Scaling Sustainable Energy Options in Terms of Accessibility, Availability, and Acceptability of Options

Society thrives on the secure and reliable flow of affordable energy to industries, homes, public service facilities, communication systems, and transportation systems. Because energy is the lifeblood of the economies of nations and a primary factor in the technology deployment plans of industrial entities and public agencies at all jurisdictional levels, it is essential to the operation of society. Accidental or intentional disruption of energy systems (generation, flow, and use) can cause high-cost damages. Analyses by the International Energy Agency (IEA) in 2001 (http://www.iea.org/technol) indicate that world energy use will rise by 57% by 2020 at an average annual rate of 2%, using 1997 as the reference year. Globally, fossil fuels (oil, gas, and coal) are expected to account for 90% of the primary energy mix by 2020. Oil is expected to provide 40% of the primary energy mix to support mostly transportation in the technologically advanced countries and power generation in developing countries. Furthermore, regional shares in global energy demand will shift from the advanced countries to the developing world. Although coal use will rise in absolute terms, its share in the energy mix will decrease in favor of renewables and gas. By 2020, emission rates of ${\mathrm{CO}}_2$ from fossil fuels are expected to increase by 60%, relative to 1997, at an annual rate of 2.1%.

That scenario is underlain by the assumptions that the global economy will grow at a rate of more than 3% per year; the rate of growth of the global population will decrease; and fossil fuel prices will remain relatively constant, at approximately US$21 per barrel (in 2001 dollars) until 2010. Large uncertainties characterize energy demand and supply projections. The energy mix may change drastically in response to global and regional politics, energy policy reforms of nations, technological advances in energy efficiency of appliances and automobiles, fuel substitution, and development of environmentally friendly energy technologies. Particularly, technological advances can serve as an enabler for the improvement, acceptance, and implementation of options that would otherwise have gained smaller segments of the energy mix. Although global energy demand and supply factors are worthy of coordinated treatment in an increasingly interdependent world, direct implementation of sustainable energy systems is more feasible on a regionalized basis, where the following three factors recognized by the World Energy Council (http://www.worldenergy.org/wec-geis/news) as indices of energy sustainability can be assessed:

A complex web of sociopolitical, technical, natural resource, and logistical factors determine the accessibility of various types of energy resources in each country or region. In some regions, an energy resource such as oil may be logistically accessible but not affordable to a large segment of the population. This is the case with oil in some developing countries where poor refining and product distribution systems frequently cause scarcities. Although energy resources, particularly electricity, are generally available and reliable in the technologically advanced countries, transient but large-scale interruptions are becoming more common. In many parts of the world, low-efficiency energy systems still occupy a large segment of the energy mix. Coal combustion technologies are still at non-optimal efficiencies in North America, Asia, and Africa. Biomass from which is extracted only 5 to 15% of total energy content, constitutes as much as 40–60% of all energy use in developing regions. More-recent data are not available but it is unlikely that they would show dramatic deviations from the range estimated. At a more macroscopic level, the energy efficiency of a political or economic entity can be defined as the rate at which energy converts itself or materials into marketable products or services, as expressed in energy consumption per unit of output. High energy intensity does not necessarily imply high energy efficiency. Perhaps, the most critical index of energy sustainability is energy acceptability. It is characterized by conflicting socioeconomic interests. As in the case of nuclear energy, technical efficiency may not translate to acceptability in all places. Real and perceived risks of immediate and long-term environmental degradation, human health damages, and accidents are the primary driving factors in energy acceptability. Global climate change has emerged as the biggest concern with respect to environmental and human health impacts of energy.

Technological developments can change the scores of each type of energy resource on the three previously outlined energy sustainability indices. Indeed such developments can alter scenarios of future energy mixes for regions and countries. However, the deployment of advanced technologies will require trade-offs among energy affordability, availability, and acceptability. For example, as estimated by the International Energy Agency (IEA) in 2001, a 500-megawatt natural gas-coal-fired power plant that incorporates ${\mathrm{CO}}_2$ capture can attain an 80% reduction in ${\mathrm{CO}}_2$ emissions at an electrical generation efficiency loss of 8–13% and an increase in capital costs of 50–100%, within a ${\mathrm{CO}}_2$ capture and storage scheme that would cost US$40–$60 per ton of ${\mathrm{CO}}_2$ avoided.

To exhibit advances in technology, techniques, methodologies, and policies for enhancing the sustainability of energy systems, this special edition of the ASCE Journal of Energy Engineering is devoted to “Sustainable Energy Systems.” This relevant issue includes the following: