The Experts below are selected from a list of 32661 Experts worldwide ranked by ideXlab platform
J K Kaldellis - One of the best experts on this subject based on the ideXlab platform.
-
optimum sizing of photovoltaic energy Storage systems for autonomous small islands
International Journal of Electrical Power & Energy Systems, 2010Co-Authors: J K Kaldellis, Dimitrios Zafirakis, E KondiliAbstract:The electrification of autonomous electrical networks is in most cases described by low quality of electricity available at very high production cost. Furthermore, autonomous electrical networks are subject to strict constraints posing serious limitations on the absorption of RES-based electricity generation. To by-pass these constraints and also secure a more sustainable electricity supply status, the concept of combining photovoltaic power stations and energy Storage systems comprises a promising solution for small scaled autonomous electrical networks, increasing the reliability of the local network as well. In this context, the present study is devoted to develop a complete methodology, able to define the dimensions of an autonomous electricity generation system based on the maximum available solar potential exploitation at minimum electricity generation cost. In addition special emphasis is given in order to select the most cost-efficient energy Storage Configuration available. According to the calculation results obtained, one may clearly state that an optimum sizing combination of a PV generator along with an appropriate energy Storage system may significantly contribute on reducing the electricity generation cost in several island electrical systems, providing also abundant and high quality electricity without the environmental and macroeconomic impacts of the oil-based thermal power stations.
-
cost benefit analysis of a photovoltaic energy Storage electrification solution for remote islands
Renewable Energy, 2009Co-Authors: J K Kaldellis, Dimitrios Zafirakis, El Kaldelli, K A KavadiasAbstract:Abstract A large number of various sized islands are spread throughout the south-east Mediterranean Sea. Most of these small islands face serious infrastructure problems, like the insufficient power supply and the low quality of electricity available at very high production cost. In an attempt to improve the life quality of all these isolated communities, an investigation concerning the financial viability of an integrated electrification solution based on one or more photovoltaic generators and an appropriate energy Storage system is described. The main target of a similar solution is to maximize the contribution of the photovoltaic generator and minimize the life-cycle electricity generation cost of the remote island networks investigated. In addition, special emphasis is given in order to select the most cost-efficient energy Storage Configuration available. According to the results obtained for high and medium–high solar potential regions, the proposed Configuration is found to be more cost-effective than the existing thermal power stations. Several side benefits like the improved electrical network reliability and the minimization of the environmental and macroeconomic impacts resulting from the replacement of the imported oil should also be considered.
-
integrated electrification solution for autonomous electrical networks on the basis of res and energy Storage Configurations
Energy Conversion and Management, 2008Co-Authors: J K KaldellisAbstract:Most medium and small islands of the Aegean Archipelagos face serious infrastructure problems, strongly related with the limited electrical energy available at extremely high cost. On the other hand, the area is characterized by very high wind speeds and abundant solar energy, thus the exploitation of the available renewable energy sources (RES) may significantly contribute to the fulfillment of the local societies energy demand at minimum environmental and macroeconomic cost. However, the stochastic availability of wind energy and the variable availability of solar energy, the daily and seasonal electricity demand fluctuations, as well as the limited local electrical network capacity result in serious restrictions concerning the maximum renewable power penetration. In this context, the present paper investigates the possibility of creating a combined electricity generation facility based on the exploitation of wind or/and solar potential of an area as well as on the utilization of an appropriate energy Storage Configuration in order to replace the existing thermal power stations with rational investment requirements. For this purpose, the major parameters of the proposed integrated Configuration are firstly calculated and its financial viability is accordingly analyzed. One of the main targets of the proposed solution is to maximize the RES exploitation of the area at a minimum electricity generation cost, while special emphasis is given in order to select the most cost-efficient energy Storage device available. According to the results obtained the proposed solution is not only financially attractive but also improves the quality of the electricity offered to the local communities, substituting the expensive and heavily polluting existing thermal power stations.
Qiuwang Wang - One of the best experts on this subject based on the ideXlab platform.
