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2 pages, 168 KiB

Open AccessEditorial

Energy and Exergy Analysis of Renewable Energy Conversion Systems

by Audrius Bagdanavicius

Energies 2022, 15(15), 5528; https://doi.org/10.3390/en15155528 - 29 Jul 2022

Viewed by 1010

Abstract

Rising climate change issues are prompting engineers and scientists to focus more on improving renewable energy conversion systems [...] Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

Research

Jump to: Editorial

17 pages, 2095 KiB

Open AccessArticle

Thermodynamic Analysis of Waste Vegetable Oil Conversion to Biodiesel with Solar Energy

by José A. León, Gisela Montero, Marcos A. Coronado, José R. Ayala, Daniela G. Montes, Laura J. Pérez, Lisandra Quintana and Jesús M. Armenta

Energies 2022, 15(5), 1834; https://doi.org/10.3390/en15051834 - 2 Mar 2022

Cited by 2 | Viewed by 1680

Abstract

Exergy and energy analyses of two biodiesel production processes that integrate solar energy as the main energy source were developed to determine the process with the higher efficiency from an energy and exergy approach. The biodiesel production processes were simulated in ASPEN PLUS [...] Read more.

Exergy and energy analyses of two biodiesel production processes that integrate solar energy as the main energy source were developed to determine the process with the higher efficiency from an energy and exergy approach. The biodiesel production processes were simulated in ASPEN PLUS^®, and the solar energy supply was studied in TRNSYS^®, using EXCEL^® simultaneously for the exergetic analysis. The solar thermal energy collection system can supply 81% of the energy required by the alkali process in the Flash separation equipment. For the supercritical process, solar thermal energy can supply 74.5% of the energy in the preheating and separation stages. The energy efficiency of the supercritical process is higher; nevertheless, the exergetic efficiency of the alkaline process is higher than the supercritical one. Solar collection systems contribute from 85% to 93% of the exergy destroyed by the global process for both cases. The alkaline biodiesel production process has the highest advantages when using solar energy as the main source of energy, compared to a process in supercritical conditions that presents greater irreversibilities and requires more infrastructure to collect the solar resource. However, using solar energy as the foremost energy source offers an alternative to fossil fuels, and it provides an environmental benefit concurrently with the use of biodiesel. Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

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25 pages, 1550 KiB

Open AccessFeature PaperArticle

A Class of Reduced-Order Regenerator Models

by Raphael Paul and Karl Heinz Hoffmann

Energies 2021, 14(21), 7295; https://doi.org/10.3390/en14217295 - 4 Nov 2021

Cited by 5 | Viewed by 1391

Abstract

We present a novel class of reduced-order regenerator models that is based on Endoreversible Thermodynamics. The models rest upon the idea of an internally reversible (perfect) regenerator, even though they are not limited to the reversible description. In these models, the temperatures of [...] Read more.

We present a novel class of reduced-order regenerator models that is based on Endoreversible Thermodynamics. The models rest upon the idea of an internally reversible (perfect) regenerator, even though they are not limited to the reversible description. In these models, the temperatures of the working gas that alternately streams out on the regenerator’s hot and cold sides are defined as functions of the state of the regenerator matrix. The matrix is assumed to feature a linear spatial temperature distribution. Thus, the matrix has only two degrees of freedom that can, for example, be identified with its energy and entropy content. The dynamics of the regenerator is correspondingly expressed in terms of balance equations for energy and entropy. Internal irreversibilities of the regenerator can be accounted for by introducing source terms to the entropy balance equation. Compared to continuum or nodal regenerator models, the number of degrees of freedom and numerical effort are reduced considerably. As will be shown, instead of the obvious choice of variables energy and entropy, if convenient, a different pair of variables can be used to specify the state of the regenerator matrix and formulate the regenerator’s dynamics. In total, we will discuss three variants of this endoreversible regenerator model, which we will refer to as

ES

,

EE

, and

EEn

-regenerator models. Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

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15 pages, 3662 KiB

Open AccessArticle

Comparison of Two Energy Management System Strategies for Real-Time Operation of Isolated Hybrid Microgrids

by Luis Santiago Azuara-Grande, Santiago Arnaltes, Jaime Alonso-Martinez and Jose Luis Rodriguez-Amenedo

Energies 2021, 14(20), 6770; https://doi.org/10.3390/en14206770 - 17 Oct 2021

Cited by 8 | Viewed by 2211

Abstract

The propagation of hybrid power systems (solar–diesel–battery) has led to the development of new energy management system (EMS) strategies for the effective management of all power generation technologies related to hybrid microgrids. This paper proposes two novel EMS strategies for isolated hybrid microgrids, [...] Read more.

