Console & dashboard

The console gathers the design-level indicators of the system and the convergence of the simulation. It is organised as four pages, reached with the buttons at the bottom of the panel, which share a footer reporting computation times and solver convergence.[−]

The console doubles as the help viewer: clicking the help button of any panel replaces the results with the help page of that panel, and clicking one of the page buttons below brings the results back. Selecting a node in the analysis tree changes the panel on the left, not the page shown here: the page you last chose stays until you choose another.

Page 1, demand coverage - Reached with the Demand coverage button. Reports, for cooling and heating separately, two blocks of five rows, each closed by its total: the heat pump output, the geocooling supply, the auxiliary contribution, the domestic hot water made and the uncovered demand — first at the peak hour in kW under Total peak, then over the year in MWh/y under Total energy. The same figures, as percentages, are given on page 3 under Demand coverage ratio.

Each block adds up to its total. The five power rows are read at the same hour, the one at which the building demand, space load plus domestic hot water, is highest; that hour is given as Peak hour on the Thermal loads panel, one per mode. The first four rows are what the system delivers at that hour and the fifth what it does not, so the five add up to the peak demand. The energy block does the same over the year. Total peak and Total energy are the same figures as Total peak and Space energy plus DHW energy on the Thermal loads panel.

Geocooling has its own row in both blocks. When the compressor is bypassed, the cooling is delivered by the borehole field, not by the heat pump. Both rows read — in the heating column, since geocooling does not heat.

Comparison with the load panel. Without domestic hot water, the rows sum to the Space peak of the Thermal loads panel. With hot water (separate load format), they sum to that peak plus the hot water drawn at that hour, and the Domestic hot water row shows how much of it the system makes; any shortfall appears in Uncovered demand.

Hot water at the peak and over the year. In heating, hot water uses the heat pump capacity left over by the space load. At the heating peak there is often none left, so the Domestic hot water row can read 0 kW while the annual total is substantial, the hot water being made during the rest of the year.[−]

The peak hour is the hour of highest building demand, not the hour when the system delivers the most. The two coincide while the demand is covered; once the system is saturated, it delivers its full capacity over many hours.

Three coverage ratios (on page 3). Space coverage counts the heating and cooling load alone; DHW coverage the hot water alone, and reads — where none is requested; Total coverage includes the hot water on both sides of the ratio. When they differ, the difference is hot water the system does not make: DHW coverage gives it as a percentage and Uncovered (MWh/y) on page 1 in energy.

On a geocooling design no hot water is made during geocooling hours, since the compressor is bypassed: Space coverage can read 100 % while Total coverage reads much less. The borehole field is not at fault; the hot water must then come from an auxiliary water heater.

Page 2, energy consumption - Reached with the Energy usage button. Reports the total system peak power demand (kW) and the mean annual electricity consumption (MWh/y) for each component — heat pump, auxiliary equipment, domestic hot water, and circulation pumps — together with the combined system total. Use this page to assess the electrical load profile and evaluate pump energy relative to compressor energy.

Hot water has its own line. The space COP varies hour by hour with the entering fluid temperature and the part load, whereas hot water is computed with the fixed DHW COP of the Heat pump performance panel. In cooling, the water is heated with condenser heat that would otherwise be rejected to the ground, so its COP can be an order of magnitude above the space COP.

The energy lines add up; the power lines do not. Each kW cell is the maximum drawn by that component, and the four maxima occur at different hours: the compressors peak with the building, the pumps run steadily, the auxiliary equipment only at the extremes. Only the Total line is a simultaneous maximum, read on the whole system.

Page 3, system efficiency - Reached with the Energy efficiency button. Reports the seasonal COP of the complete system (sCOP), the seasonal COP of the heat pumps on the space load, the seasonal COP of the domestic hot water they make, and the reduction in peak electrical demand obtained against a resistive reference (%). Below them, the Demand coverage ratio block states as percentages what page 1 states in kilowatts and megawatt-hours: the share of the peak that is served, then the share of the annual demand — for the space load, for the hot water, and for the two together.[−]

All three coefficients are ratios of energies over the whole horizon, the heat delivered divided by the electricity used, not averages of hourly COPs; each hour is thus weighted by its consumption, as on a utility bill. The system sCOP includes the auxiliary equipment and the circulation pumps, the heat pump sCOP counts the compressors on the space load alone, and the hot water sCOP the same compressors on the water they heat. A wide gap between the first two usually points to the circulation pumps, detailed on page 2.

[−] The heat pump and hot water lines read --- when nothing ran: a geocooling system draws no compressor electricity in cooling, and the hot water line is blank when no hot water was produced. The hot water sCOP reads ∞ when the cooling DHW COP is set to ∞, the water then costing no electricity.

