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Solar air heating helps aircraft manufacturer soar to new green heights

Bombardier Inc. has been a corporate role model of energy efficiency for years, but the world's third-largest aircraft manufacturer recently took initial steps toward incorporating even more “green” technology by using a solar-energy retrofit to preheat outdoor air at its Mirabel, QC, industrial building.

Previously, solar was not a preference because the Montreal-based, publicly held company’s two-year payback selection criteria limits the consideration of many alternative-energy concepts.

At the company's 40,000-sq-ft research and development facility at the Mirabel Airport, Bombardier's plant engineering group authorized the recent installation of a Lubi, a wall-mounted solar air heater manufactured by Enerconcept Technologies that is amid a two-year payback for that application. The solar air heater supplements the existing natural gas-fired make-up air unit by preheating wintertime outdoor air for the 52-ft tall, hangar-style building as required by ASHRAE Standard 62-mandated commercial-building requirements.

“In 2008 we analyzed all types of equipment with a goal of reducing our electric and natural gas consumption,” said Serge Dumont, P.E., Plant Engineering and Tooling Manager, Commercial Aircraft Division—Bombardier. “We decided only projects with a two-year payback or less would give us the most effective return on investment.”

The manufacturer’s factory engineers supplied Dumont's engineering team with sizing, output calculations and other design assistance. According to National Solar Test Facility, a Mississauga, ON-based third-party laboratory that tests and rates solar technologies under controlled temperature/sunlight/wind (and which is sanctioned by the Solar Rating and Certification Corp. of Cocoa, FL), the Lubi is the world’s most efficient solar product.

The 145-ft x 12-ft solar collector aesthetically simulates architectural windows and covers about 25% of the 7,600-sq-ft masonry wall. It is delivering an annual 16-ton reduction of CO2 emissions and a C$5,000 natural-gas savings. Over the course of its 20-year (minimum) lifecycle, the natural-gas savings is expected to rise to more than C$100,000 when considering inevitable fossil-fuel price escalations. Lifecycle CO2 reductions are estimated at 320 tons.

In an ideal setting, the solar air heater could have yielded an even greater payback if not for several site challenges including:

• The collector is mounted on a west wall instead of an optimum south wall exposure, which was decided against due to a future building project that is expected to partially block sunlight on the south wall;
• A larger solar collector could have provided more heating, however, the Lubi is sized to provide the capacity of preheated outdoor air required by the existing 7,000 cfm rooftop make-up air unit;
• A larger solar air heater also could have supplied a second HVAC system, however, its east-side location required a rooftop ductwork addition that was not cost-effective; and
• The building’s indoor temperature setpoints are an energy-conserving 66°F (19°C), which requires less solar heating capacity than higher building setpoints.

The 66°F building temperature is part of several company-wide green strategies Bombardier employs.

“We have saved a lot of natural gas by lowering the temperature in our building by just one degree,” Dumont said.

Other strategies include energy conservation through microprocessor-controlled lighting zone programming that provides light only when workers are present. The company also stores energy during off-peak hours so as not to surpass higher energy rate allowances by local utilities during peak times.

The solar strategy is new for Bombardier, although it has been used twice previously, both with wall-mounted solar collectors. Other solar methods, such as solar water heating and photovoltaic do not yet reach the company’s two-year payback standard, according to Dumont.

The wall-mounted solar air heater, which was recommended by a Bombardier supplier with performance data later verified by Dumont’s engineering department, potentially supplies 36°F–45°F (20°C–25°C) above ambient depending on outdoor temperature and available sunlight. It has a 7-in. space between the glazing and a 26-gauge sheet metal facade attached to the wall and is custom painted to match the building’s blue, decorative striping below. Changing the wall color from beige to the darker blue inside the collector helps increase solar-radiation absorption by 40%. The solar collector also increases the R-value of the wall portion it covers from R-20 to R-40, which in turn helps reduce heat loss through the building wall.

The solar air heater’s 18% higher efficiency versus other solar air heaters’ collectors is due to its patented translucent perforated panel technology. Each 3 ft x 1 ft (900 mm x 320 mm) polycarbonate panel has 906 perforations. Unlike wall-mounted metal solar collectors that suffer significant thermal losses on their exterior panel surfaces, the solar collector’s panels greatly reduce thermal loss because of their transparency and the cooling effect of outdoor ambient air being drawn through the perforations by the building’s HVAC air handling system. Wind and rain do not affect the solar collector's performance.

The solar collector’s rising air culminates in a sheet-metal mixing box fabricated by the project’s ventilation contractor, J.P. Lessard Canada Inc. of Montreal, QC. The box also features a bypass damper manufactured by T.A. Morrison Co. of Stittsville, ON, which is controlled by a Honeywell building automation system for the facility. Connecting the mixing box to the rooftop HVAC unit is a 30-ft long, 32-in.-diameter sheet-metal duct. A black weather-resistant exterior coating provides optimum solar-radiation absorption and negates the need for duct insulation.

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