Off-Grid Case Studies
Here are some examples of off-grid small wind turbines in Canada and the United States.
Off-Grid Farm in Southern Alberta, Canada (10 kW turbine)
A small stand-alone system installed in southern Alberta allows a farm to operate independently of the grid. The farm had been connected to the grid, but the owner wished to have autonomous power and to reduce the environmental impact of his farm and home energy use. The farm’s wind energy system supplies power to a residence for a family of four, a machine shop, a water well and yard lights.
The peak load is about 5 kW. The wind map of Canada shows that the region has a 18 km/h (5 m/s) annual average wind speed at 10 metres height. Power is generated by a 10 kW wind turbine on an extra-tall 33 metre tower. Power from the turbine is rectified (i.e. converted from AC to DC power) to 48 volts DC for storage in high quality low maintenance gelled electrolyte cell deep discharge batteries of 1000 Ah capacity. A 5 kW inverter then supplies 120 and 240 volts AC to the farm and house. To reduce peak loads and electricity consumption, major energy consuming appliances – the stove, clothes dryer, furnace and water heater – are fuelled by natural gas. Additional equipment required to control the power safely includes a transfer switch, battery charging controls, system monitor and circuit protection. If the wind turbine has charged the batteries and is still producing power, a dump load controller “dumps” (or “shunts”) excess power to pre-heat water for the water heater.
This system is larger than a non-farming home would require as it provides power for both the home and farm. The installed cost of the wind turbine, the tower, premium batteries and other BOS equipment was $60,000 CAN (1997). The farm is now free of utility cost increases and the power being consumed has little environmental impact.
Off-grid Farm in Central Alberta, Canada (10 kW turbine)
The rolling prairie of Alberta, between Calgary and Red Deer, is one of the most productive agricultural areas in western Canada. With few trees, deep soils, and a hint of mountain view to the west, this northern end of the Great Plains is a dramatic place. It breeds independence and honours a pioneering spirit.
In 1989, a wheat farmer who wanted independence from the electric utility, purchased a 10-kilowatt wind turbine to supply all his power requirements, including a residence for a family of four, a machine shop, a water well, and yard lights. The Trochu Wheat Farm was already connected to power, but the farmer’s goal was a stand-alone system that would survive inflation and have less environmental impact than the coal used to produce electricity for the grid.
The installed cost for the system, using an extra tall 33-metre tower and premium steel-clad gelled electrolyte batteries, was $55,000 CAN. The Trochu farmer soon discovered that his system was producing more energy than he was using, so he added a custom-designed “dump-load” system to take advantage of the surplus electricity for space heating. This wind energy user is very happy to be an independent energy producer and is pleased with his equipment and the amount of energy it produces. He has become very knowledgeable about his system and feels comfortable to conduct all routine maintenance and operations. He feels that his investment is worthwhile, considering the long expected life of the equipment, energy independence, and reduced environmental impact of the system.
The system specifications are as follows:
- System Type: Upwind, horizontal axis wind turbine
- Model: BWC EXCEL Generator
- Three phase, variable frequency, variable voltage alternator
- Rated Output: 10 kilowatts
- Battery Capacity: 1000 AH @ 48 VDC
Off-Grid Home in Colorado, USA (1.5 kW turbine)
This home, built in Ward, Colorado (at an elevation of 9000 feet (2743 meters)), has been off-grid since it was built in 1972. When the house was built, the nearest utility was over a mile away, and it would have cost between $60 000 US and $70 000 US (based on 1985 rates) to connect to the utility lines. The owners decided to install a hybrid electric system powered by wind, solar, and a generator for a cost of about $19,700 US.
The parts of the system are as follows. Wind generator: 1.5 kW Bergey, 10-ft (3-m) diameter rotor, 70-ft. (21-m) tower; PV panels: Solarex, 480 watts; battery bank: 24 VDC, 375 ampere-hours; inverter: 4 kW Trace sine wave, 120 VAC, 1 phase; generator: 6.5 kW Onan, propane-fueled, (de-rated to 3 kW for altitude). Electric appliances in the home include television, stereo, two computers, toaster, blender, vacuum cleaner, and hair dryer.
The largest electric loads are created by a well pump and washing machine. The generator runs about 20% of the time, particularly when the washing machine is in use. Propane serves the other major loads in the home: range, refrigerator, hot water, and space heat. Solar collectors on the roof provide pre-heating for the hot water.
Off-Grid Cottage near Georgian Bay, Canada (1.5 kW turbine)
When Gard Shelley and his wife visit their cottage in the 30,000 Islands area of Georgian Bay, they are able to enjoy the comforts of home thanks to a combination of wind and solar power.
