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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorYanntoe
    • CommentTimeSep 16th 2016
     
    Hi,
    Can anyone point me in the direction of a discussion group on the above? We have access to a small stream which flows all year. Impressive when it rains hard, but mostly a good steady flow, even during drought conditions.

    There is an old mill race of sorts and evidence of a fixing for some kind of water wheel/generator or some such.

    It's 10meters from the house, and I wonder whether it is worth exploring micro hydro electricity generation.

    I know I have to bite the bullet and look at flows and head and all that , but the remains of the old structure seems encouraging.

    Any pointers welcome.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 16th 2016
     
    • CommentAuthorYanntoe
    • CommentTimeSep 16th 2016
     
    Thanks Fostertom, yes I've seen this.
    The scale of anything I could look at is probably much smaller than the options in the document and the detail seems daunting. I guess if I could generate an average of 1 or 2kw per hour with battery storage, that would be sufficient. I probably haven't thought this through, get I'd make a start on checking the viability of such an idea.
    • CommentAuthorEd Davies
    • CommentTimeSep 16th 2016
     
    Try the Navitron forum - there are a few people on there with plenty of experience of micro hydro.
    • CommentAuthorEd Davies
    • CommentTimeSep 16th 2016
     
    Posted By: Yanntoe1 or 2kw per hour
    1 or 2 kW. Watts are already a rate (joules/second). Actually, for microhydro 1 or 2 kW is quite a lot. The nice thing about hydro, though, is that it tends to run 24 hours a day so even a few hundred watts adds up to quite a significant contribution.
    •  
      CommentAuthordjh
    • CommentTimeSep 16th 2016
     
    Posted By: Ed DaviesTry the Navitron forum - there are a few people on there with plenty of experience of micro hydro.

    +1
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 16th 2016 edited
     
    Do a quick calculation first.

    MGH

    Where M = mass flow rate (kg/s)
    G = gravity (10 m/s^2)
    H = height (m)

    Then work on 15% of that because of the environmental rules about the amount of water you are allowed to use (not the full rules, but good enough to see that it may be worthwhile or not).

    You can establish the mass flow rate by creating a cross sectional area profile of the stream, then measuring the flow at different points (just use floats and a stop watch).
    • CommentAuthortychwarel
    • CommentTimeSep 16th 2016
     
    Where are you ?
    • CommentAuthoratomicbisf
    • CommentTimeSep 16th 2016
     
    Posted By: SteamyTeaDo a quick calculation first.

    MGH

    Where M = mass flow rate (kg/s)
    G = gravity (10 m/s^2)
    H = height (m)

    Then work on 15% of that because of the environmental rules about the amount of water you are allowed to use (not the full rules, but good enough to see that it may be worthwhile or not).

    You can establish the mass flow rate by creating a cross sectional area profile of the stream, then measuring the flow at different points (just use floats and a stop watch).


    Are you really only allowed to divert such a small proportion of the water for very small scale hydro? Seems bizarre as you're not using [it up] and many small streams flow entirely in pipes for some distance so to divert it a few metres through a turbine would seem benign by comparison.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 16th 2016
     
    It is do do with the wildlife in the streams, not the water.
    • CommentAuthorYanntoe
    • CommentTimeSep 17th 2016
     
    Thanks all.
    Based in Cumbria, in one of the wettest valleys in the country.
    The stream in question, is highly volatile going from an average depth of, say, 100ml in dry weather, to 500ml in wetter weather. A couple of weeks ago it was 2000mm deep after 2 days of heavy rain. In short when it rains on the fell, the beck increases dramatically, however, even in times of relative drought it doesn't dry up. Being a very rocky beck it will be difficult to do a bottom profile, so the calculation of volume will be extremely inaccurate. As to 15% of the available water, this will depend on when it's measured. If it's during a dry period, the project is almost certainly a non starter.
    The 1 to 2 kW target was to cater for our current usage of about 400kW per month and to add heating for domestic hot water . This is currently provided by wood pellets.

    We live at the bottom of a North facing wooded slope, in the valley bottom, so in winter the sun only appears above the horizon in the early morning and late evening. Hence Solar PV isn't that attractive except in the summer. It does, however, tend to be very wet in winter when we need the most energy.

