The heat exchanger is important in practical thermal processes, especially those of (i) the molten-salt storage schemes, (ii) compressed air energy storage schemes and (iii) other load-shifting thermal storage presumed to undergird a Smart Grid. Such devices, although central to the utilization of energy from sustainable (but intermittent) renewable sources, will be unfamiliar to many scientists, who nevertheless need a working knowledge of them. This tutorial paper provides a largely self-contained conceptual introduction for such persons. It begins by modelling a novel quantized exchanger,1 impractical as a device, but useful for comprehending the underlying thermophysics. It then reviews the one-dimensional steady-state idealization which demonstrates that effectiveness of heat transfer increases monotonically with (device length)/(device throughput). Next, it presents a two-dimensional steady-state idealization for plug flow and from it derives a novel formula for effectiveness of transfer; this formula is then shown to agree well with a finite-difference time-domain solution of the two-dimensional idealization under Hagen–Poiseuille flow. These results are consistent with a conclusion that effectiveness of heat exchange can approach unity, but may involve unwelcome trade-offs among device cost, size and throughput.

Two conceptually and computationally simple techniques (one optimistic, the other pessimistic) are introduced to estimate the energy payback time of a photovoltaic array. Both yield values of the Energy Returned On energy Invested (EROI) in excess of approximately 5. Therefore solar photovoltaic electricity appears to be a stably sustainable source of renewable energy.

Presently, America's average electrical power consumption is 1.3 kW/p; in the world as a whole, it is ~0.33 kW/p. If, for 2050, a world goal of 1 kW/p is adopted, this implies an average electric power draw of 1 GW for each population cohort of 1 000 000 residents; and the Earth will have ~10 000 such cohorts. Multi-hour outages are already common; demand peaks daily; and renewable generation is intermittent. Hence, as a hedge against rare supply failures, each cohort would profit from local backup storage of electricity/energy in the order of 1-2 GWd. For comparison, the biggest electrochemical storage scheme yet seriously proposed will contain ~240 MWh, while most of the largest pumped hydro storage reservoirs are <;50 GWh. In approximately 50 years, when fossil fuels have become scarce, we should already have constructed this bulk storage. This review argues that the principal contenders for the storage of electricity in bulk are: 1) electrochemical storage in flow batteries; 2) chemical storage in agents, such as ammonia, hydrogen, methanol, or light hydrocarbons; 3) compressed air energy storage; and 4) underground pumped hydro. Finally, it will argue that not one of these four contenders has yet been built, tested, and perfected, while virtually none of the needed storage capacity exists today.

In this paper, prima facie evidence is presented to demonstrate that, by the close of this century: 1) the world will be approaching exhaustion of its supply of recoverable fossil fuel; 2) the energy shortages engendered thereby can reliably be avoided only if immediate massive steps are taken to actualize the development and manufacture of important, as yet unproven, components of a global smart energy system; and 3) the world over, there is little evidence (as measured by funding committed for development and demonstration) that the key governments are seriously concerned.

Explores the open question of whether mankind, having run through its dowry of fossil fuels, will be able to maintain its advanced global society. Given our present knowledge base, no definite answer can be reached. It seems only common sense to believe that, to survive, a band of hunter gatherers must arrange its activities to acquire at least as much energy as it expends both directly in hunting and gathering and indirectly in essential ancillary activities, such as basal metabolism, which support the hunting and gathering.

The phloem provides a network of sieve tubes for long-distance translocation of photosynthates. For over a century, structural proteins in sieve tubes have presented a conundrum since they presumably increase the hydraulic resistance of the tubes while no potential function other than sieve tube or wound sealing in the case of injury has been suggested. Here we summarize and critically evaluate current speculations regarding the roles of these proteins. Our understanding suffers from the suggestive power of images; what looks like a sieve tube plug on micrographs may not actually impede translocation very much. Recent reports of an involvement of SEOR (sieve element occlusion-related) proteins, a class of P-proteins, in the sealing of injured sieve tubes are inconclusive; various lines of evidence suggest that, in neither intact nor injured plants, are SEORs determinative of translocation stoppage. Similarly, the popular notion that P-proteins serve in the defence against phloem sap-feeding insects is unsupported by empirical facts; it is conceivable that in functional sieve tubes, aphids actually could benefit from inducing a plug. The idea that rising cytosolic Ca(2+) generally triggers sieve tube blockage by P-proteins appears widely accepted, despite lacking experimental support. Even in forisomes, P-protein assemblages restricted to one single plant family and the only Ca(2+)-responsive P-proteins known, the available evidence does not unequivocally suggest that plug formation is the cause rather than a consequence of translocation stoppage. We conclude that the physiological roles of structural P-proteins remain elusive, and that in vivo studies of their dynamics in continuous sieve tube networks combined with flow velocity measurements will be required to (hopefully) resolve this scientific roadblock.

