Interesting Off the Grid OZ setup

[buffalobillpatrick]

Geothermal heat pump system at Mt Best


"The crucial part of a heat pump system is the source of heat. In our case it is 10,000 litres of water stored in pressurised underground tank.

In winter, we take heat energy from this water (we cool it down) and deliver this energy at a suitable temperature to the house interior.

Water in the tank is heated by two sources: the Earth interior and our custom made low-temperature polyethylene solar collectors.

Why is this system energy efficient?

To begin with, the system is designed (with Dr Mirek Piechowski from MP Energy Consulting, who holds a PhD in thermal sciences) to operate at very low heat source temperatures (4-10°C).

In this temperature range, the planetary interior actually heats up the water in the undergound tank, because underground soil temperatures are higher. We turned heat storage loss into heat gain. Isn't it intelligent choice?

Secondly, during sunny winter days our solar collectors warm up our 5°C water to higher temperatures, even on partly cloudy days.

Since solar collectors operate at very low water temperatures (5-10°C), heat losses due to convection are minimal. On a sunny winter day we once managed to capture 57kWh from our 24 m² collectors. Who needs fossil fuels?

Thirdly, our heat pump has COP (coefficient of performance) between 4 and 6 in the temperature range of our heat source.

It means that for every 1 kWh of electricity we use to run the heat pump, we transport 3 to 5 kWh of heat from the underground water tank to the house interior."

[AC_Hacker]

Originally Posted by buffalobillpatrick

Why is this system energy efficient?

To begin with, the system is designed (with Dr Mirek Piechowski from MP Energy Consulting, who holds a PhD in thermal sciences) to operate at very low heat source temperatures (4-10°C).

This is interesting because of what it is not saying, and that is that if you can sufficiently reduce the heat load of your house, these ultra-low temperature heating strategies, such as you have just posted, become possible.

This is actually what I was trying to tell you at the beginning of your heat pump odyssey, but you got insulted and said I was trying to kill your project.

I was trying to point you in the direction of ultra-low temperature heating, which is only possible when you have ultra-low heating loads.

Rave on dude...

-AC

[WyrTwister]

In the summer , do you recoup the cold " stored " in the water ?

God bless
Wyr

[WyrTwister]

A local Christian University has went big tome into heat pumps . I think the first ones , they drilled a well and put a loop at the bottom to exchange heat or cool with the ground water ?

They have a fair size pond , that I think they are now using as a heat / cool sump ?

God bless
Wyr

[buffalobillpatrick]

Mt Best is in South East tip of Australia close to Melbourne.
The yearly mean temp. is 12*C (53.6*F) & windy.
This means that the ground temp. is aprox. 12*C , good for Geothermal.

[jeff5may]

Originally Posted by WyrTwister

In the summer , do you recoup the cold " stored " in the water ?

God bless
Wyr

Yes and no. During cooling season, the geothermal loop will heat the ground. The heat travels through the ground at a fairly constant rate. It can be stored for a relatively short time by insulating or isolation. But eventually, it will bleed off if not used, much like a rechargeable battery.

However, there are ways to guide this extra heat or cool in the ground. For example, you can place your geothermal loop a certain distance away from your basement, so that the heat generated in the summer will arrive at the basement walls and floor in winter. How far away depends on the type of soil, how deeply buried, etc.

During swing season (where you are both heating and cooling your home within a day or two of each other), the heat generated to cool the home one day helps efficiency the next when the system reverses. A few degrees of temperature change in the ground in your favor can add up to hundreds of dollars in savings fairly quickly. This change in evaporating or condensing temperature and pressure is analogous to turning the thermostat down a few degrees while heating, or turning it up while cooling.

[buffalobillpatrick]

Originally Posted by jeff5may

However, there are ways to guide this extra heat or cool in the ground. For example, you can place your geothermal loop a certain distance away from your basement, so that the heat generated in the summer will arrive at the basement walls and floor in winter. How far away depends on the type of soil, how deeply buried, etc.

I'm very interested in this, thanks for idea to research.