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nPro: Software tools for simulating and designing geothermal borhole fields

On this page, you learn about the software tools available for simulating and designing geothermal probe fields and how these can be used for planning districts with heat networks.

Calculation programs for the design of geothermal probes

Various calculation programs exist for the design of geothermal probes for different application areas. Well-known software tools for the design of geothermal borehole fields are:

GEO-HANDlight allows the calculation of probe length based on various parameters such as ambient air temperature, annual average demand, and monthly maximum demands and peak loads for geothermal probes for heating and cooling purposes. Additionally, it can determine the temperature at the outlet of a heat pump for an existing probe field. The EWS program enables the calculation of supply and return temperatures as well as performances of probes monthly over a period of up to 60 years. It allows the sizing of individual probes and probe fields according to the current standard SIA 384/6. For this, direct cooling can be considered, as well as seasonal storage of heat. All relevant influencing parameters such as probe type, backfill, probe arrangement, load profile, geology, etc. can be configured. Earth Energy Designer (EED) is a numerical simulation program, which optimizes probe depth and drilling distances based on technical boundary conditions. In addition, it can calculate the temperature in the brine. While GEO-HANDlight uses a simplified design procedure developed by Biberach University of Applied Sciences (Prof. Koenigsdorff), the tools EWS and Earth Energy Designer (EED) represent numerical simulation programs. Each of these programs is based on normative guidelines that define specifications for the design of geothermal probes.

In the nPro-Tool, geothermal probe fields can be simulated and designed.

Standards for designing geothermal probe fields: VDI 4640 and SIA 384/6

The standard VDI 4640 provides precise guidelines for the design of geothermal probes and near-surface collectors and includes important standards and procedures. It contains detailed information on probe sizing, probe spacing, and maximum probe load. It also establishes clear criteria for considering soil-specific thermal properties such as thermal conductivity and the volumetric heat capacity of the soil. These parameters play a crucial role in the efficiency and performance of geothermal energy use. The standard serves as a tool for professionals and planners to ensure precise calculation of probe length and other relevant sizing aspects, thereby enabling optimal adaptation of the geothermal system to local conditions. By adhering to these soil-specific thermal properties according to VDI 4640, efficient use of geothermal energy and sustainable design of geothermal probes are ensured. In Switzerland, the standard SIA 384/6 is used for designing geothermal probes, which is similar in content to VDI 4640 but has specific differences. Some of the design methods considered, including GEO-HANDlight and nPro-Tool, are based, on the standards and guidelines of VDI 4640, which provide a basis for the efficient and sustainable sizing of geothermal probes.

Calculation of geothermal probes with nPro

Unlike the programs mentioned above (especially Earth Energy Designer and EWS), which solely enable the simulation of geothermal probes but do not simulate other components of a building or district, the nPro software offers functions for the comprehensive simulation of a building or heat network in a district: Starting with the generation of load profiles for heat, cold, and electricity, through the simulation and design of the heat network (pipe sizing, heat loss calculation according to DIN EN 13941), to the design of the components of an energy center at the building or district level. In the energy center, different heat, cold, and electricity generation technologies, such as heat pumps, combined heat and power plants, boilers, and geothermal probes, can be combined. A techno-economic optimization model allows the design optimization of the components of the energy center taking into account economic and technical boundary conditions. Furthermore, nPro supports the determination of relevant parameters for the design of geothermal probes, such as the temperature at the heat pump outlet, probe length, and number of probes. Detailed information on the geothermal-related calculation functions of nPro can be found in the documentation. Various calculation functions for the design of geothermal probes can be utilized in nPro:

  • Calculation of the number of probes depending on the specified probe length, temperature, and probe distance.
  • Calculation of probe length depending on the probe configuration, probe distance, and temperature at the heat pump outlet.
  • Calculation of the temperature at the heat pump outlet depending on the given probe length, probe distance, and probe configuration.
  • Calculation of temperature profiles at the heat pump outlet depending on the given probe length, probe distance, and probe configuration.

The advantage of using nPro for the design of geothermal probes is that the calculation of probe length and temperature at the heat pump outlet is directly integrated into the simulation of the heat network. This allows to consider the effects of probe length and temperature at the heat pump outlet on the heat and cooling losses in the heat network. nPro thus combines the benefits of several specialized software tools both for the design of geothermal probes and the design of heat networks.

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