Solar hot water - again

08/31/2009 - 06:29

We've been here so many times before but I'm sure that there are others here doing rennovation and thinking about plumbing!We've got a local firm to prepare a preventivo for the plumbing work in our house and its time to make a final decision on what to have where We had asked for a pellet boiler plus 5 radiators to be part of the quote but coming home and taking time to think it over I'm wondering if it makes more sense to just get the pipework put in but leave the boiler/rads as we are never likely to use the house overwinter at least in the next 12 years. A pellet boiler is a pricey item too and it would sit around unused most of the time.Plus as our plumber pointed out it would produce unwanted heat in the summer if it just heated water !So instead we could get a solar hot water system so we have hot water for showers / washing up. These are the figures and I'd love to find out what people think !! Would they do this ? Have they done it?? Are they happy?The System is an active closed loop one needing a pump to circulate fluid - PROBLEMS what about if theres a power cut? We must have roof panels rather than a passive system where you need no pump - lack of space.If the pump stopped working the water could boil in the tubes!!Collecttor on the roof is 30 tube evacuated navitron collector supplying 200 lires of hot water daily . Is this the best type for Italy or is Flat plate betterI've calculate our daily entire water use to be 155 litres for each of us.Thats probably 70 - 80 liters of hot water the rest cold.So 200 litres of hot would be more than enough.Would it be best to add 2 collectors at this stage? Even if we didnt need so much water? We may have guests? It would be best to drain the system when we were not at our house . could we do this?Hot water cylinder is 180 litre vented cylinder but what about adding a thermal store for another 172 litres? Space is another limiting factor as the cylinder will need to be on the ground floor so some loss of heat may occur but pipes will be well insulated. Should we plumb a radiator to take off excess heat for April / Oct eves ?Total cost for parts is around £2000 but we would need the hot water cylinder etc anyway so its not all for the solar.Any opinions ?? Help!!  



SalveCouple of ideas.You could run a low voltage, say 12 or 24v central heating pump from a transformer/battery system that would still circulate water during power cuts. This would work unattended too.You could make sure the pump was on a plug or easily accessible spur and buy one of those silent (or almost) mains generators. If you were clever you could run a few lights etc. too. You would need somewhere with some ventilation to run it, but I have seen some remarkable little generators for sale.  Ciao

Apart from the problem with power cuts, there is a new product on the market from Ariston, solely for domestic hot water production. The model is the Nuos and uses a air/water heating system.This has an internal hot water tank of either 80/100 or 120 ltrs and last prices I had were circa Euro 1000 + IVA. It uses approx 300 watts of electricity in normal mode. Cannot include the pdf of the details, as they were made from the brochure. If you would like them, send me a PM with your email.

You are quite right - solar is a good thing indeed. Having experienced different set-ups with top class evacuated tube panels and cheaper flat plate jobs I find that the best value for money comes from the cheaper ones. We get 5 square metres for €1,200 and they deliver slightly excessive performance in mid summer and then extend the adjacent seasons. Solar energy is free so who cares about efficiency?Many people have thought that they will never come out here for winter but soon change their minds when they find how fabulous it is, so be careful not to ruin a perfectly good house by putting in an inadequate heating system. A good wood burning stove is the most important bit of kit in the armoury and will be good enough to keep a gas boiler 'off'' nearly all the time. Both wood and solar heat sources are unregulated and untimely so you need to store  and smooth the energy in a big tank of water - a heat bank. The DPS heat bank ( comes with all the pumps and controls already fitted and will solve all your problems in one go. Your safety concerns are well answered with a vented system with power free heat dumping. Whatever you do, I would suggest you leave the door open for heat pumps. Within 10 years gas boilers will be heading for the skip and renewable energy, delivered as electricity, will be moving in along with heat pumps. Our target for this year has been to design 'Zero Gas' systems....Thanks to the Enel deal a PV car port will be going in this month and an enticing new prospect looks possible - 'Negative Cost heating'Anyway, good luck with the project; I hope it all goes well.

