We are all hindered by unintended consequences, Sweden one might argue a global leader for harvesting leftover heat was hamstrung by the law which prevented other suppliers accessing the district heating grid, but that changed when a law was passed last year that allows outside suppliers to deliver heat through the district heating grid. Now the town of Kiruna in northern Sweden can use waste heat from their local industry to cheaply heat homes, a neat solution when the mercury hits -30 Deg C in winter. Details are scare in the Guardian article  however using waste heat whether from industry or power generation are cost effective when the distance (which equates to heat lost) between the source and end-user is not great. Less commonly known is that waste heat can be used in the tropics to drive cooling. Low grade waste heat energy, often dumped in rivers or the sea, can be used to change concentration of liquids with salt, e.g. lithium bromide causing cooling, which in turn maybe used to create chilled water for comfort cooling.
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