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Heating with solar

Perforated glazing on solar panels ups the collection efficiency of energy, even on white walls.


December 29, 2011
Kathy Smith

Plastech Inc. decided it had to do something about the $6,000 a year it was paying to heat its shipping area using natural gas.

The thermoplastic parts manufacturer, a division of the MI Integration Group with a 26,000 square-foot plant in Sherbrooke, Que., wanted to do the job using solar technology without altering the ivory coloured building’s exteriors with a darker, more absorptive tone. But light colours, such as white or ivory, aren’t generally recommended for most solar collector absorbers.

Enerconcept Technologies, a Magog, Que. manufacturer of solar collectors, had the solution. There would be no dark paint costs or changing of the exterior building’s aesthetics with the company’s recently developed solar technology using patented perforated glazing on a wall-mounted solar air heater.

The Lubi installation looks more like a wall of windows than solar panels and is rated at 80.7 efficiency by the Canadian Standards Association (CSA-International).

On a black surface, the Lubi is 20% more efficient than any other wall-mounted solar glazing or metal collectors. On a white wall such as Plastech’s, efficiency is up 58%.

With darker colours, the collector provides air temperatures of up to 45 degrees C above ambient outdoor temperatures and maximum outputs of 254-btu per hour per square feet (800-watts per square metre). Since 2010, temperature was measured at 25 degrees C on sunny days. This extraordinary performance was certified by the National Solar Test Facility (NSTF), a Mississauga, Ont.-based, third-party laboratory that tests and rates solar technologies under controlled temperature, sunlight and wind, and is sanctioned by the Solar Rating and Certification Corp. (SRCC) in Cocoa, Fla.

“Solar air heating has been a good method of reducing energy costs and CO2 emissions, preserving the environment and maintaining a comfortable workplace for our employees,” says Stephane Tremblay, general manager at Plastech.

Using dark walls as an absorber is recommended for optimum solar performance efficiency; however, the inherent performance disadvantages of Plastech’s light coloured wall were offset with a 40% larger collector.

The company received incentives from Natural Resources Canada and a rebate from the Energy Efficiency Fund (EEF) of natural gas utility, Gaz Metro. The payback on the project is four years and in addition to the $6,000 in annual savings, the collector reduces CO2 emissions by 15 tons per year.

Installed by Sherbrooke-based metal contractor RTSI, the 90-by-24-foot-high wall-mounted solar collector has clear glazing that from a distance appears to be windows.

Here’s how it works: sunlight radiates through the glazing where it’s absorbed by the building’s corrugated steel wall. The Lubi’s efficiency comes from its patented design featuring 906 perforations per three-by-one-foot panel. As the indoor ventilation fan draws collected warm air through the six-inch-deep collector, ambient air draws through the perforations and cools the panels. Some wall-mounted solar collectors suffer significant heat loss through the glazing or metal façade. The Lubi panel minimizes heat loss and increases efficiency.

Heating the shipping area
When Plastech’s 5,500-square-foot, three-door shipping area calls for heat, the plant’s indoor mixing plenum box’s motorized damper opens and its 7,000-cfm fan draws solar collector heat to the area through ductwork. Heated air is distributed via 36-inch-diameter DuraTex, a non-porous fabric air dispersion system manufactured by DuctSox in Peosta, Iowa. The lightweight duct has no diffusion through the plant until it enters the shipping area where linear diffusion orifices disperse the air evenly.

The fabric ductwork is hung with a cable suspension system approximately two feet below the 24-foot-ceiling. If the shipping area doesn’t reach its set point temperature of 21 degrees C from solar collector heat, a second motorized damper opens to add recovered ambient production floor machinery heat through the same duct system.

Heat from the injection moulding process is enough that Plastech exhausts surpluses and doesn’t need a dedicated heat source for the production area during winter. If the combination of solar and heat recovery still can’t satisfy the shipping area’s set point temperatures, a propane gas-fired heater from Reznor (Memphis, Tenn.) acts as a back-up source.

Typically the solar collector and heat recovery supplies all the shipping area heating needs and reduces the Plastech’s future gas-fired heating consumption to near zero.

A direct digital controller from Johnson Controls (Milwaukee, Wis.) monitors the heating process and controls the dampers from Belimo Aircontrols USA (Danbury, Conn.) and the mixing box’s 7,000-cfm fan manufactured by the LFI division of Canarm, in Brockville, Ont.

Leprohon, a Sherbrooke-based mechanical contractor that offers design, installation and service to its industrial, commercial and residential customers, solved several challenges as the project HVAC contractor.

It’s custom-fabricated sheet metal ductwork circumvents a machinery crane that shares a common surrounding wall area with the solar collector. Plus, the north side shipping area required fabric ductwork installation traversing the entire building’s width to the collector’s optimum south-side solar exposure location.

The shipping area’s indoor air quality now receives a minimum of two air changes per hour, twice what the local code requires, but at no fossil fuel expense to Plastech.

The addition of wall-mounted solar heating offers multiple advantages to Plastech. Throughout its minimum 15-year lifecycle, it will tally at least $90,000 (based on 2011 energy prices) in projected annual energy savings and eliminate more than 300-tons of CO2 emissions, while providing employees with better indoor air comfort.

Information provided in this application feature was supplied by Enerconcept Technologies. Visit www.enerconcept.com.