Instrumentation for Evaluating Integrated Lighting System Performance in a Large Daylighted Office Building

Electric lighting consumes for 30% to 50% of electrical energy used in large commercial buildings, and has significant impact on cooling energy requirements. The integration of daylighting with electric lighting to provide ambient illumination and providing task lighting separately at each workstation is an attractive strategy for energy conservation. Energy savings come from proper control of the electric lighting system in response to available daylight. Building-level energy use measurements are generally insufficient to determine how well a building is operating. Detailed measurements of energy used by separate building components are needed to understand how a particular building system is operating.

This paper describes instrumentation used to monitor the electrical energy consumption and illumination levels in a recently completed 56,000-m² office structure in the SansFrancisco Bay Area. Interfacing of the temperature, electrical, and illumination measurements to the dataloggers is described. Data acquisition in this occupied building presents several challenges. Researchers needed to make measurements quickly, with minimal disturbance to occupants by equipment and wiring, in four quite different daylighting zones separated by large distances—all on a limited budget. We give a brief description of the building and the issues to be addressed by this monitoring project. We then describe the instrumentation installed in the building to measure both lighting levels and electric power consumption. Finally, we present and discuss typical results that can be obtained with this instrumentation.