Page 162 - Zero Net Energy Case Study Buildings-Volume 3

CASE STUDY NO. 17
CENTRAL ENERGY FACILITY OPERATIONS CENTER
Energy Use—Actual Measurement and Comparison to Modeling Results
Metered energy use was recorded for the basic categories of electrical use (lighting, plug load and building equipment) and the heating and cooling energy as separately measured via flow meters. The electrical energy use includes the control room for the campus energy supply, which is a substantial power draw because of its 24/7 operation.
The building used approximately 151.6 MWh during the period from 5/2016 to 4/2017, which equates to an EUI of 54.1 (kBtu/sq.ft. per year). It is important to note that the EUI includes not only the administrative office building but also the intensive process loads of the central plant control room and server room that are associated with larger campus operations.
Energy Production versus Energy Use: Zero Net Energy Performance
As noted above, the solar PV system installed on the canopy structure was not determined by the building energy use data, but simply fills all the available space on the canopy. The system produced almost 290 MWh of energy over the course of the year from 5/2017 to 4/2018, which is almost double the actual annual energy use measured for the building. So, even with half of the solar PV system installed on the canopy, the building easily achieves ZNE.
Post Occupancy: Observations and Conclusions
Post Occupancy: Natural Ventilation
Reliance on user operation of the natural ventilation for fresh air and cooling is questionable, even with the most attentive of user groups. Finely tuned operation that is responsive to outdoor air conditions and efficiently reduces the cooling load is best accomplished through automated, continuously-operating window actuators and an integrated operating system. Deep energy sav- ings are possible with this type of system. On the other hand, user-operation provides the oc- cupants with a sense of control of the internal environment and comfort conditions. This is the typical discussion of pros-and-cons among designers and clients when evaluating natural venti- lation as a cooling design strategy.
In the case of this building, the choice of user-operated windows was driven by the perceived extra cost of an automatically operating system and the state of that technology at the time this building was designed. The users also favored the option of manual control only since they felt invested in awareness of the energy performance of the building.
Post Occupancy: Occupant Behavior
The initial campus planning design decisions—positioning the building to terminate a long axis from the center of campus and create a strong visual presence at that termination—were more successful than anticipated. The building has high numbers of visitors, both from the campus and abroad, attracted by the importance placed on the energy management and sustainability aspects of the entire CEF. The planning concepts and the design of the facility is at least partly responsible for this response. (There was even a request made to Stanford to allow a wedding to take place in the outdoor amphitheater at the office building’s courtyard space, based on the mission of the CEF project and its realization.)
Campus classes and meetings are regularly scheduled in the office building’s communal spaces as well. The importance of such interest in these ZNE buildings should not be underestimated, as they also serve as educational demonstrations of forward-thinking design principles and a “realistic” approach to ZNE building design.
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Zero Net Energy Case Study Buildings: Volume 3