SOLAR TODAY - June 2011

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View a video overview of the project with interviews from the inauguration: solartoday.org/video.

Solar Cooling and Heating
System Highlights
Climate of Woodstock, Ontario:

solar resource: 3. 57 kilowatt-hours/

square meter/day average high/record low temps:

27. 8°F to 79.5°F (minus 2. 3°C to 26. 4°C)/ minus 34.1°F (minus 36. 7°C)

System details:
designer and installer: Proterra Solar
collector area: 5,594 square feet (520
square meters) of panels
average Production: 420 gigajoules
per year
collectors: 162 S-Power 20/2000 TPS
evacuated-tube collectors
controls: Solar cooling controller
designed by Proterra Solar
heat Exchangers: For the building, a 1.2
million-Btu-per-hour, double-walled,
plate-on-frame heat exchanger; for
domestic hot water, a 500,000-Btu dou-
ble-walled, brazed-plate heat exchang-
er; and for the pool, a 500,000-Btu shell-
and-tube heat exchanger
chiller: 30-ton Yazaki WFC-5C30 absorp-
tion chiller

Advanced industrial components:

domestic hot water standby tank:

3,000 gallons
solar Preheating: Two 120-gallon
(450-liter) tanks
Pumps: Seven, ranging from 2 to 7 horse-
power
freeze control: Propylene glycol
system installation: Tubes horizontally
custom-rack-mounted on a flat roof;
40-degree tilt, 0-degree azimuth
commissioned: November 2010

Cost and incentives:

Pre-incentive total: $1 million natural resources canada rebates:

$143,339

ontario solar thermal heating incentive: $143,339

total cost after incentives: $700,000

what kind of savings to expect, how
long the chiller’s going to run and all
the details.”
Based on this expertise, Proterra
designed a system of 162 S-Power
evacuated-tube collectors compris-
ing 5,594 square feet (520 square
meters) of collector area. The S-Pow-
er collector’s ability to be rotated was
a particular advantage.

A major challenge of the project, according to Ball, is that the building’s roof was not built to accommodate the wind loading of panels installed at a 45-degree angle. Instead of mounting the collectors with tubes oriented vertically, Proterra oriented the tubes horizontally, with the frames tilted 15 degrees and toward the south. Then each tube was rotated so its internal flat absorber stood at 40 degrees.“So we still get our 40-degree angle, but the wind loading is only at a 15-degree angle,” Ball explained.

Another challenge was finding a suitable controller for the solar heating and cooling system. Unable to find a plug-and-play controller that fit its needs, Proterra designed one. “If we didn’t have our own controller, we would have had to reengineer each [future] system,” said Ball. The standardized controller will reduce costs on future projects significantly, he added.

The solar collectors connect, via more than 4,000 feet (1,219 meters) of piping, to a 3,000-gallon ( 11,356-liter) storage tank, which provides two days of thermal storage. Through this solar loop, 4,500 gallons ( 17,000 liters) of propylene glycol heat 240 gallons in domestic hot water-storage tanks. A double-walled, plate-on-frame heat exchanger transfers 1.2 million British thermal units per hour to the heating system, a two-pipe building-heating loop. Starting this summer, the solar loop will feed a 30-ton Yazaki absorption chiller and cooling tower for air conditioning. The Yazaki absorption chiller is connected to the existing central cooling system and will reduce the electrical consumption of the two Trane chillers.

NELSON’S PHOTOGRAPHY

instead of mounting the collectors with tubes oriented vertically, Proterra oriented the tubes horizontally, with the frames tilted up 15 degrees and facing due south. then each tube was rotated so its internal flat absorber stood at 40 degrees.

Energy Agency also offered a small grant and technical advice.

“Between the people in Germany and Lucio, they’re all experts in designing solar systems, so they helped us to design the system to accept the absorption chiller,” said Ball. “Within that whole process, they tell you how many panels you need,

Got a recent PV or thermal installation to share? send your proposal and photos to editor@solartoday.org.

Recouping the Investment

Under Proterra’s direction, Trigon Construction Management coordinated the build, with Oxford Plumbing handling plumbing. Although the project took more than a year from concept through commissioning, the solar thermal installation took just 11 weeks. The system was inaugurated Nov. 9. After months when it was covered with snow, in March the system contributed the projected 6 million to 7 million Btu daily for water and space heating.

The $1 million project cost was offset by Canadian and Ontario incentives (see sidebar). Ball estimates the system will offset air-conditioning bills about 50 percent per year. It is projected to reduce electric and natural gas bills an average $5,000 per month. Based on the incentives and annual utility price increases averaging 3 percent, Ener Works expects the system to pay back its cost in less than nine years.

Ener Works’ technical expertise and flat-panel
collectors complement Proterra as the merged
company seeks to do more projects like Oxford
Gardens, said Ball. He noted the North Ameri-
can potential as fuel prices rise, as reflected in
Europe, where solar heating and cooling systems
with 50,000 square feet ( 4,645 square meters) of
collectors are not uncommon. “We think there’s
a lot of upside to this business,” said Ball, “and
we wanted to be one of the first companies to
get involved in it.”
Visit oxfordgardenssolarproject.com for proj-
ect details and real-time performance. ST