The Great 'Get Paid To Generate Energy' Hunt

green_as_grass

Cardew

Sorry for the delay in my reply.

I didn't dismiss the Cranfield report because of procedural problems but because of advances in the relevant technology since the report was completed. My point about the faults in the systems that arose during the study was that installers could not manage to do the job properly even when they knew their systems were under test! This is indicative of the poor standards the solar thermal industry has in both design and installation of systems in this country. They are often like the double-glazing firms of yesteryear, who prey on gullible people to make a fast buck, charge an exorbitant price, do a shoddy job, then go bust. This is why many people (like albyota above) end up dissatisfied and why expectations of poor performance (and actual poor performance) abound.

But not all systems and not all installers are like this. This is why I advise that people do their own research first, so they can sort out the bona fide from the cowboys.

You ask, 'How has technology developed...?' There are many others better qualified to answer this in more detail than me - trawl the Navitron Forums if you want to know more, one of the Navitron founders has been using his own roof as a research and development site for many years, I wish he was replying to your question - but I'll list some of the changes that I'm aware of off the top of my head.

Let me note that I'm using the word 'technology' in its original dictionary definition sense, ie. 'the application of scientific knowledge for practical purposes'. Your comment 'Sun heats water flowing through panels' made me wonder if this was clear to you. I know many people immediately think of electronic gadgets when the hear the word technology.

Also, be aware that although the knowledge is 'out there' it is not widely understood or applied in the UK.

Advances:

1. Standard packages don't do the job. An individual assessment for each location is crucial so that a system can be designed efficiently (including measurement of hot water consumption, and patterns of use, angle & orientation of roof, positioning of panels to avoid shadowing, assessment of pipe runs so that optimum bore of pipe can be used, and so pumps are not over-powered, etc. etc.). Also, whether customer wants the system designed for rapid payback or long-term benefits in efficiency.

2. Improved 'selective' coatings on flat-plate panels to increase absorption.

3. Use of 'heat pipes' in evacuated tubes rather than circulating water through the tubes, meaning less fluid needs to be heated, so less loss of heat and better ability to cope with stagnation (over-heating).

4. Advances in the 'refrigerant-type fluid' used in heat pipes to avoid degradation over time and at extremes of temperature.

5. Use of thermal stores/accumulators rather than standard hot water tanks, which allow 'stratification' of heat layers, giving quickly-available heat without heating the whole tank.

6. Use of pressurised systems so that higher temperatures can be achieved without boiling the circulation fluid.

7. Layout of the solar circuit and order of components to minimise wear and tear on components, maintain efficiency and avoid thermosiphoning/loss of heat during cool periods (ie. night).

8. Development and availability of high-temperature and high performance pipe lagging (normal pipe lagging melts) to minimise heat losses at temperature in excess of 100 Celsius.

9. Use of expansion vessels, which allow automatic recovery after stagnation without user intervention so less down time.

10. Simple and effective methods to dump heat when tank exceeds its operating temperature (eg. using existing central heating circuit).

11. Development of sophisticated electronic controllers which minimise pumping times to when it is most beneficial, and some which allow efficient use of East-West panels for people who don't have south-facing roofs. Also facilities to continuously monitor performance of the system so that faults can be quickly identified and system efficiency maintained.

To be honest I can't be certain that all the developments in this list were discovered in the last 9 years. However I would bet a pound to a penny that very few were actually implemented in the systems examined in the Cranfield study.

You ask my view about the WHICH? conclusions.
You use the Which figures to conclude that 'solar thermal in money-saving terms is a joke'.
If I can copy some of the conclusions from the WHICH? web site here, which show that they do not agree with your judgement:

This is advice to one customer:
‘Solar water heating could easily provide 50% of their hot water all year round. They’d need to keep their boiler for central heating and to provide the rest of the hot water.’
The downside? Installing solar panels on the roof and adapting the existing plumbing (including a new hot water cylinder) would cost between £3,000 and £5,000. With savings estimated at about £90 a year, compared with the current price of gas, it could take many years for this to pay for itself.
However, the government Low Carbon Buildings Programme (see ‘Grants and offers’) provides grants of up to £400, which would reduce the cost of solar water heating substantially. If you use a more expensive fuel than gas for hot water, it’ll take less time to recover the cost of installation – electricity users will save around £280 a year, liquid petroleum gas (LPG) users £250, and oil users £330, based on current prices."

Yes, the payback figures they give for installation together with gas CH are low (£90 a year) and payback time of 'many years' is long. However this is very different to your comment regarding 'panels on your roof that are costing you money'. Note, their wording '50% of hot water all year round' is misleading. What they really mean is around 100% during summer, around nil during winter, but overall 50%.

