Geothermal Heating/Cooling - help & suggestions

Originally Posted by Flower

We are located in Echuca, the house which we are planning on renovating was built 45 years ago and had hydronic heating (wall) installed but due to high running costs was no longer used (about 20 years ago). We plan on installing a bore for garden purposes. The house has timber floorboards and you can walk underneath it and is located in a flood area.

With the extensions, we plan on having quite good insulation on the windows, walls and floors.

Is it an advantage that the hydronic heating exists in the house? We would be using a new system for heating and cooling, however would it be suitable as the main and only heat/cool source with our temps -3 to 45?

No natural gas is available at the site - thus our searching for a cheaper alternative.

As there is a current hydronic heating system in the house and we are planning on sinking a bore and require heating and cooling, is there a financial advantage in using a geothermal system.

It was recommended that we use a open loop system which would involve extracting water from the bore, passing it through the ground source heat pump and then using the water in the home and injecting the remainder back into the aquifer via a second borehole?? (Can read it but don't necessarily understand it!)

The new extensions which would require a new heating system would be quite large with a high ceiling and the original part of the house is not currently cooled by any means.

Any suggestions? Any financial advantages?

Your situation is very similar to Tasmania in that (1) it's fairly cold and (2) natural gas in Tas is in fact a new industry (the Hydro got access to it late 2002, some households from 2005 onwards but most still don't have access) with very few people in Tas having ever used gas for anything other than a BBQ.

Your options for the energy source are, in practice, solid fuel (wood, and coal if you can get it), electricity and fuels derived from oil (diesel, heating oil, LPG).

If keeping the cost down is an aim then forget anything based on oil and don't go for a direct electric system (ordinary electric fan heaters etc). That leaves you with wood, heat pumps and off-peak electricity.

Air sourced heat pumps (reverse cycle air-conditioners) are very popular in Tas now but many never use them for cooling at all. They're installed simply because they are a cheap means of heating the house (don't really need much cooling down here ). If a heater works well enough in Tas then it should work well enough in any other state...

Air sourced heat pumps lose output at very low temperatures. They should still achieve an average of 300% efficiency though so power consumption will be low. But it needs to be big enough to work properly when it's very cold. Alternatively, a smaller unit with some other form of heating as backup for the coldest days is also an option if you like the idea of having a wood heater etc but don't want to use it regularly.

A geothermal system won't lose output when the outside temperature drops. As long as it's sized and installed properly it should work just as well as gas.

Personally, I'd go for some type of heat pump unless you want to use wood. Either of those should be fairly cheap to run (assuming mains power and reasonably cheap wood) so it's personal choice.

Geothermal heat pumps are more efficient but costs more to install. Whether you use the hydronic system or not is really up to you - you could just install a split system or ducted air-conditioner as an alternative if you wanted to (and it's a more practical cooling option).

You can get a wood-fired boiler to use with the hydronic system if you want to. Obviously you need to load the wood etc regularly but there are some that are automatic for heat output adjustment (thermostat) and only need filling with wood twice each day.

The other option is off-peak electric. It's not energy efficient, it will use a lot of power, but in most cases the power is relatively cheap which offsets that financially (though it doesn't do a lot of good for the environment). You'll need a very big water storage tank to make it viable since it's only on for 6 - 8 hours each night. It can be done and works fine if you can fit a suitable tank in somewhere - we're talking about something pretty big and not your normal household water heater though.

Do you know how much you pay per kWh for electricity?

Thanks for your reply and comments, just checked the invoice and it states kw/h is .165800 Peak. Hope this helps.

Looked at a price for Wood boiler for the current hydronic and that was about $5,000 which was about 2 years ago, little reserved about wood heating but certainly something to keep in mind as a backup option.

Geothermal hydronic heat pumps are incredibly efficient compared to any other form of heating. Think COP (coefficient of performance) of 5 - 6, versus 3 - 4 for the best air-to-air heat pumps. Also underfloor hydronic is largely radiant heat which just seems more comfortable. Unfortunately, hydronic is much less effective in cooling mode.

Downside is that there are very few domestic size installations in Australia so you may be the guinea pig whereby your installer learns his trade. Also the cost of the bore holes can be prohibative. For a closed system you may need 200 - 300 metres of bore hole(s). For an open system you need two holes - in heating mode one to suck relatively warm water and the second to discharge cold water, and plenty of available water. Scandinavia leads the world in geothermal heat pumps and many in Europe think that Nibe brand is the best.

Also, have a look at the ORER website - federal Office of Renewable Energy - which pays massive subsidies for air-to-water heat pumps but is strangely silent on the more efficient geothermal.

Keep us posted as you research.

Graeme

Hi Graeme,

Thanks for your reply and suggestions - will look into those. Since my post, I have had a little feedback from a company dealing specifically in this area and they suggest to seriously look at an open loop as we are also going to sink a bore for our garden. Perhaps there might be additional savings since we are already boring into ground water.

So fingers crossed, already having hydronic heating in the original area/bedrooms of the house and sinking a bore anyhow, the gods might be telling us something!

Keep you posted.