About 10 years ago, I had the opportunity to work with the Maine State Housing Authority on a project to install the very first of what promised to be a “cold weather heat pump”. This technology promised to leap frog incremental advances in heat pump technology to create heat out of cold temperatures using a “dual compressor” technology. Heat Pumps move heat from one place to another using compressors, refrigerant, and phase changes. Refrigerators are heat pumps that move heat from the refrigerator and into the kitchen. Geothermal Heating, or Ground Source heat pumps, move heat from the relatively warm ground into the house. Using electricity to run compressors and fans, they can move more heat than they use running the compressors.
People have used heat pumps to heat and cool their houses for decades in the south. It was a perfect match for climates that don’t get very cold, but also have a significant cooling load. As it gets colder outside, it takes more and more energy to extract heat from the air, the capacity of the heat pump to create heat decreases, and the efficiency of the heat pump decreases.
A company called Nyle Corp., which was engaged in the business of drying things, lumber, dog food and the like, had developed the technology, and was trying to bring it to market as a solution to the energy crisis. They developed a cold climate heat pump water heater and a cold climate air source heat pump for heating homes. Unlike all of the major international heat pump companies like Sanyo, Daikan, Mitsubishi, and Fujitsu, which were incrementally improving heat pump technology through smarter controls, more efficient compressors and better refrigerant, Nyle Corp had a different idea. They developed a technology that used a two-stage compressor technology to boost the efficiency of the heat pump at low temperatures. At some point one of the managers of Nyle Corp, Duane Hallowell spun off a company called Hallowell Heat Pumps to manufacture the cold climate heat pump.
This product had some success, it actually did what it was intended to do when it worked, but ultimately the design proved too unwieldy to succeed in the harsh demands of space heating equipment. Many people hear about heat pumps in Maine, and they are reminded of the failure of the Hallowell Heat Pump, and they point to the companies’ failure as proof that heat pumps don’t work in Maine. Being involved in that early project, I became very suspect early on of the risks associated with the “cold climate” heat pump design. I installed 20 or so of the earliest units, and experienced multiple failures on multiple units, and always different failures. It wasn’t as if there was one problem that they needed to overcome, there were many.
When I step back from the details for a moment, I have to consider the fact that there are a bunch of multi-national corporations making incremental improvements in heat pump technology, all along the same lines; better compressors, better controls, variable frequency controls, etc. Then there is this little company in Maine with an approach that no one else is taking. It was hard for me to imagine that they would succeed.
But that doesn’t mean that air source heat pumps aren’t viable. It’s true that they have their limitations, due mostly to the fact that you pay per btu of output. Because of that, they can only provide 100% of the heating demand for houses with very light demand. The heat pumps made by the big multi-national corporations are extremely reliable, and are protected by robust warranties by companies that will be around to honor them. And they’re getting better and better. Mitsubishi now has a heat pump that puts out 100% of it’s output at 5 degrees, and 65% of it’s output at -17 degrees. And best of all, it produces heat at better than 300% efficiency, which is like buying oil for $1.50 a gallon.
As the world runs out of oil, three things will replace home heating oil as heating alternative in Maine; insulation, heat pumps and biomass. Our buildings will become better insulated, and they’ll be heated with pellets and electricity. Hopefully, we’ll continue the trend of greening our electrical grid, so that heat pumps will not only be the most efficient way of heating a home, but the energy used will come from the wind, the water, biomass and the sun.