The “shell” dryer—modelling and experimentation

The “shell” dryer is an African solar food dryer which uses natural convection. Its design has been defined by users, in terms of local working conditions and ease of use. However, it is necessary to optimize the design of the dryer's air flow section for best performance. We present here a theoretical study of a simple process using mathematical modelling tools.     

A “sleeper” awakes: tidal current power

Tidal currents are formed by the energy dissipated by the tides. These can be thalassic, estuarine or fluvial. There has been a growing interest to harness these currents and turn the energy into electrical power. The potential is considerable. The technology is in existence or adaptable. The sites are numerous, though as with most ocean energies, only a small fraction of the global potential could be converted. The paper provides a brief review of an area that has been scrutinized for more than quarter of a century.     

Plea for an “European heat pump consortium”

We already share population crowding and environmental pollution. In today's world, we have no other option than to share also technologies, market and investments. In a renewable energy society, we are in transition from an association of academics and volonteers to a fully professional organisation.Environmental energy harnessing with heat pumps has to follow this trend for the greater benefit of its market share in Europe as well as abroad. Constitution of an “European Heat Pump Consortium” is a way of choice to implement this trend.Its usefuliness is to be demonstrated in influencing consumers and market by:

• — Local and international information exchange between professionals and the public at large

• — Creation of, support for and/or participation in demonstration and dissemination projects

• — Cooperation with technical and political organisations and with industry and SME's.

     

The concept “environment” in exergy analysis: Some special cases

The concept “environment” is of considerable importance in present-day engineering thermodynamics.Introduction of this concept in operation brings not only simplification of the methods of solving classical thermodynamic problems, but also gives the exergy method which forms the major new part of thermodynamics, including some parts of biology, economics and other fields of science.But practice shows that it is necessary to define the concept “environment” more precisely in some cases.     

Modelling and experimentation of the “Shell” dryer

The “Shell” dryer is an African solar food dryer using natural convection. Its design has been defined by users, in function of local working conditions and of its easy using. But it is necessary for the best behaviour of this dryer to optimize its air flow section design. We present here a theoretical study of a “rustic” process, through mathematical modelisation tools.     

Comment upon “Public goods and private interests: understanding non-residential demand for green power”

This article presents a critique of the recent contribution to Energy Policy (November 2001) by Wiser, Fowlie and Holt, entitled, “Public goods and private interests: understanding non-residential demand for green power”. In their article, the aforementioned authors explore the proposition that business and other organisations adopt green power, and will pay even a premium for it, because of what the authors describe as “altruism”. According to the article below, although Wiser et al. address an important problem and raise interesting issues, their attempt at challenging received theory and existing paradigms is undermined by the manner in which their research was undertaken. Deficiencies arise with regard to survey techniques, data preparation, model specification, and statistical methods. The deficiencies in their research methods cast doubt upon their findings, facilitating alternative interpretations of their empiricism.     

The impact of electricity market liberalization in Turkey: “Free consumer” and distributional monopoly cases

Electricity sector has grown substantially in Turkey since the early 1960s as a result of rapid industrialization and urbanization. The vertically integrated state-owned company had a legally established monopoly on the generation, transmission and distribution of electricity in Turkey. With the support and encouragement of international organizations like the World Bank, Turkey has initiated a comprehensive program to liberalize and privatize the electricity market in 2001. The liberalization of the electricity market in Turkey started in the distribution side of the market. The distribution network was divided into 21 distribution regions and in each of these, separate – initially state-owned – distribution companies have been authorized to distribute and sell electricity. The plan envisaged to complete privatization of all distribution companies until the end of 2006. This study compares the welfare implication of privatization of the distribution networks by comparing two extreme cases, a pure regional distributional monopoly case and a representative pure “free” consumer case, with a benchmark case of administered price regulation. For this purpose, we develop a simulation model of the Turkish electricity system, and use the data on generation and distribution costs. Our simulation analysis shows that substantial welfare losses occur if the distributional companies behave as regional monopolists. Our findings reiterate the importance of regulation and market design.     

The Fundamentals of Integrating “the commons”: Application as community tissue or urban implant

Clarifying the means by which we define and shape the commons, can become the platform from which we can seek to achieve community-scale integration in service to principles of sustainability. This paper presents the formulation of energy-related environmental variables — sun, light, wind and water — in “envelope form” for purposes of modeling alternative integrative patternings of communities as “tissue on the land”. Such modeling yields prototype designs of urban districts, urban blocks and/or individual buildings whose designs capitalize on passive energy manipulation as a “first order” response, thus structuring strategies for the integration of efficient “second order” metabolic systems which together provide the technical base for energy-related resource management.     

