Conducting electricity survey for an existing facility : a systematic approach

Abstract: For a sustainable future it is important to use Earth’s resources efficiently. One way of doing this is to reduce the energy use in buildings. For the end user, increased energy efficiency will also lead to economical benefits from reduced energy costs. The facility management of Saab AB in Järfälla expressed a concern regarding the electricity consumption during night in their facility. The question arose why the power draw during night was at its current level. Answering this question would increase the management’s understanding of the energy systems and if there are measures to implement increasing the facility’s energy efficiency. An outline for a systematic electricity survey was made inspired by audits developed by ASHRAE and the Swedish energy agency. The scope developed for the survey was set to only investigate one building, but doing this thoroughly. After measuring supplied power to the buildings on the compound systematically, one building was selected as the subject for the continued survey. The different energy systems of the building was identified and investigated, such as chillers, pumps, computers and lighting. Using both data loggers and electrical testing equipment the different systems were measured either over time or momentarily. The power draw for each of the systems was estimated using measurements, calculations, interviews and assumptions. The power draw during night for each system identified was presented both numerically in tables and as fractions of the total building electricity use in charts. It was found that the cooling related systems constituted over 40% of the power draw at night, and computer related activity was roughly 29%. This is due to the high amount of computer activity during night generating huge amount of heat that needs to be rejected via several cooling systems. Regulatory issues were found on cooling systems and the lighting control strategy causes high lighting levels during night. The occupancy hours were found to deviate from the defined hours in data charts, causing ventilation not to operate according to occupancy. Several measures were suggested to reduce the electricity use during night, ranging from increased maintenance and revising control systems to more capital intensive measures such as variable speed drive for pumps and chillers.