Page 89 - Zero Net Energy Case Study Buildings-Volume 1

WATSONVILLE WATER RESOURCES CENTER
CASE STUDY NO. 4
Energy Production versus Energy Use: Zero Net Energy
Measurements of the energy used by all of the systems in the building were started in 2010 and preceded the installation of the solar photovoltaic system in 2012. Due to the separate sources and timing of the recorded information, the energy use and energy production results reported in this case study are not coincident in time. They nevertheless provide a good comparative set of data for each, particularly since the weather patterns for the two different years were very similar.
Verification that the Water Resources Center is actually performing at ZNE is not possible to confirm exactly at this time because of the service and metering issues discussed previously. As noted, the City chose the most cost effective approach for bidding and purchasing the PV sys- tem, which was to enlarge the system and include additional electric loads of other city facilities and equipment, including a very large water recycling pump at the adjacent Water Operations Center. Isolation of the Watsonville WRC building loads in relation to the energy production of the PV system cannot be done at the same level of certainty as the other case studies in this monograph.
The graphs on the facing page show the performance of the combined building/pump loads and both arrays for the PV system. The upper graph shows that the roof-mounted array is providing about 70% of the first-year demand for the building. The lower graph indicates a large demand from the recycling pump, which drew a large amount of power from the roof panel array.
Post-Occupancy: Controls and Monitoring
Monitoring of the building energy system and data measurement began with initial occupancy near the beginning of 2010. However, it was soon discovered that energy data was being re- corded but not stored and six months of data were lost as a result. The BMS system was set for recording too detailed a level of data, inconsistent with the memory/storage capacity of the system. With a programming reset, the system began recording data in July 2010.
The systems were shown to be operating as planned. A failure of the electric DHW heater, caused by a manufacturer’s issue unrelated to the ZNE design, caused a switch to a gas-fired DHW heater.
Post-Occupancy: HVAC
The HVAC system in general has been operating as designed and no significant problems were apparent in the first year of operation. The office and the laboratory wings have proven to be comfortable thermally and the total energy use for heating, cooling and ventilation have been approximately what was expected.
Post-Occupancy: Acoustics
A common complaint among occupants of high performance buildings is the poor room acous- tics. The Water Resources Center is no exception: the hard surfaces with little acoustic absorp- tion material combined with the absence of the “white noise” of operating equipment such as fans and air blowing through ductwork and diffusers have led to post-occupancy reports of poor acoustic quality. This can be mitigated by installation of absorptive acoustic materials and atten- tion to standard acoustic design for certain noise sources such as footfall, telephones and office equipment.
Large ceiling fans were installed in the office spaces as part of the ZNE design strategy, since gentle air movement allows a sense of comfort at higher air temperatures. However, the contrac- tor installed a generic controller instead of the manufacturer’s controller and the result was very noisy operation. The result is that occupants appear not to be using the ceiling fans as intended, negating the intended effect and likely resulting in higher energy use for cooling since higher temperature setpoints for cooling could not be used.
Post-Occupancy: General
The principal issue that emerged during the post-occupancy period was the inability to obtain the complete set of measurement data needed to evaluate the building’s energy performance. Ad- ditional work on the BMS system would no doubt resolve this problem. In general, however, the building’s overall total energy use appears to be less than that indicated by the design modeling and consistent with the goal of ZNE performance. This is expected to be confirmed once the data issue is resolved.
Zero Net Energy Case Study Buildings: Volume 1
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