For thermal, read "fossil fuels" -- coal and natural gas, the very things that are melting the poles. Image via Wikipedia
Jeff is using nice round numbers, and siding optimistically more often than not, but his goal is to see what it will take to simply offset the energy lost from the declining availability of oil as we slide down the far side of Hubbert's Peak by converting to renewables. Jeff puts that figure at about 5% attrition as a round number which has historical precedent, and then converts the current Oil use in the world into BTU's for lack of a better unit, and then finally converts that into electricity as that is what renewables are good at. The result of offsetting 5% of our current annual oil use with elecricity? 900,000 GW hours.
Lets put that into a measurement that we are used to seeing on our monthly bills: KWH. 900,000,000,000 KWH. Frankly that is a number too big to even comprehend. So I tried to convert it into how many gasifiers we would need to build to make that much electricity since we can make 40,000 KWH each. Yep LOTS better – we only need to build 2.25 billion gasifiers and cut down 3.5 milllion square miles of willow coppice annually to power them. And that is only to replace what we are losing each year, i.e. we have to build that many EACH YEAR just to maintain our energy status quo. That also means we will need to build 1000% more PV and Wind generators than we did in 2008 (the current record holder) and then do it EVERY year, for the next 40-50 years. Considering the best PV is only getting 15 watts per sq ft that is an amazing amount of area to cover.
Conservation and efficiency gains you ask? We can only pray that it offset the dual demographic pressures of rising population and the desire of the Third World to drive an F-150 to eat a Big Mac for lunch every day, and I didn't even get into EROEI, front loading the carbon emissions to retool our society, or the fact that there simply may not be enough copper left to wire the generators that we will need. Something to think about next time you see that cheery bumper sticker about "The Answer is blowing in the wind…" or "The Answer Comes up Every Morning". PV and especially wind generation will certainly have a huge role to play in our future, likely the same critical role as they did to electrify the farms of great grandparents; I am rapidly becoming convinced that Energy DESCENT is the reality – and that the Status Quo is already living History.