Oussama Ibrahim | Lebanese University (original) (raw)

Papers by Oussama Ibrahim

Renewable & Sustainable Energy Reviews, Apr 1, 2013

This paper presents a review of the energy status, conventional and renewable, in Lebanon and ill... more This paper presents a review of the energy status, conventional and renewable, in Lebanon and illustrates their problems with the suggested recommendations. In addition, a detailed review of the principal directorates of the electricity of Lebanon Company (EDL) is also presented all along with the existing problems and recommended solutions. An economic, environmental optimization of different power sources is studied, where three scenarios are introduced based on the fuel source of different CCGT power plants. The results emphasized on the maximum possible use of wind energy and natural gas in electricity generation. Based on the optimization study, a five-year master plan for electricity generation is modeled. The suggested plan has an investment capital cost of 5553 M$ with the savings and additional incomes being 5900 M$ compared to EDL financial status in the adopted base year, 2009. In addition, this plan exceeds the trend to introduce a 12% share of renewable energy in the power sector by 2020, where the share is supposed to be about 15% out of the total installed capacity before this date. The concluding remarks highlight the role of politics in the development of the energy sector.

Journal of heat transfer, Feb 27, 2018

The performance of a flat-plate solar collector is usually assessed by its efficiency. This effic... more The performance of a flat-plate solar collector is usually assessed by its efficiency. This efficiency is normally defined on a steady-state basis, which makes it difficult to correctly track the instantaneous performance of the collector in various case-studies. Accordingly, this paper proposes an improved definition of instantaneous efficiency of a flat-plate solar collector used as a part of a solar water heating system. Using a predeveloped model by the authors for such a system, the proposed efficiency-definition is examined and compared with the conventional one for specific case studies. The results show that the improved definition of efficiency records reasonable values, i.e., no over-range values are observed contrast to the case of conventional efficiency-definition. Furthermore, this suggested efficiency approximately coincides with the conventional one at a wide range of time, as long as the system is operating in the so-called trans-steady-state phase or when the system is off-operational provided that the instantaneous rate of heat stored in the heat transfer fluid (HTF) is less than or equal to zero. As a result, the improved efficiency-definition yields more realistic results in reflecting the performance of a flat-plate collector in an active solar water heating system and is recommended to be used.

Energy, 2014

ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (... more ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (air source heat pump water heater). The developed model is used to assess its performance in the Lebanese context. It is shown that for the four Lebanese climatic zones, the expected monthly values of the average COP (coefficient of performance) varies from 2.9 to 5, leading to high efficiencies compared with conventional electric water heaters. The energy savings and GHG (greenhouse gas) emissions reduction are investigated for each zone. Furthermore, it is recommended to use the ASHPWH during the period of highest daily ambient temperatures (noon or afternoon), assuming that the electricity tariff and hot water loads are constant. In addition, an optimal management model for the ASHPWH is developed and applied for a typical winter day of Beirut. Moreover, the developed dynamic model of ASHPWH is used to compare the performance of three similar systems that differ only with the condenser geometry, where results show that using mini-condenser geometries increase the COP (coefficient of performance) and consequently, more energy is saved as well as more GHG emissions are reduced. In addition, the condenser “surface compactness” is increased giving rise to an efficient compact heat exchanger.

Energy and Buildings, Jun 1, 2014

This paper presents the dynamic modeling of a domestic hybrid water heating system. The system is... more This paper presents the dynamic modeling of a domestic hybrid water heating system. The system is composed of a solar collector, a heat pump water heater, a wind turbine, a battery and a hot water storage tank. Both air-source and geothermal-heat pumps are investigated. Detailed mathematical dynamic models of the individual components are presented and validated. Simulations for typical days in summer and winter for Beirut and Cedars, two Lebanese locations with different meteorological and demographic conditions, are conducted using Matlab software. A renewable coverage factor (RCF) is defined, representing the renewable energy share with respect to the total delivered energy. Results reveal that the proposed hybrid system is capable of securing all hot water needs in all case studies and RCF is always above 63%. Furthermore, an energetic, economic optimal management model is developed for the proposed hybrid system. It is applied to the considered case studies, where results illustrate the optimum size of each of the system components as well as the optimum energy-flow distributions among them over two investigated time periods, five and ten years. It is noticed that the initial cost of the hybrid system is acceptable and important annual savings are obtained.

Energy Procedia, 2012

This paper presents a detailed review of EDL (Electricité du Liban). It displays the institution'... more This 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.

