Tiny refrigeration compressors the size of a soda can have hit the market in the past few years, leading to portable battery powered refrigerator/freezer coolers.
How that came about was the US military put out a bid for the thing, some companies submitted designs. The military went, nahhh, changed our minds. Don't need.
Since the tiny compressors weren't a weapon or other item unsuitable for civilian use, the companies decided to not waste all their R&D time and money, and started manufacturing them. Adam Savage had one built into a cooling backpack for a spacesuit costume. That enabled a much longer comfortable wear time than his "Alien" suit from a previous year that used circulating ice water which heated up in 10~15 minutes.
For photovoltaic panel efficiency, the recent development is bifacial panels. They have a transparent instead of opaque backing so any scattered light hitting the back side adds to the power output. That gets a pretty good boost on clear winter days with snow on the ground. Even if the top side has snow, the panels can still make power from backside scatter. IMHO they should have built in heaters powered from the back side. Fit them with a thermostat and a cutoff for when the front side is clear. For temperate climates, covering the ground beneath and around with white gravel, or having the roof underneath white, works well. Of course the panels have to be far enough above a surface for best backside performance.
Bifacial panels are being used in vertical installs, oriented north-south. Tests have shown that overall they generate the same power per day as panels facing the Sun, but the distribution is spread towards morning and afternoon, with a dip mid-day. Angled reflectors alongside the panels can pump up the mid-day output.
Yet another development is water cooled solar panels where a plate covering the back side has water channels through it. The water boots power output by taking away heat, and the heated water can be used for heating a house, swimming pool, greenhouse etc.
