Are you all pleased with your solar panels for hot water heating

JDoubleU · 29-03-2014 4:10pm

Bryan, I've already read the thread and while there's some useful info in it, there's not much on savings. The new thread was for specifics on savings.

championc · 29-03-2014 9:07pm

I think a well installed, properly sized, well located, Evac Solar Tube system should pay for itself in about 10 years

goat2 · 02-04-2014 4:30pm

at least when i asked a guy about this solar water heating system,
fair dues to him,
he told my roof was not suitable due to direction, he saved me money and time as well as being disappointed,
when i consider that a load of logs will heat radiators and hot water, at least the money will last a fair few yrs with a good output

John T Carroll · 02-04-2014 5:13pm

JDoubleU wrote: »

I'm interested in solar thermal panels and the savings they provide. It would be great to hear from people (not companies) who have realised actual savings from solar thermal. I'm interested to know:

Your savings are in Euro.
If you have tube or flat plate
What direction they face.
Hot water or hot water & heating
What part of the country you live in.
What convinced you to buy that particular panel e.g. were you fed bs on savings etc. I have come across one company who shall remain nameless and have to say I'm not impressed with their BS.

I know savings will vary for each home depending on use but it would be great to see differences and get a real picture of what's out there.

Thanks in advance.

If you read my very first post and then go to page 3 of my posts to "2013 Solar output" then go to Cell E421 of the attached Spreadsheet then that will give you a very good feel, in my opinion, for the real savings of a Flat Plate Panel set up. If you want to compare it with the "usual" Three Flat Plate + 300 litre cylinder just multiply by a factor of 1.5. An Evacuated Tube Array, should give an additional 25% to 30% increase in savings, in both cases.

db · 08-04-2014 9:23pm

cost $6K approx
year of installation 2013
m2 area 40 tubes
orientation SW 35 degree slope
flat plate or tubes tubes
cylinder size 300L
summer heat dump strategy ( if any ) None

Moved in last August and delighted with the solar performance. Water would be hot enough for showers up till end of October, about 40deg at the top, a bit cooler in Nov and down to about 20deg in Dec with the occasional good day when there was a bit of sun. Since the start of Feb the water in the evening would increase week by week and it is above 40deg most days at this point. Last week we had a couple of days >50deg top and bottom of the cylinder.

Even when there was little heat from the sun in the middle of winter, it took very little to heat the water with the oil boiler. We never had to run the boiler for more than an hour to bring the water up to temperature.

Qualitymark · 11-04-2014 12:56am

db wrote: »

cost $6K approx

Dollars?

Jakey Rolling · 14-04-2014 4:04pm

Had ours installed as in 2012 as it was a new build and more or less required to meet the Part L regs for renewables.

Cost €5000 inc cylinder
30 tubes with parabolic reflector
South facing roof at 35% pitch
300l cyclinder
No heat dump

What I can comment on is this.
We save about the equivalent of 300 litres of oil over the year.
This is about €250 at current prices.
So payback would be 20 years nominally
That's ignoring any maintenance, fluid replacement, eventual pump replacement.

So I wouldn't see solar thermal in any way as a cost saving measure, but it does feel good to have the tank at 65C on a day like today.

Our setup appears to be slightly oversized.
Good in that we had water up to 40C in Dec and Jan on solar alone.
Bad in that it spends most of the time stagnating, reaching 195C in summer. Don't believe this is good for the anti-freeze additive witch states max temp of 180C.

The slight problem with this is that the system stops pumping at 120C, so if I went and had a bath now, using up the hot water, the solar won't start reheating the tank until the top end drops back below 120C in the evening. Not normally a problem, but could catch you out at times.

josip · 14-04-2014 4:21pm

Jakey Rolling wrote: »

Had ours installed as in 2012 as it was a new build and more or less required to meet the Part L regs for renewables.

Cost €5000 inc cylinder
30 tubes with parabolic reflector
South facing roof at 35% pitch
300l cyclinder
No heat dump

What I can comment on is this.
We save about the equivalent of 300 litres of oil over the year.
This is about €250 at current prices.
So payback would be 20 years nominally
That's ignoring any maintenance, fluid replacement, eventual pump replacement.

