Demand Response - Load Shedding

Load Shedding

Electrical generation and transmission systems may not always meet peak demand requirements— the greatest amount of electricity required by all utility customers within a given region. In these situations, overall demand must be lowered, either by turning off service to some devices or cutting back the supply voltage (brownouts), in order to prevent uncontrolled service disruptions such as power outages (widespread blackouts) or equipment damage. Utilities may impose load shedding on service areas via rolling blackouts or by agreements with specific high-use industrial consumers to turn off equipment at times of system-wide peak demand.

In the effort to reduce the electric demand on power grids at critical periods, researchers developed a ballast prototype that quickly and reliably sheds the electric load within a building’s lighting system. A load-shedding ballast is an instant-start ballast with bi-level dimming and a built-in power line carrier (PLC) signal receiver for automated dimming response.

By dimming lighting via an electronic signal, the ballast reduces the current supplied to the lamps. A signal injector on the building’s lighting circuits controls the ballasts, eliminating the need for extra wiring. The ballasts respond to a signal sent by the utility or the customer’s energy management system, reducing power to the lighting by one third. Field studies showed that building owners could dim the lights by as much as 40% for brief periods of time without upsetting 70% of the building’s occupants or hindering productivity. Ninety percent of building occupants accepted the reduction in light levels when they were told that it was being done to conserve energy.

The new ballast system works on individual light fixtures, not on the main power grid. The system is recommended for new construction and remodeling and promises good return on investment in energy savings. In U.S.-based markets, the system has a three-year or less payback period for new construction. The ballast’s use has the potential to reduce U.S. peak electric demand by 20,000 megawatts. If used widely, it has the potential to help avoid blackouts.