Here, the first stage of backfilling has been completed, with the soil being well compacted to
ensure good contact and reliable heat exchange
between the earth and the loop.
During the first year of data collection, the water-to-air heat pump at left and the water-to-water heat
pump (square box in the middle) installed in the basement supplied space conditioning and water heating, respectively. During the second year, these two units were replaced by an integrated heat pump that
is expected to show significant gains in efficiency. oRNL and its partners will compare the performance
of both options, plus the common configuration of a water-to-air heat pump with desuperheater.
ditioning and water-heating loads in houses 1
and 2 with national average occupancy.
In November 2010, we replaced each home’s
two heat pumps with a single prototype GS-IHP
that provides both space conditioning and water
heating. For several years ClimateMaster has
been collaborating with ORNL under a Cooperative Research and Development Agreement
to develop the GS-IHP, which is expected to
be significantly more energy efficient than currently available heat pumps. Comparing data
from years one and two will establish the energy
savings of the GS-IHP compared to the two-heat-pump configuration. However, the most
common GSHP configuration on the market
is a single water-to-air heat pump with a desuperheater, which provides only a portion of the
required hot water as a byproduct when the
compressor operates for space heating or cooling. After the GS-IHP data is available, our team
will use calibrated models to compare the performance of all three configurations (one heat
pump with desuperheater, two heat pumps and
the GS-IHP). Cost estimates will also be provided. ClimateMaster anticipates launching a
Trilogy water-source heat-pump product line
based on the GS-IHP technology in 2011.
assessing early results
Preliminary analysis of the data measured at
the ZEBRAlliance research houses since November 2009 indicates that space-conditioning and
water-heating needs could have been provided
to the houses with ground heat exchangers
installed in just the excavations required for
construction — the basement overcut, below
the basement floor and the utility trenches. As
mentioned, no extra digging or drilling would
have been required except making the utility
trenches slightly deeper than normal.
The data showed that the installed loops and
heat pumps all performed as expected, indicating that they were adequately sized for the
3,700-square-foot homes. Temperatures of the
fluid entering the heat pumps ranged from 33°F
to 93°F (0.6°C to 34°C) at house 1 and 34°F to
90°F (1°C to 32°C) at house 2 — within good
proximity to the design range of 35°F to 95°F
( 2°C to 35°C). Heating and cooling set points
maintained throughout the year were 71°F
and 76°F ( 22°C and 24°C), respectively. From
January through March 2010, the supplemental
electric resistance heater was never activated at
house 1 and consumed only 66 kilowatt-hours
at house 2.
Early estimates indicate that when implemented at scale by a production builder in this
region, this FHX approach may be feasible at
$1,000 per ton. That compares with traditional
vertical-loop and six-pipe-per-trench horizon-tal-loop systems that typically are installed in
this region at $3,000 per ton and $2,250 per
ton, respectively. The actual cost of a particular project may vary depending on drilling/
trenching conditions, regional cost variations,
underground soil thermal properties and building geometry.
This September we’re scheduled to release
the FHX-sizing tool and performance-simulation model integrated with EnergyPlus, as
well as a comprehensive technical report documenting the basis for the FHX-sizing tool,
the performance-simulation model, the data
measurements and the validation of the sizing
tool and simulation model. ClimateMaster also
plans to make its Trilogy line of water-source
heat pumps, based on the GS-IHP technology,
commercially available in 2011. These and other
innovations may provide the affordability breakthrough for GSHP systems that homebuilders,
homeowners and energy-efficiency advocates
have been seeking. ST
