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Author Topic: Introduction and off-grid living questions  (Read 10297 times)
DanielCoffey
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« on: November 03, 2015, 03:28:47 PM »

Hello folks, I am delighted that I have found this forum as I will shortly have the opportunity of moving off-grid. I thought I would start with an intro and then throw some questions and concerns out to the forum to see what sticks, what is trodden on and what you throw back at me.

My wife (who is disabled - yes this is relevant to subsequent questions) and I are about 50 and currently living in a mid-1930s first-floor flat that is on-grid with Scottish Power in Edinburgh. We have no renewables as the roof is shared with 6 owners. Our current utility usage is 6500kWh for gas (heating and domestic hot water but no bath or shower) and 3750kWh for electric (including a power shower). My wife has two pieces of healthcare-related equipment which are on 24/7 and consume about 50W between them (air pump pressure-relieving mattress and a CAS Alarm with a toasty hot wall wart). We have no income other than benefit as she is severely disabled and I am her fulltime carer.

Now here it gets interesting...

We are about to receive a large lump sum which we intend to put into a new build PassivHaus bungalow of around 120m2 in the Scottish Borders (mid- or eastern Borders rather than the windier/wetter west coast). We are leaning towards the smaller Borders villages (like Clovenfords/Walkerburn and similar) rather than the towns because you get a lot more plot for your cash down there. A finger in the air division of the lump sum would put us in the ballpark of 125k for a plot of around half an acre, 275k for the design and build of the PassiveHaus bungalow and a fairly large contingency to live off for a year while the build was happening and our income-related benefits were stopped.

Plots that are not serviced or are missing certain services seem fairly common as it is mainly rural in-fill or failed farms in this area. Water is a given as we will insist on this. Electricity is usually adjacent, gas is often absent and sewerage is usually absent. Telephone is present, mobile is patchy and internet is likely to be slow.

The PassivHaus design would allow us a very large thermal store, would favour Solar PV but would lead us away from solid-fuel or any other combustible heat source for safety and insulation efficiency.

We had jumped on Solar PV as the main energy source and had seen the solar plus storage options that have been in the news recently and this got me searching for more information and guidance on what other folks are doing. After a few false starts trawling random battery innovators, I ended up here and thought... do I actually even need to be on grid at all?

As far as I see it, I could pay for the electricity to be brought on the site and opt for, say (subject to planning of course) 6-8kW of PV, a modest battery and stay on the grid as most folks would expect me to... OR I could do all that but have a larger battery store and only use the grid for emergency top-up although I would have to pay the standing charge of course. The alternative is going off-grid with PV, the larger batteries and generator for emergencies and this is attractive but terrifying at the same time. I have been well brainwashed by the Utilities over the years to believe that "You need us. Trust us. Stay with us." and the thought that I might not need them is frightening from a mental point of view.

With the FiT for new installs going down the toilet from next January, we have to want to do this for the love of being clean rather than a desire to make "$$$ in our spare time" so we would want to do it right. We believe in paying properly for well-made components of a system. I would have to get a professional installation as I have no real talent in this area myself and would also have to remain in my role of carer in Edinburgh while the property was being designed, built and finished. It would be a "fully managed turn-key" project.

Now over to you. In the words of Heath Ledger in Casanova... "I have too long dominated the conversation. What are your thoughts on the matter?"

Daniel.
« Last Edit: November 03, 2015, 03:33:59 PM by DanielCoffey » Logged
dickster
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« Reply #1 on: November 03, 2015, 03:54:19 PM »

If you build to high insulatory standards, minimal hot water from a stove that is only on tickover is something that you should consider carefully. Also insulated foundations seem to be a good idea. Good luck!
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DanielCoffey
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« Reply #2 on: November 03, 2015, 03:59:40 PM »

Hopefully the PassivHaus standards will specify a wonderful level of insulation on all sides as well as top and bottom. It would include MVHR and Solar PV into a huge thermal store but I would have to consider if Solar Thermal was effective enough compared to more PV.
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A.L.
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« Reply #3 on: November 03, 2015, 06:56:56 PM »

hello and welcome,

- 2300 per square meter seems an awful lot even for an off mains drainage passivhaus. I would thought if you stick to 'low tech' solutions for insulation, construction etc 1500 would be adequate.

