HYDROGEN’S SILVER BULLET?

Two organisations in the US are addressing the ‘green
hydrogen’ conundrum

The U.S. Department of Energy’s National Renewable Energy Laboratory and Xcel Energy have launched a ground-breaking two-year project aimed at using electricity generated from wind turbines to produce and store pure hydrogen, thus offering what may become a significant new template for future energy production. Don C. Smith considers the project, and delves into what implications this could have for the oft-dreamt about hydrogen economy.

Despite considerable optimism (and perhaps put more simply,
hope) about the future development of a hydrogen economy, a key unresolved questions remains: how to produce hydrogen in a clean, efficient way. Using natural gas or coal – or even nuclear power – to produce hydrogen, in many ways defeats the purpose of moving towards a future powered by hydrogen. In the first two instances, greenhouse gases are emitted in the process of producing the hydrogen. In the last case, nuclear waste is generated.

Hydrogen, while the most common element in the universe, is not found in its pure form on earth and must be either electrolyzed from water, or stripped out from natural gas, both of which are energy-intensive processes that result in greenhouse gas emissions.

Moreover, while wind energy seems perfectly suited to help ease the need for fossil fuel based electricity, wind farms only generate electricity when the wind is blowing. And the wind only blows about one-third of the time in the U.S. and often at night when the need for power from the electricity is less in any case.

This creates the need for backup generation, which is usually fossil fuel based. Consequently, the goal of producing hydrogen without generating greenhouse gas or other harmful by products, and then using the hydrogen later to feed the
electricity grid, has been seen as a promising– albeit difficult – dream. One of the world’s foremost energy think tanks, the Colorado-based Aspen Institute (AI), has gone on record to say, “as a nearlyideal energy carrier, hydrogen will play a
critical role in a new, decentralized energy infrastructure that can provide power to vehicles, homes, and industries.” But the
AI also cautions that the process of making hydrogen with fossil fuel-based power can involve the emission of significant
levels of greenhouse gases.

Launch of a new demonstration project

In December, the National Renewable Energy Laboratory (NREL) and Xcel Energy, a major U.S. electricity and natural
gas company with operations in eight western and Midwestern states, unveiled a unique prototype facility – located at NREL’s Wind Technology Center near Denver, Colorado – aimed at addressing these questions and helping provide research results about the “wind to hydrogen” challenge. The importance of the project was underscored by the attendance
at the announcement ceremony of several high-ranking Colorado politicians including U.S. Senators Wayne Allard, a
Republican, and Democrat Ken Salazar; as well as Democrat U.S. Rep. Mark Udall, who co-chairs the U.S. House of Representatives’ Renewable Energy and Energy Efficiency Caucus.

Richard D. Kelly, Xcel chairman, announced, “today we begin using our cleanest source of electricity – wind power – to create the perfect fuel: hydrogen. Converting wind energy to hydrogen means that it doesn’t matter when the wind is blowing since its energy can be stored on-site in the form of hydrogen.” And he added, “by marrying wind turbines to hydrogen production, we create a synergy that systemically reduces the drawbacks of each. Intermittent wind power is converted to a stored fuel that can be used anytime, while at the same time offering a totally climate-friendly way to retrieve hydrogen, to power our homes and possibly cars in the future.”

Dan Arvizu, NREL director, said the US$2 million project with Xcel “allows our researchers to compare different types
of electrolyzers and work on increasing the efficiency of a wind-to-hydrogen system. And it has the potential to point the way to a completely emissions-free system of making, storing, and using energy.”

Project description

The demonstration project facility links two wind turbines to electrolyzers – devices that pass the wind-generated lectricity
through water to split the liquid into hydrogen and oxygen. The resulting hydrogen can be stored and used later to
generate electricity from either an internal combustion engine turning a generator or from a fuel cell. In either instance, the
only by-product is water. The NREL site will include: a building that houses the electrolyzers and a device to compress the
hydrogen for storage; four large tanks to store the hydrogen; a generator run by an engine that burns hydrogen; and a control room where computers will monitor all steps of the process.

The demonstration project will use two wind turbine technologies – a Northern Power Systems 100 kW wind turbine and a Bergey 10kW wind turbine. The energy from the 10kW wind turbine will be converted from its ‘wild’ alternating
current (AC) form to direct current (DC), and then used by the electrolyzer stack to produce hydrogen and oxygen from water.

