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

championc · 02-11-2011 1:15am

I'm no expert - just my 2 pence worth.

Watch your roof and see what time the sun hits the roof in the morning and what time it loses it later in the day. However, given the fact that the air temp is lower in the mornings, it would not quite be as efficient as a SW facing roof.

As for sizing, you really need 50 tubes with a 300l store (or I have 30 tubes with 180l). It really heats hot washing water but if oversized on the tubes side, could in theory be used to transfer heat from the store into a rads circuit to take the chill out of a house in late spring or early autumn (via a second coil) - that next on my to do list !!

C

Do-more · 02-11-2011 7:00am

Likewise I am no expert but this link let's you input all the various data for your location, orientation, roof pitch etc. and calculate the output of a solar PV panel.
http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

By running the calculations for due south and for your actual orientation you can see what drop off you have from the ideal. As it's based on calculating the solar radiation I presume it's also reasonably valid for solar thermal.

FWIW my roof is also facing south east and the passive house planning program calculates that 8m2 of tubes will give me 69% of my yearly estimated DHW demand.

quentingargan · 02-11-2011 8:56am

Qualitymark wrote: »

Does the orientation make a huge difference? My roof faces southeast, rather than due south.

Do these systems just heat washing water, or do they heat radiators as well?

What's the ideal size for a standard three-bed semi?

There is a small fall off when you go from S to SE. About 10%, and slightly more than that if the roof is steep. If you have a SE roof with a 30 degree pitch, that is better than a SE roof with a 45 degree pitch.

We have a computer simulator that can give precise figures based on your geographical location, roof orientation and pitch and the type of panel used. PM me if you want that.

Qualitymark · 07-11-2011 10:56pm

Our roof is a standard sort of pitch - it's a typical 1930s semi - but I have no idea what that pitch is. Any tips? If I lean out the skylight and put a spirit level on the roof will it show the percentage pitch?

firemansam4 · 07-11-2011 11:54pm

I really wouldn't worry to much about the pitch of the roof, unless it is at a very shallow or deep pitch it wont make too much difference. As for the roof being not due south, i don't think many roofs are, so there would be a loss of efficiency but what we would have recommended as installers would have been to just add a few extra tubes to compensate if you are using vacum tubes that is.

Qualitymark · 08-11-2011 12:17am

I'm just wondering what figure to put in that calculator, though.

Qualitymark · 08-11-2011 1:08am

Do-more wrote: »

this link let's you input all the various data for your location, orientation, roof pitch etc. and calculate the output of a solar PV panel.
http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

Unfortunately it's designed for people from another planet than mine. Azimuth? Installed peak PC power? Tracking options? They might as well be speaking Greek.

Do-more · 08-11-2011 9:06am

Qualitymark wrote: »

Unfortunately it's designed for people from another planet than mine. Azimuth? Installed peak PC power? Tracking options? They might as well be speaking Greek.

Firstly as it may not have been obvious, the calculator in the link calculates the amount of electricity generated by a solar photo voltaic panel.

It will not calculate the amount of hot water you will get from a solar thermal panel.

The idea was more that you could see for yourself how much a panel mounted on your roof would produce compared to the ideal south facing orientation.

The Azimuth is the direction in which your roof is facing, so if it is facing directly south you put in 0 and if it is facing due East you put in -90.

So you only need to pick your location off the map and put in a value for the pitch of the roof and for the azimuth and all other values you can leave at the default.

The idea was only to demonstrate to you that it is not the end of the world if you don't have a roof facing due south.

For example my own roof is facing approx. south east (-43) and is at 45 degrees pitch but I lose only 5.2% compared to the optimum for my location which is facing due south with a 37 degree pitch.

Qualitymark · 08-11-2011 9:19am

@championc What is this 'coil' of which you speak?

Coles · 08-11-2011 12:47pm

Qualitymark wrote: »

@championc What is this 'coil' of which you speak?

Heating systems (solar, peat pumps, central heating boilers etc) transfer their heat in an 'indirect' way. Basically the warm water in the boiler (or glycol mix in the solar panels) doesn't mix with the water in the cylinder, but rather flows through a section within the cylinder (the 'coil') where the heat is transferred to the water.

