E-Letter responses to:

review: Martin I. Hoffert, Ken Caldeira, Gregory Benford, David R. Criswell, Christopher Green, Howard Herzog, Atul K. Jain, Haroon S. Kheshgi, Klaus S. Lackner, John S. Lewis, H. Douglas Lightfoot, Wallace Manheimer, John C. Mankins, Michael E. Mauel, L. John Perkins, Michael E. Schlesinger, Tyler Volk, and Tom M. L. Wigley Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet Science 2002; 298: 981-987 [Abstract] [Full text] [PDF]

E-Letters: Submit a response to this article

Published E-Letter responses:

Regarding Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet

Richard B. Diver   (24 April 2003)

Slowing population growth

Albert A. Bartlett   (24 April 2003)

Re: Hoffert et al.

Gerald E. Marsh, George S. Stanford   (24 April 2003)

Strategies for dealing with global warming

Ned Ford   (24 April 2003)

The competitiveness of renewable energy

Marco Verweij   (24 April 2003)

High-Temperature Solar-Thermal, a readily available solution

Taw Benderly   (27 November 2002)

Life-cycle Assessment of Energy Technologies

sergio a pacca   (27 November 2002)

Breeder reactors should be considered also

Ira Charak   (27 November 2002)

Ignores conservation

William R. Stewart   (27 November 2002)

