Page 110 - Zero Net Energy Case Study Homes-Volume 1

CASE STUDY NO. 5 COLONIAL HOUSE MULTI-FAMILY HOUSING
(Opposite page) Initial size and layout of the solar PV sys- tem on the roofs and trellises needed to realize ZNE per- formance of the housing and community building. (Courtesy Coastal Architects).
(Below) Solar PV system as installed. (Courtesy of Red- wood Energy).
Renewable On-Site Energy Supply
The large solar PV array was sized based on the results of the computer simulation of the annual energy consumption of the 44 housing units, assuming average energy use patterns prescribed by the software. (See energy modeling discussion below.) This analysis yielded an annual en- ergy use of 216,000 kWh, which was determined to be the minimum required output for ZNE performance. This was calculated as that produced by a 147 kW(DC) system with the Oxnard project’s configuration.
The decision was made to install solar PV panels on all available roof space as limited by code and fire access restrictions and on the three trellis features in the community open space. Ini- tially, the solar PV system planned consisted of 523 panels mounted at 10° tilt angle on the roof arrays (housing and community building) and 147 panels mounted flat on the trellises, as shown in the drawing on the opposite page. This system design would have a total of 670 panels of SunPower module (Type E) with an output of 240 watts (DC) and a total installation of 160.8 kW. With that output, the housing project would have been expected to perform at ZNE as measured during occupancy.
The actual system installed consists of 304 SunPower modules with an output of 327 watts (DC) for a total installation of 99.8 kW. This essentially means that when all units are taken together, the total energy produced on site annually would not offset the annual energy consumption total.
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Zero Net Energy Case Study Homes: Volume 1