Wednesday, August 2, 2006
August 2 was a very hot day, with very high electric prices (fig 1). The CUE Optimizer took advantage of the day’s lowest prices by recommending an OPT temperature setpoint of 65°F during the unoccupied early morning hours. The cool air was absorbed by the building’s thermal mass and released gradually during the day to reduce HVAC electric demand during high-priced hours. The Optimizer found opportunities to shift cooling load among occupied hours as well (fig 2).
By employing this strategy, the CUE Optimizer reduced the HVAC electricity consumption by 11% (fig 3) and expense by 21%, without compromising comfort.
Outside Temperature & Electric Market Price – Figure 1 CUE uses forecasts of outside temperature, humidity, and solar radiation to anticipate building cooling loads. Forecasts of volatile hourly electric market prices create a CUE arbitrage opportunity – we shift cooling loads to low-priced hours using use building thermal mass. We execute this shift by sending OPT temperature setpoints to the building automation system from our central servers. |  |
 | Zone Temperature Setpoint Control – Figure 2 NSU (Night Set-Up) defines the normal temperature setpoints (or thermostat settings) that are programmed into the building automation system. Typically the setpoints are set up at the end of occupancy – thus shutting down HVAC operation – and set down in the early morning – to restart HVAC operation in advance of building occupancy. OPT (OPTimal) defines the setpoints recommended by CUE to reduce a building’s HVAC expense. |
HVAC Electricity Consumption – Figure 3 This final graph shows the practical effect of CUE thermal mass control strategies on HVAC system electric consumption. The CUE Optimizer reduced the HVAC electricity consumption by 11% and expense by 21%, without compromising comfort. |  |