The California Smart Grid Center (CSGC) recently did a demonstration test of a Wireless Pneumatic Thermostat (WPT) which, according to WPT maker Cypress Envirosystems, showed significant reductions in cost, time, and disruption when retrofitting legacy buildings for Smart Grid Auto-Demand Response connectivity.
The patent-pending hybrid pneumatic and digital technology employed by the WPT targets existing buildings. It is designed to let them participate in peak load reduction and energy efficiency strategies previously impractical because of the long investment payback and disruption to building occupants incurred by conventional retrofitting of controls.
The CSGC test involved about 6,000 sq-ft of office space at Sacramento State University. Prior to the retrofit, the offices used non-communicating pneumatic thermostats for control of heating and cooling. These old thermostats couldn't be set remotely, nor could they interface with the Smart Grid for Auto-Demand Response. Cypress says retrofitting them to modern communicating digital thermostats using conventional technology would have been extremely costly, with a payback period of five years or longer. It would also require opening up walls and ceilings, with significant disruption to building occupants.
The installation at Sacramento State University took about two hours rather than the several days needed for conventional controls. Once installed, the thermostats enabled remote control and monitoring of zone setpoint, temperature, and branch pressure (heating or cooling demand) via an operator station. The system can also interface with existing automation systems using BACnet, and has a built-in interface compliant with the OpenADR protocol developed by the U.S. Dept. of Energy's Lawrence Berkeley Laboratory, which allows communication with utilities for Auto-Demand Response. This interface allows buildings to automatically curtail electricity use during periods
of high demand (by increasing the setpoint temperature for thermostats, for example).
Cypress says similar large-scale retrofits using the WPT, involving over one-million square feet, have confirmed each WPT can shed up to 1kW of peak load, and reduce HVAC energy use by up to 30%.
“Most commercial buildings built before 1995 uses pneumatic control systems. This equates to about 70% of the existing commercial building space, or over 60 billion sq-ft, which cannot be easily connected to the Smart Grid. We designed the WPT specifically to address this problem and also to deliver energy savings.” said Harry Sim, CEO of Cypress Envirosystems.