Figure 1: Contour plot showing the various operating stages of occupancy sensors described in the case study.
Data visualization for buildings is the display of a rich set of variables and parameters that managers can use to verify the energy savings of energy- efficient technology and identify malfunctions in building equipment or problems with operating strategies. Effective data visualization depends on having graphic presentation formats that reveal the phenomena relevant to the building's performance. A research project at the Center for Building Science is aimed at developing data visualization techniques for improved building management. Buildings with energy management control systems as well as dedicated monitoring equipment in the San Francisco Bay Area provided the data for case studies of data visualization described here and in a detailed LBNL report available from the authors.
Today, engineering estimates of energy use and savings are the basis of most energy-efficient building design and retrofit projects. Unfortunately, in the field, these buildings often perform very differently from design estimates. Measured data can help verify energy savings, illuminate control and operational problems in a building, and test the accuracy of predictive methods. Such data are increasingly necessary in energy performance contracting, utility DSM program evaluation, and other activities where regulatory requirements or financial contracts require actual energy performance and costs to be documented.
Analysts now have considerable experience with the use of measured building energy and environmental data. However, the information is often in the form of point estimates, such as total annual or monthly energy use. In recent years, data collection has tended toward increasing disaggregation into shorter timesteps and specific end uses. The rapid development of data- acquisition technology, computer workstations, and graphics software has allowed detailed building energy data to be collected and visualized in new ways. This offers various benefits:
The following is a brief description of a case study that illustrates how data visualization can help building managers detect operating problems and optimize their facilities' energy use.
Case study: Recommissioning a Lighting System. Figure 1 shows a "contour plot" representation of energy consumed by a bank of lights in 1,000 m2 (10,000 ft2) of office space. Although somewhat difficult to read in this duotone version, the plot clearly indicates the on/off status of the lights and the energy consumed. This plot facilitated the detection of two problems. First, during the late evenings between 9/27/93 and 11/11/93, the lights were used more than would be expected. Building managers determined that this was due to the tripping of occupancy sensors by a security guard. As a result, the building owner installed manual-on/automatic-off switches. The second problem can be seen in the 18% increase in energy use after 1/10/94. On that day, an electrician accidentally reset the centrally controlled dimmable ballasts to their maximum settings. The increased light levels were not noticed by the building's occupants but were easily detected and corrected using the information provided by the contour plot shown here.
Currently, the project team is using commercial software to analyze monitored building data on the University of California, Berkeley, campus. The results are recorded in a specially designed database. Custom software developed in this project is being adapted for use in the Building Life Cycle Information System, BLISS (CBS News, Summer 1995). Members of the BLISS project will use data collected from Berkeley's Soda Hall to develop and calibrate a real-time operations model of a chiller, which will be added to the DOE-2 building energy simulation model.
(For further case studies and full-color images, see the Building Data Visualization for Diagnostics, Operator Feedback, and Performance Optimization by Steven Meyers, Evan Mills, and Allan Chen)
—Steven Meyers and Allan Chen
Please contact the authors to obtain a report (LBL-36704) with further discussion of data visualization and more examples of case studies.
Center for Building Science
(510) 486-6358; (510) 486-5394 fax
This work is funded by the Assistant Secretary for Energy Efficiency and Renewable Energy, Federal Energy Management Program of the U.S. Department of Energy, and by the University of California Energy Institute.
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