Page 108 - Zero Net Energy Case Study Buildings-Volume 2

CASE STUDY NO. 10
WEST BERKELEY BRANCH LIBRARY
The metering setup did not permit separate data reporting for heating, cooling, ventilation and pump energy use. Hence the energy use categories indicated for the energy modeling results cannot be separately reported for the measured results, and therefore compared. The charts showing measured data combine these four categories into the single category of “Mechanical”.
The total energy used by the building in this year was 63,000 kWh, or an EUI = 23.1 kBtu/sf per year. This total is approximately 15% more than the design target and 30% more than that indicated by the energy modeling. The whole building energy model was not calibrated to actual weather and occupancy conditions, but some reasons for the difference are the incomplete com- missioning after the building was occupied, as well as some user behavior issues that arose. (See Post Occupancy: Observations and Conclusions, below.)
Energy Production versus Energy Use: Zero Net Energy
While the energy use was higher in this first year of occupancy than the design target, the over- sized solar PV system provided the cushion needed to exceed the goal of ZNE performance. The system performed as specified in the submittal by the solar subcontractor, providing 75,000 kWh during the year, about 20% more than the energy used in that period.
The Cumulative Energy Balance chart for 2014 illustrates the net positive performance of the building, with the net total on-site energy balance at the end of that one-year period still positive on the production side.
Post Occupancy: Observations and Conclusions
Perhaps the most successful aspect of this case study project is the fact that the new building incorporates systems and features that result in a ZNE performance within the fixed first-cost budget established for the project. The project cost budget, established by a professional con- sulting team years earlier and never envisioning any more than a basic LEED-Silver building de- sign, was absolutely fixed by the public bond measure—no additional funds would be available. Yet, the design team and the client worked successfully together to expand the project goal to a zero-net-energy building and to achieve that goal within the cost budget, at the same time with all other project requirements fulfilled.
The project experienced problems and issues on the path to this success, however, not unlike the other successful case study buildings. There are still common technical issues, but for public projects there are some differences created by the public process and occupant behavior that can affect the final design and the actual performance.
Post Occupancy: Controls and Monitoring
The need for a master controls integrator became obvious at the start of commissioning when the relative complexity of the sequence of operations of the passive ventilation system became apparent, along with the other aspects of the mechanical systems operation. Large parts of this system are not normally centrally controlled by a conventional building management system (BMS), yet the BMS controls technician was required to program the system to operate win- dows, skylights, shades, backup ventilation fans, as well as to respond to inputs from the rooftop weather station and the interior CO2 sensors.
As noted in the controls system description above, the BMS vendor was given a change order to add the solar PV system, the small metering system and the energy dashboard to the central control system. Except for the metering system, which uses a Modbus communication protocol, these added operating control systems use BACnet protocol.
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Zero Net Energy Case Study Buildings: Volume 2