One of the largest and most extensive solar air heating projects in the world has now been completed for the United States Military base at Fort Drum, in upstate New York. The project is extremely significant in terms of the sheer agnitude of energy and CO2 savings, and it shows the tremendous potential for solar thermal when it is deployed on a large scale.
In the fall of 2005, the Army Corp of Engineers at the base commissioned a multimillion dollar retrofit program to upgrade 27 of their vehicle maintenance buildings. Conserval Engineering Inc. of Toronto, Ontario, Canada, and Conserval Systems Inc. of Buffalo, NY, worked closely with the military base over the two-year duration of the contract in the design and installation of the SolarWall® transpired collector systems. SolarWall® systems had previously been installed at six other U.S. military bases. This project was one of the reasons why the U.S. Corp of Engineers, in 2006, identified the transpired collector as one of two cost effective technologies ideally suited for military buildings, such as vehicle maintenance garages.
Typical military buildings, such as vehicle maintenance garages, hangars, and warehouses are ideal for solar air heating. They have a high ventilation load which represents an enormous energy expenditure given the tremendous volume of air that has to be continuously brought in and then heated over the entire heating season. As well, these buildings have large wall surfaces available, which makes it easy to integrate a SolarWall system into the exterior façade.
For the Fort Drum project a variety of colors were selected for the 50 SolarWall® systems, including: black, brown and blue-grey. The objective was to complement the existing color schemes of the buildings.
The SolarWall® panels were mounted 6” to 10” from the exterior wall to create an air cavity. The heated boundary layer is drawn off the panels and through the perforations into the air cavity behind. From there, it is either directed into the HVAC units or into the building through a fan and ducting system. Conserval Engineering customized the interior heat distribution for optimal performance in each building. In total, 99 fans are being used to deliver 300,000 cfm of air. As well, new air makeup fans and distribution ducting were installed to improve the ventilation air in some of the older facilities. In some cases the air was brought in through wall fans, in other cases through roof mounted fans or HVAC units. The issue of destratification was present in many of the buildings; the temperature at the ceiling of tall hangars was as much as 20 F (12 C) hotter than floor temperature prior to the installations. The SolarWall® ducting systems were designed to minimize the stratified ceiling heat, resulting in additional energy savings.
The $3 million that was allocated to the turnkey SolarWall® project will allow the base to generate a minimum of 4MW of thermal energy. It will displace 2,000 tons of CO2 annually by reducing 44,000 million BTU/h (46,000 GJ) of natural gas each year. From a cost and energy production perspective, these values illustrate the financial attractiveness of the SolarWall® solar air heating system. The SolarWall® project at Fort Drum also created ten man years’ worth of work, which highlights the local job creation benefits of solar.
One of the SolarWall systems (4,100 sq. ft.) on Building 91 is currently being monitored by the NREL (National Renewable Energy Laboratory). The preliminary results from one month of monitoring were calculated as follows:
Building 91 @ $0.90 /therm,
Boiler efficiency 70%
Solar energy gain - $36/day
Natural gas savings for the one SolarWall system for one month were approximately $1000