Global NEST International Conference on Environmental Science & Technology
Water is a very valuable natural resource absolutely necessary for life. Lately water resources a... more Water is a very valuable natural resource absolutely necessary for life. Lately water resources are facing very high pressure from continuously increasing demand. Besides, various areas face water shortage due to decrease of precipitation, irrational use, losses and other reasons. Furthermore the importance of water resources is getting more and more obvious after realising that the water availability is not any longer guaranteed as it was used to be considered until recently. Various water supply methods are applied in different cases in order to satisfy water demand, such as dams, desalination units and water transport. Each of these methods however has different environmental and social impacts. The objective of the present work is to investigate the issues and parameters that identify the water sustainability. To that effect, a detailed literature review for the already defined water sustainability indexes is carried out. Then, the various alternative water supply methods are an...
Global NEST International Conference on Environmental Science & Technology
The utilization of electrical cars is considered as the new tool against the serious problems res... more The utilization of electrical cars is considered as the new tool against the serious problems resulting from the oil products consumption of the transportation sector. Actually, many people believe that the adoption of electro-mobility, especially in the urban areas or small-medium size islands, is the only solution for significant reduction of the environmental impacts of our society. In this context the current work first estimates the real world electricity consumption of commercial electrical cars, including charging and discharging loss, using long term experimental measurements. Accordingly, on the basis of the total electricity consumption and using the electricity generation fuel mix (mainland vs. remote islands) the corresponding air pollutants are predicted. On the other hand, one may estimate the air pollutants emissions of the contemporary private cars using experimental measurements and data provided by the cars’ manufacturers and other external accreditation bodies. Fo...
Electric Vehicles (EVs), accompanied with the use of Renewable Energy Sources (RES), are the solu... more Electric Vehicles (EVs), accompanied with the use of Renewable Energy Sources (RES), are the solution for the decarbonization of the transport sector and are undoubtedly on the rise. Although EVs have been in the limelight over the last decade, little effort has been made towards the proper use of the vehicle's battery. Therefore, a better understanding of Lithium-ion (Li-ion) batteries, since they represent the heart of the majority of electric cars, during the discharging and charging procedure is crucial. The present study, that was experimentally conducted under real-world driving conditions, quantitatively analyzes the energy losses that take place during the charging of a Battery Electric Vehicle (BEV), focusing especially in the previously unexplored 80%-100% State of Charge (SoC) area. The results show that losses, during charging within the abovementioned area, are almost double compared to the 20%-80% SoC area and vehicle's average specific real energy consumption is almost 2 kWh/100 km more, compared to what the driver sees on the EV's dashboard. Furthermore, it is not for the driver's benefit to exceed 80% of SoC during charging, considering the required charging time, the distance that each SoC area provides and the life expectancy of the battery itself. Based on these results and after a thorough literature review, the authors suggest the optimum SoC range within which drivers should operate the EV's battery.
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
In the present paper, the evolution of the velocity field in the blade passages of two radial pum... more In the present paper, the evolution of the velocity field in the blade passages of two radial pump impellers with different curvature and outlet blade angle (β 2 = 20 and 50 degrees) is reported. The study is based on computational modelling. The numerical solution of the discretized three-dimensional, incompressible Navier-Stokes equations over a structured grid is accomplished with a commercial CFD finite-volume code. For each impeller, pressure and relative velocity distributions are presented and analyzed. The flow patterns in the blade passages are monitored, and the mechanisms that dominate the flow field in the different regions of the impeller geometry are discussed.
Hydropower is the most widely used renewable energy source worldwide, contributing almost with 18... more Hydropower is the most widely used renewable energy source worldwide, contributing almost with 18.5% to the fulfillment of the planet electricity generation. However, most locations in Europe appropriate for the installation of large hydro power stations have already been exploited. Furthermore, there is a significant local communities’ opposition towards new large power stations; hence, small hydro power stations remain one
The electricity generation in the Aegean Archipelago islands is determined by increased electrici... more The electricity generation in the Aegean Archipelago islands is determined by increased electricity production costs due to its dependency on imported oil. On the other hand, these islands are favored with considerable wind potential that encourages the realization of wind energy projects. However, due to the stochastic behavior of wind, the respective electricity generation cannot always provide firm capacity to an autonomous electrical power system. To encounter the existing situation, system operators are obliged to limit wind power penetration, this resulting in significant wind energy curtailments. In an attempt to face these problems, the idea of an integrated water pumping energy storage strategy is examined. To investigate the optimum size of a Pumped Hydro Storage (PHS) system, an integrated computational algorithm is developed, based on a well-established sizing procedure methodology that also considers boundary conditions. The numerical code is prepared in "Visual-Basic" environment and a user-friendly computational tool is created, presenting among others the hourly operational status as well as the annual energy yield of the plant. Finally, an application of the proposed numerical code is presented, based on real data like the long-term renewable energy curtailments of existing wind parks (operating in a representative North Aegean island) and the operational characteristics of the PHS system components. By applying the proposed numerical code, the operational parameters of a PHS system may be investigated in detail, while based on the application results obtained, the ability of the wind energy to remarkably contribute in the remote islands' energy balance is illustrated.
