Solar Panal info req for domestic use

[Andy Champ]

Mary,

I read that article yesterday, then thought about it.

Your system wouldn't suit me.

I can't be sure exactly how much hot water we use each day.

When I have a shower, I don't want the temperature to be down at ... what was it? 31 centigrade? when I finish. So the temp in the top of the tank needs to be 40 plus. Better 45.

Your system pulls in cold water from the bottom of the tank, warms it a bit, then dumps it back in the top. Where it will mix with the *hotter* water left over from the last boiler run. And ruin the stratification.

What *would* work would be a second cylinder to preheat the water before delivering it to the hot one, which would be gas (or something) heated. By raising the input temperature to the hot tank from... er... 8.5 degrees (I just went and measured it) to 31 I'm saving 23 degrees worth of heating. I then need to dump in another 40 degrees or so to get it to a legionella-safe 60. Lets make it easy and bring it up by only 35, which means the solar is going to save me 40% of my gas bill.

Of the part that is for hot water only.

OK, in summer it'll be more effective - but in winter it'll be doing nothing much, or freezing wouldn't be an issue.

My last summer quarter gas bill was £65 - no heating, so that tells me the hot water cost. I'll save 40% of that, by 4 quarters, about £100 per year.

Remember that installed cost is going to have to include a 2nd cylinder to even get that efficiency...

Now I can get 5% on investments with no problem. So if the installed cost is over £2000 *including* the 2nd cylinder - forget it. Better things to do with my money. Say buying a really fuel efficient car for the commute.

Andy.

[Derek Geldard]

Oh well you'll be able to describe the experiment in detail then. A mere bagattelle for such as yourself. A "Classicist" and all.

Incorrect, that's the "People's Friend" version.

I went to the same school as one of the ZETA team

The problem was that they weren't measuring what they thought they were.

They were wrong.

It wasn't happening.

This is a matter of public record.

Now tell us more about what your understanding is of these little problems of "Containing the temperature". Or did you mean "Heat"? Please expand.

BTW good day today in Leeds ( 9c) how much solar energy did your solar water heating system aquire ?

DG

[Derek Geldard]

No I'd buy a spell checker before I mouthed off at other people's typos.

DG

[Derek Geldard]

Depreciated Cash Flow.

You wouldn't inderstand it.

Since you have claimed to be both a Classicist and Nuclear Physicist I assume you're not also claiming to have accountancy qualifications as well.

DG

[Derek Geldard]

And a fool and her money is soon parted.

And if they know jack shit ?

How much solar energy did you collect today (28/01/2008) ? A very favourable day here in Leeds?

Yes, Yes, Yes, The salesman was a nice man, a very, very nice man.

Am I correct. He took your money did he?

OK. How much solar energy did you collect today (28/01/2008) ? A very favourable day here in Leeds?

Getting sued eliminates the profit on 10 - 30 sales. Go figure.

When you lose you keep quiet about it, at least in public forums ...

DG

[Derek Geldard]

Hrmmph.

"Work on the sun"?

Does the sun not heat parts of the earth on a seasonal basis and raise the external temperature ? Is summer not warmer than winter? Is not the warmth-tude not dependant on the received energy flux from the sun?

I am surprised I have to assert this, my daughter teaches this in primary school I could arrange for private coaching for you (And Mary "Classicist, and Quantum Physicist" Fisher) if it is really needed.

DG

[Peter Scott]

Apologies if this is mentioned in another message in this thread, but There are now so many I don't want to read them all. I've got a book called 'Tapping the Sun' by Chris Laughton ISBN 1-90217-529-8 website

It's a bit pricy for its size but it does have a good summary of water heating systems. Might be worth a read.

Peter Scott

[geoff]

In message , Mary Fisher writes

Buy me one, then

[David Hansen]

On Tue, 29 Jan 2008 00:30:44 +0000 someone who may be Derek Geldard wrote this:-

I have never noticed Mary making claims of any sort regarding her background, unlike some of those who disagree with her.

[David Hansen]

On Tue, 29 Jan 2008 01:03:08 +0000 someone who may be Derek Geldard wrote this:-

Correct. If you wish to assert that they work differently you might like to explain your theory.

Many words, but they add little to the discussion.

The facts are quite simple. Solar panels work by absorbing heat from sunlight. As they have a small mass they warm up more quickly than the surroundings. This heat can then be transferred elsewhere. The external temperature has nothing to do with this process, which is why they can be used in the antarctic.

A solar panel will lose heat to the surroundings. However, this is minimised by various forms of insulation.

Thus the assertion that it is too cold in winter for solar panels is incorrect.

Excellent, more personal abuse. Do keep it up.

[David Hansen]

On Mon, 28 Jan 2008 21:05:44 +0000 (UTC) someone who may be Ed Sirett wrote this:-

Yes and no. It depends on the design. In particular, as I have said before, some solar controllers will also control a boiler. They will suppress boiler output if there is solar input and storage is above a minimum temperature. Instead of controlling the boiler directly such a controller can control the heating of a hot water cylinder. Once set up such controllers can be left alone, unless the household contains a fiddler.

Of course such a system involves more work and so at the moment tends to be more a DIY option.

[David Hansen]

On Mon, 28 Jan 2008 21:41:40 +0000 someone who may be Andy Champ wrote this:-

Do you think anyone can say exactly how much hot water they will use in a day? Solar water heating works by slowly warming the water and storing enough of it to overcome variable draw offs.

"Ruin" is a rather strong term. It would be the correct term if the Solartwin system involved high flow rates, but it doesn't.

That used to be the fashion. However, as well as cost it has the disadvantage of extra heat losses, due to the extra volume of water stored at above ambient temperature). This reduces the effectiveness of the system. For a number of reasons few offer such systems these days.

Any freezing generally happens overnight, when there is no sun to warm the collector. When/if the sun rises the frozen collector is rapidly thawed out and will then start warming the water in the cylinder. On a very cloudy day the collector might stay frozen all day, which is no problem.

With a drainback system the collector will be empty overnight and thus not frozen. When/if the sun is out enough to make collecting its heat worthwhile the panel is filled up and it is then obviously not frozen.

With a non-drainback system the system either has antifreeze added or the controller uses a little heat from the store to keep the water temperature above freezing. When/if the sun comes out hot water production starts.

[The Natural Philosopher]

Completely wrong, but one expects nothing else. Google 'black body radiation' for the facts.

Correct, there is too little direct sunlight. Again an understanding of various things like the relationship between energy transfer and the perceived temperature of the source, and what cloud cover intersperse atmosphere does to it, would be somewhat better than blank erronoeus assertions.

At least its based on reason, not pseudo scientific blather.

>

[David Hansen]

On Wed, 30 Jan 2008 13:02:13 +0000 someone who may be The Natural Philosopher wrote this:-

Another assertion. Strongly expressed, but not backed up by anything convincing.

I did black body radiation a long time ago.

Yawn. Do keep it up though as it is probably revealing.

You may have the last word at the moment.

[The Natural Philosopher]

And didn't understand a word of it one assumes.