Solar panels - advice on siting away from house?

ofthesorrows

Hi

I don't really want to go into the pros and cons of solar panels here, suffice to say we've decided to go for them to heat DHW but have a few questions if anyone has any advice:

Firstly any recommendations on brands? Have read that German/Austrian made ones are best, and to avoid Chinese manufactured ones. Am looking at the flat plate ones rather than tubes as among other things there are a lot of flying leaves around in Autumn!

Secondly we have an E/W pitched roof on our house but a south facing garage roof about 8m from the house, so were thinking of using it to mount the panels. Anyone have any experience of installing the system external to the house like this? The garage is a new build so we can provide space for the tank etc in it no bother. We're thinking of going for a large tank (600+l) to maximise efficiency and thinking of using a pressurised system to deliver water to the whole house.

Any help would be appreciated greatly!

PeteHeat

Hi,

You have options available to you however I think it best to have a proper survey carried out as a solar system should be designed to meet your hot water requirements.

This includes the size and type of cylinder, very well insulated delivery pipes as you don't want to lose the heat between the garage and the house and the correct quantity and quality of panels.

As the store / cylinder will be in the garage prevention of heat loss is very important, after deciding on the capacity you may need to look at a highly insulated plant room.

It reads very expensive but can be achieved at a reasonable cost because partition walls and a ceiling with proper insulation may suit.

quentingargan

ofthesorrows wrote: »

Hi

We have an E/W pitched roof on our house but a south facing garage roof about 8m from the house, so were thinking of using it to mount the panels. Anyone have any experience of installing the system external to the house like this? The garage is a new build so we can provide space for the tank etc in it no bother. We're thinking of going for a large tank (600+l) to maximise efficiency and thinking of using a pressurised system to deliver water to the whole house.

Any help would be appreciated greatly!

Your losses on an east-west roof may be less than the losses on having a remote cylinder. Personally I would prefer to keep it simple and put extra panels on the roof to compensate for the orientation. An extra panel may be a lot cheaper than all the fuss of having a remote cylinder and will work a lot better.

You can fit the cylinder remotely, but every time you run the hot tap, you will lose the heat in the pipe, and you will have to wait longer for your hot water, as well as wasting water which may be an issue. For this reason, I would recommend using two separate lines - a 1/2" pipe feeding sinks and a separate 3/4" pipe feeding baths. That way, running the tap for a few minutes for the sink won't waste as much heat. Some people use a pre-heat cylinder in the shed and a separate cylinder in the house, but I always find this a bit complicated. Your waste heat will depend on the frequency with which you use small amounts of water. If this is excessive, you might go down to a smaller pipe and pump for your sinks. As Peteheat says, you should make sure the underground pipe is very well insulated.

ofthesorrows wrote: »

Hi

Any recommendations on brands? Have read that German/Austrian made ones are best, and to avoid Chinese manufactured ones. Am looking at the flat plate ones rather than tubes as among other things there are a lot of flying leaves around in Autumn!

I sell both Austrian flatplates and Chinese vacuum flasks. There are over 2,000 factories in China making panels and you can't tar them all with the one brush. The vacuum flask system was developed in China and they have a lot of expertise - in fact many so-called European panels use Chinese flasks. You can ask your supplier to specify 316 marine grade stainless or aluminium frames if you are concerned about tarnish. All vacuum systems will have a life of about 20 years and at that stage, the Chinese flasks will be a lot cheaper to replace than EU made vacuum tubes. Performance for both is similar, but you can check this out by asking for the EN12975 cert from the supplier with the data from an independent lab.

I won't advertise brands here, but you can PM me. You need to decide first whether you want flatplates or tubes. They both have +s and-s. If you have flying leaves, I would avoid vacuum tubes that rely on a reflector. However, tubes without a reflector, besides having a much lower wind load, also keep themselves clean, even in autumn leaves.

Q

Cuauhtemoc

I'd be looking at a similar setup to this.
Boiler in the garage - probably about 8 meters or so from house as well.
Boiler will be heating a 500L buffer tank in garage/boiler house which would in turn supply a dhw tank and ufh in the house.
Was also hoping for about four/five solar panels to contribute to the buffer tank in garage.

Is it all that much more complicated to have the second tank in the house? I don't really have an alternative setup to this.

Thanks,
C.

Cuauhtemoc

Cuauhtemoc wrote: »

I'd be looking at a similar setup to this.
Boiler in the garage - probably about 8 meters or so from house as well.
Boiler will be heating a 500L buffer tank in garage/boiler house which would in turn supply a dhw tank and ufh in the house.
Was also hoping for about four/five solar panels to contribute to the buffer tank in garage.

