I response to my other threads here's an outline of our off-grid power
system.

A couple of years ago now I asked some questions here about the costs of
running diesel generators for domestic power. Some of the numbers I
got back almost put me off buying the house, but I, with my partner, did
buy the place.

The power set-up as we bought it comprised three diesel generators, all
Listers of different power outputs, 1.75kVA, 3.5kVA and 11kVA. This
system had evolved over the years.

Historical side note: We have recently made contact with the, now, 94
year old woman who lived in the house from the 30s through to the 70s.
She and her husband put in the two lower powered Listers. She, in fact,
poured the concrete floors we still have today. Perhaps I should get her
back to do the tower foundations!

The house could run directly from any of the generators, the choice of
generator was based on what you wanted to do. The lowest was fine for TV
etc., the next for a washing machine, the largest was put in by later
owners to run a blacksmith's forge.

The generators were used only when needed, evenings, weekends. Thus we
don't use a video, say, and we have a gas (lpg) fridge---came with the
house.

In addition to the diesel system the previous owners added a couple on
small wind turbines (one 50W, one 400W) on the gables of an
outbuilding., and a couple of small battery banks with a 600W inverter.
This system allowed for lights being used in the middle of the night but
not much more.

The whole system is very ad hoc with lots of switches being used
depending on what you need to use. So, we decided last year to look at a
more modern system or going on the grid.

Going on the grid would cost around 20K. We quickly realised we could
spend a lot less than that and have a system based on solar and wind
power. We then had to decide whether to go the DIY route or get a
supplier fitted system. Luckily we have a company that does renewable
systems just a few miles away, which makes for good service. Their quote
for a full system was about 15K but as it is an 'approved' system we can
get 3-4K of grants to cover some of that.

The DIY route would get any grants and the kit would attract 17.5% VAT
instead of the 5% we paid. However, there's probably not much in it in
terms of the hardware costs after the sums.

The system we went for, based on our location and needs, comprises 6
110W Solar PV panels, one Whisper H40 (900W) windcharger, a very clever
3.3kW inverter and a bank of 16 6V deep-cycle batteries. In addition
there's a solar controller and a wind controller in there. The inverter
is also wired to the 11kVA Lister as its back-up charger. It can also
patch us straight through to the genset if we use very heavy loads.

All the wiring has been done by the company we got in but the
groundworks and preparations are DIY.

The first stage was just the inverter, batteries and genset wiring. This
immediately made a tremendous difference as the genny was turned on
just for charging for 2.5 hours every 3 to 5 days.

The solar was added next, on the shortest day of all days! We have been
surprised at its effect. Even at this time of year it is delaying the
need for diesel charging by a few days. The last few days have had
record daily inputs of over 60Ah. This is more than enough to cover our
normal nightly demand.

The final part is the wind turbine. The charger we have chosen is
designed to work in high wind areas and has been used in similar
locations to ours (exposed!) in the north of England. We are predicting
that the diesel generator will be used very little once the turbine is
up and running. In fact we may have to make a decision as to whether to
divert its dump load to some use other than heating the inverter
shed---possibly to a secondary immersion heater.

We then have to decided what to do with the old system. The Air 303 did
suffer some damage in recent storms and an electrical storm fried out
600W inverter. The new inverter is protected from this and the new
turbine is better suited to our conditions and will be better installed,
though obviously there are no guarantees.

We still feel we need to hang on to the 3.5kVA genset as we like the
idea of backup systems. We will probably try to sell the smallest
generator, it was built in 1960 so it may be of interest to a collector.

We may used the older wind/battery system to run a DC lighting circuit
for the outbuildings with a small inverter there for emergencies.

In fact this raises a final question about the recently discussed
regulations on electrical work. Does it apply to a situations such as
mine on the other side of the 'meter'? We don't actually have a meter
but how does it apply to the old inverter system itself?

