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1441 results in Energy Technology

Page 38 of 73

  • 10 - Design and Implementation of Off-Grid and On-Grid SPV Systems

  • J. N. Roy, D. N. Bose
  • Book:
    Photovoltaic Science and Technology
    Published online:
    05 July 2018
    Print publication:
    15 November 2017, pp 358-400

  • Summary

    INTRODUCTION

    An overview of the Solar Photovoltaic (SPV) systems has been presented in Chapter 9. The entire system [1–9] consists of: (a) solar field; (b) structure; (c) Balance of System (BOS) comprising DC-DC converter, Maximum Power Point Tracking (MPPT), inverter/ Power Conditioning Unit (PCU) and other accessories such as LT panel, cables, combiner box, connectors, etc.; (d) storage, if required, comprising battery and charge controller and (e) transformer for on-grid systems. A solar field provides a varying DC output decided primarily by insolation and ambient conditions. The design and implementation of the solar fields consisting of solar modules connected in series and parallel, known as ‘string and array design’, has been discussed in some detail in Chapter 9. Structures are required to mount the modules. The structure for a fixed system is relatively simple. Tracking structures are more complex as these require provision for movement of the modules according to the Sun's position. Motors with movable structures are, therefore, required for such installations. The movement of the motor can be programmed to ensure that the Sun's rays fall perpendicular to the module face whenever possible. Dual axis tracking is even more complex than single axis tracking. It may be noted that the power required for driving the motors are provided from the power generated from the SPV plant.

    The DC-DC converter along with MPPT takes the output of the solar field as an input and converts this to a maximum possible stable DC output. In case storage is provided, a battery is required to store some amount of energy for later use. A charge controller is also required to manage the charging and discharging of the battery. The inverter provides the AC output to the corresponding loads. A solar inverter consists of DC-DC with MPPT control and DC-AC converters. A Power Conditioning Unit (PCU) is essentially a solar inverter along with a charge controller. Accessories, such as cables, connectors, combiner box, LT panel, etc., are required to implement the string and array design (DC side) and manage the interface between inverter/PCU output and load (AC side). An on-grid system, which is also known as ‘SPV power plant’, sends the generated power to the electricity grid local substation.

  • 9 - Overview of Solar PV System Technology and Design

  • J. N. Roy, D. N. Bose
  • Book:
    Photovoltaic Science and Technology
    Published online:
    05 July 2018
    Print publication:
    15 November 2017, pp 320-357

  • Summary

    INTRODUCTION

    Our conventional energy reserves are limited and have severe environmental impact. There has been all round focus on the development of renewable energy primarily due to these facts, as well as from the perspective of energy security, climate change and energy access. Solar energy has been the Earth's most available energy source, capable of providing many times the total energy demand. Solar Photovoltaic (SPV) deals with conversion of sunlight into electricity. Governments across the world have realized the importance of solar power and over 60 countries have introduced feed-in tariffs, capital subsidies and incentives for productions to promote wider adoption and advancement of SPV. The average growth rate of global SPV capacity has been close to 40%, with the total installed capacity now approaching 350GWP. Renewable energy initiatives, particularly SPV, have picked up pace in India also. The Jawaharlal Nehru National Solar Mission (JNNSM) has been a major initiative of the Government of India to give an impetus to the domestic solar power industry. It sets an ambitious target of 20 GW of solar power capacity by 2022. Several State Governments have announced independent policies in SPV.

    Solar PV systems [1–7] occupy a very important place in the SPV value chain (Figure 9.1). As it comes at the end point of the value chain, it decides the amount of power finally supplied. The power generated by a SPV system depends on the previous operations of the value chain as well. In the crystalline silicon (c-Si) technology, the type of wafers (mono or multi) and the efficiency of the solar cells, decided by the cell manufacturing technology, play a very important role. Assembly of the solar cells to make modules has been somewhat straightforward for c-Si technology. Thin film technology (a-Si, CdTe, CIGS, etc.) takes a different route in the value chain diagram (Figure 9.1). The modules are made directly by the Chemical Vapour Deposition (CVD) technique to deposit thin layers of appropriate materials on a conductive glass substrate to form p-n junction solar cell. In this case also the efficiency is decided by several factors such as material (Si, CdTe, CIGS, etc.), structure (amorphous, microcrystalline, etc.) and configuration (single junction, tandem junction, etc.).