“Energy Tower” combined with pumped storage and desalination: Optimal design and analysis

The “Energy Tower” (ET) is a power plant project which uses hot dry air and seawater to produce electricity. An optimized design of a system that is a combination of an ET, pumped storage and seawater desalination plant is considered. A model set covering each subsystem, and results of the optimized design for a project in the area of Eilat are presented. The additional benefit from combining the systems comes from an efficient use of the energy in the brine water coming from the desalination process, and from using pumped storage in an unconventional way. The benefits of the combined system lead to an increase of 14% in the annual net profit, compared to the sum of profits from optimally designed stand-alone systems.     

“FRAC ” — A simulation code for forced fluid flow and transport in fractured, porous rock

The 3D Finite Element Program FRACTure was developed with the specific aim of studying the coupling of interactive mechanisms in geoscience and in particular those relevant to the long term behaviour of a Hot Dry Rock reservoir. The flexible modular structure facilitates the addition of further processes and elements to the existing library and the handling of linear and non-linear constitutive laws and the calculation of their interactions. The Hot Dry Rock applications involve essentially forced fluid flow of cool fluid injected into a hot fractured rock matrix. A study of the relevant processes required finite element solutions for the hydraulic, thermal and elastic fields and especially their interactions. Particular attention has been paid to modelling the perturbations arising from poro-elastic and thermo-elastic effects in the rock matrix and of a non-linear, stress dependent joint closure law. The fracture network is designed in a way to represent nature as realistically as possible: fracture flow takes place along planes or in pipes (fracture intersections), porous matrix flow in 3D bodies. In devising the coupling scheme careful thought has been given to the different time constants for each physical process. Apart of simulating the coupled Hot Dry Rock behaviour, the code has been successfully practised in a variety of applications in geoscience: analysis of geoelectric measurements, radon transport, solute tracer tests, simulations of heat probe operations and hydrogeologic system modelling.     

Shape of “True” transition boiling curve and two‐mode boiling

Two‐mode boiling could occur on the same heating element, which provided information on the criterion separating the stable and metastable boiling regimes. The “equal‐area” criterion based on the complete boiling curve interpreted the criterion of coexistence of the two boiling modes. However, the transition boiling curve could not be constructed by the pool boiling tests. Literature works adopted various correlations of transition boiling curves for analysis, but failed to recognize the possible errors incorporated in such an approximation. This paper demonstrated the relative errors embedded in calculating the equal‐area criterion by assuming various shapes of the transition boiling curve. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(7): 593–601, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10113     

Chimney effect in a “T” form cavity with heated isothermal blocks: The blocks height effect

In this paper, a numerical study of natural convection from a two dimensional “T” form cavity with rectangular heated blocks is conducted. The blocks are identical, and the domain presents a symmetry with respect to a vertical axis passing through the middle of the opening. The governing equations are solved using a control volume method, and the SIMPLER algorithm for the velocity–pressure coupling is employed. Special emphasis is given to detail the effect of Rayleigh number and block height on the heat transfer and the flow rate generated by the chimney effect. The results are given for the parameters of control as, 10⁴Ra3×10⁶, Pr=0.71, opening diameter (C=l^′/H^′=0.15), blocks gap (D=d^′/H^′=0.5) and blocks height (1/8B=h^′/H^′1/2). These results show that the heat transfer variation with Ra is in the same manner as those met in the case of the vertical smooth or ribbed channels.     

Nanomaterials for benign indoor environments: Electrochromics for “smart windows”, sensors for air quality, and photo-catalysts for air cleaning

Nanomaterials can be used in a number of technologies in order to accomplish benign indoor environments. This paper takes a unified view on this problem from a solar-energy-based perspective and specifically considers electrochromics for achieving good day-lighting jointly with energy efficiency, sensors aimed at air quality assessment, and photocatalysis for air cleaning. Recent results, mainly from the authors’ laboratories, are reported for all of these areas.     

European solar standards : Final approval of CEN/TC312 “Thermal solar systems and components”

A powerful tool for the promotion of the use of the solar thermal systems is the existence of technical standards and regulations for these industrial products. These technical specifications permit the quality improvement of the products and, consequently, the increase of the consumers' confidence to this technology. Eva Kotsaki, CEN/TC 312 Secretary, CRES — Energy Policy and Planning Division, Greece provides an update on the current position regarding European solar thermal standards.     

Assessment of an “Energy Tower” potential in Australia using a mathematical model and GIS

“Energy Tower” is a technology for producing renewable and clean electricity by means of cooling hot and dry air, which is continuously supplied to arid lands. We assess the potential of an Energy Tower by incorporating topographic and meteorological parameters into a computational model, providing evaluations for the net power production and the electricity production cost. We formulate a highly simplified model for the Energy Tower’s flow, setup and process a spatial dataset of topographic and Meteorological upper air parameters. The model was applied to the Australian continent. A model simulation of one annual cycle enabled the ranking and selection of promising sites. The highest potential for energy towers is in the Port Hedland region, where favorable meteorological and topographic conditions would result in high average net power (≈370 ± 160 MW), potentially providing the electricity needs of 0.5 million people, for an economically competitive costs (3.5 ¢kWh).