Solar electrical water heating

I'm interested in reducing my fuel/carbon foot print and estimate that most goes on heating water.I have a farly normal fully pumped gas HW/ CH system with a HW tank, with two insulation jackets. Tank stat set at 55

A number of neighbours have gone over to Solar for hot water using the vacuum collector system and it seems a very good idea, however the cost of significant (circa =A33K) and requires a fair bit of specialised plumbing, for example a new tank with 2 coils.

I wondered about the cost/benefit of using solar electricity to heat water.Sounds crazy but my tank already has a top-up immersion heater and I wondred if this could be run from batteries. Looking on ebay I noticed that there are 12/24v heaters than can produce 500 watts and can replace an existing immersion heater .

I know that the specific heat capacity of water is very high so heating a water tank would require a lot of fully charges batteries and hence panels to charge them. However every degree you can heat the tank for free is one that does'nt need gas right ?

Electric also has some advantages. It might be possbile to do this in an incremental way thus spreading the cost i.e adding panels/batteries as you can afford them.It could also incoporate a wind charger to get some power in all light conditions i.e at night. Finally the plumbing might not need changing at all to incorporate this meaing this falls within the realm of a purely electrical installation + some mechanics to fit the panel/ wind charger

I understand that electro voltaics are pretty inefficient, but I wondered if this approach might be cheaper or even more cost effective than the full solar hot water panel system ?

Reply to
jives11
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Forget it. You will never recouple the cost. It is quite easy to do a solar hot water system. A two coil tank is a waste most of the time the water from the sun will not be hot enough. A better solution is to use a second tank. The first tank just a normal tank ideally with a 28mm coil is used to preheat the water and the output from this goes into the feed of the tank connect to the boiler. This system is cheap to implement you can do it with an old radiator painted black and insulated in a box with a glass front. Provided the radiator is below the tank you won't even need a pump because the action of heating the water will do the work.

Better still leave this god forsaken country behind and go somewhere warmer where fuel costs aren't a problem.

If you are interested in doing your own eco projects there are some nice books that some eco centre does in wales. I forget the name. Do I few searches on the internet and I think you'll fine it.

Reply to
david.cawkwell

Don't forget this is a diy group. £3k sounds a but steep.

Look at

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reckon you could buy the parts for a rudimentary solar HW setup for under £1500 including collectors, tank, pumps and controls.

Reply to
Vortex2

Plenty of bargains in Spain?

Reply to
Bruce

I think you mean the Centre for Alternative Technology (CAT).

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Reply to
Piers Finlayson

A number of neighbours have gone over to Solar for hot water using the vacuum collector system and it seems a very good idea, however the cost of significant (circa £3K) and requires a fair bit of specialised plumbing, for example a new tank with 2 coils.

I wondered about the cost/benefit of using solar electricity to heat water.Sounds crazy but my tank already has a top-up immersion heater and I wondred if this could be run from batteries. Looking on ebay I noticed that there are 12/24v heaters than can produce 500 watts and can replace an existing immersion heater .

I know that the specific heat capacity of water is very high so heating a water tank would require a lot of fully charges batteries and hence panels to charge them. However every degree you can heat the tank for free is one that does'nt need gas right ?

Electric also has some advantages. It might be possbile to do this in an incremental way thus spreading the cost i.e adding panels/batteries as you can afford them.It could also incoporate a wind charger to get some power in all light conditions i.e at night. Finally the plumbing might not need changing at all to incorporate this meaing this falls within the realm of a purely electrical installation + some mechanics to fit the panel/ wind charger

I understand that electro voltaics are pretty inefficient, but I wondered if this approach might be cheaper or even more cost effective than the full solar hot water panel system ?

------------------------------------------------------------------------------- Don't do the solar PV method, it will take a life time to pay for itself. I'd go for a 'solartwin' system, its a compromise system for £2K diy install and no hot water tank changes. Plenty of info online and on YouTube etc etc.

Steve

Reply to
Mr Sandman

Have you calculated what you are spending on HW at present?

There are four adults here and daily showers, sometimes twice a day. My monthly HW cost at this season is £1.50, with cooking my summer gas bill is £2.50 > £3.00.

I want to reduce my carbon foorprint, like most sensible people do, but there is a point where common sense must cut in and prevent insanity from taking over.

Reply to
EricP

I'd be *very* surprised if that was the case over a full year unless you= have a super insulated house with heat recovery ventilation and lots of =

solar gain.

Here we use about 1cm of oil/week (about 20l) in the summer for more or =

less just hot water. In winter 6 or 7cm of oil is the norm and if it get= s cold and stormy 8 or 9cm.

The plumbing is not that special and have you looked at the cost of phot= o voltaic cells? I'd advise you to be sitting down if you want to have mor= e power than lighting a torch bulb...

