Enter geothermal operating data
Use consistent measured values for a steady operating period.
Formula used
The calculation applies sensible heat transfer to the circulating geothermal fluid.
With a heat pump COP above 1, compressor power is calculated as usable source power divided by COP minus 1. Delivered heating is source heat plus compressor input.
How to use this calculator
- Measure the fluid flow rate and select its unit.
- Enter density and specific heat for water or your brine mixture.
- Enter stable source supply and return temperatures.
- Set the operating duration you want to evaluate.
- Use an efficiency allowance for real loop and exchanger losses.
- Enter heating COP above 1 when a heat pump is used.
- Review usable geothermal power, total energy, and heat pump estimates.
Example geothermal operating data
| Input | Example value | Purpose |
|---|---|---|
| Flow rate | 12 L/s | Sets circulating fluid volume. |
| Fluid density | 998 kg/m³ | Converts volume flow into mass flow. |
| Specific heat | 4.186 kJ/kg·K | Represents water heat capacity. |
| Supply and return | 14 °C and 9 °C | Creates a 5 °C temperature difference. |
| Runtime and efficiency | 8 hours and 90% | Estimates practical recovered energy. |
| Heating COP | 4.0 | Estimates delivery and compressor input. |
Understanding Geothermal Heat Energy
Geothermal systems move heat rather than create it. Underground soil, rock, or water holds relatively stable temperatures. A circulating fluid absorbs energy from a warmer source. It releases energy where heating is needed. The heat rate depends on fluid flow and temperature change. Longer operation increases the total recovered energy. This calculator turns those conditions into thermal power and energy values.
Why Flow Rate Matters
Flow rate controls how much fluid passes through the heat exchanger. More flow carries more mass every second. A larger mass flow can transport more heat. However, pumping demand may also rise. Very high flow can add pressure losses. Very low flow can reduce heat exchange. Use measured flow whenever possible. Nominal pump ratings may not match actual field conditions.
The Role of Temperature Difference
Temperature difference is the driver of sensible heat transfer. For heating, compare source supply temperature with return temperature. The calculator uses the absolute difference for energy magnitude. It also reports the flow direction implied by the temperatures. A small difference can still produce useful heat at high flow. A large difference with poor flow may deliver less energy. Record temperatures at stable operating conditions for better estimates.
Fluid Properties and Efficiency
Water is common in closed and open geothermal loops. Brine mixtures need different density and specific heat values. Colder antifreeze mixtures often carry slightly less heat per kilogram. Enter reliable fluid properties when available. The efficiency field represents loop, exchanger, and practical recovery losses. It reduces ideal extracted heat to an expected usable geothermal contribution. It does not replace a full design simulation. Pipe length, ground conductivity, and seasonal recovery still matter.
Heat Pump Interpretation
A heat pump can raise the useful delivery temperature. Its heating coefficient of performance, or COP, relates delivered heat to electricity input. When COP is greater than one, extracted geothermal heat is only part of delivered heating. The calculator estimates compressor electricity and delivered heating using the entered COP. These estimates assume steady conditions. They do not include fans, controls, defrost, or auxiliary heaters.
Using Results in Design Work
Start with measured or proposed operating values. Check that units match the selected flow unit. Review average thermal power for equipment sizing. Review usable energy for a chosen operating period. Compare delivered heat with the building load. Leave a margin for weather, cycling, and ground conditions. Repeat the calculation for winter and summer scenarios. This produces a clearer range than one isolated result. Consult qualified geothermal and mechanical professionals before final equipment selection.
Limits and Good Practice
This estimate uses steady-state sensible heat transfer. It assumes entered flow remains constant during runtime. It cannot measure borehole depletion, groundwater restrictions, mineral scaling, or weather loads. Verify sensor calibration before use. For commercial systems, combine these figures with pressure-drop, pump, load-profile, and long-term ground-response assessments. Good records support more reliable adjustments over time.
Frequently asked questions
1. What does this geothermal heat calculation measure?
It estimates the thermal power transferred by a circulating geothermal fluid and the energy transferred during a selected runtime. It also applies an efficiency allowance for practical heat recovery.
2. Why is density required?
Flow meters often report volume. Density converts that volume flow into mass flow. Mass flow is required because specific heat capacity is expressed per kilogram.
3. Can I use this for water and antifreeze mixtures?
Yes. Enter the density and specific heat values for your actual mixture. Do not use plain-water assumptions for concentrated brine or antifreeze solutions.
4. What does the temperature difference represent?
It represents the change in fluid temperature through the heat exchanger. With flow and fluid properties, that change determines the sensible thermal transfer rate.
5. Why does the calculator use an absolute temperature difference?
The absolute difference gives the heat-transfer magnitude. The result separately identifies whether the temperatures indicate extraction from, or rejection to, the geothermal source.
6. What efficiency should I enter?
Use a conservative allowance for heat exchanger, loop, and operational losses. Measured performance is best. For early estimates, compare several reasonable scenarios instead of relying on one figure.
7. What is heating COP?
Heating COP is delivered heating divided by compressor electricity. A COP above one means the heat pump moves geothermal energy in addition to using electrical input.
8. Does the heat pump estimate include pumps and fans?
No. The COP estimate models compressor input only. Add circulation pumps, fans, controls, and auxiliary heating separately when preparing a complete electrical energy estimate.
9. Can this calculator size boreholes or ground loops?
No. Borehole and loop sizing requires soil data, ground response, climate loads, pipe geometry, operating schedules, and local engineering constraints.
10. Are the results suitable for open-loop systems?
Yes, as a heat-transfer estimate. Confirm local water quality, flow permissions, fouling risk, discharge rules, and well performance before using open-loop designs.
11. How can I improve accuracy?
Use calibrated temperature sensors, measured flow, correct fluid properties, and stable operating periods. Compare several seasons and validate calculated heat against utility or building-load records.