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capital costs of ASHP, GSHP, MSHP from ResStock capacity outputs

asked 2020-10-21 14:05:51 -0600

sashadf1 gravatar image

updated 2020-10-21 15:41:28 -0600


This is a question specifically for the ResStock team at NREL.

When trying to estimate the capital cost of units installed, there can be a normalized cost ($/(kbtu/hr)) and a fixed cost. Specifically I am trying to calculate the normalized cost based off of the ResStock output for 3 different equipment; ASHP, MSHP, and GSHP.

I am simulating in a really cold climate (Maine) so I want to be sure I am not underestimating the size of the equipment needed.

ASHP has two capacity fields;

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These units are in watts. There is also a simulation_output_report.size_heating_system_kbtu_h field, which for ASHP is equal in value to the hvac_heating_capacity_w field after performing unit conversions.

Which of these three fields (after appropriately converting units) should I use for estimating the normalized cost? Should I sum hvac_heating_capacity_w and hvac_heating_supp_capacity_w?

Would the method change for MSHP, ASHP, or GSHP? I noticed that MSHP has hvac_heating_supp_capacity_w = hvac_heating_capacity_w, while GSHP has a value for hvac_heating_supp_capacity_w that is larger than hvac_heating_capacity_w.

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Follow up to this; right now, to calculate normalized cost for all equipment types, I am using the field simulation_output_report.size_heating_system_kbtu_h because it is typically larger than or equal to simulation_output_report.size_cooling_system_kbtu_h for my simulations. If simulation_output_report.size_cooling_system_kbtu_h were larger I would use that.

I would just like to confirm that this is the correct thing to do.

sashadf1 gravatar image sashadf1  ( 2020-10-21 14:08:12 -0600 )edit

I don't have any experience with ResStock, but the supp value is probably the supplementalheating coil for conditions outside which the heat pump coil is expected to be effective. In which case, either of the other two values would be the one you should use. See this example for ZoneHVAC:WaterToAirHeatPump...

MatthewSteen gravatar image MatthewSteen  ( 2020-10-21 15:50:21 -0600 )edit

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answered 2020-10-21 15:43:12 -0600

Doesn't this depend on whether the kbtu/hr in your $/(kbtu/hr) cost equation is based on rated cooling capacity or rated heating capacity?

If you're using costs from, you'd want to use the rated cooling capacity since that is how that cost data is derived.

"hvac_heating_supp_capacity_w" is the capacity of the supplemental electric resistance heating, so you could use that too if you have cost data for that component.

In case you weren't aware, ResStock can do these cost calculations for you, using these fields:

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Thanks! We dont have cost data for the supplemental electric resistance heating, just for the hvac system as a whole. Will investigate having ResStock do the calculations for us, we have been doing them ourselves manually to this point.

sashadf1 gravatar image sashadf1  ( 2020-10-21 22:58:32 -0600 )edit

ResStock calculations agree with what we have been calculating manually for the capital costs. We are now calculating capital costs based off of the cooling capacity of the equipment for normalized cost and then summing this with a fixed $/unit cost to determine the total cost.

sashadf1 gravatar image sashadf1  ( 2020-11-04 23:24:39 -0600 )edit

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Asked: 2020-10-21 14:05:51 -0600

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Last updated: Oct 21 '20