You say that of one of the most logical people on here? Figures. You only understand adverts, not the real world.
Like I said, get your nurse to change your monitor to a lower resolution setting. It will make the print much bigger for your failing eyesight. Won't help your failing brain, though.
OK so is that an _average_ of £18/yr or £18 _each_ year? Were you able to work out the number of kWh of heating saved each year?
Was there any noticeable drop in the output of your parent's system over 10 years?
The vacuum tubes should to last for 25-30 years at least, so after a comparison over 10 years the system still has another 15-20 years life in it. Even so, the tubes can be replaced quite easily if need be.
cheers, Pete.
** sip confused senile ramblings **
You're effectively asking me what are the deficiencies of the system you measured, when I havent seen it, have no figures etc. So its very difficult to say where your particular system would be deficient.
All I can do with so little info is say a few rather general points, without really knowing the details of your system.
Firstly, the question of whats there. NREL insolation figures answer the question how much. There is also the question of direct vs diffuse. We get infra red from above every day, some days direct from the sun, some days diffuse. Vacuum tube collectors may have reflectors behind the tubes to concentrate direct IR only, and the system design may well rely on this concentration. In such cases, overcast days will not produce the goods. Flat panels will perform better on such days. Bear in mind that evacuated tubes only collect over a minority of the total area they cover, whreas flat plates collect over nearly 100%.
Tubes are more energy efficient than flat plates in direct sun, but when overcast their output falls heavily, whereas plate collectors dont suffer from as much output reduction.
Plate collectors are a better choice for low temperature water, since efficiency stays fairly high, cost per area is much lower, and performance on overcast days stays fairly good. But of course what we want is hot water, not warm to hot. A combination of the 2 collector types can give some advantages over either type alone, with water flowing through the plates first, then the vacuum tubes.
Then as you pointed out there is the question of storage. Storage volume, temperature and insulation all effect cloudy day behaviour, as well as collector type and design. There is also the question of how the storage is set up to work with the panels. I cant be anything more than vague on this, as I know almost nothing about your setup.
The big problem with solar energy generally is that although it is possible to make systems that pay, 99% of them don't. The level of design skill around doesnt seem to match the task at hand. This is to be expected, since solar is still a fringe alternative field. Those that do have the skills are thus far more likely to be employed in a mainstream field.
With NREL insolation figures and sufficient skill, one can design systems that will work, or design ones that sometimes do, or ones that are not much use. There is nothing in principle that stops solar heating working, it is all a question of getting payback good enough to make it worthwhile. Few systems achieve that.
NT
You made the statement that it was inadequately for the job. Whilst it was being monitored it achieved results which were broadly similar to those achieved from the 7 commercial systems tested by the DTI in their report DTI/Pub URN 01/1202 (available at
From the fact that the results I measured on my system and those obtained by the DTI in their tests of commercial systems were similar I conclude that my installation and design was quite adequate. I was puzzled as to why you considered it to be inadequate - if it was then it makes all the commercial systems tested by the DTI also inadequate.
Thank you for your other comments, most useful.
It was an average of GBP18 per year. In a ten year period the total saving was a shade over GBP180.
I was able to measure the contribution from the solar panels and calculated the cost of achieving the same contribution from the gas boiler (taking into account boiler and transfer losses).
There was no subjectively noticeable drop in nearly 20 years (it was only monitored for about 10).
Indeed, but the system do suffer from failures. Mine had a seal fail on a collector tube and whilst a single collector tube is relatively cheap and easy to DIY having one replaced commercially usually costs GBP100-300. The neighbours had a leak in one of their commercially installed panels after about 5 years as I recall which cost them over GBP500 to have repaired. They removed the system just prior to selling their house although I have no idea why they did so.
That may be true from the amount a daylight that we have here in Scotland in the summer but the heat collector does not track the sun so the collection must only be effective during the major part of the day which will be same for most of the UK.
Rob
I see, what was the contribution from the solar panels in kWh over a year?
At least with evacuated tube collectors there is some built in redundancy. If a single tube failed I'd tend to leave it until the roof needed other work, and get it replaced then.
Sounds like an expensive system, as a whole 20 tube collector can be had for £400 these days.
To put it on their new property I guess ;)
cheers, Pete.
But it gains heat when you would be purchasing that heat. In the US many experimenters have used devices to track the sun and gained brilliant results. In more dim UK this must make a hell of a difference.
It was just over 1000kWh per year over the period measured.
As I had several spares it was easy enough to replace. However the cost of a DIY repair with available spares is not really applicable to most people and the commercial cost is more appropriate.
It can't be replaced for GBP400 though.
In any case it was a flat panel collector so replacing the whole panel was the only option available.
I was quite surprised to read in the DTI report of the number of faults they had upon delivery of new units.
As I purloined some bits of it from their skip I somehow doubt that was the case :-).
Using a simple formula of:
Money_This_Year =3D (Money_Last_Year * Interest_Rate) - Money_Taken_Out
And assuming that the amount that would have been saved by the heating system were to be taken out each year immediately after the year's interest was paid gives the following results:
With an interest rate of 3% and taking out =A318 per year, after 20 years =A3425 remains in the bank.
If it were possible to get 3.6% interest the whole =A3500 would be left in the bank after taking out =A318 per year.
Today it is easy to get 4.5% or over, and over the last 20 years that should not have been difficult to find most of the time, which would have given =A3630 in the bank today - =A3130 profit on top of the =A318 per year that the system saved in heating costs!
Using a simple formula of:
Money_This_Year =3D (Money_Last_Year * Interest_Rate) - Money_Taken_Out
And assuming that the amount that would have been saved by the heating system were to be taken out each year immediately after the year's interest was paid gives the following results:
With an interest rate of 3% and taking out =A318 per year, after 20 years =A3425 remains in the bank.
If it were possible to get 3.6% interest the whole =A3500 would be left in the bank after taking out =A318 per year.
Today it is easy to get 4.5% or over, and over the last 20 years that should not have been difficult to find most of the time, which would have given =A3630 in the bank today - =A3130 profit on top of the =A318 per year that the system saved in heating costs!
Using a simple formula of:
Money_This_Year = (Money_Last_Year * Interest_Rate) - Money_Taken_Out
And assuming that the amount that would have been saved by the heating system were to be taken out each year immediately after the year's interest was paid gives the following results:
With an interest rate of 3% and taking out £18 per year, after 20 years £425 remains in the bank.
If it were possible to get 3.6% interest the whole £500 would be left in the bank after taking out £18 per year.
Today it is easy to get 4.5% or over, and over the last 20 years that should not have been difficult to find most of the time, which would have given £630 in the bank today - £130 profit on top of the £18 per year that the system saved in heating costs!
Hi,
Sounds good. (Though it assumes flat energy prices and zero inflation!)
cheers, Pete.
You - the biggest liar on newsgroups - 'don't believe'?
** snip senile drivel and babble **
Ignore this copy - Google Groups had a bit of a fit yesterday!
If it is easy to retrofit as you keep claiming, what is stopping you?
I can do the upstairs and feed all, inc hall, from the loft. Nice fresh air coming in and in summer keep it nice and cool. I may install a air hander up there and heat this from the boiler via copper coil battery. I can actually make my own air handler using marine ply varnished.
I know what you claim to be able to do - however it hasn't happened has it? You claim hot air is good - but don't use it; you claim enormous savings for solar hot water yet can't do simple maths and have never designed, built or used one. You claim to know better than my decade of measurements when you have no experience whatsoever. Your competence goes as far as "trust me- I'm a plumber" and no further. It's all hot air and no action isn't it?
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