Editing Pieee

'''Special Issue of Proceedings of the IEEE''': "Addressing the intermittency challenge:  Massive energy storage in a sustainable future."

'''Guest Editors: ''' 

* William F. Pickard, Life Fellow IEEE, Washington University, USA, Email: wfp@ese.wustl.edu
* Leon di Marco, FSK Technology, UK, Email: leon.dimarco@btinternet.com
* Derek Abbott, Fellow IEEE, University of Adelaide, Australia, Email: dabbott@eleceng.adelaide.edu.au

==Scope==
The sustainable green energy system of the future is sometimes envisioned as having three parts:  (i) widely distributed generation of electricity from sun, wind, and other; (ii) a low‐loss electrical backbone for moving vast quantities of energy from regions of plenty to regions of scarcity; and (iii) local distribution to smart loads.  This Special Issue will focus on the missing link between (ii) and (iii) – the difficult and often-neglected problem of matching the electrical outputs from intermittent renewable sources such as solar thermal (or solar photovoltaic or tidal or wind, etc.) to a time varying consumer demand which can be modulated only so far. This is known as the ''intermittency challenge''.  A promising resolution to this challenge is the creation of a robust, long‐life, low‐loss grid that delivers, in times of plenty, surplus electrical energy to massive regional storage reservoirs near the end-users. These reservoirs save the energy in any convenient form and back-transform it into grid power during times of local shortage. This Special Issue will discuss selected aspects of the Intermittency Challenge, with a pervasive emphasis on intuitive understanding of the technologies described, on their currently achievable performance and robustness, and on the near-term prospects for their performance improvement.  In particular, chemical storage will focus on the challenges of a solar hydrogen economy and the production, storage, and utilization of hydrogen for off-grid energy requirements such as automotive transport.  Papers on mechanical and thermal storage will focus on the back-conversion of energy stores into electricity for the local grid. 

==Objectives and significance==
The objective of the proposed Special Issue is to review research, development, and commercialization efforts in the areas (A) of massive storage of renewable green energy and (B) its back-conversion to grid electricity.  By “massive” we mean quantities on the order of one gigawatt‐day and up, where 1 GWd = 86.4 TJ.  We shall encourage not only papers of narrow technical focus (however important) but also ones of plentiful tutorial-style content. Given the known issues of cleanliness, safety, and sustainability with both nuclear and fossil fuels, there is a rapidly growing recognition of the importance of green and renewable energy sources.  However, the weak link of the major renewable sources is their intermittency.  The urgency of addressing and resolving this Intermittency Challenge is clear:  fossil fuels are not intermittent, but they are finite; and if their depletion is not to leave our children a world where on-demand energy is only a memory, then the enormous task of developing massive energy storage systems is urgent.  In the United States alone there is 1.1 TW of electric generating capacity, of which less than 10% is both renewable and buffered with storage; furthermore, it is hard to see how the gap could be closed with more dams.  

The proposed Special Issue will highlight this urgency; and we intend it to be a landmark resource for future workers in the area.   

==Contributors and paper outlines==

Although the number of contributors and papers is likely to slightly increase or be modified, the following list includes the majority of the contributions in the proposed Special Issue.

===Preface article===
 
====Scanning the issue==== 

The Guest Editors will briefly review what the “intermittency challenge” is and why our energy future depends on overcoming it. It will then briefly contextualize each paper in the Special Issue and point out that the papers have been grouped thematically as follows: (a) Keynote and Policy.  (b) Chemical Storage.  (c) Mechanical Storage.  (d) Thermal Storage.  	
 
===Energy policy===
 
====Energy storage—from characteristics to impact. A US roadmap====
*'''Authors:'''  Avi M. Gopstein (U.S. Department of Energy, USA)
*'''Contact email:'''  Avi.Gopstein@science.doe.gov
*'''Scope:'''   This paper will discuss energy storage at a high level and from the perspective of the physical fundamentals that govern technological performance characteristics of the grid.  It will describe the likely menus of solutions available for such issues as massive storage for load-shifting, storage to provide bridging power, storage to assure grid stability, storage to promote power quality, and storage to make electricity more economic.  Innovative storage technology will pave the way for longer-term integration of new energy technologies of all kinds, including (but not limited to) hydrogen fusion and the many forms of renewable generation.
 
