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Home energy

Discussion in 'Serious' started by GMC, 15 Jun 2015.

  1. GMC

    GMC Well-Known Member

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    Wondered if there are any home energy consultants on here that could offer an informed opinion on Tesla's powerwall.

    Have to admit the message is compelling to me so am making enquiries about whether there are any planning restrictions on me that would impact ability to put solar panels on my roof.

    Question I have is whether or not I could get off the leccy grid with one of these...
     
  2. RedFlames

    RedFlames ...is not a Belgian football team

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    On the topic of battery packs you also have the ones from Daimler coming up - linky [Website is in German].


    Also re: planning - this... TL-DR: you should be fine, but check with the council anyway...
     
  3. Jumeira_Johnny

    Jumeira_Johnny 16032 - High plains drifter

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    The short answer is no. They are designed to be more of a load balancer then an off the grid solution. Both the 7 and the 10 kWh really are made for low usage hours charging, then discharging during peak usage hours. Think running the AC from 11am-4pm loads.

    At an average 35kWh usage for a home a day, you would need 4-5 of the Walls and that is with little overhead in the system for a windless or cloudy day. At $3500 before install, that would be $14,000 just for the Walls. Not counting the install, the clean sine inverters, the solar panels, the wind generator.....You can see where this is going.

    The PowerPack is another product, at a very different price range, that is more in the line of an off grid solution. Even then, at the moment, there are better solutions out there for off the grid.

    The Wall really shines in markets where the tiered pricing is very very expensive. So the overnight charging/daytime discharging can keep you in the lowest tier and over 5 years that is real money vs reaching tier 3 or 4 during the day for hours at a time.

    What this is, IMO, is a proof of concept technology to begin the conversation on a diffuse energy grid. Small local power production going to small local power storage banks; all interlinked.
     
    Last edited: 15 Jun 2015
  4. asura

    asura jack of all trades

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    Basically... what he said.

    Longer answer is do you really want to be off the grid? Yes, I know that was a question, it's just as an intro. In the UK and England in particular it doesn't make much sense to be off the grid, our weather is really just to inconsistent to rely on one or even two renewable to power our homes, on a per home basis, without going to ridiculous extremes. One example of a ridiculous extreme, is some bright spark minister who was very enamoured with bio-mass fuels and wanted to see a percentage (can't remember exactly, 10% or something) of our energy created using harvested wood. It would have required turning (more than) all the UK land mass into coppicing willow to achieve his goal.

    If everyone were off the grid, not only would there be no grid (a handy thing in many ways, though it has gotten a bit big for its boots) but there'd be no room to live for all the small scale generation.

    Micro grid communities can be made to work, but you really need a critical figure Eigg has almost achieved this, though they still need to crank up the diesel jenny every now and again - not technically an on the grid activity, but it's a dependency link and a burning of fossil fuel, so... nevertheless, theirs is the UK (European[whisper it, world wide?]) pin up child for green energy production and distribution. Definitely worth a look.

    Solar panels, they have their place, if you decide to go for them, consider a mix of PV & Thermal, it doesn't take many m2 for the hot water to start pouring in, and with a modern well insulated stratified hot-water-cylinder that can be well used.

    If you're really, really thinking about getting off the grid, and you want to maintain all your modern comforts, you're not looking at a few solar panels and a battery (you're a bit-techer, you'd have done it with car batteries by now surely) something like that is a much more holistic endeavour. You want a super-insulated, air tight house, using a MHVR as a starting point, then you can start to hang the gadgets on.

    Underfloor heating's great, you don't need (want for health reasons) to heat the water up to anything like the heat of conventional radiators and remember every watt = 1 degree C / Cm3 of water, and that adds up pretty quickly.

    You're down in the neck of the woods where air source heat pumps can be used all year round without any real issues, air-air or air-water units are available.

    Bio-mass is feasible, for heating highly insulated homes - not electricity generation for the grid - it's not my favourite technology not just because you have a fuel dependency, whitest they're getting increasingly less so, boilers can be temperamental and they do require end-user interaction.