Colin

Colin Blackburn wrote:

A most interesting piece on living 'off the mains.'

This is probably preaching to the converted, but if you haven't already
visited the Centre for Alternative Technology at Machynlleth then get
yourself over there ASAP, as there is much to be learned and many brains
there to be picked. (And some very serious batteries to be viewed.)

In fact this raises a final question about the recently discussed
regulations on electrical work. Does it apply to a situations such as
mine on the other side of the 'meter'? We don't actually have a meter
but how does it apply to the old inverter system itself?

BS 7671 certainly applies. There's a whole section (Section 551)
applicable to "generating sets" - the definition of which extends beyond
rotating machinery and so includes your inverter, PV cells and
batteries. It covers the ELV sources (50 V AC or 75 V DC) as well as
'mains voltage' stuff. Parts, but not all, of it are concerned with
interfacing safely to a public supply - interlocking, separate earthing
and so on. These won't apply to you, but there is much that does,
mostly concerned with the co-ordination of protective devices (i.e.
fuses and circuit breakers) and fault levels, to ensure that bad things
(like cables catching fire) don't happen if there's a short-circuit
somewhere. Earthing bonding and shock protection are also covered.

Whether Part P applies is a moot point: The SI says:

"'electrical installation' means fixed electrical cables or fixed
electrical equipment located on the consumer's side of the electricity
supply meter;"

If there's no meter there can be no consumer's side, so you could argue
it doesn't apply. Dunno whether that would stand up in court though.

--
Andy

You say 16.6v? You mean 13.6 I guess? which are more commonly called
12v batteries, even though theyre not exactly..

We may used the older wind/battery system to run a DC lighting circuit

for the outbuildings with a small inverter there for emergencies.

why not feed it into the main dc system?

You must have wired over the washing machine thermostat so it doesnt
heat electrically.

BTW are you using the gen exhaust heat to heat the house? If the gen
runs much in winter, you get around 20kW out of an 11kW gen exhaust, at
full tilt.

Is all your lighting 12v? 12v loads are generally more efficient than
running things on 240, as theres no invertor losses in the way..

If you want to inevst a few more hundred, solar flat plate space
haeting is an excellant payer.


NT

You say 16.6v? You mean 13.6 I guess? which are more commonly called
12v batteries, even though theyre not exactly..

We may used the older wind/battery system to run a DC lighting circuit

for the outbuildings with a small inverter there for emergencies.

why not feed it into the main dc system?

You must have wired over the washing machine thermostat so it doesnt
heat electrically.

BTW are you using the gen exhaust heat to heat the house? If the gen
runs much in winter, you get around 20kW out of an 11kW gen exhaust, at
full tilt.

Is all your lighting 12v? 12v loads are generally more efficient than
running things on 240, as theres no invertor losses in the way..

If you want to inevst a few more hundred, solar flat plate space
haeting is an excellant payer.


NT

wrote in message
oups.com...
BTW are you using the gen exhaust heat to heat the house? If the gen
runs much in winter, you get around 20kW out of an 11kW gen exhaust, at
full tilt.

What's the best way to do this ? I assume some sort of heat exchanger but
are there ones that you can place on the exhaust without a) disintegrating
or b) messing up the running of the genny ?

On 2 Feb 2005 12:06:20 -0800, wrote:

BTW are you using the gen exhaust heat to heat the house? If the gen
runs much in winter, you get around 20kW out of an 11kW gen exhaust,
at full tilt.

With just the solar input the OP said the gen only runs for 2.5hrs
every 3 - 5 days. Once the wind gen gets turning it'll be even less
often. The invertor is 3.3kW so should cope with most normal loads
without (auto starting?) the genset.

I sort of wonder if 11kVA isn't a bit on the large side but I guess if
the invertor drops everything over to the genny for loads over 3.3kW
it's not so bad. Bit daft running up an 11kVA genny for an extra few
hundred watts...