Journal of Solar Energy Engineering-transactions of The Asme, Jun 26, 2018

A macro rectangular-channel flat-plate solar thermal collector is designed and examined in this s... more 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.

Journal of building engineering, Nov 1, 2018

Abstract The concept of integrated energy management is presented in this study. It defines a glo... more Abstract The concept of integrated energy management is presented in this study. It defines a global strategy for the management and control of an energy system following five steps, namely, i) selection of resources and technologies, ii) mathematical modeling, iii) optimal sizing, iv) optimal references and v) operational control. First, the above-mentioned concept is introduced and explained. After that, integrated energy management is applied for two case studies; i) a simple conventional domestic electric water heater and ii) a hybrid domestic water heating system mainly composed of an air source heat pump, flat-plate solar thermal collectors and wind turbines. These systems are numerically investigated using both Matlab and Trnsys softwares in different weather climates. Compared with specified base cases, results prove that the introduced concept is very efficient from the energetic and economic points of view, where savings in operational costs touched 29% in a typical meteorological year for case I and about 15% in a typical week of the winter for case II.

Solar Energy, May 1, 2017

Recently, more and more research is being conducted on thermo-activated building walls with the u... more Recently, more and more research is being conducted on thermo-activated building walls with the use of circulating water or other fluids for the aim of decreasing and shifting the heating and/or cooling loads. In this context, we present a novel concept of the active embedded-pipe envelope systems. The system consists of an active closed-loop-water-pipes embedded in the building exterior walls to harvest and utilize the solar energy gain on the south wall exterior surface to decrease or offset the heat loss through the north wall and enhance thermal comfort. During non-cloudy winter days, a significant amount of solar energy hitting the south (insulated) facade is not transferred to the inside environment. In this study, a comparative experimental setup is carried out to test the system's efficiency and compare its performance to that of a static insulated envelope without the system. Also, a numerical model is developed and validated against experimental measurements. Numerical simulations with a parametric study are carried out to examine the active wall loop system's efficiency for different design and operating parameters. The main conclusion derived from this study is that the system performs very well in the Mediterranean climates (or similar climates) and to a lower extent in the cooler ones. However, its performance is highly dependent on several design, climatic, and operating variables which should be optimized to have the best performance.

Journal of building engineering, Jul 1, 2018

Abstract Building envelope reflective finishing can play a major role in the energy saving of bui... more Abstract Building envelope reflective finishing can play a major role in the energy saving of buildings. Extensive research demonstrated the influence of such a finishing on the external surface of horizontal and vertical walls; however, research on low-emissivity (low-e) finishing at the interior surface of vertical envelopes is hardly found in the literature. Accordingly, this study starts with a state-of-the-art on low-e applications in buildings. Dynamic simulations are then carried out to investigate the thermal and hygro-thermal behavior of envelopes with interior surface low-e coating, during heating and cooling season in Lyon, France. A new methodology to simulate the operative temperature of the indoor environment, considering the emissivity of the indoor surfaces, is proposed. Results showed that the energy-saving potential of low-emissivity finishing is major when applied to low/non-insulated buildings, particularly when considering thermal comfort. A foreseen application is to couple this technology with a system that controls the indoor operative temperature, reaching energy saving potentials of between 7% and 13%. If an operative-temperature-based control is implemented at a position near a low-emissivity surface, energy savings of up to 22% could be achieved. Beneficial contribution is obtained when simulating low-e coating coupled with interior aerogel plaster, where energy savings of 21% and 30% are obtained for 0.5 cm and 1 cm of aerogel plaster, respectively. This thin layer of aerogel plaster demonstrated also to be effective in retrofitting existing walls to reduce the moisture risks. It is worth mentioning that from an architectural point of view, a low- emissivity coating means a metal appearance wall finishing, which needs to be accepted by the occupants.

Building and Environment, Feb 1, 2014

Water heating contributes an important proportion of residential energy consumption all around th... more 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, photovoltaicethermal 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.

