Excerpts from the report
Executive Summary
Because of the inevitable depletion of fossil fuels and the corresponding release of carbon to the environment, the global energy future is complex. Some of the consequences may be politically and economically disruptive, and expensive to remedy. For the next several centuries, fuel requirements will increase with population, land use, and ecosystem degradation.
Current or projected levels of aggregated energy resource use will not sustain civilization as we know it beyond a few more generations. At the same time, issues of energy security, reliability, sustainability, recoverability, and safety need attention.
We supply a top-down, qualitative model—the surety model—to balance expenditures of limited resources to assure success while at the same time avoiding catastrophic failure. Looking at U.S. energy challenges from a surety perspective offers new insights on possible strategies for developing solutions to challenges.
The energy surety model with its focus on the attributes of security and sustainability could be extrapolated into a global energy system using a more comprehensive energy surety model than that used here. In fact, the success of the energy surety strategy ultimately requires a more global perspective. We use a 200 year time frame for sustainability because extending farther into the future would almost certainly miss the advent and perfection of new technologies or changing needs of society.
I. INTRODUCTION
Energy surety is an approach to an “ideal” energy system that, when satisfied, enables the system to function properly while allowing it to resist stresses that could result in unacceptable losses. The attributes of the energy surety model include safety, security, reliability, recoverability and sustainability.
One way to gain insight into energy surety is to study the thermodynamic limitations imposed by well-established physical principles. Seeking sustainability changes the energy perspective from a “scarcity mentality” to one motivated by an “abundance mentality” that seeks to supply energy requirements without damaging the natural environment that supports humanity. The scarcity mentality underlies conventional supply-and-demand economics, and also underlies the philosophy that limiting use will stretch the supply of resources to sustain us. The abundance mentality must include efficiency and conservation, but it also aims to provide as much energy as is required for a prosperous existence. It does so in a responsible manner, making the best possible use of exergy resources, and not necessarily taking the path that would be dictated by purely economic motives. Some regulations and incentives might be used.
From a thermodynamic point of view, sustainability can be described as continuously being able to match exergy sources with exergy needs. Exergy is energy available to do useful work, considering the energy available from a given source within its particular environmental surroundings [footnote 1]. Giving full consideration to exergy use includes choosing the best mix of fuels, and applying conservation principles to all steps, starting with energy production and ending with final use, even utilizing what would normally be characterized as waste heat and mass. A high-exergy fuel is optimal for conversion to electricity, while a low exergy fuel might be used for space heating, for example.
The optimal exergy solution may not always be the most satisfying economic solution.
This supply-demand matching, if it is to be done without disrupting environmental features valued by society, requires closing the energy cycle by managing emissions and other activities that interfere with the environment. Emissions, water use, and land use changes can adversely influence sustainability and social equity. Matching also requires that we utilize current exergy sources in ways that allow seamless movement toward using other new exergy sources as current ones grow scarce.
Energy is a component required for fulfilling nearly all needs for sustaining society, but much energy is wasted, and little emphasis is placed on guaranteeing sustainable energy supply and on using energy sources to their fullest advantage. To emphasize the need to better appreciate the sustainability aspects of energy, the term exergy is used almost exclusively. The reader who may find that term difficult should recognize that when energy available from any source is being utilized to its full advantage, no exergy is wasted.
Energy and exergy are often interchangeable in this report. The working definition is that exergy represents the maximum beneficial use available from an energy source, given the surroundings. As an example, the exergy available from a given fuel may be greater in a location where plentiful cooling water makes it possible to generate electricity more efficiently. If the waste heat can instead be used for space heating or as part of an industrial process, even greater exergy might be available. What is lowest cost may not best conserve resources, and some advocates of imposing exergy-based mandates propose using taxes or financial incentives to maximize the best use of exergy. This report does not discuss the merits of such measures.
