Category Fuel of the Future

Current Electrolytic Technologies

The kinetics of the O2 and H2 evolution reactions at the electrodes limit how fast hydrogen can be generated and are dependent on the electro­de’s chemical activity. Precious metals such as platinum and palladium generally make good electrodes, but they are prohibitively expensive. The reaction can be ‘‘overdriven’’ by applying a larger voltage than the minimum required, but this reduces the efficiency. For water splitting, the oxygen-evolving anode is the larger contributor to the problem, requiring a larger overpotential.

In general, first, to enhance the water conductivity and thus the overall rate of the process of water electrolysis, an electrolyte is dissolved in water...

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Water Electrolysis with Solar Electricity

2.1 Water Electrolysis

Electrolytic production of hydrogen by water electrolysis is a well known electrochemical process first described by William Nicholson and Anthony Carlisle in 1800, a few weeks after Volta described his new ‘‘voltaic’’ pile.1 In detail, the splitting of one mole of water into gaseous H2 and O2 by the action of electricity (Equation 2.1, where F is the Faraday constant measuring 1 mole of electricity, 96485 C) produces a mole of hydrogen gas and a half-mole of oxygen gas in their normal diatomic forms:

H2O(l)+2F ! H2(g)+ 202(g) (2.1)

An electrolyzer uses electricity to split water into the component elements...

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The Hydrogen Science & Technology Network

In 1974, a few scholars in the United States started the International Association for Hydrogen Energy (IAHE).52 In 1981 they established

the International Journal of Hydrogen Energy, published monthly by Elsevier since 1982. The journal is nowadays one of the primary lit­erature sources for the exchange and dissemination of basic ideas in the field of hydrogen energy, whereas the World Hydrogen Energy Con­ference, organized by the IAHE every two years on a different continent, attracts about 1500 attendees. The monthly Hydrogen & Fuel Cell Letter (www. hfcletter. com), which covers the science, business and politics of hydrogen and fuel cells, has been published continuously since 1986 and is widely regarded as an important voice in the international hydrogen community.

From Germany to ...

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Hydrogen as Energy Carrier: Exergizing the Energy System

Recently, Joshi and co-workers evaluated the performance of the two routes of hydrogen production that are relevant to this textbook, namely PV and solar thermal systems, based on exergy analysis and a ‘‘sustain­ability index’’.46 As expected, the solar thermal hydrogen production system has a higher sustainability index because of higher exergy effi­ciency, when compared with the PV hydrogen production system whose exergy efficiency ranges between 3.68 and 4.84%. The exergy efficiencies of concentrating the collector increase with increasing solar radiation.

In brief, whenever energy is converted (produced, handled, stored, transported, disseminated, utilized, etc.) it is split into two parts (Equation 1.4):

Energy = exergy + anergy (1.4)

Exergy is the maximum amount of availabl...

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Hydrogen Safety and Sustainability

Given that it is so light, in the early 1900s hydrogen was used for about two decades to lift huge dirigibles until, on 6 May 1937, the Hindenburg, a rigid airship lifted by hydrogen, caught fire in midair over New Jersey and was destroyed during its attempt to dock with its mooring tower at the Lakehurst Naval Air Station (Figure 1.19). Out of 97 people aboard, 62 survived the crash at Lakehurst, although many suffered serious injuries, but 35 passengers perished, along with one member of the civilian landing party.

Ignition of leaking hydrogen is widely assumed to have been the cause of this disaster, even if the visible flames were from combustion of the aluminized fabric coating...

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Solar Hydrogen

Hydrogen generated by water splitting induced by solar energy is the fuel of the future, which can replace fossil fuels and ultimately cease our dependence (or ‘‘addiction’’,22 to quote a former US president) on fossil hydrocarbons and coal, thus ending the emission of CO2 into the atmosphere that causes global warming and climate change.

In other words, clean solar-based H2 technologies not only produce hydrogen but also employ entirely renewable and abundant energy sources and raw materials: solar energy and water, respectively, which produce no CO2 emissions (Figure 1.13).

Chapter 1

 

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Demineralization

 

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Rivers

Oceans

 

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Heat Market

 

Energy (in. out)

 

Electricity Re-generation

 

Aerospace

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Hydrogen Production and Utilization

Hydrogen is widely employed in the chemical and petrochemical industries. The total world production of hydrogen as a chemical

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Figure 1.7 The only emission produced by Frauscher’s Riviera 600 hydrogen- powered boat is clean water; H2 is obtained cleanly by photovoltaic electrolysis of water.

(Photo courtesy of Fronius.)

constituent and as an energy source was valued at US$120 billion in 2010 (Figure 1.8).17 The two main applications are the production of ammonia (NH3), via the Haber process, which is used directly or indirectly as fertilizer, and hydrocracking, namely converting heavy petroleum sources into lighter fractions suitable for use as fuels (and in the de-sulfurization of middle distillate diesel fuel)...

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Hydrogen and Solar Hydrogen

1.1 Hydrogen: Structure and Properties

First produced by Robert Boyle in 1671 by reacting mineral acids with iron, hydrogen was recognized as a discrete substance by Henry Cavendish in 1766.1 Cavendish named the gas ‘‘flammable air’’ and further reported in 1781 that it produced water when burned. In 1783, Lavoisier reproduced Cavendish’s findings, formulating the mass con­servation law, and named the element ‘‘hydrogen’’ from the Greek for ‘‘water-creator’’.2

At standard temperature and pressure, hydrogen is a colorless, odorless and non-toxic diatomic gas with the molecular formula H2. It is the lightest (average atomic weight 1.007825 u for 1H) and most abundant chemical element (75% of the Universe’s elemental mass)...

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