Monitoring Based Commissioning: Benchmarking Analysis of 24 UC/CSU/IOU Projects

Mills, Evan ; Mathew, Paul

Lawrence Berkeley National Laboratory

关键词: Calibration;    Heating;    Information Systems;    Monitoring;    32;   

DOI  :  10.2172/961599
RP-ID  :  LBNL-1972E
RP-ID  :  DE-AC02-05CH11231
RP-ID  :  961599

美国|英语

来源: UNT Digital Library

【 摘 要 】

Buildings rarely perform as intended, resulting in energy use that is higher than anticipated. Building commissioning has emerged as a strategy for remedying this problem in non-residential buildings. Complementing traditional hardware-based energy savings strategies, commissioning is a 'soft' process of verifying performance and design intent and correcting deficiencies. Through an evaluation of a series of field projects, this report explores the efficacy of an emerging refinement of this practice, known as monitoring-based commissioning (MBCx). MBCx can also be thought of as monitoring-enhanced building operation that incorporates three components: (1) Permanent energy information systems (EIS) and diagnostic tools at the whole-building and sub-system level; (2) Retro-commissioning based on the information from these tools and savings accounting emphasizing measurement as opposed to estimation or assumptions; and (3) On-going commissioning to ensure efficient building operations and measurement-based savings accounting. MBCx is thus a measurement-based paradigm which affords improved risk-management by identifying problems and opportunities that are missed with periodic commissioning. The analysis presented in this report is based on in-depth benchmarking of a portfolio of MBCx energy savings for 24 buildings located throughout the University of California and California State University systems. In the course of the analysis, we developed a quality-control/quality-assurance process for gathering and evaluating raw data from project sites and then selected a number of metrics to use for project benchmarking and evaluation, including appropriate normalizations for weather and climate, accounting for variations in central plant performance, and consideration of differences in building types. We performed a cost-benefit analysis of the resulting dataset, and provided comparisons to projects from a larger commissioning 'Meta-analysis' database. A total of 1120 deficiency-intervention combinations were identified in the course of commissioning the projects described in this report. The most common location of deficiencies was in HVAC equipment (65% of sites), followed by air-handling and distributions systems (59%), cooling plant (29%), heating plants (24%), and terminal units (24%). The most common interventions were adjusting setpoints, modifying sequences of operations, calibration, and various mechanical fixes (each done in about two-thirds of the sites). The normalized rate of occurrence of deficiencies and corresponding interventions ranged from about 0.1/100ksf to 10/100ksf, depending on the issue. From these interventions flowed significant and highly cost-effective energy savings For the MBCx cohort, source energy savings of 22 kBTU/sf-year (10%) were achieved, with a range of 2% to 25%. Median electricity savings were 1.9 kWh/sf-year (9%), with a range of 1% to 17%. Peak electrical demand savings were 0.2 W/sf-year (4%), with a range of 3% to 11%. The aggregate commissioning cost for the 24 projects was $2.9 million. We observed a range of normalized costs from $0.37 to 1.62/sf, with a median value of $1.00/sf for buildings that implemented MBCx projects. Per the program design, monitoring costs as a percentage of total costs are significantly higher in MBCx projects (median value 40%) than typical commissioning projects included in the Meta-analysis (median value of 2% in the commissioning database). Half of the projects were in buildings containing complex and energy-intensive laboratory space, with higher associated costs. Median energy cost savings were $0.25/sf-year, for a median simple payback time of 2.5 years. Significant and cost-effective energy savings were thus obtained. The greatest absolute energy savings and shortest payback times were achieved in laboratory-type facilities. While impacts varied from project to project, on a portfolio basis we find MBCx to be a highly cost-effective means of obtaining significant program-level energy savings across a variety of building types. Energy savings are expected to be more robust and persistent for MBCx projects than for conventionally commissioned ones. Impacts of future programs can be maximized by benchmarking energy use and targeting the commissioning towards particularly energy-intensive facilities such as laboratories.