19 Jun 2007

Photovoltaic glass

“When a journalist talks about PV cells, we know we are dealing with an amateur.” Jerry Stokes, President of Suntech Europe, drops this little admonition on me as he talks me over their installation at the Kingspan (Code Level 6) Lighthouse at Offsite 2007 (see previous post). As I have already used PV cells several times in the conversation so far, he has already pencilled me in as a numbskull. I reflect on the number of times I have casually written about PV cells over the years. Oh well, you live and learn. Apparently the photovoltaic cells are the tiny little bits that make up the modules, arrays or panels (all of which are OK to refer to) but on their own are not very useful. You need thousands of cells to make a module. I will know next time.

Suntech is an interesting company. It was started in China in 2001 by Shi Zhengrong, a solar engineer. It’s seen explosive growth, mainly supplying the German photovoltaic boom, and is now listed on the NYSE with a valuation of around $5.5billion. How many six-year-old companies have done that in Britain? (Don’t know, but expect answer to be none). Shi, who owns 40% of the company, is now one of the richest men in mainland China. All from making photovoltaics.

At the Offsite exhibition last week, Suntech were showing off a Japanese PV system called Photovol Glass which is the first translucent photovoltaic skin I have seen. It can be used as a substitute for glass in applications like glazed facades and roofs. As well as generating electricity, it cuts out heat transfer and UV radiation, but admits around 10% of daylight, thus making it suitable for large glazed facades or roof panels. Money wasn’t mentioned in my conversation with Stokes, so I can only assume that it costs rather more than traditional PV, which is hardly well-known for being cheap in the first place, but if it rolls out as Suntech hope, it could pave the way for one day becoming a replacement for standard glass. Or maybe not. What does an amateur like me really know about this stuff?

2 comments:

  1. Jerry StokesAugust 20, 2007

    Hi there Mark. I am glad to see that you found our conversation interesting and thank you for providing some additional information about Photovol glass semi-transparent thin film BIPV modules.
    I was pleased to have had the opportunity of clarifying the difference between PV cells and modules but never thought I was talking to an amateur or a numbskull!
    By way of further clarification; there are two types of PV modules, those made with crystalline solar cells and those with thin films of amorphous silicon or other materials.
    Crystalline solar cells are either mono crystalline or poly crystalline. Mono crystalline solar cells have a higher conversion efficiency of light into dc electricity than either poly crystalline or thin film types.
    A PV module consists of strings of solar cells connected in series and or parallel and then usually laminated between a clear glass front sheet and a tedlar backsheet. In the case of crystalline modules typically there will be between 36 and 72 cells per module. Thin film modules, which are much larger versions of what you might have in a solar calculator are made by depositing a very thin set of semi-conducting layers onto a glass superstrate. The cells in this case are series connected across the module - the wider the module the more cells there are.
    Crystalline solar modules are normally opaque but by substituting the back tedlar layer for a second transparent sheet such as glass and by spacing the solar cells further apart a semi-transparent "light thru" PV module can be made. These PV modules are typically used in canopies or for sun shading and brise soleil.
    The Photovol glass semi-transparent thin film modules shown in your picture start life as an opaque thin film layer. A laser is then used to selectively remove material to enable light transmission whilst still enabling the thin film PV module to generate electricity.
    These Photovol glass modules are designed to be used in place of standard glazing in facades and curtain walls. Their cost if off-set by avoided building material costs, (you need a building skin anyway), solar electricity generation, solar thermal shading and savings through a reduction in cooling load whilst still providing even illumination within the building. The view from inside the building looking out is similar to wearing sunglasses - even illumination without glare whilst from the outside where the light level is higher than on the inside you cannot see in to the building.
    I would be very pleased to provide further general information about PV cells, modules and their use in buildings to anybody who is interested.
    Jerry Stokes

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  2. I want to use the photovol glass in one of my projects and I could not find any info about it's eficiency.I was wondering if you can give me some more info about it.

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