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

championc

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

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.

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

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

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

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

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

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

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

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.

John T Carroll

josip wrote: »

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.

The savings that I calculated above are based on utilising the full output of 1300 Kwh/Annum ( 30 E.tubes), so even if the hot water consumption increases dramatically then I cant really see any improvement in payback time. However you can now get E.Tube array manifolds to which you can simply "plug in/on" extra tubes as required, the incremental cost of this will be
relatively low as you will already have installed the main system, this will then certainly shorten your payback time.

josip

John T Carroll wrote: »

The savings that I calculated above are based on utilising the full output of 1300 Kwh/Annum ( 30 E.tubes), so even if the hot water consumption increases dramatically then I cant really see any improvement in payback time. However you can now get E.Tube array manifolds to which you can simply "plug in/on" extra tubes as required, the incremental cost of this will be
relatively low as you will already have installed the main system, this will then certainly shorten your payback time.

Is plugging in the extra tubes something a householder could do or would an installer be needed?

Does the cylinder size have to be dimensioned according to the number of tubes to maximise the benefit?

John T Carroll

josip wrote: »

Is plugging in the extra tubes something a householder could do or would an installer be needed?

Does the cylinder size have to be dimensioned according to the number of tubes to maximise the benefit?

I'd say it would be prudent to get an installer for two reasons: safety, as the tubes will normally be roof mounted and the water/glycol mixture may need topping up depending on the type of E.Tube fitted.

The cylinder size and solar coil area would also need to be sized correctly on initial installation.

John T Carroll

josip wrote: »

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.

If one can start off with young children using a shower with a flowrate of 5 to 6 LPM rather than the "power" shower of, say 10 to 15 LPM then they will get used to that, its much harder to downsize without having a revolution on your hands.

tipperary

ammc wrote: »

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.

Hi, one of these will give you what you need. You can view data over a day/week/month or custom time range, gives a great insight into how your system functions (todays output attached).
After getting one I ended up changing my controller to one of these units. It's a solar controller that also controls the immersion. I switched to nightsaver power also. I previously ran the boiler to bring the cylinder up to temp, but this wasn't using the boiler very efficiently as the boiler was almost always coming on just to heat the water (we don't turn the heating on very often due to stove and well insulated house). The immersion controller paid for itself in less than a year:D.

Qualitymark

I wonder if the large and set-to-increase water prices will hit the sale and use of solar hot water panels.

Qualitymark

Qualitymark wrote: »

I wonder if the large and set-to-increase water prices will hit the sale and use of solar hot water panels.

I very much doubt it, most solar systems are closed loops so "consume" no water as such.

If anything it will make them more useful as people would waste less hot water so the cylinder would be able to get hotter as less water is drained from it.

The solar heated water is less likely to run out if people are using less.

daved1975

Hi. I am thinking of getting solar panels. I have a bungalow in wexford. Any advice on types and a reliable company to get them from

StaroftheSea

Hi,
We are building a new house and are unsure as to go for thermodynamic panels or kingspan Solar panels for domestic hot water. As far as I know the thermodynamic panels heat 100% of DHW requirements, while the Solar panels only provide a proportion of it. Given that they are both coming in at a similar installation cost, why would one go for the kingspan instead of the thermodynamic?

Thanks,

freddyuk

Because solar thermal systems only have a tiny power drain from a pump (25+ watts) which runs for short bursts thus is basically "free" once installed. Occasional fluid replacement is recommended. A Thermodynamic system requires constant power to run the heat pump (800+ watts??) to make it work thus is effected by the rising cost of electricity over the long term.
You need to calculate the benefit of using the immersion to top up solar thermal (or standard boiler) which may be already installed and consider the payback times/ replacement costs. It is easy to calculate the cost of heating with an immersion based on time/volume so how many cylinders of hot water can you get for the cost of installing and running and maintaining a heat pump (thermodynamic) system.
Replacing a solar thermal pump is easy and cheap if ever required. Replacing the tubes (which are recommended over flat plate) is also very cheap although I would not expect to have to do this for many years.
Replacing a thermodynamic unit would be much more expensive and their service life is not known.
There are other makes/brands of solar thermal and it is how they are installed and serviced not where you get them from which is vitally important for long term, trouble free service.

