Residential Grid-Direct Photovoltaic System: SMUD Home of the Future

The Sacramento Municipal Utilities District (SMUD) Home of the Future, built by RJ Walter Homes in Folsom, California, is the first LEED Platinum house built in the Sacramento region and is only the second LEED Platinum home built in Northern California. The award winning design was created by a consortium of partners including SMUD, the US Department of Energy’s Building America program, Building Science Corporation and the National Renewable Energy Laboratory.

The SMUD Home of the Future combines beauty, affordability and comfort while leading the way to an environmentally sustainable future. Special care was taken in selecting the materials and components of the house to make the lowest possible environmental impact while providing the highest energy performance and best indoor air quality. The goal of SMUD’s program is to design and build true zero energy homes— homes that produce as much energy as they use.

OCR Solar & Roofing provided the design, installation and commissioning of the PV system with battery backup and worked with SMUD, BP Solar and NREL on the installation of the advanced PV system monitoring package. In addition to the PV system, the house also has a solar assisted domestic hot water and heating system.

"Compared to homes built to California’s already stringent Title 24 energy standards, the SMUD Home of the Future not only reduces annual energy use and utility bills by 80%, including net zero electric use, but it also cuts peak demand by 80%."

Bill Reaugh, OCR Solar & Roofing

Overview

DESIGNER: Bill Reaugh, technical services manager, OCR Solar & Roofing, ocrsolarandroofing.com
PROJECT MANAGER: Fred Dever, solar general superintendent, OCR Solar & Roofing
DATE COMMISSIONED: September 2008 Installation timeframe: 120 days (over the course of new construction)
LOCATION: Folsom, CA, 38.7°N
SOLAR RESOURCE: 5.32 kWh/m2/day
RECORD LOW/AVERAGE HIGH TEMPERATURE: 17°F / 95°F
ARRAY CAPACITY: 4.73 kW
STC ANNUAL AC PRODUCTION: 6.4 MWh

Equipment Specifications

MODULES: 27 BP Solar BP 175I, 175 W STC, +5%/-5%, 4.9 Imp, 35.8 Vmp, 5.5 Isc, 43.6 Voc
INVERTER: Xantrex XW 6048, 6 kW
CHARGE CONTROLLERS: Two XW SCC, 150 Vdc maximum input, 60 A MPPT charger
BATTERIES: 12 Dekka 8G31, 12 Vdc, 98 Ah, wired for 294 Ah at 48 Vdc
ARRAY: Three modules per string (525 W, 4.9 Imp, 107.4 Vmp, 5.5 Isc, 130.8 Voc), four and five circuits per charge controller (2,100/2,625 W, 19.6/24.5 Imp, 107.4 Vmp, 22.0/27.5 Isc, 130.8 Voc)
ARRAY COMBINER: Two Midnight Solar MNPV6 with 10 A, 150 Vdc breakers
SYSTEM MONITORING: SMUD bidirectional kWh meter on inverter output circuit and NREL sponsored monitoring system with weather station
ARRAY INSTALLATION: Roof mount on composition shingles, low profile BP Solar Integra racking, 160° azimuth, 23° tilt

Article Discussion

Related Articles