"Solar water heating companies
While two companies gave the most cause for concern, Which? received poor service and exaggerated claims of performance from nearly all 14 firms. One suggested we’d make our money back in ‘six to eight years’ on a system costing £5,200. Even with income from the proposed Renewable Heat Incentive (RHI), pay-back times are likely to be double this."

So Which? implies here that payback time could be twelve to sixteen years with RHI. They don't imply that it is a joke in terms of saving money.

"Cowboy solar sellers
Which? chief executive, Peter Vicary-Smith, said: 'Most of the firms in our investigation behaved like true cowboys - they promised huge savings that bore no relation to reality, and some really piled pressure on the homeowner to sign up immediately or risk losing a one off "special offer".
'The solar industry is too important to our long-term energy needs for things to drag on like this. It needs to clean up its act, and if it won’t, the OFT and the government will have to step in.' "

Although the WHICH? CEO says that most solar thermal firms are cowboys they do not conclude that Solar Water Heating technology per se is useless. Quite the opposite; it is 'too important for our long-term energy needs' to let the cowboys carry on.

In the absence of any regulations regarding design and installation of solar thermal systems, sadly, it is up to the consumer to be well informed if they want to avoid the cowboys.

My conclusion is that a well designed and installed system, utilising the best technology (technical know-how) currently available, will perform far better than the current average figures they quote. So payback times of 10 years are not as far-fetched as you would claim, Cardew, even at current energy prices.

Most people acknowledge that energy prices are set to escalate as supplies dwindle, even if they aren't fully aware of 'peak oil' issues. You, on the other hand, seem confident that inflation will remain stable (or go down) in the short term and don't wish to take the long term view into account.

You dismiss claims from actual users of solar thermal panels to be 'justifying their purchase' and 'saving face'. I think these are the people best-placed to inform us of the potential of solar thermal. These are the people who have the irrefutable evidence on their monthly bills of what a well designed and installed system at comparatively moderate cost can achieve. There is a small army of people on the Navitron forums who dedicate much of their spare time helping other people get their installations right. These are not the actions of people who know they have wasted their money but don't want to admit it. Rather, they are enthusiastic about this technology because they know it works, and they want to help other people avoid the cowboys. And, like the BMW and 50" TV owners, they get use from it, pride and pleasure in their ownership.

I'd be very surprised to hear someone expressing the same level of enthusiasm about their new gas boiler, however efficient!

And you mention repairs. Yes, pumps and electronics do go wrong, but can be replaced relatively cheaply. Most components in a solar water heating system will last many years without maintenance. Compare that to a brand new condensing combi boiler.

You ask about justifying the cost of bigger systems. If you're talking about payback then the smaller systems will be quicker, particularly those that utilise an existing tank and have no need for a heat dump facility. That's not the way I have chosen to go, because once payback is achieved you then have a system which gives limited benefits thereafter. I would rather have a larger system that gives benefits that continue through some of the autumn and spring seasons; benefits that will then carry on long after payback has been achieved.

Since my own system is not up and running yet I can't give you figures to quantify the benefits. Why not start a thread on Navitron asking users to give you their real life figures? Or would you just refuse to believe them?

Cardew

green_as_grass wrote: »

You dismiss claims from actual users of solar thermal panels to be 'justifying their purchase' and 'saving face'. I think these are the people best-placed to inform us of the potential of solar thermal. These are the people who have the irrefutable evidence on their monthly bills of what a well designed and installed system at comparatively moderate cost can achieve. ?

Green as Grass,

Just a couple of points.

I have read the Navitron forums and as you say there are enthusiasts - some might say there are zealots as well.

I don't know what your definition of 'irrefutable evidence' might be, but the quote you included as an example of 'actual savings' in an earlier post is quite typical.

Somebody compared their gas bill from Sep to Dec 2005 without solar with their Sep to Dec 2006 gas bill and concluded that their new solar system had saved them 1,824kWh - in a Sep to Dec quarter - utterly stupid - but irrefutable proof????

I recently spoke to the technical manager of a solar installation firm(very much not cowboys) and for a system costing in the region of £4,000 he stated the annual output would range from approx 800kWh pa in North Scotland to 1,200kWh in SW England.

Surely you can get massive arrays(if your roof is big enough) that will produce 2,000kWh pa or more and cost a lot more. However even 2000kWh is approx £60 -£80 savings if you have gas.

I would add that with a hot water tank there are heat losses of between 2kWh and 3kWh a day(water at 65C) - something that a combi boiler does not have.

