The latest addition to the NSS Space Solar Power Library is a paper by Al Globus which he presented at the 2011 International Space Development Conference: Towards an Early Profitable Power Satellite Part II. Globus investigated technologies and designs that could deliver small, operational single-launch power satellites for niche markets. A reasonably sized R&D program could jump start the project into a vigorous space solar power industry. Indeed, the necessary precursor work may be significantly easier than the paper suggests, with an almost 31% efficiency under space conditions. And if you missed it, here is Part 1 of the paper from 2010.