Off grid viability

[Alexphd1]

After receiving a £13k grid connection for two houses (there is a decent amount of work involved), I was starting to wonder when does it break even to go off grid. Shopping wisely 13k can buy a lot of pv. 

Edited June 8, 2016 by Alexphd1

[Crofter]

PV is the easy bit. Storage is where it gets expensive. You can run a backup generator and live with the fuel costs of course.

 

£13k split between two houses isn't a show stopper- my connection was £2k for a single house and represents about 5% of my total budget.

[Jeremy Harris]

Batteries are one problem, the lack of winter output from PV is another. 

Batteries are very expensive and need replacing every 8 to 10 years (if looked after) and the capacity of the battery bank needs to be around 4 to 5 times the daily usage, so you're going to use pretty much all of that £13k on the first set of batteries for the two houses.  Then you need to look at another generation system for when the PV output is low (essentially around 4  months of the year).

As above, £13k doesn't seem OTT for two houses.  We paid £3.5k just to move a cable and pole, plus another £400 odd for the connection, just for one house.

[Alexphd1]

No I have mentally accepted the 13k no problem there. But say it was 25k would it be worthwhile going off grid?

 

[Crofter]

The thing is you are never going to have a 'normal' house off grid. You will have significantly higher outgoings due to battery replacement, diesel, and ongoing maintenance. Or you change your lifestyle to suit and give up the big TV and fridge.

So 'worth it' is a tricky one because you can't just look at a cheap site with no access to mains electricity and add a lump sum to cover the off-grid system.

 

 IMHO the most promising off-grid system would be hydro, but you would be very lucky to have a resource available.

[readiescards]

At £24k connection I'm looking at it very seriously and have got two companies keen to supply a one-stop solution (so no passing the buck if it fails) with both putting together detail studies.  

New battery solutions keep coming to the market and huge amounts of money are being invested in mega battery factories so It might not make sense today but very soon I think (hope!) it will.

[Nickfromwales]

11 minutes ago, readiescards said:

At £24k connection I'm looking at it very seriously and have got two companies keen to supply a one-stop solution (so no passing the buck if it fails) with both putting together detail studies.  

New battery solutions keep coming to the market and huge amounts of money are being invested in mega battery factories so It might not make sense today but very soon I think (hope!) it will.

Are you still aiming at off-grid for electricity? 

Just in case ;)

[Jeremy Harris]

There's a battery solution that is viable, lasts for decades, is extremely well proven and need very little maintenance, so batteries definitely aren't the key issue.  The real problem is that you will always have uncertainty in terms of generation capability, unless you just install a big generator.  PV will be all but useless for a third of the year, wind generation will vary massively from day to day.  Neither will give you a reliable minimum daily generation capability, so, as above, you need to adjust your life to match the unpredictable pattern of generation.  Pretty much everyone who live off-grid ends up with a generator, unless they have something like a reliable hydroelectric system. 

A friend in the next village was on-grid and went off-grid voluntarily around 15 years or so ago.  He bought an Indian-made single cylinder Lister diesel, coupled it to a generator and installed it in a concrete block built outhouse, complete with an underground 45 gallon oil drum silencer.  He uses the waste heat from both the water jacket and a home made exhaust heat exchanger to heat water that runs his central heating and hot water system, whilst the generator runs the big electrical loads.  He runs a 12V DC lighting system from batteries, but that's all the batteries run, so he doesn't have a big battery bank, and has avoided a fair bit of cost and maintenance as a consequence.

He drives an old Perkins engined diesel Land Rover pickup and does a twice weekly trip collecting waste cooking oil from two Chinese restaurants and a chip shop.  He processes some of the waste vegetable oil into biodiesel once a week or so, but the bulk of it is just filtered, pre-heated and used as-is to run the Lister. 

He's just adjusted his life style around not having power 24 hours a day, but only for the few hours a day when he runs the generator.  He does spend around 10 to 15 hours a week collecting and processing fuel, servicing the generator, etc, so it's very far from being a fit and forget system.  Then again, all off-grid systems require a few hours a week to maintain and keep optimised, as there's no solution available that is maintenance free, and there isn't likely to be one for a couple of decades, at a guess.

[Ferdinand]

On 8 June 2016 at 21:14, Crofter said:

PV is the easy bit. Storage is where it gets expensive. You can run a backup generator and live with the fuel costs of course.

 

£13k split between two houses isn't a show stopper- my connection was £2k for a single house and represents about 5% of my total budget.

What are the economics and compromises of having your own pumped storage system?

Say I have 50m fall on my land, what Potential Energy can I store in how big a pair of reservoirs, and what sort of turbine do I need to get the power out?

And will they make me turn it off if newts move in  ?

Ferdinand

[MarkH]

We're off grid now in a caravan on our plot and will remain so when the house is built. Our connection was going to cost £20k and more and it just seemed more interesting to go off-grid plus I have a strong aversion to overhead cables (just don't like the look of them, they chop the sky up). We have a measly 1000W of P.V., a 600w wind turbine and a 48V, 460amp/hr battery bank. Once the garage is finished we'll fit our currently ground-mounted PV to the roof and expand the array to 3kW. Our house is small and uncomplicated and we don't (and won't) have a 200 inch TV, we currently run a brilliant A+++ rated fridge that uses 65kWh a year.