  • 5 - Organic and Polymer Solar Cells

  • J. N. Roy, D. N. Bose
  • Book:
    Photovoltaic Science and Technology
    Published online:
    05 July 2018
    Print publication:
    15 November 2017, pp 134-157

  • Summary

    INTRODUCTION

    There has been rising interest followed by extensive research on organic and polymer solar cells in the last three decades. Organic semiconductors have made great strides since conductivity [1] and electroluminescence [2] in Anthracene were studied in the 1960s by Kallmann and his group. Electronic processes in organic materials have been thoroughly discussed by Pope and Swinberg [3]. Rapid progress in the field of organic materials is exemplified by the commercial success of Organic Light Emitting Diodes (OLEDS) in mobile phones and other applications. This has been possible through the tailor-making of the properties of organic semiconductors to emit light across the visible spectrum from blue to red [4]. Recently Heliatek [5], a German firm, has achieved a record conversion efficiency of 13.2% for an Organic Photovoltaic (OPV) Multi-junction (MJ) cell using small molecules. The cell has three absorber layers for absorbing light from the near infrared, red and green wavelengths, covering the major part of the solar spectrum from 450 nm to 950 nm. Stability of the small molecules is projected for 25 years. This achievement has provided great impetus to commercial development. Thus, there is, in principle, no reason why organic solar cells with their inherent advantages, discussed below, should not usher in the third generation of solar cells [6, 7].

    At the outset it is necessary to distinguish between the types of organic and polymer materials for PV applications.

    Organic semiconductors can be classified into two broad types [8]:

  • (a) Small molecules with molecular weight (MW) < 1000; usually deposited by physical vapour deposition

  • (b) Polymeric films[9] with molecular weight (MW) > 10,000; deposited by casting from solution, spin coating, doctor blading screen, or inkjet printing. Though thin films are reasonably easy to form, their molecular weight and purity are hard to control.

    • ENERGY LEVELS

    Organic solids and polymers are generally considered to be insulators. However, both, the small molecules and polymers (Figure 5.1) used as light-absorbing materials have large conjugated systems in which carbon atoms covalently bond with alternating single and double bonds. These electrons in orbitals delocalize and form a delocalized bonding orbital with a anti-bonding orbital. The delocalized orbital forms the Highest Occupied Molecular Orbital (HOMO) and the orbital forms the Lowest Unoccupied Molecular Orbital (LUMO).

  • Preface

  • J. N. Roy, D. N. Bose
  • Book:
    Photovoltaic Science and Technology
    Published online:
    05 July 2018
    Print publication:
    15 November 2017, pp xxvii-xxx

  • Summary

    The growth and demand for Solar Photovoltaic (SPV) energy systems has been strong and in line with the increasing importance of renewable energy. Worldwide demand and production of SPV systems has been growing at a compound annual growth rate of more than 30% over the last decade. There have been significant advances in technology, spanning the entire value chain consisting of solar cells, modules and balance-of-system (BOS) components. This has resulted in an increase in efficiency and a significant cost reduction over the years, making SPV systems viable both in small stand-alone and large grid-connected applications.

    Solar energy, which is the Earth's most available energy source, can be converted to electricity providing scalable and clean power requiring minimal maintenance. This book deals with the subject of Solar Photovoltaics in some detail covering the basics as well as advanced topics. All the important areas of SPV, covering both science and technology, have been addressed in this book. Commencing with the basic principles, different types of solar cells from bulk silicon (Si) to thin film cells are described comprehensively. Tandem concentrator cells now provide the highest efficiencies of 43%. Newer low cost alternatives, such as organics and perovskites, are also discussed. Manufacturing details have been covered in great detail. The basic cost and investment calculations of SPV manufacturing and systems leading to economic viability have also been included. These aspects are generally not covered in most of the books published in this field. Several practical and state-of-the art manufacturing and system design details have been presented based on the experience of one of the authors (J. N. Roy). This book should be useful for students studying this important subject, who eventually want to pursue careers in this field. The book should be also useful for researchers and industry personnel who want to have a thorough understanding of the subject. Each chapter has illustrations and tables. There are several examples and exercises throughout the book to help consolidate thorough learning of the subject.

