Research Highlights

Energy Use Patterns in Off-Grid Houses – Case Study #10: Belfast, PEI

House Description

A 1 1/2 storey house built on a slab foundation. The main house is 7.3 x 9.7 m (24 x 32 ft.), the sunroom/office section is 4.9 x 7.0 m (16 x 23 ft.), and the workshop/studio section is 5.5 x 7.3 m (18 x 24 ft.), with 1.8 x 3.7 m (6 x 12 ft.) indoor wood storage area. The total heated area is 279 m2 (3,000 sq.ft.). It was built as an affordable alternative to the PEI Advanced House Project (sponsored by NRCan). This house has been occupied by a family of five full-time since the fall of 1997 (currently three are full-time). The house has good solar access. An airtight woodstove provides space heating for the main section of the house (3 cords wood/year) and preheats the water. In-floor hydronic heat is installed in both main and upper floors, but only used in office and studio (upper floors). This alternative energy system is different from the other houses in the study, as it is connected to the grid. See below for details.

Thermal Envelope Summary
AC/H@50 Pa: 2.19
Walls: 3.3 RSI
Ceilings: RSI 7.4
Floors: RSI 1.4 under slab
Windows: 3/8” space, low-E, argon casement and single hung
Doors: steel polyurethane core

System Description

Power is supplied by a World Power H900 wind generator, rated at 900 W output. Energy is stored in 4, Surrette “Big Red CS25” batteries, wired to produce 124 VDC (840 Ah). A 4,000 W Trace SW4024 inverter produces 120 VAC for the house. A grid-connected sub-panel provides backup power. The system cost approximately $18,000 CAD.

System Performance

The load on the system includes lights, a water pump, a fridge, two freezers, laptop computer w/printer, fax machine, portable stereo, TV/VCR unit, clothes washer, vacuum, iron, sewing machine, toaster and popcorn popper. The total possible daily load is approximately 29 MJ (8kWh), while the actual one is estimated to be 22 MJ (6 kWh), with the renewable energy system typically supplying 2 kWh per day. Water heat is provided seasonally by the water coil off the airtight stove. Cooking and the remaining hot water for the house is provided by propane. Approximately 600 L of propane are required each year. The grid connection is used to carry the house over times when the batteries are charging.

The actual electrical use in this house is about 7,810 MJ (2,170 kWh) annually. When the kWh equivalent of the propane appliances is included in this figure, the total is 21,380 MJ (5,940 kWh). The average annual lighting and appliance use for this vintage house in PEI is 24,500 MJ (6,810 kWh).Water heating accounts for another 24,500 MJ (6,810 kWh), for a total of 49,000 MJ (13,620 kWh). There is a difference of 27,620 MJ (7,670 kWh), for a reduction of 56%. These figures do not include space heating.

Notes From Homeowner @ System Operation:

It is important to note that the grid connection is not used to charge the batteries, rather it is used to carry the house through periods when the batteries are being recharged by the wind system. Although the wind generator is rated at 900 W, it acts more like a 600 W generator. A higher tower would result in better performance, but the homeowner feels that the wind unit is overrated. In 2001, the following changes will be made to the system: a new 1 kW-rated wind generator will be installed, as will a 1 kW PV system (16-75 W panels). This will bring the overall cost of the system to almost $30,000 CAD (less the sale of the original wind generator).

Homeowner’s reasons for going off-grid:

The homeowner wanted the house to provide a demonstration of an effective renewable power system, to achieve energy self-sufficiency, and to reduce electrical use from non-renewable sources.

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