Sustainability

Research

15 pages, 3745 KiB

Open AccessArticle

The Direct Reduction of Iron Ore with Hydrogen

by Shuo Li, Huili Zhang, Jiapei Nie, Raf Dewil, Jan Baeyens and Yimin Deng

Sustainability 2021, 13(16), 8866; https://doi.org/10.3390/su13168866 - 8 Aug 2021

Cited by 52 | Viewed by 7686

The steel industry represents about 7% of the world’s anthropogenic CO₂ emissions due to the high use of fossil fuels. The CO₂-lean direct reduction of iron ore with hydrogen is considered to offer a high potential to reduce CO₂ [...] Read more.

The steel industry represents about 7% of the world’s anthropogenic CO₂ emissions due to the high use of fossil fuels. The CO₂-lean direct reduction of iron ore with hydrogen is considered to offer a high potential to reduce CO₂ emissions, and this direct reduction of Fe₂O₃ powder is investigated in this research. The H₂ reduction reaction kinetics and fluidization characteristics of fine and cohesive Fe₂O₃ particles were examined in a vibrated fluidized bed reactor. A smooth bubbling fluidization was achieved. An increase in external force due to vibration slightly increased the pressure drop. The minimum fluidization velocity was nearly independent of the operating temperature. The yield of the direct H₂-driven reduction was examined and found to exceed 90%, with a maximum of 98% under the vibration of ~47 Hz with an amplitude of 0.6 mm, and operating temperatures close to 500 °C. Towards the future of direct steel ore reduction, cheap and “green” hydrogen sources need to be developed. H₂ can be formed through various techniques with the catalytic decomposition of NH₃ (and CH₄), methanol and ethanol offering an important potential towards production cost, yield and environmental CO₂ emission reductions. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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11 pages, 2364 KiB

Open AccessArticle

Experimental Study of a Small-Size Vacuum Insulated Water Tank for Building Applications

by David Vérez, Emiliano Borri, Alicia Crespo, Gabriel Zsembinszki, Belal Dawoud and Luisa F. Cabeza

Sustainability 2021, 13(10), 5329; https://doi.org/10.3390/su13105329 - 11 May 2021

Cited by 7 | Viewed by 3646

Abstract

Insulation of thermal energy storage tanks is fundamental to reduce heat losses and to achieve high energy storage efficiency. Although water tanks were extensively studied in the literature, the enhancement of the insulation quality is often overlooked. The use of vacuum insulation has [...] Read more.

Insulation of thermal energy storage tanks is fundamental to reduce heat losses and to achieve high energy storage efficiency. Although water tanks were extensively studied in the literature, the enhancement of the insulation quality is often overlooked. The use of vacuum insulation has the potential to significantly reduce heat losses without affecting the dimension of the storage system. This paper shows for the first time the results of the heat losses tests done for a 0.535 m³ water tank for residential building applications built with a double wall vacuum insulation. The different tests show that the rate of heat losses strictly depends on the temperature distribution inside the tank at the beginning of the experiment. Compared to a conventional water tank insulated with conventional materials, the U-value of the lateral surface was reduced by almost three times (from 1.05 W/K·m² to 0.38 W/K·m²) using vacuum insulation. However, the bottom part, which is usually used to place the support parts and the piping, is the critical design part of those tanks acting as a thermal bridge with the ambient and enhancing heat losses. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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22 pages, 10136 KiB

Open AccessEditor’s ChoiceArticle

Aiming Strategy on a Prototype-Scale Solar Receiver: Coupling of Tabu Search, Ray-Tracing and Thermal Models

by Benjamin Grange and Gilles Flamant

Sustainability 2021, 13(7), 3920; https://doi.org/10.3390/su13073920 - 1 Apr 2021

Cited by 7 | Viewed by 2074

Abstract

An aiming point strategy applied to a prototype-scale power tower is analyzed in this paper to define the operation conditions and to preserve the lifetime of the solar receiver developed in the framework of the Next-commercial solar power (CSP) H2020 project. This innovative [...] Read more.

An aiming point strategy applied to a prototype-scale power tower is analyzed in this paper to define the operation conditions and to preserve the lifetime of the solar receiver developed in the framework of the Next-commercial solar power (CSP) H2020 project. This innovative solar receiver involves the fluidized particle-in-tube concept. The aiming solution is compared to the case without the aiming strategy. Due to the complex tubular geometry of the receiver, results of the Tabu search for the aiming point strategy are combined with a ray-tracing software, and these results are then coupled with a simplified thermal model of the receiver to evaluate its performance. Daily and hourly aiming strategies are compared, and different objective normalized flux distributions are applied to quantify their influence on the receiver wall temperature distribution, thermal efficiency and particle outlet temperature. A gradual increase in the solar incident power on the receiver is analyzed in order to keep a uniform outlet particle temperature during the start-up. Results show that a tradeoff must be respected between wall temperature and particle outlet temperature. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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19 pages, 3198 KiB

Open AccessArticle

Overall Efficiency of On-Site Production and Storage of Solar Thermal Energy

by Teodora M. Șoimoșan, Ligia M. Moga, Livia Anastasiu, Daniela L. Manea, Aurica Căzilă and Čedomir Zeljković

Sustainability 2021, 13(3), 1360; https://doi.org/10.3390/su13031360 - 28 Jan 2021

Cited by 2 | Viewed by 2215

Abstract

Harnessing renewable energy sources (RES) using hybrid systems for buildings is almost a deontological obligation for engineers and researchers in the energy field, and increasing the percentage of renewables within the energy mix represents an important target. In crowded urban areas, on-site energy [...] Read more.

