I'm trying to source a ground source heat pump to connect to a ground loop I'll be installing under my new house build, There seem to be plenty of air source pumps but I'm struggling to find ones that I can connect to a ground loop.
ground source heat pump
(33 posts) (11 voices)-
proftournesol
MemberPosted Monday 27 Jan 2014 @ 9:46:37 am from IP # -
proftournesol
Memberwe have an energy efficient house but we still need hot water! The winter temp drops to -5 degrees though
Posted Monday 27 Jan 2014 @ 11:28:39 am from IP # -
Bushwalker
MemberI wouldn't call them 'horrendously' expensive. They do increase the cost of a ducted system because of the ground loop expense, and payback time on the added efficiency is long. Compared to a small split system, sure, they are a lot dearer, but compared to an equivalent ducted system the increase is for the cost of the ground loop which usually involves drilling.
There are probably a bunch of Chinese units available, but in the first instance try the people at GeoXchange: http://www.geoexchange.com.au/waterfurnace.aspx
If you only need hot water and your minimum temperature at night is -5C then an air source heat pump HWS may do the job for you.
Posted Monday 27 Jan 2014 @ 1:40:49 pm from IP # -
middo
MemberWhat is the location? Ground Source is popular at extreme latitudes as Air Source efficiency starts to take a dive as temp & humidity drops (once you get -7oC for prolonged periods humidity drops to close to 0 and so the specific energy density of the air becomes lower and thus the system less efficient).
Don't get me wrong I love the physics of Ground Source, but I wouldn't pay a significant premium for it over air source (plus rest of things such as service / installers etc.. should be cheaper for Air Source as the market is bigger) . Australian climate is just so much more mild than Northern Europe so the low temp issues just aren't a factor for most regions even a few days at -5oC you still get hot water but it will be less efficient.
Posted Monday 27 Jan 2014 @ 2:28:16 pm from IP # -
Bushwalker
MemberActually, GSHP has been all the rage for 20 or more years across the US at all latitudes. There is an efficiency benefit over Air Source regardless of the location.
Why haven't they taken off in Australia? Mostly because of the expense. They are a niche market here so the volumes are small and the installers never get cracking because of little competition. Few homeowners will take on long term paybacks for efficiency gains, but we are slowly heading that way.
Having spent time in Europe, I'm always shaking my head when we go to the snow here. Those are places that should have the high latitude technologies employed by the truckload but do not...
Posted Monday 27 Jan 2014 @ 2:55:38 pm from IP # -
middo
Member-5oC isn't snow country. Perisher gets -10oC most nights in Winter: http://www.weatherzone.com.au/climate/station.jsp?lt=site&lc=71072
-5oC is just inland temp in Victoria i.e. Ballarat or Bendigo get that regularly 1st thing in winter mornings. Since a heat pump and storage tank you should program to operate at sunset when air temp is the highest to get as much free energy as possible.
Ground Source has lots of advantages;
-Average temp of the ground stay much high in winter so you start with more energy per unit of mass. But you may have less in summer, in Spring & Autumn you are probably even.
-Specific Energy Density of the circulating liquid is much higher than "Air" so more efficiency there as well (not as much difference as you would assume).
The downside is you are buying into a small market niche in Australia against current generation Air Source solutions that are cost effective due to "relative" mass market penetration.
The real question is the efficiency, and Air Source today are remarkably efficient. i.e. Ground Source efficiencies are 250% to 300% but Air Source are 220% to 300% (took the efficiency figures straight from http://www.energysavingtrust.org.uk/ as a generally reliable source). So to me the math says go Air Source unless you really need Ground Source for a reason such as very low temp.
Posted Monday 27 Jan 2014 @ 3:27:53 pm from IP # -
Bushwalker
MemberAgree that air source have improved efficiency considerably, and for a well insulated, energy efficient home where use requirements are small the differences in installation cost may make a GSHP the lesser option.
prof, can you provide more information on your requirements?
BW
Posted Monday 27 Jan 2014 @ 10:21:51 pm from IP # -
Benny
MemberThose cold nights would probably be on clear sunny days too wouldn't they ? When a solar HWS (ET) would give you warm water that could be easily and cheaply boosted if needed far cheaper than the cost of GSHP installation. That is if cost is an issue for you.
Posted Monday 27 Jan 2014 @ 10:24:25 pm from IP # -
proftournesol
MemberWe are building in the Ovens Valley, NE Victoria. Temperature range of 45 degrees to -5 degrees with daytime temps often not too much above 1-2 degrees for much of the day during winter. We are building a nearly passivhaus with R8 insulation values and a Zehnder ERV with a ground loop for internal temperature management. We are looking at hot water options: either evac tube solar, heat pump powered by our PV. Evac tube systems need boosting here and we want to avoid adding gas. Another alternative would be to add some micro electric instant heaters in eah bathroom but as we are excavating for the ground loop for the Zehnder (a horizontal loop) there would be virtually no added cost for an additional loop for a ground sourced heat pump for the hot water although I'm struggling to find a local supplier of ground sourced heat pumps.