Read up on 'indirect cylinders'.

championc · 08-11-2011 8:46pm

to continue

A pipe enters your cylinder and goes around and around in the shape of a spring and then exits the cylinder. If the liquid is hotter than the water inside the cylinder, and is travelling slowly enough, it will transfer the heat from the coil into the cylinder water.

images?q=tbn:ANd9GcRXaxDqTi4pS-E-rZ_kdQyMggsJBAkODV762c7FYAFSe3JcHw67DQ

images?q=tbn:ANd9GcRXaxDqTi4pS-E-rZ_kdQyMggsJBAkODV762c7FYAFSe3JcHw67DQ

I personally am trying to see if it's worth my while for this transfer to happen in the opposite direction - transferring surplus heat from the cylinder back into the radiator circuit. It's a larger scale version of heat dumping.

Anybody done this ?

C

Coles · 08-11-2011 10:26pm

championc wrote: »

I personally am trying to see if it's worth my while for this transfer to happen in the opposite direction - transferring surplus heat from the cylinder back into the radiator circuit. It's a larger scale version of heat dumping.

Anybody done this ?

C

One interesting way to deal with surplus summer/autumn heat would be to incorporate a seasonal thermal store, - basically an extremely well insulated and large thermal mass. Might be difficult to incorporate into an existing house, but if might work in some scenarios.

Wikipedia link to 'Seasonal Thermal Stores'.

ccsolar · 08-11-2011 10:52pm

Coles wrote: »

championc wrote: »

I personally am trying to see if it's worth my while for this transfer to happen in the opposite direction - transferring surplus heat from the cylinder back into the radiator circuit. It's a larger scale version of heat dumping.

Anybody done this ?

C

Hi Champion
We fit this type regularly in existing houses when there is a circulating pump near the hot water cylinder.
It works well in summer as a heat dump but you will need a special controller or a pipe stat to set it up.
Cc

firemansam4 · 08-11-2011 10:58pm

championc wrote: »

I personally am trying to see if it's worth my while for this transfer to happen in the opposite direction - transferring surplus heat from the cylinder back into the radiator circuit. It's a larger scale version of heat dumping.

Anybody done this ?

C

In one system we were working on in the past I seen this happen by accident,
What happened was in mid summer the cylinder got to very high temperatures of around 90 degrees c, The solid fuel stat was probably located a little too close to the cylinder and the temperature traveled down the solid fuel pipe off the solid fuel coil in the cylinder, it then knocked off the solid fuel pump and took a good bit of heat out of the cylinder to the radiators, but they would of went just luke warm and reduced the temperature of the cylinder from 90 c to about 55 c. It was a 300 l cylinder.

but even without this if lets say this time of year you start putting on your heating and it has been a very sunny day outside, it is possible that your cylinder can be up at 80 or 90 degrees and the heating system could be running at 70 degrees so what happens is opposite transfer through the heating coil only a small bit albeit

championc · 09-11-2011 7:31pm

firemansam4 wrote: »

but even without this if lets say this time of year you start putting on your heating and it has been a very sunny day outside, it is possible that your cylinder can be up at 80 or 90 degrees and the heating system could be running at 70 degrees so what happens is opposite transfer through the heating coil only a small bit albeit

I know this is a very vague question but hopefully someone can give me a less vague answer - If my store was at 75 and I turned on my rads pump (without the boiler) to allow for the store heat to transfer into the rads circuit, how long would you expect before I would begin to feel some heat from rads - 10 mins, an hour ........

My thought would be to put a temperature controlled valve in place to basically allow the store to dump heat once the store temp was over 55 deg.

Or maybe a simpler proposition, In a typical setup that has a rad as a heat dump, how quickly does a rad like this heat up and how long would a store at 75 take to be reduced down to 55 (basically allowing for the use of the store hot water that night or the next morning)

C

firemansam4 · 09-11-2011 11:38pm

championc wrote: »

I know this is a very vague question but hopefully someone can give me a less vague answer - If my store was at 75 and I turned on my rads pump (without the boiler) to allow for the store heat to transfer into the rads circuit, how long would you expect before I would begin to feel some heat from rads - 10 mins, an hour ........

My thought would be to put a temperature controlled valve in place to basically allow the store to dump heat once the store temp was over 55 deg.

