Rye, New Hampshire Couple Spins Meter Backwards with Solar
In an effort to reduce fossil fuel dependence and CO2 emissions, Marc and Michele Sopher decided to install a Geothermal heating system and a grid-tied photovoltaic array in their new home.
The four-ton, ground source geothermal heat pump uses naturally stable underground temperatures to produce heat at relatively high efficiency, compared to resistive electric heating. But as a “renewable” technology this large heat pump is only as green as the considerable amount of electricity that is needed to power its pump and compressor.
The Sophers were aware of this tradeoff while designing their home, and made the conscious decision to use solar electricity (photovoltaics) to help power the geothermal system.
This dual renewable approach should result in a near ‘net zero’ CO2 household—how close will not be known until after a year or two of data collection to see if the grid-tied solar system is large enough to meet the geothermal systems’ power demand.
In addition to renewable energy systems, the home features modern building materials that are efficient, of sustainable origin, and non-toxic. Uncommonly high insulation levels of R60 in the ceilings and R40 walls help insure minimum heat escapes during the cold New England winter.
Pat Coon and Will Kessler of ReVision Energy were consulted by the Sophers to determine the best use of the house’s excellent southern exposure. “We took a look at their system design and it made economic and environmental sense. With the geothermal pump’s electric load, solar PV is the ideal solution,” says Kessler.
The system consists of eighteen Evergreen Solar photovoltaic panels and will produce around 380 kWh monthly, with an annual CO2 savings of around 7,000 lbs.
The recently installed solar system qualifies for an uncapped 26% federal tax credit and the $6,000 state rebate offered by the New Hampshire Public Utility Commission.
In order to track the gross renewable power generated on site, ReVision Energy installed a separate meter adjacent to the DC/AC inverter. PSNH’s primary meter is bi-directional, so when the panel’s electric production exceeds demand, the extra kilowatt-hours are banked under the NH Net Metering Program.
“It is very gratifying to see the meter outside spinning backward!” said Michele Sopher.