The propagation of hybrid power systems (solar–diesel–battery) has led to the development of new energy management system (EMS) strategies for the effective management of all power generation technologies related to hybrid microgrids. This paper proposes two novel EMS strategies for isolated hybrid microgrids, highlighting their strengths and weaknesses using simulations. The proposed strategies are different from the EMS strategies reported thus far in the literature because the former enable the real-time operation of the hybrid microgrid, which always guarantees the correct operation of a microgrid. The priority EMS strategy works by assigning a priority order, while the optimal EMS strategy is based on an optimization criterion, which is set as the minimum marginal cost in this case. The results have been obtained using MATLAB/Simulink to verify and compare the effectiveness of the proposed strategies, through a dynamic microgrid model to simulate the conditions of a real-time operation. The differences in the EMS strategies as well as their individual strengths and weaknesses, are presented and discussed. The results show that the proposed EMS strategies can manage the system operation under different scenarios and help power system operator obtain the optimal operation schemes of the microgrid. Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

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23 pages, 8664 KiB

Open AccessArticle

Design and Realization of a Hybrid Excited Flux Switching Vernier Machine for Renewable Energy Conversion

by Haidar Diab, Yacine Amara, Sami Hlioui and Johannes J. H. Paulides

Energies 2021, 14(19), 6060; https://doi.org/10.3390/en14196060 - 23 Sep 2021

Cited by 5 | Viewed by 2094

Abstract

This paper presents the design of a hybrid excited flux switching Vernier machine. This machine is designed to serve in renewable energy conversion applications, such as a wind turbine generator, or tidal turbine generator. After introducing this original structure, a design based on [...] Read more.

This paper presents the design of a hybrid excited flux switching Vernier machine. This machine is designed to serve in renewable energy conversion applications, such as a wind turbine generator, or tidal turbine generator. After introducing this original structure, a design based on finite element models is conducted. The specifications correspond to relatively low power direct drive wind or tidal turbine applications. The rated power is set to 10 kW, with a rated speed of 300 rpm. Mainly the electromagnetic design is presented. Aspects related to the realization of a prototype are also presented, and an experimental study is included. Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

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13 pages, 3147 KiB

Open AccessArticle

Optimization of Mono-Crystalline Silicon Solar Cell Devices Using PC1D Simulation

by Gokul Sidarth Thirunavukkarasu, Mehdi Seyedmahmoudian, Jaideep Chandran, Alex Stojcevski, Maruthamuthu Subramanian, Raj Marnadu, S. Alfaify and Mohd. Shkir

Energies 2021, 14(16), 4986; https://doi.org/10.3390/en14164986 - 13 Aug 2021

Cited by 16 | Viewed by 3617

Abstract

Expeditious urbanization and rapid industrialization have significantly influenced the rise of energy demand globally in the past two decades. Solar energy is considered a vital energy source that addresses this demand in a cost-effective and environmentally friendly manner. Improving solar cell efficiency is [...] Read more.