    I'll check out Navitron.
    • CommentAuthorEd Davies
    • CommentTimeSep 17th 2016 edited
     
    Posted By: Yanntoean average depth of, say, 100ml in dry weather
    100 mm, not millilitres?

    400kW per month
    That'd be 400 kWh/month, I assume, so about 550 watts. I've no idea what your hot water requirements are but the usual rule of thumb people quote is 3 kWh/person/day so 125 W/person. For 3 people approx 1 kW total.

    If your beck is a triangle 500 mm deep in winter and 1 metre wide then its cross section would be 0.25 m² (½ base x height). If it's flowing at 1 metre/second that'd be 250 kg/s so a weight flow of roughly 2500 N/s meaning you'd only need a head of 0.4 metres at 100% efficiency. Even if you only divert one sixth (roughly 15%) of the water you'd only need a head of 3.6 metres plus a bit for losses. Does that seem doable?

    I think most of the microhydro people do is actually higher head than that so presumably lower flow rates.
    • CommentAuthorYanntoe
    • CommentTimeSep 17th 2016
     
    OK.
    The beck is 100mm deep on average when dry.
    Yep, 400 kWh (units) per month.

    The beck varies along its length as it goes across our land, from 1.5 to 2.5 metres wide, when dry.

    Might be able to get a head of 3 metres but over a distance of 100 metres.

    Reckon 3000kWh per year for water heating in total.

    I'll have a better measure up later.
    •  
      CommentAuthordjh
    • CommentTimeSep 17th 2016
     
    I went looking for Steamy's 15% figure but couldn't find it. But I did find this rather scary document:

    https://www.gov.uk/guidance/new-hydropower-scheme-apply-to-build-one

    Hopefully the folks on the Navitron forum will make it easier.
  1.  
    Would suggest doing a stealth installation using a siphon system and a powerspout turbine. Have a look at the powerspout website for the basics.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 18th 2016 edited
     
    Posted By: djhI went looking for Steamy's 15% figure but couldn't find it
    It was 12 years ago I had to do a module in it. But seem to remember that you had to leave 85% of the flow at the 95% quartile (so when it is almost dry. But it was a while back).

    You can get some flow data here:
    http://nrfa.ceh.ac.uk/data/search
    Just go to the gauging station uphill of your property.

    The Environmental Agency can give you more details.

    As for 'doing a stealth'. There are fines for that sort of thing, as there is for burning waste, stealing seagull eggs, killing badgers, overdosing with fertilisers and pesticides etc. Kind of thing that arrogant farmers do 'out in the country'.
    We are trying to make a better environment for everyone, not benefit just one person.
    • CommentAuthorEd Davies
    • CommentTimeSep 18th 2016
     
    Posted By: SteamyTeaJust go to the gauging station uphill of your property.
    Is it likely there'd be such a thing for a beck of this size?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 18th 2016
     
    No idea, but always worth a look.
    • CommentAuthorYanntoe
    • CommentTimeSep 18th 2016
     
    No, there is no gauging station. The beck has a number of tributaries just up stream, never runs dry, but isn't normally a torrent.

    I think I need to ask a local installer of such systems , on the assumption I might find one.

    I'll let you know if I'm successful.

    Thanks for the info
  2.  
    <blockquote><cite>Posted By: SteamyTea</cite><blockquote><cite>Posted By: djh</cite>I went looking for Steamy's 15% figure but couldn't find it</blockquote>It was 12 years ago I had to do a module in it. But seem to remember that you had to leave 85% of the flow at the 95% quartile (so when it is almost dry. But it was a while back).

    You can get some flow data here:
    http://nrfa.ceh.ac.uk/data/search
    Just go to the gauging station uphill of your property.

    The Environmental Agency can give you more details.

    As for 'doing a stealth'. There are fines for that sort of thing, as there is for burning waste, stealing seagull eggs, killing badgers, overdosing with fertilisers and pesticides etc. Kind of thing that arrogant farmers do 'out in the country'.
    We are trying to make a better environment for everyone, not benefit just one person.</blockquote>


    You would only get fined if you where caught. The whole point of a stealth installation is that no one knows it exists.

    Or you could go down the red tape route.

    https://www.gov.uk/guidance/new-hydropower-scheme-apply-to-build-one
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