In a post-carbon energy economy, just as during the Age of Fossil Fuel, the locations where men take control of energy resources (e.g., the coal-pit, the mill wheel, the terminals of a concentrating solar power generator) will often be far removed from the locations where they wish to expend those resources. Therefore, the captured energy resource, once isolated, must somehow be translated from its point of origin to its point of use; and in doing so, its owner must expend energy. In this paper it is argued that, in a sustainably fueled future: (i) renewable energy in its initially transportable form will be overwhelmingly electrical; (ii) energy frugality will dictate long-distance transport of energy as electricity; (iii) intermediate-term (less than a fortnight) storage of energy will be via compressed air energy storage or pumped hydro- or electrochemical batteries, which can not be comparatively evaluated without extensive expensive development and demonstration; and (iv) massive conversion of electrical energy into synthetic fuels will be restricted to selected transportation applications.

Renewable energy is abundant, but not necessarily near the urban centers where it will be used. Therefore, it must be transported; and this transport entails a systemic energy penalty. In this paper simple qualitative calculations are introduced to show (i) that high-voltage direct-current (HVDC) power lines for megameter and greater distances are unlikely to achieve power capacities much beyond 2 GW, although they can be paralleled; (ii) that most sources and sinks of electric power are rather less than 10,000 km apart; (iii) that such long lines can be constructed to have transmission losses <= 2%; and (iv) that lines of such low loss in fact meet minimal standards of intergenerational equity. (C) 2013 Elsevier Ltd. All rights reserved.

The Intermittency Challenge and the approaching need for massive storage of rapidly dispatchable energy has led the concept of the National Battery, a unified facility that holds the aggregated outputs from an array of intrinsically episodic renewable sources, releasing energy as demand requires. In this contribution, the original demonstration of Murphy that lead-acid batteries are inappropriate is first reviewed and then extended to show that no commercially available battery technology is at present appropriate. However, prospectively, underground pumped hydro storage could suffice, and at a lesser cost than suitable batteries.

Present day electricity is a bargain. It frees mankind from a host of dirty, debilitating occupations—epitomized by the now endangered occupation of legger. Correctly applied, electricity would make a most excellent paramount energy carrier for a post-carbon world. It is, however, only an energy carrier and not a source of energy, the preeminent source for its generation being bargain-priced fossil carbon. But when, in less than a century, that is gone, electricity is a good bet to cost markedly more while being still a bargain. This paper once again shows that mankind's energy needs can be met by (i) renewable solar generation of electricity buffered by (ii) massive electricity storage and (iii) a robust distribution grid. The time available for making this switch from fossil carbon to solar is at best a century and possibly as little as fifty years.

If our industrial civilization is to be sustained, it must find renewable sources of energy to replace its finite and rapidly shrinking reserves of fossil carbon. Moreover, these renewables, even if intermittent, must somehow be rendered reliable and dispatchable, most probably by developing super-massive storage facilities for energy. Historically this has meant pumped hydroelectric storage, a technology that is well developed, reliable, comparatively inexpensive, and seriously limited by a shortage of suitable reservoir sites. The obvious solution is to excavate an underground reservoir many hundreds of meters below surface level and to exchange water between it and a surface reservoir created immediately above it and diked using spoil from the excavation. This variant of hydro storage is called underground pumped hydro (UPH) and is described in detail in this review, where it will be shown that: 1) the cost per GW of pumping station could be reasonable and on the order of 1 G$US while 2) the cost of storage capacity could be less than 100 $US per kWh and in keeping with the U.S. Department of Energy's cost goals.

The pressure-driven mass-flow hypothesis of phloem translocation associated with Ernst Münch has become hegemonic and has been mathematically modelled in many, many different fashions - but not, apparently, in one chosen so that it gives simple algebraic predictions of (i) the speed of translocation; (ii) the saccharide concentration at the source; and (iii) the pressure offset due to translocation. To overcome this deficit, the problem was drastically simplified by assuming that: (i) radial variations could be neglected; (ii) osmotic water uptake was restricted to sink and source regions of negligible thickness; (iii) there was a constant rate of saccharide loading at the source; and (iv) the sink strength was sufficient to lower the photosynthate concentration at the extreme distal end of the sieve tube to levels at which it becomes unimportant. The resulting system of quadratic algebraic equations was then solved for the translocation speed, which was shown to vary as the square-root of the loading rate. Also found were the offset of the intra-tube hydrostatic pressure and the sap saccharide concentration at the source, which, likewise, vary as the square-root of the loading rate.

This Special Issue focuses mainly on massive energy storage systems, but also includes a vision for small to medium sized storage and a discussion of the driving forces.

It is argued: (i) that the harvesting of terrestrial solar radiation to perform useful work is at least an order of magnitude more efficient when carried out by solar-thermal or solar-photovoltaic processes than when carried out by way of biomass conversion and (ii) that, therefore, biomass energy is unlikely to compete successfully with inanimately harvested solar energy—except of course in restricted niche applications.

