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Ultimate Guide to Power Efficiency

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Humans interact with nearly every aspect of the carbon cycle. In the past, trajectories of emissions and land use change unfolded with little or no reference to their impacts on climate. Now much of the world is ready to make carbon management a priority. The United Nations Framework Convention on Climate Change and its Kyoto Protocol establish initial steps toward stabilizing the climate (Sanz et al., Chapter 24, this volume). In the future, however, much more will need to be done, especially if CO2 concentrations are to be stabilized at a concentration of 750 ppm or lower. The basic problem is that world energy demand continues to grow rapidly. With a business-as-usual strategy, global carbon emissions could exceed 20 PgC per year (y-1) (about three times current levels) by 2050 (Nakicenovic, Chapter 11).

Many technologies present options for decreasing emissions or sequestering carbon. Unfortunately, no single technology appears to have the potential to solve the energy problem comprehensively within the next few decades (Caldeira et al., Chapter 5, this volume). Indeed, meeting world energy demands without carbon emissions may require fundamental breakthroughs in energy technology (Hoffert et al. 2002). Even with future breakthroughs, the best options for managing the future energy system are very likely to involve a portfolio of approaches, including strategies for extracting extra energy from carbon-based fuels, technologies for generating energy without carbon emissions, and approaches to increasing sequestration on the land and in the oceans (Caldeira et al., Chapter 5).

Increases in energy efficiency (measured as energy per unit of carbon emissions) typically accompany economic development, and it is reasonable to assume that efficiency increases will continue in the future (Sathaye, Chapter 22). Even with aggressive assumptions about increases in efficiency, reasonable scenarios for the future may result

Figure 1.3. The energy gap, showing the growing difference between the emissions projected in a widely used scenario (IS92a) and the emissions required to stabilize atmospheric CO2 at 550 ppm (with the WRE 550 scenario [Edmonds et al., Chapter 4, this volume]). This energy gap is the target for climate policy. Also shown is the emissions trajectory for IS92a in the absence of endogenous technology improvements. The very large improvements can be expected based on past experience, but they may involve many of the options that are also candidates for closing the energy gap between the emissions scenario (IS92a) and the stabilization scenario (550 ppm constraint). Redrawn from Edmonds et al., Chapter 4.

Figure 1.3. The energy gap, showing the growing difference between the emissions projected in a widely used scenario (IS92a) and the emissions required to stabilize atmospheric CO2 at 550 ppm (with the WRE 550 scenario [Edmonds et al., Chapter 4, this volume]). This energy gap is the target for climate policy. Also shown is the emissions trajectory for IS92a in the absence of endogenous technology improvements. The very large improvements can be expected based on past experience, but they may involve many of the options that are also candidates for closing the energy gap between the emissions scenario (IS92a) and the stabilization scenario (550 ppm constraint). Redrawn from Edmonds et al., Chapter 4.

in CO2 levels well above widely discussed stabilization targets (i.e., 450, 550, and 750 ppm CO2). This is the case for many of the scenarios explored in the IPCC Special Report on Emission Scenarios (Nakicenovic, Chapter 11), leading to a gap between emissions consistent with reasonable advances in energy technology and those required to reach a particular stabilization target. This gap needs to be filled through active policies and could include incentives for new technologies, sequestration, or decreased energy consumption (Edmonds et al., Chapter 4).

The juxtaposition of the portfolio of future options for energy and carbon management with the gap between many economic scenarios and CO2 stabilization creates a problem. A priori, it is not possible to identify a set of options available for filling the energy gap because most or even all of the available options may have already been used in the increased energy efficiency that occurs as a natural part of technological advance (Figure 1.3). Because there is no way to predict the mechanisms that will appear endogenously, there is no simple way to identify an additional set that should be the targets for policy intervention. From a carbon management perspective, the efficiency increases that occur spontaneously make some aspects of the carbon problem simpler, and they make some aspects more difficult to solve. On the one hand, if economic pressures consistently lead to efficiency increases, additional policy tools may not be necessary, at least for some of the efficiency increases. On the other hand, if the efficiency increases in the economic scenarios consume most of the options for carbon management, the costs of developing options for closing the gap may be very high (Edmonds et al., Chapter 4) or they may entail unacceptable trade-offs with other sectors (Raupach et al., Chapter 6).

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