Thanks for the replies and to abruzzo for the question.  We are sort of halfway there, in that we have a gas system but it is set up to include solar when we get around to it.  We have underfloor heating int he cantina which I would like to think could also use the solar-produced hot water when the house is empty - just as a sort of tick-over system. Not sure if that would be feasible though.I'm also interested long-term in photovoltaics - will they ever actually be cost effective?Abruzzo, we seriously considered then dropped the idea of a pellet boiler.  Mainly because you need somewhere absolutely dry to store the pellets, and in winter in teh mountains (especially if the house is empty) that's difficult to do, given the quantity needed. We have two woodburners, and now that I have finally persuaded the builder that the flue must end above roof height, that makes for cosiness without smokiness. We do also try to shut down a lot of the house for the winter, and put up heavy curtains to make it a bit less open-plan.I agree that winter can be the best time - although weeks of fog, cold winds and rain are not to everyone's taste.  But a bright December morning warm enough to eat outside can't be beat.

In reply to by Annec

Annec, The answers to your questions are YES... slightly.  Winter insolarity is half that of the summer so your panels will not be good for much more than freeze protection while you are away, but at least that gives peace of mind. For a real example, my panels run nearly every day of the winter with the pump starting at 8 in the morning and running until a bit before dark.Are your stufas connected to water in any way? Once you get them adding to the pool of energy you will be able to turn that horrid gas boiler off.As for the PV question... generally the cost/benefit ration is so absurd they would never get off the ground. e.g. 5mq wet solar panel costing €1,200 = about 26mq of PV panels costing €32,000. But with the Enel deal the whole thing is really good. That €32,000 can give you a nice car port and earn €4,000 a year.... giving enough power to run a heat pump and a pool pump amongst other things.

Please can you enlighten me in to exactly what is the ENEL DEAL and how does one go about getting it?We have a farm with a large house and use stufe for heating plus an emersion heater for hot water.  True as far as the heating is concerned it is free for us as the prunings from the trees give us our fuel and more, but really would prefer NOT to burn the wood as it is a polutant.Sorry to sound a little green ,in both respects, but could you advise us where to get futher info Thanks 

If you're burning wood, it is a carbon neutral activity.  You are only releasing carbon which would have otherwise been released as the wood rotted down.  And trees suck up lots of CO2 whilst growing, so its a double bubble. Or that's what I've been told....

 The problem with burning wood isn't so much the carbon emission as it is the fine particles in wood smoke which lodge in the lungs. Where I live in California the installation of wood burning stoves has been banned as the American Lung Association has been educating municipalities on the problem. My mother lives in Tuscany and I've been amazed when I've visited in the fall and winter on how poor the air quality has been from wood burning fires. I know there's no easy or economical answer to heating in rural areas but just think people should be aware of the problems with burning wood. Here's an excellent link on the issue.

If I remember correctly from some of the posts on the old forum, then solar powered domestic hot water and heating only constituted about 20 - 30% of the requirements of a house, before other heat sources were required. This seems to be the synopsis from the linked site in earlier emails. I appreciate that solar can provide all the hot water in the Summer months, but then it gets cloudy and the efficiency drops.I, honestly cannot understand why people want to install solar, GPL, woodburners etc to just live comfortably. Currently, I am working on a project for a 220 sq mtr new build (4 years old ), where they are paying Euro 5000 per year for GPL just for hot water and heating, both on 24 hrs with room temperature 20C. Our calculations reduce the heating and hot water to approx Euro 1500 - 2000 per year and that is using electricity alone.

