By Karl Hill
A Holistic Approach to Solving Energy Needs
Fuel cells. Biofuels. Solar and wind energy. Microgrid distribution systems. Meeting the nation’s energy needs in the future will involve a broad range of technologies, and New Mexico State University researchers are at the forefront of some of the most intriguing innovations.
Civil engineering professor Nirmala Khandan and his colleagues were already hard at work on a research project to produce hydrogen from cattle manure when he decided to strike off on yet another energy-production trail.
“We are now focusing on producing electricity directly from the waste, without methane or hydrogen or any intermediate fuel,” Khandan said. “We are very excited about it.”
With an interdisciplinary research grant from the university’s research office as seed money, Khandan began working with chemical engineer Shuguang Deng and Geoffrey Smith, an environmental microbiologist in the College of Arts and Sciences, to develop a bench-scale microbial fuel cell (MFC) to evaluate the feasibility of producing electricity from cattle manure. If successful the technology would solve a major environmental pollution problem while adding a new energy source to the nation’s portfolio.
“We started in December and already we have got the reactors going and we are producing electricity,” he said.
The MFC consists of two compartments with a membrane between them. In the first compartment, known as the anodic compartment, microorganisms in the organic waste oxidize a substrate such as glucose under anaerobic conditions. This microbial reaction liberates electrons and protons. The protons flow through the proton exchange membrane into the second chamber, known as the cathodic compartment, while the electrons flow through an external electrical circuit. The cathodic compartment is maintained under aerobic conditions, where oxygen is reduced to water.
So far, the power outputs are small, but the process has a number of advantages over other biological energy conversion technologies, Khandan said. MFCs can operate at high overall efficiencies, even at ambient temperatures. Their gaseous products do not require any treatment before discharge. They do not require any energy input. And because they have no mechanical components, they are expected to be robust and reliable.
On the issue of efficiency, Khandan offered this comparison: The process of obtaining methane from biomass and using it as a fuel to generate electricity has a maximum efficiency of 35 percent. Obtaining hydrogen instead and using it in a fuel cell to produce electricity boosts the efficiency to 65 percent. With microbial fuel cells, “we are getting about 80 to 90 percent.”
“The potential is there,” he said. “It will take five years to make it practical in real applications. We are perfecting the science now.”
Khandan’s latest project typifies the eclectic, multidisciplinary approach NMSU researchers are using to help the nation address its energy challenges. Projects range from finding ways to make hydrogen fuel cells economical to harnessing wind and solar energy and tying it in to the electric “grid.”
“We believe it is important to deal with complex energy issues in a holistic manner,” said Abbas Ghassemi, director of NMSU’s new Institute for Energy and the Environment in the College of Engineering, which is the focal point of much of the university’s energy research. “In this way we can help to meet our nation’s energy needs while conserving natural resources and protecting the environment.”
Economical methods of producing hydrogen are critical to the success of hydrogen fuel cells, a promising alternative to fossil fuels for powering vehicles and generating electricity for other needs. The same researchers who are collaborating on the microbial fuel cell project – Khandan, Deng and Smith – are making progress on that front as well.
Recent research has demonstrated that hydrogen can be produced economically from organic wastes in liquid and slurry form. The NMSU researchers, funded by a $360,000 grant from the National Science Foundation, are developing a system for producing hydrogen from a solid waste – cattle manure.
“Dairy waste is the model we are using, but the technology can be applied to any biomass,” Khandan said. “We have engineered the process to produce hydrogen instead of methane, because hydrogen is a much better fuel than methane in several aspects.”
Methane production is the natural result of microorganisms digesting organic matter in biomass such as manure. “But halfway through the process, hydrogen is produced,” Khandan said. “The hydrogen is consumed by the microorganisms to produce methane. We want to stop the process – let them go until they produce hydrogen and stop it.”
The researchers are developing a twostage reactor that incorporates a unique hydrogen-selective membrane for rapid and efficient separation of high-purity hydrogen. Since the project started in July 2006, they have successfully produced hydrogen from a solid waste stream using a prototype reactor. A provisional patent and a trademark have been filed.
