[minthd]

I think that in most cases, using a rechargeable battery is cheaper - and cheaper leads in most areas of embedded systems.Also most embedded systems need power for something like motor/lcd/relay/etc and energy harvesting cannot supply enough energy for that - and the issue of wireless connectivity of such networks is only partially solved and not yet mature i think. And even the micro-controllers are only half way there.

Also the places that could use energy harvesting are sensors networks in industry and building, and those are quite conservative industries(for good reasons) and they greatly care about reliability, and also the field of sensor networks for industry is not fully developed with applications like predictive maintenance are quite new. Same goes for the medical industry , where such sensors could be valuable.