- remember a 120 sq metre Passivhaus is unlikely to require more than 1.5kW to heat

- 6kw of PV will in January only average around 4.5kWh of electricity per day and that is before system inefficienceies
       have a play here - http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php

- I am concerned about your 'large thermal store' what do you expect it to do? generally 4 days storage is the maximum realistically unless you wish to attempt interseasonal storage.

- solar thermal can return 3X as much as PV on an area basis but a large array would only make sense if attempting interseasonal storage.
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ceisra
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« Reply #4 on: November 03, 2015, 08:30:17 PM »

We have a member on here Camilltech who has his own blog
What he is building on Rassay probably fits 95% of what you require
It's well worth a read, probably the last year would be a start
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DanielCoffey
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« Reply #5 on: November 03, 2015, 09:16:59 PM »

Thanks for the feedback and blog suggestions. I think Camilltech is way ahead of what we would be able to specify in our new build in that he has wind and water to pad out the solar through the year.

The more I think about it, it is beginning to look like we will start with a decent PV array, a good battery store with space to expand, a grid connection as the winter top-up  source and a generator for when it all goes wahoonie-shaped after a winter blow. Then after a couple of seasons of learning what the actual consumption is like in the new place we can consider either more PV or adding wind if it is feasible before looking to cut the tie to the Utilities.

The thermal store I was referring to would be something like a 1000L water tank for domestic hot water. I have not looked into the systems inside a PassivHaus yet apart from a couple of build logs. One was a bungalow but larger than what we can afford and the others were family homes.

I have been advised to allow at least 2000/m2 for the build because bungalows can be tricky to get signed off for PassivHaus due to the size and extra on top for design and white goods. There will be additional costs for insurance, bringing in the utilities and of course the PV and battery kit which the other PassivHaus builds did not have (they were all wood-burning with the associated constraints that added).

When we get closer to considering plots I am sure we will be back with lots more questions. Hopefully we will be reviewing plots in the Borders after the Christmas break.
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billi
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« Reply #6 on: November 03, 2015, 09:59:07 PM »

me are  confused now  ,   ......  i thought a Passiv house needs no thermal store


overzize  PV and battery  and  get a  heatpump  ... battery ,  from bater in poland  perhaps ,


Regards
Billi
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
DanielCoffey
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« Reply #7 on: November 03, 2015, 10:24:56 PM »

As far as I am aware, a PassivHaus uses the water tank to store surplus heat from the MVHR, Solar Thermal (if fitted) and PV Immersion. It is supposed to be used for domestic hot water and as a heat source to return to the MVHR if needed (I am unsure about that last part).

The reason that PassivHaus don't really like solid fuel stoves is that they would need a dedicated air supply and associated ducting/flues which cause thermal bridges through the insulation. They have a risk of combustion products entering the living space if there is negative pressure in the property (which is why a PassivHaus will not have vented tumble dryers or cooker hoods). The good news is that if you really go overboard on the amount of insulation, you don't really need stoves. Just the MVHR and scavenged heat from occupants, a couple of towel rails and domestic electronics should be all that is needed.

The overall benefit is an uncluttered roof for perfect PV.

I think we will be looking to start with up to 8kWh of panels and a dedicated battery/machinery room with an option to expand the battery later.
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billi
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« Reply #8 on: November 03, 2015, 10:50:31 PM »

Quote
8kW
sounds hot  to me

Cool  ,can u get it installed on the land  before the end of this year (FiT) ?

Billi
« Last Edit: November 03, 2015, 10:54:28 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
DanielCoffey
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« Reply #9 on: November 03, 2015, 10:57:00 PM »

If you want to see a good PassivHaus build, here is a nice one of a family house in Scotland with 4kWh of panels and some Thermal too. They did opt for a stove which they rarely use.

Culbokie Passive House Diary : https://pennyandmartin.wordpress.com/
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jonesy
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« Reply #10 on: November 03, 2015, 11:22:59 PM »