I'm actually quite curious as to how this clever invertor does it's
thing. Say you put something on that means the total load is greater
than 3.3kW, what happens whilst the genset starts and comes online?

--
Cheers
Dave. pam is missing e-mail

I'm actually quite curious as to how this clever invertor does it's
thing. Say you put something on that means the total load isgreater
than 3.3kW, what happens whilst the genset starts and comes online?

We wait to hear... there are not many options though. It either current
limits, causing Vout to drop, shuts down if its a poor design, or
switches off some loads.


NT

I wonder if you looked at the gas bottle solar engine at:
http://www.amasci.com/freenrg/minto.html

I've never played with one, but on the surface it looks like it could
produce serious power for peanut money. Anyone know anything about it?
NT

Thanks for this Colin, Much appreciated.

How does the VAT thing work? Why would you have to pay 17.5% VAT if you
were DIY'ing it?

Which Inverter are you using?

Also, how much are the installation costs? (If that isn't too cheeky a
question)
It is crazy that they won't allow DIY installation for grants as DIY
reduces costs and would therefore encourage more installations. f'n'
government organisations!.

Cheers,

Alan.

Please keep us updated on how you get on with it.

It is crazy that they won't allow DIY installation for grants as DIY
reduces costs and would therefore encourage more installations. f'n'
government organisations!.

I suspect because they think it is too easy for you to fleece them, or not
complete the installation.

Christian.

wrote:
You say 16.6v? You mean 13.6 I guess? which are more commonly called
12v batteries, even though theyre not exactly..


We may used the older wind/battery system to run a DC lighting circuit


for the outbuildings with a small inverter there for emergencies.


why not feed it into the main dc system?

We don't have a main DC system. There is a small DC system that runs to
the garage and workshop. There is a DC line to the house but it is used
solely for an alarm system.

You must have wired over the washing machine thermostat so it doesnt
heat electrically.

Nope. The washing machine will start quite happily off the inverter.
When the load rises, ie the heater comes on, the genset kicks in to take
over the high load. The inverter controls this. It then leaves the
genset on for a period of time after the high load has dropped this is
to prevent the genset having to start up again. The inverter will
happily grab use of the genset for charging the batteries during this
period.

However, at the moment we will often switch over manually to the
middling generator and do the washing with that. This is in part because
the generator needs exercising from time to time.

BTW are you using the gen exhaust heat to heat the house? If the gen
runs much in winter, you get around 20kW out of an 11kW gen exhaust, at
full tilt.

No we're not but it is certainly something to think about. The generator
is an air cooled Lister in an outbuilding a few metres away from the
house so I don't know how feasible this would be. The exhaust at present
discharges through a hole in the wall and warms the sheep in the
adjacent field!

Is all your lighting 12v? 12v loads are generally more efficient than
running things on 240, as theres no invertor losses in the way..

The house is wholly 240V AC (except for the alarm. This is historical
as the original occupants used direct generator power only. Once the
wind power is up and running we are likely to, generally, have an excess
of power so the inverter losses would be insignificant. Certainly not
worth the additional costs of putting a DC line across to the house and
wiring up a DC lighting circuit.

If you want to inevst a few more hundred, solar flat plate space
haeting is an excellant payer.

We are hoping to review our whole heating set-up later this year, once
we have a feel for our electricity situation, so any suggestions are
welcome.

Colin

Alan wrote:
Thanks for this Colin, Much appreciated.

How does the VAT thing work? Why would you have to pay 17.5% VAT if you
were DIY'ing it?

If you buy the parts they are just ordinary bits that have ordinary VAT.
If you buy "a power system" then it attracts the same VAT rate that
heating and power fuels do.

Which Inverter are you using?

It's a Trace pure sine wave inverter. I can't recall the model number
but it is rated at 3.3kW and takes 24V input.

