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new to this forum, but am always interested in what the real experts (the actual users and DIY people) have to say.
I have been running hydronic heating and winter hot water from a large woodboiler connected to a 400L copper tank with coiled heat exchanger.
I would like to connect solar water heater to this tank, possibly by means of evacuated glass tubes (require about 30 I guess). This appears to be the most efficient and economical.
My tank is about 2m below the roof where I would fit the solar collector. Currently, the tank is fitted with an open expansion cistern. I have the following questions:
Has anyone got experience with evacuated tubes compared with conventional panels. Would I require to fit the expansion cistern above the tubes manifold or do the tubes run a separate closed system? The easiest position would be facing NE on 15 degree roof, not optimum, but less of a problem with tubes as I understand. Best suppliers?
I would welcome any comments, advice.
tks DutchDutch
Jonger Newbie Joined: 08/09/2006 Location: United KingdomPosts: 4
Posted: 11:54am 22 Aug 2007
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Hi Dutch
I have been planning the installation of an evacuated tube system to my house in the uk, the system recommended is to have a closed circuit with its own make up tank as it needs to cope with freezing winter temperatures so needs to have an antifreeze mix, this system them heats a cylinder of water in the conventional way, they recommend a twin coil cylinder, bottom coil the solar coil, the top coil from your alternate source - in your case from the wood burner.
In my own case I am going to fit a second cylinder fed from the tubes which is connected into my main tank downfeed pipe between the cold storage tank and the existing cylinder so I don't have to disturb my existing setup, this then preheats my make up water in my cylinder and for most of the day will mean my existing boiler will not be required. My house layout means I can position the second cylinder so the tubes will thermosyphon through the coil so I don't need a pump, but most systems will need to be pumped if you cannot arrange things that way.
Hope that helps.
JongerJonger
AMUN-RA Senior Member Joined: 10/03/2007 Location: AustraliaPosts: 144
Posted: 09:29pm 22 Aug 2007
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DUTCH where in vic r u if you have the room you don't need to put solar collectors on the roof as long as they face the equator they could go on a stand or even wallmounted verticle below the tank level so they will thermosyphen an not require pumping.Try cris on
0387963010 apricus solar vic he should be able to help or look for the Solco Genius it is a poly unit that can hanldle the cold and can be feed direct from a boiler source it is a zero pressure gravity system Mick Every day the sun shines
& gravity sucks= free energy.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 07:11am 04 Sep 2007
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Thermosiphon systems certainly work, but never as efficiently as a pumped system. I have had both, and adding a pump and a sensitive differential temperature controller makes a huge difference to the performance.
The only hidden trap with a basic thermosiphon system is the possibility of freezing. On a cold cloudless frosty night, the collectors can easily drop below freezing, and that can rupture pipework.
The solution to this is to fit an anti freezing valve to the lowest point in your system. This will dribble water if the water in the collectors falls below a few degrees above freezing. Hot water is drawn back down from the storage tank to warm the collectors.
A proper solar differential temperature controller will start up the pump if the collectors approach freezing temperatures.
Either way, freeze protection is always something to think about for any solar hot water system other than the black plastic swimming pool heaters. Those can freeze, and the plastic pipe just expands. Copper pipe is very likely to split if full of solid ice. Cheers, Tony.
RICHARD Newbie Joined: 03/01/2008 Location: AustraliaPosts: 3
Posted: 12:34am 05 Jan 2008
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I am doing a domestic project for a client at this moment and have had to make considerable enquiries regarding your question. Hope this helps.
1. I have specified evacuated tubes (Abricus System)- 35 in total
2. This is tied up to a 250lt.stainless tank - in this case by the same mfr.
3. From the tank it is fead into a Renai instantaneous boiler. The theory being the boiler functions well below its normal capacity.
4. The water travels, around the dwelling, via a continuous loop providing hot water, at all times to all outlets.
5. In order to achieve this you require copper panels.
It is a highly economical way of addressing the issue of
hydronic heating - infact the most economical way so I have been told.
Now you may be able to help me since I would appreciate some further response to my question (SOLAR HOTWATER & HEATING - RICHARD.
I am doing a small seaside shack 120m2. My clients will not allow bottled gas - the area relies on mains electricity, tank water and an effluent plant for each and every dwelling.
1. The most economical way to address this issue, being hotwater and hydronic heating is via a 'heat pump' eg Quantum or Skyline.
Could you please read the remainder of my posting.
Regards
Richard.
SOLAR ENERGY
KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178
Posted: 03:33am 19 May 2008
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OK plenty on the market LOW pressure water in glass evacuated tubeswould be the least expensive for this option ~48 tubes can be had for $1600 and ~$400 for pump and controller to circulate the water, far better than flat panel systems.
Frost prone areas need copper rod in tube and manifold idea, these are about $900 a unit, easy to retrofit to existing hot water service or hydronic heating.
Problem- what are you going to do with all this heat in summer? removing the tubes over summer is NOT a good idea although they are hardy removal and refitting them is the most hazardous (IE you will break 1 in 40 every time they go in or out unless you have 3 people and kid gloves)1
send me an email if you like karlajensen@optusnet for a supplier if you need one.Luck favours the well prepared
petanque don Senior Member Joined: 02/08/2006 Location: AustraliaPosts: 212
Posted: 05:48am 19 May 2008
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Do you really need a 400L tank?
Having a more modest (smaller) system will ether give better performance under marginal conditions or mean you can have less heating tubes and so it will be cheaper.
dazz Regular Member Joined: 15/04/2008 Location: Posts: 78
Posted: 06:46am 19 May 2008
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where we live it is fairly cool in winter. Around 2șC at night and 10șC max during the day. But summer is mild. we can have hot days over 30șC but most night time temps ar around 15șC
So overnight in summer the house usually cools just the right amount to stay cool inside even on hot days.
So Hydronic heating is only needed in winter, but the demands on a hydronic system are quite big.
A 400L tank and over 100 tubes is common here for a hydronic heating and hot water system. A standard setup for just hot water heating in a 2/3 person house is 160L with 20 tubes. And a lot more if you want hydronic heating as well
Even with 20 tubes and hot water heating only, the system provides enough hot water in summer but only provides 50% of the heating in winter.
So again an oversize system to provide more hot water in winter is not uncommon.
The question therefore is definitely, what do you do with all that heat in summer. A completely wasteful but effective solution is to use radiators to remove the excess from the system. But if you have a swimming pool the excess and be well utilized.
cheers, Daryl
KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178
Posted: 09:07am 22 May 2008
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how do you transfer the heat to the pool without spending another arm and a leg? I have considered this downunder but the heat exchangers I'm thinking are going to be very expensive.Luck favours the well prepared
dazz Regular Member Joined: 15/04/2008 Location: Posts: 78
Posted: 11:33am 22 May 2008
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Hi Karl
I think you will find that heat exchangers are generally expensive becuase they transfer large amounts of heat in a very small space. So the good ones have all sorts of nifty technology in the heat distribution structure etc. Doing so in a small space is vital for a hot water cylinder and desirable for low impact with a swimming pool. But the advantage of the swimming pool is that you have a lot of space to play with and can get bigger. An extreme might be to have a hose running the lenth of the pool and back. The downside is the look and it gets under you feet. My father has used a large copper pipe coil for years. This hangs over the side of the pool and can be lifted out if needed. It's cheap, ugly but does the job.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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