These are the important WHICH quotes from their 25 April 2010 report

These claims are wildly optimistic. A highly experienced solar water heating expert calculated that the reduction on the overall gas bill would be closer to 10% - a saving of about £55 a year at current gas prices.

Solar water heating panels typically cost between £3,000 and £5,000, and will save you between £50 and £85 a year on water heating costs, with the biggest savings to be reaped if you have an electric heating system.

My note: for all fuels

A typical system is able to provide you with around a third of your hot water needs - a saving of £50-80 on your water heating bills a year, based on a three-bedroom semi-detached house.

Some panels require regular checks of the unit and connections, or a wipe of the panel glass with mild detergent. Bear in mind how difficult this will be when panels are up on your roof.

You can add solar water heating panels to most existing hot water systems, though you’ll usually need to add an additional cylinder for pre-heated water, or change your existing cylinder for one with a twin coil.
It’s difficult to use a solar water heating system with a combi boiler because these are designed to take cold mains pressure water and solar water heating systems supply low pressure warm water.

The bottom line is that the only figure that counts is the annual output in kWh of hot water you can use.

Now I ask again, you invest £4,000 on solar you lose around £150 a year in interest, compounded.

WHICH calculates £55 annual savings with gas(£80 with electricity) so how is that not a joke in money saving terms?

yakky58

Thought I show the PV figures for 2009-2010 I submitted to Ofgem

Month Export Generate Used in kwH
April 2009 138 252 114
May 2009 135 267 132
June 2009 146 290 144
July 2009 154 262 108
August 2009 119 236 117
Sept 2009 114 215 101
October 2009 58 117 59
November 2009 29 64 35
December 2009 16 45 29
January 2010 23 53 30
February 2010 36 47 111
March 2010 111 211 100 Total 2059 kwh 09-10

Array is 2kwH
Cost £8,500

Average use of elect is 4,200 kwH per annum so I generate around 47%.

No defects in 4 years, peak generation was 2078 watts

Panels show no drop in production over four years.

Cleaned twice a years with a hose (Mar-Sept)takes about 30 mins.

Cardew

yakky58 wrote: »

Total 2059 kwh

Array is 2kwH
Cost £8,500

Those who haven't followed Yakky's interesting and pragmatic posts in this forum should appreciate that the reason his array is so cheap is that he did some considerable DIY work on the installation.

What is interesting is just how little power was generated in the 4 winter months(Nov - Feb) - just 10% of the annual total.

John_Pierpoint

Unfortunately with government created inflation in RPI terms running at 5 - 6%; so we are all losing money by keeping it in savings accounts.
Who knows what the best alternative investments are but the gold and silver bugs might like to add FiT to their portfolio.

green_as_grass

Cardew

The example I gave did indeed show large savings. I imagine he must have a large array, possibly for heating a swimming pool, possibly not in the UK (some posters are from further afield). He did not include details of his system, I'm afraid. It was just the first example I came across. It does not mean that his figures were exaggerated. You seem to resort to criticising the character of people giving these examples of savings ('zealots') rather than taking the information on board. I don't find this a convincing form of argument.

Yes, you do keep asking the same question again and again don't you! Yet you seem to be missing the point that I keep making.

I maintain that real-life examples of savings are the best evidence that solar panels do work well when designed and installed based on current advances in technology. The problem is that many installers (even the ones who are not con-merchants) and many so-called experts are not aware of these advances, or base their predictions on the 'average' designs/installations rather than the best. How confident are you that the 'technical manager' you spoke to is aware of the recent technological advances?

Again, you use the WHICH? figures to make your point, but have not answered my point that WHICH? still endorses solar water heating. I wonder if, in their figure for 'savings' they are taking account of loss of interest / payment of loans. Any calculation regarding payback / savings must surely do this if it is to be meaningful. Or perhaps they are taking the long term view of escalating costs of fossil fuels. How do you explain their positive attitude towards solar thermal?

You say that "It’s difficult to use a solar water heating system with a combi boiler because these are designed to take cold mains pressure water and solar water heating systems supply low pressure warm water."
Actually an up-to-date design would probably utilise a thermal store rather than a standard hot water tank. These supply hot water at mains pressure (heated by a massive coil within the store) and so it is possible to use this type of system with a combi boiler.

