Page 43 - Zero Net Energy Case Study Buildings-Volume 3

THE J. CRAIG VENTER INSTITUTE
CASE STUDY NO. 12
Energy Production versus Energy Use: Zero Net Energy Performance
2015 was the second full calendar year of operation and the resulting performance data shows that the building is short of ZNE by about 20%: 964 MWh used compared to 800 MWh produced on-site. The solar photovoltaic system performed as expected. It was the energy use, which was higher than modeled by nearly 30%, that caused the building to perform less than ZNE. (See the final subsection, “Post Occupancy—Observations and Conclusions”, for a discussion of the possible causes of the higher energy use than anticipated.)
As the solar PV performance chart on the facing page indicates, a dip in production during the second quarter prevented the building from getting close to ZNE performance. Even without this behavior in the following year, 2016 data showed a similar general pattern with a second year of net-negative performance.
The consistent pattern of energy use exceeding energy production by the same relative fraction means that the cumulative difference grows more negative, as reflected in the chart on the previ- ous page.
Post-Occupancy: Observations and Conclusions
The intent of this project was to “do the experiment” and determine if it is possible to design and build a ZNE laboratory, something that had never been done. At the end of two years, given an analysis of the design and performance of the JCVI facility, the answer appears to be affirmative given possible corrective actions, but the data has not yet proved it conclusively.
Certainly, as a great advance in laboratory design, the goal of establishing the model for The Laboratory of the 21st Century is met. The original target for the ZNE design was EUI = 70, compared to an energy-efficient Labs21 design of EUI = 270. The actual measured performance for 2015 is EUI = 73.8, close to the target. Falling just short of ZNE soon after occupancy is not surprising, given the adjustments and tuning of the building systems that normally are necessary.
Also, the initial “stretch goal” of EUI = 70 was essentially achieved, but given the size of the solar array that was eventually installed (producing 800 MWh in 2015), the EUI would have to be lower by another 10 units (kBtu/sq.ft.) to reach the ZNE objective. This is certainly achievable in the next few years, given some of the issues discussed below. The “experiment” proved to be successful by one measure—the initial target EUI was essentially achieved, the path to ZNE with this building is now known and all of the design innovations can serve as a good model for the design of future research laboratories.
Post-Occupancy: Equipment
The most innovative strategy to reduce equipment energy consumption is the use of shared [-80°C]-freezers in a dedicated room for that equipment. This enabled the use of water-cooled [-80°C]-freezers, a much more energy-efficient type, as well as a general reduction in the num- ber of freezers required. This programmatic change required the support of the research scien- tists, which was given during the planning stages.
The [-20°C]-freezers, though not water-cooled, were also intended to be purchased new as energy-efficient models. When the building opened, some scientists did not secure the purchase of the new [-20°C]-freezers for budgetary reasons and simply moved their existing freezers into the new location. The expected reduction in energy use for equipment was therefore only par- tially achieved initially, but will likely be fully realized in the future as this particular equipment if replaced..
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