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"Energy conversion."
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Solar power and energy storage systems
Extensive study of solar energy is increasing as fast as the serious threat of global warming. Sunlight is a very important alternative source of energy because it can be converted into electricity. Solar energy is considered the best source of renewable energy because it is clean and unlimited. Solar radiation can be harnessed and converted into different forms of energy that does not pollute the environment. In order to transform solar radiation, we need collectors of sunlight, such as solar cells. The main challenges are energy security, the increasing prices of carbon-based energy sources, and minimizing global warming. We cannot use sunlight during the night, so an energy storage system (ESS) is necessary. The best ESS is one with high power and high energy density. This book introduces the basic concepts of an ESS.
Book
Photocatalytic water splitting with a quantum efficiency of almost unity
Overall water splitting, evolving hydrogen and oxygen in a 2:1 stoichiometric ratio, using particulate photocatalysts is a potential means of achieving scalable and economically viable solar hydrogen production. To obtain high solar energy conversion efficiency, the quantum efficiency of the photocatalytic reaction must be increased over a wide range of wavelengths and semiconductors with narrow bandgaps need to be designed. However, the quantum efficiency associated with overall water splitting using existing photocatalysts is typically lower than ten per cent
1
,
2
. Thus, whether a particulate photocatalyst can enable a quantum efficiency of 100 per cent for the greatly endergonic water-splitting reaction remains an open question. Here we demonstrate overall water splitting at an external quantum efficiency of up to 96 per cent at wavelengths between 350 and 360 nanometres, which is equivalent to an internal quantum efficiency of almost unity, using a modified aluminium-doped strontium titanate (SrTiO
3
:Al) photocatalyst
3
,
4
. By selectively photodepositing the cocatalysts Rh/Cr
2
O
3
(ref.
5
) and CoOOH (refs.
3
,
6
) for the hydrogen and oxygen evolution reactions, respectively, on different crystal facets of the semiconductor particles using anisotropic charge transport, the hydrogen and oxygen evolution reactions could be promoted separately. This enabled multiple consecutive forward charge transfers without backward charge transfer, reaching the upper limit of quantum efficiency for overall water splitting. Our work demonstrates the feasibility of overall water splitting free from charge recombination losses and introduces an ideal cocatalyst/photocatalyst structure for efficient water splitting.
Water splitting with an internal quantum efficiency of almost unity is achieved using a modified semiconductor photocatalyst that selectively promotes the hydrogen and oxygen evolution reactions on separate crystal facets.
Journal Article
Energy conversion and green energy storage
\"Energy Conversion and Green Energy Storage presents recent developments in renewable energy conversion and green energy storage. Covering technical expansions in renewable energy and applications, energy storage, and solar photovoltaics, the book features chapters written by global experts in the field. The book serves as a useful reference for researchers, graduate students, and engineers in the field of energy. Providing insights related to various forms of renewable energy, the book discusses developments in solar photovoltaic applications. The book also includes simulation codes and programs, such as Wien2k code, VASP code, and MATLAB®\"-- Provided by publisher.
Book
Grid converters for photovoltaic and wind power systems
Advancements in grid converter technology have been pivotal in the successful integration of renewable energy. The high penetration of renewable energy systems is calling for new more stringent grid requirements. As a consequence, the grid converters should be able to exhibit advanced functions like: dynamic control of active and reactive current injection during faults, and grid services support. <p>This book explains the topologies, modulation and control of grid converters for both photovoltaic and wind power applications. In addition to power electronics, coverage focuses on the specific applications in photovoltaic and wind power systems where grid condition is an essential factor.</p> <p>With a review of the most recent grid requirements for photovoltaic and wind power systems, the relevant issues are discussed:</p> <ul> <li> <div>Modern grid inverter topologies for photovoltaic and wind turbines</div> </li> <li> <div>Islanding detection methods for photovoltaic systems</div> </li> <li> <div>Synchronization techniques based on second order generalized integrators (SOGI)</div> </li> <li> <div>Advanced synchronization techniques with robust operation under grid unbalance condition</div> </li> <li> <div>Resonant controller techniques for current control and harmonic compensation</div> </li> <li> <div>Grid filter design and active damping techniques</div> </li> <li> <div>Power control under grid fault conditions, considering both positive and negative sequences</div> </li> </ul> <p>Throughout, the authors include practical examples, exercises, and simulation models and an accompanying website sets out further modeling techniques using MATLAB® and Simulink environments and physical security information management (PSIM) software.</p> <p><i>Grid Converters for Photovoltaic and Wind Power Systems</i> is intended as a course book for graduate students with a background in electrical engineering and for professionals in the evolving renewable energy industry. For professors interested in adopting the course, a set of slides is available for download from the website.</p> <p><b>Companion Website</b></p> <p><a href=\"http://www.wiley.com/go/grid_converters\">www.wiley.com/go/grid_converters</a></p>
eBook
Wind power
Readers learn about the history of wind power, how it is used today and how it may be used as an energy source in the future.