    Chapter 1 presents a general introduction to the subject of solar energy in the context of global warming. Solar insolation and distribution are presented and some basic terms are defined. This is followed by the principles of operation of SPV devices, device characteristics, criteria for choice of materials, and critical parameters for efficient operation.

Photovoltaic Science and Technology
  • J. N. Roy, D. N. Bose
  • Published online:
    05 July 2018
    Print publication:
    15 November 2017
  • Solar photovoltaics (SPV) forms an integral part of renewable energy systems that are crucial for combating global warming. Written to serve as an ideal text for students, researchers and industrial personnel, it discusses the principles of operation of photovoltaic devices, their limitations, choice of materials, and maximum efficiencies. It covers in depth discussion of new materials and devices based on organics and perovskites, and a flow-chart of the manufacture of Si, GaAs and CdTe cells, their characterization and testing. It highlights characterization, testing and reliability of solar PV modules, comparison of fixed and tracking SPV systems using concentrator cells. Economical aspects of grid-connected and stand-alone systems and a wide range of applications, from solar pumps, and street lighting to large power plants is covered in the text. Several aspects such as cell and module manufacture, characterization, testing, reliability, and system design are described considering commercial SPV manufacturing plants.

  • 1 - Overview

  • Liang-Shih Fan, Ohio State University
  • Book:
    Chemical Looping Partial Oxidation
    Published online:
    07 November 2017
    Print publication:
    12 October 2017, pp 1-54

  • Summary

    Introduction

    The term “chemical looping” was first used by Ishida et al. (1987) to describe a high exergy efficiency combustion process that engages redox reactions employing metal oxides as a reaction intermediate. In an earlier book of Fan, the term “chemical looping” was used in a broad sense to describe the nature of a reaction scheme in which a given reaction is decomposed into multiple sub-reactions using chemical intermediates that are reacted and regenerated. Further, the sub-reactions are ideally configured in such a manner that the exergy loss of the process as a result of this reaction scheme can be minimized. The term in this broad sense, which has been of interest to industrial practice, can be dated to the late nineteenth century, and is used again in this book. The chemical intermediates considered in the chemical looping reactions are mainly metal oxides. The concept of chemical looping is rooted in the second law of thermodynamics as applied to the reduction of process irreversibility and hence the enhanced exergy efficiency of the process. The application of this exergy concept for combustion systems was reported earlier by Knoche and Richter (1968, 1983). In the work of Ishida et al. (1987), they employed metal oxides such as NiO, CuO, Mn2O3, and Fe2O3 as chemical intermediates for combustion reaction applications. The unique feature of using a metal oxide in a chemical looping combustion scheme is that CO2 becomes an easily separable combustion product and thus, the parasitic energy requirement in the CO2 separation is low in this combustion system. Such a CO2 separation feature has been deemed to be important in recent years, particularly in light of global concerns over the increasing CO2 concentration in the atmosphere.

    Aside from electricity generation from chemical looping combustion, chemicals can also be generated from chemical looping routes that have considerable process advantages. Chemicals such as propylene, butadiene, benzene, and xylene are currently produced mainly from petroleum through catalytic and/or thermal cracking processes of crude oil to naphtha, butane, and propane. When the feedstock is coal or natural gas, the production processes are different. For coal, chemicals are produced via two routes. One route is through coal gasification to generate syngas, then synthesized to chemicals; the other route is through coal pyrolysis to generate volatiles, then refined to chemicals.

  • 5 - Catalytic Metal Oxides and Applications

  • Liang-Shih Fan, Ohio State University
  • Book:
    Chemical Looping Partial Oxidation
    Published online:
    07 November 2017
    Print publication:
    12 October 2017, pp 307-369

  • Summary

    Introduction

    Selective oxidation reactions of carbon based feedstocks synthesize important chemicals and their precursors, such as alcohols, epoxides, aldehydes, and other organic compounds. They employ catalytic metal oxides, which are multifunctional, enabling materials, to fulfill three parallel roles: (1) provide active surface sites for the reactants without participating in the reaction; (2) reduce the activation energies of the reaction pathway; and (3) oxidize the reactants through the transfer of their lattice oxygen during reduction. The third role is akin to the well-known catalytic surface Mars–Van Krevelen mechanism, which is further discussed in this section and Section 5.6, that is characterized by the reaction products incorporating the compounds of the catalytic material lattice. In these kinds of selective oxidation reactions, the catalytic metal oxides behave as “oxygen carriers,” where oxygen from the crystal lattice bonds with the reactants. In these reactions, the surface of the metal oxide is reduced by the hydrocarbon reactant and can later be re-oxidized by gaseous oxygen.

