At TED2010, Bill Gates unveiled his vision for the world's energy future, describing the need for "miracles" to avoid planetary catastrophe and explained why he's backing a dramatically different type of nuclear reactor (Terrapower).  The necessary goal?  Zero carbon emissions globally by 2050.

In my view in this talk Bill gets a lot right, including the woefully inadequate level of energy R&D investment, the misplaced investment in deploying uneconomically viable technologies, the inadequacy of current alternative energy solutions, the need to be cheaper, and the need to try a lot of different approaches to improve the odds of success. These perspectives have led him to conclude that nuclear power is the best available option, and putting his money and time where his mouth is he has invested in and promoted a high-risk nuclear power venture called Terrapower.  With his investment in Terrapower he also perhaps inadvertently has created a big angel investment model for what is necessary to get the ball rolling given the inability of the capital markets or government to address the problem.  

Terrapower represents the big R&D investment approach aiming to produce carbon free energy that costs less than energy today.  It is using around $100M to produce paper designs.  It will need billions and a decade to build a test reactor and billions more and another decade to design and deploy production reactors.  It ultimately has to overcome the public skepticism of nuclear power and a whole host of technical problems.  It’s definitely the big R&D approach but relative to the scale of the energy business it is tiny.  It is small even relative to US investment in clean power which mostly funds deployment of technologies that can never realistically compete but satisfies various political constituencies.  

In contrast StratoSolar is solar not nuclear and is a small R&D approach.  It builds on existing PV and construction technologies and materials.  A relatively small investment of $10M builds a test platform in 18 months rather than computer simulations.  Incremental investments develop production platforms and then assemblies of production platforms.  It generates competitively priced electricity in production, so it needs no subsidies.  It simply needs R&D investment.  Energy is so large scale that ramping up production initially may need government guarantees to bolster investor confidence.

This New York Times article outlines the decline and credits the Brookings Institution, The World resources foundation, and The Breakthrough Institute. They jointly authored the following report “Beyond Boom and Bust” that details the decline and policy changes that they argue would make for a more sustainable subsidy regime.  Unfortunately the current political situation does not bode well for reform, particularly if it costs money. 

The current subsidy regime is boom and bust and not focused on technology improvement.  It is classic government subsidies that encourage the status quo and create a class of companies that live on the subsidies without incentive to improve and who lobby to maintain the subsidies regardless of the benefit or lack thereof.  It also funnels money to favored constituencies like government contractors and peer reviewed scientists.  

The main focus should be on technologies that have a realistic chance of economic viability with an honest accounting of costs associated with intermittency and geographic isolation.  Too much of alternative energy is over optimism and pass the buck accounting.  

The alternatives to fossil fuels have several well-known problems, but land use is rarely raised as a limiting factor.  Generally this seems to be because only limited solutions for particular geographies are considered.  This is a simple analysis of land use for all energy for some major industrial countries.  It shows that nuclear, wind and ground solar are very constrained in their ability to scale to a full solution by land use limits alone.

LAND USE km2/TWh/y
                  Nuclear     Wind    Ground PV StratoSolar
exclusion       72            77               13          2.5
occupied       <1             2                13          <1

The table above shows land use in km2 per TWh per year for various energy alternatives.  Exclusion is land area affected but still available for limited use.  For nuclear the exclusion area is the international standard 30km radius evacuation zone.  This is the area of possible permanent contamination in a major accident and rationally should not include any major urbanization. We assume 5GW plants.  For wind the exclusion area is more restricted only allowing agriculture. The area estimate is based on NREL data and assumes an optimistic 5MW/km2. Ground PV exclusion allows for no other use.  StratoSolar exclusion use is similar to nuclear allowing anything but dense urban use.  Occupied shows the land area actually occupied.
                   EIA 2009                           km2           km2       km2             km2            km2
                   QuadBtu      TWh/y       nuclear       wind  ground PV   StratoSolar   Total Land
Japan          21.863          4,000       286,707       307,770     50,701        10,140           377,930
Germany     14.355          2,777       199,021       213,642     35,195          7,039           357,114
France         11.29           2,184       156,527       168,026     27,680          5,536           551,500
England        9.349          1,808       129,617       139,139     22,921          4,584           242,900
Spain           6.508           1,259        90,228         96,857     15,956          3,191           505,370
Italy              7.838           1,516      108,668       116,651     19,217          3,843           301,336
USA            99.278         19,203    1,376,412    1,477,528   243,403         48,681        9,526,468

The table above estimates the excluded land area required by each energy alternative to supply all current energy for the major industrialized countries listed and also lists the land area of each country.  This gives a sense of the scalability of the different resources.  It’s pretty clear that for Japan and Europe wind and nuclear don’t have the room to scale, and ground PV given that it fully uses the land it’s on is also implausibly large.  Even the US would find it practically and politically impossible to find the necessary land, once we exclude mountains, rivers and lakes.

The StratoSolar land area required is by far the smallest, and has the least impact on use, excluding only dense urban.  Based upon this data, StratoSolar is the only viable alternative for a complete energy solution not constrained by the availability of land.