Brian Nelson indicated a short stack of hardcover books, pulling the first title onto the table and flipping to page 35.
“This is the Altherma picture, right here,” said the mechanical engineer and owner of Nelson Mechanical Design in Edgartown, pointing to a black and white diagram that looked more like a drawing from a physics textbook, with its arrows and straightforward renderings. The system in question was that of an air-to-water heat pump, a method of heating a house that works via a basic principle schoolchildren learn when using magnifying glasses outdoors: Concentrate the energy of the sun into a small space, produce immense returns of heat.
The air-to-water pump, manufactured by Daikin, is used to operate a radiant heat system in the home and heat the water supply.
Last year Mr. Nelson installed an Altherma heat pump system, the first of its kind on the Vineyard, in the home of West Tisbury resident Ted Bayne. Since then, Mr. Bayne’s home has become a test kitchen of sorts for the heat pump technology. Based on Mr. Bayne’s careful recording of his propane and electricity expenses (he has kept track of these costs since January 2007), the experiment has proven a success — so much so that “It’s no longer an experiment,” Mr. Nelson summed up.
Here is how it works: Heat is extracted from outdoor air via refrigerant coils through the heat pump itself, which sits outside and looks remarkably like an air conditioning unit, but more rectangular. Once concentrated in the coils, one kilowatt of solar energy yields four kilowatts of heat, for 400 per cent efficiency (Daikin’s official materials note that this rating can be up to 500 per cent). Baseboard electric heating, by contrast, is about 99 per cent efficient, according to 2011 U.S. Department of Energy numbers. Oil-fueled central heating ranges from 80 to 89 per cent efficiency.
The numbers and returns for a heat pump system sound futuristic, but they are really a call to the past. The book on Mr. Nelson’s table detailing heat pump designs and principles was published in 1947.
“In 1947, they had these ideas, this knowledge, this ability,” Mr. Nelson said with more than a touch of excitement in his voice.
Heat pumps and their implementation fell to the wayside in America not long after, however, thanks to cheap propane costs in the 1950s and 1960s. They have been the standard in other regions, like Japan, for decades.
“This is America; it always comes down to economics,” Mr. Nelson said. “When propane heads toward $4 a gallon, my phone’s ringing off the hook. For newer construction, people are saying ‘Why would I put in propane?’”
Mr. Bayne’s system is connected to the propane boiler system of radiant heating that was already in the home, but the heat pump can handle all warming functions until the temperature outdoors falls below 35 degrees, in which case the boiler starts to help out.
Most of the time, “we’re lying to the Viessmann [boiler],” Mr. Bayne said last week. “I keep sending water upstairs [via the heat pump] and it keeps coming back warmer.” He said that neither family members nor visitors have reported any changes in comfort level — whether the shower was colder than usual or the radiant heat less noticeable—since the heat pump was installed (although the dial in the shower did move a bit to accommodate the new system).
According to Mr. Bayne’s data, his annual home electric costs since installing the heat pump increased $1,104.76, since the pump is powered by electricity. His propane costs, however, dropped from about $6,500 to $2,000 — a savings of 54 per cent. The net savings for total home operating costs was $3,400. The heat pump system itself was an investment of about $20,000; in an interview last year with the Gazette, Mr. Nelson estimated the system would pay for itself in five to six years.
The heat pump is on track for just that timetable, and Mr. Nelson and Mr. Bayne couldn’t be happier.
“We were overjoyed the system behaved the way we want it to,” Mr. Nelson said. “It met our engineering goals — to have it deliver precisely as expected was very gratifying.”
“We were [actually] looking for . . . 45 to 50 per cent [savings],” he added.
“The paybacks are there,” Mr. Bayne said.
On learning the results of Mr. Bayne’s pump, Paul Pimentel of Edgartown, senior vice president of NORESCO, an energy-efficiency management company, jumped on board, taking what Mr. Nelson described as “the next quantum leap.” (Perhaps unsurprisingly, both Mr. Bayne and Mr. Pimentel are on the board of the Vineyard Power cooperative.)
“That shows us who the smartest of us is: Paul,” Mr. Bayne said. “He waited until this science experiment was complete.”
Mr. Pimentel’s goal is to eliminate reliance on propane and to heat his home entirely via heat pump. Although he still has a boiler in his home, it is for emergency purposes only, if the heat pump needs repairs.
To solve the problem of what to do when temperatures drop, Mr. Pimentel’s system stores energy for later use, using two large steel storage tanks filled with water. The solar energy still comes in through the outdoor pump and is compressed into heat, but those extra-efficient four kilowatts go into the water tanks. That way, when it’s the middle of winter and the home heating system needs backup, it draws from the already-existing store; it doesn’t need to rely on the pump to pull still more heat from the frigid air. It’s also bypassing the need to use more electricity in this way, since the original electric power running the system yielded enough for the future. Operating costs, Mr. Nelson estimates, drop by half.
In addition to eliminating propane use, the storage system also allows for more flexibility about when to run the heat pump. Mr. Pimentel could choose to operate it only when electricity costs are low, saving even more money.
“We could put excess electricity back into our own system,” Mr. Pimentel said of the implications for such a process. “And keep it on-Island [rather than in the grid].”
Both Mr. Bayne and Mr. Pimentel are interested in seeing exactly what the limits of the heat pump are; Mr. Bayne intends to fiddle with the cutoff heat pump/boiler mark this winter and see how the system functions at, say, 28 degrees to “put more pressure on the heat pump system to give me what I need.” Time — and more of Mr. Bayne’s data — will tell.
“When these heat pumps came out, it made the Island Plan more realistic,” Mr. Nelson said, referring to the Martha’s Vineyard Commission’s comprehensive plan. One of the plan’s goals is to virtually eliminate fossil fuel heating dependency by 2050.
“If the experience is anything like Ted’s, we could become a net zero Island,” concluded Mr. Pimentel.