-
thermal performance analysis of thermocline combined sensible latent heat Storage system using cascaded layered pcm designs for medium temperature applications
Renewable Energy, 2020Co-Authors: Naseer Ahmed, K E Elfeky, Qiuwang WangAbstract:One tank type thermocline thermal energy Storage (TES) concept is considered as a possible cost optimized solution for the medium temperature industrial applications, e.g., chemical processing, beverages industry etc. However, one of the drawbacks of this TES Configuration is higher thermocline degradation at the end of discharging cycles and overall decrease in performance. In current work a new type of combined sensible-latent heat Configuration is introduced to counter these issues. The concept of the proposed thermal Storage Configuration is to use structured sensible heat cheap material with the space between them occupied by encapsulated phase change material (PCM) capsules, forming cascaded layered packed bed along the tank height and the heat transfer fluid flows between them. A comprehensive unsteady numerical model is formulated based on two-phase Schumann model equations to evaluate performance of the each proposed prototypes. The numerical simulations are performed to investigate the effect of combined sensible rod structure and multi-layered PCMs designs on thermocline temperature profiles, exergy outputs, total thermal energy Storage, efficiency in the use of total Storage capacity, utilization ratio and the proportion of PCM effectively changing phase. The comparative analysis is performed for four different Configurations, i.e., single layered sensible rod with PCM (SLSPCM) arrangement and the three cascaded layered sensible rod with PCM (CLSPCM) arrangements. The overall results show that the TES with a volume fraction arrangement of (40%-20%–40%) is performance wise the best Configuration followed by (25%-50%–25%) and (10%-80%–10%), respectively. And SLSPCM is the lowest in the row. The analysis presented in the current study shows that the use of multistage PCMs having suitable combination of layer thickness and fusion temperature together with the inclusion of cheaper structured filler material, offer an efficient and cost effective TES alternative.
-
thermal and economic evaluation of thermocline combined sensible latent heat thermal energy Storage system for medium temperature applications
Energy Conversion and Management, 2019Co-Authors: Naseer Ahmed, K E Elfeky, Qiuwang WangAbstract:Abstract In the current work a new thermocline combined sensible-latent heat thermal energy Storage Configuration is proposed as an alternative to the currently used thermal Storage systems; containing solid rod structures of cheap naturally occurring material with phase change material capsules impregnated between the rods. An energy balance method coupled with an enthalpy based technique are used to develop a comprehensive transient numerical model. The numerical simulations are performed to compare the performance and the cost of the three types of thermal energy Storage systems. The three thermal energy Storage systems are; sensible rod structure, encapsulated phase change material and combined sensible-latent heat. The influence of different evaluation indexes on economic feasibility and the performance of thermal energy Storage such as capital cost, capacity cost per kWh, axial temperature distribution, pumping work, thermocline degradation, effective discharging time and effective discharging efficiency; are analyzed. The results show that effective discharging efficiency and capacity costs for encapsulated phase change material, combined sensible-latent heat, sensible rod structure are 95%, 87%, 76% and $42/kWh, $37/kWh, $35/kWh, respectively. Moreover, the hybrid Configuration exhibits a Storage capacity of 78.5 kWh/m3, which is 26% higher than sensible rod structure and 22% lower than encapsulated phase change material Configuration. The results of the comparative study indicate that the combined sensible-latent heat TES system seems to be a more viable option among the considered Configurations due to its optimized performance and comparatively low cost. Also due to the reasons that thermal ratcheting of the Storage tank is avoided and it provides stable fluid outlet temperature.
Naseer Ahmed - One of the best experts on this subject based on the ideXlab platform.
-
thermal performance analysis of thermocline combined sensible latent heat Storage system using cascaded layered pcm designs for medium temperature applications
Renewable Energy, 2020Co-Authors: Naseer Ahmed, K E Elfeky, Qiuwang WangAbstract:One tank type thermocline thermal energy Storage (TES) concept is considered as a possible cost optimized solution for the medium temperature industrial applications, e.g., chemical processing, beverages industry etc. However, one of the drawbacks of this TES Configuration is higher thermocline degradation at the end of discharging cycles and overall decrease in performance. In current work a new type of combined sensible-latent heat Configuration is introduced to counter these issues. The concept of the proposed thermal Storage Configuration is to use structured sensible heat cheap material with the space between them occupied by encapsulated phase change material (PCM) capsules, forming cascaded layered packed bed along the tank height and the heat transfer fluid flows between them. A comprehensive unsteady numerical model is formulated based on two-phase Schumann model equations to evaluate performance of the each proposed prototypes. The numerical simulations are performed to investigate the effect of combined sensible rod structure and multi-layered PCMs designs on thermocline temperature profiles, exergy outputs, total thermal energy Storage, efficiency in the use of total Storage capacity, utilization ratio and the proportion of PCM effectively changing phase. The comparative analysis is performed for four different Configurations, i.e., single layered sensible rod with PCM (SLSPCM) arrangement and the three cascaded layered sensible rod with PCM (CLSPCM) arrangements. The overall results show that the TES with a volume fraction arrangement of (40%-20%–40%) is performance wise the best Configuration followed by (25%-50%–25%) and (10%-80%–10%), respectively. And SLSPCM is the lowest in the row. The analysis presented in the current study shows that the use of multistage PCMs having suitable combination of layer thickness and fusion temperature together with the inclusion of cheaper structured filler material, offer an efficient and cost effective TES alternative.
