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Journal ArticleDOI

A realizable renewable energy future

30 Jul 1999-Science (American Association for the Advancement of Science)-Vol. 285, Iss: 5428, pp 687-689
TL;DR: The ability of renewable resources to provide all of society's energy needs is shown by using the United States as an example, and the issues of energy payback, carbon dioxide abatement, and energy storage are addressed.
Abstract: The ability of renewable resources to provide all of society's energy needs is shown by using the United States as an example. Various renewable systems are presented, and the issues of energy payback, carbon dioxide abatement, and energy storage are addressed. Pathways for renewable hydrogen generation are shown, and the implementation of hydrogen technologies into the energy infrastructure is presented. The question is asked, Should money and energy be spent on carbon dioxide sequestration, or should renewable resources be implemented instead.
Citations
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Journal ArticleDOI
TL;DR: The biggest challenge is whether or not the goals need to be met to fully utilize solar energy for the global energy demand can be met in a costeffective way on the terawatt scale.
Abstract: Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

8,037 citations

Journal ArticleDOI
TL;DR: This review highlights the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER), and summarizes some important examples showing that non-Pt HER electrocatsalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalyst.
Abstract: Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

4,351 citations

Journal ArticleDOI
TL;DR: The Scope of Review: Large-Scale Centralized Energy Storage, Chemical Energy Storage: Solar Fuels, and Capacitors 6486 5.1.2.
Abstract: 1. Setting the Scope of the Challenge 6474 1.1. The Need for Solar Energy Supply and Storage 6474 1.2. An Imperative for Discovery Research 6477 1.3. Scope of Review 6478 2. Large-Scale Centralized Energy Storage 6478 2.1. Pumped Hydroelectric Energy Storage (PHES) 6479 2.2. Compressed Air Energy Storage (CAES) 6480 3. Smaller Scale Grid and Distributed Energy Storage 6481 3.1. Flywheel Energy Storage (FES) 6481 3.2. Superconducting Magnetic Energy Storage 6482 4. Chemical Energy Storage: Electrochemical 6482 4.1. Batteries 6482 4.1.1. Lead-Acid Batteries 6483 4.1.2. Alkaline Batteries 6484 4.1.3. Lithium-Ion Batteries 6484 4.1.4. High-Temperature Sodium Batteries 6484 4.1.5. Liquid Flow Batteries 6485 4.1.6. Metal-Air Batteries 6485 4.2. Capacitors 6485 5. Chemical Energy Storage: Solar Fuels 6486 5.1. Solar Fuels in Nature 6486 5.2. Artificial Photosynthesis and General Considerations of Water Splitting 6486

2,570 citations

Journal ArticleDOI
TL;DR: In this article, a review of the current state of knowledge and technology of hydrogen production by water electrolysis and identifies areas where R&D effort is needed in order to improve this technology.

2,396 citations


Cites background from "A realizable renewable energy futur..."

  • ...With ever increasing energy costs owing to the dwindling availability of oil reserves, production and supply [17] and concerns with global warming and climate change blamed on man-made carbon dioxide (CO2) emissions associated with fossil fuel use [18], particularly coal use [2], hydrogen has in recent years become very popular for a number of reasons: (1) it is perceived as a clean fuel, emits almost nothing other than water at the point of use; (2) it can be produced using any energy sources, with renewable energy being most attractive [19]; (3) it works with fuel cells [20–22] and together, they may serve as one of the solutions to the sustainable energy supply and use puzzle in the long run, in so-called ‘‘hydrogen economy’’ [23,24]....

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Journal ArticleDOI
TL;DR: A comprehensive review of the potential role that hydrogen could play in the provision of electricity, heat, industry, transport and energy storage in a low-carbon energy system, and an assessment of the status of hydrogen in being able to fulfil that potential is presented in this article.
Abstract: Hydrogen technologies have experienced cycles of excessive expectations followed by disillusion. Nonetheless, a growing body of evidence suggests these technologies form an attractive option for the deep decarbonisation of global energy systems, and that recent improvements in their cost and performance point towards economic viability as well. This paper is a comprehensive review of the potential role that hydrogen could play in the provision of electricity, heat, industry, transport and energy storage in a low-carbon energy system, and an assessment of the status of hydrogen in being able to fulfil that potential. The picture that emerges is one of qualified promise: hydrogen is well established in certain niches such as forklift trucks, while mainstream applications are now forthcoming. Hydrogen vehicles are available commercially in several countries, and 225 000 fuel cell home heating systems have been sold. This represents a step change from the situation of only five years ago. This review shows that challenges around cost and performance remain, and considerable improvements are still required for hydrogen to become truly competitive. But such competitiveness in the medium-term future no longer seems an unrealistic prospect, which fully justifies the growing interest and policy support for these technologies around the world.

1,938 citations

References
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Journal ArticleDOI
17 Apr 1998-Science
TL;DR: Direct water electrolysis was achieved with a novel, integrated, monolithic photoelectrochemical-photovoltaic design that splits water directly upon illumination; light is the only energy input.
Abstract: Direct water electrolysis was achieved with a novel, integrated, monolithic photoelectrochemical-photovoltaic design. This photoelectrochemical cell, which is voltage biased with an integrated photovoltaic device, splits water directly upon illumination; light is the only energy input. The hydrogen production efficiency of this system, based on the short-circuit current and the lower heating value of hydrogen, is 12.4 percent.

2,052 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the energy invested in photovoltaic modules on the basis of currently operating commercial production lines in France and found an average energy pay-back time of 1.2 years for amorphous silicon modules and 2.1 years for crystalline silicon modules.
Abstract: The energy invested in photovoltaic modules has been investigated on the basis of currently operating commercial production lines in France. The analysis was made for two types of solar cells, polycrystalline silicon and amorphous silicon. The energy which was calculated in this way was compared with the energy produced by these modules under operating conditions in various European climates. An average energy pay-back time of 1.2 years for amorphous silicon modules and 2.1 years for crystalline silicon modules was found. It can be anticipated that these energy pay-back times will decrease in the future.

54 citations