It's not a report, it's an almost 400 page book. He doesn't compare random energies, instead he looks at what, under reasonably generous conditions, the daily power budget each energy source could provide per person. The very generous 20kWh/d of power per person is the key point. 6 m/sec is already high, with few places reaching such speeds consistently. And almost no one will reach double that, so you can look at an optimal 17 W/m^2 for wind.
http://web.stanford.edu/group/efmh/winds/global_winds.htmlIn chapter 25, he acknowledges that while the cost of photovoltaics will fall, he does not see it doing so in a timeline that will be useful in terms of getting everything deployed for a ~2050 deadline. Economically speaking, carpeting deserts with concentrating collectors will be the cheaper of the solar options. The book is careful about doing all the math, citing all its sources and carefully explaining the scenarios it models. It is a very good book[+].
But cost is not the only issue—even as prices fall, there is still the problem of land use area. Efficiencies aren't going to pass 30% (without going to much more expensive materials) and for mass production, we can halve that; cheap as panels may someday become, places with high pop densities (on top of seasonal variations/not being near the equator) are going to have trouble meeting their needs. Especially if they don't want to get rid of their curling irons, hair/clothes dryers, toasters and electric stove/kettles. But panels/turbines aren't the whole picture.
Already today, panels take up only a fraction of the cost of solar. You ideally, want an MPPT controller. You might need voltage regulators, you'll need a rack for the panel and batteries, an appropriately sized inverter, wiring and installation. Batteries—to save more money long term—you want to oversize them so you rarely hit a low depth of discharge. But more batteries means more panels. You also want enough batteries such that you can wait out ~4 days of low light (speaking from experience, on cloudy days you can go the entire day at ~13% typical amp output). Even those at the equator will only get ~6 good hours of sunlight (~8 hours for an appreciable amount), so even for the best case scenario, 12 hours of storage per person is not going to cut it. Solar is great but it's no panacea. And the math doesn't work out for chemical energy storage. Molten salt storage, compressed air look to be more logical at the grid level but even they won't be sufficient.
That said, Mr Theil is also incorrect to place Nuclear in opposition to renewables. Renewables will be in addition to Nuclear [-]. As well as looking into more DC appliances, more HVDC and working out circuit breakers for them, optimal manufacturing layouts such that 'waste output' can be redirected to where it is needed. More energy efficient devices, energy routing algorithms (and a global grid of superconducting HVDC while we're at it—seems far fetched but still at a much higher technological readiness level when compared to fusion), better city planning, climate control with geothermal heatpumps, more material reclamation and recycling, nuclear waste as fuel, carbon capture, extracting CO2 from the ocean for fuel and a cultural move away from an over consuming disposable society.
[+] I am biased in that I'd already known the author for one of the best free books on information theory and machine learning. Anyone interested in the link between learning, energy and thermodynamics should see this book as a starting point. http://www.inference.phy.cam.ac.uk/itprnn/book.pdf
[-] Ch. 24 of sewtha.pdf goes into numeric data backed detail on why most build out, waste, cost arguments against nuclear are weak. Personally, I think at best, we only have a couple hundred more years where we can all be justifiably irrationally paranoid over Nuclear. We should have DNA repair down by then.