GSHP - What percentage of heat energy is taken from the ground?

In summary, the conversation is about heat pumps and the percentage of heat that is taken from the ground. The poster's understanding was that 100% of the heat is taken from the ground, but it costs 25% in electrical energy to convert it into usable energy. However, after reading some forums, it was suggested that the ground collector only needs to absorb 3kW of heat energy and the other 1 kW is supplied from electricity. This is supported by the information provided in the link which states that a geothermal heat pump operating at a COP of 3.5 provides 3.5 units of heat for each unit of energy consumed. The conversation also touches on the difficulty of estimating the value of installing a heat pump
  • #1
smjpl
8
0
Hi all,

I am wondering about heat pumps, not necessarily ground source heat pump.

What percentage of heat is taken from the ground?

My understanding was that 100% of the heat is taken from the ground but it costs 25% (if COP of 4) in electrical energy (running the compressor) to convert the heat from low temperature heat into high temperature heat (albeit a smaller amount).

From reading some forums, some people think that if I have a 4kW heat pump and achieve a COP of 4, that the ground collector only needs to absorb 3kW of heat energy and the other 1 kW is supplied from the electricity, i.e. the compressor.

Is this correct?
 
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  • #2
Have you seen this link??
It tells you all you need to know - and agrees with your understading of it. But other factors will determine what sort of value you, personally, will get if you instal it in your home. That is much harder to estimate because it will depend very much on local conditions (wind, air and soil temperatures and soil type etc.).
 
  • #3
Cheers for the reply. It answered my question but it appears I am wrong.

http://en.wikipedia.org/wiki/Coefficient_of_performance

"A geothermal heat pump operating at 3.5 provides 3.5 units of heat for each unit of energy consumed (i.e. 1 kWh consumed would provide 3.5 kWh of output heat). The output heat comes from both the heat source and 1 kWh of input energy, so the heat-source is cooled by 2.5 kWh, not 3.5 kWh."
 
  • #4
You seem to be right to me. The heat source heat plus the electrical input appear as heat in your house. Isn't that what you are both saying?
 
  • #5
sophiecentaur said:
You seem to be right to me. The heat source heat plus the electrical input appear as heat in your house. Isn't that what you are both saying?

No, I was thinking 100% of heat comes from ground but it costs you 25% in electrical energy to convert it into usable energy. I thought the conversion process didn't add any additional heat but it does.

i.e. if you had a 4 kW heat pump, you would cool the ground by 4 kW not 3 kW.

But just to clarify for anyone else, it does only cool the ground by 3 kW granted you have a COP of 4.
 
  • #6
Yep - and that's how I read what you wrote. :smile:
 

Related to GSHP - What percentage of heat energy is taken from the ground?

1. What is a GSHP system?

A GSHP (ground source heat pump) system is a type of heating and cooling system that uses the natural heat energy stored in the ground to regulate the temperature inside a building. It works by circulating a fluid, usually a mixture of water and antifreeze, through pipes buried in the ground. The fluid absorbs heat from the ground, which is then transferred indoors to provide heating, or removed from indoors to provide cooling.

2. How does a GSHP system extract heat energy from the ground?

A GSHP system uses a heat exchanger, which is typically a loop of pipes buried in the ground, to extract heat energy from the ground. The fluid circulating through the pipes absorbs heat from the ground and carries it into the building where it is used for heating. The fluid is then circulated back into the ground to absorb more heat and continue the process.

3. What percentage of heat energy is taken from the ground?

The percentage of heat energy taken from the ground varies depending on factors such as the size of the system, the type of ground, and the climate. However, on average, a GSHP system can extract about 50-70% of its heat energy from the ground. This means that for every unit of electricity used to power the system, it can produce 2-3 units of heat energy.

4. Are there any environmental benefits to using a GSHP system?

Yes, there are several environmental benefits to using a GSHP system. They use renewable energy from the ground, which reduces the need for fossil fuels and lowers greenhouse gas emissions. They also have a longer lifespan compared to traditional heating and cooling systems, reducing the need for frequent replacements and disposal of old systems. Additionally, GSHP systems operate quietly and do not produce any on-site emissions, making them environmentally friendly and sustainable.

5. What are the maintenance requirements for a GSHP system?

GSHP systems require minimal maintenance compared to traditional heating and cooling systems. The ground loop pipes are usually designed to last for decades, and the heat pump unit typically has a lifespan of 15-20 years. Routine maintenance may include checking and cleaning the filters, inspecting the system for any leaks, and ensuring the heat pump is operating efficiently. It is recommended to have a professional check the system every 1-2 years to ensure optimal performance and longevity.

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