CSP Thermal energy storage

Hi,

I am simulating Linear Fresnel Reflector, and found that the sum of the hourly thermal energy into TES (MWt) is negative over the year!!

1. Even if I use 16 hours of TES. Why is the sum of hourly values (-)? or what does that explain?

2. Even if I set the storage dispatch control w/ & w/o solar to 1, it gives very low thermal energy to storage and it is still dispatching at one hour per day!

I attached a copy of thermal storage input values & the results.

Thank you,

Hi Ahmed,

In each time step, when the value of "TES thermal energy into storage" is negative, it means that the TES is discharging power in that time step.

It might be helpful to use the time series graph to see how SAM is operating the plant. You can plot "Field thermal power produced" and "TES thermal energy into storage" to see the TES charging during the day and discharging at night. For example:



Best regards,
Paul.

Dear Paul,

Thank you for your reply and explanation.

My only confusion now is that the sum of all " hourly thermal energy into TES " values is negative!
How is it possible that thermal discharge energy more than the charge? And it is increasing with the increase of TES size!
Where does the exceeded values come from? 

Many thanks for your always support,
Ahmed 

Hi Ahmed,

The molten salt linear Fresnel model uses an older algorithm to solve for energy and mass flow and for plant control that performs poorly under certain conditions, especially during time steps when the solar field, thermal energy storage, and power cycle are all operating. This causes the error you found: On a total annual basis, it is quite small, on the order of 1%.

The molten salt power tower, physical trough, and standalone thermal energy storage models use a newer algorithm, so do not have this problem.

We hope to update the algorithm for the molten salt linear Fresnel model, perhaps in 2023, but are not sure if funding will be available for that work.

Best regards,
Paul.