Or maybe a simpler proposition, In a typical setup that has a rad as a heat dump, how quickly does a rad like this heat up and how long would a store at 75 take to be reduced down to 55 (basically allowing for the use of the store hot water that night or the next morning)

C

I think in my last example i give which would have been something like what you want to do, it took about 10 to 20 minutes to start feeling the radiators heat, but like i said it was only to a slight luke warm of all the rads, if you were doing this to try heat the house I personally cant see it really doing much, it might be of more use as something that would kick in maybe 20 minutes before the heating comes on, to save a little on the heating fuel costs.
But this is just an opinion - I could very well be wrong, i've never actually tried fitting a solar system to heat radiators, just to heat DHW

gjc · 30-11-2011 12:47pm

Excuse me I am thinking of getting solar panels to heat water only looking at 300l tank evacuated tube system...trying to sift through info .....can I ask what temperature is the water heating up to at this time of year?? Also what is the best way of comparing different products. Any help would be grateful.

Do-more · 30-11-2011 2:08pm

gjc wrote: »

Also what is the best way of comparing different products.

Comparing different solar panels is not a particularly easy task (in my experience at least

).

Decent panels should be certified and appear in the Solar Keymark database. It's easiest if you are comparing two panels which are both certified by the same certification body such as DIN the German certification body.

You will need get the licence number for the panels you are looking for from your supplier, hopefully it will be on their literature or website and then get the test data sheet for that panel from the data base. The licence number will look something like this: 011-7S206 R

You should then be able to compare the performance of the panels under test conditions for a location in Germany.

Whilst the output you get in Ireland won't be the same as for the test location it does at least give you a chance to make a comparison between panels and relating that back to the price you are being quoted for installation you can see which is giving you the most bang for buck.

It's also helpful to look at the stagnation temperature of the panels which is given on the test data sheets the higher the temp. the better.

The whole process is not very user friendly and can be pretty baffling but it's the best I can offer you.

championc · 30-11-2011 5:50pm

For 300l tank I would suggest 50 tubes.

I have 30 and 180l and on a full sunny day at present, I can raise the whole store by about 15 deg C. The highest I've been during November is about 52 deg C (good sunshine 04 - 07 Nov) with the lowest at 15 deg C. I have a combi boiler so I can send pre-heated water to the boiler to then raise it to the required 45 / 46 deg C to deliver to the taps so I am never wasting any heat really - I only heat what I use.

Here's a pic of my data from 22 Nov 2011

ccsolar · 01-12-2011 4:31pm

gjc wrote: »

Excuse me I am thinking of getting solar panels to heat water only looking at 300l tank evacuated tube system...trying to sift through info .....can I ask what temperature is the water heating up to at this time of year?? Also what is the best way of comparing different products. Any help would be grateful.

PM sent
Cc

championc · 03-12-2011 8:23pm

BTW, for anyone who is wondering, Kingspan re-badge Steca controllers

saibhne · 04-12-2011 10:39am

gjc wrote: »

Excuse me I am thinking of getting solar panels to heat water only looking at 300l tank evacuated tube system...trying to sift through info .....can I ask what temperature is the water heating up to at this time of year?? Also what is the best way of comparing different products. Any help would be grateful.

Hi gjc,
I've sent a PM to you about a free design service you can avail of which compares the output of different solar panel systems. Using the details of your particular site you can find out how much energy different systems will produce and figure out the cost/benefit.

Thanks!

S.

gjc · 11-12-2011 4:44pm

Solar panels installed this weekend question one..... is the system a silent system or do people get noise when the pump is running. my system is not noisy but certainly is not silent (small level of noise) when the pump is running is this normal?? Ta

championc · 11-12-2011 10:30pm

While my pump is in the attic, when up there, I can hear it whirling away but it's just a quiet whirling, nothing more

C

Qualitymark · 11-12-2011 10:32pm

championc wrote: »

While my pump is in the attic, when up there, I can hear it whirling away but it's just a quiet whirling, nothing more

C

Does it save you money on water heating even with the electric pump?

firemansam4 · 11-12-2011 11:35pm

gjc wrote: »

Solar panels installed this weekend question one..... is the system a silent system or do people get noise when the pump is running. my system is not noisy but certainly is not silent (small level of noise) when the pump is running is this normal?? Ta

The pumps usually make a small swishing sound but it shouldn't be very loud at all, but sometimes slight air bubbles in the system can make them a lot louder, this will usually settle down after a while but then there are pumps that do seem to make a lot more noise than normal.

Qualitymark wrote: »

Does it save you money on water heating even with the electric pump?

I tried working out the cost of running a pump on the system for a year and by my estimations it worked out less than 20 euros a year. This was taking into account the amount of time they would usually be running on average every day in a year and the power of the pump which is usually set at about 50 watts or less. So from those figures I worked out how many kilowatts was used on an average year and multiplied it by the cost of a KW of electricity.