    A wood burning stove with a back boiler is generally as or more efficient than most pellet boilers, but you don't get a helping hand from the RHI, which sucks and the control isn't as precise, so while more efficient on paper your more prone to wasted heat. Though the direct heat is localised the back boiler let's you share it throughout the rest of the house and reduces the heat waste, until your pressure vessel starts whistling....

    Rayburn still make solid fuel cooker/boilers.

    Ground source heat pumps / Geothermal, are both interesting, but take up a chunk of space and if anything goes wrong with your ground loop or bore hole they're difficult to fix.

    Wind turbines are okay on a larger scale, small domestic tend's to be not so great unless you're in a prime wind location.

    If you are building from scratch, you might want to look at an old mill for conversion or a site near (but not too near eh?) to a burn (stream) as if you can get permission for it, a small water turbine will be reliable.

    Oh, I'm sure there's more, much more.
     
  5. GMC

    GMC Well-Known Member

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    Wow. Big answers (and appreciated too)

    I should qualify my intent in getting off the leccy grid. I dont like that the big energy firms arent accountable to consumers as we dont have another alternative. Being able to dramatically reduce how much we use them for could force a change in the way they go about business. Not to mention that resources in the current model are finite and something needs to change, preferably before we have a really big problem. I still need gas for central heating and cooker, and am a long way from having the funds to build a properly efficient home so looking for what I can do I guess.

    I do believe solar is the way forward though,more so then wind or combusted fuel sources which by turns less predictable/consistent and less efficient.

    From responses so far it seems folks don't think it's a complete solution ready for prime time yet.
    Hopefully it will get there or at least close enough to push the big energy companies to start treating people like customers with options, instead of bottomless wallets to be emptied.
     
  6. Jumeira_Johnny

    Jumeira_Johnny 16032 - High plains drifter

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    Dude, you in the UK. Solar will never be viable for you. It's better to let the people in the sunny parts of the world make it for you. For you to get off the grid with solar, with overhead built into the system to cover non producing hours, you'd have to have quite a bit of land and a shed load of cash; assuming you keep a normal household and don't go full hippy. Never go full hippy.

    You're better off with multiple sources; hydro, wind, solar, geothermal. That way one cloudy day in the winter doesn't leave you stranded. Or, move to Morroco. Land, sun and lack of regulation are in abundance; so you can build any system you want.

    It's not that I don't think it's ready for prime time. It's not designed for prime time. We are buying 2 10kWh walls, if that tells you what I think of them. They are a great integrated package....for load balancing in areas with expensive peak electrical demand. Just not off grid.
     
  7. theshadow2001

    theshadow2001 [DELETE] means [DELETE]

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    I would hazard a guess that solar would be better used providing a base line temperature for hot water than generating electricity in this climate.
     
  8. RTT

    RTT #parp

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    Completely untrue. We have long days, and you don't need direct sunlight, only light - even our winter days are long enough to produce enough power from a decent array to keep a household going. I'd provide sources, but this stuff is trivially google-able...
     
    Last edited: 16 Jun 2015
  9. Corky42

    Corky42 Where's walle?

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    I've not seen mention of hydrogen fuel cells is that because my understanding of the technology, breaking down water into hydrogen and oxygen, costs more to do than we gain from using those gasses as fuel?
     
  10. Flibblebot

    Flibblebot Smile with me

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    Very true, that. Solar PV is very viable in the UK.

    I think, Johnny, that your daily usage figure of 35 kWh/day is much too high - in the UK, the figure is more like 15-20 kWh/day. I live in a 4-bed house and my usage for the last year is about 6300 kWh - so around 17 kWh/day - and I have more equipment running 24/7 than your average UK household (although perhaps not your average bit-techer ;) )
     
  11. GMC

    GMC Well-Known Member

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    Not convinced solar is non viable here. Photosynthesis is a solar powered reaction and this is a pretty green country. That suggests it's a question of collection efficiency, not solar source.
    As to how much I could self sustain, I'll have to dig out usage records from past bills.
     
