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Basic Drives PUBLIC ACCESS

Imagine an Economy in Which Energy is Taken from a Range of Sources and Delivered in only a Couple of Convenient forms. These people do.

[+] Author Notes

Executive Editor

Mechanical Engineering 123(12), 51-55 (Dec 01, 2001) (5 pages) doi:10.1115/1.2001-DEC-4

This article discusses various technological innovations to develop energy infrastructure that could result in fewer carbon emissions. A number of technologies are in development with emissions reductions in mind. They range from gasification of coal and other hydrogen-bearing fuels to an eventual transition to a hydrogen economy. Advocates of an economy run on hydrogen observe that it makes the primary source of fuel irrelevant. Hydrogen can be extracted by various processes from natural gas, petroleum, coal, possibly even wood chips left by the sawmill, just like syngas. Processes based on reforming fossil fuels represent the most economical way to produce hydrogen today and account for 95 percent of the hydrogen produced worldwide. Deregulation of electricity markets has spurred activity to make nuclear reactors more competitive. Designs are in the works to make plants cheaper to build and operate, generally by making them smaller and simpler, ideally so they can be composed of factory-built modules. The Canadians, meanwhile, are working toward the next generation of their Candu reactor, with the aim of making it simpler and cheaper to build and run.

During a recent presentation in Argentina, Guillermo Celentano of Repsol YPF in Buenos Aires observed an essential truth of life: “We need energy, no matter the source from which it is obtained.” Celentano, who was speaking at the World Energy Congress, had written a paper that carried the prophetic title, “The XXI Century Energy Transformation.” He was one of many who were looking .ahead.

When energy forecasters start talking about the future of technology, they may describe cars powered by hydrogen fuel cells so their only emissions are heat and water. If they’re thinking in the long term, they may predict significant gains in power generation by renewables, especially sun and wind. For the nearer future, many are preparing for a resurgence of nuclear power, driven by simpler designs that aim to make reactors more competitive in deregulated electricity markets.

Wait a minute. Cities full of cars that don’t burn gasoline? Where are they going to get all that hydrogen?

Well, for one thing, by electrolyzing water. And where will the power come from to break down water into its elements? From wind, sun, and nukes.

Okay, maybe it’s not going to be so simple. But that was a sketch of the future that a listener could piece together front comments by Celentano, the resources manager for Repsol’s La Plata refinery, and a number of other speakers.

Actually, all the scenarios of the future see a broad range of energy sources for heating, power, and transportation. Sun, wind, water, and uranium will all play a role, but the familiar fossil fuels will predominate for decades at least.

The variety is necessary to meet rising demand. It is also desirable, because it lets the world economy avoid reliance on one or a few primary fuels.

The idea was summed up by Robert Schock, a senior fellow in the Center for Global Security Research at Lawrence Livermore National Laboratory in California. “Development of a range of technologies is the only insurance against uncertainties,” he said.

One plan that has been put forward to get all those different sources of energy to work together is to use them to generate electricity, which can be distributed to carry out any number of jobs. Converting fuels into the common form of hydrogen goes right along with that idea.

Acher Mosse, who represents the Electric Power Research Institute in Latin America and the Caribbean, referred to it as “the electricity-hydrogen infrastructure.”

According to Celentano of Repsol, hydrogen is not a primary source of energy because, although it is abundant in nature, it is not naturally found as a gas by itself. Instead, he concluded, “Hydrogen must be considered a versatile and new means to store energy.”

An industrialized world that generates electricity and fuels its vehicles on pure hydrogen has far fewer carbon emissions than our world has.

Bruce Sampson, senior vice president for strategic issues and planning for Canada’s BC Hydro, observed that hydrogen leaks don’t turn into oil spills, and since H2 can come from so many substances, it increases international energy security.

Although the final word is yet to come concerning the relationship, if any, between atmospheric carbon dioxide and global temperatures, the people who have to plan for the future of the energy business are taking a hard look at the issue. What most of them see is a world playing it safe and taking considerable steps to reduce the carbon it introduces into the air.

