[TRNSYS-users] OpenStudio to TRNSYS for geothermal chiller/heater plant modeling

[Ajit Naik]

Hi All,

I'm looking to model a building served by a hydronic DOAS & hydronic radiant panels/chilled beams tied to a water-to-water heat pump with heat recovery, a  vertical-borehole geothermal condenser loop with waterside economizer, supplemental boiler, and supplemental dry cooler. The building in question has a frequent simultaneous demand for cooling/heating, so the WWHP is expected to frequently run in heat recovery chiller-heater mode.

I've set up the airiside model in OpenStudio, but have run into the issue that the plantside chiller-heater component is not available in OpenStudio. As such, I'm attempting to extract the hourly OpenStudio loads, model the plant in TRNSYS, determine equivalent heating & cooling COP from the TRNSYS results, and input these simulated equivalent COPs on an electric boiler and air-cooled chiller in OpenStudio to obtain final results. I plan to use the TRSNSYS WWHP and dry cooler electricity inputs along with the OpenStudio load outputs for efficiency computation (and directly use the boiler gas results from TRNSYS)

To this end, I've output the hourly loads on all hydronic coils, and am attempting to apply them via an equation block to generate chilled & hot water return temperatures for supply side inlet input into a Type 927 WWHP with wellfield (emulating the GHP example) plus a supplemental boiler and fluid cooler maintaining loop temps when necessary.

However, I am having trouble figuring out how to model the impact of  heat recovery and free cooling on the overall efficiency. Is there a way to directly model the heat recovery in such a plant side application, and any suggestions on how to account for waterside economizer on reduced WWHP input energy?

Thanks in advance for any ideas/suggestions!

Ajit Naik
BEMP
Energy Engineer

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