So I wouldn't see solar thermal in any way as a cost saving measure, but it does feel good to have the tank at 65C on a day like today.

Our setup appears to be slightly oversized.
Good in that we had water up to 40C in Dec and Jan on solar alone.
Bad in that it spends most of the time stagnating, reaching 195C in summer. Don't believe this is good for the anti-freeze additive witch states max temp of 180C.

The slight problem with this is that the system stops pumping at 120C, so if I went and had a bath now, using up the hot water, the solar won't start reheating the tank until the top end drops back below 120C in the evening. Not normally a problem, but could catch you out at times.

Since it was a new build, you would have needed a cylinder anyway, regardless of panels, so I think you're being hard on your system by including the full cost of the cylinder.
Were there any grants for solar still around in 2012?
Have you considered installing a blind for your panels? I remember seeing them advertised but can't find them now.

freddyuk · 14-04-2014 6:59pm

A simple by pass via a radiator is a cheap way of diverting the sting from the system. One diverter valve some pipe and a standard radiator cost about the half the cost of having the fluid replaced. Most decent controllers have this function included. It helps prevent all the system components being stressed leading to early failure. "A properly designed system does not need a bypass" is often quoted but how can you design a thermal system that provides sufficient hot water in winter and does not stagnate in summer. It only takes one very hot day to have a steam event and cause damage to glycol, expansion vessel etc. if there is no where for the heat to go. There is the argument that in an attic the ambient temperature is aready too high to be able to dump the heat but we are talking 120c + in the system. I would rather have the dump and have a good chance of saving my system if I am away on a belter of a day.
Kingspan have an inbuilt "safety" system but they do not really want to have to pay out if it fails hence the warranty terms and it's effectiveness is in some doubt. Maybe others will have an opinion on that.
There are high quality Glycol solutions that do not need replacing after stagnation but I doubt any standard system will have this used.
Using blinds is not an option if the panels are on the roof and automatic blinds are going to be likely to fail after a couple of winters.
Just my opinion but interested in expert views on this.

Jakey Rolling · 14-04-2014 11:16pm

freddyuk wrote: »

A simple by pass via a radiator is a cheap way of diverting the sting from the system. One diverter valve some pipe and a standard radiator cost about the half the cost of having the fluid replaced. Most decent controllers have this function included. It helps prevent all the system components being stressed leading to early failure.

Thanks for that - I will have to quiz my plumber on this, as you say, the system components are being stressed by this continual stagnation.

What I can't work out is what size radiator would be needed to effectively dump the excess. Given that the aperture of the tubes is approx 3m2 then at most you would expect continuous 3kW heat to be transferred, if solar radiation is approx 1kw/m2. However the controller often shows power up to 20kW, presumably based on temp difference, flow rate and specific heat capacity. I'm not so keen on plumbing a rad in a cold attic. Wouldn't it need glycol in the circuit too?

John T Carroll · 15-04-2014 7:14am

Jakey Rolling wrote: »

Thanks for that - I will have to quiz my plumber on this, as you say, the system components are being stressed by this continual stagnation.

What I can't work out is what size radiator would be needed to effectively dump the excess. Given that the aperture of the tubes is approx 3m2 then at most you would expect continuous 3kW heat to be transferred, if solar radiation is approx 1kw/m2. However the controller often shows power up to 20kW, presumably based on temp difference, flow rate and specific heat capacity. I'm not so keen on plumbing a rad in a cold attic. Wouldn't it need glycol in the circuit too?

I would say that a 2 Kw Dump Radiator would be adequate even with an ambient temperature of 20C, you can do your own calculations on the attached spreadsheet. Yes there would be glycol in the system as it becomes part of the whole primary circuit and would also include a three way diverter valve and a suitable solar controller, quite alot of controllers have this facility, your's may already have it. The central heating system itself can be utilised but is a bit messy especially with systems with zoning, there are some posts out there regarding this.
The 20 Kw power indication may wrongly be a "12 or even a 24 hourly" number, power as distinct from energy is based on an hourly calculation. A 3 M2 evacuated tube array wouldnt give, in my opinion, more that 2.2 Kw even in a very sunny day.

freddyuk · 15-04-2014 8:26am

Don't forget you need a solar rated diverter valve not a simple 3 way motorised valve. A 60 x 40 double rad finned should give you about 1kw under normal conditions and cost under €50. You don't need rad valves just male - 15mm compression.

