This is something I’ve been interested in too. Here’s some more resources I’ve gathered up:

Technology from the late 1800s, early 1900s combined in new solarpunk ways:

I think there’s a lot of value in using energy in the form we receive it to minimize conversion losses, and in recent discussions I’ve been introduced to a couple new ones: solar steam generators which use trough reflectors or ranks of mirrors focused on long vacuum-lined tubes of water to produce steam which can run steam engines/generators. With clever application of steam storage tanks, they can even store excess pressure to keep it going when it’s dark, and to cycle fluid in the system using excess pressure rather than using pumps. This thread had some really cool info on how these went together and the ages of the various components: https://www.reddit.com/r/solarpunk/comments/1b8048e/comment/ktmjpst/?utm_source=share&utm_medium=web2x&context=3

(It also doesn’t have to be used to turn a turbine or generate power/motion. There’s tons of systems in industry that need steam for sterilization etc: https://solarimpulse.com/solutions-explorer/fresnel-solar-steam-generator-1)

Soda locomotives: fireless steam locomotives where the boiler is surrounded by a tank of caustic soda, which generates heat when water is added, and the steam exhaust is condensed and added to the soda to create more heat. It goes until the soda gets too dilute, but it can be ‘recharged’ by drying it out. These never really took off because it took more coal to dry the soda than to run a similar train, and electric trains quickly came into their own and filled the niche of low-pollution trains for inside cities and tunnels. But I feel like they could pair well with solar furnaces or cookers stationed along the tracks. The locomotive would just exchange wet soda for dry and start again. This has an advantage in being completely analog and able to work on cloudy days or at night, as long as you get enough sunny days to dry out big batches of soda at the stops along the way. And the drying stations are stationary so they can be optimized for their location.

There are also fireless locomotives which are basically just a big steam tank, rather than a boiler, which are filled by an external source of steam where it’s plentiful, like onsite at nuclear reactors, and perhaps certain geothermal ones. That might fit some other use cases.

Waterwheels - preferring the kind that didn’t dam up the entire river but instead guided a part of it into a separate channel, where the waterwheel would be mounted. The remaining river would be undisturbed, which is better for the habitat, while still generating free motive power.

vapor-compression systems these were used in old-fashioned refrigerators but modern technology could optimize the design, and they could be matched with any steady motion from a water wheel etc.

I feel like streetcars are always worth mentioning, just because they were such an effective transport system for cities, even using quite early motors, metallurgy, electrical knowhow, and hitting their stride way before modern batteries that could power the vehicle they’re riding in.

I should also mention solar furnaces, and solar ovens which can produce useful heat with fairly simple components (mirrors and a bit of math) which should be useful in any recovering society

1940s tech:

Woodgas conversions of internal combustion engines I like these because it emphasizes reuse of existing machinery instead of new manufacturing. It doesn’t require high-tech electronics or rare materials for batteries like electric vehicles. And it’s less practical for the kind of quick trip to the store or daily commute which has shaped our current society. A woodgas vehicle takes awhile (ten to twenty minutes to start up), can’t easily be stored indoors, and because the fire needs to burn down, doesn’t make much sense for short trips. But in a solarpunk society, most folks shouldn’t need a car for that stuff – they’d be walking or taking public transit. So conversions like this would be used for special trips – hauling produce to town, supplies out to forest management camps, research sites, and other remote locations. And perhaps for road trips by campers and other people who might borrow one for an adventure. The wood can be sustainably sourced, using scraps from sawmills, harvested invasive trees, brush, and even dedicated coppiced plantations of especially fast growing trees like paulownia elongata. One of the byproducts of gassification is biochar, which can be tremendously useful in compost, and holds carbon for a comparatively long time. I also think its important to note that while this can be done well, when these vehicles were previously used in massive numbers (during WWII) they led to deforestation. They make sense in small doses, and with some careful management of their inputs.

I got a bunch of good info from this person on reddit

Edit: bonus airship rant:

Despite seeing relatively little use, airship design has advanced tremendously in the last hundred years. Improved materials have allowed them to take more effective shapes, and improved engines, motors, batteries, and computer systems, have made them much easier to control. While reading about historical airships, I was struck by the risk in doing almost anything with them, but especially by landing – which often required ground crews (‘landing parties’) of hundreds of men who would by strength of muscle, pull the thing down to the ground. By contrast, modern airships can land themselves right on the ground.

Airships could open up some really cool possibilities: while they lack the speed of a jet, they have more capacity, and lower fuel requirements. While they lack the sheer capacity of a container ship, they’re a lot faster and use way less fuel. They can also fly over land, meaning they can reach all kinds of places ships can’t, and cut long detours around continents or transfers between vehicles. Basically, container ships might be able to carry more, but they’re not as good at going from Boston to Seattle, and they suck at getting to Kansas City. What’s more, airships can act as flying cranes, lifting bulky objects like wind turbines or assembled buildings right over obstacles, and to places where roads or trains simply couldn’t carry them.

Low Tech Magazine has a lot of suggestions for precisely this.

Sterling engines.

Woodgas engines for agricultural machinery.

What technologies wouldn’t work? Are there certain prohibitions in place that make a solarpunk society distinct from other types?