    The selectivity of a catalytic metal oxide can be controlled by multiple factors, such as structure, chemistry, electronic properties, composition, kinetics, and energies. An ideal selective catalytic metal oxide needs to be tailored specifically for the application at hand. Hence, it becomes essential to understand the surface morphology, crystal structure, and the reaction mechanisms involved. The accessibility and mobility of lattice oxygen play a vital role in determining the reactivity and selectivity of the catalytic metal oxides. The structure of the catalytic metal oxide should allow for sufficient transportation of lattice oxygen toward the surface and needs to be able to sustain the vacancy created by the absence of oxygen. That is, the host structure needs to provide a sustainable pathway for the ions to diffuse in order to utilize the lattice oxygen. While participation of lattice oxygen facilitates the oxidation–reduction of the process, it does not necessarily result in high product selectivity. The selectivity of a given structure can originate from the bond strength between metal and oxygen, where a weak metal–oxygen bond will release oxygen that can fully oxidize the reactant and yield an undesired product. An ideal catalytic metal oxide with readily accessible and mobile lattice oxygen, appropriate host structure, and suitable metal–oxygen bond strength has the potential to be both reactive and selective when reduced.

  • 4 - Syngas Generation

  • Liang-Shih Fan, Ohio State University
  • Book:
    Chemical Looping Partial Oxidation
    Published online:
    07 November 2017
    Print publication:
    12 October 2017, pp 236-306

  • Summary

    Introduction

    Syngas, predominantly a mixture of H2 and CO, is an important feedstock for the production of many valuable commodity chemicals such as methanol, synthetic liquid fuels, ammonia, and hydrogen. Since syngas forms the backbone of many chemical industries, its purity, H2:CO ratio, and cost have a major effect on the operation and economics of downstream chemical processing systems. Over the years, the process of syngas production has evolved from simply passing steam over hot coke to the use of large-scale solid circulating units that process a variety of hydrocarbon feedstocks. Some syngas production processes have been used at the commercial scale while others are still being developed at the lab and bench scale. Considerable knowledge has been gained from large-scale operations, and these have been valuable in paving the way for further innovations and new technologies development.

    Gasification and reforming are the two processes that form the basis of all syngas production technologies. Syngas production technologies involve the use of oxidative reagents like oxygen, steam, CO2, and more recently metal oxide oxygen carriers, to selectively convert various hydrocarbon feedstocks to syngas. The term “selective” is significant since the formation of full combustion products, CO2 and H2O, is undesirable. Therefore, careful consideration is required when selecting operating conditions like temperature, pressure, catalyst, and/or metal oxide oxygen carriers. The ultimate goal for generating syngas is a process that is simple in operation and low in energy and cost requirements. For operation with metal oxides, as in chemical looping processes, combustion applications have been studied extensively. Relatively little has been probed on chemical looping gasification and reforming. There is a distinct difference in operating strategy between chemical looping gasification/chemical looping reforming (CLG/CLR) and chemical looping combustion (CLC) processes. The CLC processes can achieve a complete reactant gas oxidation with a low reactant gas to oxygen carrier ratio. The CLG/CLR processes, on the other hand, can achieve a partial or selective reactant fuel oxidation with a high reactant fuel to oxygen carrier ratio.

    In this chapter, syngas generation technologies based on conventional processes and chemical looping processes are discussed. Specifically, Section 4.2 provides a historical viewpoint on the development of current commercial-scale syngas generation processes. An account of each of the technologies followed by examples of their application in commercial operation is given.