Book
Giant bulk piezophotovoltaic effect in 3R-MoS2
Given its innate coupling with wavefunction geometry in solids and its potential to boost the solar energy conversion efficiency, the bulk photovoltaic effect (BPVE) has been of considerable interest in the past decade
1
–
14
. Initially discovered and developed in ferroelectric oxide materials
2
, the BPVE has now been explored in a wide range of emerging materials, such as Weyl semimetals
9
,
10
, van der Waals nanomaterials
11
,
12
,
14
, oxide superlattices
15
, halide perovskites
16
, organics
17
, bulk Rashba semiconductors
18
and others. However, a feasible experimental approach to optimize the photovoltaic performance is lacking. Here we show that strain-induced polarization can significantly enhance the BPVE in non-centrosymmetric rhombohedral-type MoS
2
multilayer flakes (that is, 3R-MoS
2
). This polarization-enhanced BPVE, termed the piezophotovoltaic effect, exhibits distinctive crystallographic orientation dependence, in that the enhancement mainly manifests in the armchair direction of the 3R-MoS
2
lattice while remaining largely intact in the zigzag direction. Moreover, the photocurrent increases by over two orders of magnitude when an in-plane tensile strain of ~0.2% is applied, rivalling that of state-of-the-art materials. This work unravels the potential of strain engineering in boosting the photovoltaic performance, which could potentially promote the exploration of novel photoelectric processes in strained two-dimensional layered materials and their van der Waals heterostructures.
A strain-engineering approach enables enhancement of the bulk photovoltaic effect in non-centrosymmetric rhombohedral-type MoS
2
multilayer flakes.
Journal Article
Near-perfect photon utilization in an air-bridge thermophotovoltaic cell
Thermophotovoltaic cells are similar to solar cells, but instead of converting solar radiation to electricity, they are designed to utilize locally radiated heat. Development of high-efficiency thermophotovoltaic cells has the potential to enable widespread applications in grid-scale thermal energy storage
1
,
2
, direct solar energy conversion
3
–
8
, distributed co-generation
9
–
11
and waste heat scavenging
12
. To reach high efficiencies, thermophotovoltaic cells must utilize the broad spectrum of a radiative thermal source. However, most thermal radiation is in a low-energy wavelength range that cannot be used to excite electronic transitions and generate electricity. One promising way to overcome this challenge is to have low-energy photons reflected and re-absorbed by the thermal emitter, where their energy can have another chance at contributing towards photogeneration in the cell. However, current methods for photon recuperation are limited by insufficient bandwidth or parasitic absorption, resulting in large efficiency losses relative to theoretical limits. Here we demonstrate near-perfect reflection of low-energy photons by embedding a layer of air (an air bridge) within a thin-film In
0.53
Ga
0.47
As cell. This result represents a fourfold reduction in parasitic absorption relative to existing thermophotovoltaic cells. The resulting gain in absolute efficiency exceeds 6 per cent, leading to a very high power conversion efficiency of more than 30 per cent, as measured with an approximately 1,455-kelvin silicon carbide emitter. As the out-of-band reflectance approaches unity, the thermophotovoltaic efficiency becomes nearly insensitive to increasing cell bandgap or decreasing emitter temperature. Accessing this regime may unlock a range of possible materials and heat sources that were previously inaccessible to thermophotovoltaic energy conversion.
An air gap embedded within the structure of a thermophotovoltaic device acts as a near-perfect reflector of low-energy photons, resulting in their recovery and recycling by the thermal source, enabling excellent power-conversion efficiency.
Journal Article
Wind towers : architecture, climate and sustainability
This book offers a holistic treatment of wind towers, from their underlying scientific principles to design and operation. It includes suggestions for optimization based on the authors' own research findings from recent analytical studies.
Book
Gradient tantalum-doped hematite homojunction photoanode improves both photocurrents and turn-on voltage for solar water splitting
Hematite has a great potential as a photoanode for photoelectrochemical (PEC) water splitting by converting solar energy into hydrogen fuels, but the solar-to-hydrogen conversion efficiency of state-of-the-art hematite photoelectrodes are still far below the values required for practical hydrogen production. Here, we report a core-shell formation of gradient tantalum-doped hematite homojunction nanorods by combination of hydrothermal regrowth strategy and hybrid microwave annealing, which enhances the photocurrent density and reduces the turn-on voltage simultaneously. The unusual bi-functional effects originate from the passivation of the surface states and intrinsic built-in electric field by the homojunction formation. The additional driving force provided by the field can effectively suppress charge–carrier recombination both in the bulk and on the surface of hematite, especially at lower potentials. Moreover, the synthesized homojunction shows a remarkable synergy with NiFe(OH)
x
cocatalyst with significant additional improvements of photocurrent density and cathodic shift of turn-on voltage. The work has nicely demonstrated multiple collaborative strategies of gradient doping, homojunction formation, and cocatalyst modification, and the concept could shed light on designing and constructing the efficient nanostructures of semiconductor photoelectrodes in the field of solar energy conversion.
Solar-to-fuel conversion represents a renewable means to harvest sunlight, but the most efficient materials are often expensive or rare. Here, authors demonstrate gradient tantalum-doped hematite homojunctions as a method to improve photoelectrochemical water splitting performances.
Journal Article