A frame with a solar panel and a storage battery mounted on it functions as a power generator, for all intents and purposes. Quite a lot of vehicle-mounted appliances have been added recently, from minifridges to electric kitchens to forges and chemistry labs. It’s not particularly complicated to put one together once you have all the materials.
Construction items have been added to the .jsons, so I don’t think it would be too hard to make an item that functions similar to a storage battery as a furniture item. The question becomes how to connect faraway appliances to the generator? For a vehicle, anything attached to the same frame is connected, but for furniture items, it’d be a bit harder.