Harnessing renewable energy sources (RES) using hybrid systems for buildings is almost a deontological obligation for engineers and researchers in the energy field, and increasing the percentage of renewables within the energy mix represents an important target. In crowded urban areas, on-site energy production and storage from renewables can be a real challenge from a technical point of view. The main objectives of this paper are quantification of the impact of the consumer’s profile on overall energy efficiency for on-site storage and final use of solar thermal energy, as well as developing a multicriteria assessment in order to provide a methodology for selection in prioritizing investments. Buildings with various consumption profiles lead to achieving different values of performance indicators in similar configurations of storage and energy supply. In this regard, an analysis of the consumption profile’s impact on overall energy efficiency, achieved in the case of on-site generation and storage of solar thermal energy, was performed. The obtained results validate the following conclusion: On-site integration of solar systems allowed the consumers to use RES at the desired coverage rates, while restricted by on-site available mounting areas for solar fields and thermal storage, under conditions of high energy efficiencies. In order to segregate the results and support optimal selection, a multicriteria analysis was carried out, having as the main criteria the energy efficiency indicators achieved by hybrid heating systems. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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16 pages, 1985 KiB

Open AccessArticle

A Practical Methodology for the Design and Cost Estimation of Solar Tower Power Plants

by Omar Behar, Daniel Sbarbaro and Luis Morán

Sustainability 2020, 12(20), 8708; https://doi.org/10.3390/su12208708 - 20 Oct 2020

Cited by 15 | Viewed by 4218

Abstract

Concerns over the environmental influence of greenhouse gas (GHG) emissions have encouraged researchers to develop alternative power technologies. Among the most promising, environmentally friendly power technologies for large-scale applications are solar power tower plants. The implementation of this technology calls for practical modeling [...] Read more.

Concerns over the environmental influence of greenhouse gas (GHG) emissions have encouraged researchers to develop alternative power technologies. Among the most promising, environmentally friendly power technologies for large-scale applications are solar power tower plants. The implementation of this technology calls for practical modeling and simulation tools to both size the plant and investigate the scale effect on its economic indices. This paper proposes a methodology to design the main components of solar power tower plants and to estimate the specific investment costs and the economic indices. The design approach used in this study was successfully validated through a comparison with the design data of two operational commercial power tower plants; namely, Gemasolar (medium-scale plant of 19.9 MW_e) and Crescent Dunes (large-scale plant of 110 MW_e). The average uncertainty in the design of a fully operational power tower plant is 8.75%. A cost estimation showed the strong influence of the size of the plant on the investment costs, as well as on the economic indices, including payback period, internal rate of return, total life charge costs, and levelized cost of electricity. As an illustrative example, the methodology was applied to design six solar power tower plants in the range of 10–100 MW_e for integration into mining processes in Chile. The results show that the levelized cost of electricity decreases from 156 USD/MWh_e for the case of a 10-MW_e plant to 131 USD/MWh_e for the case of a 100-MW_e plant. The internal rate of return of plants included in the analyses ranges from 0.77% (for the 10-MW_e case) to 2.37% (for 100-MW_e case). Consequently, the simple payback ranges from 16 years (for the 100-MW_e case) to 19 years (for the 10-MW_e case). The sensitivity analysis shows that the size of the solar receiver heavily depends on the allowable heat flux. The degradation rate and the discount rate have a strong influence on economic indices. In addition, both the operation and the deprecation period, as well as the price of electricity, have a crucial impact on the viability of a solar power tower plant. The proposed methodology has great potential to provide key information for prospective analyses for the implementation of power tower technologies to satisfy clean energy needs under a wide range of conditions. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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19 pages, 4390 KiB

Open AccessArticle

A Parametric Study of a Solar-Assisted House Heating System with a Seasonal Underground Thermal Energy Storage Tank

by Le Minh Nhut, Waseem Raza and Youn Cheol Park

Sustainability 2020, 12(20), 8686; https://doi.org/10.3390/su12208686 - 20 Oct 2020

Cited by 6 | Viewed by 3259

Abstract

The requirement for energy is increasing worldwide as populations and economies develop. Reasons for this increase include global warming, climate change, an increase in electricity demand, and paucity of fossil fuels. Therefore, research in renewable energy technology has become a central topic in [...] Read more.

