Hydronic Systems in Australia (in particular Solar pre-boosted systems)

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Hydronic Systems in Australia (in particular Solar pre-boosted systems)

(16 posts) (7 voices)

Started 1 year ago by naikun
Latest reply from Greg

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naikun
Member

Hi everyone, I'm new to this forum.

I'm a student at UNSW currently studying in Renewable Energy Engineering.

I'm doing a bit of market research for a project I'm pursuing. We are looking at the feasibility of a gas boosted hybrid solar domestic hot water system combined with pool heating and hydronic heating.

I thought that getting everyone's opinions on this very lively forum would be extremely helpful. I have looked through other threads on this topic and I'm getting varied opinions. I get the feeling that many people come onto here looking for some sort of solar hydronic system, but in the end come to the conclusion that it's much too expensive.

Anyway I've got a bunch of questions I'd love to know your thoughts on this concept, bad, good, whatever. I want to learn as much as I possibly can, and I have relatively little technical experience in this field.

1) What kind of hydronic systems (heat pump, gas boiler, solar etc) have you had installed? And who supplied your hydronic components?

2) What do you think works in hydronic heating (e.g. I've read some stuff about radiative heating being better than slab heating in warmer climates) and why?

3) What doesn't work in hydronic heating (e.g. solar) and why?

4) If you don't mind, a small description of yourself as a potential customer (or someone who has already installed a system) so that I can get a rough idea of the demographic of hydronic system customers. Maybe age range and location would be fine.

5) Lastly, what would you like to see most on the market and at what price range?

Thank you so much for all of your help!

Posted Thursday 25 Nov 2010 @ 2:36:52 am from IP #
sun2steam
Member

1) I installed a smallish system (30 tube collector, 500L tank, 2 radiators) myself using imported product from China as available products in Australia are far too expensive. Not finished yet. But is is clearly too small. I also have to improve the insulation of the house.
2) I believe that slab heating in the Sydney area is a waste of money. Not only most people intend to heat the whole hose (who needs to heat a bedroom?), but it is clearly an overkill in a moderate climate. Radiators are simpler and by far cheaper. Besides the really big demand is in upgrading old houses.
3) In my case solar heating does not (yet) work, because the collector are is to small and because I loose too much heat through walls and windows.
4) are you genuine or are you just naive?
5) For the Sydney area: affordable collectors, tanks and radiators.

Posted Thursday 25 Nov 2010 @ 3:03:35 am from IP #
naikun
Member

sun2steam, thanks heaps for the concise reply, its precisely the information I'm looking for.

To your reply in 4) LOL, how about genuinely naive? I was trying to be polite/ non-invasive, maybe it came across differently?

In any case thanks for all the help mate. Looking forward to more replies.

Posted Thursday 25 Nov 2010 @ 3:24:40 am from IP #
ghostgum
Member

It's often better to ask a student some questions, rather than giving answers.

1. Gas fired hydronic with radiator panels.
2/3. If you are doing solar hydronic, then consider whether radiators (70C water) or slab (40C water) is more suitable, given the water temperature available from a solar heated hot water tank.
How large a tank do you require to store 1-2 days heating? How does this compare with the heat capacity of a house concrete slab?
Look at the heating response times for radiators vs slab.
Is it more or less cost effective to use thermal mass in the building, directly heated via double glazed windows with low U value?

Posted Thursday 25 Nov 2010 @ 4:08:30 am from IP #
naikun
Member

Hey ghostgun thanks for that, it wouldn't be market research if I didn't get market feedback.
I am grateful for your response which actually outlines a few of the issues we are considering.

E.g. radiators or slab, it seems that radiators require less coils, and thus cost reductions, but the higher temperature requirements might lead to issues (especially for a hybrid system). What we were considering is a little different to typical configurations. Like perhaps a condensing gas boiler (for higher efficiency) with solar as a preboost, this would be closed loop. The tank would then be the sole "thermal battery" where heat can be distributed to DHW (through a brazed plate heat exchange), and then a mixing block connected to the tank which would connect to either hydronic heating in winter, or pool heating in the warmer months.

To me it seems more feasible from an energy standpoint to go with slab, but more cost-effective to go radiators (which can also be retrofitted, given enough undefloor space).

With regards to the tank, I'm not quite sure, people have said 500-800L which is seems kind of large to me but may be necessary? I don't know these are the questions I'd like answered.

As for the effects of passive solar heating, I am 100% all for it, and I think it is definately one of the better solutions out there, especially from a green building perspective. Why not just attack the source? I.e. poor insulation/climate understanding.

But relying on passive solar seems dependent on the effects of thermal lag, (so the building cannot be in continual use, but for specified periods of use). Also radiative heating has a competitive edge in giving the home a high-tech feel, (heated tower rails). Having said this the system we are considering would definately be high end. Which once again points to my questions about current hydronic systems' demographic.

I'm not 100% sure but I do detect a hint of cynicism. I'm sorry if I have asked too much as a forum newbie. I'm just looking for market feedback.