-
thermal and economic evaluation of thermocline combined sensible latent heat thermal energy Storage system for medium temperature applications
Energy Conversion and Management, 2019Co-Authors: Naseer Ahmed, K E Elfeky, Qiuwang WangAbstract:Abstract In the current work a new thermocline combined sensible-latent heat thermal energy Storage Configuration is proposed as an alternative to the currently used thermal Storage systems; containing solid rod structures of cheap naturally occurring material with phase change material capsules impregnated between the rods. An energy balance method coupled with an enthalpy based technique are used to develop a comprehensive transient numerical model. The numerical simulations are performed to compare the performance and the cost of the three types of thermal energy Storage systems. The three thermal energy Storage systems are; sensible rod structure, encapsulated phase change material and combined sensible-latent heat. The influence of different evaluation indexes on economic feasibility and the performance of thermal energy Storage such as capital cost, capacity cost per kWh, axial temperature distribution, pumping work, thermocline degradation, effective discharging time and effective discharging efficiency; are analyzed. The results show that effective discharging efficiency and capacity costs for encapsulated phase change material, combined sensible-latent heat, sensible rod structure are 95%, 87%, 76% and $42/kWh, $37/kWh, $35/kWh, respectively. Moreover, the hybrid Configuration exhibits a Storage capacity of 78.5 kWh/m3, which is 26% higher than sensible rod structure and 22% lower than encapsulated phase change material Configuration. The results of the comparative study indicate that the combined sensible-latent heat TES system seems to be a more viable option among the considered Configurations due to its optimized performance and comparatively low cost. Also due to the reasons that thermal ratcheting of the Storage tank is avoided and it provides stable fluid outlet temperature.
Chang Liu - One of the best experts on this subject based on the ideXlab platform.
-
optimal planning of a 100 renewable energy island supply system based on the integration of a concentrating solar power plant and desalination units
International Journal of Electrical Power & Energy Systems, 2020Co-Authors: Zhixun Wang, Xiangning Lin, Ning Tong, Shitong Sun, Chang LiuAbstract:Abstract Environmental-unfriendly power supply mode and freshwater shortage are two main problems for isolated islands. A 100% renewable energy supply system equipped with local desalination units is an effective solution to the above problems. It can save fuel supplies and eliminate pollutant emissions. Firstly, a 100% renewable energy supply system based on wind turbines and the integration of a concentrating solar power (CSP) plant and desalination units is proposed in this paper. The flexible schedulability of CSP plants is utilized to complement to wind power generation, and the thermal Storage system reduces the battery energy Storage Configuration for islands. Different from the conventional method of seeking the minimum levelized cost of CSP from limited capacity combinations, an optimal planning model is established to achieve the minimum overall costs of the 100% renewable energy system. In addition, the adjustable output characteristic of CSP is also considered as the decision variables to optimize the operation of the microgrid. The model is linearized to a mixed integer linear programming problem. Simulation results show that the proposed supply system improves the efficiency of renewable energy utilization and capacity factors of generation units; the peak load demand is cut down and the capacity Configuration of generation units is also reduced. The comparison with other state-of-art systems shows that the cost-effectiveness of the proposed system is better in areas with abundant renewable energy resources and high fuel costs.
