Wednesday, August 8, 2012


This post was initially written to provide background information for this article on the potential benefits of moving air conditioners to off peak power. (published by RenewEconomy on 21 Sept 2012) The article argues that that gradually moving air conditioners to off peak would allow most of the proposed power system upgrades to be deferred for a long time.  The use of phase change materials (PCMs) to store cold or heat would allow this conversion to be done without reducing people's comfort levels.

PCMs are finding a markets as a compact way of storing heat or cold.  This post provides background information on the characteristics and uses of PCMs.  

Phase:  Many materials can exist in more than one phase.  For example, water can exist in the solid, liquid or gas phase.  Some materials can also exist as different crystal phases.
Phase change: The change from one phase to another.  For example, the melting of ice to liquid water.  Phase changes can be driven by changes in temperature and/or pressure.
Phase change material (PCM): A mixture or pure substance that can change phase.  The term is often restricted to materials that change phase over a narrow temperature range.