R.Y. Nuwayhid

Low cost stove-top thermoelectric generator for regions with unreliable electricity supply

During the winter months in regions where constant electric power supply cannot be relied upon, power may be derived parasitically from heating stoves. A proportion of heat from these 20–50 kW wood or diesel-heated stoves may be utilized to drive a thermoelectric generator (TEG) consisting of several commercially available low-cost modules. These are Peltier modules operating in a power generating mode and adapted to the low-flux regime coupled with hot side temperatures of 100–300 °C. Two commercially available modules are considered. The generator is then theoretically re-evaluated with the Peltier modules re-designed in order to produce maximum power in a simple and cheap manner allowing easy commercial production using existing technology. A current power target is set at 100 W for a minimum domestic use.

Price-driven economic order systems from a thermodynamic point of view

Many researchers have attempted to bridge their fields with others to gain insight into their own, benefiting from the synergies of such processes. As markets have become increasingly more competitive, disorder has become a prevailing characteristic of modern productive systems operating in complex, dynamic and uncertain environments. Some researchers in the discipline of management science/operational research have applied information theory and entropy approaches to account for disorder when modelling the behaviour of productive systems. However, few have applied classical thermodynamics reasoning to modelling such systems. The present paper postulates that the behaviour of production systems very much resembles those of physical systems. Such a parallel suggests that improvements to production systems might be achievable by applying the first and second laws of thermodynamics to reduce system entropy (or disorder). To demonstrate the applicability of these laws, the economic order (production) quantity model is used as an illustrative example.

On entropy generation in thermoelectric devices

In this paper, a comparison between the Entropy Generation Minimization method and the Power Maximization technique is presented. The assessment is performed by analyzing, as a typical example of direct conversion heat engines, the thermoelectric generator. The effects of heat-leak and finite-rate heat transfer on the performance of the generator, which is modeled as a Carnot-like engine with internal irreversibilities, are studied. Even though both methods lead to the same conclusions, the entropy generation minimization method, when applied for such an inherently irreversible device, is shown to be less straight forward than the power maximization technique requiring careful accounting of the different sources of irreversibility. Moreover, the entropy generation rate vs. efficiency behavior of the generator reveals that the efficiency at minimum entropy generation rate and the maximum efficiency are distinct.

The realization of a simple solar tracking concentrator for university research applications

A tracking parabolic concentrator was built from easily available and affordable components. Simplicity and ease of assembly were prime considerations. Considerable experience was gained in the design, assembly and testing. The system performed reasonably well considering its simplicity and rapid assembly. As an educational tool, demonstrating both energy conversion and control, or for simple high temperature experiments and applications, any university could easily set up a similar working concentrator at a very low cost.

On the thermodynamic treatment of diffusion-like economic commodity flows

The flow of a commodity is modelled as a quasi-thermodynamic irreversible process. The flow is treated not as a mass quantity, but more like a transient energy quantity. A commodity is thus considered an artefact that depends on whether it resides or is stored within the system or is in transit across the system boundary to the surroundings. This allows the use of the fundamental laws of thermodynamics and brings further insight into the process of commodity diffusion. The methods of irreversible thermodynamics are also considered and a coupling relationship between commodity price and quality is derived.

THE SOLID WASTE MANAGEMENT SCENE IN GREATER BEIRUT

The magnitude of the solid waste problem in Beirut (Lebanon) is apparent to any onlooker. Waste collection has improved recently but is frequently incomplete and sometimes sporadic. Considerable labour problems exist and are made worse by the disruption from the aftermath of civil war. The most suitable future disposal methods have not been fully studied, and existing disposal sites and plants are near to saturation or collapse. In order to start a new waste management study correctly, the first step was to analyse the waste composition, characteristics and generation rates. The authors attempt to show that some form of incineration with energy recovery may be the preferred disposal option given the current local prevailing social conditions. Composting is argued to be the next choice. Direct landfill of untreated waste is the choice for the present time, but its continuance is open to question if new landfills are not identified and permitted to be used.

A universal model for studying the performance of Carnot-like engines at maximum power conditions

A universal model for studying the performance of endoreversible heat engines with heat leak is presented. By exploiting finite-time thermodynamics, the new model allows detailed analyses of Carnot-like engines under combined modes of heat supply and/or release. Many established laws and major conclusions derived in several references are shown to represent very special cases of the new formulation. Furthermore, as a special case of the general model, the performance of endoreversible heat engines under combined conduction, convection, and radiation heat transfer modes is studied and generated results are displayed graphically.

Evolution of power and entropy in a temperature gap system with electric and thermoelectric influences

Simple thermodynamic modeling of heat engines as thermal gap systems provides useful insight on the performance of power plants. When a temperature difference exists, a potential for power production ensues, and optimization is naturally sought. When electric and/or thermoelectric effects are present, the entropic behavior of such systems changes somewhat. An optimum power extraction temperature is found to be related to the so-called CNCA optimum temperature. The opportunity to generate thermoelectric power in a temperature gap is discussed in some detail in a fashion that renders it analogous to many current thermodynamic optimization studies.

The effect of planet thermal conductance on conversion of solar energy into wind energy

Endoreversible thermodynamics are used for studying the influence of a planets thermal conductance on conversion of solar energy into wind energy. Results indicate a strong dependence of the rate of wind energy generated on the amount of heat leaking by conduction form the illuminated side to the dark side of the planet. The upper boundary for the conversion efficiency of solar energy into wind energy derived in DeVos and Flater [Am. J. Phys.59(8), 251–254 (1991)] is found to be well above the actual value calculated here. Furthermore, an upper limit for the planets dimensionless thermal conductance, a function only of the thermal conversion efficiency, is also determined.

The Efficiency at Maximum Power Output of a Carnot Engine with Heat Leak

Endoreversible thermodynamics are used for studying the performance of Carnot engines with heat leak. This is done by adding a heat leak term into a variation of the model suggested by DeVos [1]. Heat transfer across the engine is assumed to occur via a conduction/convection mechanism and Newtons law of cooling is employed to model the heat transfer processes. The efficiency at maximum power output is found to be deeply affected by the rate of heat leak. Moreover, the Curzon-Ahlborn relation [2] is shown to represent a special case of the new formulation. Since the suggested model allows more flexibility in predicting actual engines performance, its use is recommended in thermodynamics courses.