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Topic Title: Domestic electrical generator
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Created On: 27 June 2013 01:08 PM
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 27 June 2013 01:08 PM
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sosa

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Hi all first post here, i'm an electrician who's been asked to price a job at a remote farm house, with the problem being that currently there is no electrical supply to the building and to have one put in is going to cost £40,000+ and so i've been asked about the idea of installing a generator now as i don't have a great deal of experience with this i was wondering if anybody new any contacts so that i could get a price off them?
 27 June 2013 02:12 PM
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Legh

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A remote farmhouse - sounds like Scotland to me.
Surely there are initiatives abroad to encourage the installation of some form of alternative energy generation?

The first that springs to mind is something along the lines of a straw burner with a heat exchanger coupled to a solar water heater.

Now for the electrical generation, what about PV, water or/and wind.?

Lots of that up there and probably down here as well - lol

Legh

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Why do we need Vernier Calipers when we have container ships?

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"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 27 June 2013 03:01 PM
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perspicacious

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Welcome sosa

"Now for the electrical generation, what about PV, water or/and wind.?"

With no export then?

Regards

BOD
 27 June 2013 03:39 PM
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Legh

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Originally posted by: perspicacious

Welcome sosa

"Now for the electrical generation, what about PV, water or/and wind.?"

With no export then?

Regards

BOD


Where to ?

I can't see a FIT up here.
I think, this one sounds as though its going to be self sufficient

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 27 June 2013 04:22 PM
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slittle

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Diesel generator running on biofuels can be quite economic I believe.

Back to the OP, I'd say your client needs to look at the capital and running costs of the generator against the 40k investment to get a supply there.

A decent set (bearing in mind it's got to run at least 12-18 hours a day) is going to be the thick end of £10K, add to that all the servicing costs and fuel and all of a sudden your £40k for the DNO connection isn't so bad.

You've already mentioned it is remote, that means a long trek when the generator is out of fuel or has a blocked filter. The other way, if the power disappears those nice people in vans turn up and fix it for free !

Stu
 27 June 2013 05:56 PM
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perspicacious

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The number of farmers who say that it is cheaper for them to run a generator than it is buying off the grid still amazes me Even more so when they haven't got a kWh meter connected to their gen-set.

At best, you've got the equivalent of 11 kWh in a litre of diesel oil and then you've got to factor in the losses. So if we start with a litre of red at 70p that energy costs 6.36p/kWh. Next on a larger 400 kVA gen-set running at 95% output you're probably looking at a maximum of 40% efficiency of the engine so each crankshaft kWh is now 15.91p/kWh and then alternator at say being 90% efficient takes this up to 17.67p/kWh. These figures will be even worse if you're looking at part load running and far worse again for the 12 kVA domestic set. If you dig deep enough, you can find the actual figures from the engine and alternator manufacturer's sites. The 400 kVA figures I've put in above are the distant, faded memory of a John Deere powered 400 kVA set I looked at. You could be looking at 30p/kWh yet alone the capital cost, maintenance and eventual replacement as Stu says.

Regards

BOD
 27 June 2013 06:51 PM
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Legh

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@BOD
Before you can compare the running costs you'll need to factor in the capital costs for both DNO supply against any self sufficient methods.

Now if the OPs client lives near a river or on uplands then nature has supplied the raw energy and it would then be down to a feasibility study.

Legh

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Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 27 June 2013 07:58 PM
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perspicacious

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"near a river or on uplands then nature has supplied the raw energy"

And 1 hp is 550 lbs raised 1 foot in 1 second.....That's a lot of water fall

Regards

BOD
 27 June 2013 08:12 PM
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perspicacious

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1st floor bath emptying in 1 minute equates to 35 W.

Regards

BOD
 27 June 2013 09:28 PM
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broadgage

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In a remote place, the mains electricity supply is not only very expensive to have put on, but may prove less reliable than hoped for.
So a generator may be needed anyway for standby purposes.

If the AVERAGE demand is less than about1KW, and the peak demand is less than 5KW, then it may make more sense to avoid a generator and use wind or solar with a battery bank instead.

If they go for a generator, then the wiring is much the same as for an installation supplied from the public mains.

It would be advisable to also install a 12 volt battery powered lighting circuit in order that basic lighting can be used without running the engine.
 28 June 2013 04:19 AM
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Legh

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Originally posted by: perspicacious

1st floor bath emptying in 1 minute equates to 35 W. [IMG][/IMG]

Regards

BOD[IMG][/IMG]


Sufficient to run LED lights through a rechargeable battery, excluding minimal losses and down time for maintenance.

So one bath equivalent a day for various cleaning activities may provide enough light for a couple of hours or so.

Just the beginning of not looking so unreasonable as one might first suppose, don't you think ?

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."

Edited: 28 June 2013 at 04:37 AM by Legh
 28 June 2013 08:44 AM
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broadgage

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The economics of useing a diesel generator as the only or main source of electricity also become a great deal more favourable if the considerable waste heat from the engine can be put to good use.

As a very rough guide, a domestic sized diesel generator will produce at least 2KWH of useable heat for every KWH of electricity.

From each liter of diesel fuel, I would expect very roughly 3KWH of electricity, 6 or 7 KWH of useable heat, and about 3KW of not readily useable heat (exhaust gases, alternator losses, heat radiated from engine block etc)

It is a fairly simple matter to plumb standard central heating radiators into the engine cooling system via a heat exchanger.
Underfloor heating is better as it retains heat and avoids undue fluctuations in space temperatures according to load.