Regarding Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet 24 April 2003
Richard B. Diver Sandia National Laboratories, Solar Technologies Department Respond to this E-Letter: Re: Regarding Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet	Although I agree with the article’s conclusion that worldwide efforts to develop the alternative energy production technologies needed to address greenhouse gas buildup in Earth’s atmosphere are sorely lacking, I am disappointed that the technology best able to deal with this impending catastrophe, solar thermal technology, was barely mentioned. Solar thermal electric technologies, including parabolic troughs, power towers, and dish -engine systems are not only the most efficient solar technology available, they are also the lowest cost -- much less than photovoltaics. The ability to incorporate cost-effective thermal energy storage mitigates the intermittent nature of solar resources, permits power production during peak periods and at near “base-load” capacity, and lowers electricity cost. Dish Stirling systems have demonstrated solar-to- electric conversion efficiencies of approximately 30%; the Solar Two power tower near Barstow California produced power continually for 153 hours; and nine solar thermal electric plants totaling 354 MWe generating capacity have been powering~100,000 homes in California for over 15 years. Because these plants are constructed from ordinary materials and power conversion equipment, generating capacity is virtually unlimited and can be increased rapidly. I agree with the author that the amount of land needed to supply 10 terawatts is approximately 220,000 km2. However, given that this is less than 0.15% of the world’s land area and that the best solar resources are generally in desert areas that do not compete with other needs, this is not unreasonable. The expected long-term cost of solar thermal electricity is nearly competitive with conventional fossil fuel or nuclear generated electricity and only needs short-term subsidies to get started. Furthermore, after the cost of the “solar fuel” has been paid off in 20-30 years, the cost of solar electricity will be much less than the conventional alternatives, not even counting the costs of waste disposal or environmental remediation. Richard B. Diver Sandia National Laboratories, Solar Technologies Department
Slowing population growth 24 April 2003
Albert A. Bartlett, Professor Emeritus of Physics University of Colorado, Boulder Respond to this E-Letter: Re: Slowing population growth	In their comprehensive review of advanced technology paths to global climate stability, Hoffert et.al. (1) open with a clear statement of the origin of the problem: "In the 20th century, the human population [of the earth] quadrupled and primary power consumption increased 16-fold" (2). If these rates were to persist through the 21st century, Earth's population would be 16 times larger than in 1900, and the primary power consumption would be 256 times that in 1900. Even without the greenhouse problems, the obvious impossibility of continuing these growth rates would lead rational people to say that the present declines in the growth rates of U.S. and world populations are too slow and that the world's first order of business should be to stop the growth of populations and the growth of per capita primary power consumption. Instead of advocating the obvious, the authors paint a picture of all manner of technological fixes which, at enormous expense, may provide some answers to the need to stop the growth in emissions of greenhouse gases that are associated with energy production. As is so often the case, technological fixes are offered without being reviewed in the light of Eric Sevareid's Law: "The chief cause of problems is solutions" (3, 4). One can be sure that each technological solution will create new problems that are not indicated by calculations, equations, and technical speculations. The article makes it clear that achieving global climate stability won't be easy, but it ignores the first and easiest thing we should do. We should follow the lead of the countries of Europe that all have population growth rates that are presently near or below zero. These countries are making real strides toward sustainability as is indicated in the First Law of Sustainability: "Population growth and/or growth in the rates of consumption of resources, cannot be sustained" (5). Albert A. Bartlett Professor Emeritus of Physics University of Colorado, Boulder, Colorado, 80309-0390 References 1. M. I. Hoffert et al., Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet, Science 298, 981 (2002). 2. It must be stressed that these enormous increases are consequences of negligibly small annual growth rates; of population of 1.386%, of per capita primary power consumption of 1.386%, and of total primary power consumption of 2.77%. 3. E. Sevareid, CBS News, December 29, 1970; quoted in T.L. Martin, Malice in Blunderland (McGraw-Hill, New York, 1973). 4. For instance, when the problem was the need for more electric energy, a solution was nuclear power. But nuclear power has presented a whole new set of problems, each of which, it is said, can be solved by more technology. 5. A. A. Bartlett, "Reflections on Sustainability," Population & Environment, Vol. 16, No. 1, September 1994. Renewable Resources Journal, Vol. 15, No. 4, Winter 1997-98, Pgs. 6-23
Re: Hoffert et al. 24 April 2003
Gerald E. Marsh, Reactor physicists, retired Argonne National Laboratory, George S. Stanford Respond to this E-Letter: Re: Re: Hoffert et al.	