Is it all that much more complicated to have the second tank in the house? I don't really have an alternative setup to this.

Thanks,
C.

I have built a system similar to what you have desceibed.

The way my system works is a follows, (tá bron orm is olc mé)

The main tank is in the house and the flow is from the garage direct from the boiler, the return pipe from the house tank first passes via a coil in the top of the 1000litre solar buffer tank then it goes through the boiler.

I have also set up an automatic bypass pump that switches in if the outpuout of the buffer tank is above 60C.

Hope this is usefut top you!

PeteHeat

Hi C,

We have installed a system similar to yours, the main difference was the heating is for rads instead of UFH.

I think you should get better value out of the solar as the flow temperature for the UFH is much lower than the flow for rads.

.

quentingargan

Cuauhtemoc wrote: »

I'd be looking at a similar setup to this.
Is it all that much more complicated to have the second tank in the house? I don't really have an alternative setup to this.

Thanks,
C.

That isn't too complicated, and works better than having the solar panels a long way from the cylinder.

Your buffer tank will also help with dumping surplus heat, though in a well insulated house I reckon that the contribution of solar panels to space heating is pretty negligible.

However, take a close look at the length of pipe runs. Your buffer tank might be closer to the kitchen tap than the cylinder in the house. This is the hot tap that you switch on and off most often. Depending on the location of kitchen and bathroom, you might want to dispense with that second cylinder? But you possibly have looked at this option already. Q

De_man

quentingargan wrote: »

running the tap for a few minutes for the sink won't waste as much heat.
........ As Peteheat says, you should make sure the underground pipe is very well insulated.

i have this setup....use a secondary return on the hot water line with the pump set up on a timer to be on a peak times therefore reducing the time lag until you get the hot water....that canadian guy mike holmes had an idea
set up PIRs in your shower rooms & ensuites, when you go into shower room the hot water pump in your plant room is activated automatically by the PIR (great idea)

i haven't got around to sorting that prob out fully yet...

Peter is right....i used a "Zero Loss" pipe from the garage to house
cost me 970euro :eek: might be a better to use lengths of wavin with a couple of cans of expanding foam?

quentingargan

De_man wrote: »

i have this setup....use a secondary return on the hot water line with the pump set up on a timer to be on a peak times therefore reducing the time lag until you get the hot water....that canadian guy mike holmes had an idea
set up PIRs in your shower rooms & ensuites, when you go into shower room the hot water pump in your plant room is activated automatically by the PIR (great idea)

i haven't got around to sorting that prob out fully yet...

Peter is right....i used a "Zero Loss" pipe from the garage to house
cost me 970euro :eek: might be a better to use lengths of wavin with a couple of cans of expanding foam?

Secondary returns cause an awful lot of heat loss. No matter what way you work it, you lose twice the heat (flow and return) and lose all that for a lot more time as well in most cases.

If you are worried about having to wait a 10 seconds or so for hot water to come to the tap, better to have an auxilliary cylinder in the house, or maybe narrower pipe and a pressurised pump. Q

De_man

quentingargan wrote: »

Secondary returns cause an awful lot of heat loss. No matter what way you work it, you lose twice the heat (flow and return) and lose all that for a lot more time as well in most cases.

If you are worried about having to wait a 10 seconds or so for hot water to come to the tap, better to have an auxilliary cylinder in the house, or maybe narrower pipe and a pressurised pump. Q

agreed there, in my case the garage/plant room is situated a good bit from the house and since i'm in a water conservation area;) it's really a trade off heat v water, i had to take the required steps to reduce the water wastage....

yep i've the whole system pressurised..ideally this equipment would be placed in the house & not in the garage....i suppose looking back on it now i should have reduced 4 panels i have to three, then i could have put them on the roof of the house...and had everything in the house and saved myself an absolute fortune

regarding the auxilliary cylinder in the house, i could install one quite easily but i can't see any huge advantages.....if you have a moment you might go through this

thanks

quentingargan

De_man wrote: »

regarding the auxilliary cylinder in the house, i could install one quite easily but i can't see any huge advantages.....if you have a moment you might go through this

thanks

I haven't done this myself, but I have seen systems where a pre-heat cylinder was put in the shed close to the panel. A second differential thermostat then circulated water from this cylinder to one in the house some distance away.

The advantage is that you can keep the panel working at optimum temperature by regularly circulating water from it to the pre-heat cylinder (particularly useful for flatplates). The longer pipe run is only heated occasionally when running water from one cylinder to the other.