Expeditious urbanization and rapid industrialization have significantly influenced the rise of energy demand globally in the past two decades. Solar energy is considered a vital energy source that addresses this demand in a cost-effective and environmentally friendly manner. Improving solar cell efficiency is considered a prerequisite to reinforcing silicon solar cells’ growth in the energy market. In this study, the influence of various parameters like the thickness of the absorber or wafer, doping concentration, bulk resistivity, lifetime, and doping levels of the emitter and back surface field, along with the surface recombination velocity (front and back) on solar cell efficiency was investigated using PC1D simulation software. Inferences from the results indicated that the bulk resistivity of 1

Ω

·cm; bulk lifetime of 2 ms; emitter (

n^{+}

) doping concentration of

1 \times 10^{20}

cm

^{- 3}

and shallow back surface field doping concentration of

1 \times 10^{18}

cm

^{- 3}

; surface recombination velocity maintained in the range of

10^{2}

and

10^{3}

cm/s obtained a solar cell efficiency of 19%. The Simulation study presented in this article allows faster, simpler, and easier impact analysis of the design considerations on the Si solar cell wafer fabrications with increased performance. Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

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21 pages, 5025 KiB

Open AccessArticle

Advanced Exergy Analysis of Waste-Based District Heating Options through Case Studies

by Huseyin Gunhan Ozcan, Arif Hepbasli, Aysegul Abusoglu and Amjad Anvari-Moghaddam

Energies 2021, 14(16), 4766; https://doi.org/10.3390/en14164766 - 5 Aug 2021

Cited by 4 | Viewed by 1996

Abstract

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their [...] Read more.

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their significant potential and the experience accumulated over many years. The work described here deals with the conventional and advanced exergy performance assessments of the district heating system, using four different waste heat sources by the exhaust gas potentials of the selected plants (municipal solid waste cogeneration, thermal power, wastewater treatment, and cement production), with the real-time data group based on numerical investigations. The simulated results based on conventional exergy analysis revealed that the priority should be given to heat exchanger (HE)-I, with exergy efficiency values from 0.39 to 0.58, followed by HE-II and the pump with those from 0.48 to 0.78 and from 0.81 to 0.82, respectively. On the other hand, the simulated results based on advanced exergy analysis indicated that the exergy destruction was mostly avoidable for the pump (78.32–78.56%) and mostly unavoidable for the heat exchangers (66.61–97.13%). Meanwhile, the exergy destruction was determined to be mainly originated from the component itself (endogenous), for the pump (97.50–99.45%) and heat exchangers (69.80–91.97%). When the real-time implementation was considered, the functional exergy efficiency of the entire system was obtained to be linearly and inversely proportional to the pipeline length and the average ambient temperature, respectively. Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

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30 pages, 8680 KiB

Open AccessFeature PaperArticle

Coordinating Control of an Offshore LVDC Microgrid Based Renewable Energy Resources for Voltage Regulation and Circulating Current Minimization

by Walid Nassar, Olimpo Anaya-Lara and Khaled Ahmed

Energies 2021, 14(12), 3384; https://doi.org/10.3390/en14123384 - 8 Jun 2021

Cited by 7 | Viewed by 1549

Abstract

Multi-Use Platform (MUP) is a new topic addressed, extensively, under the EU funded projects that aim to exploit oceans in a sustainable way in order to reduce the costs of marine energy and to extract seafood. MUP’s electrical grid experiences many challenges, being [...] Read more.

Multi-Use Platform (MUP) is a new topic addressed, extensively, under the EU funded projects that aim to exploit oceans in a sustainable way in order to reduce the costs of marine energy and to extract seafood. MUP’s electrical grid experiences many challenges, being offshore. One of these challenges is that only Alternating Current (AC) systems are considered which are inefficient, expensive and require bulky components. Considering the advantages of Direct Current (DC) systems, this paper aims to study the feasibility of using the DC system to improve the electrical infrastructure of the MUP’s grid. Floating energy unit comprising tidal, wind and solar energy resources is considered as a base unit for the MUP’s grid. The paper proposes a new distributed controller for grid voltage regulation and minimizing circulating current among parallel-connected floating energy units in an offshore Low Voltage Direct Current (LVDC) microgrid. A mathematical model is derived for n-parallel floating energy units with the proposed controller. Additionally, stability analysis for the overall model of a single floating energy unit is also presented. The analysis and simulation of the proposed DC system demonstrate that the system is stable and fault-rejected at different operating conditions. Full article

(This article belongs to the Special Issue Energy and Exergy Analysis of Renewable Energy Conversion Systems)

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