Have you considered going to someone like Scotframe, and getting them to up the insulation.  I heat our 100m2 bungalow (35cm fibreglass in the loft, 20cm walls & floor) with a single 7kw wood burner, using about 1.5stere which costs around 60 or would be about 400 in day rate leccy using panel heaters, and less with a heat pump. Key in hand cost about 1000/m2 5 years ago in France. Includes ground works, but not septic tank (2000 installed)
If you do decide to go off grid, bear in mind that a regular sparky would probably not immediately understand RE installations, if your original installer is on holiday etc. There are also on going costs for battery/inverter replacement.
Make sure the house designer knows the size of battery and likely hydrogen production to ensure safe ventilation.
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1.1kWp PV & SB1700. 7kW log burner.
knighty
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« Reply #11 on: November 04, 2015, 12:10:09 AM »

tbh, if you're grid connected, there's not much point in having a battery system, especially in a PassivHaus type build

you can still dump any excess power into the heat store

you'll be paid for exporting power if you export it or not... with 8kw of solar pv that export payment should cover the cost of any power you import

plus, there's no battery cost, battery maintenance, or battery replacement

if you spend 2000 on the battery alone, that'll buy you about 17,000kwh import from the grid (think running your kettle 24/7 for 2 years)

that's without buying chargers, inverters, fuses, cables, etc. etc.  (I'd guess close to another 2000 for decent kit)


I think batteries for people on grid are more of a hobby than a need or best use of cash

plus if your wife is disabled, you really want the most reliable system possible, which is the grid

- with possible a small/cheap generator for emergencies, or a little ups for anything crucial - but, if you've done ok without these so far, then I guess the off chance of a blackout isn't such a big deal
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DanielCoffey
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« Reply #12 on: November 04, 2015, 08:08:50 AM »

There are some very good idea in your replies folks - thanks.

The point about battery gassing is of acute interest in a PassivHaus. The air circulation is so tightly controlled that you simply cannot have an external vent in a battery room. If I wanted to use batteries that needed ventilation, they would have to go in an outbuilding that was outside the insulated envelope but this would expose them to unheated winter temperatures.

This also means that a wood stove is inadvisable. While it can be done, you have to take great care with flues, dedicated air supply and also finding a stove small enough. If the heat of a 7kW unit was dumped into the living space, it would vastly exceed the heating mandated by the PassivHaus standard (max of 10W per m2). If you actually managed to find a unit that put enough of the heat up the flue to be captured for the heat store, you would still risk overheating that one room.

I really do believe there is value in having a battery store even if grid connected, if for no other reason than to even out personal consumption. If I assume similar electricity usage in the new property as to what I am using now (which did not include space heating - that was on the gas), I would be buying roughly 4000 kWh a year from the Utility. Solar would of course offset a lot of that, especially since we would be at home during the day to schedule white goods. The PassiveHaus will have a background consumption to run its machinery 24/7 which will need to be catered for in the night. A medium battery store of roughly a couple of days usage would really help even that out.

Then, of course, as A.L. pointed out, even a good PV setup will not cover me in the winter even with batteries because of my location. I agree now that being off-grid from the outset is not reasonable to expect but it might be something I could work towards.

We will certainly require a generator for emergencies even with the grid because we will be in the Scottish Borders. January 2015 saw plenty of more rural homes without power for THREE consecutive days and it happens to some degree every year. The rural grid is not as reliable as a city and not as high priority for repair. We can do it if we plan properly now - PV, batteries, grid when it is there and generator when it isn't.

EDIT : I have an additional question... if I have a PV array larger than, say, 4kWh, how do I restrict flow back to the grid in the summer if the Utility Company limit what I am allowed to feed in?
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billi
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« Reply #13 on: November 04, 2015, 08:49:56 AM »

... a gasing  battery ( lead acid)  can be  placed in the garden -perhaps some insulation required -

@ Knighty , i would not  want those Grid units  ,  especially not  now ,  when  from 2016 , one can get 1.63p FiT  only  and pays about 10 times   for imported not green power

PV , battery and off grid Inverter is very reliable  ,  .... generator not so (prob only my experience )


Quote
EDIT : I have an additional question... if I have a PV array larger than, say, 4kWh, how do I restrict flow back to the grid in the summer if the Utility Company limit what I am allowed to feed in?
possibly , dont  have an inverter  feeding back , bigger than 4 kw , and the other part of the PV  via chargecontroler ...

But  it looks to me , that one should plan  without  FiT   payments   ....  , anyway

Billi
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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« Reply #14 on: November 04, 2015, 09:16:45 AM »

If you want a genny think about how you are going to safely store the fuel and for how long. Will it be an installed genny with auto start, or wheeled outside into a sheltered spot? Petrol goes off in a few months. LPG comes in handy containers, but would need swapping out every few years. Don't know about diesel.


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1.1kWp PV & SB1700. 7kW log burner.
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