Jakey Rolling · 15-04-2014 9:47am

Having had a look through the solar controller menu, and downloaded the manual it doesn't seem my controller has the option of operating a divert valve for heat dumping. The only related option for "Collector protection" is to force the pump on at predetermined temperature, but this just feeds to the normal storage tank - suitable if you had a swimming pool or large accumulator possibly!

It looks like this would be a pain + cost to change, as the controller is integrated into a "Solar Station" package. FYI, the controller is an "STDC" made by Sorel Mikroelektronik, rebranded as "ModvSol".

Jakey Rolling · 15-04-2014 9:57am

John T Carroll wrote: »

The 20 Kw power indication may wrongly be a "12 or even a 24 hourly" number, power as distinct from energy is based on an hourly calculation. A 3 M2 evacuated tube array wouldnt give, in my opinion, more that 2.2 Kw even in a very sunny day.

The power seems right enough, as with a temp difference of 20C and flow rate of 12litres/min that gives about 16kW (using c * m x dT ). The pump is switched on once the temp difference is >9C, but it seems there is some initial overshoot in collector temp after the pump has started circulating. Steady state it is closer to 2kW as expected.

Anyhow, I'm happy that the controller's calculations are ball-park correct as it's giving approx 10kWh over a day, with 5 hours operation and average 10C temp difference between collector and storage. That works out at an average of 2kW while in operation, so about right.

John T Carroll · 15-04-2014 2:42pm

In view of that you might consider using the Central heating as a dump, I use mine very occasionally in a "manual" mode to see how it functions. I have no problems with stagnation as I have a Flat plate set up and I have the max cylinder temperature setting at 80C, I have soft water so no scaling problems. The cylinder (oil fired) heating coil is 0.65 M2 which is probably typical of a lot of installations. When "dumping" I have an isolating switch on the electrical suppy to the oil burner which I switch off. I manually open the oil fired coil motorised valve to the hot water cylinder, I put the Timer to constant ON and then simply turn the room stat to its maximum setting of 30C which starts the C.Heating pump, I have two radiators (approx total 3 kw output) which do not have thermostatic valves so the water circulates through them. It seems to have no problem in removing excess heat from the cylinder. It wouldnt be too difficult to "automate" this. You could fit a simple differential temperature controller with a cylinder surface mounted sensor about a 1/4 to 1/2 way "up" the heating coil to give
a fairly representative temperature measurement. It may be worth looking at the heating coil area, in lots of cases. this is now 1.0 M2.

freddyuk · 15-04-2014 9:06pm

Jakey Rolling wrote: »

Having had a look through the solar controller menu, and downloaded the manual it doesn't seem my controller has the option of operating a divert valve for heat dumping. The only related option for "Collector protection" is to force the pump on at predetermined temperature, but this just feeds to the normal storage tank - suitable if you had a swimming pool or large accumulator possibly!

It looks like this would be a pain + cost to change, as the controller is integrated into a "Solar Station" package. FYI, the controller is an "STDC" made by Sorel Mikroelektronik, rebranded as "ModvSol".

You seem to have the most basic version but there is a heat transfer option? Maybe this can be used to dump heat rather than transfer it to another cylinder? Instructions seem a bit lacking unless you have a complete operators manual. If it will transfer heat at a set temperature then just put this through a radiator as it is simply a TDC.Is there a terminal for this purpose?

Jakey Rolling · 15-04-2014 10:40pm

freddyuk wrote: »

You seem to have the most basic version but there is a heat transfer option? Maybe this can be used to dump heat rather than transfer it to another cylinder? Instructions seem a bit lacking unless you have a complete operators manual. If it will transfer heat at a set temperature then just put this through a radiator as it is simply a TDC.Is there a terminal for this purpose?

I have downloaded what appears to be the complete operation manual - as above, no mention of heat dump facility, or any heat transfer to anything other than the primary storage (in my case a 300l pressurised cylinder).

My plumber said he has similar sized systems working 4+ years without a problem. To be fair, pressure seems well regulated when stagnating, due to the expansion vessel. Stays between 2 and 3 bar.

