Enter usable energy
Provide deliverable stored energy in MWhth, not merely nameplate capacity.
Set the output level
Enter the constant thermal load in MWth.
Check system boundaries
Keep stored energy and delivered power either both gross or both net of conversion and auxiliary losses.
Read the runtime
Use hours for planning and minutes for shorter dispatch events; compare the result with the required service window.
Thermal Storage Storage Duration Estimator
The Thermal Storage Storage Duration Estimator estimates how long a thermal storage resource can sustain a constant output using its available energy. It is designed for designers checking how long stored heat or cooling can support a steady thermal load. Duration links the system’s energy rating to the power demand it must serve, which helps distinguish a short-duration high-power resource from a longer-duration one.
Use usable energy after state-of-charge limits, reserve requirements, or inaccessible thermal inventory. Enter delivered output at the same measurement boundary. The quotient is an ideal steady-output duration; actual runtime can differ because loads change, conversion efficiency varies, auxiliary equipment consumes energy, and control systems may preserve a minimum reserve. For a variable load profile, calculate energy interval by interval rather than relying on one average power value.
Calculator inputs
MWhth
Energy available for delivery after operating limits.
MWth
Constant delivered power assumed during discharge.
Result
—
Estimated storage duration
Duration in minutes—
Equivalent daily coverage—
Energy used each hour—
Storage duration (hours) = Usable stored energy (MWhth) ÷ Delivered output (MWth)
Because one MWth sustained for one hour equals one MWhth, the units reduce directly to hours. The formula assumes constant output and that usable energy already reflects operating limits and any losses applied before the selected boundary.
What the result means
The result is the continuous runtime available at the entered output. Reducing output extends duration; increasing output shortens it.
Confirm that the equipment can sustain the entered power throughout discharge. Energy capacity alone does not guarantee the required output rating.
Given
A thermal store offers 96 MWhth of usable energy while serving a 16 MWth process load.
Calculation
Duration = 96 MWhth ÷ 16 MWth = 6 hours. In minutes, 6 × 60 = 360 minutes.
Result
The system can sustain the stated output for about 6 hours under the constant-output assumption.
Should I enter nominal or usable energy?
Use usable energy available at the chosen delivery boundary. If you enter nominal capacity, first reduce it for operating limits and applicable losses.
What happens if the load changes over time?
This constant-power estimate will not capture the exact runtime. Sum each interval’s energy demand or use a load profile for a more detailed calculation.
Does a longer duration mean a more powerful system?
No. Duration is energy divided by power. A system can have long duration but a modest output rating.
Why must output be greater than zero?
Duration would be undefined at zero output because no stored energy is being consumed. Enter the actual planned load or dispatch level.
Are MWhth and MWth compatible units?
Yes. One MWth maintained for one hour is one MWhth. Convert kW/kWh or other units to a consistent scale before entering values.