In their discussion of advanced energy technologies, Hoffert et al. state that “The main problem with fission for climate stabilization is fuel. Current estimates of [uranium] in proven reserves and (ultimately recoverable) resources are 3.4 and 17 million metric tons, respectively. This represents 60 to 300 TW-year of primary energy. At 10 TW, this would only last 6 to 30 years--hardly a basis for energy policy.” (1). That is misleading, by more than two orders of magnitude. The authors—and the work they reference—assume the absence of any technological advances beyond today’s wasteful thermal reactors. Particularly profligate is the once-through, “throw-away” nuclear fuel cycle now decreed for the United States, which uses much less than a hundredth of the energy potential of the mined uranium. With state-of-the art technology and proliferation-resistant, pyrometallurgical reprocessing, uranium can yield adequate energy for thousands of years (2). More than 2000 TW-years of energy is waiting in what the United States has already mined (3). The authors also say that “Available reactor technology can provide CO2-emission-free electric power, though it poses well-known problems of waste disposal and weapons proliferation.” However, with reprocessing and fast reactors, waste disposal is almost trivial, since the radioactive toxicity of the real waste (the fission products) will be below that of the original ore in less than 500 years (2). As for proliferation, the new technique of nonaqueous pyrometallurgical reprocessing is far more proliferation-resistant than today’s policy of simply storing unreprocessed “spent” fuel (2, 4). Although some engineering details are yet to be worked out, the feasibility of at least one such process--the integrated-cycle advanced liquid metal reactor (ALMR)--has been well demonstrated (5-8). It could constitute an excellent basis for an energy policy. Gerald E. Marsh George S. Stanford Reactor physicists, retired Argonne National Laboratory Argonne, Illinois 60439 References 1. M. I. Hoffert et al., Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet, Science 298, 981 (1 November 2002). 2. Yoon I. Chang, “Advanced Fast Reactor: A Next-Generation Nuclear Energy Concept.” Forum on Physics and Society, April 2002. Available on line at http://www.aps.org/units/fps/apr02/index.html. 3. C. E. Boardman, private communication. See also C. E. Boardman, C. E. Walter, M. L. Thompson, C. S. Ehrman, "The Separations Technology and Transmutation Systems (STATS) Report: Implications for Nuclear Power Growth and Energy Sufficiency." http://www.project21.org/NPA396.pdf. 4. W. H. Hannum, D. C. Wade, G. S. Stanford, “Self-Protection in Dry Recycle Technologies.” Global-95, Versailles, France, September 11-14, 1995. 5. C. E. Boardman, A. Fanning, D. Carroll, A. Dubberley, M. Hui, “A Description of the S-PRISM Plant,” Proceedings of the 8th International Conference on Nuclear Engineering (ICONE-8), Baltimore, MD USA, 1999. 6. C. S. Ehrman, C. E. Boardman, “Integrating ALWR and ALMR Fuel Cycles.” Proceedings of the 4th International Conference on Nuclear Engineering (ICONE-4), New Orleans, USA, 1997. 7. C. E. Boardman, M. Hui, D.G. Carroll, A. E. Dubberly, “Economic Assessment of S-Prism, Including Development and Generating Costs.” Proceedings of the 9th International Conference on Nuclear Engineering (ICONE-9), Nice, France, 2001. 8. W. H. Hannum, Ed., “The Technology of the Integral Fast Reactor and Its Associated Fuel Cycle.” Progress in Nuclear Energy, Vol. 31, No.1/2 (1997) (special issue).
Strategies for dealing with global warming 24 April 2003
Ned Ford Cincinnati, Ohio Respond to this E-Letter: Re: Strategies for dealing with global warming	The excellent article by Hoffert et. al. (Vol. 298 P. 981) has the unfortunate effect of misrepresenting the potential for near-term reductions in CO2 emission. Although energy efficiency is discussed in principle, the article inappropriately minimizes its immediate potential. DOE's "Clean Energy Future" report (http://www.ornl.gov/ORNL/Energy_Eff/CEF.htm) identifies the potential for eliminating over a third of all U.S. energy consumption for less money than we presently spend on energy, using only existing technology. This particular study assumes a much lower total potential than others, but it is among the most comprehensive, and its primary shortcoming is an arbitrary assumption that the only way to accelerate the adoption of these technologies is an inefficient carbon tax. http://www.cool-companies.org is one of a number of very good resources on efficiency, which I identify here because its excellent reference section includes most of the other important organizations and studies. Efficiency's underappreciation may be due in part to the many synergistic effects--efficient lighting reduces air conditioning costs, end-use efficiency reduces transmission loss and reserve margin requirements, vehicle efficiency reduces oil refining emissions, building efficiency reduces natural gas line loss and transmission energy costs-- which complicates comparing a group of strategies that save money with the sort of technology Hoffert examines, which cost money. If one is willing to allow a fraction of a cent per KWH in increased cost over the existing internal cost of a shovel full of coal into a fully amortized, antiquated power plant, it becomes possible to modernize the entire coalburning fleet, using highly efficient combined heat and power technology, which provides waste as a commodity for industrial processes or district heating and cooling. Together with available end-use efficiency, it becomes feasible to think in terms of eliminating 75% of total carbon-emitting electricity fuel, bringing the remaining emissions into reach of some of the existing renewable generation technologies. 50% reductions in all other fossil fuel sectors are readily demonstrated to be feasible, and while technical potential may never be fully achieved, there is no question that the technology will improve and fall in cost, especially in relation to fossil fuels, over time. While this is a dramatic claim, it is undoubtedly a multidecade project, and as such is not extreme in relation to the rate at which we built the existing system. And one does not have to "allow" that extra fraction of a cent. If human health is to be protected, SO2 and NOx restrictions are likely to raise the cost of the old coal sufficiently. And a lot of other factors may do so anyway. Efficiency won't be as effective with unrestrained population growth or unrestrained economic growth. However, failure to restrain either is likely to result in tremendous price pressure on conventional fuels, which will make efficiency more attractive and slow CO2 emissions growth anyway. The U.S. has had flat CO2 emissions growth or a modest decline since January of 2001. While many will assume this to be a product of the recession, it coincides with the California response to natural gas price surges in the winter of 2000/01, which included installation of efficiency hardware that saved energy equivalent to half of all annual average growth in the U.S. for a single year. Changes in consumption are likely if we apply modest deliberate intent, for example, telecommuting, reducing transport