The Great 'Get Paid To Generate Energy' Hunt

albyota

green_as_grass wrote: »

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.

the controller is quite clever in that, at lower tank temperatures, a lower differential would be applied, 10 degrees, at higher tank temps a larger differential, as I said, if water is already hot you cannot heat it further with the same temperature water, therefore as time elapses, the sun moves further past the panels and without stratification in a twin coil cylinder, the water temperature at the lower part of the cylinder stays quite warm, all this happens automatically during the day whilst we are out....not drawing off hot water, once the cylinder has gained all it can from the solar panels that is it! until the next sunny day. Remember, we are almost half way through the year and I can count on one hand, maybe two, the amount of really decent yields from the kit.


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.

They only sit idle if the sun doesn't shine......which is most of the time.....we are in the UK you know....!!!

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'.

Take my word for it, if it ain't sunny or warm the yield is nothing or very little, and believe me, I know how to optimise the system, heat loss calcs heating systems, controls, and energy saving is my job.

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!

If....in the UK we had regular 'weeks or months' of warm sunny days, I would probably keep them, but we don't and since they are in the way of me maxing out the roof area with PV panels, then they have gotta go!!

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 think, I am one of those clever chaps , maybe cleverer.....as even with the setup I have with the optimisation and control, and knowing how much water we as a family use, therefore allow the cylinder to be cool enough for maximum yield following day, and holding off the heat pump from heating the water until evening time when the sun has gone.

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.

I think I still am sensible enough to realise that spending £2.5K on my (for most of year) roof orniments that save me £50/yr, that I still might be able to sell them to some unsuspecting sucker, for near what I paid for them....however I have a conciense.

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.

As you see, it is not all about technology...its about common sense and some basic school boy physics.......I must have had a day off sciving and turned in that day....

lets be clear...I used to rave about my panels....how much hot water we got......for 'free'....until you actually do the maths, I am in the renewables industry and we are an MCS installer of air source heat pumps, and often get asked if we can quote for solar thermal, and I tell it exactly how it is.....we do not and will not be fitting it, there are enough country & western salemen riding in from all over, some selling at £3.5 - £4k installed, some ripping off at £8k+ for the same kit, my advice is...don't waste your money.

My Dad has a DIY panel on his leanto roof, a 4ft x 2ft radiator...painted black under a bit of glass....no pump....no controller.....purely gravity...hot water rising to cylinder slightly higher in the airing cupboard, it cost him £30 for the radiator, and a sheet of glass and has been in operation for over 20 years, he has had many showers and baths for free, his pay back was probably in the first year.

Solar thermal can work.... in the right application, like a hospital, school or care home, using large amounts of hot water, but the storage of the hot water becomes an issue.

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 !!

hope this helps some of you who are considering shelling out your hard earnt on some roof orniments.

John_Pierpoint

I note that you have an air (?) source heat pump.
Does it use the new fangled inverter technology or is it a traditional "starts with a thump" one that flickers the lights?
As a potential user of a heat pump, I ask this because my local electricity supplier in this area (EDF) has no experience of heat pumps. I have heard, what are more than rumours, about the local engineers getting twitchy about the effect of both types of motors on the local grid.
Could there be any adverse interplay between the heat pump and the PV panels you are proposing to install ?.

Cardew

Green as Grass,

This is a money saving website and there can be no question IMO but that solar thermal will cost anyone, who pays to install such a system, money year on year.
The problem in any discussion on such a subject is that we get sidetracked into discussing extraneous issues. It seems that the proponents of solar thermal have a vested interest in pursuing this course.

You, as a proponent, appear to pin your arguments the proposition that modern technology has dramatically changed the situation. You stick to this position despite overwhelming evidence to the contrary – Government sponsored tests of 8 systems, WHICH report from last month, Albyota’s experience, manager of a solar firm etc

Why should I not keep repeating the statement that “anyone fitting solar thermal will save between £30 and £80 a year and lose £150 a year in interest”. It is the crux of the argument, I have given plenty of evidence to support that statement and no amount of discussion on peripheral issues can change that situation.

So let me try another tack.

For a £4,000 solar thermal system I state that the average annual saving is approx 1,000kWh thus £30 to £80 depending on fuel, and that a reasonable expectation of future fuel inflation is 5% pa. You lose approx £150 a year in lost interest compounded.

So are you prepared to give your estimate along similar lines?

yakky58

Cardew is right low generation in the winter but you have to take the whole years generation into account. The next two quarterly bills will be free based on the last two years. that I think is money saving now and part of the payback process.

The DIY part is true. However, that was in effect two days work to to place arrays on the roof and do the wiring, not an onerous task at all. I had the company sign off the electrical part and Southern Electric arrived on queue to install a free export meter.

Ongoing work is twice yearly clean with a hose that takes 30 mins. Not very hard work.

Registering with Ofgem as a generator was far harder with the forms but its a one time only job.

