You have installed a wind turbine and a solar array on a tracker for your new off-grid home.
It was sized for your budget and electrical needs — so now why in all that is environmentally friendly would you need a generator?
A number of practical reasons instantly spring to mind.
One is insurance. Home policies stipulate that alternate energy installations require a backup generator.
This is for a simple reason, as well as reason No. 2. Weather!
Weather is, as any Albertan knows, as fickle as a trout on a time table.
Fog is the enemy. Storms bring wind, spring days bring sunshine, and a week of fog brings fuel bills. It’s that simple.
The next reason for pure, old-fashioned electromotive force is high electrical loads for prolonged periods.
You know the deal: the brother and sister-in-law are over with their eight children, every light in the house is on, the kids are in and out at a furious pace, extra heat, extra pump loads, toilets flushing, televisions going . . . you get the picture.
About midnight when all is finally quiet, you decide to fire up the Jacuzzi, and low and behold you need just a little more than the reserves in the battery bank can supply.
Automatically the generator comes on, providing the power for that soak in the suds.
It tops off the battery bank and shuts down without so much as a flicker in the lights or a finger being raised by owner.
The system switches over seamlessly anytime extra power is needed.
Typically the generator runs most from November to March and usually it is due to a high demand for power at a low production period; short days, more fog and calm nights.
So what type of generator to use?
Well that depends on each situation.
If you have a heated shop and lots of diesel-powered equipment, a diesel powered-generator may be the ticket.
It that’s not your situation, then a duel fuel generator that uses either natural gas or propane will fill the bill.
What size? Well again what are your circumstances? A retired couple with a good solar and wind set-up, 10 to 12 kilowatts will fill the bill.
If you are running a large shop or multiple buildings like house, garage, shop and barn, 18-40 kW is required.
The size is determined by the size of your battery bank and the need to charge it as quickly as possible, while still powering everything that needs to run.
The backup generator is a prime consideration in an off-grid home system.
Choosing the correct one is essential to keeping costs down and keeping the system operational for the long term.
It generates input costs as well as electricity, of course, but if care is taken in making the correct choice, then the costs will be minimal and the life of the system will be long and trouble free.
Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003 and is in the planning stage for his second.
His column appears every second Friday in the Advocate. Contact him at: lorne@solartechnical.ca