of goods by better direct shipping, more effective use of coherent computer systems to facilitate information management without hard copy, and much more. Buildings can eliminate nearly all energy consumption cost-effectively when sophisticated engineering is applied skillfully. Sound voluntary family planning programs can do much to reduce the high end of the range of projected energy needs by the end of this century. Most important, whatever the future holds, our options are far broader, and our likely requirements for energy resources that do not exist today are smaller and come later, if we make a serious effort to understand, identify, and acquire the existing money-saving efficiency potential today. We clearly have several decades of substantial work to do here and can easily outpace population growth and growth in standards of living if we undertake this as if the future carrying capacity of the planet depends on it. To underscore the importance of starting with efficiency first, an all-out effort to capture the savings identified in the DOE report in the electric sector for an arbitrary 20 years would result in total U.S. energy costs in the 20th year being 84% of the first year, assuming an annual cost of 5% of the price of electricity for the programs. Using the same assumptions, and a similar program cost to build new power plants at the average price of natural gas combined cycle, and assuming natural gas prices that are half of today's, the 20th year's total electric costs would be 150% of today's. The difference is fuel, financing, administration, distribution, and utility revenues. CO2 emissions would be somewhat lower than 84% of today's, because less efficient resources would be shut first, but it is hard to be specific with a simplified analysis like this. That 66% of today's electric costs that can be saved would go a very long way to paying for the sort of programs Hoffert et al. advocate. Ned Ford
The competitiveness of renewable energy 24 April 2003
Marco Verweij Max Planck Project Group on Common Goods Respond to this E-Letter: Re: The competitiveness of renewable energy	In their article “Advanced Technology Paths to Global Climate Stability” (1 Nov., p. 982), Hoffert et al. argue that energy sources “that can produce 100 to 300% of present world power consumption without greenhouse emissions do not exist operationally or as pilot plants.” They also chide the Intergovernmental Panel on Climate Change for its “misperceptions of technological readiness.” Hence the authors conclude that intensive research and development constitutes the only path out of this dire predicament. When it comes to renewable energy, the conclusions reached by Hoffert et al. seem overly pessimistic. The production costs of almost all sources of renewable energy have declined significantly during the last two decades, whereas the production costs of coal, oil, and gas have remained stagnant. Experts from a variety of independent organizations--including the U.S. Department of Energy, International Energy Agency, and U.C. Berkeley’s Renewable and Appropriate Energy Laboratory--predict that it is quite feasible to make most forms of renewable energy cheaper than fossil energy within the next ten to fifteen years (1). Thus far, the increasing competitiveness of wind energy has been most conspicuous. Wind has already become a cheaper source of electricity than nuclear energy or coal. Its production costs have been reduced six-fold over the last twenty years, making wind energy almost as cheap as gas. This is not to argue that it would be easy to stimulate the competitiveness of renewable energy. Besides increased research and development, this would require consumers to get informed about new products; enterprises to undertake risky investments; governments at all levels to adapt infrastructure, change tax systems, and provide financial incentives; universities to update curricula; engineers and architects to familiarize themselves with new processes and materials; NGOs to remain vigilant; grid operators to find solutions to the problems caused by the intermittency of some renewables; and international organizations to assist developing countries in acquiring clean technology. All this while many energy companies are tied down by their investments in coal, oil, and gas. However, Hoffert et al. posit that carbon-free technologies do not exist even at the pilot-plant level. Such deep pessimism is not only unwarranted, but also unhelpful as it might discourage governments, enterprises, and NGOs from starting to undertake the myriad of efforts that could make renewable energy competitive (2). This would be regrettable as one of the main motors driving down the costs of emerging technologies is increased production, through enabling economies of scale and further slides down the learning curve. Marco Verweij Max Planck Project Group on Common Goods Poppelsdorfer Allee 45 53115 Bonn Germany References 1. See http://www.eren.doe.gov/power/choices.html, http://www.eren.doe.gov/state_energy/technologies.cfm, http://socrates.berkeley.edu/%7Edkammen/er120/ER120-L1.pdf, and International Energy Agency, “Experience Curves for Energy Technology Policy”, OECD/IEA, Paris, 2000. 2. Reuters Press Agency, “Scientists Say Fossil Fuel Alternatives Lacking”, 31 October 2002.
High-Temperature Solar-Thermal, a readily available solution 27 November 2002
Taw Benderly, CEO-Chief Technology Officer Integrated Energy Technologies, Inc. Respond to this E-Letter: Re: High-Temperature Solar-Thermal, a readily available solution	Why haven't this extraordinary team of scientists and engineers mentioned readily available, fully-tested, DOE lab certified, solar-thermal technologies. These technologies include fixed parabolic troughs with tracking-thermal tubes that can produce electricity by powering Rankin Cycle engines with thermal transfer fluids heated to 750 degrees F (see Kramer Junction, CA/Gilbert Cohen/Luz/Duke Solar), and Dr. Roland Winston's fixed, evacuated tube arrays with non-imaging optics, that can deliver a glycol/water solution heated from 350 to 400 degrees F to any thermally process that can utilize this heat. This can immediately shift substantial loads in tens of thousands Megawatts from many major high- demand electrically powered functions, to include single and double effect absorption chillers for space and process cooling. Both of these solar-thermal array