I'll look at costs of suitable controllers. Can I assume that another unit would work with the same thermocouples that are in place?

John T Carroll · 16-04-2014 2:13pm

Jakey Rolling wrote: »

I have downloaded what appears to be the complete operation manual - as above, no mention of heat dump facility, or any heat transfer to anything other than the primary storage (in my case a 300l pressurised cylinder).

My plumber said he has similar sized systems working 4+ years without a problem. To be fair, pressure seems well regulated when stagnating, due to the expansion vessel. Stays between 2 and 3 bar.

I'll look at costs of suitable controllers. Can I assume that another unit would work with the same thermocouples that are in place?

Personally, I wouldnt even dream of allowing any system stagnating which can result in collector/system temperatures of up to 250C. This was the main reason I didnt go for E.Tubes at the time. After x years when the system starts degrading for whatever reason, one will say I wonder would it have done y more years if I had had a heat dump fitted.

If you do decide to retrofit a Controller capable of dumping then you might find one that looks at the STORE temperature as its measurement (for dumping only) and not the cylinder temperature. Quentingargen explains the problem with using the cylinder temperature quite well in one of the "Solar Heat Dump" posts. It probably would be prudent to change the solar fluid as well as this may have degraded even though this would not have reached 250C, its more than likely that it would have reached temperatures roughly corresponding to the saturation temperature as this is the temperature that the panel starts blowing down into the expansion vessel, the remaining vapour is then superheated on up to say, 250C. The saturation temperature at 2 Bar (gauge) is 134C, at 2.5 Bar is 139c & at 3.0 Bar is 144C.

The new controller should be compatible with the existing sensors if they are PT1000. I think most modern systems use PT1000 probes now. Its quite easy to measure the resistance on one probe by disconnecting it, if not sure. In any even, check with the supplier of the Controller.

Caracol · 21-05-2014 2:11pm

sinnerboy wrote: »

I'll sticky this awhile and add

Please indicate

cost
year of installation
m2 area
orientation
flat plate or tubes
cylinder size
summer heat dump strategy ( if any )

Reminder - no trade / company names please

.

cost : 6570 euros (including scaffolding)
year of installation: 2014
m2 area: 40 tubes (Kingspan thermomax)
orientation: South West
flat plate or tubes : tubes
cylinder size: 300L copper triple coil
summer heat dump strategy: 2 heat dump radiators in attic
Controller: Resol C4

House currently has 3 zones
Zone 1 upstairs rads
Zone 3: downstairs rads
DHW

Very happy so far:
On a sunny day in May temps go up to 50s in bottom of cylinder and high 50s in top of cylinder
On a mixed / cloudy day in May, temps in the 40s which is ok for bath and showers.

mickrick1 · 20-06-2014 1:00pm

Hi Guys - I installed solar panels in our bed and breakfast back in March 2011. Everything seems to be fine, although I have no scientific data to back this up.

Just wondering do I need to ensure that heat transfer fluid is still at the same level as when panels were installed. How can I check this? Do I need to get a professional in? I have a drum of the fluid in the garage.

Any suggestions would be much appreciated.

Mick.

josip · 20-06-2014 1:31pm

Mick, I'm a user not a professional, but my understanding is that it's usually a closed system with an expansion vessel. I think the fluid only vents in extreme situations.

Any time we've had a bubble in the system, I've called in the installers since the system had to be drained.

Very open to correction from pros

ccsolar · 20-06-2014 1:55pm

mickrick1 wrote: »

Hi Guys - I installed solar panels in our bed and breakfast back in March 2011. Everything seems to be fine, although I have no scientific data to back this up.

Just wondering do I need to ensure that heat transfer fluid is still at the same level as when panels were installed. How can I check this? Do I need to get a professional in? I have a drum of the fluid in the garage.

Any suggestions would be much appreciated.

Hi Mick
Check the pressure gauge at the side of the pumping station
If it's between 1-2 bar your system should be fine
Best to check it late evening.

Cc

mickrick1 · 21-06-2014 12:25am

ccsolar wrote: »

mickrick1 wrote: »

Hi Guys - I installed solar panels in our bed and breakfast back in March 2011. Everything seems to be fine, although I have no scientific data to back this up.

