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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

Buy individually or both books together. Delivery is free!


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    • CommentAuthorTriassic
    • CommentTimeApr 16th 2014
     
    ""Panasonic has reportedly achieved a record 25.6% conversion efficiency for its HIT (Heterojunction with Intrinsic Thin layer) solar cell.

    The company say this beats their previous best of 24.7% efficiency for crystalline silicon-based solar cells of a "practical size", achieved in February 2013.""

    Made me wonder if I should be using conversion efficiency as a buying criteria, rather than cheapest price?
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 16th 2014
     
    That is only under optimum test conditions, £/W is the best gauge as it is cheap to put an extra panel in.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 16th 2014 edited
     
    Posted By: TriassicMade me wonder if I should be using conversion efficiency as a buying criteria, rather than cheapest price?
    Why should you, unless short of roof space?
    • CommentAuthorTriassic
    • CommentTimeApr 16th 2014 edited
     
    Posted By: fostertomWhy should you, unless short of roof space?
    In the old days no one worried about vehicle fuel efficiency, now it helps sell cars. Thought the same approach could help sell solar! Maybe I'm wrong.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 16th 2014
     
    I thought it was safety features that sold cars, or was that back in the 1990's
    • CommentAuthorsnyggapa
    • CommentTimeApr 16th 2014
     
    fuel efficiency does not directly equate to solar cell efficiency though . Fuel efficiency in effect saves you fuel every journey.
    solar cell efficiency is of academic interest unless you are constrained on space, as with less efficient cells you just use more of them.

    However the improvement in technology is absolutely to be applauded though - if the improvements filter down to mainstream and costs eventually decrease then it's a good thing - it's just not likely relevant to 95+% of the customers at this point

    For my roof, since I could only fit 6 panels I went for Sanyo HITs - I paid a large premium for them and are very happy, but I only got these because I needed 1.4kWp to meet building regs - if I had more roof I would have used more, less efficient but cheaper panels with a higher output overall.

    of course if more efficient panels were available at a price than enhanced the overall payback, then it's a no-brainer

    -Steve
  1.  
    Hi Steve, how much were they per m2?
    • CommentAuthorTriassic
    • CommentTimeApr 17th 2014
     
    Posted By: Viking HouseHi Steve, how much were they per m2?
    No idea, the quote was from some advertising blurb about their R&D efforts, not even sure they are in production yet!
    • CommentAuthorEd Davies
    • CommentTimeApr 17th 2014
     
    Too many Steves. Think VH was asking about Snyggapa's Sanyo HITs.
    • CommentAuthorsnyggapa
    • CommentTimeApr 18th 2014
     
    hard to say per m2 , the quote wasn't itemised

    6 (total 7.4m2) of panels cost us £8K so you could say >£1000/m2 - however the biggest part of that figure would be for installer's inflated profit margin under the old FIT regime. Less efficient panels would not have cost me much less
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 18th 2014
     
    The installer probably made a couple of grand, sales person about 500 quid.
    • CommentAuthorsnyggapa
    • CommentTimeApr 18th 2014
     
    it was 1 man bob so he probably made the lot - however my choices at the time were limited to bob hope, or no hope... I don't begrudge him it, it was the market price at the time.

    I could probably have got the job done for half price a week later - that was the market price then... (who says that subsidies don't distort the market)

    -Steve
  2.  
    To convert a 100m2 Passive House to Energy Plus with sufficient surplus energy to power an electric car (3,000kWh) we'd need 8,000kWh, if we use PV-T we'd need 5,000kWh PV and 3,000kWh Solar Thermal.
    Will that fit on the roof?
  3.  
    Solar Cell/panel efficiency is only a factor if your tight for space, or would like to have a few less panels on your roof for aesthetic reasons. If you have a small roof and require a higher efficiency panel you will be paying more, Panasonic are one of the best panels but you get much better £/w value for LG's higher efficiency panels. Ranging from 265watt -300watt panels (top 18.3% Module efficiency) compared to an average 250watt panel (14.93%) efficiency.

    Remember that the panasonic efficiency is for the cell not the module efficiency which will be less.

    I have a brief guide on some points to look at on our website;
    http://green-uk.com/solar-pv/choosing-right-panels

    Ultimately though the system will only perform if designed and installed well.
    • CommentAuthorrhamdu
    • CommentTimeJul 2nd 2014
     
    Go for the best price per installed kilowatt.

    Roof space considerations don't really affect the choice unless you are either (1) off-grid or (2) prepared to spend extra money to save the planet, regardless of financial return on your investment.
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