Applying these insights to the U.S. exergy infrastructure suggests several steps in a path toward exergy surety. A national goal should be to use our understanding of exergy to slow the trend of depleting the earth’s available limited fuel supplies and to accomplish two other important goals:
close or manage the cycle of emissions from energy conversion and reduce the magnitude of such emissions by applying exergy analysis and
make possible the use of on-demand exergy resources by future generations.
This second goal would use more processes with persistent sources (solar; wind, nuclear—with fuel enhancement such as reprocessing and breeding; geothermal; tides; and coal with sequestration [footnote 2]. Fully accomplishing these goals may not be possible, but striving toward them is far better than blindly marching toward energy depletion, environmental exhaustion, and esthetic despair, only to discover that the scarce remaining resources are inadequate to produce the required new infrastructures.
Examining current and future energy options from a surety approach provides some interesting insights and provides one way to understand energy challenges in an uncertain and changing world. A complete application of the surety model can only be valid if all the components of the system (including the earth and biosphere) are understood and quantified. This may be possible in the future as knowledge of the earth’s complex systems advances. The attributes of sustainability are complicated, multidimensional, and deserving of additional study, including relationships between exergy usage and population growth.
This report argues that sustainability can be achieved up to some limiting carrying capacity of the U.S. and the world, but carrying capacity also includes some assumptions about living standards, social equity, esthetic expectations, and desires of mankind. The limiting carrying capacity depends upon available exergy supplies and our wiser use of them, including the exergy content of waste streams, but there are other limits based on available land and environmental factors, even if environmentally acceptable exergy supplies are without limit. In other words, if humankind becomes more symbiotic with the earth, future generations will enjoy the same prosperities that we enjoy today. Finally, several aspects of the surety approach warrant additional discussion and study.
1 Exergy is a measure of the usefulness of a unit of energy. The word comes from the Greek elements “ex” meaning “out of” and “ergon” meaning “work.” So, exergy means the fraction of the total energy that we can extract to deliver as work. Exergy can also be viewed as energetic order, ordered energy or available energy. It is also important to note that energy contains exergy only when that energy is out of equilibrium with its surrounding environment. For additional insights on exergy, see references [1] and [2].
2 At current use rates, coal use may be sustainable for more than the 200 year time frame we set here. (The Energy Information Administration notes that reserves were sufficient for 250 years.) With that assumption, and also assuming that coal use includes sequestration of carbon dioxide emissions, we include it in the sustainable fuel category, but we recognize that this categorization is debatable. More recent estimates of coal supply at current use rates indicate that the US may have as much as 450 years of reserves [Max Valdez, Sandia National Laboratories, private communication]. See reference [EIA, 1995, Coal Industry Annual, 1994 US Department of Energy Annual report, DOE/EIA-0584 (94), 265 p.].
II. BACKGROUND AND OVERVIEW
Global energy challenges for the mid-term (5–20 years) and the long-term (20–200 years) are different. In the near term, large, growing economies such as China’s and India’s are expanding their roles in the global economy and are consuming energy at an increasing per capita rate. This means increased competition for materials and energy as well as likely increased pollution of the environment.
In the mid-term, depletion of oil and natural gas may reduce supplies and threaten the global economic expansion. For transportation—which is almost exclusively dependent on oil—the crisis may occur well before most people have anticipated. Potential negative consequences to societies worldwide could be unprecedented. For the U.S., transportation is key to the current way of life, so a fuel disruption would severely impact the economy. Potential consequences may be even more detrimental because oil and natural gas are currently the preferred feed-stocks for most of the chemical industry. Substitutes can be manufactured from coal but are more costly, and if coal were to be used to make synthetic liquid fuels, the sustainability of coal supplies would diminish, and carbon emissions would rise, presenting more need for sequestering or reprocessing emissions.
~~~~~~~~~~~~~~~ Editorial Notes ~~~~~~~~~~~~~~~~~~~
The Sandia Labs report is available to the public Toward an Energy Surety Future (PDF - 42 pages).
The report seems deeper and more comprehensive than the usual report on energy.
-BA
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