Page 139 - Zero Net Energy Case Study Buildings-Volume 2

Energy Production versus Energy Use — Zero Net Energy Performance
The energy production by the solar PV system is separately and accurately recorded as part of that system’s operation. Using the utility meter data, the standard charts can be constructed showing the building energy use versus the on-site production and the cumulative net energy performance over the two year period. These measured data show that the building has been performing below the ZNE goal, with total annual on-site energy production at 83% of the total annual energy use, not the 100%+ needed to make it a ZNE-performing building.
Since the building is using an amount of energy slightly less than that determined from the energy modeling, the issue appears to be simply an under-production by the solar photovoltaic system. While the number of panels was originally expected to be adequate to offset the design loads, adjustments to the panel layout and unexpected maintenance issues appear to have lowered the production below the desired threshold. The PV panel performance was severely hampered by the presence of sea birds, as noted above.
Combined with a greatly enhanced solar PV panel cleaning schedule, the Exploratorium’s pro- gram to reduce plug loads and engage staff for further reductions in energy use should help to bring into balance the two curves of Energy Use and Energy Production, resulting in an annual ZNE performance. Though a less likely scenario, changing out some of the original PV panels for replacements with higher production would also raise the production level and bring the building to a net positive performance level.
THE EXPLORATORIUM
CASE STUDY NO. 11
Solar Photovoltaic System Performance (2015)
Zero Net Energy Case Study Buildings, Volume 2
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