Hiroshi Urano, president of the International Gas Union, pointed out that this course follows the so-called “minimum regret” approach recommended by the World Energy Council after its previous big meeting in Houston three years ago. Urano had turned out to promote the product his organization represents, natural gas,' the fuel of increasing choice in an emissions-conscious world.

A number of technologies are in development with emissions reductions in mind. They range from gasification of coal and other hydrogen-bearing fuels to an eventual transition to a hydrogen economy.

The hydrogen fuel cell, for instance, has an attraction over its counterpart that uses natural gas. Even if the gas is pure methane, there’s one atom of carbon for every four of hydrogen.

With H2 there’s no carbon in, so there’s no carbon out. Theoretically, at least, the carbon is captured and sequestered during the reforming of hydrogen-bearing fuels. In the case of electrolysis, there is no carbon in water to begin with, and if the process is driven by renewables or nuclear power, there is none emitted from the electricity source either.

And farther upstream, if the factory that makes the hardware for the process is already running on pure hydrogen, there will be no carbon from its stack. And then there will be those hydrogen-burning trucks that carry the parts. You get the picture.

Advocates of an economy run on hydrogen observe that it makes the primary source of fuel irrelevant. Hydrogen can be extracted by various processes from natural gas, petroleum, coal, possibly even wood chips left by the sawmill, just like syngas. Unlike synthetic gas, however, the potential sources of hydrogen include water.

The argument continues that, because hydrogen comes from many sources, it adds to the flexibility of an economy. The ultimate sources of energy are almost invisible. If there’s trouble with one, production turns to another, and the hydrogen keeps flowing.

The scheme of Candu: Current reactors use heavy water and natural uranium. A slight fuel enrichment will permit using a mix of light and heavy water.

Grahic Jump LocationThe scheme of Candu: Current reactors use heavy water and natural uranium. A slight fuel enrichment will permit using a mix of light and heavy water.

An international group of authors wrote a paper on the pros and cons of handling hydrogen. Robert Harris and David Thatcher are with Advantica Technologies Ltd. in the United Kingdom; Yoshikiyo Asaoka is with Osaka Gas in Japan, and Jacques Saint-Just works for Gaz de France. Harris is also on the International Gas Union’s committee on gas utilization and power generation. Saint-Just and Asaoka are on the IGU’s hydrogen committee.

They reported, for instance, that hydrogen can travel more efficiently than electricity over long distances., more than 1,000 km. On the other hand, hydrogen would be more costly to transport than natural gas because of its lower volumetric energy density.

The current natural gas transmission system may be adaptable in practice to hydrogen. There is a potential problem with an embrittlement of parts from contact with pure hydrogen, but the authors predict that it can be overcome.

The dangers of transporting liquid or gaseous hydrogen are about the same as those for natural gas, they said, although characteristics of combustion differ.

They predicted that a transition to a hydrogen economy will be gradual and will start in niche markets.

Processes based on reforming fossil fuels represent the most economical way to produce hydrogen today and account for 95 percent of the hydrogen produced worldwide, the authors reported.

Although they consider electrolysis powered by renewables to be a worthy goal, they pointed out, “Hydropower is indeed the only renewable energy that represents today a significant fraction of the world energy supply.”

An artist's eye view of the next-generation Candu reactor: Atomic Energy of Canada Ltd. promises additional economies in capital and operating costs.

Grahic Jump LocationAn artist's eye view of the next-generation Candu reactor: Atomic Energy of Canada Ltd. promises additional economies in capital and operating costs.

According to Deborah Bleviss of the Inter-American Development Bank, one of the key weaknesses in the development of most renewables is “feast-or-famine funding.” It is an undercapitalized industry that can’t compete in international markets. Companies can’t hold on to their professionals, and turnover in ownership is high. “Money comes in usually only during a crisis,” she said.

Bleviss, the bank’s manager for a program called Sustainable Markets for Sustainable Energy, suggested that improvement could start with a commitment from governments to fund research and development over several years.