Stretching for a hundred miles along the northeastern side of Lake Huron, Georgian Bay is ringed with small islands, a landscape of pink granite and trees. But it costs a lot for Toronto Hydroelectric to run cables to the outer islands. Shelley estimates that he would have had to pay a $60,000 (US) installation fee just to connect to the utility's electric grid, which would have required running a cable about a mile underwater from the mainland. By contrast, his Southwest Windpower H1500 cost only about $10,000 to purchase in 1996.
Shelley hired a local contractor to install the 1.5 kW turbine on a 24-foot tower, but found himself helping out so much with the installation that when a neighbor said, "Hey, do that for me!" he decided to make it a sideline to his business. He estimates that he has since helped to install 15-20 windmills in the Georgian Bay area, and perhaps as many as 75-100 in eastern Canada.
Because it is a stand-alone system, Shelley's installation did not require negotiating an interconnection agreement or other arrangements from his utility. Nor did it require any special permitting. The base of the 24-foot tower is about 10 feet above water level, out on a point, completely exposed to the prevailing west wind.
Shelley and his wife use their Georgian Bay cottage from May to late October. They typically use 4-5 kWh/day when they are in residence, and about 1.5 kWh/day (to run a refrigerator) when they are not there. Shelley can count on the windmill to generate anywhere from 0-20 kWh of electricity per day, about 6 kWh/day on average. A complementary solar energy system provides another .75 kWh/day on average. The hybrid system uses a 20 kWh battery bank to ensure that power is there as needed.
The system requires very little maintenance. In addition to avoiding the substantial cost of connecting to the Toronto Hydroelectric grid, Shelley estimates that the system saves him another $1,000/year in electricity bills.
Off-Grid Home near Silver Islet, Ontario (1.3 kW turbine)
Silver Islet is a summer cottage community with a small number of year-round residents, approximately 100 km from the city of Thunder Bay, Ontario. The Ontario Hydro grid is several miles away and most cottagers use woodstoves, propane appliances, kerosene lanterns, and gas generators when they need electricity.
The Thunder Bay area is typically a good solar regime. Even in winter when days are short, the skies are typically clear and the sun bright. This particular location on the shore of Lake Superior is also ideal for wind energy.
Cam and Brenda Snell live year-round in this remote community. They have chosen to provide power for their log home with a hybrid solar PV/wind system. This energy system gives them the ability to live with comfortable modern conveniences amidst the incredible beauty of this northern wilderness.
The systems specifications are as follows:
- Four 75 watt (4.4 amp at 12 VDC) Siemens PC4 solar panels, configured for 24 volts, for an array of 8.8 amp capacity at 24 VDC; all on a Wattsun single axis tracker
- Custom-built pole mount for array on deck
- Whisper 1300-watt 2-blade wind generator (high voltage model) on mountain behind house, 125m of Teck cable.
- 15m tubular steel tower with gin pole to facilitate lowering for maintenance.
In the utility shed the following equipment is housed. Inverter: Trace 4024 SW, with fused DC disconnect, in insulated compartment; battery bank: 820amp/hour composed of four 6volt Surrette dual-case batteries with hydrocaps, in sealed vented insulated compartment which incorporates a 40-watt light bulb in an explosion-proof fixture for heating compartment when necessary; diversion control (dump load control): Enermaxer 60-amp, with custom built 1850-watt resistor bank and shield transformer; rectifier and brake for the wind generator; solar system disconnect switch custom built manual override for tracker; back-up generator: 4.5kW, propane fuelled.
In House: Remote Photron MPC-3m to track battery voltage, batter compartment temperature, amp consumption, and system amp production.
This renewable energy system was installed in the fall of 1995. Cam and Brenda have learned to live with the system, adjusting their consumption habits to suit the weather. The system provides power for most conventional household needs, such as lighting, stereo, TV/VCR, small kitchen appliances, microwave, vacuum cleaner, power tools, hair dryer, submersible water pump (120 V AC), washing machine, and an ultra-efficient Vestfrost two compartment two-compressor fridge/freezer.
The home is heated by a woodstove and two propane heaters; the kitchen range and water-heater use propane, a back-up generator provided power and charges the battery bank via the inverter’s standby feature if needed.
The advantage of a hybrid system in this climate and latitude is how well solar power and wind power complement each other. A solar system can provide for most needs in the summer when daylight hours are long and power requirements are less. In winter, daylight hours are short, but typically the wind is stronger, colder, and therefore more powerful. A system of this type can be used to provide power for household needs as long as energy conservation is part of the homeowners’ routine.