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Author Topic: Designing heating & hot water system for off grid new build  (Read 4500 times)
biff
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« Reply #60 on: November 06, 2020, 10:26:14 AM »

Well OK,
      H.mmm,I fell I'll in 2010, Sorta OK now, need a eye opp.
 Have 2 new hips, state of the art hearing aids but they can do nothing with the brain. It's a bit like the new type APC ,  IPSs, when you try and work them with big external batteries, they drop into factory set default and shut down after 20 mins. I won't be going into any OPH. freeze.
        Biff
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« Reply #61 on: November 06, 2020, 11:10:44 AM »

Well Biff, I commiserate. I am over 70 and have several metal joints and hearing aids but I was horrified to read that you are ‘organising future choirs” and hate to speculate why! stir

And I rely a bit on expert electricians and plumbers and builders but I do have go, especially with advice and guidance from this forum. Long may it last.

But, how to you wire a generator outside into an electrical spreader inside the house without causing a helluva draught? snow
Thank you all, David
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6 Kw Proven wind turbine, 15 Navitron evacuated solar hot water tube array and 1.8 Kw PV, grid connected (SMA inverters) and GSHP supplying radiators and UFH. Wood burning stove (Esse 300) and oil fired Rayburn. Rainwater harvesting 4500 litre tank underground and 1500 litres above.  Kia e-Niro
biff
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« Reply #62 on: November 06, 2020, 01:07:29 PM »

Ahh, djs63,
       Choirs are the in thing here in the bog,
     We are overrun with senior Rock Bands and good choirs are hens teeth,  yet I see where yee are coming from. All the good bands have Choirs, even Dangle O Dongle who just lives down the road,
   No, I would not get away with that. Mrs Biff is  smirking away here. The sun is cracking rocks out there and I'm off to the shed to hide and fine a chore to finish, Grin
      Biff
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« Reply #63 on: November 07, 2020, 09:37:18 AM »

I had three 'barn cats' at my old house and I rarely fed them so they'd hunt. Mount your bird table on top of a 110mm soil pipe, the birds will come and you'll get hours of pleasure watching your cat trying to climb up it then sliding back down  hysteria  hysteria I'm sure there is probably an argument that a correctly loaded and used dishwasher is more efficient than  heating the water but I actually find doing the dishes quite therapeutic and good for my 'engineers hands'  fingers crossed! Neither the plumber or the electrician that worked on my house had seen a new build without one  Shocked Me, I hate the feckin things like some folk hate 4x4s  wackoold I have three of those  fingers crossed!
Would have to be pretty high - mine's a good jumper, she's even been up on our roof a few times so could probably jump onto anything under 5ft.

well , ?  is the "
Quote
£1500/year
" figure so much out  of reality ?  or are you pdf and paul ignoring something ?


And again 20k  for a grid connection  to pay for import energy from a dirty grid , when you do not get anything close to that amount one pays per unit , when exporting green home-brew units .... hmm
That's so far out from reality it'd make Trump proud - essentially that graph only works if you have net metering and can use the grid as a giant battery. Off grid, if you use that for sizing you're going to be running a generator most of the time since there is about a 6 month gap between when you're generating the electricity and when you need it. Using PVGIS to get a prediction for a 15kW PV system placed at Benbecula airport with no shading from hills, etc. gives the following output.


So in December, that gets you an average of 6.4 kWh/day (i.e. an average of 266W) for everything - heating, lighting, hot water, refrigeration, etc. compared to about 60 kWh/day in May.

The next graph is a heating balance for a Passivhaus built where I am (southern UK, so much evenly spread out than it would be in the Hebrides). The grey bars are where additional heating is needed. Note how the heating demand is the exact inverse of the PV resource



So a 100m2 passivhaus (i.e. an exceptionally well built and insulated structure) is going to need ~500 kWh/month in December just for heating - you can probably just about do this from a heat pump (COP 2.5 is pretty reasonable) but you then won't have any hot water, lighting, cooking, etc.  freeze

In reality you're going to manage in clear weather, and running the place off a diesel generator for the rest of the winter. Diesel generators are absolutely filthy compared to the grid - you're looking at 250g of diesel per kWh mechanical at best. Assuming you're charging batteries a lot of the time (~10% losses there) and the mechanical -> electrical conversion is 90% efficient you're at about 310g of diesel per kWh(e).
Diesel is 2.68 kg of CO2 per litre, and a density of 0.85 kg/litre - that means any electricity from diesel is ~980 g/kWh and a shedload of particulates, NOx, etc.