Also, how much are the installation costs? (If that isn't too cheeky a
question)

I'd have to get back to you on that one. To be honest whatever they were
I'm grateful! One of the guys spent the best part of two days trying
unsuccessfully to wire in the ignition box for our generator. The
ignition box was an unnamed, probably home made, thing that used a key
and push button system. He went home, had a eureka moment and then came
back and sorted it out. It isn't a job I could have done at all.

Colin

Christian McArdle wrote:
It is crazy that they won't allow DIY installation for grants as DIY
reduces costs and would therefore encourage more installations. f'n'
government organisations!.


I suspect because they think it is too easy for you to fleece them, or not
complete the installation.

Probably. Though the grants are authorised on quotes but are paid on
completion of the works. In our case the installer was able to verify
that the works had been completed and we were able to verify that the
installation was working and that we were happy with it.

Colin

Cheers Colin, much appreciated.

I still don't get it though - If I pay someone to fit my "power
system", it is 5%, if I buy it from the same people and fit it myself,
it is 17.5% - mmm - anyone would think the government doesn't want
renewable energy. When I eventually get round to doing mine, I will
have to have a chat with my accountant. I will also contact clearskies
and register my complaint at their being DIYist. There must be ways for
them to prevent fraud. If I buy the kit from a registered supplier and
they certify this then surely that should be enough.

I'm allergic to tradesmen hence the question about costs.

Thanks again,

Alan.

Colin Blackburn wrote:
wrote:

We may used the older wind/battery system to run a DC lighting
circuit
for the outbuildings with a small inverter there for emergencies.

why not feed it into the main dc system?

We don't have a main DC system. There is a small DC system that runs
to
the garage and workshop. There is a DC line to the house but it is
used
solely for an alarm system.

Normally one has both 12v and 240v, as putting some of the loads on 12v
reduces the necessary invertor rating and eliminates the invertor power
losses for the 12v loads. 240 only systems cost noticeably more.


You must have wired over the washing machine thermostat so it
doesnt
heat electrically.

Nope. The washing machine will start quite happily off the inverter.

I think thats usually regarded as a bit of a no-no with solar and wind
power. To use the leccy for heating increases the system cost
unnecessarily. I guess its a case of well, since youve got a genny...

The good news is that if in future you make the setup more efficient by
addressing this, you'll have some more leccy to play with. This will
all help to get you off the generator hopefully.


BTW are you using the gen exhaust heat to heat the house? If the
gen
runs much in winter, you get around 20kW out of an 11kW gen
exhaust, at
full tilt.

No we're not but it is certainly something to think about. The
generator
is an air cooled Lister in an outbuilding a few metres away from the
house so I don't know how feasible this would be. The exhaust at
present
discharges through a hole in the wall and warms the sheep in the
adjacent field!

I would expect very feasible - if you continue using the gen anyway.
When youre loading it at 3kW you're going to get somewhere in region of
6kW out of that exhaust pipe. An exhaust heat exchanger is a fairly
elementary thing to make.


Is all your lighting 12v? 12v loads are generally more efficient
than
running things on 240, as theres no invertor losses in the way..

The house is wholly 240V AC (except for the alarm. This is historical
as the original occupants used direct generator power only. Once the
wind power is up and running we are likely to, generally, have an
excess
of power

that would be a most unusual situation if you didnt use the genny.


so the inverter losses would be insignificant. Certainly not
worth the additional costs of putting a DC line across to the house
and
wiring up a DC lighting circuit.

the solar panels are remote as well? I dont know anything about your
alarm setup, but even a wimpy alarm cable can be used to supply a
steady current 24/7 to a secondary house battery, enabling some amount
of 12v load use. Alarm cable is very low current rated, but it has
several cores and can charge that battery 24/7, so it might be usable.
But with what you spent I imagine you dont want to bother with 12v
stuff.


If you want to inevst a few more hundred, solar flat plate space
haeting is an excellant payer.

