I think you're more likely to find a solar powered home with a sewing machine inside than an actual solar powered sewing machine. IIRC the older Singer motors are already rated for 12VDC as well as 120VAC. I don't think any special mods would need to be made to run one on solar power.
I have a pretty good interest in alternative energy but a very small practical knowledge base. CD I think you did help with the push toward less reliance on fossil fuels by buying the wind energy rating so it's not entirely just "in name only" regardless of the ultimate source of your power. As more people buy the rating the power company will have to build more wind towers to meet the demand for that source of power. Hybrid systems are worth looking at too with part of your power supplied onsite by solar or wind with the rest coming off the grid. No need for a bank of batteries that way. I'm a big believer in a non-centralized power grid. I think it's much more reliable to have many small sites producing power instead of one large facility supplying all of it. A solar water heater is also a good step in the right direction. Direct conversion of solar energy to heat is very efficient. I think it would be nice if all new construction had to supply at least 10% of their energy onsite. That would be a good start. One good thing is many businesses are taking steps toward renewable energy and more eco-friendly, energy efficient buildings voluntarily.
Even if everything does eventually go solar I think there will still be people who treadle, if for no other reason than they enjoy it.
Rodney