====Generation portfolio planning for systems with large penetrations of intermittent renewables====
*'''Authors''': Elaine K. Hart (Stanford University, USA), Mark Z. Jacobson (Stanford University, USA)
*'''Contact email:''' jacobson@stanford.edu
*'''Scope:''' Minimizing the need for massive energy storage systems on grids with large penetrations of intermittent renewables like wind and solar will require new methods of both system planning and system operation.  At the planning stage, the effects of intermittency can be reduced by using optimization methods and large historical and modeled data sets to develop portfolios that best match the aggregated intermittent resources with the load.  These models can also be used to approximate the capacities of conventional dispatchable generators or large-scale energy storage facilities required to ensure that these low-carbon systems meet appropriate reliability standards.
 
==== How thermal energy storage enhances the economic viability of concentrating solar power====
*Authors: Ramteen Sioshansi (The Ohio State University, USA), Paul Denholm (National Renewable Energy Laboratory, USA), and Seyed Madaeni (The Ohio State University, USA) 
*Contact email: sioshansi.1@osu.edu
*Scope: Concentrating solar power (CSP) is a promising utility-scale solar generation technology. We will survey the value that thermal-energy storage can provide CSP by providing services, including allowing CSP generation to be shifted to higher-value periods, the size of the solar field to be increased relative to that of the powerblock, and the CSP plant to have a higher effective capacity value.
 
====The future of solar thermal farms linked by transnational grids====
*Authors: Stewart Taggart (DESERTEC-Australia)
*Contact email: staggart@desertec-australia.org
*Scope: In this paper, the author(s) will argue Asia's unique geography, factor endowments, economic growth and future energy favor a 'Pan-Asian Energy Infrastructure' patterned after the European DESERTEC Industrial Initiative. The article will focus on Australia's Outback and China's Mongolian solar resources as potential 'anchor tenants' for a region-spanning energy grid stretching from Beijing to the Great Australian Bight. Issues also to be stressed are (a) efficiency of transduction from incident solar watts to shipped transmission-line watts and (b) anticipated transmission losses along megameter links.
 
====The relative abundance of the elements in the periodic table and their impact on global energy policy====
*Authors: Derek Abbott (University of Adelaide, Australia)
*Contact email: dabbott@eleceng.adelaide.edu.au
*Scope: This paper examines the relative abundance of the elements in the earth’s crust. Together with known global annual growth rates in their rate of consumption, we compare their relative extinction times. We then discuss how this information impacts on long-range energy policy in terms of both generation and massive storage.


===Chemical Storage===
 
====Ammonia-based energy storage for concentrating solar power====
*Authors: Keith Lovegrove (Australian National University, Australia), John Pye (Australian National University, Australia), Greg Burgess (Australian National University, Australia), Rebecca Dunn (Australian National University, Australia)
*Contact email: keith.lovegrove@anu.edu.au
*Scope: Concentrating solar power uses mirrors to concentrate solar radiation to a hot focus. One method of storing this energy is based on the reversible dissociation of ammonia. In this storage system, a fixed inventory of ammonia passes alternately between energy-storing (solar dissociation) and energy-releasing (synthesis) reactors. Coupled with a Rankine power cycle, the energy-releasing reaction can be used to produce dispatchable power for the grid. At 20 MPa and 20oC, the enthalpy of reaction is 66.8 kJ/mol. The main advantage of an ammonia-based storage system is that energy is stored in chemical bonds, rather than heat. Therefore energy can be transported around a gigawatt-sized solar field with no heat losses from steam or oil lines. In addition, an ammonia-based storage system can leverage the substantial industrial experience of the ammonia industry.
 
====The importance of the seasonal variation in demand and supply in a renewable energy system====
*Authors: Alvin O. Converse (Dartmouth College, USA)
*Contact email: alvin.o.converse@dartmouth.edu
*Scope: As energy systems become more completely dependent on renewable sources, seasonal variations in supply and demand will require massive seasonal energy stores and/or long distance energy transportation systems.  This will favor the use of hydrogen over electricity because of the lower cost of gas storage and pipeline transport compared to batteries and transmission lines.
 
