combining a climate battery type system with a wicking bed, suggestions please.

I am building a wicking bed with a cold frame on top. I will insulate the frame and bed to keep the heat it. To collect extra heat in the winter, I wondered if it would be helpful to use a small electric pump to run water from the reservoir through a black plastic pipe looped across the surface of the bed. This should pick up heat from the sun and store it in the gravel/ water, kind of like a climate battery. Remember that this is in Colorado, with intense sun and guaranteed cold frame overheating most days without venting.

What do you think?

The pump could be turned off at night to prevent freezing. I am thinking that this system could be especially useful during March and April, when I would be trying to start new tender plants, and there is a lot of sun around, but nights are still cold.