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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.

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    • CommentAuthorGavin_A
    • CommentTimeJan 22nd 2012
     
    Posted By: bot de paillehttp://www.britishgas.co.uk/business/products-and-services/energy-management/smart-metering.html

    erm yeah, the link was referring to an electricity smart meter.
    • CommentAuthorSeret
    • CommentTimeJan 23rd 2012 edited
     
    The EMMA device isn't really aimed at consumers, it's more for larger buildings. However, a few people have been looking at optimising their PV systems along these lines:

    Arduino based:
    http://openenergymonitor.org/emon/node/217

    Bit more rough-and-ready:
    http://www.yougen.co.uk/blog-entry/1737/Auto+control+enables+use+of+solar+PV+for+immersion+heater/

    To my mind there's nothing wrong with doing this. The pricing structure implies minimising your export, and you'd be mad not to really. Ideally we'd be able to store excess electricity, but the economics of battery storage are marginal at best according to my calculations. I really think there's a huge gap in the market for a practical home storage system for on-grid PV. Perhaps as current batteries continue to improve it will come, but I wouldn't be surprised to see it come from out of left field either.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 23rd 2012
     
    Posted By: Seretbut I wouldn't be surprised to see it come from out of left field either.


    Will almost certainly be a resistive load such as water or space heating as that has virtually zero electrical losses. That is the trouble with the grid being pretty good at delivering electrons.
    • CommentAuthorSeret
    • CommentTimeJan 23rd 2012
     
    Even with batteries I don't think the stumbling block is the efficiency, it's more an issue of longevity. The main costs in a battery storage system are the batteries themselves. If they were either cheaper or lasted longer it would be worth doing. Until it does you're not likely to get kit for PV designed with on-grid battery systems either, so it'd have to be a home brew solution.

    Until then, storing your excess electricity as heat seems like the simplest and most economic solution for a homeowner.
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 23rd 2012
     
    There is the issue that if getting energy in and out of the batteries is inefficient then it inflates effective energy costs and carbon footprint.

    With a typical swing in generation intensity (kgCO2/kWh) in the GB grid of (say) 20% as of now, it is just possible that a good inverter/charger with Li-chemistry batteries could have an energy loss of significantly less than 20% round-trip and actually lower a typical house's carbon footprint. But only just, and not in winter when we seme to run coal generation pretty-much flat out for now. Not possible at all so far as I can see with lead-acid batteries (round-trip losses at least 20% themselves), even ignoring any emboddied costs.

    Rgds

    Damon
    •  
      CommentAuthorfostertom
    • CommentTimeJan 23rd 2012
     
    Posted By: Seretthere's a huge gap in the market for a practical home storage system for on-grid PV
    Electric car
    •  
      CommentAuthorfostertom
    • CommentTimeJan 23rd 2012
     
    Posted By: Seretstoring your excess electricity as heat
    Electric (night store) Aga
    • CommentAuthorskyewright
    • CommentTimeJan 23rd 2012 edited
     
    Posted By: fostertom
    Posted By: Seretstoring your excess electricity as heat
    Electric (night store) Aga

    At the risk of stating the obvious it seems likely that for most installs, most of any "excess" occurs outwith the heating season...
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 23rd 2012
     
    :bigsmile:
    •  
      CommentAuthorfostertom
    • CommentTimeJan 23rd 2012
     
    An Aga isn't for heating, it's for cooking and hot water, that's the point. Outwith and inwhere the heating season.
  1.  
    Although there is much more excess in the non-heating season and at the moment as a total per day we are using more than we generate, I am impressed by how much power we are getting with 4kW installation for peak periods of the day. If it's a clear day then its peaking at 2-3kW which is way more than we need unless we are running the dish washer/washing machine so it would seem to make a lot of sense to divert anything excess to heat a thermal store and save the gas boiler some effort.
    • CommentAuthorSprocket
    • CommentTimeJan 24th 2012
     
    > To my mind there's nothing wrong with doing this. The pricing structure implies minimising your export

    OK, I feel a bit better about the idea now.

    > electric car >most of any "excess" occurs outwith

    I had also been seriously considering this.
    As long as I can work around a car that has to be parked at home in the sunny part of the summer day.
    Shame there is no sensible storage for this... two cars to swap is pushing it a bit.
    • CommentAuthorskyewright
    • CommentTimeJan 24th 2012
     
    Posted By: SeretThe pricing structure implies minimising your export

    Perhaps, unintentionally entices rather than implies?

    Posted By: SeretUntil then, storing your excess electricity as heat seems like the simplest and most economic solution for a homeowner.

    Depending on:
    a) The cost of the "maximisation" technology.
    b) The available "excess" that you actually have a use for (and the value that can save, compared to other sources for that usage).
    c) The technology &/or implementation being smart enough to avoid accidental increased import.

    Ethical issues aside, unless those factors combine to produce a realistic payback for the "maximisation" process, the most economic solution is to be happy with the generous FIT and let the excess out into the grid...

    [aside]
    One problem with the current system is that without an export meter (which applies to most installs) the owner not only doesn't know how much they are actually exporting (making it difficult to assess the maximisation potential), they don't know exactly how much they are using (as opposed to importing) either!
    [/aside]
    • CommentAuthorSeret
    • CommentTimeJan 24th 2012
     

    Ethical issues aside, unless those factors combine to produce a realistic payback for the "maximisation" process, the most economic solution is to be happy with the generous FIT and let the excess out into the grid...


    Dumping the power into an existing immersion heater can satisfy all of that for about £100, so the break-even point would seem to be at about 2500kWh compared to gas or 800kWh compared to electric. How quickly you hit that is obviously going to depend on how big your array is, what other loads you're meeting, and (as you say) how efficient your dump load system is.
    • CommentAuthorskyewright
    • CommentTimeJan 24th 2012 edited
     
    Posted By: SeretDumping the power into an existing immersion heater can satisfy all of that for about £100, so the break-even point would seem to be at about 2500kWh compared to gas or 800kWh compared to electric.

    With just a standard immersion as the dump (and without spending extra on 110V transformers, etc.) isn't maximisation only available when generation is above houseload + 3kW, squeezing the annual potential yield notably?
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 24th 2012
     
    Or when the water is cold :wink:
    • CommentAuthorSeret
    • CommentTimeJan 24th 2012
     
    Posted By: skyewright
    With just a standard immersion as the dump (and without spending extra on 110V transformers, etc.) isn't maximisation only available when generation is above houseload + 3kW, squeezing the annual potential yield notably?


    Yes, it wouldn't be at all practical without limiting the power going to the heater. You can of course get 1kW immersion heaters, but they're upwards of £50 anyway, so you'd be better off trying to control the power properly IMO.

    Obviously the ideal system would accurately monitor the excess power available, and trim the output to the heater to match. The Arduino system could do this, but the parts to pull off this kind of power electronics are fairly expensive. It's probably more cost effective to just cut in relays at 500W and 1kW like the bloke I linked to.
    • CommentAuthorjamesw
    • CommentTimeAug 23rd 2012
     
    In case anyone comes across this thread in the future, I suggest that it be considered closed since there is a later thread that lists available products and you'd do better to continue the discussion there:
    http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=9487
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