====Hydrogen generation technologies from water electrolysis: Present and future of high-pressure electrolyzers====
*Authors: Alfredo Ursúa (University of Navarra, Spain), Pablo Sanchis (University of Navarra, Spain)
*Contact email: pablo.sanchis@unavarra.es
*Scope: This paper describes the water electrolysis technology to produce clean hydrogen in a renewable energy-based grid. First, basic concepts concerning thermodynamics and electrochemistry of water electrolysis, with special attention to the influence of the temperature and pressure on the process, are explained both from a theoretical and practical point of view. Then, the two main types of electrolyzers, alkaline and PEM, are described and compared. After that, the technology used in atmospheric and pressurized electrolyzers is exposed and evaluated, and their strengths, weaknesses and trends for the coming years are analyzed. Commercial units of the different technologies offered by manufacturers are included in the analysis.
 
====The hydrogen-fueled internal combustion engine====
*Authors:  Sebastian Verhelst (Ghent University, Belgium)
*Contact email: sebastian.verhelst@ugent.be
*Scope: Use of hydrogen as an energy carrier for transport applications is mostly associated with fuel cells. However, an internal combustion engine converted to or designed for hydrogen, can attain high power output, high efficiency and ultra low emissions, at a cost currently far below that of fuel cells. More importantly, because of the possibility of bi-fuel operation, the hydrogen engine can act as an accelerator for building up a hydrogen infrastructure. This article presents the current state and future prospects for hydrogen engines.
 
====Energy storage and supply from sustainable organic fuel made with CO<sub>2</sub> and water in a solar powered process====
*Authors: R. Pearson (Lotus Engineering, UK), P. Edwards (University of Oxford, UK), M. D. Elsaman (PARC, USA), K. A. Littau (PARC, USA), Leon di Marco (FSK Tech., UK)          
*Contact email: leon.dimarco@btinternet.com
*Scope: Massive long-term energy storage using CSP generated sustainable organic fuels, which can be used for conventionally powered transportation, as part of a large-scale atmospheric CO2 reduction strategy.
 
===Mechanical storage===
 
====The present state and future prospects for advanced adiabatic compressed air energy storage====
*Authors: Giuseppe Grazzini (University of Florence, Italy), Adriano Milazzo (University of Florence, Italy) 
*Contact email: adriano.milazzo@unifi.it
*Scope: Adiabatic compressed air energy storage represents a valuable and environmental friendly option for massive energy storage. Some examples in this field refer to underground storage at medium pressure level. In view of a widespread utilization, independent from the availability of underground storage volumes, an artificial reservoir is required. This prompts for rather high air pressure within the storage, which in turn requires carefully optimized recovery of the thermal energy released in the compression phase. Starting from a thermodynamic tutorial of the relevant design parameters and their influence on the system efficiency, we propose a comprehensive set of criteria for the design of the system; with particular attention on heat transfer devices. A possible application within a wind energy plant is analyzed. 
 
====The history, present state, and future prospects of underground pumped hydro====
*Authors:  William F. Pickard (Washington University, USA)
*Contact email: wfp@ese.wustl.edu
*Scope: To stabilize the future national or regional electricity grid supplied by sustainable but intermittent sources will require multiple gigawatt-day-sized energy storage modules.  Devices of such functionality do not at present exist but can be created using extant technology.  This paper discusses one possible realization based upon the familiar pumped hydro facility, only now with the lower reservoir directly under the upper and many hundred meters below ground surface. 
 
====Geotechnical issues in the creation of underground reservoirs for massive energy storage====
*Authors: Nasim Uddin (University of Alabama at Birmingham, USA)
*Contact email: nuddin@uab.edu
*Scope: Pumped storage is currently an economically viable alternative to the conventional above ground type of facility, and is made increasingly attractive by consideration of the reduced environmental impact, which the underground concept make possible. This paper is intended to provide an introduction to the engineering challenges of underground pumped storage.
 
===Thermal storage===

====Concept and development of a pumped heat electricity storage system====
*Authors: Jonathan Howes (Isentropic Ltd, United Kingdom) 
*Contact email: jonathan.howes@isentropic.co.uk
*Scope: The paper will first address (a) the early conceptualization of a system for heat/work conversion based upon the first Ericsson cycle of 1833 in combination with massive thermal storage in gravel and (b) the development and test of the first prototype. Using these test results, mathematical modeling of the engine/heat pump and thermal stores has yielded improved second and third prototypes. Design of the second prototype and its behavior under test will be discussed.  Extant test results will be employed to extrapolate to the predicted performance of massive utility-scale equipment.
 
