Thursday, February 22, 2007

Pebble bed reactors can supply hydrogen for power

The hydrogen economy is a futuristic vision of our society using hydrogen for vehicle fuel. Hydrogen can burn in an internal combustion engine creating only water vapor, H2O, which is nonpolluting and does not contribute to global warming.

However, hydrogen is a very reactive element and on earth hydrogen is bound up in molecules, principally water, H2O. To create pure H2 the hydrogen must be separated from the molecule, requiring energy. Today hydrogen is produced by electrolysis, using electrical energy. Hydrogen is best viewed as an energy storage system; energy is absorbed to create hydrogen and later released when the hydrogen is burned.

The pebble bed reactor is a high temperature helium gas cooled nuclear reactor. The 950 degree Celsius heat can be used to disassociate water into hydrogen and oxygen. This is substantially hotter than the temperatures reached by today's boiling water and pressurized water nuclear reactors. Two chemical processes show promise for commercial scale production of hydrogen: (1) high temperature electrolysis, and (2) the sulfur-iodine cycle, which is pictured in the schematic diagram above.

So the pebble bed reactor, with high temperature disassociation of water, can be a safe, clean source of power for the hydrogen economy.

But one of the problems of the hydrogen economy is that the storage and transportation of highly reactive hydrogen is extremely difficult. Hydrogen makes steel tanks brittle. Liquefied hydrogen must be kept cold (-253 degrees C), and the liquefaction process is energy intensive. Hydrogen can be compressed and stored in strong tanks at room temperature, but the pressures must be very high and the pressurization process is energy intensive. The H2 hydrogen molecule is so small it permeates containers and leaks out.

Indy 500 race cars run on methanol

Nobel prize winning chemist George Olah has proposed a more practical system he terms the methanol economy. Methanol can be used as a vehicle fuel. Methanol, H3COH, is readily created by combining H2 with recycled CO2 captured from existing coal-fired power plants. Methanol burns to form H2O and CO2, but the process is carbon-neutral because the CO2 would have been released into the atmosphere at the coal-fired power plant.

There will be enough CO2. US coal-fired power plants will continue to produce CO2 for a century even if they are replaced by one 100 megawatt PBR per week. CO2 comprises 0.06% of air. Later on in this century we will be able to glean CO2 from the atmosphere, perhaps using nanotechnology to create advanced membrane filters. In this way methanol fuel can remain carbon-neutral.

The great advantage of methanol over hydrogen is that methanol can be transported and stored using the existing pipelines, storage tanks, tanker trucks, and fuel stations used for gasoline, with minor modifications. Methanol can be burned as fuel in an internal combustion engine. Indianapolis 500 race cars have used methanol since 1964 because it is safer than gasoline in an accident; methanol is not as explosive as gasoline.

Beyond Oil and Gas: The Methanol Economy
, by George A. Olah, Alain Goeppert, and G.K. Surya Prakash, also discuses related concepts, such as the direct methanol fuel cell that could replace the internal combustion engine. For example, dimethyl ether, CH3OCH3, is a nontoxic, noncorrosive chemical that can be used a fuel for diesel engines.

Chemists and chemical engineers can develop processes to produce all the common hydrocarbons we now derive from petroleum. These chemical processes rely on an inexpensive, plentiful supply of hydrogen, which can be created from water using the high temperatures of the pebble bed reactor.

The pebble bed reactor can be a source of carbon-neutral fuel for vehicles.

Friday, February 16, 2007

Corn ethanol energy is a delusional diversion

Ethanol from corn is being hailed as a carbon-neutral fuel for automobiles. The CO2 emitted from from ethanol combustion is balanced by CO2 absorbed in growing the corn. Corn ethanol is also promoted as reducing US dependence on imported petroleum for gasoline.

