Three different Solar technologies have been used in the design for this home. Solar water heating and solar pool heating use efficient Solar Thermal technology to directly absorb solar heat into drinking water and pool water, while a 18-panel Solar Electric system reduces remaining power needs by 30%. The additional Solar Backup unit provides 2-3 days of pure backup power in case of utility outage.
Solar Photovoltaic System
The owner’s priorities for the Solar Electric system were to firstly provide enough automatic backup power to maintain the operation of critical circuits throughout the home in the event of a power outage. This included refrigerators, computer circuits, microwave, and limited lighting and outlets in the home. With backup power requirements in place, a solar array was sized to recharge the backup system on a daily basis. When the 2-3 day backup storage is not sufficient during prolonged cloudy conditions, a generator is connected to boost the batteries to full charge quickly and efficiently, saving fuel and reducing noise.
The next priority was to produce as much power from available South-facing roof space at the rear of the home. The two roof sections fit 9 panels each, providing over 400kWh per month in generated electricity for use in the home or to feed back into the utility grid. The utility-installed Net Meter tracks received and delivered energy, and bills the customer only for the ‘net’ power used. When the net usage is below zero, a credit is given towards the next month’s bill.
The Xantrex XW Solar Backup equipment was installed at the rear of the enclosed garage, and includes two monitoring systems for tracking solar production and battery state. The XW Monitoring Gateway provides basic statistics on hour-by-hour production from PV arrays, while the XW Configuration Unit allows detailed analysis of voltages and current flow throughout the system. The XW can also be configured for Wind Generator and Small Hydro charging inputs.
Solar Pool Heat
The ten black polymer panels in this installation are mounted flush to the flat roof and extend the owner’s swimming season by 50-80%. The system is controlled by a Pentair Suntouch unit, an excellent and multi-function controller which allows a single point of programming for solar, pump timer, chlorinator, cleaner, and other pool accessory devices. This controller also integrates seamlessly into the Intelliflo 4-160 Variable-speed pump, and instructs the pump to ‘boost’ flow to panels when Solar heat is available. The controller monitors solar temperature, pool, temperature, and ambient temperature, and automatically controls pump and valves to heat and cool (at night) the pool to a desired temperature.
Since this flat-roof system will not drain during a freeze event, a ‘freeze circulation’ feature moves pool water through the panels to prevent fracture of the components.
Solar Water Heat
The passive-style Solar Water Heating system at this residence was designed for minimal maintenance with year-round hot water generation. The insulated 4′x9′x8″ glazed collector provides 50 gallons of storage and direct water heating to the home, and can generate up to 120 gallons or more of hot water on warm sunny days. Water is piped to directly flow through the collector, using no pumps or transfer fluids to capture heat. A backup tank boosts water temperature when not enough sunlight is available, and a tempering valve reduces temperature when heated by solar beyond 130 degrees F.
The annual production of this system accounts for 60-80% of the average hot water needs of the home, which can amount to monthly savings of over $30 if preheating for an electric water heater. This system is also installed with a refillable water conditioning unit to help prevent scaling damage to the collector and house plumbing, as well as a series of bypass and drain valves for service.
