Question
In a solor heating application, heat enery is stored in somemedium until it is needed to heat a home at night, Should thismedium have a high or low specific heat? Suggest a substance that would be appropriete for use as aheat-storage medium and explain its advantages. In a solor heating application, heat enery is stored in somemedium until it is needed to heat a home at night, Should thismedium have a high or low specific heat? Suggest a substance that would be appropriete for use as aheat-storage medium and explain its advantages.
Explanation / Answer
I've actually done some solar heating installation/sizingprojects at a previous employer and I think I can help out withthis question. You would want a medium that has a high specific heat. This means that it will take a lot of energy to raise thetemperature of the medium during the day, but also means that itwill have that much more stored energy at night and depending uponhow fast you draw the energy out, will be able to provide moreenergy to your system for a longer period. The one medium that has the highest specific heat of anymaterial is water. This is the medium that we always used inmy projects. You would have a large storage tank of water(typically water mixed with an antifreeze material so that itwouldn't boil during the summer or freeze in the winter if not inuse) and during the day you would continually circulate the waterthrough the solar panels to absorb as much energy as you could(i.e. raise the temperature). Then at night you would bypassthe flow through the solar panels and just circulate the water fromthe now hot storage tank throughout your system. Since water can absorb large amounts of energy withoutchanging state, can hold that energy in for a relatively longperiod (does not radiate the heat away quickly like ametal) and can resupply that energy back into a systemrelatively easily (it can be circulated around) it would be thebest medium to use.