Energies

Editorial

3 pages, 470 KiB

Open AccessEditorial

Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes

by Giorgio Cau, Mario Petrollese and Vittorio Tola

Energies 2022, 15(3), 1121; https://doi.org/10.3390/en15031121 - 3 Feb 2022

Viewed by 1221

Abstract

This book contains the successful invited submissions [...] Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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Research

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17 pages, 2102 KiB

Open AccessArticle

The Modelling and Experimental Validation of a Cryogenic Packed Bed Regenerator for Liquid Air Energy Storage Applications

by Robert Morgan, Christian Rota, Emily Pike-Wilson, Tim Gardhouse and Cian Quinn

Energies 2020, 13(19), 5155; https://doi.org/10.3390/en13195155 - 3 Oct 2020

Cited by 12 | Viewed by 3064

Abstract

Electrical energy storage will play a key role in the transition to a low carbon energy network. Liquid air energy storage (LAES) is a thermal–mechanical energy storage technology that converts electricity to thermal energy. This energy is stored in three ways: as latent [...] Read more.

Electrical energy storage will play a key role in the transition to a low carbon energy network. Liquid air energy storage (LAES) is a thermal–mechanical energy storage technology that converts electricity to thermal energy. This energy is stored in three ways: as latent heat in a tank of liquid air, as warm sensible heat in a hot tank and as cold sensible heat in a packed bed regenerator (PBR), which is the focus of this paper. A PBR was selected because the temperature range (−196 °C to 10 °C) prohibits storage in liquid media, as most fluids will undergo a phase change over a near 200 °C temperature range. A change of phase in the storage media would result in exergy destruction and loss of efficiency of the LAES device. Gravel was selected as the storage media, as (a) many gravels are compatible with cryogenic temperatures and (b) the low cost of the material if it can be used with minimal pre-treatment. PBRs have been extensively studied and modelled such as the work by Schumann, described by Wilmott and later by White. However, these models have not been applied to and validated for a low temperature store using gravel. In the present research, a comprehensive modelling and experimental program was undertaken to produce a validated model of a low-temperature PBR. This included a study of the low-temperature properties of various candidate gravels, implementation of a modified Schumann model and validation using a laboratory scale packed bed regenerator. Two sizes of gravel at a range of flow rates were tested. Good agreement between the predicted and measured temperature fields in the PBR was achieved when a correlation factor was applied to account for short circuiting of the storage media through flow around the interface between the walls of the regenerator and storage media. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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16 pages, 3197 KiB

Open AccessArticle

Performance Evaluation of a Direct Absorption Collector for Solar Thermal Energy Conversion

by Abdul Sattar, Muhammad Farooq, Muhammad Amjad, Muhammad A. Saeed, Saad Nawaz, M.A. Mujtaba, Saqib Anwar, Ahmed M. El-Sherbeeny, Manzoore Elahi M. Soudagar, Enio P. Bandarra Filho, Qasim Ali, Muhammad Imran and Alberto Pettinau

Energies 2020, 13(18), 4956; https://doi.org/10.3390/en13184956 - 21 Sep 2020

Cited by 27 | Viewed by 3465

Abstract

The solar absorption efficiency of water as a base-fluid can be significantly improved by suspending nanoparticles of various materials in it. This experimental work presents the photo thermal performance of water-based nano-fluids of graphene oxide (GO), zinc oxide (ZnO), copper oxide (CuO), and [...] Read more.

The solar absorption efficiency of water as a base-fluid can be significantly improved by suspending nanoparticles of various materials in it. This experimental work presents the photo thermal performance of water-based nano-fluids of graphene oxide (GO), zinc oxide (ZnO), copper oxide (CuO), and their hybrids under natural solar flux for the first time. Nanofluid samples were prepared by the two-step method and the photothermal performance of these nanofluid samples was conducted under natural solar flux in a particle concentration range from 0.0004 wt % to 0.0012 wt %. The photothermal efficiency of water-based 0.0012 wt % GO nanofluid was 46.6% greater than that of the other nanofluids used. This increased photothermal performance of GO nanofluid was associated with its good stability, high absorptivity, and high thermal conductivity. Thus, pure graphene oxide (GO) based nanofluid is a potential candidate for direct absorption solar collection to be used in different solar thermal energy conversion applications. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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24 pages, 10645 KiB

Open AccessArticle

Comparison between Hydrogen and Syngas Fuels in an Integrated Micro Gas Turbine/Solar Field with Storage

by Maria Cristina Cameretti, Alessandro Cappiello, Roberta De Robbio and Raffaele Tuccillo

Energies 2020, 13(18), 4764; https://doi.org/10.3390/en13184764 - 12 Sep 2020

Cited by 9 | Viewed by 2855

Abstract

In recent years, the use of alternative fuels in thermal engine power plants has gained more and more attention, becoming of paramount importance to overcome the use of fuels from fossil sources and to reduce polluting emissions. The present work deals with the [...] Read more.

