VINEYARD HAVEN, MASS.—Until this summer, the 16,000 gallons of groundwater that runs below the Mansion House Inn, Health Club & Spa was a nuisance. Because the inn’s subbasement sits in the middle of the groundwater, the water constantly had to be pumped away to protect the structure. Now, the water is an asset. How so? It stores energy not only from the sun above the inn but also energy pumped into it via a sophisticated geothermal heat pump system. For Sherman and Susan Goldstein, the inn’s owners, realizing the water’s potential was like striking gold.
The history of the inn’s geothermal system goes back to 2007 when Jay McMann, the Mansion House’s plant engineer, attended a geothermal open house held by Nelson Mechanical Design (NMD). McMann realized the potential for geothermal and recommended it to the inn’s owners. It was NMD that recently installed the geothermal heating and cooling system at the inn.
Within the Mansion House there is now a geothermal water loop that runs throughout the property. Each of the 40 rooms and suites has a heat pump installed and there are other heat pumps throughout the inn. During the summer the heat pumps are used to extract heat from the air. It is transferred to the water loop which ultimately transfers the heat energy to the ground water via a heat exchanger.
“All the heat pumps in the guestrooms are pulling the heat into the water,” says Brian K. Nelson, principal with NMD.
He says the system actually stores more energy in the ground than the inn will ever need. In a second phase of the project, the system will be expanded so that it can harvest the heat energy in the ground water to not only heat the inn during the colder months but also provide all the energy needed to heat domestic hot water and pool water.
Heat Pumps in Reverse
“All we will be doing is running the heat pumps backwards,” Nelson says. “That is the magic of the heat pump system—the pumps are reversible.”
The temperature of the groundwater is a steady 55 degrees; the temperature in the water loop is 85 degrees. The water can be heated to as high as 160 degrees thanks to a compressor. The groundwater moves slowly so it can be used as a “solar battery,” Nelson says. A fuel oil boiler system is available as a backup for heating but it will be used only rarely.
Thanks to a direct digital control (DDC) system that incorporates wireless thermostats, infrared occupancy sensors and switches, heat pumps only run when needed in guestrooms. Because the DDC system is Web based, the inn’s engineer can monitor how effectively the heat pumps are working.
“Before we had to wait for guest complaints,” Nelson says. “Now we can be proactive. The transition to the new system has been very seamless.”
Ice Maker Feeds Energy into System
The inn’s new water cooled ice maker in the Zephrus Restaurant is also connected to the geothermal system. Heat generated by the machine is put into the water loop instead of the restaurant where it was deposited by the old air cooled machine.
Nelson expects the inn to recover its investment in the geothermal and energy management systems in four years. Rebates obtained through Massachusetts’ Cape Light Compact will pay for a significant percentage of the work.
To further reduce the inn’s carbon footprint, the Goldsteins are planning a rooftop garden that will generate produce for the restaurant.
Click here to access a PDF displaying how the geothermal heating system will work.
Click here to access a PDF displaying how the geothermal cooling system will work.
Also go to the Mansion House Inn, Health Club & Spa.
Glenn Hasek can be reached at editor@greenlodgingnews.com.