Also if a generator is to be used, careful planning is advisable regarding electricity use so as to minimise generator running hours and ensure that it is at least 50% loaded most of the time that it is running.
 28 June 2013 09:49 AM
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Legh

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@broadgage

I'm with you on this one. but have not considered the idea of recycling the heat generated from the generator itself.

I've witnessed a straw burner coupled up with a solar water heater and Rayburn providing heating and water for a large farmhouse. The electric is still on the public supply.

I also remember some chap who connected the back boiler plumbing of an Aga in series with another wood burning stove. Probably enough pressure produced in the pipes to drive a small turbine -lol

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 28 June 2013 10:21 AM
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OMS

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It's not that easy guys - unless you want gross overheating then you need to be dumping a load of heat in summer if you want to see in the dark or cook.

From experience you are going to need a lot of bulk water storage, a mixing system (you can't run engine temp water into UFH), a dunp radiator (probably with fan cooling) and a whle host of other things.

It can be done - I've a mate who lives "off grid" and he uses an old ford fiesta diesel engine to run his alternator and collects the heat into about 10,000 litres of thermal store. He also has a home brew 2m wide overshot water wheel and an old traction lift gearbox to run an additional alternator

He also has a a number of deep cycle submarine batteries - old and knackered now, second hand when bought and fearsomely expensive to replace with modern LiFE or LiON cells.

The biggest problems with off grid are managing lifestyle - if you expect to live as you would on grid, then the plant, equipment and effort are way beyond any resonable payback time.

As BoD alluded to - other than carbon fuels, the bulk energy density of water, air or sunlight is pretty appaling - so you need loads of it to do anything sensible - and to create an output that you can store.

If it was that easy, we'd have a grid efficiency a little better than 40% wouldn't we - and that's accounting for the grid to act as the storage - without it, it's basically a non starter in any economic term.

It can be done - but you need to have the lifestyle - and that's rare.

Regards

OMS

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 28 June 2013 10:36 AM
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perspicacious

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1st floor bath emptying in 1 minute equates to 35 W

Sufficient to run LED lights through a rechargeable battery, excluding minimal losses and down time for maintenance.
So one bath equivalent a day for various cleaning activities may provide enough light for a couple of hours or so.
Just the beginning of not looking so unreasonable as one might first suppose, don't you think ?


Spread over 1 hour is 0.58 W and 2 hours 0.29 W so by the time you factor in losses, you'd be lucky to get half these steady outputs so I don't think 0.15 W for two hours would be reasonable.....

Regards

BOD
 28 June 2013 12:11 PM
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broadgage

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The last diesel engine heat recovery that I was innvolved in was done as follows.

The hot water from the engine was pumped through an engine cooling radiator and a large domestic type hot water cylinder.
A standard engine cooling thermostat bypassed the flow past the radiator and the cyclinder until the coolant reached 60* degrees, so as to allow the engine to quickly reach operating temperature.
This water circuit contained standard engine antifreeze, and was maintained under slight pressure by a header tank.

The radiator was cooled by an electric fan that only operated when the water temperature exceeded 85* degrees.

The coil in the hot water cylinder was connected via a standard domestic heating pump to underfloor heating, a 3 port mixing valve being employed to keep this water at 45* in line with normal underfloor heating practice.

*temperatures from memory, may not be exact.

Another installation in which I was innvolved was a large standby generator for a big house, 100 amp 3 phase, so as to give nearly 100% backup for the public supply .
In this case, the engine waste heat was dumped into the swiming pool as being neater and simpler than a large external radiator.
The intention not being so much as to heat the pool, as to get rid of the waste heat.
The owner has however found it worthwhile to run the generator even when the mains is available, in order to heat the pool.
I would estimate that the heat input to the swiming pool was at least 100KW. Not enough in mid winter, but it certainly extends the swiming season a fair bit.
 28 June 2013 04:33 PM
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Legh

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Originally posted by: perspicacious

1st floor bath emptying in 1 minute equates to 35 W

Sufficient to run LED lights through a rechargeable battery, excluding minimal losses and down time for maintenance.

So one bath equivalent a day for various cleaning activities may provide enough light for a couple of hours or so.

Just the beginning of not looking so unreasonable as one might first suppose, don't you think ?


Spread over 1 hour is 0.58 W and 2 hours 0.29 W so by the time you factor in losses, you'd be lucky to get half these steady outputs so I don't think 0.15 W for two hours would be reasonable.....

Regards

BOD


From what I can remember about the power consumption of indicator LEDs is that they drop 0.6V with a current flow of between 4 -18mA.
So that would give a power consumption of something in the order of 10mW.

With the correct type of reflector and lens and a little magic you would end up with something similar to one of those fancy miniature spot lamps from CW.

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 01 July 2013 02:57 PM
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AJJewsbury

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Have a look around - I have seen adverts for off-grid systems that are a kind of hybrid UPS - it runs the generator at full efficiency to charge the batteries, then shuts the generator down and supplies the load from battery via an inverter, until the battery gets low again - that way you get a stable supply, maximise the generator efficiency and avoid noise at low consumption times (e.g. overnight with only the freezer and a few standby-boxes running). Maybe some versions would be able to accept other SSEG too (PV, hydro or whatever's to hand).
- Andy.
 02 July 2013 12:16 PM
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AJJewsbury

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