I wouldn't dream of retrofitting a system like this, but it could be used as an alternative and would be a lot more efficient than using a secondary return system if you want to save water waste.

De_man

Thanks Quentin, that makes sense, retrofitting wouldn't be a huge job in my case (a mornings work) & i thought i had all avenues covered:)

Overall, the panels are doing exceptionally well, we spend very little for all our hot water & home heating needs when compared to neighbouring properties.

Now, if only i could get a "cheap" wind turbine i'd be sorted;) :D:D

tks again

quentingargan

De_man wrote: »

Now, if only i could get a "cheap" wind turbine i'd be sorted;) :D:D

tks again

As it happens, I am developing a turbine for the Irish market at present:rolleyes:. PM me if you want more on that.

Of course, how cheap is cheap? See here for what happens when you cut the budget too fine (taken from another post on this site)... Q

Evergreen

ofthesorrows wrote: »

we have an E/W pitched roof on our house but a south facing garage roof about 8m from the house, so were thinking of using it to mount the panels

Quentin makes a lot of good points in relation to heat loss from having the tank in the garage. An East west system with two panels on each roof and an East-West controller would be a good option. With a system like this the controller will take heat from one side or both sides of the roof once the panels reach a certain temperature.

We have worked on quite a few similar instalaltions and the biggest problem you will find is that during the Summer they will provide way too much heat and you will probably need to setup a heat dump.

quentingargan wrote: »

Chinese flasks will be a lot cheaper to replace than EU made vacuum tubes. Q

I disagree with this statement, we have used German made U-tube evacuated tubes panels for years and a replacement flask is only EUR 50.00, I have been quoted on occasions EUR 90.00 to replace chineese made heat pipe flasks. I imagine the reason for the difference in cost is that a U-tube system only needs to have the glass part replaced, whereas a heat pipe system has the copper pipe and fluid built into it.

quentingargan

Evergreen wrote: »

I disagree with this statement, we have used German made U-tube evacuated tubes panels for years and a replacement flask is only EUR 50.00, I have been quoted on occasions EUR 90.00 to replace chineese made heat pipe flasks. I imagine the reason for the difference in cost is that a U-tube system only needs to have the glass part replaced, whereas a heat pipe system has the copper pipe and fluid built into it.

If you've been charged €90, you were robbed!:eek:

We sell replacement vacuum flasks for €6 each. These flasks are all interchangeable coming in sizes 47mmX1500, 58mmX1800 etc., and there are hundreds of factories producing these so the flasks are pretty much a commodity, regardless of whether they are for U tube or heat pipe. There is a small difference in the coatings used, the more expensive ones having a copper layer which you can see from inside the flask.

Many European factories actually buy the flask part from China and put them into their own manifolds. Yet others buy the whole lot from China and rebadge it. Nothing wrong with that, I'm typing this on a Japanese branded Chinese made laptop... But €90 for a flask that we can profitably sell for €6? No wonder there are so few houses with solar panels in Ireland!

Where the heat pipe is welded into the tube as a combined unit, the replacements are expensive. This is quite different to flasks where they glass component is separate, and often you are obliged to buy these from the original manufacturer only. Bad idea....

Evergreen

EUR 6.00 ??

I'll give you a call next time I need a replacement

PeteHeat

Hi Evergreen,

I expect the price you paid is for both the tube and the heat pipe ?

That would make sense (kind of) because at €6.00 for the complete kit it makes the Chinese manifold on its own very expensive, example 20 tubes @ €6 = €120.00.

There are some very good Chinese systems on the market and as Quentin pointed out quite a lot are re-badged in Europe, but the quality is down to the importer / agent.

I was asked to install a Chinese system inported and supplied by a hardware store, the same manufacturer has a system with the Solar Keymark and SEI approval.

The big difference that caught my attention was the product code was wrong, appears that the importer brought in a container of the cheapest product made by the factory.

The fact that the importer / retailer didn't know the difference is alarming enough but the factory knowingly sold the inferior product into Ireland having gone through the SEI registration process making a joke of the whole industry.

The above is not good for the consumer who is buying the system expecting the same quality or the Solar industry in Ireland not to mention the better quality Chinese products.

There is a process for buying OEM, (AKA re-badging products) which has a paper trail that is easy enough to follow so nobody is buying a product they think is made in Europe but is actually made in China.

Sad to say its still a case of Caveat Emptor.

.

Fergus Wheatley

The most important aspect of the solar panel installation is the cylinder and the pipework insulation. Poor insulation and your very good panel only performs in good weather. Probably the cheapest way for you to proceed is to mount the panel on the West side of your roof and not to use the East side.

