solar water heating panels

[clogs]

had a chat with a chap about the solar water heating panels.....
I have them.....and very happy with them....
but how many on the forum use them.....?
just outta interest....

 

[Spectric]

I think you get much hotter weather for more months of a year than we ever do, so should be very efficient in Greece. Only ever known one person to use them and that was some time back, hot water in summer and pre heating water to the boiler in winter.

 

[Argus]

It's all oil or LPG here....... no gas for miles and electricity is expensive.
I'm in mid Wales and I have a bank of 4 them augmenting an oil-fired heating system. They were here when I bought the place 12 years ago, installed about 30 years ago - and still going strong.

There is obviously been a deterioration in the plate's thermal pick-up efficiency over that time, but with only one moving part (the pump) it all works. Basically, the controls look for a 5 degree difference in the cylinder water input sensor and the stack temperature on the roof..... if it is then there will be an exchange of heat. Simple as that. It doesn't matter that there may be overnight frost on the car in December, if the sun's bright mid-morning, which it can be and the heat from that gives that 5 degrees split, it gains heat which it rejects to the water in the cylinder.

The whole array will will quite easily achieve a cylinder water temperature of 50 degrees even in December, if the sun is bright enough. Clearly there is a limit to the amount in the winter months but, it does exist and this will offsets the oil boiler or other form of water heat and provides a saving. Otherwise, for many months of the year it is the principal source of water-heating.

At the other extreme, in this last week's so-called heat wave, with ambient dry bulb temperatures in the upper 20's, typically 26 - 28 degrees, the top day-time temperature on the stack has been in the upper 90 degrees, then over 100 a couple of times and the cylinder water temperature is over 70 in the evening, with no use of other hot-water input. Most of the time it will easily top the 60 degrees limit that keeps the boiler off. Even a sunny day in winter this will translate to some hot water.

Sometimes the outlay of so-called 'green-initiatives' can be compared to spending a fiver to save a quid, and it's necessary to offset and amortise the installation cost against the pay-back, but I think that my stack has been a benefit to me and the previous owner who put it all in. It probably paid for itself 15 or 20 years ago.

These things can be more costly than they need to be as an installed item in the UK - we don't have the market size that other countries have, nor the expertise on the ground - but they do work and they are a long-term benefit because of the system's simplicity.

 

[clogs]

Argus,
thanks for the input.....ur system will have course paid for itself time and time again.....I'm glad ur happy with it....
As Spectric says it's our primary sourse of hot water here in Crete.....the odd time in the winter it's not quite enough so then we have to burn wood...we could burn oil (duel fuel boiler) but the Arab's don't really need my money.....
incidentaly we get good Olive hard wood for our winter fuel....works out €120 per ton cut into 30cm lengths.....about a 1.5 ton gets us thru.....

When I lived in the bush (Africa) we had to make our own solar panels.....they are quite easy and cheap to make.....depending on wether u want full water pressure or the gravity type....
so far, thanks for answering......

 

[Trainee neophyte]

I have two of the passive type - ie the water tank sits above the panel and as hot water rises (or cold water sinks, I forget which) the water heated in the panel rises and exchanges its heat with the water in the tank automatically. I have a friend with the panel on the roof and the tank in the basement - plumbed into the central heating hot water system - this needs an electric pump, thermostats, temperature sensors etc and seems to fail every three or four years. A good earner for a plumber.

My only complaint with the passive system is that the water is ludicrously, dangerously hot. You get used to superheated steam showers, but foreigners have to be warned otherwise they can do themselves some damage. It is always on my list of things to do to cover the panel with a sheet to reduce the efficiency, and maybe one day I will. The upside is 300 days a year unlimited free hot water.

 

[Just4Fun]

I have 90 evacuated tubes which I installed 16 years ago. They produce about 7 000 kilowatt hours per year, most of which I feed into the heating system. During the summer the heat is directed to our hot water system.

Peak production is in February & March, despite outside temperatures being -20C or -30C at that time. The skies are very clear then, plus a lot of light is reflected off the snow onto the tubes.

 

[D_W]

They were all the rage here about 35-40 years ago and were on roofs in a lot of places, but must not have held up well.

About a decade ago, the vacuum tube arrays started showing up, but just as fast as they came, they often had a sign on them letting passers-by know that the whole array was for sale.

 

[recipio]

I had the tubes filled with antifreeze installed a few years ago as part of a Government grant package. They work brilliantly from about March to October then its back to gas for the winter. One thing nobody told me is that they can overheat and when the tank temp hits 90 degrees C it will blow a safety valve. This happened about three years ago when a I found a geyser blowing scorching hot water in the hot press. Nothing for it but to pay for a venting system to prevent it happening again. What maddens me is that I would have paid for a safety system initially if only the plumber had told me but alas a lot of them just want to take the money and run.☹

 

[clogs]

by pass valves are standard here.....
but I guess it's almost once in a lifetime in the UK...
well before global warming.....
actaually quite a few have another tank for excess hot water......
U can almost boil water every day here......certainly after 10 am u cant touch the hot water exit pipe from the panel.....
our's is a 2 panel system (1.2m Hx 1m W) heating a 300lt tank.....

 

[Terry - Somerset]

In the UK, we don't typically have the climate to get year round heating from solar water.

