2-4 joules is basically nothing. There is no chance something like this pays back the energy used to make it within its usable lifetime. It may have some use in

2-4 joules is basically nothing. There is no chance something like this pays back the energy used to make it within its usable lifetime. It may have some use in niches where you need to power some low-power electronics away from the grid, but those also don't tend to be areas with a lot of foot traffic.