At the moment there is virtually always some gas on the grid, and exporting solar will displace it - it's only on very rare high wind days that we hit the practical minimum level of gas, when PV tends to be quite low. That means the grid is acting as a near-perfect battery subject only to transmission losses. Even accounting for these, if you produce an excess of more than maybe 20% annually then you're responsible for a net reduction in grid emissions - something intrinsically impossible if you're off-grid. There probably **is** a sweet spot where you're cleaner off-grid, but it's likely to be quite a narrow one and getting narrower as the grid cleans up.
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brackwell
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« Reply #64 on: November 07, 2020, 10:26:44 AM »

PDF27,
Good presentation.


Makes that £20K connection fee more attractive particularly if the builder digs the trench whilst on site to save costs.

For me PV is a non starter for the reasons PDF shows.  I could put my faith in wind and hydro as these are well matched to the requirements.
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Alan D
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« Reply #65 on: November 07, 2020, 11:00:01 AM »

You could use the £20000 for buying 156 of these.

https://www.ebay.co.uk/itm/6000W-6-Blades-Wind-Turbine-Genertor

156 times 6000W = 937793W if its a bit windy. £127.96 Each

I am a bit suprised that the manufacturer does not know how to spell Generator
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pdf27
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« Reply #66 on: November 07, 2020, 11:11:27 AM »

Makes that £20K connection fee more attractive particularly if the builder digs the trench whilst on site to save costs.

For me PV is a non starter for the reasons PDF shows.  I could put my faith in wind and hydro as these are well matched to the requirements.
PV is great off-grid, but assuming that you can use summer PV generation for winter heating just doesn't work and the further north you go the worse it works. Certainly if you've got the water for hydro that's a very good option and **probably** cheaper than a grid connection if you've got enough water that you only need at most a small battery to deal with peak loads (oven, etc.) - and even if the water supply is seasonal then a relatively small PV system can almost certainly fill in the gaps well. If you've got excess water then you can save a significant amount of money by using resistance heating instead of heat pumps.
Wind is a little less clear - you need bigger (more expensive) batteries and probably will end up with some diesel. It's also likely to be a relatively high maintenance solution. That's where it starts to get dubious - both economically and in environmental terms - compared to a grid connection.
Once you're on grid then the biggest PV system you can afford/accept makes clear environmental sense and probably economic sense too, although the same amount of money in an offshore wind turbine would give vastly more power, so it isn't totally clear-cut.
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Alan D
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« Reply #67 on: November 07, 2020, 12:14:17 PM »

December is the best time to go there and do a survey for where to put P.V. panels.

Time and money can be wasted by assuming the panels wont have any
shading issues.
Then you look at the panels a few months later to see the Sun not shining on them.
The big Yellow thing definitely drops lower this time of year.
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camillitech
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« Reply #68 on: November 07, 2020, 02:06:40 PM »

PDF27,
Good presentation.


Makes that £20K connection fee more attractive particularly if the builder digs the trench whilst on site to save costs.

For me PV is a non starter for the reasons PDF shows.  I could put my faith in wind and hydro as these are well matched to the requirements.

It is an excellent presentation of the facts, a fine business case for doing the 'sensible' thing but for some people living 'off grid' is a lifestyle choice. Probably not a sensible one from the viewpoint of most people living a normal and average life. There are many reasons people choose to free themselves of various shackles of the crowd and normality, extreme sports, yearly cruises, challenging jobs, amassing money or flash cars. Me, I always wanted to live 'off grid' probably after pouring through the Exchange & Mart property section 50 years ago and seeing what you could buy in a remote location for the price of a mid terrace 'two up, two down' in commuting distance of a northern town. There is something uniquely satisfying about not having any wires, cables, pipes and there associated utility bills attached to your house. It may also be difficult for people from a town to realise how common power cuts are in rural and especially island communities. Frankly, I don't care about the economics or the sanity, I love it  wackoold As for my only worry of getting old and being unable to maintain all this stuff I guess a large batch boiler could easily take care of heating and DHW, situated in that agricultural shed along with enough room to store and cut the wood. Nothing worse than cutting wood in the teeth of west coast gale (been there, done that) and if you get the right sized boiler it'll take huge logs. 10 or 20kW of PV will more than take care of your winter usage excluding heating and DHW. So, no need for high maintenance wind turbines or unblocking hydro turbines.

