Energy consumption of cold climate heat pumps in different climates – Comparison of single-stage and two-stage systems

• Heating and cooling energy demand of barrack buildings in northern climates has been simulated in detail.
• Building insulation is one of the key elements to reduce energy consumption.
• Two-stage heat pump systems show significant energy improvements over single-stage units reducing backup heating greatly.
• Primary energy demand or greenhouse gas emissions are a good measure to compare buildings and their HVAC systems.

The aim of the study presented in this paper is the comparison of different possibilities to reduce the power consumption and environmental impact of barrack buildings of the US army. For this purpose different building standards, different heating and cooling appliances and a cold storage concept are compared using annual building simulations. These simulations are carried out for central and northern locations in the US. The focus of this paper is the applicability of cold climate heat pumps in these climates. A coupled building and appliance model has been established to allow a fair comparison based on first energy usage and CO2 emissions. Altogether seven different building configurations in six different locations have been investigated. Simulation results show the most significant energy savings (up to 90%) can be achieved by improving building insulation and heat recovery of the ventilation system. Second major improvement is the usage of two-stage heat pump systems, which drastically reduces the need for backup heating systems and lead to seasonal efficiencies (SCOPs) in the area of 3.0, or in other words an energy saving of 20–35%. Thermal storage and control concepts such as night setback in comparison show little effect. The simulation results also showed that primary energy demand or greenhouse gas emissions are better measures for the comparison of environmental impact than COP and SCOP.