1) drying bath towels in the sun.
My bathroom doesn't have very good ventilation. I realized that when hang dry my bath towels (on my deck on a drying rack, on a sunny day anyway) the bath towels don't get the mildewy smell that it used to after a few days. Not only do the towels dry faster, sunlight also kill germs. This prolong the number of days the towels can go before being washed.
I also sun dry our bath mat, hand towels every few days.
2) I make my own almond milk. I used to dump the almond meal after making the milk. A big waste but I didn't know what to do with it, Then my husband started buying these $9/lb almond meal to make paleo tea cakes. ....So what I do now is, after I make the almond milk, i scattered the wet almond meal in a glass baking tray, and sit it on top of the Charbroil Grill on the deck. On a sunny day, it dries the same day. We will then either use it right away, or freeze them.
We also just installed solar panels on the roof...
But i would like to hear what other low tech ways other people make sure of the sun energy.