• Energy Research

A macro rectangular-channel flat-plate solar thermal collector is designed and examined in this study. It consists of a set of adjacent macro rectangular channels formed between the upper, lower, and fin-parts of an absorber plate, thus, overcoming the necessary welding between the absorber plate and riser tubes used in conventional flat-plate collectors. An optimization model is suggested and solved to obtain an optimal design of the proposed collector. After that, a detailed dynamic mathematical model of this collector is presented and numerical simulation is carried out using matlab. Furthermore, a comparison with a conventional sheet-and-tube solar thermal collector is investigated and parametric analysis is conducted under both steady-state and dynamic conditions. The results reveal that the designed collector yields an enhancement of 8% for integrated thermal efficiency under transient regime and an average improvement of 12% for steady-state efficiency when compared with the conventional collector. In addition, the influence of the variation of different parameters, such as the mass flow rate of the heat transfer fluid (HTF), the thickness of different parts of the absorber plate, and the number of channels, on the performance of the proposed collector is presented. From an economical perspective, the cost of materials composing the new collector is less than that of materials composing the conventional one.

This paper presents an evaluation of an optimized Hybrid Pneumatic-Combustion Engine (HPCE) concept that permits reducing fuel consumption for electricity production in non-interconnected remote areas, originally equipped with hybrid Wind–Diesel System (WDS). Up to now, most of the studies on the pneumatic hybridization of Internal Combustion Engines (ICE) have dealt with two-stroke pure pneumatic mode. The few studies that have dealt with hybrid pneumatic-combustion four-stroke mode require adding a supplementary valve to charge compressed air in the combustion chamber. This modification means that a new cylinder head should be fabricated. Moreover, those studies focus on spark ignition engines and are not yet validated for Diesel engines. Present HPCE is capable of making a Diesel engine operate under two-stroke pneumatic motor mode, two-stroke pneumatic pump mode and four-stroke hybrid mode, without needing an additional valve in the combustion chamber. This fact constitutes this study’s strength and innovation. The evaluation of the concept is based on ideal thermodynamic cycle modeling. The optimized valve actuation timings for all modes lead to generic maps that are independent of the engine size. The fuel economy is calculated for a known site during a whole year, function of the air storage volume and the wind power penetration rate.

This paper presents a brief review of the conventional and renewable energy statuses, in Lebanon, as well as of the principal problems facing the electricity of Lebanon Company (EDL). In addition, an analytical-critical review of the latest three official Lebanese electricity plans is presented. Furthermore, two future electricity generation plan-scenarios for Lebanon are investigated, where multi variables are examined, namely: cost, environment and tariff. First, an economical-environmental optimization is carried out, where two reasonable scenarios are introduced based on the fuel source of CCGT power plants. Results revealed that the investment in wind energy and natural gas for power production should be a main concern in the future. Second, an optimization of the average electricity tariff for each of the two investigated generation scenarios is studied, where three different approaches are illustrated. Results confirm that all tariff plans are acceptable and convincing, and that the use of natural gas in CCGT plants is always preferred against gasoil. Moreover, the optimized average tariff is maximally a double of the current EDL average tariff, which is very convincing compared with the actual cost of electricity for the current Lebanese electricity sector.

In this paper, we describe an optimization followed by a fuel-saving evaluation of a new concept of a hybrid pneumatic–combustion engine that can be obtained by modifying a conventional internal combustion engine without developing a new cylinder head. Until now, most studies on the pneumatic hybridization of internal combustion engines have dealt with a two-stroke pure pneumatic mode. The few concept studies that have dealt with a hybrid pneumatic–combustion four-stroke mode required a supplementary valve to be added to charge compressed air in the combustion chamber. This heavy modification cannot be carried out by simply adjusting an existing internal combustion engine because a new cylinder head should be developed. It is therefore not logical to suggest this concept as an option in vehicle powertrains to reduce fuel consumption. Moreover, those studies focus on spark-ignition engines; there are reasons to think that their concepts might not work adequately for diesel engines. Our concept is capable of making a diesel engine operate under two-stroke pneumatic motor modes, two-stroke pneumatic pump modes and four-stroke hybrid modes, without requiring an additional valve in the combustion chamber. This fact constitutes our study’s strength and innovation. The evaluation of our concept is based on ideal thermodynamic cycle modeling. The optimized valve actuation timings for all modes lead to generic maps that are independent of the engine size. The fuel economy is calculated based on the new European driving cycle and on the assessment and reliability of transport emission models and inventory system urban and rural cycles.

AbstractThis paper presents a detailed review of EDL (Electricité du Liban). It displays the institution's technical problems at the level of electricity generation, transmission and distribution as well as the administrative and financial states and suggests several recommendations. It is obvious that EDL suffers a great shortage in its generating capacity and human resources and would not be effective without conducting a national strategy that includes radical solutions.

This paper provides a recent overview of the exact, approximate, and hybrid optimization methods that handle Multi-Objective Mixed-Integer Non-Linear Programming (MO-MINLP) problems. Both the domains of exact and approximate research have experienced significant growth, driven by their shared goal of addressing a wide range of real-world problems. This work presents a comprehensive literature review that highlights the significant theoretical contributions in the field of hybrid approaches between these research areas. We also point out possible research gaps in the literature. Hence, the main research questions to be answered in this paper involve the following: (1) how to exactly or approximately solve a MO-MINLP problem? (2) What are the drawbacks of exact methods as well as approximate methods? (3) What are the research lines that are currently underway to enhance the performances of these methods? and (4) Where are the research gaps in this field? This work aims to provide enough descriptive information for newcomers in this area about the research that has been carried out and that is currently underway concerning exact, approximate, and hybrid methods used to solve MO-MINLP problems.

AbstractIn Canada, off-grid power production is significant, with more than 200,000 people living in about 300 remote communities scattered across Yukon, the Northwest Territories, Nunavut, and other islands. Most of these isolated sites rely on diesel to generate electricity. The operation of these remote isolated grids run on a deficit in the order of hundreds of millions of dollars yearly and must therefore be subsidized by the government. Low and high penetration wind–diesel hybrid systems (WDS) have been experimented to reduce diesel consumption. In a previous article, we explored the re-engineering of current diesel power plants with the introduction of high penetration wind systems using compressed air energy storage (CAES). This is a viable alternative to increase the overall percentage of renewable energy and reduce the cost of electricity, to increase the diesel engine lifetime and efficiency and to decrease their fuel consumption and GHG emissions. In this paper, we present the operative principle of this hybrid system, its economic benefits and advantages. Finally, we apply this concept in the case of a Canadian Nordic village to demonstrate the real energetic, ecological and economic potential of this system.

Water heating contributes an important proportion of residential energy consumption all around the world. Different kinds of domestic hot-water production systems exist. The operational cost, environmental effect and performance of these systems differ according to various energy sources, climates, system types and system designs. Hence, the proper choice of a domestic hot-water system could save energy, protect nature and reduce operational costs, significantly. This paper illustrates, to the best of the author's knowledge, the existing water-heating systems all along with the principle, advantages, disadvantages and state-of-the-art for each. Six different categories were presented, namely wood, oil/gas, electric, heat pump, solar and instantaneous systems. The heat-pump systems were further classified into several groups, namely air source, ground source, solar assisted, ground source-solar assisted, photovoltaic–thermal and gas-engine driven systems. In addition, concerning solar water heating, different types of systems and collectors were presented and reviewed. Principal conclusions from the review are outlined and a general approach to recommend the appropriate water-heating system is proposed.