Just wondering do I need to ensure that heat transfer fluid is still at the same level as when panels were installed. How can I check this? Do I need to get a professional in? I have a drum of the fluid in the garage.

Any suggestions would be much appreciated.

Hi Mick
Check the pressure gauge at the side of the pumping station
If it's between 1-2 bar your system should be fine
Best to check it late evening.

Cc

Cheers CC.

I checked pressure gauge last night and it was at 0. Can you tell me how to reset it. I have reset pressure gauge before on our hot water system by using a flat screwdriver. Can I do something similar here?

Thanks

Mick.

ccsolar · 21-06-2014 1:08am

mickrick1 wrote: »

ccsolar wrote: »

Cheers CC.

I checked pressure gauge last night and it was at 0. Can you tell me how to reset it. I have reset pressure gauge before on our hot water system by using a flat screwdriver. Can I do something similar here?

Thanks

Mick.

Hi Mick
0 pressure basically means you have a small weep/leak in your system
Check all joints for signs of a leak possibly staining on insulation but you need a special pump to fill system and flush out air
Try hiring at a plumbing shop or get an expert to service and repair leaks
Sorry it's not better news

Cc

John T Carroll · 21-06-2014 8:29am

ccsolar wrote: »

mickrick1 wrote: »

Hi Mick
0 pressure basically means you have a small weep/leak in your system
Check all joints for signs of a leak possibly staining on insulation but you need a special pump to fill system and flush out air
Try hiring at a plumbing shop or get an expert to service and repair leaks
Sorry it's not better news

Cc

Before re filling the system, ensure that the expansion vessel pre pressure is checked, it should be around 1.5 to 2.5 Bar.

My system pre pressure was 2.5 Bar (cold evening) and the installer continued pumping until he had 2.8 Bar on the liquid side pressure gauge. This should have pumped about 1.4 litres of water/glycol into the 18 litre expansion vessel, this should serve two purposes, it will act as a cool buffer for the expansion vessel in the event of stagnation and it will make up any small air pockets that might remain after commissioning. I got tiny quantities (bubbles) for about 10 days when I cracked open the manual vent on the Deaerator or the Air Catcher as they call it in the USA. Make sure that too much liquid is not pumped into the expansion vessel as it wont hold the blowdown contents in the event of stagnation.

mickrick1 · 21-06-2014 10:52am

Any ideas on a good person to look at my system in Galway?

championc · 21-06-2014 6:08pm

Got my RPi outputting the data once again

https://xively.com/develop/Y9cJha4J1gxxCijlJKkW

John T Carroll · 21-06-2014 10:11pm

championc wrote: »

Got my RPi outputting the data once again

https://xively.com/develop/Y9cJha4J1gxxCijlJKkW

It's asking for a Login+Password.

championc · 22-06-2014 1:44am

https://xively.com/feeds/1928576781

calum22 · 29-07-2014 2:44pm

Great thread!!!

I was talking to a company at last years SelfBuild show in Dublin and was unsure. This thread has definitely reinvented the possibility of solar panels at my house

jiminho · 19-08-2014 8:04pm

This question is more for new builds that have "passive haus" or almost PH standard so air tight, very insulated and good natural space heating capabilities.

Has anyone on boards used their solar thermal panels to heat their hot water and central heating? Underfloor heating would be sufficient to heat a PH and as these require to be on all the time (hot days excluded) would only need water flowing thru them at approx. 30C. This temperature is obviously well suited for geothermal where it can be produced consistently all year round but sounds like this would be well within the capabilities of solar panels. Obviously a bigger system would need to be installed but as any system gets bigger, surely it would become more cost effective. Has anyone ever heard of this been done in Ireland or UK?

19-08-2014 8:11pm

I am in the process of installing a system that consists of 2 x 20 tube collectors in a SE & SW configuration, I don't expect it to provide sufficient heat for the UFH but I hope to offset some of the energy required so that I'll need to load the turf boiler less.

BryanF · 19-08-2014 8:17pm

jiminho wrote: »

This question is more for new builds that have "passive haus" or almost PH standard so air tight, very insulated and good natural space heating capabilities.