I'd really appreciate it if you would address, or even just acknowledge, the points I'm making.

albyota

I purchased and fitted my own solar thermal panels for approximately £2,500, and believe I am qualified to discuss with confidence as to how it works....fitted over 2 years ago, the 4 square metres of genersys flat plate panels on the 45 degrees pitch south facing roof, has a thermistor in the panel and a thermistor in the twin coil cylinder, if the temperature in the panel is greater than the water temperature in the cylinder, then the controller switches the circulating pump on and can modulate from 0 to 100%. there has to be roughly a 15 to 20 degree difference for this to happen, on a day like today part sun this morning, cloudy in the afternoon, the 210 litre 'OSO' cylinder temperature rose from 28 degrees to 51 degrees. On warmer, clearer skies mainly between say 10am to 4pm this time of year the yield would be nearer to 70 degrees in half the time, however you cannot use all this very hot water in a day. we all have showers and if it is a very warm day, the cooler the shower, you couldn't use it for heating without a large thermal store and you wouldn't need heating if its warm.
one thing to remember, either extra controls are required to hold off the heating system to be able to benefit from solar, or set the boiler programmer to only switch on after the sun has gone i.e. 6pm and only heat the top section of the cylinder only with the amount of water you are likely to use that day then let the cylinder remain cool for the following days yield, hot water will not heat hot water, 2nd law of thermodynamics.

so....today my 38 watt grundfoss circulating pump ran for about 6 hours and yielded what 30 -40 pence worth of hot water.

to replace the pump would cost £80
to replace the controller would cost £110
everything else is maintenance free
Panels are just coils of 15mm copper pipe in a sealed insulated aluminium box with dark glass.

nothing technical about it, and what technological advances could there be, a way of keeping the sun in front of the clouds??? even with evacuated tubes at a lot more money.... if its cloudy.....you get nothing.

Cardew

green_as_grass wrote: »

Cardew

The example I gave did indeed show large savings. I imagine he must have a large array, possibly for heating a swimming pool, possibly not in the UK (some posters are from further afield). He did not include details of his system, I'm afraid. It was just the first example I came across. It does not mean that his figures were exaggerated. You seem to resort to criticising the character of people giving these examples of savings ('zealots') rather than taking the information on board. I don't find this a convincing form of argument.

Yes, you do keep asking the same question again and again don't you! Yet you seem to be missing the point that I keep making.

I maintain that real-life examples of savings are the best evidence that solar panels do work well when designed and installed based on current advances in technology. The problem is that many installers (even the ones who are not con-merchants) and many so-called experts are not aware of these advances, or base their predictions on the 'average' designs/installations rather than the best. How confident are you that the 'technical manager' you spoke to is aware of the recent technological advances?

Again, you use the WHICH? figures to make your point, but have not answered my point that WHICH? still endorses solar water heating. I wonder if, in their figure for 'savings' they are taking account of loss of interest / payment of loans. Any calculation regarding payback / savings must surely do this if it is to be meaningful. Or perhaps they are taking the long term view of escalating costs of fossil fuels. How do you explain their positive attitude towards solar thermal?

You say that "It’s difficult to use a solar water heating system with a combi boiler because these are designed to take cold mains pressure water and solar water heating systems supply low pressure warm water."
Actually an up-to-date design would probably utilise a thermal store rather than a standard hot water tank. These supply hot water at mains pressure (heated by a massive coil within the store) and so it is possible to use this type of system with a combi boiler.

I'd really appreciate it if you would address, or even just acknowledge, the points I'm making.

Green as Grass,

I am happy to acknowledge your points but I simply don't agree with them. I am sorry to be blunt but your posts are full of obfuscation and illustrate the point I was making about people justifying a decision they have made.

You quoted a completely nonsensical 'actual' saving of somebody who concluded that he had saved 1,824kWh in a Sep to Dec quarter(December mind you!) He concluded this by the highly scientific method of comparing gas bills.

You now surmise that this might have been for a swimming pool or he lived abroad - despite using the 1824kWh @ 3p+/kWh to calculate savings.

Why should we take such nonsensical statements 'on board' when they are clearly flawed. If you read some posts on MSE they give 'actual real life examples with statistics' of people who have achieved fuel consumption reductions on their cars and oil CH over over 30% by the simple expedient of strapping a magnet on their fuel lines.(it lines up the molecules to aid burning apparently!!!) Should we also 'take this on board'?

Now if you want another example of 'real life' savings, take the post above by Albyota who works in the plumbing industry. He has described his solar thermal system in detail - with 4 square metres of panels.

He posted earlier in this thread that in over 2 years use he had saved £130 in gas and is now removing the panel from his roof. So his savings are in the same region that WHICH suggest is typical i.e. £55 pa.

Another example of frankly obfuscation is this claim that 'technical advances' have improved output significantly since the Government tested 8 systems of both types. e.g.

You question the technical manager's knowledge.

WHICH's solar expert still states £55 pa saving. Is that not with modern tecnology?

