The world's only trigeneration system - currently part of a three-year test operation in Southern California - could trigger a revolution in distributed hydrogen and electricity production, and open up a commercial market for hydrogen-fuelled cars.
On 3 November, Dr Scott Samuelsen was honoured at a White House ceremony as a Champion of Change for his pioneering work on hydrogen power. He is director of the National Fuel Cell Research Center at the University of California in Irvine, which with partners, has created a sewage-to-hydrogen fuel cell plant.
As part of the process, Biofuel generated by waste treatment plant sewage is converted to zero-emission hydrogen fuel, which yields the equivalent of 70 miles/gallon in fuel cell vehicles.
“This is the epitome of sustainability, where we are taking an endless stream of human waste and transforming it to transportation fuel and electricity,” Samuelsen says.
At the heart of the sewage-to-hydrogen fuel cell plant is a 300 kW fuel cell, which produces hydrogen, electricity and waste heat. Its creation was spurred by 10 years of research funded by the U.S. Department of Energy (DoE). Air Products had begun a search in 2001 for a stationary hydrogen fuelling system for light duty vehicles, in Allentown, PA. On the other side of the country, in the National Fuel Cell Research Center (NFCRC), a search had also begun to generate hydrogen from biofuels for use in fuel cells.
Researchers at the two facilities soon became partners, and DoE agreed to fund early development with the aim of designing a hydrogen fuelling system that could be deployed in the field.
The multi-million dollar funding awarded to Air Products was for a multi-phase project, integrating the goals of Air Products and those of NFCRC in Irvine, says Ed Heydorn, business development manager for Hydrogen Energy Systems at Air Products. DoE suggested anaerobic digester gas as a fuel and this led to more partners joining the project.
The team grows
First, Samuelsen introduced Fuel Cell Energy, headquartered in Danbury, CT, to Air Products. Tony Leo, vice president of technology at Fuel Cell Energy, explains: “we got involved about two and a half years ago [early 2009]. We had been looking at extracting hydrogen from fuel cells for 10 years.” Teaming up with Air Products allowed the company to apply what they had been learning.
Next, the partners selected the Orange County Sanitation District in Fountain Valley, CA, near UC, Irvine, as the site for a fuel cell-to-hydrogen system; it would be fuelled by digester gas generated in sewage holding tanks to produce hydrogen for the fuelling station which would be built nearby. Samuelsen says it took two to three years to arrange the location and create the design for the field system.
Construction of the plant, a fuelling station and the technology to clean the digester gas was funded by a US$2.7 million grant from the California Air Resources Board in 2008. An additional US$750,000 was provided by the South Coast Air Quality Management Board.
Purification essentials
A fuel cell cannot handle any biofuel, including digester gas, without a purification system to remove contaminants. A digester gas skid was designed and constructed to filter and remove contaminants and clean the fuel. This technology is commercially available from several vendors, Samuelsen says, but “it is still an evolving and challenging technology.” The challenge lies in the variability of the biogas itself, from application to application.
Fuel cells, in normal operation, reform a fuel such as natural gas, by mixing it with steam at high temperatures causing a reaction in which hydrogen atoms are split off each methane molecule. The products are water and hydrogen. In the high temperature fuel cells manufactured by Fuel Cell Energy, this reaction occurs internally. Lower temperature fuel cells used in cars and other small applications use external reformers.
The OCSD fuel cell-to-hydrogen plant is not the first to use biogas to generate hydrogen. Two other plants in California, the Sierra Nevada Brewery and Gill's Onions use the biogas derived from plant waste, which is then converted to hydrogen in fuel cells to generate electricity consumed in each plant. They are strictly cogeneration plants.
Sierra Nevada Brewery installed a 1 MW fuel cell system (also manufactured by Fuel Cell Energy) that supplies power and heat to the brewery. The waste heat is used to produce steam for boiling the beer and other heating needs. Gills Onions in Oxnard, CA, tired of trucking its onion waste to fields, decided to put it to work. It found a company, Biothane, to design an anaerobic digester for onion juice that would produce methane.
The company then purchased two Fuel Cell Energy 300 kW fuel cells that now convert the methane to hydrogen to produce electricity for the processing plant.
More fuel increases efficiency
The breakthrough for the fuel cell-to-hydrogen system came when Samuelsen and his team discovered that increasing the amount of digester gas going into the fuel cell beyond what was needed to generate electricity would produce excess hydrogen. The excess hydrogen was more than the fuel cell stack could digest and it could be siphoned off into storage tanks for vehicle fuelling.
