Park Central Apts cut costs with
solar-generated electricty and hot water

Wednesday, March 18, 2009

Developer Rich Arnesen (right) discusses the solar installations on the roof
of Park Central Apartments with a building resident.

From a fact sheet published by Focus on Energy:

Water heating can be a significant cost in the operation of multifamily residential buildings. On average, water heaters account for between 15 and 25 percent of the energy consumed by residents in multifamily dwellings, according to the Energy Information Administration (EIA), the independent statistical agency of the U.S. Department of Energy. For some multifamily residences, a solar water heating system, which uses the sun’s energy to preheat water entering an existing gas or electric water heater, may be a cost effective means to reduce monthly heating bills. . . .

Park Central Apartments, located in downtown Madison, is a development that has integrated solar hot water technology into a complete portfolio of energy saving measures. Park Central Apartments’ solar hot water system services 52 of the 76 units (which range from studio to three-bedroom units). The solar hot water system will save its tenants an estimated 37 percent of the building’s water-heating load. In addition to the solar hot water system, the electrical load for common spaces within the Park Central Apartments building is partly satisfied by a 10-kilowatt(kW) solar array.

The developer implemented several energy efficiency measures to reduce the building’s overall energy consumption, allowing the renewable energy system to satisfy more of the energy load. For example, the units are outfitted with ENERGY STAR® qualified appliances and windows, energy saving showerheads and aerators, and the developer also installed a high efficiency furnace. The heavily insulated basement parking area is not heated, further reducing the building’s heating load. In addition, according to the developer, the R-value (a measure of heat resistance for insulation) for apartment units exceeds code by 20 percent. The developer’s
passion for renovating old public buildings and new construction with energy saving measures has helped to make it Wisconsin’s first “green built” multifamily residence.

Park Central Apartments’ solar hot water heater is a closed-loop, pressurized hydraulic system. The 320-square-foot solar collector is located on the building’s roof and is largely hidden from view at the street level. Pumps cycle the solar fluid from the collector to a set of hot water tanks located five stories below within the building’s basement. Because the solar hot water system was installed during construction, the intake and return pipes were routed from the roof to the hot water storage tanks using interior space. Routing pipes through an interior space—as opposed to routing them along the outside of a building—limits heat loss and improves system efficiency. Physically, the limiting factor for the solar hot water system was the allocation of space for the hot water storage tanks in the basement. Otherwise, additional roof space could have been used to increase the size of the collector and further reduce the building’s natural gas water heating load.