When simulating a BTES system in Hysopt, the user should first load match it with this template, which is based on a TRT (Thermal Respons Test). The correct way to load match is with an already executed TRT. More information about a TRT can be found in BTES 1.0 or BTES 1.4.
A TRT and this template have the following principle. A mixing circuit is used to make sure the temperature difference between the ingoing and outgoing temperature of the probe is constant (in this case 4 K, the user should change the constant value depending on the executed TRT). A constant volume flow is delivered by the pump, which results in a rather constant thermal power injected into the soil.
The following results come from a TRT and should be inserted in the BTES-BC:
Average thermal power injected [W] → Cold deposit power
Undisturbed (natural) soil temperature [°C] → Natural soil temperature
In a TRT the borehole resistance is also typically given and should be recalculated to the heat transfer coefficient of the borehole heat exchanger as follows.
UA-value borehole [W/K] = depth borehole [m] / borehole resistance [m.K/W]
The calculated borehole UA-value should also be implemented and locked by the user.
If the pressure drop is also given from the test, the KV value can be calculated by clicking on the pencil icon visualised above. After clicking on the pencil icon, a popup window appears. In this popup window, the user can calculate the KV value by entering the pressure drop and the volume flow rate (which is also given by the TRT).
The remaining parameters needed to correctly simulate the BTES system are found by clicking on the pencil icon of the simulation settings.
After clicking on the pencil icon, a popup window appears with remaining simulation settings. More information on these settings can be found in BTES 1.0 or BTES 1.4.
The soil capacitance, the soil start temperature and the thermal loss coefficient should be load matched with the given trend function from the TRT. In the graph below an example of a trend function (red) is visualised and compared to the measured soil temperature (blue).
The BTES system should be load matched with the trend function using the remaining 3 parameters. To easily load match it, the user should first export the .csv file from the “data file”-BC in the template.
To export the .csv file, the user should click on the pencil icon visualised above. After clicking on it, a popup window appears with the possibility to export or import the .csv file.
The user should click on the middle icon with the arrow pointing down in the cloud to export the file. After exporting, the values in the file should be changed with data calculated from the trend function. The trend function starts with a time of 0h, however, the data for the first 12h shouldn’t be used because at this point the behaviour isn’t stationary yet. After changing the data, the user should import it into the software by clicking on the right icon with the arrow pointing up in the cloud and uploading the file.
After the user has successfully imported the data file, the user can compare the simulated soil temperature (green) and the temperature generated from the trend function (red) in 1 graph by plotting them together. In the graph below the BTES system is successfully load matched with the trend function. The load matching should be done by changing the 3 parameters, spoken of earlier.
However, for a TRT only 1 probe is used to do the test. In a real installation, more probes are typically used wich means these parameters should be scaled accordingly. The way to scale them isn’t always linear. The parameters that should be scaled linearly are:
Cold deposit power
UA-value borehole heat exchanger
The natural soil temperature stays the same, the
To quickly use and simulate a complete BTES system in Hysopt, different templates are available in our Inspiration Library and explained in BTES 1.0 templates and BTES 1.4 templates.