You've just answered your own question haven't you Badger? With the horrifically high fuel and electricity prices in Italy no wonder people are looking to other means of heating their DHW and CH!!Solar systems will not provide all the hot water from October - April that's true but even if they do from April until Oct that's covered the emissions from running a small car for a year - if you are also doing it for green reasons.By adding a thermal store to a standard system even more hot water can be provided and be made avaiable at more useful times of the day ie showers first thing in the morning.Solar systems will also become more and more economical as fossil fuels run out or are made unavailable.And if they are passive systems or ones run by a solar pump then they can run when the main power is off!   

OK, I agree with some of what you are saying. If you have a thermal store over the winter months, then you have to ensure that temperature is boosted to approx 70C every 2 - 4 weeks to prevent bacterial infection in the showers etc. Your original question was with regard to DHW production for basic summer use and not for heating purposes, but as usual the post changed to then include PV, Heating and DHW.As it only costs about 1200 euros per year to heat my house 24/7 and supply constant hot water using electricity, then that is my demise ........ so be it.It only costs me about Euro 3 per week in the summer months for hot water, but I do have the advantage of not having glass panels all over the place.I am quite happy not to make any comments or suggestions if you feel they are not informative.

please don't regard it as a personal criticism if I chose to debate the points you made - I feel more strongly about  the benifits of a solar system whereas you think the panels are unattractive and would prefer to use electricity.Its not really enough to fall out over is it ? I'm interested in hearing all opinions!quote 'I am quite happy not to make any comments or suggestions if you feel they are not informative.'Does anyone think that we can find a complete kit for the Navitron price ( £1,500 expensive whereas navitron are evacuated tubes.) in Italy ? They seem to be flat plate collectors which are much more. 

On Badger's point about having to periodically heat water up in order to prevent bacterial growth (I suspect he's thinking of Legionella), that really only applies if the hot water is coming from a hot water tank as most Brits think of one.If you have a "Thermal Store" system (which is something solar pretty much requires), the hot water in the tank is static; once the tank is filled, is just sits there absorbing and giving off heat. Inside the tank, there is generally at least one input heat-transfer coil connected to the solar panel and one output heat-transfer coil connected to your cold water supply on one end and your hot water piping on the other. (Many Thermal Store tanks have more than one heat input coil so you can, for example, use your wood fire or pellet stove to heat the tank and so provide domestic hot water.)The volume of water in the heat transfer coil connected to the domestic hot water pipes is minimal, so saying you have to heat up the system regularly to prevent the growth of disease organisms is true only if this is also necessary to prevent bacterial growth in the pipes in any house.Many Brits seem to have problems getting their heads around the Thermal Store concept since it is sort of the reverse of how a British hot water tank works. They seem to think that the only way to use solar energy to heat domestic hot water is to connect the panels to a heat transfer coil suspended in the water tank and then have the water in the tank flowing out the taps.In fact, this would be a very silly approach in Italy because of the lack of cisterns in domestic water supplies here. If you wanted to use this method and take your hot water directly from the tank, it would have to be built very strongly to withstand the sometimes fearsome pressure of mains Italian water. Obviously, a strongly-built tank will cost a lot more than one which only has to deal with the pressures exerted by the static volume of water it holds.As far as the question of finding kit cheaper than Navitron's in Italy is concerned, I suspect you'd have difficulty doing so.There are lots of technical arguments for and against evacuated tube systems as opposed to flat plate collectors, but I really don't want to get into all that. I believe that the evactuated tube systems sold by Navitron are a sensible approach for Italy and their kit is good value and as good in quality as any you're likely to find here.Unfortunately, I can't cite personal experience of using a Navitron system in Italy, because ours is still -- over a year after it's delivery -- sitting in the barn waiting to be installed! There are various reasons for this, but difficulty in finding a competent plumber who seems to be someone I can work with has been a major factor. Installing a solar water system isn't rocket science and it's something I'd almost certainly do for myself if I lived in Britain, but I decided to hire a plumber to do the job here because of the lower cost of plumbers in Italy and the convenience of not having to faff around with planning in detail all the gubbins I'd need and then acquiring them from an Italian plumbing supply place. However, since it seems that every plumber around here is very busy over L'Aquila way (no doubt doing charity work), I'm beginning to wonder if the only way the job is going to get done is if I spend a lot of time sketching pipe runs, counting compression fittings and figuring out what the Italians call all the various bits and pieces I'll need!Al

its so difficult even getting something bog-standard done unless you do exactly as told by the plumber!!I'm dreading showing the plumber my Navitron info as I can just imagine the reaction! Sucked lemon face as my friend outs it!!