  • Preface

  • Liang-Shih Fan, Ohio State University
  • Book:
    Chemical Looping Partial Oxidation
    Published online:
    07 November 2017
    Print publication:
    12 October 2017, pp xv-xviii

  • Summary

    This book is written as a sequel to an earlier book, entitled “Chemical Looping Systems for Fossil Energy Conversions,” published in 2010 by Wiley/AICHE. For the earlier book, the motivation was to elucidate the rationale for the resurgence of chemical looping technology research and development related to the ease in CO2 emission control and the enhancement in exergy conversion efficiency for combustion of carbonaceous fuels. The earlier book clearly indicated that the success of chemical looping technology depends strongly on the viability of the metal oxide materials for its redox applications. Knowledge of fundamental properties of these materials such as redox phase behavior, reactivity, recyclability, and metal oxide support is essential for characterizing chemical looping system performance for the conversion of coal, natural gas, petrochemicals, and biomass. Furthermore, it elaborated gasification or reforming processes involving syngas generation from traditional coal gasifiers, and the use of syngas as feedstock for hydrogen production through a steam–iron chemical looping reaction scheme. It also covered traditional methane–steam reforming applications that are coupled with chemical looping heating schemes, followed by water–gas shift reactions for hydrogen generation. Chemical looping process simulations based on Aspen Plus® utilizing reactors such as gasifier, reducer, oxidizer, combustor, and processes such as conventional gasification and chemical looping for electricity and liquid fuel production were presented.

    My motivation for writing this book was precipitated by the exciting recent revelation of direct, one-step, chemical looping partial oxidation techniques in gasifiers and reformers using carbonaceous feedstock. These techniques can produce syngas of a high quality, leading to process efficiencies far greater than any traditional gasification or reforming techniques and other chemical looping techniques. The implications of this discovery are significant in that syngas compositions can reach to near the thermodynamic conversion limit with a H2:CO molar ratio that can readily be used for direct downstream chemicals or liquid fuels synthesis. The uniqueness of these gasification and reforming techniques is that the syngas stream from the chemical looping reducer reactor will contain little CO2, yielding a process of high carbon utilization efficiency. Even higher carbon utilization efficiencies can be achieved in a chemical looping process scheme for chemicals or liquid fuels production when the CO2 generated from the process system can be fully recycled to the reducer reactor, yielding a CO2 neutral chemical looping process system.

  • 3 - Oxidative Coupling of Methane

  • Liang-Shih Fan, Ohio State University
  • Book:
    Chemical Looping Partial Oxidation
    Published online:
    07 November 2017
    Print publication:
    12 October 2017, pp 172-235

  • Summary

    Introduction

    The conversion of carbonaceous feedstocks into higher value products occurs through two major routes: (1) indirect oxidation; and (2) direct oxidation, as shown in Figure 3.1. In the indirect oxidation approach, carbonaceous feedstock is first oxidized to syngas, which can then be further converted to value-added products. With respect to syngas generation, the thermodynamics and reaction characteristics of metal oxide oxygen carriers are discussed in Chapter 2; chemical looping reactor configurations are discussed in Chapter 4; and the techno-economic analyses of several chemical looping processes are discussed in Chapter 6. In the direct oxidation approach, the carbonaceous feedstock is directly upgraded to the desired product. Conceptually, the direct route simplifies the overall process and reduces costs by removing processing steps, but no commercial-scale system exists. Early research activity on direct oxidation processes, specifically for methane, can be traced back to the 1920s, but the utilization of methane in the chemical industry has been limited due to its high molecular stability. Currently, direct methane utilization involves conversion to value-added products such as aromatics, oxygenates, olefins, and paraffins, of which the three major oxidative processes are partial oxidation to methanol, to formaldehyde, as given in Section 5.4, and to ethylene and ethane via the oxidative coupling of methane (OCM).

    Volatility in petroleum prices and limited petroleum reserves have made natural gas resources progressively more attractive as an energy source. Recent discoveries of natural gas reserves, increased accessibility to shale gas, and low natural gas prices have propelled a resurgence in methane-to-chemicals research. Monetizing cheap natural gas to obtain higher value-added products would provide a critical opportunity to the petroleum and chemical industry.9 Research into one promising direct route, OCM, has exhibited peaks and troughs, as shown in Figure 3.2. To date, pilot-scale systems were constructed and tested at the Atlantic Richfield Company (ARCO) in the 1990s. In 2012, Honeywell announced plans to scale up a proof-of-concept direct methane conversion process to ethylene. More recently, in 2015 Siluria Technologies began operating a pilot-scale OCM demonstration unit to convert methane to ethylene or gasoline.

    In this chapter, the direct oxidation of methane to ethylene and higher hydrocarbons through OCM is presented.