It takes a lot of energy besides sunlight to produce ethanol. Energy is needed for transportation, fertilizers, fermentation, and refining. A Cornell University study by Professor David Pimentel claimed that the energy released by combustion of corn ethanol is less than the energy used to create it. The US Department of Agriculture is more optimistic, estimating that 100 BTU of energy is expended to create 134 BTU of corn ethanol.

This chart is from, which has summaries of many such studies, including a July 2006 report from the National Academy of Science.

To make ethanol without the foreign fossil fuel, nuclear power, and coal, one might use renewable ethanol energy instead. The production process would consume 3 of every 4 gallons produced. Let's compute the farmland to satisfy US transportation fuel needs with ethanol.
28 quadrillion [10^15] BTU annual US transportation fuel
divided by 76,000 BTU per gallon of ethanol
divided by 2.5 gallons of ethanol per bushel of corn
divided by 25% to account for production energy consumed
divided by 148 bushels of corn per acre
equals 4 billion acres of farmland.
Total US farmland is only 1 billion acres. About 10% is now used for corn. Already the increasing fuel demand for corn ethanol is raising prices for cattle feed and reducing exports.

Ethanol is not needed in gasoline for environmental reasons, either. The US had required 2% oxygen content in reformulated gasoline to reduce smog-causing NOX (nitrogen oxides) tailpipe emissions in heavily populated areas. The oxygen was supplied by supplementing gasoline with 11% MtBE (Methyl tertiary Butyl Ether) or 6% ethanol. MtBE use has ended after leakage from underground gasoline tanks into groundwater, and ethanol use has increased to replace MtBE. However NOX emissions are properly controlled by modern fuel injection engines, so the ethanol oxygenate is not needed, and the Energy Policy Act of 2005 eliminated this requirement.

Corn ethanol is subsidized at 51 cents/gallon by taxpayers. Corn ethanol is promoted very effectively by the corn lobby. Citizens and political leaders have been deluded into believing that corn ethanol is a solution to the US energy crisis, but it is not. It is expensive, displaces food crops from farmland, and continues fossil fuel use.

Cellulosic ethanol, derived from the abundant fibers of plants rather than the starches and sugars of seeds, may be much more productive of ethanol in the future. Research and development into this technology is ongoing, with funding from the US federal government, state governments, and venture capitalists. Success is not certain, and practical, economical, industrial-scale production of cellulosic ethanol is 15-20 years into the future.

Corn energy ethanol is an expensive, delusional diversion of US energy policy. It diverts public attention, money, and national resources away from solutions that can really address the issues of global warming, energy costs, and foreign oil addiction.

Pebble bed reactors can solve the problem that corn ethanol can not -- production of inexpensive, carbon-neutral vehicle fuels. Future posts will show how.

Friday, February 9, 2007

PBRs can halve global warming CO2

In February, 2007, the Intergovernmental Panel on Climate Change published the report Climate Change 2007 which gave further evidence that (a) the climate is warming, and (b) human activities are part of the cause. Most of the press coverage focuses on the warming, the shrinking glaciers, starving polar bears, and rising oceans. The evidence that man-made greenhouse gasses actually cause the global warming is harder to communicate. The report quantitatively models the contributions of various human-caused components, such as CO2, N2O, and CH4, of which CO2 is the largest.

To my mind, the clearest evidence is the above chart, published by NASA. Over the last 170,000 years atmospheric CO2 levels and global average temperatures have changed in tandem. The two graphs are too similar to be attributed to chance. The frightening aspect, at the top right, is the sudden increase in CO2 levels of the last decades. This portends a similar increase in temperatures. Pebble bed reactors can decrease future CO2 emissions. Here's how.

Quads of fossil fuels burned annually in the US

One quad is one quadrillion [10^15] BTU per year. The first post in this blog has a DOE energy flow chart indicating consumption of 55 quads of US fossil fuel plus 29 quads of imported petroleum. These 84 quads are burned, producing CO2. US coal, primarily for electric power, accounts for 23 quads of this. We can begin to cut CO2 emissions by replacing coal electric power with nuclear electric power.

