Page 133 - Zero Net Energy Case Study Buildings-Volume 2

Plug Loads
The plug load evaluation process, which is a mandatory step in any ZNE design process, was carried out in the usual manner: first, all plug loads in the existing building at PFA were carefully measured. These included all electrical energy use created by the equipment designed into the hands-on exhibits. This was followed by an evaluation of the expected expansion created for the new facility, including proposed new exhibits, support space and workshops, which have sub- stantial equipment loads. Finally, the inventory was reviewed for opportunities to reduce these loads through new purchases of energy efficient equipment (Energy Star, where applicable).
One of the benefits of the plug load study was the discovery that 33% of the total energy con- sumed was at night when equipment could ordinarily be shut down. The design team therefore included in the electric power design digitally addressable electric outlets using programmable circuit breakers, allowing control of each equipment item from a central location. By scheduling the power use appropriately, the off-hour plug load is now only 10% of the total.
It should be noted that the two commercial food service establishments, a café and a restaurant, function independently of the Exploratorium. These concessions use natural gas for cooking, which is billed separately by the local utility. Their electric energy is supplied through the Ex- ploratorium system and is billed separately. (Their overall energy use for heating and cooling, however, is included in that of the Exploratorium’s total annual energy use, since the radiant floor system is common to the entire building and not separately metered at the tenant spaces.)
Master System Integration and Control Systems
This project was designed in an early period of the development of ZNE building design when the important role of a master system integrator was not well understood. The electrical engineering sub-consultant did not have on staff such a specialized technician and the design team relied to a large degree on control system vendors to provide the expertise. The state-of-art at that time did not include integration of the many control and data monitoring systems that would be required in a ZNE building, especially one as large and complex as the Exploratorium.
The result is the patchwork of control systems typical of that recent period, with no coordination or integration of data monitoring. Energy use is measured via electric power meters that are in- stalled throughout the building, recording data at the panel level in separate categories of space conditioning, lighting and plug loads. This data is sent to a separate Power and Energy Manage- ment System (PEMS), which then sends the data on to the main BMS (Building Management System) where it remains uncompiled and unreported.
Energy production is separately recorded at the PV system connection and then at the utility’s building meter measuring net electricity flow to and from the power grid. These meter readings for the net energy use for the entire building and the renewable energy production are sent to a dashboard near the building entry for public reporting of the basic level of overall energy use versus overall on-site energy production.
The control system for lighting is completely separate from other systems and is limited to time schedule control only.
The Exploratorium recognizes that the design and operation of the building controls and energy monitoring system are not sufficient for their educational mission, nor for collecting the data nec- essary to monitor and improve performance over time, and that a greatly improved data record- ing and reporting system is needed.
Zero Net Energy Case Study Buildings, Volume 2
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THE EXPLORATORIUM
CASE STUDY NO. 11