Posted Thursday 25 Nov 2010 @ 4:38:12 am from IP #
ghostgum
Member

I've also been wondering about how you would take an existing gas heated hydronic system, and add solar pre-heating. Would you use the solar heated hot water overnight to maintain temperature, and the gas during the day time? The water temperature is likely to be less than 70C, so the radiator panels power output will be less. If the water is down to 40-50C, then it would not heat a house quick enough and you would need to rely on the pump running longer.

Our hydronic system cost about $10k. This was about double that of gas ducted heating. Adding solar is going to add another $20k. If the annual heating bill is $500, and only half of that can be replaced by solar, then the system will have broken down before it recovers its cost. I don't see it working until the cost of evacuated tubes drops, and the cost of about 100 tubes installed is under $5000, or the cost of gas increases greatly.

In summer, a large solar hot water system could be used to run an air conditioner (similar technology to gas fridges), improving the investment.

My estimate of tank size was 2000L. In Melbourne, 5 star 200m2 house uses 149MJ per day over the year, so about 300MJ per day for the 6 month heating period.
2000l * 4.182 * 30C = 250MJ
The same calculation can be done for the concrete slab, although that has a much narrower temperature change.

Another interesting variant it mtbest.net. Low grade collectors are used to preheat water to above ambient temperature, to allow a heat pump to work more efficiently.

I'm always cynical about students asking questions in forums - they have a reputation for wanted quick answers for an assignment. If someone is willing to think and discuss issues, and to make me think about my understanding of the field, then it doesn't matter if they are a student, working or retired.

Posted Thursday 25 Nov 2010 @ 5:13:45 am from IP #
sun2steam
Member

Just a thought, maybe a bit off topic but along the line of solar space heating.

Imagine a solar hot water system with say 60 tubes (tubes are better in winter) and a 500L stainless steel tank (should allow temperatures up to 95C with changed controller setting) with a gas booster set to max 60 C to run not the hot water system but the radiator heating. The gas booster will only kick in when the water from the tank is below 60C and only heats up to 60C, reducing consumption of gas. This should be a quite efficient system and the cost can be significantly reduced as cheap imported hot water systems can be used instead of expensive systems with full Australian certification. These cheaper systems are available with full European certification. This should fit within ghostgum's $5000 cost bracket.

Higher temperatures like 70C degrees may be necessary for radiator heating in cold climates, but for moderate climates it is just too much. And if really necessary the thermostat setting can be changed for the few very cold days. The lower the temperature the lower the heat losses and less expenses for gas boosting.

Posted Thursday 25 Nov 2010 @ 6:05:14 am from IP #
naikun
Member

Thanks ghostgun, I guess what you say makes sense. In terms of market research I must say I was looking for quick answer, i.e. data But I am more than happy to discuss hydronic heating, as it would probably help further my own understanding.

a) Well when we envisioned our system, I think it's quite different from current systems. Due to my lack of knowledge, I'm not quite sure what you're suggesting. Our envisioned system would comprise of a closed loop system, with a gas booster + collectors preboosting the tank water. Keep it at a constant 70C. There will be a different heat exchanger loop, possible BPHE to maintain high flow rate exchange; one for the DHW, one for the hydronic.

I think this system would the tank at the centre of the system as opposed to. Solar -> Tank -> Booster --> Hydronic its more Solar + Booster --> Tank --> Hydronic, so I'm not sure if you'd add it onto an existing gas heated hydronic system.

b) I'm not sure why the addition of the solar will add $20,000 especially after RECs, I don't know numbers, but how would 90 evacuated tubes, pumps and tank equate to that amount. Or did you mean an added $10,000? Either way, I kind of agree, that this system does sound a little too expensive for the average consumer, it would definately be a high end solution (which is why I am here asking!)

c) As a side question, who did you source your hydronic systems from, and waht boiler are you using? Are you using a condensing boiler?

d) With regards to the "gas fridges" are you talking about absorptive coolers or something? This is quite an interesting concept.

e) Your sizing calculation was interesting, so basically your saying you'd need a massive tank (not even looking at the tube amount) to be able to power 5/6ths of the energy requirements. I'll have to talk with the group about this tank sizing issue. The only forseeable problem with that is, the most expensive component would be the tubes right? You'd need a massive amount of tubes to be able to fully heat the 2000L on a cold day. If the amount of tubes is then more reasonable, an gas boosting ends up doing most of the heating, then your making for a very inefficient gas boosting system which now has to boost the whole 2000L AND the hydronic.

f) Mt Best, simply amazing! I also now have to look into the possibility of preheating to make heat pumps more efficient, i believe this has something to do with its Carnot efficiency... Hmm

sun2steam

I like your idea, but wouldn't there still need to be an extra gas booster for the hot water (by Australian standards) even with the 60 tube system. Furthermore, is this open loop? Is potable water running through your hydronic system? And are you sure you'd skip the Australian ceritification if potable water is being used in your system?

