The evolution of oil prices is typically subject to a very high degree of uncertainty, given the extremely volatile nature of conditions that affect prices. Information on the future of oil prices is, however, extremely important for market operators as well as for central banks. Central banks, in particular, have a forward-looking perspective, attaching a very important role to inflation forecasts. This uncertainty tends to reinforce the importance of the relationship between oil prices and inflation, independently of estimates of the effects of a permanent change in oil prices on inflation and how to forecast oil prices. Two alternative technical assumptions on oil prices are worth mentioning: (more…)

Energy quality is the relative economic usefulness per heat equivalent unit of different fuels and electricity. One way of measuring energy quality is the marginal product of the fuel, which is the marginal increase in the quantity of a good or service produced by the use of one additional heat unit of fuel. These services also include services received directly from energy by consumers. Some fuels can be used for a larger number of activities and/or for more valuable activities. For example, coal cannot be used directly to power a computer whereas electricity can. The marginal product of a fuel is determined in part by a complex set of attributes unique to each fuel: physical scarcity, capacity to do useful work, energy density, cleanliness, amenability to storage, safety, flexibility of use, cost of conversion, and so on. But also the marginal product is not uniquely fixed by these attributes. (more…)

Now it is possible to move back in the process of technological change from diffusion to innovation. In the energy efficiency area, it is helpful to think of the innovation process as affecting improvements in the attributes or characteristics of products. This process is represented as the shifting inward over time of a curve representing the trade-offs between different product characteristics for the range of products available on the market. (more…)

Interest in rating the real-life energy performance of buildings has increased in recent years, and the real life efficiency performance rating of buildings is important for any sustainable energy future. (more…)

Fuel efficiency gains due to technological and operational change can mitigate the influence of growth on total emissions. Increased demand has historically outpaced these gains, resulting in an overall increase in emissions over the history of commercial aviation. The figure of merit relative to total energy use and emissions in aviation is the energy intensity (EI).

When discussing energy intensity, the most convenient unit of technology is the system represented by a complete aircraft. In this section, trends in energy use and energy intensity are elaborated. In the following section, the discussion focuses on the relation of energy intensity to the technological and operational characteristics of an aircraft.

Reviews of trends in technology and aircraft operations undertaken by Lee et al. and Babikian et al. indicate that continuation of historical precedents would result in a future decline in energy intensity for the large commercial aircraft fleet of 1.2–2.2%/year when averaged over the next 25 years, and perhaps an increase in energy intensity for regional aircraft, because regional jets use larger engines and replace turbo- props in the regional fleet. When compared with trends in traffic growth, expected improvements in aircraft technologies and operational measures alone are not likely to offset more than one-third of total emissions growth. Therefore, effects on the global atmosphere are expected to increase in the future in the absence of additional measures. Industry and government projections, which are based on more sophisticated technology and operations forecasting, are in general agreement with the historical trend.

Compared with the early 1990s, global aviation fuel consumption and subsequent CO2 emissions level could increase three-to sevenfold by 2050, equivalent to a 1.8–3.2% annual rate of change. In addition to the different demand growth projections entailed in such forecasts, variability in projected emissions also originates from different assumptions about aircraft technology, fleet mix, and operational evolution in air traffic management and scheduling.

We shows historical trends in energy intensity for the U.S. large commercial and regional fleets. Year-to-year variations in energy intensity for each aircraft type, due to different operating conditions, such as load factor, flight speed, altitude, and routing, controlled by different operators, can be 730%, as represented by the vertical extent of the data symbols. For large commercial aircraft, a combination of technological and operational improvements led to a reduction in energy intensity of the entire U.S. fleet of more than 60% between 1971 and 1998, averaging about 3.3%/year. In contrast, total RPK has grown by 330%, or 5.5%/year over the same period.

Long- range aircraft are B5% more fuel efficient than are short-range aircraft because they carry more passengers over a flight spent primarily at the cruise condition. Regional aircraft are 40–60% less fuel efficient than are their larger narrow- and wide-body counterparts, and regional jets are 10–60% less fuel efficient compared to turboprops. Importantly, fuel efficiency differences between large and regional aircraft can be explained mostly by differences in aircraft operations, not technology.

Reductions in energy intensity do not always directly imply lower environmental impact. For example, the prevalence of contrails is enhanced by greater engine efficiency. NOx emissions also become increasingly difficult to limit as engine temperatures and pressures are increased—a common method for improving engine efficiency. These conflicting influences make it difficult to translate the expected changes in overall system performance into air quality impacts. Historical trends suggest that feet-averaged NOx emissions per unit thrust during landing and takeoff (LTO) cycles have seen little improvement, and total NOx emissions have slightly increased. However, HC and CO emissions have been reduced drastically since the 1950s.