  • 6 - Process Simulations and Techno-Economic Analyses

  • Liang-Shih Fan, Ohio State University
  • Book:
    Chemical Looping Partial Oxidation
    Published online:
    07 November 2017
    Print publication:
    12 October 2017, pp 370-439

  • Summary

    Introduction

    A process simulation is the representation of a thermal or chemical transformation by a mathematical model that is solved to provide information about mass and energy requirements, equipment performance, and overall process feasibility. They are system level models used for economic calculations, energy efficiency analyses, and process comparisons. Component level information such as reactor geometry, mixing and hydrodynamics, and transport phenomena, as well as molecular level information such as surface area, reaction mechanism, and electronic interactions, are not included. Beginning with FlowTran, developed by Monsanto in the 1950s and 1960s, several process simulation software packages have since been developed, including ProSim, PRO/II, gPROMS, ChemCAD, and Aspen Plus®, and they play an important role in process development by allowing for the evaluation of a commercial scale plant based on available experimental results.

    The process simulation software that is used extensively throughout academic research and industrial operations is Aspen Plus®. Aspen was developed in the late 1970s at Massachusetts Institute of Technology for the United States Energy Research and Development Administration (now United States Department of Energy or USDOE). The project objective was to develop a computer program to aid in performing process evaluations; mainly process economics. Today, Aspen has evolved into Aspen Plus® and, as part of the AspenOne package software suite, has become the essential plant and process design software program. Aspen Plus® provides complete flexibility in designing a process simulation. Every new process begins by specifying the component species and the property method used for calculating the component species thermodynamic properties. Together, these two required specifications display the strength of the Aspen Plus® software program, due to its extensive chemical databank, available methods for calculating thermodynamic properties, and ability to adjust property values when necessary. Once the component species and property methods have been selected, Aspen Plus® assumes control and calculates the thermodynamic properties based on user input, and only allows the inputs required to satisfy the degrees of freedom. The chemical looping partial oxidation examples and the results presented in this chapter were obtained using Aspen Plus® (AspenTech), and they are available on the website as supplemental material.

  • 2 - Metal Oxide Oxygen Carriers

  • Liang-Shih Fan, Ohio State University
  • Book:
    Chemical Looping Partial Oxidation
    Published online:
    07 November 2017
    Print publication:
    12 October 2017, pp 55-171

  • Summary

    Introduction

    Partial oxidation of carbonaceous fuels in the chemical looping process uses metal oxide based oxygen carriers for the transfer of oxygen from air to the fuel. As discussed in Chapter 1, in a chemical looping partial oxidation (CLPO) process, oxygen carriers provide oxygen to partially oxidize the fuel in the fuel reactor or the reducer, thereby undergoing reduction themselves. The reduced oxygen carriers are then regenerated by air in the air reactor or the combustor and circulated back to the reducer. The oxidation reactions occurring in the combustor are highly exothermic and the heat generated can be used for power generation. The CLPO process thus generates separate streams of syngas or chemicals from the reducer and an O2-depleted flue gas from the combustor, which obviates many downstream processing steps for product generation.

    Oxygen carrier materials play a key role in determining the product quality and process efficiency for a CLPO process. During reduction, the oxygen carrier donates the required amount of lattice oxygen for fuel conversion and product synthesis. In the oxidation step, the depleted oxygen carriers are replenished with oxygen from the air while heat is released, allowing for autothermal operation. Extensive research has been conducted into the design and development of optimum oxygen carrier materials. Oxygen carriers for successful chemical looping operation need to possess certain properties, like high oxygen carrying capacity, high fuel conversion, good redox reactivity, fast kinetics, good recyclability, long-term stability, high attrition resistance, good heat carrying capacity, high melting point, resistance to toxicity, and low production cost. In addition, the applications for partial oxidation require certain distinct oxygen carrier properties in order to accurately control product selectivity. Various materials have been studied for CLPO applications. During the early stages of development, single component materials were used as oxygen carriers. More recently, the development of oxygen carriers has been directed towards using multiple metal based composite materials as oxygen carriers for improved performance. While selecting oxygen carrier materials, an understanding of the underlying mechanisms helps in engineering particles with the desired qualities. The structural evolution and integrity of these particles during reaction has a direct implication on particle strength and reactivity. These, in turn, are governed by intrinsic ionic transfer mechanisms.

    Some of the major challenges in the development of oxygen carriers include designing oxygen carriers with both good reactivity and good recyclability.

Page 38 of 73