Borehole field

Pick how the tool places boreholes. A standard shape is fastest. "Fill my property line" searches for a layout inside a boundary you draw on the map.

Ground properties

Use values from a thermal response test (TRT) at the site when you have one. Each value needs a source.

Borehole

Pipe (U-tube)

HDPE pipe. Leave outer and inner diameter blank to use the engine's SDR table for the nominal size.

Circulating fluid

Loads

Ground load is heat moved at the borehole wall. Positive = heat into the ground (cooling season). Negative = heat taken from the ground (heating season).

Hourly file (8,760 rows per year)

CSV with a header row, or a Modelica .mos table. One year (8,760 rows) repeats for every design year. A file with at least as many years as the design period is used as given.

Heat pump efficiency (COP)

Used to turn building loads into ground loads: into ground = cooling x (1 + 1/COP cooling); out of ground = heating x (1 - 1/COP heating).

Monthly table

Load check

Summary of the loads the engine will get, one year.

What to find

Limits and period

Entering fluid temperature (EFT) is the fluid temperature that returns from the borefield to the heat pumps.

Entering fluid temperature, hourly

About Borefield Studio

Borefield Studio sizes and simulates vertical closed-loop borefields of about 50 to 1,000 boreholes. It is an engineering screening tool from Gaiergy Corp. A qualified engineer must review the inputs and the results before anyone uses them for design, permits, bids or construction.

All calculations run in your browser. The first time, the page loads Python (Pyodide, from cdn.jsdelivr.net) and the engine packages (from PyPI). This takes about 5 to 15 seconds on a normal connection. Your project inputs stay in this browser: the page does not send them to a server. The map loads its tiles from Esri and OpenStreetMap.

The desktop version adds the full hourly CSV export (every hour of the design period) and the slow "similarities" g-function reference method. This web copy exports a sampled CSV (lowest and highest EFT per bin) and saves and opens project files.

Method

• Ground response (g-function): pygfunction, equivalent-borehole method (Prieto and Cimmino 2021), mixed inlet fluid temperature boundary condition, 8 unequal segments per borehole. Short times use the 1-D radial borehole model of Xu and Spitler (2006), spliced to the long-time curve.
• Borehole resistance: multipole method (Claesson and Hellström 2011) and the effective resistance Rb* of Cimmino (2019), both through pygfunction. Fluid properties from SecondaryCoolantProps. You can enter a measured Rb instead.
• Temperatures: the hourly ground load is superposed on the g-function for every hour of the design period (default 20 years). The tool reports the entering fluid temperature (EFT) to the heat pumps and checks the coldest fluid in the loop against its freezing point every hour.
• Sizing: "Find the depth" searches the borehole depth until the controlling EFT limit is just met (false position root search, tolerance 0.01 °C, as in GLHEPro per Cullin 2008). "Find the number of boreholes" uses the GHEDesigner field search inside your property line, less a setback, then sizes that layout with this engine.
• Monthly load tables are turned into hourly loads, with one heating and one cooling peak pulse at the end of each month, as GLHEPro does.

Accuracy limits

• Against a detailed Modelica Buildings borefield model (300 boreholes, 20 years), the lowest EFT from this tool is about 1.4 °F (0.8 K) too warm and the highest EFT up to 2.7 °F (1.5 K) too cool. The accuracy margin (on by default) tightens the EFT limits by these amounts before sizing.
• On the published GLHEPro version 3 example for Ottawa (Spitler 2000), GLHEPro sized the borehole about 6.4% deeper than this engine.
• Monthly load tables with short peaks can give a lowest EFT up to 4.3 °F milder than hourly loads (300-borehole reference load). Use hourly loads when you have them.
• The hybrid method can differ from the hourly method by -6% to +13% in depth. The hourly method is the default.
• Sources: Gaiergy validation runs of this engine, September 2026. Spitler, J.D. (2000), GLHEPRO: a design tool for commercial building ground loop heat exchangers. Cullin, J.R. (2008), MS thesis, Oklahoma State University.

Open-source credits

Borefield Studio uses these open-source projects under their licenses. The authors and copyright holders of these projects do not endorse Borefield Studio or Gaiergy Corp.

Library versions and licenses as published on cdn.jsdelivr.net and PyPI, checked 2026-09-26. The license texts are at each project's link.