  12. RTT

    RTT #parp

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    Precisely. I live in a 1 bed flat (2 people) and we eat up about 9kWh/day (which is our entire energy bill - hob, oven, hot water, central heating) - we don't have gas
     
  13. Harlequin

    Harlequin Well-Known Member

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    im on grid with a 2 kwh (10 panel) solar system and have been since 2012

    can pm you a video I have taken of my invertor showing its total output over the last 2 1/2 years

    suffice to say , even with a small system , we have a surplus on a day to day use - and at peak output can run the dryer on `low` heat without using grid power.

    edit:

    according to E.ON (our current provider) - we used 345kw/h from 1st to 31st may , which an average of 11.5 kw/h per day.
     
  14. Guinevere

    Guinevere Mega Mom

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    Basically, if you want to go off grid you need to ensure that:

    Consumption < Generation

    So you need to ditch the regular use of the 50" TV, the dishwasher, washing machine, tumble, the PC, standard lighting, sound system, hairdryer etc

    People that successfully live off grid without extreme outlay do so by being super frugal with their energy consumption. I'm not sure the tesla is the most cost effective way to do this, a bank of lead acids will work out cheaper me thinks. I remember reading about some guy who used old submarine batteries to great effect.

    But whatever the battery tech it's all possible even on solar in the UK.

    It's like living on a yacht for an extended period of time. Sure you can use an inverter to power just about anything but you'll get much greater run-times from your battery bank if you're super frugal.

    And that's why we all use so much power! We don't like being frugal with it.
     
  15. Jumeira_Johnny

    Jumeira_Johnny 16032 - High plains drifter

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    RTT, I get what you are saying in terms of using solar as a grid tie in. We have seen the results in Germany (a miserable country with totally suicidal weather, I still don't know how I survived that much rain growing up) and it certainly shows that larger grid based solar arrays are where we should be. And I'm not questioning a system such as Harlequin has, with a small surplus. But those aren't off grid.

    To remove a flat or a town house completely from the grid in a city/town and ensure normal house hold (using AC current, high load appliances) isn't really feasible. Not with the area available. Given the square meter prices for real estate in the UK, a battery bank needed for such a system would already make the normal person question it's viability using deep cycle or marine batteries. That's before building a proper vented storage space for the batteries and a good inverter and system management hardware, getting permit to install the system assuming you own/landlord hassle if you rent, hiring someone to do it properly (this isn't the time for the average person to DIY)......These are the things that make the PowerWall so attractive in price and ease of install (wall mounted, liquid cooled, self contained), they just simply don't have the capacity to make them ready for off grid.

    Solar power for grid tie in? Totally worth it, especially on a larger scale and with a diffused local production and storage pattern. Especially if you live one place long enough to make the financials work. Buying a house every 14 months? The numbers simply aren't there.

    Grid tie in systems don't have to include the ability to produce and store additional power needed to cover rainy/snowy days where your system isn't producing enough. Which is why true off grid systems almost always are over built and have more then one method of production. 2 days of heavy rain or snow can easily drain a system, leaving you in a dark spot. A wind turbine in a city backed up with a petrol or propane generator really isn't viable, particularly in a flat. You need space for that.

    As Guinevere, pointed out, most people need to significantly lower their usage to make off grid work. I know for us, living in Souther California and in a very expensive power market, we made normal and effective changes to our home that kept us from having a huge bill every month. We haven't made any changes to our lifestyle. I don't think we should. LED lights, proper insulation and efficient appliances are as far as we go (although now with the PowerWall, that's removing the AC unit from peak hours).

    I'm not moving the house over to 12v power and living like a hermit with boat appliances; in that we are like most people. We would need to use 1/3 (roughly 400sqft) of our roof space to match our current usage on a grid tie in system (not storing by battery) with full sun 93% of the time. Granted, that's with an AC unit but we rarely use that under 75-80 degrees inside. With just two of us and no pool, we have very low usage compared to the homes around us, easily on par with a 2 person house hold in the UK.

    I still think that off grid isn't feasible for the OP. But I would encourage a grid tie in system, especially if there are financial encouragements available from the city or power company.
     