Has anyone on boards used their solar thermal panels to heat their hot water and central heating? Underfloor heating would be sufficient to heat a PH and as these require to be on all the time (hot days excluded) would only need water flowing thru them at approx. 30C. This temperature is obviously well suited for geothermal where it can be produced consistently all year round but sounds like this would be well within the capabilities of solar panels. Obviously a bigger system would need to be installed but as any system gets bigger, surely it would become more cost effective. Has anyone ever heard of this been done in Ireland or UK?

This thread is about solar water heating?
Solar panel space heating is not suitable for Ireland. Start a new thread if you want further discussion.

ccsolar · 20-08-2014 9:49am

[Deleted User] wrote: »

I am in the process of installing a system that consists of 2 x 20 tube collectors in a SE & SW configuration, I don't expect it to provide sufficient heat for the UFH but I hope to offset some of the energy required so that I'll need to load the turf boiler less.

Hi
2x 20 tubes in SE/SW is ok but I wouldn't get over excited about the performance if connected to a 300 litre tank
You would be better off in the long run to spend a further €600 and fit 2 x 30 East / West system
Might also want to consider the Nous system or thermodynamic system
Before you proceed you should really talk to someone that has an east west system installed and get there opinion.
Cc

championc · 20-08-2014 10:45am

IMO - To add, the main months of gain, where you will have excess heat, will be during the summer months, the one time of year when I would expect that you would not be using your UFH. So complexity in controls and maybe pipework may indeed outweigh the benefits. You might do a bit better during Spring and Autumn if you have a dual coil buffer tank with a diverter valve and top load it. Obviously, the buffer tank would need three coils then, with the top one connected to your CH / UFH

jiminho · 20-08-2014 3:38pm

championc wrote: »

IMO - To add, the main months of gain, where you will have excess heat, will be during the summer months, the one time of year when I would expect that you would not be using your UFH. So complexity in controls and maybe pipework may indeed outweigh the benefits. You might do a bit better during Spring and Autumn if you have a dual coil buffer tank with a diverter valve and top load it. Obviously, the buffer tank would need three coils then, with the top one connected to your CH / UFH

Very true, it's just something i'm looking into as it would be great to have a single system. I've looked back thru the pages but I don't think you've mentioned it, can i ask how many people are in your household? Would the norm be each person has a single shower per day - in the morning or at night? I've looked at your graphs (which are great data btw) but what's your opinion of winter time - do you have a gas system that needs to "top up" during the cold months and if so, how much i.e. 20%, 50%? Lastly, what's your opinion of the temperature of the water when having a shower - are you ever cursing to yourself that it could be a bit warmer or is it the same as a normal shower? Cheers

Iamhere · 25-08-2014 9:07am

Hi,

Looking for some advise if possible, looking into solar tubes at the moment and finding it hard to get a clear idea on the best setup for our house.

House was built in 1999, it has 2 en-suite showers (1 mixer shower, 1 electric shower) and an electric shower in the main bathroom.

I have got two quotes so far, both have suggested 20 tubes, with 240/250 litre copper cylinder (dual coil).

We are currently heat water for the likes of a bath using the oil central heating as the immersion is faulty and i have been advised it would be best to replace the current copper cylinder.

There are 2 adults and 1 2 year old in the house at present but we would be hoping this would change to 2 or 3 small people over the next few years.

The house is west facing so i am wondering would 20 tubes and the cylinder size above fit our needs, also id prefer to get a stainless steel cylinder but this is just based on how they look rather than anything serious

Thanks in advance.

25-08-2014 4:21pm

ccsolar wrote: »

Hi
2x 20 tubes in SE/SW is ok but I wouldn't get over excited about the performance if connected to a 300 litre tank
You would be better off in the long run to spend a further €600 and fit 2 x 30 East / West system
Might also want to consider the Nous system or thermodynamic system
Before you proceed you should really talk to someone that has an east west system installed and get there opinion.
Cc

I had already started the installation so no going back really, anyway finished it at the weekend and so far so good.
Saturday(just the late afternoon), despite it being mostly overcast did bring the tank up to 50c since then the weather has been awful and the panels are only getting up into the low 40s, so no useful heat there.

josip · 25-08-2014 4:36pm

Deleted User wrote: »

panels are only getting up into the low 40s, so no useful heat there.