Albyota correctly states that the system is essentially panels of copper tubes with electronics to stop them acting as a radiator at night. His system is 2 years old.

As stated earlier there have been other posts by people who bought a house with solar thermal fitted, who have reported savings less than WHICH or Albyota state.

I have investigated solar thermal both in UK and abroad before reaching my conclusions - and I am a Chartered electrical engineer.

I have read WHICH's report and don't detect the same enthusiasm for solar thermal other than it is 'green' and, as you surmise, their very long 'payback period' even with the proposed RHI subsidies clearly don't take into account loss of interest in capital invested.

From a money saving aspect the evidence is overwhelming. By any form of realistic calculations your savings are going to be £30 to £80 a year and you will lose around £150 a year in lost interest(compounded).

I can understand that my posts upset you, and that is not my intent.The sole purpose of this discussion is to make anyone who is contemplating solar thermal aware of the economic realities.

green_as_grass

albyota

You give a good clear description of how the panels work with a differential temperature controller. I'm concerned that yours is only working when the temperature difference reaches 15 to 20 degrees. Is the temperature differential adjustable with your controller? The advice I've read indicates 10 degrees difference is around the optimum. Your trying to get a balance between the temp difference being too small - not worth the electricity used to operate your pump - and the temperature difference being too large - your panel sitting at a high temperature, losing its heat to the surroundings, while your tank is not getting heated. I suspect an even lower temperature difference (than 10 degrees) might be better for flat panels since they lose heat at a faster rate while sitting idle.

I think you're losing the benefit that can be gained from 'low grade' heat. Imagine at this time of year when it is cloudy, but still bright. You open your car door, get in and instantly feel the warmth. The sun has heated your car through its windows even on a cloudy day. The same can happen with solar panels if the temperature differential is adjusted to the optimum for your system.

This might explain why you say that, even at this time of year, 'when it's cloudy... you get nothing'.

Do you have the opportunity to test this out before you rip out the panels? If so I'm sure we'd all like to hear the results. You might even change your mind if you get the results I would expect!

You might consider describing your system in full detail (maybe with a circuit diagram) in a post on the Navitron Forum, along with your disappointing results. The clever chaps there may well have other ideas on how to optimise your system.

I agree that the concept of solar water heating is a simple one, but there is a lot to take into account if you really want an efficient system.

Your tip on timing your boiler input so that it doesn't override the opportunity for the solar panels to heat the tank is a valuable one. Another reason I suspect why some unaware users don't get the benefits they hoped for from solar thermal.

And yes, solar thermal is not a practical solution for space heating - the very time you need the most heat is when there is least input from the sun. I've read speculation that with an enormous array of panels and an 'inter-seasonal store' (a vast tank with vast amounts of insulation) it could be possible - but who could afford the money or the space? Now that would have Cardew tearing his hair out if I suggested it as a viable proposition :-D !!

green_as_grass

Cardew

I'm touched at your concern that your posts might be upsetting me. And a little amused, because I was beginning to think that my persistence was irritating you! I guess your concern for my feelings shows you're taking it all in your stride.

No need to worry for me - I'm not the sensitive type - I enjoy a good robust argument.

My persistence is not out of irritation, or out of a desire to justify my expenditure, but out of a desire that people not be put off a technology that I believe can not only benefit the individual in saving them money, but also benefit the environment for us all.

I have read some of your posts in other topics and admire your no-nonsense approach, and the way you help readers by putting posters' comments in context of their other previous posts, identifying patterns of their arguments and their motivations (eg. being sellers of the equipment whose virtues they are extolling).

However, there are some aspects of your style that I have found unhelpful in this topic because they give the impression that you are irritated and they are not informative to other readers:
- repeating the same point in almost every post ("your savings are going to be £30 to £80 a year and you will lose around £150 a year in lost interest")
- ignoring some points altogether (expected escalation in energy prices, list of advances in design/installation, figures being based on systems which are mostly poorly designed and installed rather than on the best systems)
- dismissing some points without giving a reasoned argument (people who give examples of their substantial savings are zealots)
- making global statements ("your posts are FULL of obfuscation")

You haven't pointed out any specific points I've made which are unclear. I would be glad of the opportunity to clarify if you did this. Don't you think this would be a more constructive approach?

I do apologise for any 'obfuscation' but I have tried to answer each and every one of your points in a reasoned way. I really would appreciate you doing the same for me.

I hope you don't find these criticisms offensive - that is not my intention - I simply want a constructive discussion that will benefit you, me and everyone else reading.

When I get my system up and running and discover how efficient it is, or is not, I will gladly return and either gloat or eat humble pie! I'm not proud ;-).