Roof Pitch Due East 75° East 60° East 40° East 20° East Due South 20° West 40° West 60° West 75° West Due West
30° 1620 1734 1824 1924 1995 2022 2008 1948 1865 1780 1679
60° 1372 1523 1664 1829 1939 1986 1968 1889 1743 1614 1467
75° 1202 1352 1495 1665 1786 1838 1823 1729 1584 1454 1312




The fact that the garage is 8 meters away, means that the additional pipe run will be 30 meters of more. Allied Solar has some training notes on-line, and the is an example here on pipe heat losses that matches up with your Scenario.

Example to calculate heat lost in pipework overnight. This ignores the cooling losses when the panel is running. I reckon you'll lose at least 10% putting it on the garage. More in the winter.

A solar panel is installed with a total of 30 meters of pipework (15m flow and 15m return). Calculate the volume of heat transfer fluid contained in the pipework. Calculate for 10mm, 15mm and 22mm.

Secondly, if the pipework cools from 50°C to 20°C at night, calculate the energy lost each night the solar panel is running.

Thirdly, assume that the solar panel runs 300 days per year and produces 2000kWh. What is the percentage efficiency drop caused by the volume of liquid in the pipework cooling. Calculate for 10mm, 15mm and 22mm.

Water in pipework cools by 30°C

Energy in kWhrs = Volume (V) x Change in Temp (Δt) x 0.001166

(This figure means 1000Joules every second for 1 hour, i.e. 3600 seconds)

10mm pipe = 30 x 1.65 x 0.001166= 0.0577 kWhrs per day
15mm pipe = 30 x 4.35 x 0.001166 = 0.1521 kWhrs per day
22mm pipe = 30 x 9.60 x 0.001166 = 0.3358 kWhrs per day

If the panel runs for 300 days per year and creates 2000 kWhrs of energy, then

for
10mm pipe: 0.0577 kWhrs per day x 300 = 17.31 kWhrs
15mm pipe: 0.1521 kWhrs per day x 300 = 45.63 kWhrs
22mm pipe: 0.3358 kWhrs per day x 300 = 100.74 kWhrs


This equates to an efficiency drop as follows
17.31 x 100% = 0.87% (10mm pipe)
2000


45.63 x 100% = 2.28% (15mm pipe)
2000


100.74 x 100% = 5.03% (22mm pipe)
2000

Evergreen

PeteHeat wrote: »

Hi Evergreen,

I expect the price you paid is for both the tube and the heat pipe ?

That would make sense (kind of) because at €6.00 for the complete kit it makes the Chinese manifold on its own very expensive, example 20 tubes @ €6 = €120.00.

There are some very good Chinese systems on the market and as Quentin pointed out quite a lot are re-badged in Europe, but the quality is down to the importer / agent..

Hi PeteHeat,

After hearing the prices from Quentin I was feeling a little hard done by so I went back to check out my facts.

We pay EUR 21 for a 58mm 1500m twin layer tube with selective sputtering on the inside layer. The tubes are manufactured in China for the German manufacturer that we deal with and came with a 10 year operational warranty.

The EUR 90.00 price that I was given was during a meeting with a large distributor in Dublin that we were trying to get to switch over to a brand of panel we distribute. During this meeting he told me that replacement tubes for the collector he currently sells (hint - made in Belfast) cost EUR 90.00 a pop.

quentingargan

Evergreen wrote: »

Hi PeteHeat,

After hearing the prices from Quentin I was feeling a little hard done by so I went back to check out my facts.

We pay EUR 21 for a 58mm 1500m twin layer tube with selective sputtering on the inside layer. The tubes are manufactured in China for the German manufacturer that we deal with and came with a 10 year operational warranty.

The EUR 90.00 price that I was given was during a meeting with a large distributor in Dublin that we were trying to get to switch over to a brand of panel we distribute. During this meeting he told me that replacement tubes for the collector he currently sells (hint - made in Belfast) cost EUR 90.00 a pop.

Yep - that all stacks. I try to distinguish between flasks which are like thermos flasks - two layers of glass with a vacuum in between, and tubes which are a single layer of glass with the heatpipe (or sometimes a U tube or a direct flow pipe-in-pipe) welded in - the whole area inside the tube, including the heat pipe are all in a vacuum.

The problem as I see it with tubes are that you have a far more expensive replacement, and you are relying on a weld or bond between copper and glass to hold in the vacuum. Two materials with different coefficients of expansion getting up to very high temperatures seems like the poorer design, and in some cases where the panel was regularly allowed to stagnate, I have heard of this system failing.