====Molten salt power towers—New players in commercial energy storage====
*Authors: Rebecca Dunn (Australian National University, Australia), Matthew Wright (Beyond Zero Emissions, Australia), Patrick Hearps (University of Melbourne, Australia) 
*Contact email: rebecca.dunn@anu.edu.au
*Scope: Concentrating solar power (CSP) can both generate and store renewable energy all in the one plant. Curved mirrors concentrate the sun’s energy to be stored as heat, for example in a mixture of molten salt, or in a chemical reaction. When required, this stored energy can be used to produce steam and drive a turbine. In this way, variable renewable energy sources such as wind and photovoltaics can be dispatched to the grid first, and the “back-up” provided by concentrating solar plants with storage.  CSP trough plants with 7.5 hours of molten salt storage have been operating in Spain since 2008. But there is a new player in the CSP storage market—the solar power tower with molten salt storage. Towers can achieve higher temperatures than troughs—565<sup>o</sup>C as opposed to 380<sup>o</sup>C—and hence store more megawatt-hours of energy in the same amount of salt.  In March 2011, Torresol Energy of Spain will commission the 17 MWe Gemasolar power tower with 15h of molten salt storage. At the same time, US firm SolarReserve will be constructing a 50 MWe plant in Spain, and a 100 MWe plant in Nevada—both with around 15h of molten salt storage. Near-term advances include using oxygen blankets to allow higher storage temperatures up to 650<sup>o</sup>C, and the use of quartz fillers and thermocline tanks to reduce the quantity of salt required.

====Concentrating solar thermal with storage using calcium hydride for low cost dispatchable energy====
*Authors:  David Harries (EMCSolar, Australia), Wayne Bliesner (EMCSolar, Australia), John Davidson (EMCSolar, Australia)
*Contact email: john.davidson@emcsolar.com.au
*Scope: The energy storage technology being developed is a thermochemical energy heat storage system that uses solar radiation to drive highly endothermic chemical dissociation reactions.  The heat is recovered in a highly exothermic reformation reaction. The system has a significantly higher energy storage density than do conventional solar energy storage systems. It also operates at high temperature, which increase the thermodynamic and solar energy to electricity system efficiency. The thermochemical energy storage system being developed in this project is based on the dissociation of calcium hydride (CaH<sub>2</sub>).  As calcium hydride is heated it absorbs solar energy to drive the endothermic dissociation reaction at around 1000<sup>o</sup>C. Operating at this high temperature increases the reaction rates and the overall system efficiency.  As hydrogen gas is released, it is removed and stored in low temperature hydride storage vessels, a low cost bulk hydrogen storage technique, the calcium remains in the reactor vessel. When solar radiation levels fall, or the amount of electricity required increases (peak electricity demand periods), hydrogen is returned to reaction vessel and an exothermic reformation (fusion) reaction releases heat. All of the materials used, including calcium, hydrogen, sodium and aluminum are available in quantities that make it possible for large numbers (Gigawatts) of the solar energy storage plant to be built over the next 15 years.

==== Review of massive solar thermal storage techniques and the associated heat transfer technologies that undergird them====
*Authors: Luisa F. Cabeza (Universitat de Lleida, Spain), Cristian Solé (Universitat de Lleida, Spain), Albert Castell (Universitat de Lleida, Spain), Eduard Oró (Universitat de Lleida, Spain), Antoni Gil (Universitat de Lleida, Spain).
*Contact email: lcabeza@diei.udl.cat
*Scope: Thermal energy storage is a key component of solar power plants if dispatchability is required. On the other hand, although different systems and many materials are available, only a few plants in the world have tested thermal energy storage systems. Here, all materials considered in literature and/or used in real plants are tested, the different systems are described and analyzed, and real experiences are compiled. The associated heat transfer technologies to support and improve these systems are described and analyzed.
 
====High temperature solid media thermal energy storage for solar thermal power plants====
*Authors: Doerte Laing (German Aerospace Center, Germany)
*Contact email: Doerte.Laing@dlr.de
*Scope: The paper will give an overview of the development of high temperature thermal energy storage using concrete as a storage medium. It will summarize the material characteristics, construction and long term testing of a 20 m³ test module and performance evaluation for a full year simulation, integrated in a parabolic trough power plant.

