CHP Buffer Vessel in DSM

[RossThompson87]

Hi,

Myself and a colleague are working on a hotel project where a CHP system has been proposed to meet the very high DHW demand.

As the demand for DHW will be sporadic, the client plans to use a very large buffer vessel with a micro CHP.

However IES just models the CHP based on its max thermal output, so the support from the buffer vessel is ignored.


Is there anyway to account for this? The only way I can think of is to produce a supporting calculation that justifies entering a higher max thermal output.

Any help would be appreciated.

Ross

[Terence]

There is no explicit option to model a buffer vessel within the VE however the advantages it offers could be reflected. The CHP will function whenever there is a heating load greater than the minimum heating fraction. As CHP’s are typically inefficient at low part loads the software default will switch off the CHP if the Heating load drops below 50% of the rated thermal output.

When the buffer tank is combined with a CHP it can be utilised for a greater range of loads as it is effectively switching on and off to maintain the buffer tank. This ability to service a load range can be allowed for by reducing the Minimum fraction of rated heat output.