Any cheap permanent ways to keep citrus warm in mild winters without covering?

I live in a hot climate that is usually good for citrus, but in winter, it does sometimes get below freezing. Lowest it has ever gotten here is 17 F (about -8 celsius), but it usually only gets down to the low 20's F. And even that is not for long - 3 days in a row below freezing is the record for the last 10 years, and on an average year it's just a few hours below freezing, maybe 2-3 dozen times throughout the winter.

People here protect their citrus without trouble, usually by covering it at night on these days, or putting the old fashioned, huge Christmas lights throughout the branches to keep them warm.

My limitations: I have chronic pain that makes it difficult to frequently put on and take off the coverings and it's likely to get worse over the years, so while I DO put on coverings now, even the couple of years I've had these citrus have been very hard, you know? I don't have outlets anywhere NEAR where there are citrus trees in my yard. I don't have a job currently due to the whole chronic illness issue, so buying a lot of supplies, like Christmas lights or special coverings, amendments, etc... in order to make something to help my trees is unlikely to be possible for a long while. And also, my hot climate is so hot that if I put rocks and such around the trees when they are smaller (a couple are), reflected heat may fry the poor things in the summer time.

What I've got: 1/3 of an acre of land. A large pond that the citrus are growing around. A ton of rocks all over that are fist sized to 2-3 times that size which I can build something with, a lot of dirt and a fair amount of sand, an old wood chipper and lots of chop and drop trees around that I can use for wood chips, a lot of native and drought tolerant trees that I can get seeds from to grow new trees, and some powdered cement and a couple small rolls of chicken wire.

So, anyone know any way I can use what I've got to help my citrus trees stay warm in the winter time here? Something different for the young vs. the older trees, maybe?   I have some ideas, but honestly, I'm very new to citrus, so would love advice!

Even if it's just to start brushing up on my baking to bribe local teens so I can get them to come cover my citrus trees during the winter time. ^_^

Could you build sun traps around the citrus with rocks?  Curved walls of rock that catch the low angle winter sun and radiate it back at the citrus.  Steep/tall enough that the high summer sun doesn't bake the citrus.