In recent years, the use of alternative fuels in thermal engine power plants has gained more and more attention, becoming of paramount importance to overcome the use of fuels from fossil sources and to reduce polluting emissions. The present work deals with the analysis of the response to two different gas fuels—i.e., hydrogen and a syngas from agriculture product—of a 30 kW micro gas turbine integrated with a solar field. The solar field included a thermal storage system to partially cover loading requests during night hours, reducing fuel demand. Additionally, a Heat Recovery Unit was included in the plant considered and the whole plant was simulated by Thermoflex^® code. Thermodynamics analysis was performed on hour-to-hour basis, for a given day as well as for 12 months; subsequently, an evaluation of cogeneration efficiency as well as energy saving was made. The results are compared against plant performance achieved with conventional natural gas fueling. After analyzing the performance of the plant through a thermodynamic analysis, the study was complemented with CFD simulations of the combustor, to evaluate the combustion development and pollutant emissions formation, particularly of NO_x, with the two fuels considered using Ansys-Fluent code, and a comparison was made. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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22 pages, 2492 KiB

Open AccessArticle

A Definitive Model of a Small-Scale Concentrated Solar Power Hybrid Plant Using Air as Heat Transfer Fluid with a Thermal Storage Section and ORC Plants for Energy Recovery

by Andrea Cinocca, Marco Di Bartolomeo, Roberto Cipollone and Roberto Carapellucci

Energies 2020, 13(18), 4741; https://doi.org/10.3390/en13184741 - 11 Sep 2020

Cited by 7 | Viewed by 2307

Abstract

The aim of this work was to propose a small-scale Concentrated Solar Power plant using conventional technologies, in order to improve their flexibility and performances, and reinforce their competitiveness compared to traditional systems. Additionally, this study analyzed the possibility of providing continuity of [...] Read more.

The aim of this work was to propose a small-scale Concentrated Solar Power plant using conventional technologies, in order to improve their flexibility and performances, and reinforce their competitiveness compared to traditional systems. Additionally, this study analyzed the possibility of providing continuity of energy production through an optimized hybrid system, which considered thermal energy storage from a gaseous Heat Transfer Fluid, air. It also considered the possibility of recovering part of the energy of the thermodynamic cycle through an Organic Rankine Cycle system with appropriate dimensions. The final outcomes were a 170 kW CSP plant with about 805 MWh of annual electricity production with a global solar capacity of 32.5%, about 900 kWh of thermal storage daily capacity, and an ORC recovery section of 54.2 kW with a specific production of 260 MWh/y. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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26 pages, 7094 KiB

Open AccessArticle

Optimized Layouts of Borehole Thermal Energy Storage Systems in 4th Generation Grids

by Hoofar Hemmatabady, Julian Formhals, Bastian Welsch, Daniel Otto Schulte and Ingo Sass

Energies 2020, 13(17), 4405; https://doi.org/10.3390/en13174405 - 26 Aug 2020

Cited by 7 | Viewed by 3074

Abstract

Borehole thermal energy storage (BTES) systems are a viable option to meet the increasing cooling demand and to increase the sustainability of low-temperature district heating and cooling (DHC) grids. They are able to store the rejected heat of cooling cycles on a seasonal [...] Read more.

Borehole thermal energy storage (BTES) systems are a viable option to meet the increasing cooling demand and to increase the sustainability of low-temperature district heating and cooling (DHC) grids. They are able to store the rejected heat of cooling cycles on a seasonal basis and deliver this heat during the heating season. However, their efficient practical implementation requires a thorough analysis from technical, economic and environmental points of view. In this comparative study, a dynamic exergoeconomic assessment is adopted to evaluate various options for integrating such a storage system into 4th generation DHC grids in heating dominated regions. For this purpose, different layouts are modeled and parameterized. Multi-objective optimization is conducted, varying the most important design variables in order to maximize exergetic efficiency and to minimize levelized cost of energy (LCOE). A comparison of the optimal designs of the different layouts reveals that passive cooling together with maximizing the heating temperature shift, accomplished by a heat pump, lead to optimal designs. Component-wise exergy and cost analysis of the most efficient designs highlights that heat pumps are responsible for the highest share in inefficiency while the installation of BTES has a high impact in the LCOE. BTES and buffer storage tanks have the lowest exergy destruction for all layouts and increasing the BTES volume results in more efficient DHC grids. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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19 pages, 2245 KiB

Open AccessArticle

Application of Phase Change Material-Based Thermal Capacitor in Double Tube Heat Exchanger—A Numerical Investigation

by Matthew Fong, Jundika Kurnia and Agus P. Sasmito

Energies 2020, 13(17), 4327; https://doi.org/10.3390/en13174327 - 20 Aug 2020

Cited by 3 | Viewed by 2748

Abstract

In many heat transfer related applications, there is a need for a stable, constant supply temperature. As a result, the integration of intermittent renewable sources of heat into these processes can prove to be challenging, requiring special temperature smoothing devices or strategies. This [...] Read more.