Aye PDF, my bird table would have been at eye level so just a little over 5' I guess. Dunno if the cat has the brains to go for the table, in my experience they always tried to climb the pole and slid back down, hilarious. 
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« Reply #69 on: November 07, 2020, 02:55:59 PM »

It is an excellent presentation of the facts, a fine business case for doing the 'sensible' thing but for some people living 'off grid' is a lifestyle choice. Probably not a sensible one from the viewpoint of most people living a normal and average life. There are many reasons people choose to free themselves of various shackles of the crowd and normality, extreme sports, yearly cruises, challenging jobs, amassing money or flash cars. Me, I always wanted to live 'off grid' probably after pouring through the Exchange & Mart property section 50 years ago and seeing what you could buy in a remote location for the price of a mid terrace 'two up, two down' in commuting distance of a northern town. There is something uniquely satisfying about not having any wires, cables, pipes and there associated utility bills attached to your house. It may also be difficult for people from a town to realise how common power cuts are in rural and especially island communities. Frankly, I don't care about the economics or the sanity, I love it  wackoold As for my only worry of getting old and being unable to maintain all this stuff I guess a large batch boiler could easily take care of heating and DHW, situated in that agricultural shed along with enough room to store and cut the wood. Nothing worse than cutting wood in the teeth of west coast gale (been there, done that) and if you get the right sized boiler it'll take huge logs. 10 or 20kW of PV will more than take care of your winter usage excluding heating and DHW. So, no need for high maintenance wind turbines or unblocking hydro turbines.

I'm an engineer, I totally get the urge to do it. I just want to make sure that Rusty has a clear understanding  of what he's getting into - from the statement in one of his posts that "I can get a grid connection but it will cost nearly £20k (!) so I'm trying to go off grid instead." that isn't entirely clear. You've done brilliantly with it, but I know I and probably 95% of the forum wouldn't be able to keep it up.
Fundamentally it is and needs to be a lifestyle choice - if you're building a house and want electricity in it then unless you're incredibly remote it's unlikely to be the best bet.

Aye PDF, my bird table would have been at eye level so just a little over 5' I guess. Dunno if the cat has the brains to go for the table, in my experience they always tried to climb the pole and slid back down, hilarious.
You should film it and put it on YouTube - would probably make more from that than the day job!
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« Reply #70 on: November 08, 2020, 12:03:56 PM »

Welcome Rusty

IMO you have had some brilliant advice only 2 things I would recommend that you also carefully consider


1.
Is it at all  possible to  try and  incorporation as much thermal mass within the thermal envelope as possible.
As this  will buffer temperature changes on those days when energy is short .

&

2.
If you go with a MHRV and conditions are at all feasible look into the possibility   of  the  installation of an earth tube to feed the unit since  it will both warm and cool  at the appropriate times of year  for free.

Good Luck and please keep us posted on progress , that is what we all feed on 
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« Reply #71 on: November 08, 2020, 12:09:43 PM »

Interesting project Rusty55.
We were faced with making the grid-tie/off-grid  choice 10 years ago for an existing dwelling in mainland, northern England with no "grid" connections of any kind. We were quoted £28k "budget" cost for grid-tie (electricity). This confirmed our original intention of remaining off-grid and we effectively also started from scratch having inherited nothing useful. We have not regretted that decision for a moment but if you are starting out and intending to be there "for life" it is worth taking a moment to review the long term economics and, of course, the comfort factor as already suggested.

It is a good idea to  run some 15-25 year projections (of your own) of the cost of services connection and bills  against all the the likely costs of installation, repairs and renewals etc that will be required for an off-grid installation (including costs for diesel/propane/wood etc). We did this kind of financial health check and are still well in pocket currently - but critically we do have incentive payments (FITs etc) added into the equation. I expect us to still be way ahead after 25 years but thereafter the gap will obviously narrow considerably. The living has been comfortable. At what point it starts to become less so due to age and/or the strains of refurbishment remains to be seen but I don't expect us to be actively interested by then.

