The Parkview Place energy systems schematic drawing above shows a simplified building cross-section in a north-south plane.  Letters correspond to major system components.  B (the largest circle) highlights the radiant floor heating and cooling systems that deliver comfort to the interior of the building.  Closely-spaced tubing in the concrete floors conveys warm water in heating season and cool water in cooling season, when commanded by local thermostats.  Tubing in the first floor was placed prior to pouring the 5” thick floor slab.  Upper floor tubing was placed in 2” thick concrete layers on top of the wood floor structures.

The primary space conditioning system, labeled  C, uses two geothermal heat pumps and an array of helical ground heat exchangers.  The water-to-water heat pumps, stacked in the garage, are coupled to 14 helical coils of plastic tubing that extend to 22 foot depth, configured in line near the building along the south and east walls.  Since ground temperatures are relatively stable year-round compared to outdoor air temperatures, the heat pumps can operate very efficiently to extract heat from the ground in winter, and discharge heat to the ground in summer.  

Water heating components D include a 600 gallon insulated domestic water tank under the main stair, a roof-mounted solar thermal system and connecting piping, an auxiliary water heating loop off one of the heat pumps, and a large immersed heat exchanger in the domestic water tank.  The heat exchanger contains pressurized water that is heated as it passes through on the way to hot water taps (showers, sinks, etc.). Water at the kitchen sinks is heated by flash electric water heaters, to reduce water and heat loss from the long pipe runs to the far corner kitchen locations.

The photovoltaic (PV) panel array E is the subsystem that captures the renewable solar energy needed to achieve zero net energy (ZNE) performance.  64 SunPower panels are placed in a low-slope configuration parallel to the roof surface, where they generate peak output of about 17 kW.  The NightSky system A spray-cools water on the roof while cleaning the PV panels to enhance their output.  Spray and rain water are collected at a single roof drain, from which they flow through a ground-mounted filter into a site-built 11,000 gallon tank under the storage spaces south of the shared garage.  At high rainfall rates, excess water bypasses the filter and drains around the GeoHelix boreholes to enhance ground heat transfer.  Cooled water in the tank provides a secondary radiant cooling source in favorable weather conditions. 

Heating and Cooling Systems