In many heat transfer related applications, there is a need for a stable, constant supply temperature. As a result, the integration of intermittent renewable sources of heat into these processes can prove to be challenging, requiring special temperature smoothing devices or strategies. This study focuses on the application of phase change materials integrated into a double tube heat exchanger as a possible thermal smoothing device. The objective of this study is to evaluate the ability of the exchanger to smoothen out temperature variations within the cold stream outlet while the hot stream is subject to oscillating inlet conditions. A computational fluid dynamics approach is used where a numerical model is developed, validated and then used to model the conjugate heat transfer within the heat exchanger. Four organic phase change materials (PCM) with different phase change temperatures were selected for investigation (myristic, octadecane, eicosane, and wax) to study the relationship between melting temperature and stabilization performance. A parametric study was then conducted by varying the Reynolds number of the flow as well as temperature oscillation period and amplitude to study the sensitivity of the system. The results confirm the potential of a phase change material-based thermal capacitor at dampening oscillations across the heat exchanger. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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16 pages, 6437 KiB

Open AccessArticle

Fuzzy Logic Energy Management Strategy of a Multiple Latent Heat Thermal Storage in a Small-Scale Concentrated Solar Power Plant

by Roberto Tascioni, Alessia Arteconi, Luca Del Zotto and Luca Cioccolanti

Energies 2020, 13(11), 2733; https://doi.org/10.3390/en13112733 - 29 May 2020

Cited by 16 | Viewed by 2545

Abstract

Latent heat thermal energy storage (LHTES) systems allow us to effectively store and release the collected thermal energy from solar thermodynamic plants; however, room for improvements exists to increase their efficiency when in operation. For this reason, in this work, a smart management [...] Read more.

Latent heat thermal energy storage (LHTES) systems allow us to effectively store and release the collected thermal energy from solar thermodynamic plants; however, room for improvements exists to increase their efficiency when in operation. For this reason, in this work, a smart management strategy of an innovative LHTES in a micro-scale concentrated solar combined heat and power plant is proposed and numerically investigated. The novel thermal storage system, as designed and built by the partners within the EU funded Innova MicroSolar project, is subdivided into six modules and consists of 3.8 tons of nitrate solar salt kNO₃/NaNO₃, whose melting temperature is in the range 216 ÷ 223 °C. In this study, the partitioning of the storage system on the performance of the integrated plant is evaluated by applying a smart energy management strategy based on a fuzzy logic approach. Compared to the single thermal energy storage (TES) configuration, the proposed strategy allows a reduction in storage thermal losses and improving of the plant’s overall efficiency especially in periods with limited solar irradiance. The yearly dynamic simulations carried out show that the electricity produced by the combined heat and power plant is increased by about 5%, while the defocus thermal losses in the solar plant are reduced by 30%. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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15 pages, 3532 KiB

Open AccessArticle

Numerical Investigation on a Packed-Bed LHTES System Integrated into a Micro Electrical and Thermal Grid

by Vittorio Tola, Simone Arena, Mario Cascetta and Giorgio Cau

Energies 2020, 13(8), 2018; https://doi.org/10.3390/en13082018 - 18 Apr 2020

Cited by 5 | Viewed by 2380

Abstract

Currently, energy storage systems are considered a key solution when mismatch occurs between energy supply and demand, allowing a more efficient energy deployment and use. The present paper is focused on the study of a latent heat thermal energy storage (LHTES) system based [...] Read more.

Currently, energy storage systems are considered a key solution when mismatch occurs between energy supply and demand, allowing a more efficient energy deployment and use. The present paper is focused on the study of a latent heat thermal energy storage (LHTES) system based on a packed bed of encapsulated phase change material (PCM) of spherical shape, conceived as an auxiliary component of a micro-grid to be built in a Research Center located in southwestern Sardinia (Italy). The main purpose of this work was to perform numerical simulations for predicting the performance of the TES system, designed to store the surplus thermal energy produced during the weekend by a heat pump fed by a photovoltaic (PV) plant. The stored energy would then be utilized during the weekdays to integrate the air-conditioning system supply. The numerical simulations were based on a one-dimensional (1-D) two-equation transient model, able to return the thermocline profile of the water and the PCM separately. The behavior of the LHTES device during charge and discharge phases was reproduced, as well as during the standby periods. Finally, two characteristic indexes of the PV system were evaluated, to investigate the effect of TES on grid interchanges, self-consumption, and self-sufficiency. Full article

(This article belongs to the Special Issue Modeling, Optimization and Testing of Thermal Energy Storage Systems and Their Integration in Energy Conversion Processes)

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