Deregulation of electricity markets has spurred activity to make nuclear reactors more competitive. Designs are in the works to make plants cheaper to build and operate, generally by making them smaller and simpler, ideally so they can be composed of factory-built modules.

Tim Abram, head of advanced fuels and reactor systems at the research and technology division of BNFL (a.k.a. British Nuclear Fuels pic), reported on some of those efforts.

One modular design is the pebble bed reactor, developed in Germany and now proposed for commercial application in South Africa by a group that includes BNFL. The reactor’s fuel consists of graphite pebbles, about 60 mm in diameter, which contain thousands of fuel particles. Helium passes through the bed to be heated before it moves on to compressors and, eventually, to a gas turbine that drives the generator.

Another modular reactor design called the AP600 has been approved by the U.S. Nuclear Regulatory Commission, although no construction permits have been issued in the States. Developed by BNFL’s subsidiary, Westinghouse Electric Co., the AP600 is a light water reactor designed to generate 600 megawatts. Westinghouse has applied for approval on a larger, 1,000-MW design called API000. In both cases, the plant design is simplified to reduce construction time and cost.

According to Abram and his co-authors in a technical paper, “The passive safety systems use only natural forces, such as gravity, natural circulation, and compressed gas to shut down and cool down the plant in the unlikely event of an accident. No pumps, fans, diesel generators, chillers, or other rotating machinery are used. A few simple valves align the passive safety systems when they are automatically activated.”

Valves are considered fail-safe because they require power to remain in their closed position. Loss of power opens them to their safety mode.

According to Westinghouse, the design of the AP600 requires 50 percent fewer valves, 80 percent less safety grade piping, 70 percent less control cable, 35 percent fewer pumps (with no safety grade pumps), and 45 percent less seismic building volume than other conventional reactors.

Modular design means that components are factory-made so plants are quicker to assemble. It takes four or five years “from first concrete to fuel loading” to build a conventional nuclear plant, Abram said. The AP600 is designed to go up in three years, the pebble bed reactor in two.

The Canadians, meanwhile, are working toward the next generation of their Candu reactor, with the aim of making it simpler and cheaper to build and run.

The Candu uses fission of natural uranium to heat heavy water, which is more efficient at slowing neutrons than is regular, or light, water. The name “Candu” derives from “Canadian,” “deuterium,” a heavy hydrogen, and “uranium.”

According to Romney Duffey of Atomic Energy of Canada Ltd., use of the slightly enriched fuel and a placement of the fuel channels closer together will combine for a number of cost-saving features. The process steam will no longer require 100 percent heavy water to operate at current efficiencies. The amount of heavy water may be reduced by a factor of 2Vi, replaced by light water. Duffey, principal scientist with AECL, said this change could save $100 million on a plant’s capital costs.

Less heavy water in the system will also make it possible to commission plants more quickly, Duffey said.

As the channels get closer together, the vessel that contains them gets smaller. This fits with the modular design of the Candu, which is another of its features designed for efficient construction and operation.

The uranium proposed for the new Candu will be enriched less than 2 percent, and so is expected to cost less than the fuel needed to run light water reactors, which need an enrichment of 3 to 4 percent.

 Energy Markets and Fingerprint Readers

Every three years, the energy world gets together to discuss issues of common interest touching on markets, technology, politics, and the future in general.

This year, the congress met in Buenos Aires, at the same time as a regional trade show, the Argentina Oil and Gas Expo.

The World Energy Congress brings together a truly cosmopolitan mix. Energy ministers and mad inventors mingle with the CEOs of global conglomerates. A few heads of state drop by for a speech or two.

Given the violence of recent world events, a concentration like that of big wheels and eccentric gears calls for tight security. It started with metal detectors and police officers searching bags at the entrance to La Rural, the exhibition complex that contained the expo and congress.

La Rural covers a goodly piece of ground. Coincidentally (or maybe not), it stands between the U.S. Embassy on one side and the city zoo across the street on the other.