Renewable and Sustainable Energy Reviews, 2013

This paper presents a review of the energy status, conventional and renewable, in Lebanon and ill... more This paper presents a review of the energy status, conventional and renewable, in Lebanon and illustrates their problems with the suggested recommendations. In addition, a detailed review of the principal directorates of the electricity of Lebanon Company (EDL) is also presented all along with the existing problems and recommended solutions. An economic, environmental optimization of different power sources is studied, where three scenarios are introduced based on the fuel source of different CCGT power plants. The results emphasized on the maximum possible use of wind energy and natural gas in electricity generation. Based on the optimization study, a five-year master plan for electricity generation is modeled. The suggested plan has an investment capital cost of 5553 M$ with the savings and additional incomes being 5900 M$ compared to EDL financial status in the adopted base year, 2009. In addition, this plan exceeds the trend to introduce a 12% share of renewable energy in the power sector by 2020, where the share is supposed to be about 15% out of the total installed capacity before this date. The concluding remarks highlight the role of politics in the development of the energy sector.

Energy and Buildings, 2014

Energy, 2014

ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (... more ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (air source heat pump water heater). The developed model is used to assess its performance in the Lebanese context. It is shown that for the four Lebanese climatic zones, the expected monthly values of the average COP (coefficient of performance) varies from 2.9 to 5, leading to high efficiencies compared with conventional electric water heaters. The energy savings and GHG (greenhouse gas) emissions reduction are investigated for each zone. Furthermore, it is recommended to use the ASHPWH during the period of highest daily ambient temperatures (noon or afternoon), assuming that the electricity tariff and hot water loads are constant. In addition, an optimal management model for the ASHPWH is developed and applied for a typical winter day of Beirut. Moreover, the developed dynamic model of ASHPWH is used to compare the performance of three similar systems that differ only with the condenser geometry, where results show that using mini-condenser geometries increase the COP (coefficient of performance) and consequently, more energy is saved as well as more GHG emissions are reduced. In addition, the condenser “surface compactness” is increased giving rise to an efficient compact heat exchanger.

This paper presents a dynamic simulation model to predict the performance of an air source heat p... more This paper presents a dynamic simulation model to predict the performance of an air source heat pump water heater (ASHPWH). The mathematical model consists of submodels of the basic system components i.e. evaporator, condenser, compressor, and expansion valve. These submodels were built based on fundamental principles of heat transfer, thermodynamics, fluid mechanics, empirical relationships and manufacturer's data as necessary. The model simulation was carried out using MATLAB software. Refrigerant R134a with two different reservoir volumes 150L & 200L are investigated. Additionally, different ambient air temperatures are considered. Results show that the rate of hot water production increases as the water reservoir volume decreases and the integrated COP increases as the ambient temperature increases.

This thesis presents a detailed review of the conventional and renewable energy statuses, in Leba... more This thesis presents a detailed review of the conventional and renewable energy statuses, in Lebanon, as well as of the principal problems facing the electricity of Lebanon Company (EDL). Besides, future electricity generation plan-scenarios for Lebanon are investigated, where multi variables are examined and optimized, namely: cost, environment and tariff. Results reveal that the investment in wind energy and natural gas for power production should be a main concern in the future. In addition, a comprehensive review of different domestic water heating systems is developed, where principal conclusions reveal that heat pump water heaters and solar water heating systems are recommended to be used. Accordingly, a general road map that controls the choice of a water heating system for domestic use from energetic and environmental points of view is developed. Moreover, dynamic simulation model of an air source heat pump water heater is presented and validated. This model is then used to ...

The aim of this work is to propose an optimal sizing method for a hybrid cooling system with mini... more The aim of this work is to propose an optimal sizing method for a hybrid cooling system with minimum energy consumption and maximum share of renewable resources. For this purpose, a hybrid cooling system that benefits from renewable energy resources is designed and modeled using Trnsys 17. Then, an optimal sizing method where the problematic is formalized as a mathematical problem under constraints is presented. Finally, the results are obtained and discussed for the two case studies selected, namely Marseilles-France and BeirutLebanon.

Journal of Building Engineering

Journal of Building Engineering

Journal of Heat Transfer

The performance of a flat-plate solar collector is usually assessed by its efficiency. This effic... more The performance of a flat-plate solar collector is usually assessed by its efficiency. This efficiency is normally defined on a steady-state basis, which makes it difficult to correctly track the instantaneous performance of the collector in various case-studies. Accordingly, this paper proposes an improved definition of instantaneous efficiency of a flat-plate solar collector used as a part of a solar water heating system. Using a predeveloped model by the authors for such a system, the proposed efficiency-definition is examined and compared with the conventional one for specific case studies. The results show that the improved definition of efficiency records reasonable values, i.e., no over-range values are observed contrast to the case of conventional efficiency-definition. Furthermore, this suggested efficiency approximately coincides with the conventional one at a wide range of time, as long as the system is operating in the so-called trans-steady-state phase or when the syste...

