Field Optical Focus Fraction

Hello,

I'm doing my dissertation about a CSP Power Tower plant (100 MWe, 8 hours TES), but to characterize losses produced by defocusing, I need to know what is "Field Optical Focus Fraction". Is the defocused area fraction?

Secondly, I have a question: the field optical efficiency is affected by "field optical focus fraction"?

How can I know the losses produced by defocusing?

Best regards,

Manuel.

Dear Paul,

Thanks for your prompt response.
I have one more question. Is related by thermic balance in the plant. In order of appearance, we have:

DNI*effective_Area_heliostats

- Optical Loss
- Defocusing Loss (calculated by "field optical focus fraction")
- Heliostat Availability Loss

= Receiver Thermal Power Absorbed

- Receiver Thermal Power Losses to convection and radiation
- TES Thermal Losses from tanks

= Cycle thermal power input
.
.
.

However, "DNI*effective_Area_heliostats - (Optical Losses + Defocusing Losses + Heliostat Availability Losses)" is not equal to "Receiver Thermal Power Absorbed"

Receiver Thermal Power Absorbed must be equal to "DNI*effective_Area_heliostats - (Optical Losses + Defocusing Losses + Heliostat Availability Losses)".

Is there another loss that SAM is not reporting?


PS: I have calculated "Defocusing Loss":
(1 - field optical focus fraction)*DNI*effective_Area_heliostats*heliostat availability


Best regards,

Manuel.

Dear Paul,

Do you have an explanation?
Thanks.

Best regards,

Manuel.

I'm having a huge issue with my model. The output Electricity spikes and whenever it does that there is a lowered optical fraction (lower than 1). Does anyone know what reason there could be for this?