Who is good at ground-sourced heat pumps in Australia?
October 23, 2019 4:29 AM Subscribe
I have an offpeak electric 315 litre hot water service with a retrofitted solar thermal roof collector. It accounts for most of the electricity our house consumes, so I'm currently researching heat pump based replacements. The solar collector is still working well and I would like to keep it as part of any new hot water system. If you're in Australia - better still, if you're anywhere near East Gippsland - and have done the same thing, who did you deal with and were they any good?
I also have a split-system reverse-cycle air conditioner that sees occasional use in the height of summer and very occasional use whenever we've been slack enough to run out of firewood in winter.
It occurred to me that in the summer, when I want heat pumped out of the living room and into the hot water tank, heat pumps using ground-sourced rather than air-sourced waste-side heat exchangers, with the heat exchange loops for both the hot water service and the aircon run side by side in the same trenches, ought to work rather well. If you're aware of existing Australian installations using that principle or of reliable and experienced suppliers willing to tell me why it's a stupid idea, I'd like to know about those as well.
I also have a split-system reverse-cycle air conditioner that sees occasional use in the height of summer and very occasional use whenever we've been slack enough to run out of firewood in winter.
It occurred to me that in the summer, when I want heat pumped out of the living room and into the hot water tank, heat pumps using ground-sourced rather than air-sourced waste-side heat exchangers, with the heat exchange loops for both the hot water service and the aircon run side by side in the same trenches, ought to work rather well. If you're aware of existing Australian installations using that principle or of reliable and experienced suppliers willing to tell me why it's a stupid idea, I'd like to know about those as well.
Do you need more hot water heating? I would have thought that more, or more efficient, solar collectors would be a better/cheaper/lower maintenance solution. Heat pump HWS would be about the last option that I (Canberra area) would consider, they have poor reps, costly to buy and run.
If you just want to 'use' waste heat, spending money you don't need to spend doesn't seem to me to be a good use of that money.
If you want to reduce power bills, solar panels and net metering, and connecting the HWS in a way that only, or first, using the solar panels to drive the HWS, would be a better option.
posted by GeeEmm at 1:26 PM on October 23, 2019
If you just want to 'use' waste heat, spending money you don't need to spend doesn't seem to me to be a good use of that money.
If you want to reduce power bills, solar panels and net metering, and connecting the HWS in a way that only, or first, using the solar panels to drive the HWS, would be a better option.
posted by GeeEmm at 1:26 PM on October 23, 2019
Solar collectors like apricus can unfortunately be problematic in places like Gippsland (and Canberra) because of the temperature extremes. They can actually get too hot, and it wrecks them. Addititionally, you get better bang for buck on your roof real estate with solar panels.
Older heat pumps were shite but the newest generations are quite different, which is why they are recommended by all the renewable govt bodies etc.
My efficient electric home group on Facebook would be a great place to share this question.
posted by smoke at 1:56 PM on October 23, 2019
Older heat pumps were shite but the newest generations are quite different, which is why they are recommended by all the renewable govt bodies etc.
My efficient electric home group on Facebook would be a great place to share this question.
posted by smoke at 1:56 PM on October 23, 2019
I've been talking to Nicola on Philip Island and she has dealt with Prof Ian Johnstone at U Melbourne who has come up with some fruitful info. He seems to be into ground-source energy at any scale and at your latitude. She's sent me several links - I can DM them if you're interested - it more about bleeding edge things and installed systems performance though.
posted by unearthed at 11:38 PM on October 23, 2019
posted by unearthed at 11:38 PM on October 23, 2019
Response by poster: Yes please! DM them if they are in some way unsuitable for public consumption, but otherwise why not post them here for the general good?
posted by flabdablet at 12:21 AM on October 24, 2019
posted by flabdablet at 12:21 AM on October 24, 2019
Oh also it should be "My efficient electric home" on facebook - it's not my group, I just follow it. They are predominantly victorian.
posted by smoke at 12:26 AM on October 24, 2019
posted by smoke at 12:26 AM on October 24, 2019
Solar collectors like apricus can unfortunately be problematic in places like Gippsland (and Canberra) because of the temperature extremes. Can you post (or DM me) the source of this analysis please Smoke?
That is quite contrary to my several neighbors' experience, and from what I see around here they are pretty prevalent still. I know over-temperature in the tank is an issue in summer, but AFAIK the solutions are well known, and have been from the early days of this style collectors. In any event, there are other options for solar collectors if that is a concern.
posted by GeeEmm at 1:46 AM on October 24, 2019 [1 favorite]
That is quite contrary to my several neighbors' experience, and from what I see around here they are pretty prevalent still. I know over-temperature in the tank is an issue in summer, but AFAIK the solutions are well known, and have been from the early days of this style collectors. In any event, there are other options for solar collectors if that is a concern.
posted by GeeEmm at 1:46 AM on October 24, 2019 [1 favorite]
Response by poster: I know over-temperature in the tank is an issue in summer
The pump controller on my Endless Solar retrofit cuts off the circulation pump to the rooftop heat exchanger when the feed water drawn from the bottom of the ground-mounted storage tank hits 79°C. Half an hour later the boil-off valve up top starts hissing and carrying on with a spectacular steam plume. It's designed to do this and seems to have no trouble with it.
I've had it for ten years now. It works really well in summer, and I've got the collector tube frame canted up at an angle that optimizes collection from the winter sun so it works well on sunny winter days as well. Not interested in any hot water solution that isn't compatible with it.
posted by flabdablet at 3:26 AM on October 24, 2019 [2 favorites]
The pump controller on my Endless Solar retrofit cuts off the circulation pump to the rooftop heat exchanger when the feed water drawn from the bottom of the ground-mounted storage tank hits 79°C. Half an hour later the boil-off valve up top starts hissing and carrying on with a spectacular steam plume. It's designed to do this and seems to have no trouble with it.
I've had it for ten years now. It works really well in summer, and I've got the collector tube frame canted up at an angle that optimizes collection from the winter sun so it works well on sunny winter days as well. Not interested in any hot water solution that isn't compatible with it.
posted by flabdablet at 3:26 AM on October 24, 2019 [2 favorites]
You guys are completely right, I totally forgot about the venting like a moron!
posted by smoke at 3:44 AM on October 24, 2019
posted by smoke at 3:44 AM on October 24, 2019
These are my friends links which have proved useful
Geothermal, U Melborne Prof. Ian Johnston
U Melborne researcher Asso Prof Guillermo Narsilio, Geothermal, some out of the box ideas in there
Ground heat exchanger thesis
Just some useful papers, actually well worth browsing around the tabs
And some useful installation imagery
posted by unearthed at 2:03 PM on October 24, 2019
Geothermal, U Melborne Prof. Ian Johnston
U Melborne researcher Asso Prof Guillermo Narsilio, Geothermal, some out of the box ideas in there
Ground heat exchanger thesis
Just some useful papers, actually well worth browsing around the tabs
And some useful installation imagery
posted by unearthed at 2:03 PM on October 24, 2019
This thread is closed to new comments.
It may be less expensive for you, if you have land (need at least 80 metres of piping at least a metre or two underground, I believe). However you would have to have a very adventurous installer to hook it up as described and then you would be dependent on them for maintenance etc.
Likewise, I've never heard of a combo solar and heat pump hot water system.
Indeed the only heat pump hot water systems I would recommend here are sanden or steibel electron - they are pricey but the power savings justify it. The rheems and other brands have an appalling rep.
If you want to eliminate hot water as an electricity source, it's very hard to beat heat pump +solar (electricity) panels that run it during the day.
posted by smoke at 1:05 PM on October 23, 2019