Global NEST International Conference on Environmental Science & Technology
Water is a very valuable natural resource absolutely necessary for life. Lately water resources a... more Water is a very valuable natural resource absolutely necessary for life. Lately water resources are facing very high pressure from continuously increasing demand. Besides, various areas face water shortage due to decrease of precipitation, irrational use, losses and other reasons. Furthermore the importance of water resources is getting more and more obvious after realising that the water availability is not any longer guaranteed as it was used to be considered until recently. Various water supply methods are applied in different cases in order to satisfy water demand, such as dams, desalination units and water transport. Each of these methods however has different environmental and social impacts. The objective of the present work is to investigate the issues and parameters that identify the water sustainability. To that effect, a detailed literature review for the already defined water sustainability indexes is carried out. Then, the various alternative water supply methods are an...
Global NEST International Conference on Environmental Science & Technology
The utilization of electrical cars is considered as the new tool against the serious problems res... more The utilization of electrical cars is considered as the new tool against the serious problems resulting from the oil products consumption of the transportation sector. Actually, many people believe that the adoption of electro-mobility, especially in the urban areas or small-medium size islands, is the only solution for significant reduction of the environmental impacts of our society. In this context the current work first estimates the real world electricity consumption of commercial electrical cars, including charging and discharging loss, using long term experimental measurements. Accordingly, on the basis of the total electricity consumption and using the electricity generation fuel mix (mainland vs. remote islands) the corresponding air pollutants are predicted. On the other hand, one may estimate the air pollutants emissions of the contemporary private cars using experimental measurements and data provided by the cars’ manufacturers and other external accreditation bodies. Fo...
Electric Vehicles (EVs), accompanied with the use of Renewable Energy Sources (RES), are the solu... more Electric Vehicles (EVs), accompanied with the use of Renewable Energy Sources (RES), are the solution for the decarbonization of the transport sector and are undoubtedly on the rise. Although EVs have been in the limelight over the last decade, little effort has been made towards the proper use of the vehicle's battery. Therefore, a better understanding of Lithium-ion (Li-ion) batteries, since they represent the heart of the majority of electric cars, during the discharging and charging procedure is crucial. The present study, that was experimentally conducted under real-world driving conditions, quantitatively analyzes the energy losses that take place during the charging of a Battery Electric Vehicle (BEV), focusing especially in the previously unexplored 80%-100% State of Charge (SoC) area. The results show that losses, during charging within the abovementioned area, are almost double compared to the 20%-80% SoC area and vehicle's average specific real energy consumption is almost 2 kWh/100 km more, compared to what the driver sees on the EV's dashboard. Furthermore, it is not for the driver's benefit to exceed 80% of SoC during charging, considering the required charging time, the distance that each SoC area provides and the life expectancy of the battery itself. Based on these results and after a thorough literature review, the authors suggest the optimum SoC range within which drivers should operate the EV's battery.
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
In the present paper, the evolution of the velocity field in the blade passages of two radial pum... more In the present paper, the evolution of the velocity field in the blade passages of two radial pump impellers with different curvature and outlet blade angle (β 2 = 20 and 50 degrees) is reported. The study is based on computational modelling. The numerical solution of the discretized three-dimensional, incompressible Navier-Stokes equations over a structured grid is accomplished with a commercial CFD finite-volume code. For each impeller, pressure and relative velocity distributions are presented and analyzed. The flow patterns in the blade passages are monitored, and the mechanisms that dominate the flow field in the different regions of the impeller geometry are discussed.
Hydropower is the most widely used renewable energy source worldwide, contributing almost with 18... more Hydropower is the most widely used renewable energy source worldwide, contributing almost with 18.5% to the fulfillment of the planet electricity generation. However, most locations in Europe appropriate for the installation of large hydro power stations have already been exploited. Furthermore, there is a significant local communities’ opposition towards new large power stations; hence, small hydro power stations remain one
The electricity generation in the Aegean Archipelago islands is determined by increased electrici... more The electricity generation in the Aegean Archipelago islands is determined by increased electricity production costs due to its dependency on imported oil. On the other hand, these islands are favored with considerable wind potential that encourages the realization of wind energy projects. However, due to the stochastic behavior of wind, the respective electricity generation cannot always provide firm capacity to an autonomous electrical power system. To encounter the existing situation, system operators are obliged to limit wind power penetration, this resulting in significant wind energy curtailments. In an attempt to face these problems, the idea of an integrated water pumping energy storage strategy is examined. To investigate the optimum size of a Pumped Hydro Storage (PHS) system, an integrated computational algorithm is developed, based on a well-established sizing procedure methodology that also considers boundary conditions. The numerical code is prepared in "Visual-Basic" environment and a user-friendly computational tool is created, presenting among others the hourly operational status as well as the annual energy yield of the plant. Finally, an application of the proposed numerical code is presented, based on real data like the long-term renewable energy curtailments of existing wind parks (operating in a representative North Aegean island) and the operational characteristics of the PHS system components. By applying the proposed numerical code, the operational parameters of a PHS system may be investigated in detail, while based on the application results obtained, the ability of the wind energy to remarkably contribute in the remote islands' energy balance is illustrated.
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Papers by John Kaldellis