Many people have been joining the “green” movement to some degree, that is, searching for alternative energy sources as a way to reduce pollution and other problems that can result from burning fossil fuels. But the recent surge in energy prices has produced an additional incentive, driving many to also look for green technologies as a way to reduce costs.
Kate Murray, town supervisor in
Town officials chose the town hall site for its central role in community affairs and its ability to showcase solar power not just for the return air fans for the building, but also for the DC, or direct current, lighting in the supervisor’s office and a conference room. Ron Masters, commissioner of conservation and waterways for the town, was familiar and confident with Nextek Power Systems, a supplier of DC power networks and experienced in facilitating alternative energy projects.
Paul Savage, president of Nextek, says the project reveals the convergence of two trends in today’s facility power. First is the advent of distributed power generation, such as the solar installation at
Nextek developed “DirectCoupled” technology that establishes a DC bus in the building. This eliminates electrical losses inherent in the inverter. According to Savage, a typical solar installation is only about 89 percent efficient because of those losses. But his DirectCoupled technology improves that figure to 99 percent, Savage claims. This bus connects to all of the DC electronic loads, eliminating losses at that point as well, because conversion from AC to DC is no longer required.
There is yet another source of loss in an HVAC system—the variable frequency drives (VFDs) that run devices such as return air fans and compressors. A typical VFD contains a rectifier that takes the incoming AC power and changes it to DC. The electronics in the drive then transform the DC into a pulsed simulation of AC to power and control the motors.
This technology has been proven to greatly reduce energy consumption by these motors. But, those rectifiers also induce losses in the system. Nextek worked with local
At night or during periods of low solar output, the Nextek Power Gateway seamlessly reverts back to grid power until the renewable source is available again. Because the system is DirectCoupled, it is not subject to “anti-islanding” regulations that require conventional grid-tied solar systems to shut down in the event of a grid failure. The Power Gateway also enables load shaping and peak mitigating with its advanced metering, monitoring and controls capabilities. During daytime peak usage, the HVAC system will be powered primarily by the solar PV array, reducing the burden on the local utility.
The anti-islanding regulations come into play, says Savage, when the distributed generator puts electricity back on the grid. “Some people look at these alternative generating sources as a backup to when power from the grid goes down. So, if you have a unidirectional power setup such as this one, then you don’t have to shut down when the grid goes down, maintaining a little independence.”
The solar energy system was funded through $260,000 from the settlement of a clean air lawsuit against a power company in 2003.
Under the settlement, the power company was required to pay $2.1 million for air pollution mitigation projects in
“Many people aren’t aware of commercial HVAC operations and the energy-saving opportunities with these motor-driven applications,” says Masters. “Demonstrating the value of these types of installations is important to furthering public understanding, and we see many other flat-roofed buildings that could be using and benefiting from this technology.”
Variable frequency drives, which act as controllers to protect motors and improve motor performance, have long benefited HVAC fan and pump applications, but
“The success we’ve had with Allen-Bradley PowerFlex drives is an efficiency we didn’t anticipate when we started the project,” says Masters. “With the variable frequency drives, we can set and throttle back to idle the system to match our energy needs, and the exposed front end of the drive adds additional economy to the system.”
Townspeople and officials are pleased with the new system, and it is setting an example across
With the success of the town hall installation, Masters anticipates future successes in upcoming “green” applications.
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