Inside the exposition halls, members of the Argentine Federal Police roamed in their black flak jackets. They led large, happy dogs that wagged their tails and sniffed for explosives.

Police personnel, as well as civilian security people, were present in force at the door to the building where the congress met. Backing up the metal detectors at these doors were fingerprint readers.

The congress proceeded as planned.

The event is held under the auspices of the World Energy Council, which publishes a report, Survey of Energy Resources, at each congress. A look into the 2001 edition suggests that it was probably no coincidence that one of the principal cities of South America was chosen as the venue for this year’s gathering.

The continent sits on a healthy share of the Earth’s recoverable fuel reserves. It has more than 13 million tonnes (that’s metric tons, 1,000 kilograms or about 2,200 pounds apiece) of crude oil and natural gas liquids under the ground or offshore. That comes to nearly 10 percent of what has been found and deemed recoverable everywhere.

The total falls far short of the Middle East, which has about 65 percent the world's oil and liquid gas reserves, but it outranks everybody else.

The reserves in Venezuela alone exceed all of Africa’s. The country has more than 11 million tonnes; Africa has 10 million.

Venezuela is home to the Faja del Orinoco oilfields. Stretching over a vast area north of the Orinoco River, they contain about 1.4 billion barrels of oil, of which almost 300 million are currently considered recoverable.

South America's share of the world’s natural gas is modest, about 4 percent.

In his presentation during a session devoted to the market challenges of South America, Total Fina Elf’s chairman, Thierry Desmarest, estimated that the Atlantic basin holds about 80 percent of the world’s deep offshore oil. A slide behind him showed a map of the continent, highlighting the undersea oil fields wrapping around the shoulder of Brazil.

Among the challenges in Latin America, according to Desmarest, are the increasing difficulty of developing oil and gas resources.

Offshore drilling reaches into ever-deeper waters. And a separate challenge is transporting energy resources from where they are recovered to the markets where they are worth money. There are large reserves, but they are distant from consumer areas, Desmarest said.

Duffey and several colleagues pointed out in a paper that nuclear reactors can serve as a source of electrolytic power to produce hydrogen for use as a fuel without the emission of carbon dioxide and other suspected greenhouse gases.

Westinghouse’s AP600 reactor uses passive safety systems and modular construction for simpler design that is less expensive to build and quicker to commission.

Grahic Jump LocationWestinghouse’s AP600 reactor uses passive safety systems and modular construction for simpler design that is less expensive to build and quicker to commission.

Commercialization of another nuclear technology under study is much farther off. Its supporters don’t expect it to churn out a watt until the middle of the century at the earliest.

The reactor, based on the Russian-developed tokamak design, is a project of the European Council, Russia, and Japan, in pursuit of the elusive goal of fusion energy. The United States used to be a partner in the project, but withdrew.

The fusion reactor skips uranium fuel altogether. At its heart is a superconductive coil and a pressure vessel full of plasma heated to about 100 million°C. Inside the pressure vessel, deuterium and tritium, heavy forms of hydrogen, fuse to create helium, but when they do there’s an extra neutron left over.

As a result, there is a loss of mass, and the lost mass becomes considerable energy. Once fusion begins, the process is expected to generate enough heat to drive itself. The pressure vessel is lined with a blanket through which fluid, such as water, flows to be heated to drive a turbine. The superconductive coil, which must be chilled to a few degrees kelvin, is a solenoid whose field confines the superheated plasma.

The concept was tested a couple of decades ago using copper coils for the solenoid.

The consortium hopes to begin building a test reactor as soon as next year, according to Federico Casci, who works for the European Fusion Development Agreement at the Max Planck Institute for Plasma Physics in Munich.

He said that it could be up and running in 2011. The plan is to build a test unit that can put out 500 MW of fusion power, although none of it will be used to generate electricity.

“We are aiming to enter the energy scenario in the second half of the century,” Casci said.

Copyright © 2001 by ASME
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