==Guest Editorial Biographies==
'''William F. Pickard (SM’66–F’89)''' received the Ph.D. degree in applied physics in 1962 from Harvard University, Cambridge, MA. After Postdoctoral experience at Harvard and at the Massachusetts Institute of Technology (MIT), Cambridge, he joined Washington University, Saint Louis, MO, where he is now a Senior Professor of Electrical Engineering. He is the author of more than 140 refereed publications grouped into five fields: (i) High Voltage Engineering, where he specialized in electrohydrodynamic motion of dielectric liquids; (ii) Electrobiology, where he pioneered the use the lanthanum as a calcium channel blocker; (iii) Biological Transport, where he pioneered in the study of stress-induced phloem blockade and also wrote well received reviews first on xylem transport and later on laticifers and secretory ducts;  (iv) Bioeffects of Electromagnetic Energy, where he was the first to observed the rectification of radio waves by cell membranes and where he also designed many novel microwave applicators; and (v) Sustainability and Energy, where he has focussed on mineral sustainability and upon massive energy storage to resolve the intermittency challenge.      

'''Leon di Marco''' received the B.Sc. degree (Hons) in physics and electronics from Manchester University, UK, in 1972 and studied for a Ph.D. degree in solid-state physics at the University of Reading until 1976.  He then joined the GEC Hirst Research Centre, London, U.K., and researched semiconductor processes, obtaining a patent on the novel VIPMOS structure. In 1979, he joined Multitone Electronics in London and, with Plessey Semiconductors, designed the first direct conversion radiopager having on-chip active filters. Between 1982 and 1995 he started two communication companies, and acted as a communications consultant to several international companies. He is now a renewable energy consultant specializing in large-scale solar power and has advised the UK government on smart meters and the prospects for EU wide renewable energy.  He was the lead organizer for a conference on the EU Mediterranean Solar Plan held in London in 2009 and is also a lead organizer for a two day Royal Society discussion meeting on Solar Power to be held in 2011.

'''Derek Abbott (M’85-SM’99-F’05)''' was born on May 3, 1960, in South Kensington, London, U.K. He received the B.Sc. degree (Hons) in physics from Loughborough University of Technology, U.K., in 1982 and the Ph.D. degree in electrical and electronic engineering from the University of Adelaide, Australia, in 1995, under Kamran Eshraghian and Bruce R. Davis. From 1978 to 1986, he worked at the GEC Hirst Research Centre, London, U.K., in the areas of semiconductors and optoelectronics. On migration to Australia, he worked for Austek Microsystems, Technology Park, South Australia, in 1986. Since 1987, he has been with the University of Adelaide, where he is currently a full Professor in the School of Electrical and Electronic Engineering. He holds over 350 publications/patents and has been an invited speaker at over 80 institutions, including Princeton, NJ; MIT, MA; Santa Fe Institute, NM; Los Alamos National Laboratories, NM; Cambridge, U.K.; and EPFL, Lausanne, Switzerland. He coauthored the book Stochastic Resonance, published by Cambridge University Press, and co-edited the book Quantum Aspects of Life, published by Imperial College Press. His interests are in the area of complex systems and multidisciplinary applications of physics and engineering. In terms of energy policy, his interest lies in a complex systems approach to analyzing global energy issues, with a particular emphasis on sustainability of the required resources. Prof. Abbott is a Fellow of the Institute of Physics (IOP), with honorary life membership. He won the GEC Bursary (1977), the Stephen Cole the Elder Prize (1998), SPIE Scholarship Award for Optical Engineering and Science (2003), the South Australian Tall Poppy Award for Science (2004) and the Premier’s SA Great Award in Science and Technology for outstanding contributions to South Australia (2004). He has served as an editor and/or guest editor for a number of journals including IEEE Journal of Solid-State Circuits, Chaos (AIP), Smart Structures and Materials (IOP), Journal of Optics B (IOP), Microelectronics Journal (Elsevier), Fluctuation Noise Letters (World Scientific), and is currently on the Editorial Boards of Proceedings of IEEE and IEEE Photonics. He has appeared on national and international television and radio and has also received scientific reportage in New Scientist, The Sciences, Scientific American, Nature, The New York Times, and Sciences et