Dispatch Control

Hello!

I've been trying to model my plant so that it won't work during the night. The way I've been working on it is by modifying the dispatch control. For the night hours - when I don't want it working - I've set the turbine out fraction equals to zero.

When I run the simulation, I usually get negative values for the System power generated - what do these negative values mean?

Also, what does negative values for TES Thermal energy into storage mean?

Best,
Jessica Mello

Dear Jessica,

The negative values at night are to account for parasitic loads to operate pumps or electric heat trace equipment for freeze protection.

A negative value for TES thermal energy into storage in a given time step means that the TES is being discharged in that time step.

Best regards,
Paul.

Dear Paul,
I am also getting a negative value for "TES thermal energy into storage" in the "single values" results under "data tables". The value is around -92500 MWht for a system with a TES of around 5000 MWht. Assuming "TES thermal energy into storage" refers to the annual energy balance for the TES, how can this negative value be explained? I would expect it to be zero over one year, or differ from zero by no more than the amount of the TES capacity (in case the TES is empty at the beginning of the year and full at the end or vice versa). Is it due to heat losses from the TES?

Best regards,
Roman

Dear Roman,

The value under "single value" is the sum of the hourly time series values under "hourly" (or it might be listed under 15-minute or similar if you are running subhourly simulations). You might want to investigate the operation of the TES by plotting data on the Time Series tab to understand what the model is doing.

If you want help with that investigation, please feel free to email me a copy of your .sam file by attaching it to an email from the Contact page (see link above).

Best regards,
Paul.