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

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

solarstudent · 04-04-2012 10:36pm

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[/Quote]

No problem pm me your email address and I will attach you some college work and Info on the systems I have

championc · 04-04-2012 11:18pm

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.

How many of these installations fitted a data logger ?

Many customers may turn around and say how delighted they are with the results and we all know that you cannot believe data sheets. Data sheets are based on the "perfect" conditions.

Let me share the following with you. A neighbour of mine had a panel. He confirmed that he was delighted with his system because his water temp never fell below 56 or so deg. First alarm bell began to ring. He then confirmed that he didn't feel that he's saved a huge amount on his gas bill so far.

Basically, he had the central heating connected to a second coil and so it was likely that the CH was doing a fair amount of heating the stored water !!

rosepaddy · 10-04-2012 9:22am

tred wrote: »

Just thinking of starting a poll on this. Is everyone here happy or not with their solar panels, performing as expected?

good question, poll is a very good idea, we use solar to support our central heating using a diffused radiation collector from switzerland only one in ireland, i think there is alot of misinformation alot of people think if they buy more tube they get more heat not true , if people dont understand what the capabilities of solar are and they have nothing to compare there system to then it is possible they ae happy with their system, even though it may be providing little support campared to a better system,

the answer to your question on the poll very happy with solar here in Ireland, even happier that i use it well towards my central heating

steviebg · 10-04-2012 10:21am

Hey all,
I am really thinking about getting in solar but don't have a clue about what to get. From reading on here there seems to be some systems better suited for use in ireland is this true? If so is there a list of the best systems to use. Also i'm in the cork area if anybody could recommend an installer they've used that would be great! Thanks all.

championc · 10-04-2012 10:26pm

rosepaddy wrote: »

good question, poll is a very good idea, we use solar to support our central heating using a diffused radiation collector from switzerland only one in ireland, i think there is alot of misinformation alot of people think if they buy more tube they get more heat not true , if people dont understand what the capabilities of solar are and they have nothing to compare there system to then it is possible they ae happy with their system, even though it may be providing little support campared to a better system,

the answer to your question on the poll very happy with solar here in Ireland, even happier that i use it well towards my central heating

I'm happy with my system but it is good, is it working efficiently, is it working as it should - I haven't a clue.

Not sure how you support central heating though, given that I assume you have plentiful hot water stored during the summer - a time when I would assume you would have little use of CH. So are you "topping up" your store in some way other than via solar ? And what minimum temperature water do you use towards your CH ?

IMO polls are a waste of time unless you have some way of actually quantifying results and everyones system would need to be based on the same factor. In other words, I have 30 tubes with Aperature Area of 3.24m2 for 180 Litres store. So this would equate to 55.5l / per m2. My system raises the water temp by 4 deg C every 50 minutes.

So to start you all off, based on the current weather

1m2 Tubes takes 12mins to raise 55.5litres by 1degC

quentingargan · 10-04-2012 10:41pm

championc wrote: »

IMO polls are a waste of time unless you have some way of actually quantifying results and everyones system would need to be based on the same factor.

I also think polls are likely to be misleading if those of us who work in the industry also take part. I'm hardly going to say that I'm unhappy with my system now, am I?:rolleyes:

solarstudent · 13-04-2012 2:25pm

championc wrote: »

So to start you all off, based on the current weather

1m2 Tubes takes 12mins to raise 55.5litres by 1degC

There are so many variables to that calculation that you cannot use it as a comparison really. It all depends on the irradiation available to the collector and how much of that it can transfer to your cylinder, and therefore the less work your boiler has to do if it has to do any at all.

hop2it · 14-04-2012 11:04pm

I must say i,m very happy with my solar tubes
I have 40 tubes 58mm by 1800 mm and a 300 litre tank
adverage bottom tank temp of 55c d'ont know if thats good or bad but i'm happy

championc · 15-04-2012 12:14am

solarstudent wrote: »

There are so many variables to that calculation that you cannot use it as a comparison really. It all depends on the irradiation available to the collector and how much of that it can transfer to your cylinder, and therefore the less work your boiler has to do if it has to do any at all.

Agreed, but the point here is, can anyone do better ? We can all "say" we are happy but you have to know what it potentially possible to have any idea if your system is working at optimum or is crap.

hop2it wrote: »

I must say i,m very happy with my solar tubes
I have 40 tubes 58mm by 1800 mm and a 300 litre tank
adverage bottom tank temp of 55c d'ont know if thats good or bad but i'm happy

Is this purely heated from the tubes or is it supported by CH ? It demonstrate better to the solarstudent, if supported by the CH, then it could be argued / questioned as to how effective the tubes indeed are.

