Review of energy solutions to global warming, air pollution, and energy security.

A presentation from Dr. Mark Z. Jacobson of Stanford University

By William A. Thomas, CSSP Board member

Dr. Mark Z. Jacobson of Stanford University presented a "Review of energy solutions to global warming, air pollution, and energy security." 

I found this to be a remarkably comprehensive study of the many factors in a quantitative evaluation of the options to meet the needs for energy supplies. For example, computation of carbon production includes the output from construction of the necessary infrastructure, not simply the operation of the production facility. The calculations also include the impact of other sources of energy during the time from planning to completion of infrastructure, as well as the lifetime and replacement cycle of facilities. Somewhat ominously, calculations for nuclear power assume one exchange of nuclear weapons in 30 years, and for coal assume 1-18% leakage of carbon dioxide from sequestration during 1000 years.  These examples illustrate the thoroughness of the computations.

The primary conclusion is that a combination of wind, solar (photovoltaic and concentrated solar power), geothermal, wave, tidal, and hydroelectric can supply enough electricity for all world needs for energy, including battery-electric and hydrogen-fuel-cell vehicles.  Furthermore, these alternative sources of energy have a much smaller impact on atmospheric composition (both greenhouse gases and other pollutants) than do coal (even with carbon capture and sequestration), ethanol, or nuclear.

The analysis begins with a ranking of effects and impacts of energy production, including abundance of resources, carbon dioxide emission, air pollution, water consumption, footprint on the ground and required spacing, ability to match peak demand, effects on ecosystems, thermal pollution, and water pollution.  Combining these factors with total energy needs supports an evaluation of the capacity of each alternative for replacing 100% of energy needs in terms of resources, materials, adequacy of supply, costs, and politics. Comparisons for transportation included battery-electric vehicles, hydrogen-fuel-cell vehicles, and combustion-engine vehicles using ethanol.

An evaluation of wind resources shows that wind over land with adequate speed (greater than 7 m/sec) could produce 70-170 terawatts, whereas the world demand estimated for 2030 is 16.9 terawatts. Similarly, the potential for solar power over land is approximately 340 terawatts. Modeling shows that short-term variations in supply from wind and solar resources can be resolved by the use of both, in addition to hydroelectric and geothermal power, to fulfill peak demand.

Comparisons of carbon dioxide emissions show that wind, solar, geothermal, tidal, wave, and hydro are relatively low with respect to nuclear (9-17x wind) and coal with carbon capture and sequestration (41-53x wind).  Emissions of other pollutant gases from the use of ethanol are similar to or greater than those from use of gasoline, and are significantly greater than those from coal.  Perhaps the most surprising result from these studies is the recognition that ethanol (both corn and cellulose) ranks approximately equal with conventional petroleum in terms of emissions, and ethanol has a serious negative impact on water resources. These observations lead to the conclusion that investments in ethanol production will be counterproductive to the development of more efficient long-term energy sources.

The long-term sustainability of energy sources is, of course, dependent on resources of raw materials. Because electricity is significantly more efficient than combustion engines, which lose a high percentage of energy to heat exhaust, more comprehensive use of electricity would reduce the overall demand for energy. Nevertheless, greater use of electricity will greatly increase the demand for batteries, raising the question of supply of raw materials for making batteries. Simply put, lithium-ion batteries require lithium.  Speaking from my perspective as a geologist, I asked Mark about the known supply of lithium, and he is assured that adequate supplies are already known. The known supplies, however, are primarily in South America, dominantly in Chile and Bolivia. Even if some of the presently unquantified supplies are valid, the long term will require careful recycling of battery materials.

I came away from this presentation awed by the elegance and thoroughness of the computations. It carries a message of optimism for future supplies of energy, but it carries a strong message of caution. Quantitative evaluation of alternatives, including many independent variables, is necessary to understand the positive and negative impacts of each potential source of energy. The need for rigorous science in the approach to policy has never been more thoroughly documented.