Welcome to the eighth part of the course ‘Design borefields with confidence’.
Summary of part 7
In the seventh part of the course, we left the theory behind and focused more on which methods there are (in GHEtool) to design borefields in practise.
In Part 7.1, the different fluid temperatures (inlet, outlet and average) that can be used to design borefields were discussed. It was said that working with inlet fluid temperatures gives you the safest way to design, since these are always the worst-case temperatures (the coldest during heating and the warmest during cooling).
In Part 7.2, the methodology ‘calculate required borehole depth’ was introduced. By predefining the number of boreholes and their positions, the algorithm could calculate how deep you should drill in order to stay within your predefined limits. However, when working with high cooling loads and a ground temperature gradient, a gradient error could occur.
In Part 7.3, the method to calculate both the required borefield size and depth was introduced to overcome this gradient error problem. This method can optimise your borefield size (both to minimise the required borefield depth as well as the minimum number of boreholes), given a certain available land area.
In Part 7.4, thermal response tests were discussed. Designing borefields of course depends on knowing the right inputs, and thermal response tests are a way of measuring the ground thermal conductivity, undisturbed ground temperature as well as the effective borehole thermal resistance in situ.
Content of part 8
In this eighth part, the focus will be on the design of bigger geothermal systems like multi-utility buildings, whole neighbourhoods and apartment buildings, since these sizes of geothermal projects typically come with some extra questions.
In the first chapter, both individual and collective geothermal systems are discussed, together with their advantages and disadvantages.
When there is opted for a fully individual system, with each user having its own geothermal heat pump and borehole, these boreholes interact in the ground. This concept is called interference and is discussed in the second chapter.
In the third chapter, the focus will be on the design challenges for collective systems and the concept of simultaneity in specific. When multiple users are connected to the same borefield, the resulting ground load is not simply the sum of all individual loads, due to this simultaneity.