Commercial Solar Water Heating System: Alta Torre Senior Housing

The solar thermal system at Alta Torre Senior Housing was added after the building had been designed. Unfortunately, this is an all-too-typical scenario for solar thermal installations, and it inevitably leads to “hide the big tank” meetings. In this case, the tanks could not be installed near the collectors due to space constraints. The decision was made to locate them 100 feet from the collectors in a concrete-block outbuilding that would also house a backup generator.

One of the downsides to locating the tanks away from the solar collectors is the expansion of the underground piping, which needs to be taken seriously. In thermal systems, temperatures can reach 250°F and then cool to less than 100°F with the start of the pump. We specified a preinsulated product called Copper-Core, a gasketed piping system that features integral bronze couplings with built-in expansion control. Copper-Core’s couplings are not fixed joint, and the sections are not soldered. A concrete thrust block was installed at each corner in the trench to prevent excessive pipe movement.

“At the very end of the project, after we had placed our tanks and installed all of the related equipment, it was discovered that the generator was too close to the neighboring building to meet the local fire code. The architect determined that if a roof was not put on the mechanical building, the generator could stay where it was. To deal with this new plan, we gladly jacketed all of the above-ground piping and had custom metal coverings made for items such as pumps and controls.”

—Justin Weil, president, SunWater Solar

Overview

DESIGNERS: Justin Weil, president, SunWater Solar, sunwatersolar.com; structural engineering, Dave Helmich, D/PM Engineering, d-pminc.com; underground piping design, Jim Andrews, Thermal Pipe Systems, thermalpipesystems.com
LEAD INSTALLER: Jerry Saecho, foreman, SunWater Solar
DATE COMMISSIONED: May 2010
INSTALLATION TIME FRAME: 30 Days LOCATION: Palo Alto, CA, 37.4°N
SOLAR RESOURCE: 5.4 kWh/m2/day
ANNUAL HEATING DEGREE-DAYS: 2,849, base 65°F
RECORD LOW TEMPERATURE: 15°F
COLLECTOR ARRAY AREA: 960 sq. ft.
AVERAGE ANNUAL PRODUCTION: 85.5 MWh

Equipment Specifications

COLLECTORS: 24 Heliodyne 410-002, 40 sq. ft. each
HEAT EXCHANGER: Young HEX 64 Y 2PB External
PUMPS: Two Grundfos UPS-50-80/2 VersaFlo, ¾-hp
STORAGE: Two 534-gallon Hanson GS-42-534-V tanks, 1,068 gallons total CONTROLS: Steca TR 0301 U
FREEZE CONTOL: Closed-loop glycol
COLLECTOR INSTALLATION: Custom pipe racking on low-slope roof, modified bitumen, 180° azimuth, 34° tilt

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