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Solar Cuts Plant's Gas Heating Costs to Near Zero

November 21, 2011
KEYWORDS heating / solar
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Canadian thermoplastic parts manufacturer Plastech Inc. wanted solar technology to eliminate the $6,000 (CAD) annual natural gas energy costs of heating its shipping area, but without the expense of altering its ivory color building’s aesthetic exteriors or painting it a darker, more absorptive color.

Light colors, such as white or ivory, are rarely recommended for most solar collector absorbers. However recently-developed solar technology using patented perforated glazing on wall-mounted solar air heaters made solar possible without bearing dark paint costs or altering the 26,000-square-foot building’s exterior aesthetics. The solar air heater appears more like a wall of windows than a solar collector for Plastech, Sherbrooke, Quebec, a division of the MI Integration Group that supplies injection molded interior and sealing parts to the automotive industry.

Plastech’s Lubi™ wall-mounted solar air heater, manufactured by Enerconcept Technologies, Magog, Quebec, is a high-efficiency solar collector rated at an 80.7 efficiency by the Canadian Standards Association (CSA-International). With darker colors, the collector can provide air temperatures of up to 81°F (45°C) above ambient outdoor temperatures and maximum outputs of 254-Btuh/ft2 (800-watts/m2). Since its installation at Plastech in late 2010, a 45°F (25°C) was measured on sunny days, a performance which Enerconcept said was previously unheard of in the solar industry for a white collector. The company said Lubi’s performance statistics are certified by the National Solar Test Facility (NSTF), a Mississauga, Ontario-based third-party laboratory that tests and rates solar technologies under controlled temperature/sunlight/wind and is sanctioned by the Solar Rating and Certification Corp. (SRCC), Cocoa, Fla.

“For Plastech, 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,” said Stephane Tremblay, general manager, Plastech.

Using dark walls as an absorber is recommended for optimum solar performance efficiency; however, the inherent performance disadvantages of Plastech’s light colored wall were offset with a 40 percent larger collector. After 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. Besides $6,000 in annual savings, the collector reduces Plastech’s CO2 emissions by 15 tons/year.

How It Works

Installed by Sherbrooke-based contractor, RTSI, the 90 x 24-foot-high wall-mounted solar collector has clear glazing that from a distance appears like windows. Sunlight radiates through the glazing where it is absorbed by the building’s corrugated steel wall. The Lubi’s efficiency is attributed to its patented design featuring 906 perforations per 3 x 1-foot-long (900 x 320-mm) 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. Unlike wall-mounted solar collectors that suffer significant heat loss through the glazing or metal facade, Enerconcept said the panel’s airflow cooling minimizes heat loss and increases efficiency.

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 via ductwork. Heated air is distributed via 36-inch-diameter DuraTex™, a non-porous fabric air dispersion system manufactured by DuctSox, Peosta, Iowa. The lightweight duct has no diffusion through the plant until it enters the shipping area where the high-throw array of linear diffusion orifices located at 6 o’clock 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 69°F (21°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 molding process is ample 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 can’t satisfy the shipping area’s set point temperatures, then a propane gas-fired heater, by Reznor, Memphis, Tenn., acts as a back-up source. Typically the solar collector and heat recovery supply all the shipping area heating needs and therefore reduces the firm’s gas-fired heating consumption to near zero, according to Yann Rouleau, plant manager.

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

Leprohon, a Sherbrooke, Quebec-based mechanical contractor that offers design, installation, and service to industrial, commercial, and residential customers, solved several challenges as the project HVAC contractor. Leprohon custom-fabricated sheet metal ductwork to circumvent 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 south side optimum solar exposure location.

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

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

For more information, visit www.enerconcept.com.

Publication date: 11/21/2011

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