Is Mount Everest the Best Place for Solar Power?

A new study on the impact of regional temperature differences on solar generating potential arrives at some surprising conclusions about the world's best locations for solar power. While the US desert southwest still ranks high, as you'd expect, it turns out that some of the best sites may be in places most of us would never suspect, including the Himalayas and Antarctica. That's because the crystalline silicon-based photovoltaic (PV) cells that dominate the market today are sensitive to ambient temperature and perform best at low temperatures, such as those found in the polar regions and high altitudes. These results could have interesting implications for future energy supply and greenhouse gas emissions in India and China, and for regional cooperation in what has historically been a tense neighborhood.

The paper by researchers from Japan's National Institute for Advanced Industrial Science and Technology was published in Environmental Science & Technology. Their approach involved superimposing mapped global average temperatures onto the map of average solar radiation, or "insolation", that has been the standard guide for assessing solar power potential. This produces some interesting shifts in the world's best solar locations, particularly by reducing the PV potential of the tropics and increasing that of colder regions. (Note that this comparison isn't applicable to solar thermal installations.) High-altitude locations look especially attractive for PV for two reasons: Not only are they colder, with average temperatures falling by 4-10ºC for each kilometer of altitude (12-28ºF/mile), but they also receive more sunlight, due to the thinner atmosphere at these heights.

The resulting differences in output are significant. The same PV module that generates 600-800 kWh/year per Watt of nameplate capacity in the UK or Germany and 1,400-1,600 kWh/W in Arizona would top 2,000 kWh/W in the Himalayas and parts of the Andes, as well as near the South Pole. The authors recognize that the latter might not be very useful without low-cost, high-volume energy storage, perhaps in the form of hydrogen, due to extended periods of darkness in the antipodal winter. I would note that the enormous distances to the nearest market might also be overcome by borrowing some ideas from the plans for space solar power (SSP). Either way, it doesn't take high storage or logistical costs to render large-scale Antarctican PV impractical, and the installation, maintenance and transmission challenges in the Andes and Himalayas aren't trivial, either. Whether the paper's conclusions turn out to be more than just scientifically interesting will depend on the detailed economics of the projects necessary to implement them.

The economics of PV entail a lot more than just the solar generating potential in a given location. Proximity to markets, or at least access to transmission, is a big factor, as is price, including both the market price for power and any relevant government or utility incentives or carbon pricing. However, it's also true that it takes either very high local prices or very high subsidies, such as Germany's solar Feed-in Tariffs, to make PV competitive in regions with low temperature-adjusted solar output. Such subsidies are a rich-country game on any scale large enough to matter, and even European countries are finding it hard to sustain these added costs as their economies teeter on the brink of another financial crisis and recession. The advantages to developing countries like China and India of pursuing high-altitude solar--even if it requires long transmission lines--could be compelling in the long run.