TES-FF Complementary?

Hello,

In the Generic CSP model I am trying to create a system that has both Thermal Energy Storage and a Fossil Fuel Back Up system. Ideally the FF system would only operate when there is no direct solar energy and no remaining energy available from storage. However, the Fossil Fuel fraction dictates that the FF system operates whenever there is no direct solar energy, i.e. it does not take into account that there is energy available from storage. The result is that both the TES system and the FF system are simultaneously supplying energy to the power block and the system is generating well over its intended capacity during certain hours.

Do you have any advice re: how this can be addressed so that the TES and FF systems can be complementary rather than independent systems?

Best regards,
Charlie

Dear Charlie,
For the generic CSP model and other CSP models that include fossil backup, the fossil fill fraction input is designed to model a fossil backup system that supplements energy from the field when there are fluctuations in the solar resource. That's why, when you use a high fossil fill fraction at night the fossil backup system supplies more energy that is required to operate the power cycle at its rated capacity. Here are some suggestions for working around that limitation of the model:

• 
  You could prevent SAM from dispatching fossil backup power during the day by defining separate dispatch control periods for night and day, and setting the fossil fill fraction for the daytime period to zero.
• 
  To ensure that the fossil system is not providing too much energy at night, you could run the model iteratively find the fossil fill fraction that results in the power cycle not exceeding its capacity.

Best regards,

Paul.

Dear Paul,

Thank you for the tips. I'll play around with the model to see what I can do. interestingly the system produces as intended during the day. It is during the evening that both the FF and TES systems are operating at 100% that production goes way above capacity. I was hoping I could make it so that the FF system would only fire when the TES system can't meet the load.

Best regards,
Charlie

Dear Charlie,

Now that I think about this more, there may be a problem with fossil fill for the generic CSP model. If you do a similar analysis using the physical trough model, you will see that the power cycle output does not exceed its design point in the way it does for the generic model. I'm working with the model developers to investigate, and will let you know when I find out more.

Best regards,
Paul.

Dear Paul,

That is greatly appreciated! I'll keep checking the forum for an update.

Best regards,
Charlie

Dear Paul,

Just checking to see if you've received any feedback from the model developers?

Best regards,
Charlie