Living off-grid with three different seasonal renewable energy sources (wind, water, and sun) means our energy production ebbs and flows. It ranges from very high (for us) to a thriftier trickle as the weather runs its course. Bottom line: During times of bountiful power, if I’m not using the electricity our systems produce, then it is wasted.
When the wind blows, the water flows, and the sky is blue, our batteries rarely get below 100% charge. My husband Bob-O has installed a shunt to take the extra electricity our system produces and, through an electric element, this excess heats the water in our water tank.
This works so well that sometimes the water coming out of our faucet is 150°F. That’s okay—we are used to it and are careful. When you take a shower at our house, you first turn on the hot water all the way and then use the cold water to regulate the temperature. And there’s absolutely no toilet-flushing allowed when someone is showering.
The hot water is great, but we only need so much. It seems like whatever I do to use excess electricity also uses water. I can wash laundry in my water-efficient front loader or wash dishes in my water-efficient dishwasher. That is all well and good during the seasons in which we have an abundance of water. But there are times when the creek is so low we can’t run the hydro turbine, and the spring that feeds our domestic water system slows to a trickle. The sun and wind inputs are at full bore, so in the daytime there is a lot of electricity. That’s when I need an appliance that uses electricity, but not water. I could use my microwave oven to use that electricity, but I mainly use it for reheating food—I don’t really like the idea of cooking my meals in it.
For years I have been curious about induction cooking. What would it be like to cook with electricity? I’ve always cooked on natural gas or propane stoves. Using electricity to make heat or cold usually uses a lot of electricity. That is why off-grid homes use gas to cook with, and solar or gas for heating water (unless you have a shunt setup like ours), and use a gas clothes dryer. In arid locations like ours, air conditioners are abandoned in favor of more energy-efficient evaporative coolers.
While it uses electricity, induction cooking is different from cooking on electric elements. Induction does not involve an electrical element heating a pot or pan—it makes the cooking vessel itself the generator of the cooking heat.
I’m not going to go all nerdy here—I’ll let Wikipedia do it: “An induction cooker transfers electrical energy by induction from a coil of wire into a metal vessel that must be ferromagnetic. The coil is mounted under the cooking surface, and a large alternating current is passed through it. The current creates a changing magnetic field. When an electrically conductive pot is brought close to the cooking surface, the magnetic field induces an electrical current, called an ‘eddy current,’ in the pot. The eddy current, flowing through the electrical resistance, produces heat; the pot gets hot and heats its contents by conduction.”
Just the pot gets hot and that’s what cooks the food inside. I’ve really wanted to try this for some time, but the cost was prohibitive. I saw one for sale on Craigslist and the price was reasonable. I went online, looked up the model and started reading user reviews. That particular single “burner” model did not get ecstatic reviews, so I researched other models. I found what I wanted—the Sunpentown Mr. Induction Cooktop—read the reviews, looked for the best price ($59), and ordered it.
The single-burner unit draws 100 to 1,300 watts, depending on the setting. The temperature range is 100°F to 390°F. With seven cook (wattage) levels and 13 temperature settings, this gives me a huge amount of control.
Since the cookware must be a ferrous material, I had to check my pots and pans to see if they were compatible. This is very simple to do, using a small magnet for testing—if the magnet stuck, the pan or pot could be used on the induction cooker. All of my cast-iron pans were shoo-ins. I had an old enameled cast-iron casserole I was looking forward to using. The magnet stuck, but the bottom was not smooth and flat. There was a raised, round ridge on the bottom, and that put it out of the running. I tested everything—my countertops were littered with every pot I owned. I even dug into my camping gear. I ended up with a small array of workable cookware.
The first thing I tried was to boil water. It took two minutes on 700 watts (23.3 Wh) to bring two cups of water to a boil. Next, I made homemade corn tortillas and cooked them on my round cast-iron griddle. Wonderful! Then I cooked a big pot of beans in one of my enameled cast-iron camp pots. This worked quite well, although I was surprised to return after two hours to stir the beans and find that the unit was off. Apparently, as a safety measure, if you do not set the timer (one minute to eight hours), the unit will shut itself off in two hours. I turned it back on and set the timer.
Another safety feature is the “lock” button. To turn the unit on, the lock button must be pressed. If no other button is pressed within 30 seconds, the unit will turn itself off. It also turns off automatically when the cooking pot is removed.
I know from my solar cooking education that food pasteurization begins at about 160°F. So I can set my cooktop to that temperature and feel confident to leave food safely simmering at that temperature for an extended period of time (say, more than two hours).
Of course, not all of my induction cooking is done for extended periods of time. I mostly use the cooktop during the daylight hours—when our solar and wind power sources are peaking. I have gotten into the habit of cooking things like rice, lentils, or potatoes during the day to use later as part of our dinner. The cooktop also works great for cooking breakfast grains (Bob-O calls them all “gruel”) or for pancakes and eggs. Even though the batteries aren’t completely full in the morning, they soon will be, and I’m careful to first check the battery meter on our wall, so I can see the battery bank’s state of charge. This kind of cooking does not take a lot of time, so it takes less energy.
I feel very good about this purchase. I now have a method to cook food using our surplus renewable energy. It is one of the puzzle pieces that fit in to make our renewable energy system even more efficient.
Kathleen Jarschke-Schultze is looking into landrace vegetable farming to adapt varieties to the microclimate at her off-grid home in northernmost California.