Qualitymark · 11-12-2011 11:42pm

And firemansam, do you get hot water all year round?

firemansam4 · 12-12-2011 12:38pm

Qualitymark wrote: »

And firemansam, do you get hot water all year round?

well its not going to provide you with 100 percent of your hot water needs in the winter months but most decent systems should provide between 60 - 70 percent of your hot water needs for a year, as well as having a little knock on effect of sometimes helping your heating system get up to heat a bit faster.

Qualitymark · 12-12-2011 1:47pm

Thanks, will put your comment behind my ear in case I ever have the money to do this.

gjc · 12-12-2011 5:51pm

Thanks for that feedback regarding noise of pump, the pump was only giving out a slight whirling noise there was indeed small amount of air in system which we have got rid of now...pump very quiet now...happy!!!

championc · 12-12-2011 10:04pm

Qualitymark wrote: »

Does it save you money on water heating even with the electric pump?

Keep an eye on the big picture. I have been graphing my gas units usage since Jan 06. I have taken the bi-monthly readings, added up a years worth (6 bills) and divided by 365 to get a daily units average.

So I started off in Jan 07 with about 4.8 units per day and rose to over 5.5. in Feb09 when I installed my system. May, Jul and Sep 11 have all stabilized at 4.0. So therefore, based on a running total of 6 bills, I'm down from about 2,000 units per year to about 1,450 and so, with costs per unit increasing, should turn into a pretty saving and well on it's way to paying for itself within 10 years.

Since Feb09, my system has recorded that it has generated over 2400 hours of heat

Qualitymark · 12-12-2011 10:07pm

championc wrote: »

Keep an eye on the big picture. I have been graphing my gas units usage since Jan 06. I have taken the bi-monthly readings, added up a years worth (6 bills) and divided by 365 to get a daily units average.

So I started off in Jan 07 with about 4.8 units per day and rose to over 5.5. in Feb09 when I installed my system. May, Jul and Sep 11 have all stabilized at 4.0. So therefore, based on a running total of 6 bills, I'm down from about 2,000 units per year to about 1,450 and so, with costs per unit increasing, should turn into a pretty saving and well on it's way to paying for itself within 10 years.

Since Feb09, my system has recorded that it has generated over 2400 hours of heat

Wow!

championc · 02-02-2012 12:20am

So by the second anniversary of it's installation, I just missed 2500 hrs by 15

Qualitymark · 02-02-2012 12:36am

Now that the weather is really icy, how are your hot water solar panels performing?

championc · 04-02-2012 12:54am

Here you go, the data from last Wednesday 01 Feb

CJhaughey · 29-03-2012 9:00pm

My 400l tank is sitting at 68deg C after todays sun. Thats top of the tank, the bottom is 42deg.

quentingargan · 29-03-2012 9:19pm

CJhaughey wrote: »

My 400l tank is sitting at 68deg C after todays sun. Thats top of the tank, the bottom is 42deg.

I assume that the sun brought the whole cylinder up to 68, and that you used some hot water, bringing cold water into the bottom of the cylinder and dropping it to 42...

The other way this can come about is that the heating brought the top to 68 and the solar brought it to 42, but, eh, you didn't have the heating on today, surely:)

CJhaughey · 29-03-2012 9:27pm

Yep 2 kids and a dog use a bit of water especially in hot weather like this.
It would have been a lot higher if it wasn't being used all day, I usually change the dishwasher feed over to HW this time of the year as well.
The washing machine has hot and cold feeds so it uses what it need from each.
Best to use it while its there.:)

Mothman · 29-03-2012 9:38pm

CJhaughey wrote: »

Best to use it while its there.:)

The kids were using the hot water on the water slide today & yesterday

It's usually May at the earliest before this is done, though we did it in April last year.
Bottom of 500l store was up to 69C with top at 74C this afternoon.

I think it's 6 days since the stove was on.

I'm delighted

solarstudent · 03-04-2012 1:38pm

championc wrote: »

For 300l tank I would suggest 50 tubes.

I have 30 and 180l and on a full sunny day at present, I can raise the whole store by about 15 deg C. The highest I've been during November is about 52 deg C (good sunshine 04 - 07 Nov) with the lowest at 15 deg C. I have a combi boiler so I can send pre-heated water to the boiler to then raise it to the required 45 / 46 deg C to deliver to the taps so I am never wasting any heat really - I only heat what I use.

