Page 130 - Zero Net Energy Case Study Buildings-Volume 3

CASE STUDY NO. 16
LACCD HARBOR COLLEGE SCIENCE BUILDING
Energy Design Analysis and Energy Performance
Modeling versus Post-Occupancy Measurement
Energy Modeling
Energy modeling was done during the design phase using IES VE software. The modeling showed a total energy use of 1,549 MWh per year or an EUI of 75.5 kBtu/sq.ft. per year. Given the number of laboratory spaces in this building, this is a reasonably low EUI that would enable ZNE performance. However, the multifloor building that is required to accommodate the full program on site does not have sufficient space for the solar PV system necessary to achieve ZNE performance, even with the innovative structure that wraps up the south façade and over the roof. Some site location for a substantial amount of additional PV panels proved necessary.
The modeled energy use for the Science Building as designed are given in the charts on the op- posite page, broken out by category of energy use.
Energy Use—Actual Measurement
As mentioned above, until 2018 there was no data recorded for the actual energy use in the building even though the meters were operational since occupancy. This includes separate mea- surements of the energy used at the Central Plant for production of heated and chilled water that are piped to the Science Building for heating, cooling and DHW, as part of the building’s HVAC system. The District has since begun to record all of this data.
Similarly, there has been no separate metering of the energy produced by solar PV system that is part of the Science Building. However, there has been metering of the net electric use/produc- tion for the building, which has been recorded since the building was occupied in 2013. This case study makes use of this data to report a reasonable estimation of the ZNE performance of this building. (See the following section for further discussion of this estimation method.)
Energy Production versus Energy Use: Zero Net Energy Performance
As noted above, the overall size and the laboratory program of this building as designed result in an energy use that cannot be offset with a building-integrated solar PV system alone. The campus as a whole has installed a very large solar PV system above the major parking areas on canopy structures and the roof of a major parking structure. This campus system is immediately adjacent to the Science Building and some of the power generated is supplied to the Science Building via the campus power grid. Therefore, it is reasonable to “assign” a portion of the re- newable energy from this campus system to the Science Building and determine that all of the building’s annual energy use is effectively offset and produces ZNE performance, as follows:
The portion of the campus system necessary for ZNE performance of the Science Building would equal the net metered annual electrical energy use at the building plus the kWh equivalent of the gas energy used for this building at the Central Plant. While the net metered annual electrical use at the building is available as recorded data, there is no separate recorded data for the gas energy figure at the current time. Therefore, for estimating purposes, the energy use modeled for heating, cooling and DHW energy can be used as a reasonable approximation for the actual gas energy use.
The measured net-meter electrical energy used in the building for 2016 is -3,762 kWh, making the building ZNE-Electric, or grid-neutral. This number accounts for the electric energy use of the building minus the solar PV electric energy produced by the system that is integral to the building. The modeled gas energy use for heating, cooling and DHW, totals 466,475 kWh (after
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Zero Net Energy Case Study Buildings: Volume 3