Jeremy is right about PV in winter. Last November/December was very, very dark. Some record for lack of sunlight was broken at a weather station near here and one day we only generated a ridiculous 35w/hr. We got to the point where we had to borrow a genny to avoid battery damage and considered getting either a genny or a wind turbine with the turbine winning. Once the turbine was installed we were fine, winter weather is rarely dull AND calm. Whilst turbines need a good site (ours is OK, not perfect) and don't do much in lighter winds they do provide 24 hours a day of juice when the wind is blowing and that makes up for a lot. Our turbine has been shut down for weeks now - we don't need the power and we have slight issues making the solar reg and diversion controller play well together - but it was a good buy and certainly preferable (for us) to a generator.

I'll be interested to see where battery tech goes in the next few years. Something better that our flooded cells is likely to come along and if it doesn't I'm likely to look for a better solution. It's a minor but regular pain in the arse maintaining them.

Edited June 12, 2016 by MarkH
voltage

[Ferdinand]

Hmm.

Quickly calculations suggest that emptying an Olympic swimming pool 3m deep with a head of 10m over a 24 hour period will generate a continuous 15kw, assuming an 85% end to end efficiency on the water to electricity generating system.

So over a week it will be 2kw if it is emptied over the 7 days.

Big lake required. But not impossibly big if you own the landscape.

So I need a very big lake and a fishing business or landing facility for seaplanes.

Suspect I would require more than a minidigger.

Ferdinand

[Ferdinand]

And such a system could get a FiT subsidy of about £30 ukp for the 360kwh you could generate each day.

Which is double the FiT for solar, so if you used your solar to pump the water up with an efficiency of more than 50% or so ... You could potentially just about break even rather than fleecing yourself if you ignore the capital cost.

Ferdinand aka Sisyphus.

[Crofter]

6 hours ago, Ferdinand said:

What are the economics and compromises of having your own pumped storage system?

Say I have 50m fall on my land, what Potential Energy can I store in how big a pair of reservoirs, and what sort of turbine do I need to get the power out?

And will they make me turn it off if newts move in  ?

Ferdinand

Reminds me of this:

https://what-if.xkcd.com/91/

[SteamyTea]

Gas or Diesel generator, use the waste heat for DHW and space heating.  Get a few batteries and some PV.

We did have a thread on this a while back on the 'other places'.  But may be worth a revisit.

[Nickfromwales]

What sort of temperatures can you expect the genny cooling system water to produce? Eg I'd have firstly thought about heating a very big primary TS ( adjacent to the genny ) as an additional heat battery, say 1500-2000 litres, then, when the TS is fully charged, would it be better to glean the heat from the TS and export it to the cylinder in the house or would it be better to use a diverter valve to send the heat directly to a secondary TS or UVC ( via a dedicated coil )? They'd have to be hydraulically separated I assume as the external arrangement would need antifreeze / inhibitor etc. 

[Jeremy Harris]

2 hours ago, Nickfromwales said:

What sort of temperatures can you expect the genny cooling system water to produce? Eg I'd have firstly thought about heating a very big primary TS ( adjacent to the genny ) as an additional heat battery, say 1500-2000 litres, then, when the TS is fully charged, would it be better to glean the heat from the TS and export it to the cylinder in the house or would it be better to use a diverter valve to send the heat directly to a secondary TS or UVC ( via a dedicated coil ? They'd have to be hydraulically separated I assume as the external arrangement would need antifreeze / inhibitor etc. 

70 to 80 deg C is OK, anything lower than about 60 deg C and the big single cylinder Lister will start to soot up, more so when run on WVO.  A big thermal store is a must, as is a switchable thermal dump for when you need to run the genset but don't need the heat (in summer, for example).

The chap in the next village has his Lister, biodiesel manufacturing kit and WVO store in a concrete block house half buried into the hillside (it was the old air raid shelter for his house).  He runs hot water from there to a big thermal store in the house and has a thermostatic changeover valve that switches two large radiators on in the cooling circuit when the thermal store is up to temperature.  One of these is inside the blockhouse, with an external opening panel to let the heat out in summer, the other is painted and fitted to the outside wall.

One thing he found was that he needed to restrict the primary flow around the engine, so that he could run the engine at a near-constant 80 deg C or so, irrespective of the thermal store temperature.  I can't remember how he has done this, but have a feeling he uses a bypass system with a car-type thermostat to keep the engine hot all the time.  I do know that the thermal store primary only runs on a thermal syphon, even though there's a massive pipe run, and that seems to work fine.  IIRC, his big Lister can provide around 5 or 6 kW of heat into the water when it's running under load, and seems to be able to heat his fairly old (I'd guess 1930's) three bedroom house OK, although he has added insulation and does things like fit sheets of PIR foam board over unused doors and windows in winter (he lives on his own.....................).