Peak demand reduction is a heating figure. The reference is an all-electric resistive installation (COP of 1), which draws at its worst hour the peak thermal demand of the building. The line gives the reduction of peak electrical demand obtained by the ground-source system, auxiliary equipment and circulation pumps included, as a percentage of that reference. Both terms are maxima over the whole horizon, each taken at its own hour, as a demand charge is billed.

The cooling column reads —, since a resistive element cannot cool.

A negative value means the system draws more peak power than a resistance would, which happens when a short field pushes the load onto the auxiliary equipment and the pumps; revisit the field length and the pump sizing.

Read this figure together with Uncovered demand on page 1: the resistive reference covers the whole demand, whereas a saturated ground-source system delivers less. When Uncovered demand is not zero, the reduction is overstated by roughly the power of that shortfall.

Page 4, ground response and validity - Reached with the Ground response & validity button. This page reports the response of the ground and whether the simulation stayed within the validity range of its models, in three blocks.

Ground evolution. First what was put into the ground: the mean annual energy exchanged with it (MWh/y), and its long-term thermal balance — cooling energy minus heating energy, MWh/y. Then what the ground did about it: the maximum and minimum EFT reached over the full simulation horizon (°C), the long-term EFT drift (ΔT, °C/y), and the temperature at the centre of the field — its perturbation ΔT(0,0) and its absolute value T(0,0), in °C. A non-zero balance means the field is loaded unevenly over the year, and the drift shows the consequence: a notable drift signals a field whose performance will change over its design life.

The two extremes are taken over every hour of the horizon, whatever the operating mode; a project that only heats therefore still reports the warmest temperature reached by the loop. Both read — until a simulation has run.

Temperature limits. The number of hours per year during which the EFT crossed the heat pump temperature limits set on the Heat pump performance panel. A design that respects its limits reports zero here; a handful of hours a year is usually a peak to be accepted knowingly, and a few hundred is a sizing decision to revisit.

Validity envelope. The peak ground load carried by the boreholes (W/m, cooling and heating), which a correctly sized field keeps within roughly 30 to 70 W/m, and the number of hours per year during which the EFT left the range over which the borehole resistance and heat pump correlations are defined. Outside that range the resistance, COP and capacity are held at the end of their curve: the simulation still converges, but a value other than zero means part of the horizon was computed at the limit of the model.

Computation time and convergence - The footer shared by every page reports the wall-clock time of each stage: the effective borehole resistance (R_b^*), the GHE transfer function (g-function), the entering fluid temperature (EFT) and the time required to display the results. Most of the time, the display of the graphs is the most time-consuming operation.

A stage that did not run reads —: editing a building load, for instance, recomputes the fluid temperature but neither the borehole resistance nor the g-function. Total is the sum of the stages that did run.

To ensure the integration of the COP(EFT), CAP(EFT) and R_b^*(EFT) curves, GHE Analysis uses a robust iterative process to reduce the numerical error associated with the ground loads (ɛ_Q) and EFT (ɛ_T). The elements influencing convergence are a COP(EFT) and CAP(EFT) curve with abrupt changes in slope, a high R_b^*, and a circulation flow located in the transitional zone.

If the residuals (ɛ_Q, ɛ_T) fail to settle, the usual remedies are to smooth a heat-pump performance curve that changes slope too abruptly, to add boreholes or length where the fluid temperature swings are extreme, or to keep the circulation flow clear of the laminar-to-turbulent transition. Only a converged solution, shown in green, gives reliable energy, efficiency and peak figures.

Dashboard donut diagram - To allow an interactive design of the system, most of the numerical values displayed on the console are graphically illustrated on the donut diagram located in the dashboard. By clicking on a piece of the diagram, it is possible to highlight a particular indicator. Progressing from the outside to the inside of the diagram, the rings contain respectively the demand coverage, energy coverage, power demand and energy consumption. Starting from noon and moving counter-clockwise, the first three pieces of each ring correspond to cooling and the last three correspond to heating.

GHE in practice: reporting what the console shows

A design report is most useful to whoever reviews it when it states the conditions alongside the result. Beside the borehole length retained, record the peak and annual coverage of both modes, the seasonal COP, the extreme EFT reached over the horizon and the long-term drift, and the share of the electricity that goes to the circulation pumps rather than to the compressors. Those five figures are on the pages above, and together they let a reviewer decide whether the design is defensible without reopening the model.

Check the convergence first. A simulation that has not converged can still fill the pages with plausible values; fix it before reporting any figure.

Report the drift. A long-term EFT drift on page 4 says the field is thermally imbalanced and that its performance will move over the design life. Where it appears, state the drift in the report with the horizon it was computed over, and say what was done about it: a change on the building side, added length, or a deliberate acceptance of the drift.