Renewable & Sustainable Energy Reviews, Apr 1, 2013

This paper presents a review of the energy status, conventional and renewable, in Lebanon and ill... more This paper presents a review of the energy status, conventional and renewable, in Lebanon and illustrates their problems with the suggested recommendations. In addition, a detailed review of the principal directorates of the electricity of Lebanon Company (EDL) is also presented all along with the existing problems and recommended solutions. An economic, environmental optimization of different power sources is studied, where three scenarios are introduced based on the fuel source of different CCGT power plants. The results emphasized on the maximum possible use of wind energy and natural gas in electricity generation. Based on the optimization study, a five-year master plan for electricity generation is modeled. The suggested plan has an investment capital cost of 5553 M$ with the savings and additional incomes being 5900 M$ compared to EDL financial status in the adopted base year, 2009. In addition, this plan exceeds the trend to introduce a 12% share of renewable energy in the power sector by 2020, where the share is supposed to be about 15% out of the total installed capacity before this date. The concluding remarks highlight the role of politics in the development of the energy sector.

Journal of heat transfer, Feb 27, 2018

The performance of a flat-plate solar collector is usually assessed by its efficiency. This effic... more The performance of a flat-plate solar collector is usually assessed by its efficiency. This efficiency is normally defined on a steady-state basis, which makes it difficult to correctly track the instantaneous performance of the collector in various case-studies. Accordingly, this paper proposes an improved definition of instantaneous efficiency of a flat-plate solar collector used as a part of a solar water heating system. Using a predeveloped model by the authors for such a system, the proposed efficiency-definition is examined and compared with the conventional one for specific case studies. The results show that the improved definition of efficiency records reasonable values, i.e., no over-range values are observed contrast to the case of conventional efficiency-definition. Furthermore, this suggested efficiency approximately coincides with the conventional one at a wide range of time, as long as the system is operating in the so-called trans-steady-state phase or when the system is off-operational provided that the instantaneous rate of heat stored in the heat transfer fluid (HTF) is less than or equal to zero. As a result, the improved efficiency-definition yields more realistic results in reflecting the performance of a flat-plate collector in an active solar water heating system and is recommended to be used.

Energy, 2014

ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (... more ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (air source heat pump water heater). The developed model is used to assess its performance in the Lebanese context. It is shown that for the four Lebanese climatic zones, the expected monthly values of the average COP (coefficient of performance) varies from 2.9 to 5, leading to high efficiencies compared with conventional electric water heaters. The energy savings and GHG (greenhouse gas) emissions reduction are investigated for each zone. Furthermore, it is recommended to use the ASHPWH during the period of highest daily ambient temperatures (noon or afternoon), assuming that the electricity tariff and hot water loads are constant. In addition, an optimal management model for the ASHPWH is developed and applied for a typical winter day of Beirut. Moreover, the developed dynamic model of ASHPWH is used to compare the performance of three similar systems that differ only with the condenser geometry, where results show that using mini-condenser geometries increase the COP (coefficient of performance) and consequently, more energy is saved as well as more GHG emissions are reduced. In addition, the condenser “surface compactness” is increased giving rise to an efficient compact heat exchanger.

Energy and Buildings, Jun 1, 2014

This paper presents the dynamic modeling of a domestic hybrid water heating system. The system is... more This paper presents the dynamic modeling of a domestic hybrid water heating system. The system is composed of a solar collector, a heat pump water heater, a wind turbine, a battery and a hot water storage tank. Both air-source and geothermal-heat pumps are investigated. Detailed mathematical dynamic models of the individual components are presented and validated. Simulations for typical days in summer and winter for Beirut and Cedars, two Lebanese locations with different meteorological and demographic conditions, are conducted using Matlab software. A renewable coverage factor (RCF) is defined, representing the renewable energy share with respect to the total delivered energy. Results reveal that the proposed hybrid system is capable of securing all hot water needs in all case studies and RCF is always above 63%. Furthermore, an energetic, economic optimal management model is developed for the proposed hybrid system. It is applied to the considered case studies, where results illustrate the optimum size of each of the system components as well as the optimum energy-flow distributions among them over two investigated time periods, five and ten years. It is noticed that the initial cost of the hybrid system is acceptable and important annual savings are obtained.

Energy Procedia, 2012

This paper presents a detailed review of EDL (Electricité du Liban). It displays the institution'... more This 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.

