Its integration with vapor absorption system is planned. There is already a sensible thermal energy storage using water. I don't wish to use any heat-exchanger either.
I would recommend the following PCM types for the application that you cited:
1) Paraffins.
2) Metal alloys.
3) Molten salts.
Hope this helps answer your question and good luck!
Storage for what? What do you intend to use this low level heat for? There are lots of low level heat sources like this around refineries and the value is usually negative. Cooling is usually done with air fin coolers and the heat is rejected to the atmosphere.
Some installation have used this heat to preheat combustion air but the cost is not justified by the economic benefit - a significant carbon tax could change the economics.
I thank Prof. Manner, Prof. Khalil and Prof. Edwin for their valuable comments.