Panels at low 40s would give a cylinder temp of mid 30s in our config.
Which is almost 20 degrees of lift over incoming water temp.
Is it because your cylinder temp was up to 50C on Saturday that you don't consider it useful?
If you've used any water since Sat, then the 40C+ at the panels should have heated the bottom of your cylinder to mid 30s?

25-08-2014 4:57pm

josip wrote: »

Panels at low 40s would give a cylinder temp of mid 30s in our config.
Which is almost 20 degrees of lift over incoming water temp.
Is it because your cylinder temp was up to 50C on Saturday that you don't consider it useful?
If you've used any water since Sat, then the 40C+ at the panels should have heated the bottom of your cylinder to mid 30s?

I meant in the sense that I couldn't use it for a shower or the like, but it did raise the temperature of the tank here is a screenshot of the system right now.
Note that both pumps are running and the system is providing low level heat.
The backup turf boiler is firing up and will heat the tank instead.

championc · 25-08-2014 6:08pm

Iamhere wrote: »

Hi,

Looking for some advise if possible, looking into solar tubes at the moment and finding it hard to get a clear idea on the best setup for our house.

House was built in 1999, it has 2 en-suite showers (1 mixer shower, 1 electric shower) and an electric shower in the main bathroom.

I have got two quotes so far, both have suggested 20 tubes, with 240/250 litre copper cylinder (dual coil).

We are currently heat water for the likes of a bath using the oil central heating as the immersion is faulty and i have been advised it would be best to replace the current copper cylinder.

There are 2 adults and 1 2 year old in the house at present but we would be hoping this would change to 2 or 3 small people over the next few years.

The house is west facing so i am wondering would 20 tubes and the cylinder size above fit our needs, also id prefer to get a stainless steel cylinder but this is just based on how they look rather than anything serious

Thanks in advance.

I am not an installer so I can only speak in so far as the experience I have gained and observed.

First of all, you need to be very prepared for the fact that this system will only supplement your heat generation and not replace it. So a big store of hot water will be exactly that, however, the bigger the store, the more tubes you need to get a decent return.

In Ireland, we have very few sunrise to sunset "perfect" sunshine days. So there will be many half days of sunshine. Now consider days in Spring and Autumn. With a westerly orientation, look at your roof on a sunny day - you will possibly have sunshine hitting it from about 11:00 onwards so west isn't too bad. The shallower your roof pitch, the earlier the sun will hit it.

So you really want as much heat, as quickly as possible. I have 30 tubes into 180 litres. I have a Top Loading function which essentially feeds the 30 tubes into 100 litres when the sun shines well, filling the top section with hot water before then filling the bottom section.

One part to note with my system is that I have a Combi boiler. So I have no other supplemental CH system of any kind to heat the water in the storage buffer tank. Just before I got my system installed, I met a guy locally who told me "the system is great, my water is always over 50 deg" but then he also said "I'm not sure if it's saving me much". That is obviously because his CH was still heating the water that the Solar did not do.

My gas consumption is down about 25 - 30 % so I can see a real genuine return. I am looking at gas units rather than anything to do with cost.

The live feed from my system is at https://xively.com/develop/Y9cJha4J1gxxCijlJKkW

ammc · 28-09-2014 1:29pm

Can someone advise me regarding a device for data collection. I have 30 Kingspan evacuated tubes (DF100) connected to a RESOL BS/4 v2 Controller. I can view the temp of tubes and the temp at bottom and top of cylinder on the controller. What would be the best device for recording data to view long term trends that I could connect to my system.

28-09-2014 1:45pm

I am using this, http://www.ultisolar.com/post/SR1188-Solar-Controllers-Solar-Water-Heater-Controllers-Solar-Smart-Controllers.html
it has a 4mb SD card and can send data to a PC via an RS422 link.

