WATER HEATING THERMAL STORAGE


Figure 3: Example of multivalent thermal store – this store provides indirect, low-volume flow instantaneous hot water or larger volumes of an indirect preheated domestic hot water feed. (Source Lochinvar)


store. The differential temperature controller will actuate the solar circuit pumps when the temperature in the collectors is sufficiently high to economically add heat to the thermal store (typically when the collectors are around 8K higher than the store), and then cease when the coolest water in the store approaches the collector temperature (typically at a temperature difference of 4K) or the water in the store has reached a maximum limiting temperature. The thermal hierarchy for the supply of primary heat to the store will depend on the application – and the order is by no means certain. Potentially if local micro-hydro is available, then electrical heat sources (such


as heat pumps) could provide an all-year low carbon source feeding heat into the thermal store.


Energy Minister Greg Barker declared


at its launch that the intent of the RHI was ‘making renewable heat not just an environmentally sound decision, but also a financially attractive one’. The application of properly integrated thermal stores to multivalent systems provide an essential element to help this worthy expectation to succeed. CJ


l TIM DWYER is technical editor of the CIBSE Journal and teaching fellow at University College London. Details of the rates and eligibility for the RHI can be viewed at www.decc.gov.uk/rhi


36


CIBSE Journal April 2012


www.cibsejournal.com


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