Full solar hot water panel systems have payback times of the medium to long term. And they are quite effcient at capturing and storing the sola= r radiation. Going electric with large expensive batteries that need on going maintence and possibly a purpose built battery rrom and even more =

expensive ineffcient photovoltaic cells is even dafter.

Reply to
Dave Liquorice

changed much since I went the first time in 1982. They do have a super-insulated house, but not everyone can go and build one. There are plenty of sales leaflets for companies, but nothing they make at the centre. It would be far better to be able to buy a product from them that you can see demonstrated rather than have to deal with sales people at unknown companies. They didn't even sell a signle solar cell ! If that's not bad enough, my TomTom directed me to drive up a fenced off footpath which I thought was funny.

Reply to
Ian

There is no link between sensible people and carbon footprint, whatever you are defining as a carbon footprint. Most people don't have a clue what it is because the term is so misused by people who think it is fashionable. One advert on TV is stating their tyres reduce some sort of footprint. It's sales talk, so learn to see through it. Sensible people will go for insulation, more efficient products and cheaper suppliers to save money. Most will also calculate what they currently spend, then decide not to fall for a sales con to keep up with the neighbours. If you had spent thousands on a heating system that only give luke warm water, you would say it was great!

Reply to
Ian

If you already have a tank. We didn't so had to install one - but not with two heating coils.

We're extremely happy with ours, our last gas bill was £8.95 for the quarter.

Mary

Reply to
Mary Fisher

They have a strong bias against photovoltaic cells. On my first (and last ever) visit, I asked about them and was directed to their resident "expert". He told me that no photovoltaic cells had ever been made that delivered more energy during their working life than had been consumed in their manufacture. So CET didn't like them - in other words HE didn't.

When I researched photovoltaic cells, I found that his claim was not true. Taking into account the less than ideal latitude in the UK, plus allowing for them not rotating to follow the sun, and therefore losing some more efficiency, it seems that they will generate three or four times the energy it cost to make them.

So they may not be the greenest method of electricity generation, but they are nowhere near as bad as he suggested.

Reply to
Bruce

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember jives11 saying something like:

Forget solar electric, the costs are ridiculous and only feasible if you're off grid. Solar water heating is perfectly feasible if you diy - if you don't diy it makes no sense. Have a look for diy solar on google.

Reply to
Grimly Curmudgeon

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The summer quarter, though!

Reply to
Bruce

May be true if you never use the CH and walk or bike everywhere. Not many people are comfortable in a freezing house though.

At 3k its not likely to ever pay its way

wildly uneconomic. The equipment's much more expensive than solarthermal, and much less efficient.

Could, but not economically.

At the medium power levels involved you can wrap resistance wire round the tank over glass fibre tape - if the tank's a non-foamed type. Or you can simply run the cells in series and feed direct to the existing

240v heater, running it at lower voltage & power.

Why use batteries to store power when you can use the water to store the heat?

free? Google amortisation :)

true of other options too, so not an advantage

It would be a lot cheaper to install more cylinder capacity and stick to daytime heat.

Theres a reason no-one does it. Even if you cut the system to the bone with electrode heating and no heat output margin you'd still be paying a fortune for the hot water.

And dont forget those panels are made using carbon based fuels.

If you just want to play with solar HW you can make a small hosepipe heater that will deliver a sinkful of steaming hot weater every 40 minutes for a tenner. Something basic like that has way more chance of paying its way. There's so little to be saved on DHW that any system has to be very cheap to pay its way. A bigger version with drain down provision could heat a cylinder.

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Reply to
meow2222

That's about 20 hours in the shower, without the solar heating.

Reply to
dennis

Bit of a sweeping statement innit? It assumes that climate change is caused by our energy use & the jury is still out on that one AFAIK.

Tell that to the tree huggers.

Reply to
The Medway Handyman

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Well, thanks for pointing that out to me :-)

I know from experience that it varies mostly according to our use of gas fires in the coldest of weathers.

My point is that we hardly use the boiler at all.

Mary

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Reply to
Mary Fisher

Not really Dave. I think we do dump too much crap into the wild on all fronts for convenience, without much thought and it should be checked a bit, but I agree on the global warming scam. As you say the jury is still very much out on that one.

Yes, I always wanted a bobble hat and they went and spoiled it. :((

Reply to
EricP

On Sat, 30 Aug 2008 08:12:57 GMT someone who may be "The Medway Handyman" wrote this:-

Sorry to interrupt that line of thought with some reality, but the jury has not been out on that one for some time.

is a good summary, in particular the graph.

If you think you know more about the weather than the Meteorological Office then perhaps you could explain the basis for your knowing more than them.

The only huggers are those who still cling, for whatever reasons, to the idea that it is all due to nature. Take a look at the graph.

Reply to
David Hansen

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