the effect.

It's a real headache for the building owners - but in the modern parlance, could it also be a "probortunity"?

Rafael Viñoly's unique design tapers from the bottom - affording more floor space at the top of the building, giving rise to its unique concave shape. Unfortunately, London's denizens have just discovered that it's double and triple glazed aluminium cladding, has properties known to Archimedes in 214-212 BC. It is said by Anthemius of Tralles that he used "Burning Glasses" to set fire to the Syracusian ships. The TV series "Mythbusters" has several times set out to examine this effect, both with MIT students, and in San Francisco. They succeeded in charring wood, and creating smoke and a small amount of flame.

It's all a bit of a pickle, and a PR disaster for those concerned - but could 20 Fenchurch Street be an interesting sandbox for a novel type of renewable energy generation?

The current solution proposed by the builders, is to erect a temporary scaffold - but it's clear that a longer term solution is going to be required. Perhaps this could incorporate elements of renewable energy generation? The sunlight reflecting onto Eastcheap below, has been reported by City A.M. to have an intensity of six times that of sunlight. Should a permanent shade be erected, this could be an ideal opportunity to deploy concentrating photovoltaic technology in an urban environment.

Unlike ordinary photovoltaics - the solar cells that we are fast becoming used to seeing on building's roof lines, concentrating photovoltaics use optics - in this case a nearby skyscrape, to focus sunlight onto specially designed solar cells capable of withstanding the temperatures of the increased intensity of sunlight. Multijunction solar cells can achieve efficiencies in excess of 44% . Heatsinks are used to cool the semiconductor junctions down - so that they can operate efficiently - as heat reduces the efficiency of solar cells. With a brightness in the region of "6 suns", such a shading device would be classed as Low Power Concentrating Photovoltaic technology - which employs cells not much different to conventional solar panels.

Of course, it is uncertain for exactly how long the complex interaction between the curved geometries of the building and the sun's path in the sky with be focusing rays onto unsuspecting Londoner's for. Some would contest that for this limited period of the year a PV installation might be uneconomic. That said, a cursory Google suggests that there are companies willing to hire out Solar-based generators (even if most seem U.S. based) - [Here] and [Here] so a hired temporary solution might be a bright way to turn a PR disaster into a publicity coup.

Perhaps if a permanent shade is erected, it could feature this technology, and feed clean green energy back into London's grid. Until then, 20 Fenchurch Street and it's environs will continue to remain "Hot Property".

The obligatory book plug, is that many of the themes encountered in this article have been covered in my book "Solar Energy Projects for the Evil Genius".