Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 425

7.4.2.9 Photovoltaics
The RSF makes extensive use of photovoltaics as its choice of RET to reach
net-zero energy. There are three systems totaling 1.7 MW. The first is a
449 kW system on the roof of the RSF (south-facing, slope 10°, attached
to standing seam metal roof). The second is a 524 kW system that acts
as a shade canopy over the visitors' parking lot. And the third is a 706
kW system, also a shade canopy, over the adjacent staff parking garage.
Altogether, the Net ZEB boundary for the project is comprised of Phase I
and Phase II of the RSF, the staff parking garage, and the visitors' parking
lot.
The second and third PV systems' surface areas are approximately 40 and
100%, respectively, of the size of the RSF rooftop PV system. This is
significant because it means approximately 140% of additional roof surface
area is needed to generate enough electricity for the RSF to attain Net
ZEB status if the Net ZEB boundary for the project was limited to the
building only. This would be the case for buildings on dense urban sites
where surface areas for possible PV integration are limited. In fact, from the
beginningoftheproject,itwasunderstoodthattheRSFroofalonecouldnot
provideenoughsurfaceareaforPVgenerationandthattheadjacentparking
areas would be needed as well.
Basedon2011data,thetotalannualenergyconsumptionoftheRSFisabout
2.35 GWh, and the PV energy generation is about 0.92 GWh. During that
year, energy consumption was matched by generation in July. This feat was
achieved withonlythefirsttwoofthePVsystemsoperational. Thecomplete
PV system was not fully operational until April 2013. Figure 7.58 shows the
monthly total energy consumption (which includes the energy consumption
from the data center) and energy generation from 2011.