Journal of Solar Energy Engineering-transactions of The Asme, Jun 26, 2018

A macro rectangular-channel flat-plate solar thermal collector is designed and examined in this s... more 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.

Journal of building engineering, Nov 1, 2018

Abstract The concept of integrated energy management is presented in this study. It defines a glo... more Abstract The concept of integrated energy management is presented in this study. It defines a global strategy for the management and control of an energy system following five steps, namely, i) selection of resources and technologies, ii) mathematical modeling, iii) optimal sizing, iv) optimal references and v) operational control. First, the above-mentioned concept is introduced and explained. After that, integrated energy management is applied for two case studies; i) a simple conventional domestic electric water heater and ii) a hybrid domestic water heating system mainly composed of an air source heat pump, flat-plate solar thermal collectors and wind turbines. These systems are numerically investigated using both Matlab and Trnsys softwares in different weather climates. Compared with specified base cases, results prove that the introduced concept is very efficient from the energetic and economic points of view, where savings in operational costs touched 29% in a typical meteorological year for case I and about 15% in a typical week of the winter for case II.

Solar Energy, May 1, 2017

Recently, more and more research is being conducted on thermo-activated building walls with the u... more Recently, more and more research is being conducted on thermo-activated building walls with the use of circulating water or other fluids for the aim of decreasing and shifting the heating and/or cooling loads. In this context, we present a novel concept of the active embedded-pipe envelope systems. The system consists of an active closed-loop-water-pipes embedded in the building exterior walls to harvest and utilize the solar energy gain on the south wall exterior surface to decrease or offset the heat loss through the north wall and enhance thermal comfort. During non-cloudy winter days, a significant amount of solar energy hitting the south (insulated) facade is not transferred to the inside environment. In this study, a comparative experimental setup is carried out to test the system's efficiency and compare its performance to that of a static insulated envelope without the system. Also, a numerical model is developed and validated against experimental measurements. Numerical simulations with a parametric study are carried out to examine the active wall loop system's efficiency for different design and operating parameters. The main conclusion derived from this study is that the system performs very well in the Mediterranean climates (or similar climates) and to a lower extent in the cooler ones. However, its performance is highly dependent on several design, climatic, and operating variables which should be optimized to have the best performance.

Journal of building engineering, Jul 1, 2018

Abstract Building envelope reflective finishing can play a major role in the energy saving of bui... more Abstract Building envelope reflective finishing can play a major role in the energy saving of buildings. Extensive research demonstrated the influence of such a finishing on the external surface of horizontal and vertical walls; however, research on low-emissivity (low-e) finishing at the interior surface of vertical envelopes is hardly found in the literature. Accordingly, this study starts with a state-of-the-art on low-e applications in buildings. Dynamic simulations are then carried out to investigate the thermal and hygro-thermal behavior of envelopes with interior surface low-e coating, during heating and cooling season in Lyon, France. A new methodology to simulate the operative temperature of the indoor environment, considering the emissivity of the indoor surfaces, is proposed. Results showed that the energy-saving potential of low-emissivity finishing is major when applied to low/non-insulated buildings, particularly when considering thermal comfort. A foreseen application is to couple this technology with a system that controls the indoor operative temperature, reaching energy saving potentials of between 7% and 13%. If an operative-temperature-based control is implemented at a position near a low-emissivity surface, energy savings of up to 22% could be achieved. Beneficial contribution is obtained when simulating low-e coating coupled with interior aerogel plaster, where energy savings of 21% and 30% are obtained for 0.5 cm and 1 cm of aerogel plaster, respectively. This thin layer of aerogel plaster demonstrated also to be effective in retrofitting existing walls to reduce the moisture risks. It is worth mentioning that from an architectural point of view, a low- emissivity coating means a metal appearance wall finishing, which needs to be accepted by the occupants.

Building and Environment, Feb 1, 2014

Water heating contributes an important proportion of residential energy consumption all around th... more 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, photovoltaicethermal 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.

Renewable and Sustainable Energy Reviews, 2013

This paper presents a review of the energy status, conventional and renewable, in Lebanon and ill... more This paper presents a review of the energy status, conventional and renewable, in Lebanon and illustrates their problems with the suggested recommendations. In addition, a detailed review of the principal directorates of the electricity of Lebanon Company (EDL) is also presented all along with the existing problems and recommended solutions. An economic, environmental optimization of different power sources is studied, where three scenarios are introduced based on the fuel source of different CCGT power plants. The results emphasized on the maximum possible use of wind energy and natural gas in electricity generation. Based on the optimization study, a five-year master plan for electricity generation is modeled. The suggested plan has an investment capital cost of 5553 M$ with the savings and additional incomes being 5900 M$ compared to EDL financial status in the adopted base year, 2009. In addition, this plan exceeds the trend to introduce a 12% share of renewable energy in the power sector by 2020, where the share is supposed to be about 15% out of the total installed capacity before this date. The concluding remarks highlight the role of politics in the development of the energy sector.