Of course it is not possible to predict what will happen to prices of either utilities or off-grid equipment in the future but one thing for sure, the cost of your grid connection is unlikely to have reduced if off-grid becomes intolerable.
 
Our personal incentive for going off-grid was as much about distancing ourselves a bit from consumerist society as saving the planet (far too late for that I'm afraid). The satisfaction in doing this is enduring but, to be brutally honest, just buying renewable power self-sufficiency barely scratches the surface for either of those ambitions.

How did you arrive at your expected usage range of 3-10 kWh? Seems very reasonable but then you mention things like UV which, even if a modest size, could consume 10% of your lowest figure on it's own. Have you included all the usual baseline loads - fridges,  freezers,  small electronics etc? Assessing your consumption accurately and then being able to live within that is the key to building the right off-grid system.
 
With regard to a turbine. I would be a bit wary of assuming all turbine disaster stories are related to weather - poor selection, wrong installation, lack of proper servicing etc all contribute as much. There are turbines that will survive Hebridean conditions. I have no first hand knowledge of the Hebrides but a quick google suggests average winds of 22 mph with average maximums of 86 mph. I am guessing here but they are probably not particularly turbulent winds so not necessarily turbine killers although high utilisation will require more regular maintenance. At odds with most opinion on here I would seriously consider a decent turbine before loading up PV. It would be the more expensive and needy installation (HP DIY route perhaps excepted) but it would utilise by far the best resource available to you (unless there is hydro potential).
  
Whether the Hebrides are sunny or not the latitude still determines actual PV performance and that performance will not be delivered as a daily average at any time of the year. With 5kWh PV, in winter you will go days with a shortfall and conversely you will have little domestic use (in a super insulated house) for the excess potential in the summer.
 
I suggest you plug some numbers into the PVGIS off-grid tool for a view of PV/battery relationship. Try and get that to balance and then ask yourself why you might buy loads of PV, when for most of the year you either can't store it all or don't have enough to stop the battery emptying. If you have very low heat demand the issue is magnified.
 
When you look at the examples from other off-gridders you need to be careful of comparing apples and oranges. Individual lifestyles will demand, or can live with, different consumption.
 
Our situation is equally individual but may give you another small insight.

There is someone home all the time and we use all that electric stuff an average grid-tie home might, just a bit more mindfully perhaps.  Our baseline (ie no "active" usage) daily electricity consumption is around 3-4kWh. Actual consumption varies with available generation - often well in excess of 50kWh. Least we can get away with is 4-6kWh in summer and 6-12kWh in winter with heating systems running. Generally there is lots of time-shifting of large loads, switching between electric and propane for cooking and mixing of heating systems - some of it automated. We have high heat demand and reasonable heat storage with the two matched ok. We have modest PV potential and often can not utilise it all in summer. We have over-sized turbine potential and often struggle to utilise it all throughout the year. We still need to run our generator to contribute 2-3% of our generation.

With experience there are some things we would do a bit differently - 48v with a slightly bigger battery, some extra and/or better configured heat storage, maybe splash some cash on more efficient white goods. In general though we would not change the set-up until renewals are required and feel no need to add extra generation.

I publish our generation/consumption data here - https://www.navitron.org.uk/forum/index.php/topic,31346.0.html
no more than academic interest I suppose but at least the numbers are real.

no more than academic interest I suppose but at least the numbers are real.

Good luck with it all and keep us informed, there is always something for us all to learn.
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« Reply #72 on: November 08, 2020, 01:53:08 PM »

It is unfortunate that most off gridders start with a dwelling already built and do their best improve energy consumption.  However IMO nowhere near enough is done to design the building correctly in the first place to reduce consumption and improve comfort levels.  Good eg of this for me are,

Passive solar gain and ratio of thermal mass to help prevent overheating in summer and warm enough in winter.

Means of resticting over solar gain and vice versa.

Location, shape and orientation with respect to local landscape. Shading from the prevailing wind direction by tree etc.

Long term energy storage such as heat stores under the house.

Ability to shut down certain parts of the house in extreme cold.

Strategic position of wood stove in view of the above.

Entrance halls for air locks

etc.