technologies have been tested and certified by Sandia National Laboratories and are in limited commercial use. The term solar-thermal has been emphasized so that it would not be confused with the far less efficient photovoltaics that seem to dominate DOE and public thought when seeking solar-based energy solutions. The barriers to large-scale solar-thermal adaptation have included the A & E profession's natural resistance to "learning something new," non-owner occupied developers reducing first costs at the expense of operating costs, and electric utilities not presently motivated by a locally imposed portfolio standard. The delta between the technology's present and future first costs is directly related to levels of market penetration. These higher first costs will be dramatically lowered with volume production for these types of solar-thermal arrays, presently available from Duke Solar http://www.dukesolar.com At a recent DOE sponsered Concentrated Solar Power roundtable discussion I attended in Las Vegas, the statistics were presented that projected 6 cent power from a 1000 Megawatt SOLAR-THERMAL plant in the southwest, utilizing the newest generation of fixed parabolic troughs with tracking targets presently available. I participated in an even more striking discussion at a recent Oak Ridge National Laboratory/University of Nevada Las Vegas/NTS Development Corporation sponsored Las Vegas roundtable discussion on CHP. It initially focused on the microturbine/absorption chiller marriage. It was not suprising that the discussion ultimately dwelled on the enormous potential for the utilization of the 350 to 400 degree F solar-thermal arrays for shifting major electrical-powered cooling loads from the grid to thermally fired absorption chiller systems. Each 1000 tons thus shifted is one less Megawatt that must be fossil fuel fired. It is interesting to contemplate what the integration of renewable thermal technologies could mean to global warming. A natural coupling would be the thermal partnering of solar-thermal with biofuels derived by the esterification process from vegetable oils and animal fats. This day/night partnered use of solar-thermal and biofuels can effectively reduce total emissions up to 85%. Depressed agricultural sectors worldwide would benefit from this value-added partnered approach. The major oil companies and electric utilities should be actively involved in this renewable-based thermal partnering. Rather than viewing such an effort as treatening to their present core business, such participation could ensure them continuing profits from the successful marketing of renewable energy sources. It might mitigate much of the present industry resistance to adaptaion of renewable thermal energy technologies. Since you acknowledge that energy is the issue, this could be a small but achievable incremental step toward the reduction of the carbon dioxide-induced component of climate change.
Life-cycle Assessment of Energy Technologies 27 November 2002
sergio a pacca, phd student Energy and Resources Group - UC Berkeley Respond to this E-Letter: Re: Life-cycle Assessment of Energy Technologies	The article highlights several technologies that could lead the world to a sustainable development path; however, no discussion of global warming mitigation is complete without mentioning the life-cycle assessment (LCA) of the proposed technologies. Because greenhouse gases are emitted during the various phases of an energy generation process (manufacturing, construction, operation, and end of life), it is fundamental to take into account the cumulative effect when alternatives are compared. Moreover, because the location of emission sources over the life cycle of a power plant does not affect global climate change, LCA seems to be the perfect tool to guide decision makers toward the best available energy option. In this case, the timing of greenhouse gas releases is much more of concern than the spatial distribution, and models looking at the persistence of greenhouse gases in the atmosphere and their potential future impacts could be coupled to the LCA framework. The literature on energy LCAs could provide a significant contribution to the debate. Sergio Pacca Energy and Resources Group, UC Berkeley Reference S. Pacca, A. Horvath, Environ. Sci. Technol. 36, 3194-3200 (2002).
Breeder reactors should be considered also 27 November 2002
Ira Charak, Engineer Argonne National; Laboratory Respond to this E-Letter: Re: Breeder reactors should be considered also	Hoffert et al. dismiss the nuclear fission option as an answer to the world's long-term energy needs on the basis that there will not be enough uranium to fuel the number of current generation type of reactors needed to make a significant impact. Completely missing from their analysis is the potential role of breeder reactors, in which electricity is generated simultaneously with the production of more nuclear fuel than is consumed through the utilization of the 99+ percent of the uranium, U-238, that is not directly usable in the current and proposed thermal reactor systems. Such a reactor can extend the available uranium resources by almost two orders of magnitude. Taking account of the breeder reactor would have almost certainly demolished Hoffert et al.'s argument against nuclear fission.
Ignores conservation 27 November 2002
William R. Stewart, systems engineer Respond to this E-Letter: Re: Ignores conservation	A premise of this article is that energy demand will continue to climb, i.e., that people now driving SUV/Pickups will eventually be driving something larger and less efficient. I contend that various scenarios should be examined that identify various technologies that reduce energy demand beyond simple efficiency. For example, there exist today many homes and buildings that produce as much energy as they consume (zero-energy building). Many European countries are creating car-free transit districts, where travel is by foot, bike, or transit. Countries like the United States could drastically cut energy demand by - Focusing new development around existing and future transit stops and making them safe and livable through limited car access - Raising appliance, building, and automotive (CAFE) efficiency standards - Instituting a carbon tax, or a BTU tax on nonrenewable energy sources It's one thing to dream, it's another to face reality, but the goal is to turn the first into the second.