There are tubes made in China, but most distributors prefer to import the flasks. The ones I referred to with the selective coating for €6 are the same spec but a slightly different size (47mm*1.5m). You should be able to get 58mm ones for a lot less than €20 - that would come to €400 for a twenty tubes, not leaving much change for the manifold and u-tubes or heat pipe etc.

The point is that the benefit of flasks is that you aren't stitched into one supplier - there are literally hundreds of factories in China working to a very similar spec. So if you or I go bust, our customers can get them elsewhere. There are only a few standard sizes and the flasks are interchangeable between all of them.

If you buy them in quantities of 40 to 60, you should be able to get these for about €5 each.:)

Evergreen

quentingargan wrote: »

The ones I referred to with the selective coating for €6 are the same spec but a slightly different size (47mm*1.5m). You should be able to get 58mm ones for a lot less than €20 - that would come to €400 for a twenty tubes, not leaving much change for the manifold and u-tubes or heat pipe etc.

The point is that the benefit of flasks is that you aren't stitched into one supplier - there are literally hundreds of factories in China working to a very similar spec. So if you or I go bust, our customers can get them elsewhere. There are only a few standard sizes and the flasks are interchangeable between all of them.

If you buy them in quantities of 40 to 60, you should be able to get these for about €5 each.:)

The panels that we use are CPC panels so there are only 6 tubes per square meters so I suppose that leaves a bit more money to spend on the rest of it.

To be fair to our supplier they send us 2 free tubes with every 100 tubes worth of panels we take from them. As of yet we haven't had a damaged tube so there is a stack of them sitting in the warehouse - with a bit of luck I won't have to pay anything for replacement tubes over the years.

exaisle

I'd be interested to hear views on what the optimum angle for a south facing flat (ie. not tube) panel is.

This may be of interest:

http://www.macslab.com/optsolar.html

Although, on the basis of that website, the optimum angle for panels in Ireland is in the region of 76 degrees, ie. (53degrees x 0.9) + 29) and this is well above what appears to be commonly recommended.

My own basis for agreeing with this is that one wants to optimise the efficiency of the panels in the winter. In the summer, I contend that panels working at lower efficiency because they arent facing the sun directly, will still provide ample hot water.

Mind you, I'm just an amateur.....

E.

quentingargan

exaisle wrote: »

I'd be interested to hear views on what the optimum angle for a south facing flat (ie. not tube) panel is.

This may be of interest:

http://www.macslab.com/optsolar.html

Although, on the basis of that website, the optimum angle for panels in Ireland is in the region of 76 degrees, ie. (53degrees x 0.9) + 29) and this is well above what appears to be commonly recommended.

You have to bear in mind that in some climates (e.g. Austria) you get sunny winter days, so optimising for winter, particularly in a passive house might make sense. I suspect that this website is drafted with such a climate in mind - cold, bright winter days. In parts of Ireland, during winter months, we only get 0.47 KwHrs per sq m per day of insolation.

Furthermore, flatplates work less efficiently in winter than tubes would, so your chances of capturing much of that 0.47KwHrs are slim because of heat losses through the glazing.

I agree that for the most part, your panels will provide more than you need during the three peak summer months when insolation is in the region of 4.5KwHr per Sq M. For that reason, I tend to optimise around the spring and autumn, when there is a reasonable chance that panels at 45 to 50 degrees will meet most of your needs for 9 months of the year.

You won't get much of contribution from flatplates during the other three months - but in most houses that doesn't matter. The central heating is on anyhow, and heats the water on its way to the radiators. The additional cost of heating water is a lot lower than it is during the summer when the only other way to heat your water is electricity, or running the heating very inefficiently just to get hot water.

exaisle

Thanks Quentin,

In my particular instance, I'm using and air-to-water system with UFH to heat the house.

E

quentingargan

Hi Exaisle, If you are using a heat pump, does your heat pump have a setting for bringing the water temperature up to 60 degrees, or are you using the immersion to do this?

I imagine you want to maximise your seasonal availability, so wonder if flatplates are the optimum in your case. I've no axe to grind here - like most people in this business, we sell both. Flatplates score on longevity and aesthetics, while tubes score very effectively on extending the operating season. Q

exaisle

Hi Quentin,

Yes, the heat pump can bring the water temperature to 60degrees.

Whatever the relative merits of flatplates versus tubes, I've gone for flatplates simply becuase of their sturdier nature (stray footballs etc)

I'll probably tilt the panels to maximise their efficiency in early spring/late autumn so probably at about 50-55 degrees.

Unless of course, somebody can suggest something better....

E