Posted Monday 27 Jan 2014 @ 11:08:00 pm from IP # -
Bushwalker
MemberI've never seen a GSHP hot water system. Many GSHP A/C systems have a desuperheater circuit that can be connected to the HWS. If you are close to passivhaus standard you won't run an A/C much, so that's not much help.
If the information helps, we're using a Siddons split ASHP HWS and the quarterly energy use is approximately 200kWh per quarter. Long term range from 150-250kWh, 4 person household.
Off Topic, but can you point us to more info on the Zehnder ground loop please?
BW
Posted Tuesday 28 Jan 2014 @ 12:29:34 am from IP # -
proftournesol
MemberBushwalker, what temperature range are you using your ASHP in? How does it manage in winter?
Zehnder info at air2energy.com.au
It will give us 3 degrees of heating and cooling but we'll have a supplemental wood pellet heaterPosted Tuesday 28 Jan 2014 @ 12:47:08 am from IP # -
Bushwalker
MemberAdelaide hills zone. Low of around 4C, never seen water frozen on the ground like I did when I was a kid in Wangaratta not far from you.
It's on off-peak so it runs at the coldest times of the day. I think we installed it 2008, has never missed a beat, or run out of hot water. (hope I haven't put the kybosh on it by mentioning that)
41C here today, hot water is the las thing on our minds. Gusty winds. Worst kind of fire weather.
Thanks for the Zehnder info.
BW
Posted Tuesday 28 Jan 2014 @ 1:35:27 am from IP # -
proftournesol
Memberwe have that weather for the rest of the week
I'm just a little concerned about running out of hot water in winter, especially if we do something like have a bath (who wants a bath in summer?)
Posted Tuesday 28 Jan 2014 @ 1:45:27 am from IP # -
Solgen
MemberProftournesol
In the 90's when I worked for the Energy Technology Centre we did a lot of testing of emerging technologies. One of them was ground source hp, there were a number installed in NSW and we did extensive testing of one installed in a house in Wagga. The performance was impressive. The unit was a Waterfurnace with a 2 speed compressor, at low speed our test gear showed COP of 6 (ie. 600% efficient)and at high speed the COP was still above 4. However, while its operating costs were impressive its capital costs were not, then they were 3-4 times the cost of an air source heat pump. The marketing of them was based on low operating costs that in a few(?) years they would pay repay the capital costs. However, this was all based on the US market where apparently air conditioners are left on 24/7 all year, I doubt that that applies in Australia. So overall, they are impressive but expensive.
A good quality air source will easily cope with -5°C, just check out the snow fields or Cooma, where minimums often go down to -12°C and yet the air source units work fine.
Other testing we did was on the Quantum heat pump hot water systems (now marketed as Siddons?), we found that systems in colder areas of NSW worked well when we tested them in July. We even tested one system which had the collector panel wrapped around the tank and which was located on the southern side of a house in Glen Innes (1000m asl), in July the whole system was one large block of ice and yet it was still producing hot water!
My advice forget about GSHP just go for air source.Posted Tuesday 28 Jan 2014 @ 6:47:04 am from IP # -
proftournesol
MemberOK, sounds like good advice Solgen
Posted Tuesday 28 Jan 2014 @ 8:24:04 am from IP # -
proftournesol
MemberWe are going to use a Sanden heat pump as it'll probably have adequate performance and much lour cost
Posted Sunday 9 Feb 2014 @ 4:38:54 am from IP # -
johnmath
MemberBushwalker said:
Adelaide hills zone. Low of around 4C, never seen water frozen on the ground like I did when I was a kid in Wangaratta not far from you.In the '80s I had a mate at Birdwood, where it regularly got down to the minuses at night. He had the River Torrens flowing across the bottom of his property, and the water in the river never dropped below 10 or 15 degrees in winter. He bought an old 3-phase dairy refrigeration unit and put the evaporator in a 44 gallon drum, which had water pumped into it from the river. He put the condenser in a wooden box with a ceiling fan to blow the warm air into his living room. As a space heater it was very effective and cheap to run. However, if the pump intake in the river blocked and water stopped flowing up to his drum, he had a 44 gallon ice block in about 20 minutes LOL.
Posted Sunday 9 Feb 2014 @ 9:23:47 am from IP # -
johnmath
MemberSolgen said:
ProftournesolIn the 90's when I worked for the Energy Technology Centre we did a lot of testing of emerging technologies. One of them was ground source hp, there were a number installed in NSW and we did extensive testing of one installed in a house in Wagga. The performance was impressive.
