Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 468

The ceiling fans are used during summer (November to April). The overall
consumption of the fans and the split systems units is 2.2 kWh/m 2 NFA /yr
whereas in a standard building, air-conditioning systems usually consume
80 kWh/m 2 NFA /yr. The strategy of using cross-natural-ventilation with
ceiling fans represents great potential for energy savings.
The PV production measured over theyear was 79,440 kWh compared toan
overall consumption of 10,202 kWh. ENERPOS has produced seven times
its electrical consumption over the year, making it a Net ZEB on an annual,
monthly, and daily basis. The PV system seems oversized, but the design
meets the goal of incorporating an architecturally integrated PV roof.
The PV system is not part of the overall cost of the building. It is included
in a financial agreement between the University of Reunion Island and a
private manufacturer. The terms of the contract specify that the university
rent its roof for 15 years. The manufacturer installed the PV system and
supports all of the costs and risks (including cyclones and maintenance)
during that period, but gets the benefits of the electricity fed into the grid
(€0.55/kWh). After 15 years, the university will become the owner of the PV
system.
The architect of the building wanted symmetry, with half the over-roof
facing north and the other half facing south. Both slopes are 9°, which is
not the optimal slope (the optimal orientation is north-facing with a slope
of about 21°) in terms of photovoltaic performance for Reunion Island.
Comparing the PV yield of the north roof to the south, it shows that the
slight suboptimal orientation does not have a significant impact (about 10%
difference).
7.5.11 Comparison of Model Prediction with Measurements for
ENERPOS
The example of the ENERPOS building illustrates the uncertainties that can
appear in the models developed during the design of a building. As stated in
Section 7.5.8.3, several models were developed during the design process of
ENERPOS, but those models were used to assess and support the expertise
used to design the building rather than to optimize the envelope or the
operation of the systems operating within. Two comparisons are presented
in this section. The first is a comparison between the energy use predicted
during design and the measurements available due to 2 years of monitoring.