The solar camping bike trailer is for those who like to tour and camp, and the trailer too could have batteries and even side folding "wings" to increase the area if required. I've seen lots of light weight bike trailers for those who like to bike tour.
If circumstances are right an ebike is a good economical choice for many, but bikes are not driven here in winter even though we are further south than you. However, the winters are getting shorter with warm spells and late arrivals. I figure the ebikes will get cheaper as the batteries get cheaper, right now fire safety is a concern for many and insurance companies, but future safer batteries should deal with that. At the rate battery factories are going up with the variety of chemistries and improvements coming on stream that cheap batteries are just a few years away.
If you’re going to use a trailer anyway than sure, why not add some solar on it. It’s not like people here don’t charge ebike batteries from solar, like on a camper, and plenty of people experiment, just never seen one do it while they’re driving it. With a little help you can drive for 6 hours straight at top speed of 25km/h, less with trailer of course but still plenty. A spare battery gives you a total of 8 hours, more than enough for a day, charge both overnight, and costs only 200-500 bucks. With a typical price of 2000 for the bike including battery they won’t get much cheaper regardless of battery advances. In practice that just means you get more range, lifetime and/or faster charging, not a cheaper bike.
These have been for sale since 2013, company went bankrupt in 2019.
As for fire safety, it does happen, at least weekly, most commonly by using cheap chargers from ali or bad choice of charging spots. Gotta educate consumers for sure. But with 5million ebikes, that‘s rare enough to cover. Fires caused by people charging phones and tablets is more common and isn’t stopping anyone from using those either. Battery fire phobia, didn’t know that was still a thing.
Most people do continue to use their bicycles during winter here indeed, ebikes only make that easier (driving a bicycle in winter takes more energy). An alternative, slightly more suitable during colder months especially with windscreen and helmet:
These e-scooters were expected to become very common before the ebike took most of the pie. The above is an example of a “share scooter”. Parked at differents spots throughout cities. Costs roughly 25 cents per minute, 45km/h tops, range 40-60miles too. It’s activated and payment is handled via an app. At destination, or anywhere, park it. At night a van picks them up, batteries are replaced, and they are then parked at better spots again (such as train stations).