Meanwhile, the energy from the 100kW wind turbine will be captured from its existing controller, which already powers a
DC bus of nearly 800 volts. That voltage is too high for the electrolyzer stacks, and new power electronics will be designed to make the necessary conversion.

Two proton exchange membrane electrolyzers from Proton Energy Systems and one Teledyne HMXT-100 alkaline electrolyzer will be used to split water into hydrogen and oxygen gases. Finally, the hydrogen will be compressed and stored. A hydrogen internal combustion engine (or a fuel cell) will convert it to electricity to be put on the utility grid during peak demand hours.

The entire demonstration project will reveal integration and operational issues as well as identify opportunities for improvement and other potential benefits.

NREL and Xcel expect to release a public update on the project’s operation in the summer. Results of the project, which will also run through 2008, will be shared with other utility companies interested in hydrogen’s future role in the
utility industry.

NREL’s assessment of the project Benjamin Kroposki, senior project manager at NREL, notes that among other things the project “addresses the variable nature of wind power, creating a ready source of electricity for periods when the wind isn’t blowing or the demand for electricity is high. This will provide consistent support of the electric grid during peak demand periods via off-peak storage of hydrogen.”

From NREL’s perspective, the project has two unique aspects. First, the project will study how to achieve efficiency gains
through a unique, integrated AC-to-DC and DC-to-DC power electronics-based connection between the wind turbines and the electrolyzers.

“These should reduce duplicative components in the wind turbines and electrolyzers to reduce cost and increase overall
system efficiency,” Kroposki said. Moreover, the project allows the comparison of multiple electrolyzer technologies to gauge their efficiencies, as well as gauge their ability to be brought on- and off-line quickly.

NREL hopes to show significant cost and efficiency gains at the integrated wind-hydrogen system level, Kroposki explained. “Xcel is a key partner in this since utilities can have a big impact on how many of these types of systems are installed. This project will be a success if based on the testing results it can be scaled up to the megawatt size wind turbines and electrolyzers,” he said.

Utilities’ interest in wind to hydrogen

Meanwhile, Frank Novachek, director of corporate planning for Xcel, says there is considerable interest among utilities in the
renewables to hydrogen business model. For instance, he noted that his own utility’s geographic operations are well suited to explore the underlying business issues. “Xcel is right
in the ‘sweet spot’ for renewables,” Novachek said, while pointing to the significant wind and solar resources in the midwest, southwest and Texas, all areas where Xcel operates.

There are wind to hydrogen demonstration projects throughout the world, Mr. Novachek said, but the key for Xcel is to study the “integration” of the systems necessary to do the process in a more efficient and effective manner. “We are trying to understand how the systems will work together and to optimize the overall efficiency of the entire system,” he said.
Mr. Novachek is also pursuing the possibilities associated with hydrogen through another group – the Hydrogen Utility Group (HUG) – that consists of 13 North American utilities as well as an electricity utility in South Korea. HUG, which is sponsored by the Department of Energy, the National Hydrogen Association,
and the Electric Power Research Institute, is examining a range of utility-related business opportunities.

More specifically the mission of HUG, which Mr. Novachek chairs, is to accelerate utility integration of hydrogen-related
business applications through the coordinated efforts of its members. In the short term, HUG is particularly interested in
exploring the use of electrolysis to produce hydrogen. “There is a whole gambit of diverse [utility] interests in the hydrogen space that utilities can look at,” he said. “We are trying to find the common interests.”

Need for an ‘Apollo Program’

The interest in wind-to-hydrogen has attracted considerable attention, including from American atmospheric scientist Mark Z. Jacobson at Stanford University in California. Mr. Jacobson advocates establishing an ‘Apollo Program’ – referring to the 1960s U.S. commitment to put a man on the moon before the end of the decade – to promote the generation of electricity from wind and then using that electricity to produce hydrogen.

Mr. Jacobson has said, “If you want to encourage hydrogen and [wind-produced] hydrogen, then you need to undertake an Apollo Program, because even though the cost of a new wind turbine averaged over a long time is similar to a new coal
or natural gas power plant, there’s no incentive to replace these other sources with wind.”

We will be watching the development of the project with interest.

About the author

Don C. Smith teaches Comparative Environmental Law at the
University of Denver College of Law. He can be reached at:
dcsmith@law.du.edu or on tel: +1 720 936 8465