Ground Source Heat Pump efficiency: Solar Panels

With the increased use of solar panels, ground source heat pumps, and other more environmentally responsible energy solutions, it is no surprise that we are all looking to get the most out of the new technologies we are embracing. One way in which this can be achieved is to use solar panels to improve ground … Read more

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With the increased use of solar panels, ground source heat pumps, and other more environmentally responsible energy solutions, it is no surprise that we are all looking to get the most out of the new technologies we are embracing. One way in which this can be achieved is to use solar panels to improve ground source heat pump efficiency. This is achieved by storing the excess energy output produced by the solar panels in the summer within the ground, and then using the ground source heat pump to extract that heat when it is needed in the wintertime. Systems such as these are commonly referred to as ‘inter-seasonal’.

Inter-Seasonal systems: Improving Ground Source Heat Pump efficiency

An inter-seasonal system for improving ground source heat pump efficiency can be:

  • a passive or low-temperature system which relies on highly insulated properties which are specifically designed to use heat energy which has been stored naturally in the surrounding grounds to heat the property within them.
  • a warm temperature active system which operate using systems such as solar thermal panels to get the maximum amount of energy possible from the sun and store this in the ground in time for when it is needed in the winter.
  • a high temperate active system which uses solar panels to harvest energy but keeps the energy stored in highly insulated storage devices as opposed to in the surrounding grounds. These systems are capable of storing much greater temperatures.

The most common type of system available on the market at the moment is of the warm temperature active variety. These systems can be very effective in harnessing all of the energy your solar panels produce, but a few variables do exist which may impact upon the panels’ effectiveness:

  1. The ground’s conductivity will determine the speed at which energy is able to move within the ground itself. Where the ground’s conductivity is high, energy is able to more easily move away from the area and to be lost.
  2. The ground’s moisture content can increase conductivity even further, causing a greater chance of the energy being leaked and lost to the surrounding area.
  3. The type of ground array used will affect performance. An array with a smaller ground surface footprint will be less affected by the seasonal climate changes throughout the year. A series of shorter boreholes located in close proximity are much better at storing energy but their performance can be compromised when heat is extracted.
  4. The number of solar panels you use solely to supply energy to the ground rather than to provide domestic hot water (DHW).

The normal ambient ground conditions will not normally be raised by a warm temperature active system because the heat deposited by the system does not ordinarily remain within the ground collector area. A system of boreholes will usually retain the deposited heat for much longer than horizontal systems.

Normally a warm temperature active system is designed to help the ground to recover its original temperature more quickly. A properly sized ground array should allow the ground to return to its original temperature in time for the beginning of the next heating season (during the wintertime) without using solar recharging.

Using Solar Panels to improve Ground Source Heat Pump efficiency

Where solar panels can be useful in recharging the ground to temperature is during the  early springtime and autumn. At these times of the year, energy is deposited in the ground whilst the sun is shining in the daytime. The energy that is deposited is held around the ground array pipes, and so as the sun sets and the heating system is required, this deposited energy from the ground is still held nearby and therefore is absorbed back into the system. This improves the Coefficient of Performance (CoP) and, therefore, the ground source heat pump efficiency.

Is this suitable for my home?

In a domestic setting, this kind of set up is not currently very useful. This is because the amount of energy which is deposited in the ground by the solar panels and then reclaimed by the ground source heat pump is actually quite small. The cost of the equipment needed can be very high, and might in fact outweigh the benefits of installing such a system on your property’s grounds.

Commercial Applications

Using solar panels to improve ground source heat pump efficiency is much more applicable at the moment in commercial settings. Large commercial projects which use a heat pump for cooling and which deposit removed heat into the surrounding ground are much more likely to make good use of such a system. These systems are on boreholes and their cooling rates are relatively high. This means that with some careful design carried out by the system designer, it is possible to reduce the size of the borehole field, making the system overall much more energy efficient.

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