Solar electrical water heating

[EricP]

And many thanks for taking the trouble to write a very good piece. :))

[EricP]

Usual sweeping ecobollox statement. Thankfully total rubbish as usual.

[PCPaul]

Whoops. My mistake. I've got a combi and a stupidly designed evacuated tube system (done by the previous owners). You're right, feeding the cold inlet to a cylinder should work fine. Presumably having the smallest single coil cylinder to be preheated by solar would work best in that case?

Dual coil cylinders are made from unobtainium and welded with rocking horse farts, judging by the price.

[dennis]

The Met office have enough trouble getting a three day forecast right, what makes you think the climate models are any better than whole atmosphere models used for weather forecasting?

I will give you a clue.. they aren't, however you will have forgotten how bad they were in twenty years time unlike yesterdays weather forecast.

[dennis]

It sure as hell wasn't unanimous.

I am a physicist too and I don't see any real evidence to backup CO2 as causing global warming. I have seen some evidence that global warming increases CO2. However the CO2 is in the wrong place to make much difference to the greenhouse effect.

[dennis]

So you don't know how to do it. It doesn't mean it can't be done using a preheated tank.

If your boiler can't take hot water input then fit a thermostatic mixing valve on the output, one side connected to the boiler and the other to the preheat tank. Set the temp to about 20C below the boiler and it will take as much preheated water as it can and mix it with the minimum of hot to get the temp selected. All these "problems" go away if you think for a few seconds.

[PCPaul]

No. No they don't.

Combi boilers, even ones that can modulate the heat well, are rarely able to give a 'minimum of hot' - mine for instance can only modulate down to

8.5kW output (from 25kW). If the scheme you suggest above is used, then on a hot day the solar water is likely to be >40C and the amount of water needed to top that up will either not be enough to trigger the boiler or it will rapidly overheat and short-cycle. Either way I don't get a nice stable hot supply out.

It's a nice idea, but in practice I think there are issues with it. If you can prove me wrong I'd be happy to try it.

[Grimly Curmudgeon]

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

I feel sorry for the furriners, but the web-footers can take their chances.

[Grimly Curmudgeon]

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

LOL! Priceless. Perhaps not using the boiler as much will buy some green conscience enough to compensate for melting an iceberg.

[David Hansen]

On 31 Aug 2008 10:36:48 GMT someone who may be [e-mail] (Andrew Gabriel) wrote this:-

I take it that you have complained about this "misrepresentation" which is being made using taxpayer's money to your MP. Or perhaps you don't do so as your MP is part of the grand "conspiracy", which tends to get ever larger with every telling.

You repeat many claims which have been debunked. I'm not going to waste my time debunking them again. Real climate is good place to start . For those who want to study the science is the place to start, in particular the "Summary for Policymakers".

You say you are, "a qualified physicist", yet don't mention which of the many highly specialised bits of physics you are "qualified" in.

Mr Lawson has spoken and written often on climate change in recent years. None of it was convincing. His work has been debunked too.

[David Hansen]

On Sun, 31 Aug 2008 09:54:42 GMT someone who may be "The Medway Handyman" wrote this:-

International action was taken on that. As a result the problem has been reduced. A good result in my view.

You ask a question. Then you claim to answer it.

Don't give up the day job and take up mind reading. You are not any good at it. You have no idea what articles I have read or not read.

[David Hansen]

On Sun, 31 Aug 2008 14:27:24 GMT someone who may be EricP wrote this:-

I wouldn't use the word unanimous myself. However, I would say that the scientists have reached as strong a consensus as they ever do.

What the antis tend to do is focus on disagreements about details and then claim that this proves the whole thing is untrue. This sort of distortion shows how desperate they are.

The "conspiracy" theory is rebutted at

which is worth repeating:

"Climate myths: It's all a conspiracy

" * 17:00 16 May 2007 " * NewScientist.com news service " * Michael Le Page

"Conspiracy (noun): a secret plan by a group to do something unlawful or harmful.

"If you believe that tens of thousands of scientists are colluding in a massive conspiracy, nothing anyone can say is likely to dissuade you. But there are less extreme versions of this argument.

"One is that climate scientists foster alarmism about global warming to boost their funding. Another is that climate scientists' dependence on government funding ensures they toe the official line (pdf).

"It has taken more than a century to reach the current scientific consensus on climate change (see Many leading scientists question the idea of human-induced climate change). It has come about through a steadily growing body of evidence from many different sources, and the process has hardly been secret.

"Now that there is a consensus, those whose findings challenge the orthodoxy are always going have a tougher time convincing their peers, as in any field of science. For this reason, there will inevitably be pressure on scientists who challenge the consensus. But findings or ideas that clash with the idea of human-induced global warming have not been suppressed or ignored ? far from it.

"Cosmic rays

"In fact, many of the better arguments seized upon by sceptics have been based on contradictory findings published in prominent journals, from the apparent cooling of the lower atmosphere (see The lower atmosphere is cooling, not warming) to the apparent cooling of the oceans (see The oceans are cooling).