Posted Thursday 25 Nov 2010 @ 12:01:37 pm from IP #
dymonite69
Member

GH says "
I'm always cynical about students asking questions in forums - they have a reputation for wanted quick answers for an assignment. "

I would have thought an engineering student could quite easily do the following:

1) Heat/Cooling load calculations
2) Review tech data on hot water heating systems
3) Contact a few commercial hydronic retailers for typical installations and components
4) Get some quotes on HWS

Why would he need to know of specific examples from a forum?

Posted Thursday 25 Nov 2010 @ 1:49:54 pm from IP #
sun2steam
Member

There is no need to use potable water in a hydronic heating system

Posted Thursday 25 Nov 2010 @ 2:10:17 pm from IP #
ghostgum
Member

Naikun,

b. The $20k figure is one that I have read. I haven't priced the components, so it may be less than this. Even $10k is too much given my existing heating bill.
c. Nissl Eichert Heating in Melbourne. Talk to an installer in your city. Biasi radiator panels. Sime 34 boiler, but turned down to about 14kW to match the radiator panels.
d. Yes, I meant absorption refrigerator/cooler.
e. You probably don't want to dimension the solar collector for heating on a cold winter day. On sunny winter days you rely on solar. On cloudy winter days you rely on gas, of if available the energy stored in the tank from a previous sunny day.
You don't want to heat the 2000l from gas at all. It would make more sense to have some valves that bypassed the large tank when it wasn't warm enough. More system cost to reduce the amount of gas used.

Posted Friday 26 Nov 2010 @ 12:06:23 am from IP #
ghostgum
Member

In some hydronic systems using steel radiators, the water is treated to remove excess oxygen, and the system is closed. There are bleed valves on the radiator panels to remove air from the system. Any linkage to hot water tank heat storage would be via a heat exchanger.

For drinking, aerated water tastes fresher.

Posted Friday 26 Nov 2010 @ 12:13:21 am from IP #
naikun
Member

dymonite69

Quote:

"I would have thought an engineering student could quite easily do the following:

1) Heat/Cooling load calculations
2) Review tech data on hot water heating systems
3) Contact a few commercial hydronic retailers for typical installations and components
4) Get some quotes on HWS

Why would he need to know of specific examples from a forum?"

Wow, I'm honestly starting to feel the a stigma against students. If you read my initial post, you would've seen me say that I am performing market research. Perhaps in my naivety, I thought that I could get some statistics from a forum, where people would just nicely answer my questions.

Your completely right, I can calculate heating/ cooling loads, I can review tech data, I can get quotes on HWS, and I can contact retailers for typical installations (yes, I have established a list of installers who I will be contacting for their views, but most of them are plumbers, they might be on site, and they tend not to be too polite.

So here I am on a forum, trying to ask for some help for data on the market not the system. I am trying to get the information as fast as possible so I am exploring various avenues of getting information. If I am not making sense tell me, I'm not here to troll, but please don't patronize me. Yes I am looking for quick answers, but its data collection, it takes about one minute to answer my questions, 1 second to disregard my post, 1 nanosecond of a thought process to disregard your own cyncism.

Posted Friday 26 Nov 2010 @ 2:58:26 am from IP #
CNCandy
Member

I asked this exact question to a Brian at Apricus Australia yesterday. I asked if an Evacuated Tube system could be used to heat an underfloor slab system which my parents have as they were looking to replace the existing gas boiler with some big expensive German made thing. He did suggest a larger than normal tank (500+L) or maybe some tanks coupled together and that anything like a heat pump system would also work. An instant gas boost would also need to be attached. The existing system is fairly large as the floor area is in the region of 350m2 and also radiates downstairs thru the slab to a floor below. House is in foothills area of Adelaide.

My second question to him was can you run a second pipe thru the ET manifold to use to to pre heat hot water for the home as well as the first running to the slab, and the answer to that one was yes. The idea here was that the ET pre heats the water before it hits the gas booster and then enters the house. The roof tiles are also a dark color which would probably assist!

He mentioned a company called Rotex who have something along these lines but haven't quite looked at it yet. Also these sort of systems come at some cost and some considerable plumbing work but it would make the most of the components.

Naikun, You could also take a look at systems like the Blue Gen Fuel Cell and the Cogen Microsystems combined heat and power system that use evacuated tubes!

Posted Friday 26 Nov 2010 @ 3:17:39 am from IP #
TonyT
Member

Hello naikun

You may be interested in my post at

http://www.ata.org.au/forums/topic/should-i-buy-a-solar-hot-water-system-or-a-solar-electricity-system

Regards
Tony

Posted Sunday 20 Mar 2011 @ 1:23:13 am from IP #
Greg
Member

Other posts here http://www.ata.org.au/forums/topic/solar-hydronic-slab-heating-revisited#post-571

Posted Sunday 20 Mar 2011 @ 10:50:51 pm from IP #

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