Transition to Solar or Wind Presents Practical Challenges
Entrepreneurs Hard at Work Finding Solutions
BY PETE GEDDES
Coal is a ubiquitous and relatively inexpensive resource. Montana holds one-third of all U.S. coal deposits, representing about 8 percent of the world’s total. The International Energy Agency reports that between 2000 and 2007, global coal use increased by 4.8 percent. That’s three times the growth of oil consumption and nearly twice the rate of natural gas.
Each day, the world consumes coal in the energy equivalent of about 64 million barrels of oil. China’s average daily consumption alone is the equivalent of 26 million barrels. In 2007, the amount of energy America generated from coal exceeded the total energy consumption from all sources in all of the countries of Central and South America combined.
In addition to emitting CO2, coal is the dirtiest of the fossil fuels. Toxic heavy metals, such as mercury, are particularly nasty byproducts. Coal contains trace amounts of the radioactive elements uranium and thorium. When coal is burned into ash, theses elements are concentrated at up to 10 times their natural levels. Hence, a typical coal-fired power plant releases about 100 times as much radioactivity as a comparable nuclear plant.
Is solar a viable alternative? It has the potential to generate vast amounts of carbon free, clean energy, but currently contributes less than one tenth of one percent of total U.S. energy consumption. Its main limitation is that storage of solar energy is prohibitively expensive.
Utilities must balance energy supply and demand instantaneously, round the clock, day or night, 365 days a year, in good weather or bad. To assure reliability, utilities back up base load generation with power from natural gas fired plants. If solar is to make a meaningful contribution to base load electricity generation, say on par with nuclear, at about 20 percent of U.S. generation, we must find a way to cheaply store the energy it creates.
Current options include pumping water uphill where it can be released through a turbine to generate electricity when demand arises. Storing enough energy this way requires filling (and emptying) massive reservoirs every day. This is particularly problematic in super sunny (but water limited) Arizona and Nevada. What about batteries? Although improving, they still store far less energy than conventional sources, e.g., gasoline. (The best batteries store about 300 watt-hours of energy per kilogram, while gasoline stores 13,000.)
From Bozeman to Beijing, thousands of entre-preneurs are working on the transition to a clean energy future. Here’s an example of some of their work. Through electrolysis hydrogen and oxygen gas are separated from water. At industrial scales this process requires high temperatures, harsh solutions, and expensive metals. Using photosynthesis as their model, MIT scientists have created an inexpensive metal that splits water into hydrogen and oxygen at room temperatures. They propose using solar power to liberate hydrogen gas from water. The easy-to-store hydrogen could then be burned in a standard generator or recombined with oxygen in a fuel cell. If the process can be scaled up, it could make solar power a dominant source of energy.
All modern societies are dependent on massive and incessant flows of energy. And in the developing world, increased energy production is an absolute prerequisite for reducing poverty. Fossil fuels are currently the choice for meet this growing demand. Why? Because they are easily storable, have high-energy densities, and provide reliable generation. (Coal-fired generating stations operate with high load factors, i.e., they operate 75 percent of the year, and nuclear plants are above 90). In contrast, wind and solar are intermittent and hence they can never deliver power consistently. Annual load factors of wind generation in Denmark, Germany, and Spain, are just 20-25 percent. (This means these wind turbines sit idle for an equivalent of 270-290 days a year.)
There is no easy, cost-free way to speed our energy transition. It is not a relatively simple engineering problem, like the Apollo or Manhattan projects. Instead, we face complex socio-economic issues. Looking at history, Vaclav Smil of the University of Manitoba observes, “There is one thing all energy transitions have in common: they are prolonged affairs that take decades to accomplish, and the greater the scale of prevailing uses and conversions the longer the substitutions will take.”