DOE Lists Innovations in Heat Pumps

December 17, 2014 By Linda Hardesty

heat pumpFor climates with moderate heating and cooling needs, heat pumps offer an energy-efficient alternative to furnaces and air conditioners, says a US Department of Energy article. The most common type of heat pump is the air-source heat pump, which transfers heat between a building and the outside air. A heat pump can trim the amount of electricity used for heating by as much as 30-40 percent, says DOE. However, the efficiency of most air-source heat pumps as a heat source drops dramatically at low temperatures, generally making them unsuitable for cold climates, although there are systems that can overcome the problem.

DOE lists a number of innovations that are improving the performance of heat pumps.

  • Unlike standard compressors that can only operate at full capacity, two-speed compressors allow heat pumps to operate close to the heating or cooling capacity needed at any particular moment. This saves large amounts of electrical energy and reduces compressor wear.
  • Some models of heat pumps are equipped with variable-speed or dual-speed motors on their indoor fans (blowers), outdoor fans, or both. The variable-speed controls for these fans attempt to keep the air moving at a comfortable velocity, minimizing cool drafts and maximizing electrical savings. It also minimizes the noise from the blower running at full speed.
  • Many high-efficiency heat pumps are equipped with a desuperheater, which recovers waste heat from the heat pump’s cooling mode and uses it to heat water. A desuperheater-equipped heat pump can heat water 2 to 3 times more efficiently than an ordinary electric water heater.
  • Another advance in heat pump technology is the scroll compressor, which consists of two spiral-shaped scrolls. One remains stationary, while the other orbits around it, compressing the refrigerant by forcing it into increasingly smaller areas. Compared to the typical piston compressors, scroll compressors have a longer operating life and are quieter. According to some reports, heat pumps with scroll compressors provide 10° to 15°F (5.6° to 8.3°C) warmer air when in the heating mode, compared to existing heat pumps with piston compressors.
  • Although most heat pumps use electric resistance heaters as a backup for cold weather, heat pumps can also be equipped with burners to supplement the heat pump. Back-up burners help solve the problem of the heat pump delivering relatively cool air during cold weather and reduces its use of electricity.

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