Page 132 - Zero Net Energy Case Study Homes-Volume 2

CASE STUDY NO. 11
SOL LUX ALPHA
Energy Production versus Energy Use: Zero Net Energy Performance
The charts on pp. 115-117 show the solar PV system performance over the course of a year for each condominium unit compared to the monthly measured energy use for that same period. The excess solar energy production in each case indicates how much energy would be available theoretically for EV charging or is simply exported to the utility grid for additional revenue.
The cumulative net energy production is a chart that essentially shows the progression of the en- ergy performance toward ZNE by adding each month’s net energy performance to the previous month’s total—if, at the end of the 12-month period, the curve remains on the positive side of the zero axis, then the building is indeed performing better than ZNE, i.e., Net Positive.
Because each condominium unit’s system is currently wired so that the EV-charging energy always comes from the grid and cannot come from the PV system or battery, there is an excess of production by each solar PV system, which was originally designed to include some EV charg- ing. Were this circuiting to be changed in the future, the EV-owners would know roughly how much of the battery could be used at night and still remain at ZNE for house and EV. Alternatively, if personal schedules permit, the EV could be charged at home during the day directly from the solar PV panels after the batteries had been charged.
Post-Occupancy: Observations and Conclusions
The manufactured wall panels had perceived advantages in theory but proved to have too many practical difficulties to warrant using the same approach on future similar projects with greatly re- stricted crane access. The process of assembly on site from only one of the short sides of a long narrow site, street closures, large crane rental required for necessary “reach”, and positioning the heavy panels at the attachment points, were together sufficient to bring the developer to this conclusion in retrospect. The added requirement of meeting the strict airtightness standard for Passive House certification was particularly difficult to achieve because of these site logisitics. The airtightness standard was finally achieved, but not until much time and effort had been expended—a discouraging result for any developer.
The developer is nevertheless not dissuaded from using manufactured housing components on a more accessible site, where prefabrication can save cost, construction time and result in a highly energy-efficient product meeting Passive House standards.
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Zero Net Energy Case Study Homes: Volume 2