There was a payoff with this discovery, Samuelsen says. Increased hydrogen production stimulated distribution across the fuel cell stack, and increased the efficiency of electrical production.
Once the system that was to be deployed at the OCSD was designed, Fuel Cell Energy ran an operational test for 9 months at its factory in Danbury, CT. The fuel cell operated on natural gas, since the company did not have access to biogas: “We shook out the 300 kW fuel cell plant for a few months,” Leo says. Upon successful completion of the test, the fuel cell plant, being modular, was shipped on 6 skids to Fountain Valley. Local contractors installed it under the direction of Air Products acting as the prime contractor.
Construction began in Fountain Valley while the shop test was still running. But there was a 6-month wait for the digester skid to be selected and built, Samuelsen says. Construction was completed in May 2011 in just over a year. The plant was commissioned the following August, in a ceremony that included, among many officials, US Congressman Dana Rohrabacher who represents the area.
Performing well
Jeff Brown, a Senior Engineer at the OCSD, and the Project Manager for the fuel cell-to-hydrogen project, says the core technology is performing well. It is operating alternately on digester gas and natural gas. The only hitch is getting the electrical output synchronised with the plant's micro-grid to smooth out voltage fluctuations, he concedes: “Any type of generation technology experiences this,” he notes.
The long term performance of the fuel cell-to-hydrogen system will be studied, particularly the digester skid performance throughout the three-year operational test.
Currently, staff are concentrating on balancing the electricity produced with hydrogen production, as the efficiency of the system depends on this, Brown explains. Furthermore, Samuelsen has conducted computer modelling of various balancing schemes, for comparison with operating performance over the next three years.
Brown adds that the goal is to run the system on digester gas only, but that this is difficult because digester gas flow from the waste water tanks may be interrupted, or equipment maintenance may require a switch to natural gas.
Fully automated
The system is totally automated – but an OCSD operator checks the system once per shift and it is monitored by Air Products personnel in Allentown 24 hours a day.
Air Products' Heydorn says the main challenge and most interesting part of the project has been developing the operating system and programme logic for the automated system that would monitor and control hydrogen production, turning it on and off to meet demand.
Only the beginning
Brown says the 300 kW system “is a small drop in terms of electricity contribution. Once the feasibility of the technology is thoroughly tested, the plan is to go to a larger system, perhaps 1 MW. Expansion of the plant is linked to the development of the infrastructure for hydrogen fuelling stations.”
Pinakin Patel, Fuel Cell Energy's project manager for the fuel cell-to-hydrogen project adds that the OCSD site has the potential to expand to 20 MW, and produce 20,000 pounds of hydrogen/day, enough to fuel 2000 cars per day. The current hydrogen production produces 250 pounds/day, enough to fuel 25 cars per day.
Patel also points out that the 250 kW of electricity produced by the system could be diverted from being fed into the micro-grid, and instead be used charge electric vehicles. Tony Leo adds that, “the success of the project proved that we can make any amount of hydrogen we need, based on laboratory calculations.”
Pressing the accelerator
While the fuel cell-to-hydrogen plant has been operating since August, retail customers are not yet able to pump hydrogen. Agreements are still being completed with car manufacturers, a process that is challenging due to the various entities involved, Samuelsen says. Liability, indemnification and cost of fuel must to be covered – most likely by the car manufacturers.
Developing a commercial price for hydrogen, still in the early stage, is a job for the State and Samuelsen is working with state officials to accomplish this. Five major car manufacturers have announced plans to commercially manufacture hydrogen-fuelled cars by 2015, and this has provided real-world stimulus to the research: “When hydrogen vehicles become commercially available in 2015, pricing will become as user friendly as [petrol prices] are today,” Samuelsen hopes.
Of course, hydrogen fuelling stations need to be built, and Samuelsen's lab is developing tools to determine where - and how many - fuelling stations are needed to attract a large consumer market. The project uses a tool called STREET – a computational methodology looking at hydrogen production, emissions, and cost of energy, plus demographic data and economic status of local populations. The goal is to identify where stations could optimally be located within the State and around the country, to replace 15% of petrol stations.
Leo concludes that producing distributed hydrogen at municipal plants all across California makes sense: “I wouldn't be surprised [that] if California is successful at deploying hydrogen cars, other states would be interested.”
About: Lyn Corum is a freelance U.S. correspondent for Renewable Energy Focus magazine.