Sample screenshot

ammc · 28-09-2014 4:00pm

Thanks dolanbaker. Is the controller the key to recording data? Was hoping I could use existing controller and connect data recording device alongside it or would it be best getting new controller altogether. Was told I could get something to run alongside it but it was something that only measured kWh's so I could see how much money would be saved. But I'd like to see how the system is performing all round

28-09-2014 5:41pm

You should be able to log data from an existing controller if there is a data port, the only difficulty would be the program for the PC to read and log the data stream. As an alternative, you could use a separate set of sensors and logging system, here is a link to my home brew system. It used to just monitor the old solar panel but it now monitors the solid fuel boiler & buffer tank and standby oil boiler.
http://www.dolanbaker.info/weather/solar_table_chart.html

kennyb3 · 03-10-2014 1:52pm

Looking at our gas bills for 4 months for the summer, 2 bi-monthly periods - about €50 for each bill.

Standing charge of about €15 incl vat and €35 for hot water (no heating used over this period).

So I'm reckoning solar panels might save €147 (€35*6bimonthly bills *70%) per year on that basis at most.

I'll be a long time paying back the €3500 net of grant it's possibly going to cost for a Kingspan 30 tube system with cylinder & installation.

Now we've two toddlers who have little consumption at present but I'm assuming the equation will change as they get older.

Still feel like i'm missing something in terms of it being worthwhile for a lot of people.

Is it that our gas costs to heat water are low as we've a small enough cylinder at present and a brand new 91% efficiency boiler to do it?

josip · 03-10-2014 2:53pm

kennyb3 wrote: »

Still feel like i'm missing something in terms of it being worthwhile for a lot of people.

Is it that our gas costs to heat water are low as we've a small enough cylinder at present and a brand new 91% efficiency boiler to do it?

Nope, it's not worthwhile for most people.
When you sit down and add up equipment, installation and maintainence costs versus your savings my guess is that less than 10% of owners will cover their costs over their lifetime.
And it will remain uneconomical unless energy costs increase significantly during the lifetime of your system.
But if that happens, then increasing inflation will probably mean that repairs and servicing costs will increase too.

For me, it's a lifestyle choice, allowing me to feel good about myself having less of an impact on the environment. Until I consider the environmental cost of manufacturing the panels, shipping them from China, diesel burned by plumber coming out to install and fix them, emptying the cylinder of hot water before we go away in the summer since we don't have a heat dump.

I'm disillusioned, but still living the dream...

John T Carroll · 03-10-2014 3:09pm

kennyb3 wrote: »

Looking at our gas bills for 4 months for the summer, 2 bi-monthly periods - about €50 for each bill.

Standing charge of about €15 incl vat and €35 for hot water (no heating used over this period).

So I'm reckoning solar panels might save €147 (€35*6bimonthly bills *70%) per year on that basis at most.

I'll be a long time paying back the €3500 net of grant it's possibly going to cost for a Kingspan 30 tube system with cylinder & installation.

Now we've two toddlers who have little consumption at present but I'm assuming the equation will change as they get older.

Still feel like i'm missing something in terms of it being worthwhile for a lot of people.

Is it that our gas costs to heat water are low as we've a small enough cylinder at present and a brand new 91% efficiency boiler to do it?

I'd say you are more or less spot on there Kennyb3, I would expect that system to make about 1300 Kwh/Annum, I don't know what your gas price is but assuming €0.08/Kwh and a boiler Efficiency of 85% then the energy savings would be, 1300/0.85, 1529 Kwh/Annum which translates to 1529*0.08, €122/Annum. If you use an electric immersion for the summer months then the saving would be, in my opinion, very close to your number, above.
I have 2XFlatPlates and with a combination of oil firing and Immersion heating during the summer months, I reckon I save around €150/Annum. My system gives a pretty consistent solar input to the cylinder of 950/1000 Kwh/Annum.

kennyb3 · 03-10-2014 3:18pm

Thanks - no immersion, we run all hot water off Ideal Logic 15kwh boiler.

Doesn't seem worth it till our two girls are getting towards their teens and using huge amounts of water for showers etc.

josip · 03-10-2014 3:25pm

kennyb3 wrote: »

Thanks - no immersion, we run all hot water off Ideal Logic 15kwh boiler.

Doesn't seem worth it till our two girls are getting towards their teens and using huge amounts of water for showers etc.

Ah, but that changes everything.
In your first post you said 2 toddlers but now we find out they're both girls
In my limited experience, hot water consumption for females is higher than for males and this will halve shorten your payback timeframe.

Are you all pleased with your solar panels for hot water heating

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