-
system level performance optimization of molten salt packed bed thermal energy Storage for concentrating solar power
Applied Energy, 2018Co-Authors: Bingchen Zhao, Chang Liu, Maosong Cheng, Zhimin DaiAbstract:Abstract Molten-salt packed-bed thermal energy Storage using thermocline technology is more cost-competitive than the conventional two-tank thermal energy Storage, due to its integrated design and the employment of a low-cost packed-bed. However, such a Storage Configuration suffers the main drawback of a low capacity factor when applied to concentrating solar power because of the adoption of conservative cut-off temperatures. The present work evaluates the feasibility of taking less conservative cut-off temperatures to improve the utilization of the packed-bed thermal energy Storage from the perspectives of a system-level operation and Storage economy. The investigations are carried out on two levels. The first-level investigation reveals the effects of both the charging and discharging cut-off temperature on the thermal performance of the packed-bed thermal energy Storage under ideal operating conditions. Three typical packed-bed Configurations are involved. The results show that the capacity factor of the packed-bed thermal energy Storage increases as the charging cut-off temperature increases and the discharging cut-off temperature decreases, especially for the Configurations using latent-heat when the adopted cut-off temperatures jump over the phase change points of the encapsulated phase change materials. The second-level investigation discusses the impacts of different levels of deep charges (using high charging cut-off temperatures) on the scale design of the packed-bed thermal energy Storage, the daily operation of the low temperature molten-salt pump (LT-pump) and the central receiver of a 100 MWe conventional concentrating solar power tower plant. The results indicate that a deeper charge operation is always accompanied with a smaller required packed-bed size as well as a higher required delivery capacity and higher pressure head of the LT-pump and that it always results in a larger daily pumping consumption, a higher peak inlet temperature ramping rate and a higher receiver pressure drop. The maximum allowable charging cut-off temperature is identified to be 500 °C for each packed-bed Configuration, according to the operating limitations on the pump and receiver. Moreover, a cost analysis is carried out to obtain the optimum charging cut-off temperature for each packed-bed Configuration. The obtained results show that performing deep charges with the cost-optimized charging cut-off temperatures can effectively improve the cost competitiveness of the molten-salt packed-bed TES integrated into concentrating solar power plants.
Alberto Benato - One of the best experts on this subject based on the ideXlab platform.
-
energy and cost analysis of an air cycle used as prime mover of a thermal electricity Storage
Journal of energy storage, 2018Co-Authors: Alberto Benato, Anna StoppatoAbstract:Abstract The increment of greenhouse gas emissions from human activities have forced the world authorities to ratify stringent environmental protection measurements devoted to the reduction of primary energy consumption and to the spread of Renewable Energy Sources (RES). To reach the fixed targets, governments have established subsidies especially to support the electricity generation from RES like wind and solar. However, the large penetration of variable and intermittent RES is stressing the need of large-scale energy Storage able to stabilize the electric grids. But, available large-scale energy Storage technologies like Pumped Hydro, Compressed Air Energy Storage or Flow Batteries, suffer of geographical constrains, require fossil fuel streams or are characterized by low cycle life. For this reason, in the present paper, a new Thermal Electricity Storage Configuration based on the Air Bottoming Cycle (ABC) concept is proposed and tested. The off-peak power is firstly converted into thermal energy using an electric heater and, then, stored in a high temperature sensible heat Storage. When the power demand is high, using a modified ABC the thermal energy is converted back into electricity. Using the plant mathematical model, an energy and a cost analyses are carried out to estimate the performance and the system feasibility.
-
performance and cost evaluation of an innovative pumped thermal electricity Storage power system
Energy, 2017Co-Authors: Alberto BenatoAbstract:Abstract Wind and solar energy have a time dependent nature which is their main disadvantage. To overcome this drawback, energy Storage systems need to be set up. High-temperature Pumped Thermal Electricity Storage employing packed bed as Storage medium can be an attractive solution. For this reason, in the present paper, firstly, an in-depth literature review on Pumped Thermal Electricity Storage and on Storage materials is presented with the aim of assessing the current state of the art. Then, a new Pumped Thermal Electricity Storage Configuration is proposed and tested. An electric heater is used to convert electrical energy into thermal energy, a single heat exchanger is installed and air is used as heat transfer fluid. A 1D packed bed model is used to simulate the thermal performance of the hot and cold Storage. In the Storage model also the pressure drop is taken into account. The plant mathematical model is implemented in Matlab environment while the heat transfer fluid and bed material properties are taken from CoolProp and NIST database, respectively. An energy and cost analysis is performed in order to assess the feasibility of the system. Five types of high Storage density material, two bed material shapes and different maximum plant temperature are tested and their influence on the technical and economic characteristics and performance of the plant is assessed.