But it is inexcusable that panels are not mandated for all new build when the cost of installation must be a small fraction of the cost of retrofitting. As an original fitment I suspect they are wholly justified.

The government insist (rightly IMHO) that carbon neutral is the way to go yet do very little to promote the right behaviours.

 

[mikej460]

We had a 3 panel vacuum array that worked well but it was forever boiling dry so we sold it. We had a Heatrae Sadia solar HW tank fitted in case we decide to try again.

 

[Phil Pascoe]

In the UK, we don't typically have the climate to get year round heating from solar water.

But it is inexcusable that panels are not mandated for all new build when the cost of installation must be a small fraction of the cost of retrofitting. As an original fitment I suspect they are wholly justified.

The government insist (rightly IMHO) that carbon neutral is the way to go yet do very little to promote the right behaviours.

My late friend had solar water heating panels that he installed himself in 1983 - he swore by them. We said at that time that solar panels of some description and grey water systems should be fitted by law to new builds and major rebuilds - they would now be a fraction of the cost. Nearly forty years later it hasn't happened yet. Why haven't all units on industrial estates, train and bus stations etc. have solar panels on them instead of farm land being used?

 

[Phil Pascoe]

In the UK, we don't typically have the climate to get year round heating from solar water.

Cornwall, no mains gas, multi fuel stove. My heating bill is less than £100 p. a. but my water heating bill is two thirds of the electricity consumption.

 

[ian33a]

I have photo voltaic panels to which I built and added a surplus power diverter to power the immersion heater. I don't have a stratification pump in the hot water cylinder so so cannot heat the whole tank with this system but it does save a little on the gas bill and has more than paid for the material cost.

As the FIT pays for power exported from my solar array, I get the financial benefit of the export while still getting to actually use the power as well.

 

[slavedata]

I have had a Solar Hot Water system in the UK for 8 years now. Works very well and the gas very rarely goes on in summer for water heating. You have to have a bigger "Newark" hot water tank with an extra heat exchanger. The solar system is sealed and pressurised The actual unit on the roof is very clever. 30 Heat exchange tubes sealed and half wavelenght coated. Inside the tubes are copper rods with fins attached. In the centre of the rod is a liquid that conducts the heat up to the heat exchanger at the top of the unit. This means the circulating liquid that exchanges at the tank only passes through the top of panel heat exchanger which is super heated to make the exchange process more efficient.

The system isn't very expensive and pays for itself in a few years. It's sourced from here.
Complete Solar Thermal Kits | Stoves And Solar

 

[Just4Fun]

In the UK, we don't typically have the climate to get year round heating from solar water.

I have 2 quibbles with that:

• The climate is not really what matters, it is how clear the skies are. Cloudy or hazy skies really cut down the output from the panels, but nothing else matters very much. My solar heating has more than paid for itself even in our climate.
  
  
• Year-round heating is not realistic in most places, but solar can still make a significant contribution. You just have to look at it as a supplement rather than a main heating system. My system is virtually useless from late October to mid January, but over the whole year it saves a lot of money.

We had a 3 panel vacuum array that worked well but it was forever boiling dry so we sold it.

Was it professionally installed? If so, they should have been able to prevent that problem. More an installer problem than a fundamental problem with the technology I would have thought.

I can divert the hot water from my panels to any/all of 3 destinations:

• A heat exchanger plumbed into the radiator circuit. This is the biggest user of the heat. It significantly reduces our heating costs. A real asset.
  
  
• A heat exchanger in the hot water circulation loop. This is the default use in summer but I designed this part of the syste poorly and it is not as useful as it should be. I would do it differently if I were to tackle it again.
  
  
• A loop of pipe under our front steps, to melt the snow off them. My thinking was that when the solar heating system was producing warm water not hot enough for heating or hot water I could still get some use out of it. It sort of works but is not really very good. It will keep the steps clear if there is no snow build-up, but if snow has already settled on the steps it will not easily clear them. I would not bother doing this again.

 

[John Brown]

We moved into this house 2 years ago. It has PV and water heating panels. I love the PV, but the water, not so much. It means we're stuck with a hot water tank, and I'd prefer a combi/on demand system. Apparently it's a bit of a minefield trying to use solar with a combi boiler, or so we've been told. So we end up with plenty of hot water in the middle of the day in summertime, and none on cold winter mornings. Unless we keep the boiler on, of course.
This boiler is on it's last legs, and I am uncertain about which way to jump when it needs replacing. I can't see air source being an option, what with my American family thinking anything less than 23C is freezing,
Maybe I should replace with a combi before the deadline. I'm all in favour of green stuff, but it's a lot easier at the design and build stage. Trying to retrofit a 400 year old barn is a bit harder.

 

[Stuart Moffat]

We moved here (between Bedford and
Cambridge) about fifteen years ago , 2 years in we had the crappy asbestos cement slates removed and I was also replumbing heating. Professional quotes for solar panels were very expensive then, and they all wanted to put them on a west facing roof. Easiest place to instal and very visible on the street.
I bought all the stuff to put up two panels for £1,500 all in, including a new tank. I did the plumbing, and the roofers were happy enough to do their bit of when installing the new slates. It really did pay for itself within 12 months and has required zero maintenance ever since . The first year we were here we filled the oil tank 3 times. It’s once a year now.