The requirement for energy is increasing worldwide as populations and economies develop. Reasons for this increase include global warming, climate change, an increase in electricity demand, and paucity of fossil fuels. Therefore, research in renewable energy technology has become a central topic in recent studies. In this study, a solar-assisted house heating system with a seasonal underground thermal energy storage tank is proposed based on the reference system to calculate the insulation thickness effect, the collector area, and an underground storage tank volume on the system performance according to real weather conditions at Jeju Island, South Korea. For this purpose, a mathematical model was established to calculate its operating performance. This mathematical model used the thermal response factor method to calculate the heat load and heat loss of the seasonal underground thermal energy storage tank. The results revealed that on days with different weather conditions, namely, clear weather, intermittent clouds sky, and overcast sky, the obtained solar fraction was 45.8%, 17.26%, and 0%, respectively. Using this method, we can save energy, space, and cost. This can then be applied to the solar-assisted house heating system in South Korea using the seasonal underground thermal energy storage tank. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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29 pages, 4193 KiB

Open AccessEditor’s ChoiceArticle

A Bibliometric Study on Integrated Solar Combined Cycles (ISCC), Trends and Future Based on Data Analytics Tools

by Miguel Ángel Reyes-Belmonte

Sustainability 2020, 12(19), 8217; https://doi.org/10.3390/su12198217 - 6 Oct 2020

Cited by 11 | Viewed by 2188

Abstract

In this paper, a bibliometric analysis was performed in order to analyze the state of the art and publication trends on the topic of ISCC (Integrated Solar Combined Cycles) for the period covering 1990 to July 2020. The Web of Science (WOS) database [...] Read more.

In this paper, a bibliometric analysis was performed in order to analyze the state of the art and publication trends on the topic of ISCC (Integrated Solar Combined Cycles) for the period covering 1990 to July 2020. The Web of Science (WOS) database was consulted, and 1277 publications from 3157 different authors and 1102 different institutions, distributed among 78 countries, were retrieved as the corpus of the study. The VOSViewer software tool was used for the post-processing of the WOS corpus, and for the network data mapping. Multiple bibliometric indicators, such as the number of citations, keyword occurrences, the authors’ affiliations, and the authors, among others, were analysed in this paper in order to find the main research trends on the ISCC topic. The analysis performed in this paper concluded that the main publication source for ISCC research was Energy Conversion and Management, in terms of the total number of publications (158), but Solar Energy had the highest number of citations on the ISCC topic (4438). It was also found that China was the most productive country in terms of ISCC publications (241), and the Chinese Academy of Sciences was the most productive institution (52). Nevertheless, the author with the most publications on ISCC was I. Dincer, from Ontario Tech University (24). Based on publication keywords, a series of recommendations for future developments in the ISCC topic were derived, as well as the ways in which those ideas are connected to the global state of solar energy research. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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21 pages, 3148 KiB

Open AccessArticle

Energy Analysis of a Novel Ejector-Compressor Cooling Cycle Driven by Electricity and Heat (Waste Heat or Solar Energy)

by Fahid Riaz, Kah Hoe Tan, Muhammad Farooq, Muhammad Imran and Poh Seng Lee

Sustainability 2020, 12(19), 8178; https://doi.org/10.3390/su12198178 - 4 Oct 2020

Cited by 14 | Viewed by 3247

Abstract

Low-grade heat is abundantly available as solar thermal energy and as industrial waste heat. Non concentrating solar collectors can provide heat with temperatures 75–100 °C. In this paper, a new system is proposed and analyzed which enhances the electrical coefficient of performance (COP) [...] Read more.

Low-grade heat is abundantly available as solar thermal energy and as industrial waste heat. Non concentrating solar collectors can provide heat with temperatures 75–100 °C. In this paper, a new system is proposed and analyzed which enhances the electrical coefficient of performance (COP) of vapour compression cycle (VCC) by incorporating low-temperature heat-driven ejectors. This novel system, ejector enhanced vapour compression refrigeration cycle (EEVCRC), significantly increases the electrical COP of the system while utilizing abundantly available low-temperature solar or waste heat (below 100 °C). This system uses two ejectors in an innovative way such that the higher-pressure ejector is used at the downstream of the electrically driven compressor to help reduce the delivery pressure for the electrical compressor. The lower pressure ejector is used to reduce the quality of wet vapour at the entrance of the evaporator. This system has been modelled in Engineering Equation Solver (EES) and its performance is theoretically compared with conventional VCC, enhanced ejector refrigeration system (EERS), and ejection-compression system (ECS). The proposed EEVCRC gives better electrical COP as compared to all the three systems. The parametric study has been conducted and it is found that the COP of the proposed system increases exponentially at lower condensation temperature and higher evaporator temperature. At 50 °C condenser temperature, the electrical COP of EEVCRC is 50% higher than conventional VCC while at 35 °C, the electrical COP of EEVCRC is 90% higher than conventional VCC. For the higher temperature heat source, and hence the higher generator temperatures, the electrical COP of EEVCRC increases linearly while there is no increase in the electrical COP for ECS. The better global COP indicates that a small solar collector will be needed if this system is driven by solar thermal energy. It is found that by using the second ejector at the upstream of the electrical compressor, the electrical COP is increased by 49.2% as compared to a single ejector system. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy)

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