The Geo-Heat Center conducted a life-cycle cost analysis for various heating, ventilating, and airconditioning (HVAC) systems for the proposed new office building on the Winnebago Reservation in northeastern Nebraska. Three HVAC systems were considered: (1) rooftop units with gas heat and direct expansion (DX) cooling (air-cooled condensers), (2) air-source heat pumps, and (3) geothermal heat pumps (GHPs).
This work has been funded and completed under Midwest Research Institute, National Renewable Energy Laboratory (NREL) Task Order No. KLDJ-5-55052-01, “Feasibility Studies and LifeCycle Cost Analysis”, Task 2: Winnebago Life Cycle Cost Analysis.
The heating and cooling loads were estimated by using building energy simulation software. The peak cooling load is estimated at 264,000 Btu/hr (22 tons), and the peak heating load is estimated at about 178,000 Btu/hr. The annual energy demand of the building is 246 kBtu for heating and 479 kBtu for cooling.
To compare alternatives, the net present value (NPV) of 30-year life-cycle cost was computed for each alternative, as shown in the table below. The GHP system was found to have the lowest net present value of life-cycle cost, approximately 18% lower than the conventional alternatives, which have very similar life-cycle costs to each other. The GHP system, although more expensive to install, has considerably lower operating and maintenance costs than conventional alternatives.