Here's a pic of my data from 22 Nov 2011

to suggest you need 50 tubes for a 300l tank is absolutely incorrect I am afraid. if thats what you need then your system has a low efficiency and output, and therefore your installer has installed more tubes to make up for this deficit and at a greater cost to you

quentingargan · 03-04-2012 3:19pm

solarstudent wrote: »

to suggest you need 50 tubes for a 300l tank is absolutely incorrect I am afraid.

I don't think there are any absolutes. There is not a one-size-fits-all dimensioning formula. I personally have a grossly over-sized panel so that I can get most of my hot water needs met in March and October, without having to light a fire to heat our water.

In a poorly insulated house, with the central heating running up to April and again in September, I would suggest a smaller array of panels.

It all depends on what you want.

ccsolar · 03-04-2012 11:11pm

solarstudent wrote: »

to suggest you need 50 tubes for a 300l tank is absolutely incorrect I am afraid. if thats what you need then your system has a low efficiency and output, and therefore your installer has installed more tubes to make up for this deficit and at a greater cost to you

I have to agree with Quintan, their is no one size fits all.
I have a 60 tube system on a 300 litre tank with a large heat dump for the summer months, Anti-scald valve is also a must as the water is normally over the 70 degrees in the tank.
It works very well in the winter especially if it is freezing cold out side, have had temperatuires of 40-50 degrees some days.
Some houses would need to install a 50 tube system inorder to avail of the SEAI grant for solar, this is due mainly to the sqm of the house.
With regards to the low efficiency/output of some panels I have used the SEAI calculator and found that their is on average only 150kwh/y difference between the cheapest panel on the market and the most expensive irish manufactured panels.
On a different note I did try and buy a 40 tube irish manufactured solar panel this week and the supplier told me that there was none in the country, the manufacturer has shipping problems.
Manufactured in Ireland translates to assembled in Ireland.

Cc

firemansam4 · 03-04-2012 11:59pm

I have fitted systems in the past using the exact same manufacturer and used different combinations of tubes to a 300l cylinder, have used higher amount of tubes on some systems mainly due to the fact of the way the old grant system worked meaning the cost was not too much more.
Now one of the systems had 40 tubes and a 300 l cylinder and another had 60 tubes and a 300 l cylinder, i found the performance of the extra tubes was a large benefit and that in more marginal months the 40 tubes just was not sufficient to heat up the cylinder enough.

And the tubes used was of a well known good quality manufacturer and nothing wrong with their output.

championc · 04-04-2012 8:37pm

solarstudent wrote: »

to suggest you need 50 tubes for a 300l tank is absolutely incorrect I am afraid. if thats what you need then your system has a low efficiency and output, and therefore your installer has installed more tubes to make up for this deficit and at a greater cost to you

Care to back this up with some data ?

solarstudent · 04-04-2012 8:49pm

championc wrote: »

Care to back this up with some data ?

yes if you p.m me i can send you some attachments via email and some data sheets if you like. i study renewable energy in C.I.T and have done a good bit of research into this, it is only my opinion and il let you make your own decision as to whether you agree. A lot of manufacturers will have to put up extra tubes to get the output because the efficiency of the panel is poor. If you have a panel suited to Irish climate (i.e designed to collect diffuse radiation mainly) then you will get far better results for less tubes.

solarstudent · 04-04-2012 8:56pm

quentingargan wrote: »

I don't think there are any absolutes. There is not a one-size-fits-all dimensioning formula. I personally have a grossly over-sized panel so that I can get most of my hot water needs met in March and October, without having to light a fire to heat our water.

In a poorly insulated house, with the central heating running up to April and again in September, I would suggest a smaller array of panels.

It all depends on what you want.

What is the point in having an oversized panel? I agree there is no one formula to determine this but you can get pretty close to your required needs by monitoring your demand for hot water, do you want it for domestic use alone or are you going to use it to support central heating, size and heat retention of your cylinder etc. There is not much point in putting up a 50 tube system for 300l cylinder when 30 would easily suffice. And I have seen a 30 tube system be more than adequate for this.

It really depends on the panel. if you buy a quality panel it will deliver better output. i think we both agree that cheap cheerful and chinese is not the (eco)logical way to go and if you want to get the best output for the least tubes you have to buy quality.

firemansam4 · 04-04-2012 9:01pm

solarstudent wrote: »

yes if you p.m me i can send you some attachments via email and some data sheets if you like. i study renewable energy in C.I.T and have done a good bit of research into this, it is only my opinion and il let you make your own decision as to whether you agree. A lot of manufacturers will have to put up extra tubes to get the output because the efficiency of the panel is poor. If you have a panel suited to Irish climate (i.e designed to collect diffuse radiation mainly) then you will get far better results for less tubes.

