If you're involved in a sizeable building construction project and are responsible for the decision-making process, you will be looking at various alternatives when it comes to providing heating and cooling solutions. As such, you may be keen to make this building as sustainable as possible and will be looking for options to help reduce the size of its carbon footprint. Conventional conditioning systems may not represent an ideal choice in helping you to meet these objectives, and you may be looking at ground-source heat pumps instead. After all, these options do focus on an interaction between the building and the ground beneath, but how do you know if the soil below is actually suitable?
Understanding the Method
For a ground-source heat pump system to work properly, heat will need to be transferred between the soil and the building through a network of pipes that are buried within the ground. For best effect, these pipes should be cast into the foundations of the building, which will help to reduce construction costs and eliminate the need for further work. In doing so, these foundations take on thermal properties, but they will only work effectively if the heat transfer process is sufficient.
Gathering Data
In order to test for functionality, engineers will use a thermal conductivity soil test to analyse the soil. While it is possible to test these samples on site, they may also be analysed in a laboratory setting using a number of different methods.
Laboratory Methods
Steady-state methods will apply a heat flow in one direction to a sample and will measure the temperature difference when the ideal state is reached. The engineers will then be able to determine its thermal conductivity using various algorithms. Alternatively, they may use a transient method, which will similarly apply heat to the specimen, but will monitor the temperature changes over a period of time.
On-Site Testing
If testing takes place on site instead, a probe is inserted into a trial pit and left for several minutes so that it can calibrate with the soil temperature. Once it is determined that the temperature has stabilised, a small voltage is applied to the probe to create a constant heat source, and this flows into the surrounding soil. This temperature will gradually increase as it propagates into the surrounding soil, and this data is analysed to provide the ultimate value of the soil from a thermal conductivity perspective.
Use of Data
This information is crucial to help contractors design the network of underground heat exchange pipes so that they can accurately meet the heating loads expected of their building.