Emerging Technologies? When I first moved to the "big smoke" in 1972, one of my friends lived in a suburban house that was built in ~1969 and had "ground sourced" reverse cycle air conditioning. It actually used a large in-ground swimming pool as the ground source. In summer the air conditioning system doubled as the pool water heater, and in winter the pool water was usually at a higher temperature than the ambient air, thus improving the COP both in summer and winter, plus heating the pool in summer for free!
Posted Sunday 9 Feb 2014 @ 9:33:36 am from IP # -
grapenose
MemberDon't want to hijack the topic but as johmath has bought up something I've been thinking about, I would be interested in his feedback. I have a 70000 litre underground water tank that I've often thought would be an ideal source to cool and heat the house. Any ideas on how I could do this?
Posted Monday 10 Feb 2014 @ 4:52:12 am from IP # -
proftournesol
MemberFrom the reading I've done 100,000 or bigger is optimal. All you do is coil the ground loop inside the tank
Posted Monday 10 Feb 2014 @ 4:56:07 am from IP # -
John P
MemberI proposed this very approach to a friend in the 1970s and he got as far as building the pool with all the connections in place but . . the marriage failed and so did the research project.
The use of water as a heat store has a lot of merit due to the high specific heat of water - 4.2kj/kg/degree. Water should even be considered as thermal mass in houses - large heat storage capacity in small volumes.
It has been done but not very often - probably due to a lack of imagination.Posted Monday 10 Feb 2014 @ 10:39:25 am from IP # -
grapenose
Memberproftournesol said:
From the reading I've done 100,000 or bigger is optimal. All you do is coil the ground loop inside the tankI would then have to find some way to circulate the water within the loop around the house.Do I assume that I need a heat pump etc. Now I'm getting confused and have no idea of the cost associated with such a system.Perhaps I need a basic guide to ground heat pumps.
Not sure I want to go down that route, was thinking more of a do it yourself system that I could use to heat/cool the living area near the tank not all the house.Posted Monday 10 Feb 2014 @ 10:29:45 pm from IP # -
Bushwalker
MemberCirculating the tank water around the house may help, but that would not be called a ground source heat pump.
A ground source heat pump has a compressor like a fridge and it transfers heat from the house to the ground (or in your case, tank) or vice versa. Heat pumps have efficiencies in the 3x range, meaning that they use 1Kw of electricity to transfer 3Kw of heat.
They also continue to operate in adverse conditions but at reduced efficiency. For instance, it might be possible that your tank is too small for the energy load of cooling your house, and the water in the tank rises to ambient as a result. The heat pump would continue to add heat to the tank until it reached a limit beyond which it could no longer transfer heat.
Without the heat pump, the tank water might be a useful transportable thermal mass.
BW
Posted Monday 10 Feb 2014 @ 10:43:01 pm from IP # -
grapenose
MemberThat's what I thought about a heat pump.As the amount of water in the tank varies throughout the year,going down as little as 30% during really dry spells, I can't see a heat pump being an economical proposition.
Must be some way I can make use of the thermal mass.Running poly pipes from the tank under the house with some sort of pump connected in the circuit,but I would need a heat exchanger, any ideas.Posted Wednesday 12 Feb 2014 @ 3:27:03 am from IP # -
Bushwalker
MemberI don't think I'd circulate it, but that is an option.
I'd install a large tank of some sort in the house. It could be a collection of 200L drums or a massive glass tank or something. The idea would be to stabilise the temperature in the house by adding a substantial thermal mass. The advantage of using water and an external underground tank is that in summer the water can be exchanged with the cooler water in the underground tank delivering an immediate refresh of the thermal mass.
Google turned up this regarding heating (wrong time of year, it's another record day in Adelaide): http://www.builditsolar.com/Projects/SpaceHeating/AWaterWallIntro.pdf
BW
Posted Wednesday 12 Feb 2014 @ 4:47:13 am from IP # -
dibouski
MemberHi,
Am wondering if this is the right place to get some info on using the aquifer to cool the A/C discharge gas before it enters the condenser.
I'm sinking an extraction/abstraction bore but am damned if I can find anyone who can supply a unit that will accept the HEX.
HEX unit is ex US too.
Thoughts?Posted Monday 7 Jul 2014 @ 6:11:04 pm from IP # -
Bushwalker
MemberWhat is a HEX unit?
Posted Monday 7 Jul 2014 @ 9:50:37 pm from IP # -
David
Membergrapenose said:
Fascinating link. Will seriously give it some thought.My only concern is that I had a Water Wall tank that leaked which would be a real problem in a house.Put a drain in the floor and ensure the floor drains to it, as just in case, if retro fitting then a drain tray or similar would offer a peace of mind option, a tank is unlikely to collapse suddenly, they leak for a longtime first, if one takes notice of warning signs then you don't get disasters.
Posted Tuesday 8 Jul 2014 @ 1:25:53 am from IP #