It is pointed out that the apparent decision of the United States to end development of the Yucca Flat, Nevada repository for permanent disposal of radioactive waste may inadvertently place it at variance with the disposal principles of the International Atomic Energy Agency (IAEA) which caution nuclear nations that “The burden on future generations shall be minimized by safely disposing of high level radioactive wastes at an appropriate time, technical, social and economic factors being taken into account.” It is then shown that the IAEA's ten technical criteria for underground disposal can seemingly be met by storing vitrified waste a kilometer underground in the crystalline basement rock of a mid-continent shield, where: (a) it should be invulnerable to redistribution by incompetence, natural disaster, or terrorism and (b) there is no obvious pathway for leakage into the biosphere. Finally, a method is proposed by which the storage impasse may be broken.

Subcutaneous fat necrosis of the newborn (SCFN) is a rare self-limiting panniculitis. It is thought to be associated with perinatal hypoxia and therapeutic hypothermia. It is characterised by firm subcutaneous nodules on the back, shoulder and arms. We present a rare facial presentation of SCFN in a 4-week-old infant with no history of therapeutic cooling. She presented with a discrete right cheek mass with no overlying skin changes. We present the diagnostic challenge and undertake a review of the literature. SCFN is an important differential diagnosis in a neonate with subcutaneous facial lesions. SCFN can be complicated by metabolic derangements including hypercalcaemia.

It is shown that, in a sustainable energy future, energy for the electricity grid will probably be derived largely from the renewable sources of wind and solar radiation. Because both are intermittent, any infinite busbar grid supplying a metropolitan area must necessarily be buffered from these intermittencies by massive energy storage on the gigawatt-day level. It is then demonstrated that, under presently foreseeable scientific capabilities, only underground pumped hydro and advanced adiabatic compressed air energy storage appear capable of meeting anticipated technological and economic constraints. Neither has ever been constructed and tested; but even so it is predicted that underground pumped hydro ultimately will prove to be superior.

This article explores whether large-scale compressed air energy storage can be justified technically and economically in an era of sustainable energy. In particular, we present an integrated energy and exergy analysis of an idealized case of an advanced-adiabatic compressed air energy storage system and estimate its cycle efficiency. Based on our results, advanced-adiabatic compressed air energy storage (AA-CAES) seems to be technically feasible with a cycle efficiency of roughly 50% or better. However, our calculation shows that AA-CAES may not be as economically attractive as underground pumped hydro storage.

In the 80 years since its introduction by Münch, the pressure-driven mass-flow model of phloem translocation has become hegemonic, and has been mathematically modelled in many different fashions but not, to our knowledge, by one that incorporated the equations of hydrodynamics with those of osmosis and slice-source and slice-sink boundary conditions to yield a system that admits of an analytical steady-state solution for the sap velocity in a single sieve tube. To overcome this situation, we drastically simplified the problem by: (i) justifying a low Peclet number idealisation in which transverse variations could be neglected; (ii) justifying a low viscosity idealisation in which axial pressure drops could be neglected; and (iii) assuming a sink of strength sufficient to lower the photosynthate concentration at the extreme distal end of the sieve tube to levels at which it became unimportant. The resulting ordinary nonlinear second-order differential equation in sap velocity and axial position was of a generalised Liénard form with a single forcing parameter; and this is reason enough for the lack of a known analytic solution. However, since the forcing parameter was very large, it was possible to deduce approximate second-order solutions for behavior in the source, sink and transport regions: the sap velocity is zero at the slice-source, climbs with exponential rapidity to a plateau, maintains this plateau over most of the sieve tube, and then drops with exponential rapidity to zero at the slice-sink.

Forisomes are ATP-independent, Ca(2+)-driven contractile protein bodies acting as reversible valves in the phloem of plants of the legume family. Forisome contraction is anisotropic, as shrinkage in length is associated with radial expansion and vice versa. To test the hypothesis that changes in length and width are causally related, we monitored Ca(2+)- and pH-dependent deformations in the exceptionally large forisomes of Canavalia gladiata by high-speed photography, and computed time-courses of derived geometric parameters (including volume and surface area). Soybean forisomes, which in the resting state resemble those of Canavalia geometrically but have less than 2% of the volume, were also studied to identify size effects. Calcium induced sixfold volume increases in forisomes of both species; in soybean, responses were completed in 0.15 s, compared to about 0.5 s required for a rapid response in Canavalia followed by slow swelling for several minutes. This size-dependent behavior supports the idea that forisome contractility might rest on similar mechanisms as those of polyelectrolyte gels, a class of artificial "smart" materials. In both species, time-courses of forisome length and diameter were variable and lacked correlation, arguing against a simple causal relationship between changes in length and width. Moreover, changes in the geometry of soybean forisomes differed qualitatively between Ca(2+)- and pH-responses, suggesting that divalent cations and protons target different sites on the forisome proteins.