..Budgie, sorry to ignore your question - I've been on a beach for a week - I see it has been answered anyway... and annec has cleared up the green issue of burning wood too.. I would go further to say that to be totally green with wood you should grow lots of it then cut it down and bury it deeply - sort of un-coal mining - but as a wood stove enthusiast I'll be burning mine.To add to bunterboy and allan mason's comments on heat banks - The Pandora from DPS Ltd is hugely upgraded for 2009 and is called the Xcel. A lovely stainless tank with masses of extra bosses for heat pumps etc and two really big ones for fitting gravity circuit stufas. All the pumps and wiring come on the tank so there is minimal work to do to fit one. An important principle to gather is that ALL connections to the tank are direct except the solar one which is via a coil. The water in the tank is unpressurised and is the same dirty black stuff that goeas round the rads, floors etc. The clever bit comes when everyone wants to have a shower at the same time. The hot tank water gives its heat to the pressurised mains water via a heat exchanger. This allows 160Kw to hit the water giving flow rates of 45 litres a minute and the hot water is POTABLE. You can fill your kettle from the hot tap!As for the wood vs. heat pump debate... Wood is the cheapest fuel available here and some of us have a bit of our own which helps. Also there is something about a fire which is so hugely satisfying that I suspect we would have one even if it cost more. As it is €2,000 gets you a good one. Heat pumps are super bits of kit but more suited to modern well insulated houses with lower demands. They are not normally very powerful. To compare - an 18Kw wood stove can heat up a 300mq stone house quite adequately (preferably to 21 - 22C for me), but that much power on a COP of say 4.5 would take 4Kw of input power (two pool pumps roughly). The norm is half that but still useful for all that. So it seems to me that we could stop arguing about this. We love wood stoves and with good systems engineering you can integrate a heat pump to make a really good year round workable system with 'ZERO GAS'.Allan Mason - I do install solar gear on my patch but you are a bit far out for me. Maybe a couple of hints might encourage you to have a go at a DIY job. Although solar is free the return on capital is not too hot so you have to keep it cheap €4,000 say. We currently get 5mq of plain old flat plate jobs for €1,200. Ground mounting is easy DIY. Don't cast a concrete pad. Use concrete filled drain pipes to make legs and gravel underneath. Insulated 16mm copper tube should be easily big enough ( I can check calcs for anyone that asks) put it in that red plastic tubing before you bury it and squirt foam all around it as well to keep out rats and water. Don't forget .75mm twin flex wire down one tube as well for the panel sensor. The other bits come cheaply and easily from 'The Solar shop' - great site. You'll need a pump station and a controller (can come combined) and an expansion vessel. Don't buy €70 worth of antifreeze - car stuff will do. Use a weed sprayer to fill the system.... There - that's saved you a grand already!  PM me if you get stuck.

Thanks for that great advice!I would feel worried about a solar collector at ground level if a house was not occupied all of the time.Surely they are vulnerable to vandalism or accidental damage? Also Italian wildlife seems to see any new object of its territory as a food source .Even plastic window seals on another house have been attacked by woodpeckers!The advantage would be no need to get planning permission?The last time I asked in our Municipio they told me to get the Geometra to submit plans - thats another £500 on top of the solar system costs!I'm trying again with a photo and measurements in the hope that they will pass it without me needing to pay a Geometra.I feel loads clearer now on what system we should go for.