I remember watching "Grand designs" on I O Skye i think where they designed a purposful house for the enviroment which showed some things which can be done.

This is where the problem lies not in this or that type of leccy/heating/ HW etc.




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« Reply #73 on: November 08, 2020, 06:27:11 PM »

I had three 'barn cats' at my old house and I rarely fed them so they'd hunt. Mount your bird table on top of a 110mm soil pipe, the birds will come and you'll get hours of pleasure watching your cat trying to climb up it then sliding back down  hysteria  hysteria I'm sure there is probably an argument that a correctly loaded and used dishwasher is more efficient than  heating the water but I actually find doing the dishes quite therapeutic and good for my 'engineers hands'  fingers crossed! Neither the plumber or the electrician that worked on my house had seen a new build without one  Shocked Me, I hate the feckin things like some folk hate 4x4s  wackoold I have three of those  fingers crossed!
Would have to be pretty high - mine's a good jumper, she's even been up on our roof a few times so could probably jump onto anything under 5ft.

well , ?  is the "
Quote
£1500/year
" figure so much out  of reality ?  or are you pdf and paul ignoring something ?


And again 20k  for a grid connection  to pay for import energy from a dirty grid , when you do not get anything close to that amount one pays per unit , when exporting green home-brew units .... hmm
That's so far out from reality it'd make Trump proud - essentially that graph only works if you have net metering and can use the grid as a giant battery. Off grid, if you use that for sizing you're going to be running a generator most of the time since there is about a 6 month gap between when you're generating the electricity and when you need it. Using PVGIS to get a prediction for a 15kW PV system placed at Benbecula airport with no shading from hills, etc. gives the following output.


So in December, that gets you an average of 6.4 kWh/day (i.e. an average of 266W) for everything - heating, lighting, hot water, refrigeration, etc. compared to about 60 kWh/day in May.


Quote
That's so far out from reality it'd make Trump proud - essentially that graph only works if you have net metering and can use the grid as a giant battery
 

well pdf , that graph i posted, has nothing to do with net metering nor a battery  and neither an off grid idea , its just a graph about  energy costs of an Joe average house  in the UK   Wink   ,  and i assume those prices for energy are higher on those Islands  whistlie , so from my engineering  perspective  , its just  a  1. semester engineering at University  lesson , 20000 GBP  for a wire, plus import of  monthly/yearly  bills , just ads up Wink  
 But surely in 7th semester , i learnt about self-consumption and battery size  and the percentage  of being  autonomous
Would-not it be great  that   those " Islanders" join up and built their own grid ?  instead of  paying just 20 K each  for a wire Wink  Cape Clear Island( now grid connected) , that i can see  from my village , did that ,  and was one or the first kind of that idea  and it is supposed to be the first Hybrid Wind (renewable) -Diesel-battery  Island  of its kind , SMA was still young then , 1998 ....  should be a huge pride for a local community to be as much self-sufficient  as possible , ....https://ec.europa.eu/info/news/progress-clean-energy-eu-islands-initiative-2020-oct-27_en

https://cordis.europa.eu/project/id/WE.-00306-84/de

Quote
Following a damage in the battery storage system and the local utilities unwillingness to take over the operation of the system, only the wind turbines were still in operation in the beginning of 1993. The future of the project is uncertain due to the scheduled connection of the islands to the mainland grid. The ultimately very bad relationship between ESB and SMA have considerably detracted form the outcome of the project
Sad isn't  it ?



All the best  to MR Trump the climate change denier , from me Wink

Billi
« Last Edit: November 08, 2020, 07:01:50 PM by billi » Logged

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« Reply #74 on: November 09, 2020, 12:07:12 PM »

Choose the right design in the right place and the jobs half done.

https://www.granddesignsmagazine.com/grand-designs-houses/36-tv-house-convention-breaking-eco-home-in-the-isle-of-skye

" Practically speaking, the structure is unbelievably energy efficient – heating bills for the year are expected to be less than £50 – but, surprisingly, it doesn’t have a lot of snazzy eco features typical of this type of new-build. Expensive solar panels and ground source heat pumps were not an option with their budget. The only source of heat is a wood-burning stove in the open-plan living room, which is used in tandem with a mechanical ventilation and heat-recovery system."
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