The previous post showed how pebble bed reactors can be built in factories, much as Boeing builds airliners. Boeing builds at least one airliner per day. Let's suppose we build just one PBR module each week to replace coal-burning electric power. The thermal efficiency of a coal power plant is about 33%, so it takes 3 times as much energy in as it sends out. Here's how many quads of fossil fuel one 100 megawatt PBR module can save.
100 x 10^6 watt [1 megawatt = 106 watts]
x 3.4 BTU / watt hour
x 24 hours / day
x 365 days / year
x 3 [to account for 33% efficiency]
x 1 quad / 10^15 BTU / year
= 0.0089 quad
So building one PBR module per week displaces 0.0089 x 52 = 0.46 quads of fossil fuel energy every year thereafter. The bar chart above illustrates the concept. The displaced quads can be from coal, crude oil, or natural gas.

Deploying pebble bed reactors can reduce the US-produced CO2 that contributes to global warming, by half, in this century.

Saturday, February 3, 2007

Technology has improved since 1970s nukes

Three dimensional computer aided design technologies help designers lay out and test designs for products ranging from tiny heart stents to huge airliners. Above is another presentation of the conceptual PBR layout done by MIT researchers using such tools. Some of the Seabrook cost overruns were due to design errors, which caused piping runs to collide during construction. With today's 3D-CAD such expensive errors can be prevented.

Design technologies have improved phenomenally during the three decades since today's operating US nuclear plants were designed. Just consider information technology. The designers of today's nukes didn't have personal computers, nor Microsoft software, nor data base management. Nor was there email, optical fiber, the internet, nor search engines.

We all know that computer speeds have been doubling ever 2.5 years or so. Computers are many thousands of times more capable than those of 30 years ago. The impact on engineering and simulation is phenomenal. Scientific computing now lets us better understand the origins of the universe, and the structure of matter. Finite element analysis, together with 3D-CAD, breaks solid models down into thousands of sugar-cube-like elements and simulates all inter-element flows of heat, electricity, fluids, stresses, etc. to predict the behavior of the whole. Software products like Fluent add dynamics and multi-phase characteristics. MATLAB does mathematics for engineers and economists. AutoCAD, Pro/E, and Catia compete to offer designers better and better 3D design, modeling, simulation, mockup, production, and testing tools.

Manufacturing management has also progressed since the 1970s with Statistical Process Control, GE's 6-Sigma process management, Total Quality Management, Good Manufacturing Process, and ISO 9000. Materials Resource Planning evolved to become company wide, to manage purchasing, production, scheduling, shipping, quality management, accounting, and management reporting, in a single, integrated, real-time management system. Enterprise-wide information systems like SAP and Oracle provide leading companies with integrated, real-time, operational control and management. Manufacturing management systems help keep Boeing from delaying airliner delivery for lack of a single one of it's 500,000 different parts, for example.

A decade ago Boeing Aircraft received the Smithsonian-Computerworld award for the Boeing 777. It was the first example of such product design and development with computer assisted design and engineering tools continuing through computer-managed manufacturing. When the airliner assemblies were brought together they fit! The 777 was the first airliner to fly without half a ton of shims.

Production lines benefit cost and quality

A standardized design and construction process will enable the production of PBR units rapidly and economically, with high quality standards. Earlier US nuclear power plants were individually designed, licensed, and constructed. In France, where nuclear plants supply most of the country's electric power, standardized designs are the rule. Standardizing the design and production process for PBRs will lead to many benefits.

  • One type-certification for many plants
  • Reduced costs
  • Faster delivery times
  • Strong quality controls
  • Continuing product improvement
The PBR production process can emulate Boeing's.

  • Production line
  • One unit per day
  • Standardized units
  • Computer-aided design, engineering, manufacturing
  • $ 100-200 million per unit
  • Life safety paramount

In summary, since US nuclear power plants were built in the 1970s, information technology and manufacturing management have improved dramatically, promising even safer nuclear power in the future.