    Last edited: 16 Jun 2015
  16. RedFlames

    RedFlames ...is not a Belgian football team

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    They've drastically cut the rate you get recently iirc, but the feed-in tarrifs are here
     
  17. Harlequin

    Harlequin Well-Known Member

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    to copy in my `number`s from my invertor for today as sent to GMC:

    1451 watts @ 240v was when it was taken , with 6.88kw for the day at that point (*A VIDEO I SENT GMC*) - total life output is 7392kwh for 13691 hours in use.

    power output as of 3.49pm is 772 watts for 252v with 10.51kwh for the day so far - with likely another 4 to 5 hours of meaningful generation.

    house is SSE facing with a 50 degree roof
     
  18. Harlequin

    Harlequin Well-Known Member

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    panels are 10 x 200w soleco with a schuco SB1700 invertor.

    mpp-peak is around 1780w
     
  19. Jumeira_Johnny

    Jumeira_Johnny 16032 - High plains drifter

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    I'll take a better whack at it. Let's take the 9kWh/day since it seems reasonable and if I were to do this in the UK, I too would go all electric. Also, I bet RTT has at least one power hungry PC. To go comfortably off grid (not nuclear fallout/doomsday here) and give ourselves a 48 hour reserve, we need 27kWh of power storage. I'll round that to 30, since we have a lot of dinner and house guests. That's three 10kWh PowerWalls linked, at $3,500 a piece not installed (Elon Musk has made clear you can not buy them separately, they need to be installed and monitored). That $10,500. I picked this option for it's safety and density, it eliminates lead batteries and storage issues.

    10kWh/day is 300kWh/mo and we want to make 100% of our power in a zone where you get 4.2 hours of average usable sunlight a day. We need roughly a 2800 watt system of PV panels. Now I like the panels with the micro inverters, but I really like the Kyocera 325W KD325GX-LPB with rated efficiency of 16%; $380 a panel. Nine panels come in at $3500. I would also look at the Samsung 250 LPC250SM with 15.6%; but at $375 a panel it seems like the extra $5 for the Kyocera is worth it. 9 panels is 40 feet by 5.5 feet or 220sqft.

    So far? $14,000. Over built and with extra overhead for off grid. Add another $2000 for a really nice true sine inverter. Why so much over head in the system? Given the trends in weather recently, I think over building is wise. In a bad storm, with good power management, you can push this system to 72 hours reserve easily. New York City lost power for 5 days. It covers having a dinner party or holiday meal where you might run the oven and hob all day, a house guest where the hot water and light usage spikes, a LAN party....you get the picture; normal life stuff.

    So a modern, compact off grid (city) system for ROUGHLY $16,000 with a life span of about 20 years. Doable? very much so. Viable? That depends. Will you live there the whole 20 years? Is it worth not being on the grid? The OP seems to have some tin foil issues with the power company, so maybe that is worth something.

    Leasing a grid tie in system starts looking more reasonable.

    Edit: Just saw Harlequin's numbers. So it's very doable. But that system (I'm assuming) has almost 0 reserve power. Not a bad thing, it's what I would actually do in my home in a city, bolstered by maybe a 10kWh PowerWall. But it's not off grid.

    On a larger property away from the city, I would would have 2 AC wind turbines and a larger PV array linked to larger storage. But that sort of off grid would be my forever home with a need for a larger infrastructure (project shop, green house), so a 30+ year investment with no need for a return.
     
    Last edited: 16 Jun 2015
  20. Harlequin

    Harlequin Well-Known Member

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    that's on good sun days - given we are northern Europe (London has a very similar latitude to Calgary - we are damn lucky for the jet stream) , winter on some days generation for me is measured in 10`s of watts.

    so - for me personally , for real off grid - you need an additional `back up` - a small wind turbine would be good - say 1kw.>2kw - can be added to a main invertor no the per panel micro ones.

    schuco do a combi invertor ;)

    edit:

    you can purchase , outright , a grid tie system in the UK - the power companies pay you a ` feed in tariff` = you sell the excess electricity back to them.

    also my system is grid tie not offgrid
     
    Last edited: 16 Jun 2015

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