Parabolic trough freeze protection

Hello,

SAM's solar field freeze protection method assumes that the HTF flow through the field at night is recirculating: The HTF flows from the field outlet directly to the field inlet. SAM calculates the energy required at the inlet to maintain the HTF temperature at or above the freeze protection temperature value that you specify on the Solar Field page, and reports the energy value as the field freeze protection energy in the hourly results:

"Freeze protection energy" - Energy required to keep field HTF above the freeze point temperature

SAM also reports these two related values:

"Tank freeze protection energy" - Energy required to keep tank above the freeze point temperature
"Auxiliary heater fuel consumption" - Fuel (energy) used by fossil backup

In SAM, heating for freeze protection is assumed to be from electricity. The auxiliary heater fuel consumption and parasitic load are associated with the fossil fill backup system, which provides heat to the power block to supplement solar energy.

The time convention of the simulation depends on the time convention in the weather file. For the standard weather files (TMY2, TMY3, EPW), the first hour is the hour ending at 1 am on Monday, January 1.

Thanks for the Beta feedback suggestion. I will recommend that the two "HX approach temp" inputs on the Thermal Storage page be disabled when the heat exchange derate factor is 1.

Best regards,
Paul.

Hello Paul,

Is there a document, which shows how the freeze protection energy is calculated.? I mean the formula and the factors considered.
Please let me know.

Yes. Please see my reply to the following post for the references:

Freeze Protection Energy Increase with New Version

Best regards,
Paul.

Hi Paul,

I was modeling a 50 MW PT plant with Hitec Solar Salt, and in the Heat loss Diagram, I found that the energy to the power block is more than the energy from the solar field.

How could this be possible.? Kindly let me know. Thanks

In any given hour, the energy to the power block would be greater than the energy from the solar field if:

1. The thermal energy system is delivering energy to the power block.

2. The backup boiler is delivering energy to the power block.

The timing of energy delivery from the storage and backup boiler systems depends on the "Thermal Storage Dispatch Control" parameters on the Thermal Storage page.

Best regards,
Paul.

Yes, That is understood. I am refering to the Heat Loss Diagram added to the Beta Version.
In that the net energy from solar field is less than the energy to the power block.

Could that be true.? Should't the net energy from solar field be larger than the energy given to power block over a year.?