Research Highlights

Energy Use Patterns in Off-Grid Houses – Case Study #1 :Yarmouth County , NS

House Description

A 16 x 8 m (52 x 26 ft.) bungalow with full basement, this energy efficient “package” house was built in 1998 for a family of four (two grown children are now part-time residents). The house takes advantage of good passive solar orientation and of a well-treed area to the north to reduce the impact of cold winter winds. An airtight stove (3 cords wood/yr) augments the solar space heating.

Thermal Envelope Summary

AC/H@50 Pa: 2.77
Walls: 2x6 framing w/RSI 3.5 (R20) (bare conc. basement.
walls, no ins. @ slab)
Ceilings: RSI 7 (R40)
Windows: low-E, argon fill, insulating spacers
Doors: steel polyurethane core

System Description

Power is supplied by a 300 W PV array and an Air 303-12 wind generator. A 5 kW gas generator is used as backup. Energy is stored in a bank of 10, T2200 golf-cart type batteries, wired to produce 12 VDC (1200 Ah). A Trace DR2412 modified sine wave Inverter/Charger is used to produce 120 VAC throughout the house (there are no DC loads). The cost to install the system was $15,000 CAD.

System Performance

The load on the system includes lighting, refrigerator, water pump, vacuum, washing machine, computer, fax machine, 26” TV with satellite system and several small appliances. The total possible daily load on the system is approximately 42 MJ (12 kWh), while the actual load is estimated to be 19 MJ (5 kWh). Propane is the energy source for water heat, clothes drying and cooking. Approximately 1470 L of propane is purchased annually. The 5 kW genset, which is housed in a small shed to the west of the house, is run an average of 1,092 hours, providing 5,460 kWh of power for the house. The genset has a remote start mechanism installed for convenience.

Annually, the actual electrical use in this house is about 7,050 MJ (1,960 kWh).When the kWh equivalent of the propane appliances is included in the actual energy use in this house, the figure is approximately 38,150 MJ (10,600 kWh). The average annual lighting and appliance energy use for vintage house in Nova Scotia is 24,500 MJ (6,810 kWh). Water heating accounts for another 24,500 MJ (6,810 kWh)1, for a total of 49,000 MJ (13,620kWh). There is a difference of 10,850 MJ (3,010 kWh), for a 22% reduction. These figures do not include space heating.

Notes From Homeowner @ System Operation:

Windbreak @ N of house is interfering with the wind generator, the height is to be increased from 6.7 m to 15 m (22 to 50 ft.). The solar array was recently put on turntable to see if daily output can be increased. Another five panels are to be added to the system to reduce the use of the genset, which is currently run about three hours every evening.

1Home Energy Retrofit in Canada: Overview and Opportunities; NRCan, CMHC, March 1994 ISBN 0662-22198-2

Homeowner’s reasons for going off-grid:

As part of the homeowner’s business, he felt it was necessary to show a “normal” house with an off-grid system, even though the cost of grid connection on this site was minimal. Homeowner has been interested in wind and PV since the 1970s, with a focus on PV for these reasons: no moving parts, quiet, minimal maintenance. The downside of PV is the toxic materials used in panels, and their susceptibility to radiation damage (“browning” or “mirroring”). Small-scale residential wind installations are typically high maintenance and site specific. Homeowner would not have recommended wind generator for this site for a client, but he had one in stock and wanted to show it to potential clients.

Homeowner’s observations on living off-grid and energy use patterns: