Electric Heat Pumps

Technology Roadmap Sections and Deliverables

• 2EHP - Electric Heat Pumps

The Electric Heat Pumps (EHP) roadmap is a level 2 roadmap at the product level, which is part of the level 1 roadmap for Electrification (1ELE). Levels 3 and 4 roadmaps would be subsystem and component roadmaps for Electric Heat Pumps (EHP).

Roadmap Overview

An electric heat pump spatially transfers heat from a low-temperature source to a high-temperature application. This process is based on the thermodynamics of the vapor compression refrigeration cycle, where the heat pump operates in a closed loop with a refrigerant fluid circulating within. In the "evaporator," the refrigerant fluid undergoes a phase change from liquid to vapor at a constant pressure, absorbing heat in the process. Following this, the "compressor" elevates both the pressure and temperature of the refrigerant, preparing it for the "condenser." Here, the refrigerant rejects the absorbed heat and transforms it back from a vapor to a liquid. Finally, an "expansion device" reduces the refrigerant's pressure and temperature back to the levels suitable for the "evaporator", completing the cycle and allowing it to commence anew.

Heat pumps have versatile applications, spanning various power scales and temperature lifts. These range from residential and commercial to industrial settings. The current dominant technology is fossil-fuel-burning boilers which are not sustainable environmentally and not strategic from an energy security perspective. This roadmap will focus on domestic heat pumps for designed residential applications in cold climates.

Design Structure Matrix (DSM) Allocation

Roadmap Model using OPM

Figures of Merit

Alignment with Company Strategic Drivers

Positioning of Company vs. Competition

Technical Model

The above values yield a COP of 4.5376. Adopting a finite difference method and perturbing the isentropic and mechanical efficiencies as well as the evaporator effectiveness by +/- 1 percentage point yields the following sensitivities both in absolute and normalized values of the COP:

Financial Model

TBD

Key Publications, Presentations and Patents

Welch et al. (2013). Motor Cooling Applications (US 8,434,323 B2). U.S. Patent and Trademark Office. This patent is from Johnson Controls, a prominent figure in the HVAC market, specializing in heat pumps and chillers. The patent details a cooling method that utilizes refrigerant fluid to directly cool the compressor's rotor. This technique potentially enables the compressor to rotate at faster speeds, producing higher pressures. Consequently, this could lead to elevated temperatures for heat pump applications, as well as, allows for smaller compressors where thermal management is a key hurdle. The patent is expired, the concept can be adopted in future use.

Canino et al. (2023). Solar Integrated Chiller Method and System (US 11,761,688 B2). U.S. Patent and Trademark Office. Smardt Chillers, a leading innovator in the field of high-efficiency chillers and heat pumps, has patented an integration of PV solar panels with an air-cooled chiller system. The design harnesses solar panels to provide power to auxiliary and balance-of-plant components within a typical chiller or heat pump configuration. This design increases the overall efficiency of the heat pump. Furthermore, with an adequately dimensioned PV array, the system has the potential to operate autonomously, both grid-tied and off-grid. The patent is recently granted.

Geyer et al. (2016). Method for Controlling Harmonics and Resonances in an Inverter (US 9,385,585 B2). U.S. Patent and Trademark Office. This is a patent by ABB, a global market leader in machinery, controls, and power electronics. The patent presents a method to control and mitigate harmonic distortions in inverters of electrical systems. By determining voltage vector sequences, evaluating their effects on the system, and using optimal sequences, the invention aims to enhance inverter efficiency and reduce harmful resonances. By controlling harmonic distortions in inverters, this invention can significantly improve the overall efficiency of centrifugal heat pumps driven by variable speed compressors. The patent is due to expire in 3 years.

Technology Strategy Statement

TBD

References

TBD