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Geothermal heat pump

After replacing my standard fridge with ultra efficient chest fridge I have some power to spare that I can use to warm up my house in winter with a heat pump, especially on windy winter days.

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.

Lastly, the electrical energy we use to operate the entire system comes from renewable sources (wind+solar), predominantly from wind.

That way the entire heating system produces NO emissions whatsoever when it operates.

 


Underground tank installation

It is very important to note, that a 1 kW heat pump is enough to warm up our entire @20 square house ONLY because the house is well insulated and has double glazed windows.

This seems like magic. Imagine trying to use a 1kW heater (or 10 light bulbs 100W each) to warm up the entire house. Good luck.

And yet, we tested our system and it works fine. 1 kW of power applied to our heat pump warmed up the entire house interior by 2 degrees in just 1 hour. If I haven't seen it I would not have believed it.

By monitoring heat pump parameters we established that our house needs 16.3 Watt per square metre of living area to maintain the interior temperature 12°C higher than outside.

Geothermic heat pump system is not the only heating source we have. On sunny days our solar reflective heating warms up the entire house and minimizes our need for heat energy.

Low temperature collectors capture maximum amount of solar heat with minimal losses.