StaroftheSea

Thanks for that Freddy, we are still at a loss to know which to go for. From reading other forums on solar panels it seems to me that they really are not any more cost effective than an oil burner for heating hot water when you take into account the installation costs and servicing etc. . It seems the only reason people are installing them (when you cut through the sales pitches) is simply because they have to because of the new regulations. . . That's 5 grand that could have been put towards something that would actually benefit the house rather paying lip service to the regulations. . .

quentingargan

StaroftheSea wrote: »

Thanks for that Freddy, we are still at a loss to know which to go for. From reading other forums on solar panels it seems to me that they really are not any more cost effective than an oil burner for heating hot water when you take into account the installation costs and servicing etc. . It seems the only reason people are installing them (when you cut through the sales pitches) is simply because they have to because of the new regulations. . . That's 5 grand that could have been put towards something that would actually benefit the house rather paying lip service to the regulations. . .

It really depends on your hot water use in the summer time. Some people don't use a lot of hot water over the summer, and would be better off using solar PV to meet the regulations in Part L. Especially on larger one-off houses where solar thermal starts to get over-sized. The hardware for a PV system can be as little as 2 grand and requires no maintenance. But other people use heaps of hot water and solar thermal might then stack.

Kingdom

Sorry for bumping the thread, esp with just a personal query. I had put out feelers on another forum re solar panels (I'm quite ignorant about it all - not intentionally) and someone whose opinion I'd respect greatly told me to look at Solar Collectors, rather than Solar Panels, for a couple of reasons.

I'm moving into a relatively new house in Dublin (1975 build) with relatively good insulation in attic and windows. It is an oil heated system though, and I know from past experience that Oil isn't cheap, and possibly is going to become more expensive.

I've 3 kids, with a 4th on the way. I've seen some prices quoted online for panelling that goes into the ten thousand figures, and I just don't have the scope for that kind of investment right now, but possibly will in 10 years or so, when I'll need to renovate, or extend anyway.
Ideally a solar energy system that heats water and radiators would be the goal, but a short-term system to heat water would be very welcome, provided it's affordable.
Has anyone got any recommendations, or suggestions?
Any help appreciated, and apologies for hijacking the thread.

josip

Kingdom wrote: »

Sorry for bumping the thread, esp with just a personal query. I had put out feelers on another forum re solar panels (I'm quite ignorant about it all - not intentionally) and someone whose opinion I'd respect greatly told me to look at Solar Collectors, rather than Solar Panels, for a couple of reasons.

I'm moving into a relatively new house in Dublin (1975 build) with relatively good insulation in attic and windows. It is an oil heated system though, and I know from past experience that Oil isn't cheap, and possibly is going to become more expensive.

I've 3 kids, with a 4th on the way. I've seen some prices quoted online for panelling that goes into the ten thousand figures, and I just don't have the scope for that kind of investment right now, but possibly will in 10 years or so, when I'll need to renovate, or extend anyway.
Ideally a solar energy system that heats water and radiators would be the goal, but a short-term system to heat water would be very welcome, provided it's affordable.
Has anyone got any recommendations, or suggestions?
Any help appreciated, and apologies for hijacking the thread.

I think you'll have to give up on the idea of heating water and rads. The solar energy just isn't there to do it in the winter when you need it for the rads.

If you over dimension your system to try to get something useful from it Nov - Feb, it'll cost a lot and cause problems in the summer when you'll need to dump all the surplus heat somewhere.

One area for tweaking is the angle of inclination of the tubes/panels. Most are roof mounted and are subject to the 35 deg slope of the roof. Which means they are most efficient during the summer months, when they don't actually need to be most efficient.

