Wind energy in Use (case study #1)
There are a growing number of farms across the American mid west and Canadian prairies that have gone off grid, due to the use of wind energy. Let's take a close look at a wind energy system completely off grid, situated on a farm in southern Alberta. The wind energy system is supplemented by natural gas, and when the wind power system is producing excess energy, this is used to heat water for the farm.
The farm had been connected to the grid, but the owner wished to have autonomous power and reduce 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.