We had a very successful crop of limes last fall - about 250 limes, from which we squeezed about a litre and a half of juice. As recommended by Will B. in a post last year, we froze most of the juice in ice cube trays and have used it for mixed drinks (G and T, Daquiris, Margaritas, etc.) over the fall and winter months. We did have a scare last winter though. The tree is in the ground, so it has to be protected over the winter. The risk is that we have a power failure during a cold snap and lose use of the electric heater. (When it gets below about -7 C the 7 watt Christmas lights that we rely on to keep the tree a few degrees above freezing need to be augmented. The back-up heat is from an electric heater with a thermostat that kicks in and out.) During the third of our three deep freezes last winter, when the ambient temperature was about -13 C we had a 5 1/2 hour power failure and the tree suffered some damage with several of the branches dying from frost bite. I'm happy to say that it has survived and there is lots of new growth following the recent warm spell.
I wonder if a number of reusable hand warmers could be used as a backup in the event of a power failure. Of course that would only work if you're not away or asleep when it happens. https://ecofreek.com/reusable/reusable-hand-warmers/
That's an interesting question, Junglekeeper. As you know, insulating material has an R value. The inverse of that is called the Heat Loss U factor, which is calculated using 3 variables: 1. The design temperature (in degrees F) or Delta T. That's the minimum outside temperature you expect where you live, minus the minimum temperature you can go to in the greenhouse. For me that's 26 (36.5 F or 2.5 C minus 8.5 F or -13 C). 2. The external area of the walls and roof of the structure. My bigger greenhouse is 6.5 ft tall and all 4 sides are 6 ft, so the area of those 5 sides is approx 185 sq. ft. 3. The R factor of whatever material the walls of the greenhouse are made of. For example, the R factor for 4 mil polyethylene or fiberglass is approx.1.20, 1.13 for single layer glass, and 1.15 for 6 mil polyethylene. Mine is 4 mil plastic (1.20) With these three variable you can calculate the wall surface heat loss in BTUs, which is the BTUs of your heat source necessary for you to keep the greenhouse above the desired minimum temperature (+2.5 C) on a -13 degree C day (or night). This is the required heat load. In my case it's 5,850 BTUs. Something else to take into account is the air infiltration heat loss, which for me is very small because the greenhouse when zipped up is pretty airtight. when I take that into account I need about 6,200 BTUs. I get about 1,000 BTUs per hour out of my 100 7 watt Christmas lights, and my electric heater generates an additional 5,200 BTUs at the high (1,500 watt) setting. I'd probably need to use the charcoal hand warmers, and I'd need a few dozen of them, I would imagine. Plus I'd have to add two lumps of charcoal every hour to each one. Hard to know for sure how many I'd need as the BTU ratings aren't provided in the link you provided. But they would add some heat. I think the more practical solution might be to buy a gas powered electric generator or to rig up my EV (once I buy one) to power the heater during a power failure. I've had this set up for 10 years now and last winter was the first time we lost power during an extreme cold spell. Fingers crossed.
There are a number of small portable propane heaters available (many with a tip over/turn off feature) which have gotten me through extended outages during deep freezes. The modern ones are quite safe. Nice harvest. I see you’re in Crescent Beach—I grew up there. Miss it often.
For backup heat to my big greenhouse I use a dyna-glo type of propane heater that has a built in oxygen depletion sensor. Worked great for me on the very rare occasions I needed it.