We are hoping to review our whole heating set-up later this year,
once
we have a feel for our electricity situation, so any suggestions are
welcome.

If you want to play, I'd also look into a tracking heliostat to provide
DHW and partial CH too. If youre into diy theyre quite low cost, and
can produce quite serious power output, as hot water. Redrok.com.


NT

wrote:
You say 16.6v? You mean 13.6 I guess? which are more commonly called
12v batteries, even though theyre not exactly..

no he said 16 6V which I read as 16 * 6V = 96V
I assume the inverter uses that to generate 240V AC

In article , "John Stumbles"
says...
wrote:
You say 16.6v? You mean 13.6 I guess? which are more commonly called
12v batteries, even though theyre not exactly..

no he said 16 6V which I read as 16 * 6V = 96V
I assume the inverter uses that to generate 240V AC

16 x 6V batteries powering a 24V inverter

Rob Morley wrote:
In article , "John Stumbles"
says...

wrote:

You say 16.6v? You mean 13.6 I guess? which are more commonly called
12v batteries, even though theyre not exactly..

no he said 16 6V which I read as 16 * 6V = 96V
I assume the inverter uses that to generate 240V AC


16 x 6V batteries powering a 24V inverter

Yes, thanks. They are wired as four serial banks of four in parallel
together.

Colin

wrote:

Normally one has both 12v and 240v, as putting some of the loads on 12v
reduces the necessary invertor rating and eliminates the invertor power
losses for the 12v loads. 240 only systems cost noticeably more.

They probably do if one is running on the edge but even with only the
solar set up, in winter, we have no problems finding enough power
(ignoring the washing machine for now) for normal needs. There are only
two of us, we have low energy lighting, we don't normally run a central
heating pump, etc.. In that case the losses via the inverter really are
negligible *for our needs*. Certainly not worth investing in a new
wiring circuit in the house. If at some point in the future we have the
house rewired---it is on the cards as like everything else it has been
piecemeal in its development---then we will consider putting in a DC
circuit at the same time.

I think thats usually regarded as a bit of a no-no with solar and wind
power. To use the leccy for heating increases the system cost
unnecessarily. I guess its a case of well, since youve got a genny...

Regarded as a no no by whom? As I say, it is not a concern with our
set-up at present. If we address our issues of water heating---at the
moment that is by an oil-fired Rayburn---then we may look at using the
hot water directly but as it is we do one load of washing a week and
that exercises either generator, both of which we would have to exercise
at some point anyway.

The good news is that if in future you make the setup more efficient by
addressing this, you'll have some more leccy to play with. This will
all help to get you off the generator hopefully.


The house is wholly 240V AC (except for the alarm. This is historical
as the original occupants used direct generator power only. Once the
wind power is up and running we are likely to, generally, have an

excess

of power


that would be a most unusual situation if you didnt use the genny.

Eh? Do you know how much electricity we use then? We live in an area
with strong wind almost every day. There is very rarely a calm day. We
have very open skies when it is sunny. I will be more than happy to post
back here saying I was wrong but looking at the inputs and outputs on
the inverter even now it is hard to imagine us being short of power.

the solar panels are remote as well?

Remote to what? The panels are ground mounted in the garden. The feed
into an outbuilding which contains the batteries and inverter charging
system. Power is then delivered to the house via an underground cable.

I dont know anything about your
alarm setup, but even a wimpy alarm cable can be used to supply a
steady current 24/7 to a secondary house battery, enabling some amount
of 12v load use. Alarm cable is very low current rated, but it has
several cores and can charge that battery 24/7, so it might be usable.
But with what you spent I imagine you dont want to bother with 12v
stuff.

As explained above. I don't think it is an issue worth addressing at
present. Also, the DC alarm cable comes from a completely separate
outbuilding which is not directly connected to the new supply system.

Colin

Ah, a 24v system. Those work nicely with the 3 wire system, but its
moot if youre all 240v.


NT