TES Packed Bed

Hi, all. I would appreciate your help.In previous version, we could review the "help" touching the parameter that we want to know (it helps me a lot for simulating a TES - Two Tanks). But in the new version, i didn't find it anything similar. 

I have some doubts according to simulate a Packed Bed (new version of SAM), in the Thermal Storage section:
1. I'm comparing the Two tanks (version 2023.12.17) vs Packed Bed (version 2024. 12.12) for an "Industrial Process Heat – Parabolic Trough – LCOH Calculator" and it seems had 1 pairs of tanks. Getting the same results in both cases. Someone knows how to simulate a Packed bed case with one tank (where could modify this parameter)? Also, I would to know how the packed bed does the discharge keeping the behavior of a thermocline and in the results where I could find it?
2. The discharge temperature max in hot (decrease) & cold (increase). I would like to know what do they refer to these parameters? Somebody have done this before?Thanks in advanceGreetings

Hi Mercedes,

We are in the process of revising the Help topic for the parabolic trough Thermal Energy Storage input page. The revised version will be available in the next update to SAM.

In the meantime, here is are draft descriptions of the packed bed parameters

The packed bed storage technology consists of a tank filled with a packed bed of solid media (e.g. rocks, spheres, etc.) that stores thermal energy passed via an HTF. When charging, hot HTF enters the tank and heats the solids closest to the inlet. As the solids heat, the thermal gradient travels down the tank. The HTF exits the tank on the other end at a low temperature. During discharge, cold HTF enters the opposite side of the tank and exits at a high temperature. This process moves the thermal gradient up the tank.

The tank model is subdivided spatially along the thermal gradient. The solid media and HTF are assumed to have equal temperatures in each subsection. The SAM timestep is divided into subtimesteps. This one-temperature model is based on the work of Vortmeyer and Schaefer.

Vortmeyer, D., and R. J. Schaefer. “Equivalence of One- and Two-Phase Models for Heat Transfer Processes in Packed Beds: One Dimensional Theory.” Chemical Engineering Science 29, no. 2 (February 1, 1974): 485–91. doi.org/10.1016/0009-2509(74)80059-X .

Packed Bed TES Parameters

Number of spatial sections
Number of subsections the model divides the thermal gradient into.

Max decrease in hot discharge temp, ºC
The maximum allowable decrease in temperature on the hot side of the packed bed tank when discharging. Determines how much energy in the TES can be discharged while maintaining the shape of the thermocline.

Max increase in cold charge temp, ºC
The maximum allowable increase in temperature on the cold side of the packed bed tank when charging. Determines how much energy the TES can charge while maintaining the shape of the thermocline.

Min charge temp, ºC
The minimum allowable HTF inlet temperature when charging the tank. Helps maintain the thermocline shape and prevents the controller from charging the TES with low temperature heat.

Void fraction
The fraction of space in the tank that is not solid media.

Volume oversize factor
Factor to increase the size of tank volume to account for thermocline shape. The volume is calculated based on design power and storage duration but does not account for shape of the thermocline.

Solid media density, kg/m3
The density of the packed bed solid media

Solid media specific heat, kJ/kg K
The specific heat of the packed bed solid media.

Effective conductivity, W/m K
The effective conductivity of the packed bed, which considers conductivity of the solid media and HTF.


Best regards,
Paul.