...Those who seem to argue as if expanding wind and/or PV solar is a no-brainer, never seem to address the intermittent question (much less the horrible economics in the case of solar at least).
Emphasis added - expanding use *is* a no-brainer - it's already happening.
I also find the the title of this thread curious; solar and wind both are "viable" now, in that each is already providing a non-trivial and growing portion of the total energy portfolio in a number of developed and developing countries (no not the majority, but significant and growing nevertheless). For more centralized power generation models, a US example would be Florida Power and Light, which operates from a diverse portfolio of sources, including wind and solar. A look across Europe will show a number of countries with significant wind and solar contributions to their overall energy mix. China is making huge investments in wind and solar, for domestic use and as an export industry. Yes, it's still pales in comparison to their use of coal, but it is indeed expanding.
With smaller scale, household or other individual sources and net metering in the mix, the potential for overall contribution to reduced demand for home and building related power requirements is enormous, with at least some peak period excess generation put back into the system.
Households putting peak-period over-generation back into the system gets to the problem of intermitttency that OP alludes to. The more pragmatic shorter term solutions that I see proposed in that regard (on both regional and larger scales) include 1) a diversified portfolio of energy sources and generation points (sort of like our retirement portfolios, eh?) to include wind, solar and other renewables, in addition to nuclear, coal (clean coal being the goal), gas and others. 2) smarter generation and transmission gird with variable capacity among the more persistent sources.
There are indeed challenges here, but as Bill Gates seemed to be saying toward the beginning of the TED talk linked in OP above. "All" of the solutions have challenges (in reaching the goal of providing economically viable energy, in sufficient quantities, delivered when and where it's needed, while minimizing CO2 emissions). The likely solution will involve multiple technologies/sources. Solar and wind are a part of that solution now, and every indication is that they will increased their contribution going forward.
An interesting project related to this discussion is the DOE Solar Decathlon (
U.S. Department of Energy Solar Decathlon Home Page). About twenty student teams from different universities design/build solar houses and set them up in DC for judging and a week-long performance competition. The houses are great and I highly recommend that anyone who has the opportunity to go to DC during the week they are there do so. Talk to the students. Most of the homes achieve net-zero metering or greater (i.e. they generate more power then they use). They still are comparatively pricey, but many of the subsystems are off-the-shelf commercial components, so this isn't pie-in-the-sky futurism. The students typically are very sharp, very motivated and believe in the future of what they're doing.
