Solar Domestic Hot Water and Heating Retrofit
ARC Mechanical added a new heating system and solar hot water units at the Bradford Village Apartments, a three-building, 21-unit complex in the same town as ARC is headquartered.
As an approved Vermont Solar Thermal Partner, through Renewable Energy Vermont, ARC worked with Realty Resources Management, which oversees the complex, to secure over $14,000 in incentives to help keep the project affordable and moving forward. The completed system for the three buildings resulted in a 65 percent reduction in boiler size and the solar system now provides 76 percent of the annual hot water consumption, well more than the original target.
Project Specifics
The solar design criteria called for the installation to provide 50 percent of the annual hot water needed by the complex’s 49 residents. However, upon completion, it is now projected to provide approximately 76 percent of those needs. ARC designed and fabricated steel mounting racks which were attached to concrete piers for eight 4 X 10-foot solar panels for two buildings and four panels for the third, capable of producing 90 million BTUs annually, or 489,840 BTUs per day.
Hot water is generated by the sun throughout the day and stored in a series of six 119-gallon thermallyinsulated solar tanks. In a traditional water heating system, water is pulled from underground lines at approximately 40 degrees and then heated to the specified temperature. With the solar system, the stored water entering the two 119-gallon indirectfired, oil-fired water heaters can be as warm as 115 degrees, even on a cloudy day. By reducing the need to heat cold water, the complex can expect substantial savings in heating oil expenses.
ARC replaced four existing boilers (combined 820,000 BTUs) with two boilers (one 105,000 BTU and one 180,000 BTU). The new boilers have an AFUE (Annual Fuel Utilization Efficiency) of 86 percent, while the old boilers had an AFUE of 78 percent. The boiler sizes were dramatically reduced due to weatherization of the buildings, including replacement windows, new insulation, and the addition of the solar hot water system. Prior to the installation of the solar packages, the domestic hot water generation was, by far, the largest consumer of energy from the original system. To ensure that tenants at the complex had no disruption in hot water during the project, ARC installed a temporary boiler that suited their needs.
Mechanical Highlights
- Domestic water heating system consists of twelve flat plate solar collectors (720 sf), six 119-gallon solar storage tanks and two 119-gallon indirect fired water heaters.
- Four boilers (combined 820,000 BTUs) replaced with two Buderus boilers (combined 285,000 BTUs). New boilers have an AFUE of 86%.
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| Solar pump station. | Second new Buderus boiler with four solar storage tanks to the left. | One new Buderus boiler with two solar storage tanks (on left) and an indirect fired water heater tank. | ||
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| Four flat plate solar collectors serve building C at the apartment complex. | Eight flat plate solar collectors serve buildings A and B at the apartment complex. | |||
