Page 132 - Zero Net Energy Case Study Buildings-Volume 1

ZERO NET ENERGY CASE STUDY BUILDINGS, VOL. 1 OBSERVATIONS
ability for UC Merced, reports that some of the meters used were found to be off by 300%, simply
due to faulty equipment.
In the case of the IDeAS Office Building and Packard Foundation Headquarters office building, the meters did not match the current transformer (CT) ratios in the electric circuit. That is, the CTs of the meters were too large to accurately measure the relatively small amount of current in the wires, rendering the measurement inaccurate. Using meters with properly sized CT’s or higher quality meters that can pick up the small loads solves this problem and results in accurate data.
This effect was detected in these two case study buildings by comparing the energy flow at the site utility meter and the energy production meter at the PV system, both of which are highly accurate metering systems. The net difference should equal the energy use as reported by the building meters. The initial inaccurate readings by the meters were detected as a result of this comparison, which also later confirmed the accuracy of the metered data after the metering system was overhauled. Reconciling the building sub-metering system with the utility metering system is thus a critical step in this aspect of the commissioning process.
Finally, the Building Management System (BMS) is usually used as a source of energy use data, but this introduces another source of possible data collection problems. The programming of the BMS is often done by software engineers who are not experienced with building energy systems and what how to organize the most useful method of reporting all the data. This programming can also be peculiar to the individual software engineer, which can make later troubleshooting difficult. Data reporting problems were experienced in some case studies, most notably in the Watsonville Water Resources Center, where data was initially lost due to a programming-based issue and where plug load data could not be deciphered from the data. This case demonstrates the need for a consistent approach, communication between the programmer and the design team, clear and transparent documentation, and system validation.
The common lesson from these experiences is that the energy metering system itself requires a commissioning process and the quality of the data that is being reported must be carefully assessed. Once this initial period of metering sub-system “tuning” is completed, the data collection and analy- sis can be started.
Monitoring, Diagnosis and Correction: Creating “Actionable” Information
When the building energy use data streams are deemed to be accurate and are compiled over a period of time, there is a lot of complex information that needs to be synthesized into a form that is “actionable” by the building manager. This includes reports about specific systems and components and, ideally, programmed warnings about anomalies or changes in the patterns of energy use. Clients and owners are typically wary of the time required for this on the part of building managers, and rightly so, especially if they are not trained to deal with the form of the data reporting. It is not useful for the building manager to receive, literally, many thousands of fault alarms over the course of a year, as has been reported in the literature. The need is rather for reports about specific systems and components and, ideally, programmed warnings about anomalies or changes in patterns of energy use that are clear and “actionable.”
At UC Merced, two postgraduate assistants were assigned the task of monitoring the data, orga- nizing reports and alerting facilities staff to such changes in use patterns. This monitoring called attention to the failure of one of the four exhaust fans, for example, as reported in the case study for the Science & Engineering Building I. This would otherwise have gone unnoticed for a long period of time, and points to the need for automated reporting systems for larger facilities, few of which have the luxury of high-quality, low-cost student assistance.
As noted in the Packard Foundation Headquarters case study, the client’s in-house IT team developed a software package that monitors the control systems of all the different energy- related building systems, records the data being produced and presents all the information in a user-friendly format for the building manager. This software “sits on top” of the set of all control systems, including the BMS, and allows the building manager to receive alerts from any part of the building infrastructure, as well as to change operational schedules from automatic window- blind operation to room temperature and lighting settings for common rooms—all with the click of a mouse.
This is a developing area for software commercialization, with similar ver- sions currently available on the market to typical building owners. Software
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Zero Net Energy Case Study Buildings: Volume 1