Purifying and storing hydrogen efficiently also are crucial to making hydrogen fuel cells practical as an energy source. Shuguang Deng, Martha Mitchell and Paul Andersen, all of the university’s Chemical Engineering Department, are developing and modifying new materials known as metal-organic frameworks (MOFs), which show promise for these applications.
Their work is funded with a $576,000, three-year grant from the Army Research Office.
“The Army has a need for a portable power supply in the battlefield that will last about one week,” Deng said. “They are using batteries that are quite expensive and heavy, and they don’t really have the capacity to be used for seven days. Typically it’s less than three days, so they have to carry a lot with them.”
Adsorption – the process that occurs when a gas or a liquid accumulates on the surface of a solid material – appears to be an effective method of separating, purifying and storing hydrogen. MOFs, which are porous materials with large surface areas that can be modified to be attractive to hydrogen, “look very promising for hydrogen purification and storage for fuel cell applications,” Deng said.
But because MOFs are new materials, their characteristics are not well known. Deng’s group is working toward a comprehensive understanding of the adsorption and diffusion of small molecules in MOFs. Computer modeling and simulations will provide insight into the nanoscale behavior and separation capabilities of MOF materials. In addition, the ARO grant has made it possible for the university to purchase an expensive instrument needed to measure the hydrogen adsorption in MOFs at high pressure.
“It will provide a direct measurement of how much hydrogen has been adsorbed in that material, and it can also show us how fast the hydrogen can be adsorbed, which is very important,” he said.
NMSU researchers are collaborating in several projects investigating the use of algae for the biodiesel production. At the university’s Agricultural Science Center in Artesia, for example, a project led by the Center of Excellence for Hazardous Materials Management (CEHMM) of Carlsbad is looking at ways to grow and harvest certain species of algae, which produce a much higher level of oil than more traditional feedstocks such as soybeans or canola.
New Mexico’s mild climate, abundant sunshine and large reserves of brackish water make favorable conditions for algae farmers, said Steve Loring, assistant director of NMSU’s Agricultural Experiment Station.
Another new initiative, supported by the New Mexico Technology Research Collaborative, aims to develop an integrated bioenergy processing system that can utilize waste streams from dairy and other agricultural industries for the production of energy, biofuels and other useful products such as fertilizer. Growing algae in the waste streams for biodiesel fuel is one of the project’s goals. Shuguang Deng of Chemical Engineering and Victor Cabrera of Extension Animal Resources are collaborating with researchers from the University of New Mexico, Sandia National Laboratories and a private sector partner, Ag2Energy.
Solar and wind power The U.S. Department of Energy’s new Solar America Initiative is likely to mean an increase in work for the Southwest Technology Development Institute (SWTDI), a component of the Institute for Energy and the Environment.
“This will be a new chapter in DOE’s promotion of the development of solar energy technologies,” said SWTDI Senior Program Manager Andy Rosenthal. “It’s part of a large and forward-looking public-private effort to promote environmentally clean and cost-effective energy technologies.”
SWTDI, a renewable energy research and development center, operates the DOE’s Southwest Region Experiment Station and has been funded primarily by the energy department for the past 27 years.
One of its key roles today is the development of codes and standards for photovoltaic systems – standards that protect the public while facilitating new technology.
“If people are going to be building with these products and putting them on their roofs, they need to be safe, they need to be inspected, and they need to meet certain requirements,” Rosenthal said.
Another area of expertise is instrumentation and data analysis. “Throughout our history, DOE has called on us to go out and measure the performance of PV systems, and other energy systems,” he said. “They call on us as a qualified and impartial university- based institute to provide these kinds of third-party assessments.”
Working with the National Renewable Energy Laboratory in Colorado, Sandia National Laboratories and the Florida Solar Energy Laboratory, SWTDI has helped to develop the test and evaluation requirements to support the Solar America Initiative. The DOE in March announced the selection of 13 industry-led solar technology development projects for negotiation for up to $168 million in funding, subject to Congressional appropriations.
In support of wind energy developments, SWTDI has the capability to measure and assess wind resources in a given area. “We have wind resource assessment towers installed in the Organ Mountains for the NASA White Sands Test Facility and we’ll be putting some up at Fort Bliss,” Rosenthal said.
SWTDI also is collaborating with NMSU’s Clovis Science Center to assess the potential for commercial wind energy production in east-central New Mexico.