ADVICE TO EVERYONE THINKING ABOUT AN INSTALLATION
Ensure you get a data logger option with your controller. For the sake of another hundred or two, you'll have a full insight as to what your system is doing and how well it's performing. You can never beat hard data

hop2it · 15-04-2012 12:25am

Is this purely heated from the tubes or is it supported by CH ? It demonstrate better to the solarstudent, if supported by the CH, then it could be argued / questioned as to how effective the tubes indeed are.

sun light only

championc · 17-04-2012 9:54am

hop2it wrote: »

sun light only

That's pretty impressive for the bottom of the tank since I would have expected new water to be entering the bottom from the rising main and therefore, it would be in the low to mid teens

Even for the top of the tank, it could be said that AVERAGING at this level at this time of year is pretty impressive for 40 tubes on 300 l. How many deg of an increase would you get on an average sunny day - maybe a day like today.

C

freddyuk · 17-04-2012 6:03pm

I would suggest the bottom sensor is actually in the area of the incoming solar coil so 55c would be about right. The really useful water is at the top and needs to be getting to 70c+ with a TMV installed to make best use of the solar energy. Is there a top sensor?

hop2it · 17-04-2012 7:16pm

@ championc

as i type this the bottom tank is 53c
we usually bath and shower at bed time so morning temp is usually in the teen,s
so a 40 degree rise even on a day like today

championc · 17-04-2012 7:45pm

As Freddyuk asked, do you have a top sensor ?

However, you've really proved my point on here. I was happy with my system performance but now I'm not so sure. Here's my data for today.

hop2it · 17-04-2012 10:31pm

no top sensor fitted yet
what's a tmv ?

freddyuk · 17-04-2012 11:04pm

May be worth getting a top sensor (about €15) as this is where you draw your hot water from. Surprised you did not get 3 sensors installed. Unless you have issues with stratification the tank should be several degrees hotter at the top of the tank. Your measurement is taken from 2/3 down where the solar coil is heating the water but this is not the water you are using. 300 litres with 40 tubes is a tall order at this time of year so it is important to know the temperature at the top. If you have the best part of 200 litres at 55c+ using 40 tubes alone then you are doing very well but if you have a boiler system feeding in at the top then this would explain it! But you say you use the water at night (not ideal) and it is cold in the morning which suggests the boiler is not heating the cylinder. Is the boiler programmed to come on? What is the panel temperature during the day when the sun is out?
A TMV is a thermostatic mixer valve to cool down the hot water to prevent scalding risk from a solar system which is allowed to get as hot as possible. Essential kit!

freddyuk · 17-04-2012 11:16pm

championc wrote: »

As Freddyuk asked, do you have a top sensor ?

However, you've really proved my point on here. I was happy with my system performance but now I'm not so sure. Here's my data for today.

Looks OK ? You are getting 70c on the panel and up to 55c in the cylinder. Depending on where your lower sensor is installed will dictate the differential top/bottom temperature.You should have sufficient hot water - maybe 120 litres for the morning showers ?

championc · 18-04-2012 12:45am

freddyuk wrote: »

Looks OK ? You are getting 70c on the panel and up to 55c in the cylinder. Depending on where your lower sensor is installed will dictate the differential top/bottom temperature.You should have sufficient hot water - maybe 120 litres for the morning showers ?

Bottom sensor right at the bottom of the 180l tank and top sensor right at the top.

I'm getting part of my system changed tomorrow. The tank has twin coils. I am getting the tubes linked to the upper coil and with a diverter valve fitted. In this way, I can heat 90l up to maybe 55 deg C and then, once reached, the diverter valve will switch the heat to begin heating from the bottom. My hope is to maximize my heat gain in Spring and Autumn.

I have a combi solar mixing valve which will send water when 45 deg or over (the Valve incorporates an anti-scald mixer), straight to the taps or else, it cools it to 28 (if between 45 and 28) and sends it to my combi for heating up to 45 deg. The combi can only take input of 28 deg or less. So I want as much hot water to go straight to the taps as often as possible.

New setup - using the upper coil to heat the top half first

freddyuk · 18-04-2012 9:15am

Ah the joys of a good old Firebird! Just needs to top up any temperature of stored water.
I can't see why your system will not work if the combi valve works effectively. Do you have a heat dump system also?

championc · 18-04-2012 3:29pm

During Feb and March, I struggled to reach 40 deg. However, if I was only heating half the water on these occasions then I'd have a greater chance of water exceeding 45 deg after even half a days sunshine.

No heat dump necessary, my system is a Kingspan which autovents. I have the max temp set to 90 deg so it's only one or maybe two days per year that it will ever get up to this. You would need about 3 days of perfect sunshine in a row to hit this

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

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