The Energy station solves the system's cycle again across a year of outdoor temperatures, adds up the compressor, fan and defrost energy, and prices it at your tariff. It is a station on every refrigeration project.
- 1
Choose the system in System. Changing it here changes it on every calculation page and in the header.
- 2
Check Town under Location. A project with a location starts on Project location; choose Expected · typical weather or Upper bound · design-high beneath it.
- 3
Enter Electricity rate, Daily runtime and Motor efficiency (0–1).
- 4
Except on a transcritical CO₂ system, set Min condensing temp, the lowest the condensing temperature is allowed to fall in cold weather.
- 5
Check Fans and defrost. When the system has a saved equipment selection, the fan and defrost figures are read from it and can't be typed over here; change them on the Equipment station. Without one, enter Evap fan power, Cond fan power, Defrost power and Defrost hrs/day yourself.
- 6
If the condenser or gas cooler has pads, set Pads to On under Adiabatic pre-cooling.
- 7
Read the results beside the sheet, starting with Annual readings.
- 8
Name the analysis in Analysis name and choose Save analysis.
Where the climate comes from, and why it matters, is in Choose the climate for an energy analysis. What the results mean is in Read the energy results.
What Kelvin works out each month
- The plant carries its design cooling load for every running hour: Daily runtime hours a day, every day of the year.
- On a subcritical system, the condensing temperature is the ambient plus the condensing TD, and never below Min condensing temp. On a transcritical CO₂ system, the gas cooler exit is the ambient plus the design's approach.
- The condensing TD comes from the selected condenser's rating (heat rejection over its kW/K) when the equipment selection has one, otherwise from the design's condensing temperature less its ambient. If the design has neither, Kelvin uses its own default and labels it as a fallback, not a design figure. Calculated from says which.
- Compressor energy is the cycle's shaft power divided by Motor efficiency (0–1).
- Evaporator fans run at constant power. Condenser fans are scaled month by month by the fan affinity law, never above their design power. Gas cooler fans run at constant power.
- Defrost energy is Defrost power × Defrost hrs/day, every day of the year.
- One flat Electricity rate prices every month. Kelvin doesn't model time-of-use tariffs or demand charges.
Saving and what uses it
Save analysis saves it against the system. Saved analyses appear as chips under Saved analyses; choose one to open it with the inputs it was saved with. Once one is open, the button reads Update analysis, and the version it replaces stays in its history.
A saved analysis keeps its own fan and defrost figures, and its own copy of the project location's monthly temperatures, so a later change upstream doesn't move it. BOM & Running Cost takes its annual energy cost from the system's most recently updated analysis.
When there are no figures
- No climate profile: the project has no location, its weather station has no complete set of monthly temperatures, a custom profile is missing a month, or the town isn't a preset. Kelvin assumes no temperatures, so there are no annual figures until you choose a climate. The notice says which is missing.
- Condensing TD is not above zero: the design's condensing temperature isn't above its ambient, or the selected condenser's rating puts it there. Set the condensing temperature above the ambient on Cycle, or check the condenser selection.
- Refrigerant not found: the design's refrigerant couldn't be loaded. On a cascade, the high-stage refrigerant has to be found too, or no month can be solved.
Note
Saving is offered only once the analysis has figures. Until then, the notice beside the sheet says what is stopping it.