A neighbour of ours has mounted theirs at ground level, 15-20 degrees off the vertical so that they are optimised for the winter sun azimut and they still get enough in the summer.

Jakey Rolling

30 Tube parabolic array here in South Tipp - heated 300 litre tank to 45deg today, plenty enough for a shower and all the washing up.

Well pleased with this, but have concerns that it is oversized in the summer, resulting in lots of stagnation with the tubes reaching 200C.

championc

What was your systems' temperature this morning ? i assume your heating system is heating the tank too so maybe it only rose from 43 deg !!

Jakey Rolling

championc wrote: »

What was your systems' temperature this morning ? i assume your heating system is heating the tank too so maybe it only rose from 43 deg !!

Mid tank sensor was down to 24c after morning showers. Heated up from there during the day. Approx 4kwh to heat 150 litres by 20C.

championc

OK. But i'm sure you didn't use 300 litres for showers. Maybe John Carroll would be better able to tell you but from experience, you'd need a few consecutive days of sunshine, with little usage, to top out the system

John T Carroll

championc wrote: »

OK. But i'm sure you didn't use 300 litres for showers. Maybe John Carroll would be better able to tell you but from experience, you'd need a few consecutive days of sunshine, with little usage, to top out the system

Its interesting to see the 30 Tube Parabolic Tube output above of 3.49 Kwh, I have seen my own system (3.84 M2 F.Plate) producing unexpectedly high outputs on sunny days in Nov/Dec for the past 3 years, (see below). I really cant think of any logical reason for this, maybe its because the sun spends its brief daily sojourn mainly in the South?.

I have used your very useful live data because you also have a 30 E.Tube (Non parabolic Array). A parabolic addition may substantially enhance the output of a 30 tube array.

I have used your own link, below, and readings for the 24th Dec. for a number of reasons, one is that the whole of your cylinder on that day is at the same starting temperature of 9C,it is quite easy then to calculate the energy required to raise it to its final temperature of 20C. The other reason is that the Solar Radiation for Dublin on the 24th was 300 joules/cm2 (0.834 Kwh/M2) which is very close to the Solar Radiation of 308 joules/cm2 (0.856 Kwh/M2) for Gurteen (Roscrea?) on the 25th Dec.

By calculation, your system produced 1.92 Kwh ((180*(14-9)/860))+((125*(20-14)/860))on the 24th. This is substantially less than the parabolic array above but one must bear in mind that even though the apparent solar radiation available was practically the same, local conditions, even a few miles apart, can give quite different results, not to mind Dublin vs Tipperary. Incidentally, I assumed in your case that there was little or no hotwater draw off during the morning/afternoon period, if there was some draw off,then the production was obviously more.

https://xively.com/feeds/1928576781/?from_cosm=true (Open this in Google Chrome or similar)

On the 24th Dec my system made a measured 1.94 Kwh from a Roches Point Solar Radiation of 401 joules/cm2(1.11 Kwh/M2). This equates to an apparent system efficiency of (1.94/(1.11*3.84)) or 45.51%, my annualised system efficiency is around 25%, I have seen the apparent efficiency as high as 55% on occasions in the past 3 years during Nov./Dec.

Evacuated Tube suppliers mostly seem to use an annualised system efficiency of 55%, they use this efficiency when calculating the SolarArray Area, personally I think that the efficiency is nearer 40% to 45%, they also dont take cylinder losses which can amount to 700 to 1000 Kwh into account when calculating the array area required, of course this applies to F.Plates as well. Again, just personally, I think most arrays are quite undersized, of course this gives an enhanced system efficiency, reduces the stagnation days and has lower Capital/Installation costs.

John

championc

So from Jakey's system, how many degrees could the whole of 300 litres have been raised on the 25th ? So if the whole tank was at 24 deg, could the whole 300 litres have been increased to 45 deg ?