Well to me there is a big difference in sitting in some class studying data sheets etc to having real on the job experience and customer feedback, and i'm saying that from my previous experience I don't think 50 or even 60 tubes is too many for a 300 liter cylinder in fact quite the contrary.
And like I said before I have never used sub standard tubes, or any sub standard parts for that matter.

And getting far better results for using less tubes well that kind of defies logic really?

solarstudent · 04-04-2012 9:28pm

firemansam4 wrote: »

Well to me there is a big difference in sitting in some class studying data sheets etc to having real on the job experience and customer feedback, and i'm saying that from my previous experience I don't think 50 or even 60 tubes is too many for a 300 liter cylinder in fact quite the contrary.
And like I said before I have never used sub standard tubes, or any sub standard parts for that matter.

And getting far better results for using less tubes well that kind of defies logic really?

Have been on work experience for 6 months at a solar company fitted over 20 different solar thermal installations and been to around 50 different installations.
And we don't just sit in a class looking at data sheets either in college btw.

Ok how about this. In Ireland we receive 60/70% diffuse radiation..ie the majority of our sunlight. If you have a panel which is designed to collect the diffuse radiation(of which there are very few in Ireland) then it will produce far greater output.
Even the worst of the worst panel will have a great output on a sunny summers day, its in mid winter that the difference in panel will count when there is cloudy weather.

So therefore if you have panels designed to collect the diffuse radiation and producing a far higher kW output in this climate..then it makes sense that you will need less tubes than you would with just your regular system which produces less kW output.
I hope this is logical for you

Also I apologise you may not have used sub standard tubes or fittings and i wasn't implying you did..but there are a lot of them out there.

firemansam4 · 04-04-2012 9:41pm

solarstudent wrote: »

Have been on work experience for 6 months at a solar company fitted over 20 different solar thermal installations and been to around 50 different installations.
And we don't just sit in a class looking at data sheets either in college btw.

Ok how about this. In Ireland we receive 60/70% diffuse radiation..ie the majority of our sunlight. If you have a panel which is designed to collect the diffuse radiation(of which there are very few in Ireland) then it will produce far greater output.
Even the worst of the worst panel will have a great output on a sunny summers day, its in mid winter that the difference in panel will count when there is cloudy weather.

So therefore if you have panels designed to collect the diffuse radiation and producing a far higher kW output in this climate..then it makes sense that you will need less tubes than you would with just your regular system which produces less kW output.
I hope this is logical for you

Also I apologise you may not have used sub standard tubes or fittings and i wasn't implying you did..but there are a lot of them out there.

Ok sorry i thought you were saying that sometimes you get better results by using less tubes.

Well all I can say is that the equipment we were using to my knowledge was of good quality and offered one of the best output ratings you could get, this was not my own company by the way but another that I worked for, and from all accounts we found that adding the extra tubes in a lot of cases really helped boost the systems efficiency in marginal conditions and like i said from a previous post it was going by feedback received from various different jobs using different amount of tubes on different systems.

freddyuk · 04-04-2012 10:26pm

solarstudent wrote: »

Have been on work experience for 6 months at a solar company fitted over 20 different solar thermal installations and been to around 50 different installations.
And we don't just sit in a class looking at data sheets either in college btw.

Ok how about this. In Ireland we receive 60/70% diffuse radiation..ie the majority of our sunlight. If you have a panel which is designed to collect the diffuse radiation(of which there are very few in Ireland) then it will produce far greater output.
Even the worst of the worst panel will have a great output on a sunny summers day, its in mid winter that the difference in panel will count when there is cloudy weather.

So therefore if you have panels designed to collect the diffuse radiation and producing a far higher kW output in this climate..then it makes sense that you will need less tubes than you would with just your regular system which produces less kW output.
I hope this is logical for you

Also I apologise you may not have used sub standard tubes or fittings and i wasn't implying you did..but there are a lot of them out there.

Can you explain the difference between the super efficient tubes that will allow you to use that many fewer tubes for the same output? Is it a different technology or a better put together heat transfer tube that transfer higher heat output into the transfer fluid from the same insolation. Is there a difference in flow rate?
Thanks

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

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