"Millions will be spent testing whether cosmic rays can form cloud condensation nuclei, even though some regard this as a waste of money (see Cosmic rays are causing climate change).

"As for funding, the US spends billions of dollars on climate science and this increased by 55% from 1994 to 2004. However, an increasing portion of this is spent on mitigation technology rather than pure research. Climate scientists point out that if they were after a bigger chunk of that money, their best bet would be to stress the uncertainties of climate change and call for more research, rather than call for action.

"Under pressure

"As for the idea that scientists change their tune to keep their paymasters happy, under the current US administration many scientists claim they have been pressurised to tone down findings relating to climate change (see US fudging of climate science details revealed).

"Indeed, those campaigning for action to prevent further warming have had to battle against huge vested interests, including the fossil-fuel industry and its many political allies. Many of the individuals and organisations challenging the idea of global warming have received funding from companies such as ExxonMobil.

"That in itself does not necessarily mean that the sceptics are wrong, of course. Nor does the fact that most scientists believe in climate change necessarily make it true. What counts is the evidence. And the evidence ? that the world is getting warmer, that the warming is largely due to human emissions, and that the downsides of further warming will outweigh the positive effects ? is very strong and getting stronger.

"Finally, perhaps the most bizarre conspiracy-related claim is that the journalists covering science have an interest in promoting global warming.

"Journalists do have an interest in promoting themselves (and their books), while their employers want to boost their audience and sell advertising. Publicity helps with all these aims, but you get far more publicity by challenging the mainstream view than by promoting it. Which helps explain why so many sections of the media continue to publish or broadcast the claims of deniers, regardless of their merit."

[Steve Firth]

Short answer, no.

You would need about 3KW of photovoltaic panels to make a signifcant dent in your hot water bill, and around 15-30KW to make a contribution to central heating. At present prices an 80W PV panel will cost you £250. So that's 38 panels needed to generate 3KW, £9.500.

For the same amount of hot water from solar thermal you would need at most 2x20tube solar collectors, an entire installation kit including 2x

20 tube collectors, a thermal store, pumps, vlaves and controller can be obtained for £1700. It would cost about £1300 to install the kit (inc. VAT) bringing the installed price up to the £3000 or so that you quoted earlier. DIY installations save "quite a bit".

[Steve Firth]

Based on previous discussions here, I made my first solar panel from a single panel central heating radiator. I removed the fins from the back, painted the front face matt black using a high-temperature paint, enclosed the entire panel in a rivetted aluminium enclosure and glazed the front face. This has been in use for several years as a test rig with water circulated using a 12V pump and a 30W PC panel to provide the electricity. It works well since the pump speed is modulated according to the available light which tends to keep the output water temperature constant.

I'm using a very cheap and nasty pump intended to circulate hot water on boats but will, at some point, change the pump for a better quality bronze unit designed for continuous operation.

Total cost of the project was £50.

[Steve Firth]

Excellent, argument without either authority or reference. That's as useful and as relevant as a canvas fireguard.

[David Hansen]

On Sun, 31 Aug 2008 13:00:13 +0100 someone who may be Bruce wrote this:-

To be fair some parts of the US military-industrial complex are realising the implications, as are some oil companies (they are not all Exxon). They still have a long way togo though and their past efforts have put humans back by at least a decade in dealing with this problem.

There is a good summary of the stages of denial at .

[Steve Firth]

Ah, excellent. I love it when the melons stand up and reveal their real agenda.

Will you be adding a few "smash the capitalist state" comments to further devalue your "contribution"?

[A.Clews]

Thus spake Andy Champ ( [e-mail]) unto the assembled multitudes:

Well, he had the panels installed after his old boiler broke down terminally, so the total cost he mentioned (some 8000 quid) was for a new boiler plus the two panels and associated equipment and plumbing.

He hasn't mentioned what the decrease in his bill is (because I haven't asked him) but I would imagine his original bills would have been higher than mine, which hover around 140 quid per quarter.

[AJH]

I'm glad you posted that, too much power being a problem wouldn't have occurred to me.

So I take it you have a evacuated tube panel warming a hot water tank that then feeds a combi. If the water is cold there's no problem, the combi does the work, if its warm the combi still does the work and modulates down to 8kW(t). The problem arises when the water is too warm to absorb 8kW and causes the combi to short cycle.

At what temperature does this happen? For example knowing the hot water tank is at 40C I can predict short cycling will happen, but I'm happy to shower at 40C, so a thermostatic bypass on the feed to the combi set at 40C would sort that problem.

At 10 litre/minute a rise of 11.5C consumes 8kW if my calculations are at all right. In fact just checking my cold tap I only get about 4 litres/minute but it is an old galvanised pipe.

AJH

[The Medway Handyman]

FFS how sad is that. Tree huggers have websites to teach them how to argue their point. The gospel according to Saint Ecobollox. The path to green righteousness.

Learn to think for yourself.