Energy and Buildings, 2014

Energy, 2014

ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (... more ABSTRACT This paper presents a dynamic simulation model to predict the performance of an ASHPWH (air source heat pump water heater). The developed model is used to assess its performance in the Lebanese context. It is shown that for the four Lebanese climatic zones, the expected monthly values of the average COP (coefficient of performance) varies from 2.9 to 5, leading to high efficiencies compared with conventional electric water heaters. The energy savings and GHG (greenhouse gas) emissions reduction are investigated for each zone. Furthermore, it is recommended to use the ASHPWH during the period of highest daily ambient temperatures (noon or afternoon), assuming that the electricity tariff and hot water loads are constant. In addition, an optimal management model for the ASHPWH is developed and applied for a typical winter day of Beirut. Moreover, the developed dynamic model of ASHPWH is used to compare the performance of three similar systems that differ only with the condenser geometry, where results show that using mini-condenser geometries increase the COP (coefficient of performance) and consequently, more energy is saved as well as more GHG emissions are reduced. In addition, the condenser “surface compactness” is increased giving rise to an efficient compact heat exchanger.

This paper presents a dynamic simulation model to predict the performance of an air source heat p... more This paper presents a dynamic simulation model to predict the performance of an air source heat pump water heater (ASHPWH). The mathematical model consists of submodels of the basic system components i.e. evaporator, condenser, compressor, and expansion valve. These submodels were built based on fundamental principles of heat transfer, thermodynamics, fluid mechanics, empirical relationships and manufacturer's data as necessary. The model simulation was carried out using MATLAB software. Refrigerant R134a with two different reservoir volumes 150L & 200L are investigated. Additionally, different ambient air temperatures are considered. Results show that the rate of hot water production increases as the water reservoir volume decreases and the integrated COP increases as the ambient temperature increases.

This thesis presents a detailed review of the conventional and renewable energy statuses, in Leba... more This thesis presents a detailed review of the conventional and renewable energy statuses, in Lebanon, as well as of the principal problems facing the electricity of Lebanon Company (EDL). Besides, future electricity generation plan-scenarios for Lebanon are investigated, where multi variables are examined and optimized, namely: cost, environment and tariff. Results reveal that the investment in wind energy and natural gas for power production should be a main concern in the future. In addition, a comprehensive review of different domestic water heating systems is developed, where principal conclusions reveal that heat pump water heaters and solar water heating systems are recommended to be used. Accordingly, a general road map that controls the choice of a water heating system for domestic use from energetic and environmental points of view is developed. Moreover, dynamic simulation model of an air source heat pump water heater is presented and validated. This model is then used to ...

The aim of this work is to propose an optimal sizing method for a hybrid cooling system with mini... more The aim of this work is to propose an optimal sizing method for a hybrid cooling system with minimum energy consumption and maximum share of renewable resources. For this purpose, a hybrid cooling system that benefits from renewable energy resources is designed and modeled using Trnsys 17. Then, an optimal sizing method where the problematic is formalized as a mathematical problem under constraints is presented. Finally, the results are obtained and discussed for the two case studies selected, namely Marseilles-France and BeirutLebanon.

Journal of Building Engineering

Journal of Building Engineering

Journal of Heat Transfer

The performance of a flat-plate solar collector is usually assessed by its efficiency. This effic... more The performance of a flat-plate solar collector is usually assessed by its efficiency. This efficiency is normally defined on a steady-state basis, which makes it difficult to correctly track the instantaneous performance of the collector in various case-studies. Accordingly, this paper proposes an improved definition of instantaneous efficiency of a flat-plate solar collector used as a part of a solar water heating system. Using a predeveloped model by the authors for such a system, the proposed efficiency-definition is examined and compared with the conventional one for specific case studies. The results show that the improved definition of efficiency records reasonable values, i.e., no over-range values are observed contrast to the case of conventional efficiency-definition. Furthermore, this suggested efficiency approximately coincides with the conventional one at a wide range of time, as long as the system is operating in the so-called trans-steady-state phase or when the syste...