I also have solar thermal and I whilst I invested about £3,000 in this I have to agree with Cardew the returns have been poor. It great in the summer but I use less hot water.

albyota

Quote:
I note that you have an air (?) source heat pump.
Does it use the new fangled inverter technology or is it a traditional "starts with a thump" one that flickers the lights?
As a potential user of a heat pump, I ask this because my local electricity supplier in this area (EDF) has no experience of heat pumps. I have heard, what are more than rumours, about the local engineers getting twitchy about the effect of both types of motors on the local grid.
Could there be any adverse interplay between the heat pump and the PV panels you are proposing to install ?.'

yes john, the air to water heat pump is the Mitsubishi Ecodan and is inverter driven, ignore the comments from EDF and the like they do not have a clue!!!, however, if everybody suddenly switched over to heat pumps then the national grid would fall over until new, clean green electricity is mixed in.

The Feed in Tarrif for the Solar PV array I will be installing will generate enough leccy to wipe out my bill. the RHI (if it happens) will pay me about £1,100 for a good few years, so for the 10,000 kWh I use in a year, it really does stack up....for me anyway.

zantos

I have had solar PV installed and working quite happily now for over a month. Today suddenly my system won't synchronise with the mains supply and just shows "waiting" on the inverter display. According to the installer this is a problem with the local electricity supply and could be an over-voltage situation on the mains (I have measure thiis at 245v so seems unlikely), or a difference in phase between the two systems. Anyway they say it is the electricity boards problem as I am techincally generating electricity that just isn't going anywhere and as it doesn't show on the export meter I don't get paid.
Has anyone else had problems like this and if so how have they resolved them?

Dave

Mcfi5dhc

zantos wrote: »

I have had solar PV installed and working quite happily now for over a month. Today suddenly my system won't synchronise with the mains supply and just shows "waiting" on the inverter display. According to the installer this is a problem with the local electricity supply and could be an over-voltage situation on the mains (I have measure thiis at 245v so seems unlikely), or a difference in phase between the two systems. Anyway they say it is the electricity boards problem as I am techincally generating electricity that just isn't going anywhere and as it doesn't show on the export meter I don't get paid.
Has anyone else had problems like this and if so how have they resolved them?

Dave

I've not had any problem like this with my system, so I've no advice, sorry. However, it does actually seem that you are the first on these forums to have a problem with Solar PV. At least your installer is helping you though (which they obviously should do)

One thing though, I always thought the mains was at 230v, not 245v.

Can you post your make and model of equipment (especially the inverter) so I/we can have a google at the error messages? Thanks

PS As a matter of interest, a little scroat near me tried to steal some cables from one of the local sub-stations. Unfortunantly, he survived.:mad: But we lost power for a couple of hours which the fire was put out and the reapirs made. We lost power like everyone else, but about 3 minutes after the power came on, I started exporting again. i didn't have to do anything, no switched to flip etc. Its the 1st power cut I have had since installign the PV, so I really didn't know what to expect.

zantos

Inverter is a Sunny Boy SB2500 driven by Sanyo HIP-215NKHE5 panels. The only time that the display has shown "waiting" in the past was when it was first installed, since then even when it is not generating this message has never appeared.
According to my installer they have had similar problems where EON have had to install monitoring equipment to find the fault and it has taken up to three months! Not something I would like especially with all the fine weather. So far the syatem has ben "offline" for approximatley six hours as it usually starts aroung 7 o'clock and runs through until seven in the evening.

Mcfi5dhc

Same inverter as mine (I think)

Does this help:
http://download.sma.de/smaprosa/dateien/5688/SB25_30-IEN092520.pdf

Is there any chance your panels could be in contact with anything metal (like wires) that could be causing a short circuit? (I'm thinking off the top of my head here, I am NOT in the solar industry and i am NOT an electrician)

Was your installation company good? Or did you have any problems with them? I would have thought they'd come out quite quick - they should have all the equipment to diagnose any faults ( I know they have done a phone diagnosis, but surely they have a duty to actually come out)

zantos

Mcfi5dhc wrote: »

Same inverter is mine (I think)


Is there any chance your panels could be in contact with anything metal (like wires) that could be causing a short circuit? (I'm thinking off the top of my head here, I am NOT in the solar industry and i am NOT an electrician)

Was your installation company good? Or did you have any problems with them? I would have thought they'd come out quite quick - they should have all the equipment to diagnose any faults ( I know they have done a phone diagnosis, but surely they have a duty to actually come out)

Thanks I've got the manual on the Inverter - they left me with it. Mains voltage now is 248-249v still within the allowable 10%. Just gave the installer another call and he is going to contact EON and see what they have to say. The inverter shows that the panels are putting out about 284v at the inverter it's just that the inverter and mains won't "talk" to each other to do anything. I'll keep monitoring the mains to see whether anything happens if the voltage drops nearer 230v although at the moment everything is within specification, only thing possibly wrong is the mains frequency which I can't be bothered toget my scope out to check! Will let you know the outcome - just in case you ever suffer a similar problem but at the moment it seems like there is nothing to do but wait. Just picked up on your "phone diagnosis" all they got me to check was the voltage at the inverter and whether there were any error messages, which seems fair enough as that is all there is to see on my side of things - probably need a data logger fitted by EON to find anything else out. They won't be happy if it's there supply that's out of spec as it will cost a bit to rectify it.