By Nigel Hey
Sandia is moving into the demonstration phase of a novel gas turbine system for power generation, with the promise that thermal-to-electric conversion efficiency will be increased to as much as 50 percent — an improvement of 50 percent for nuclear power stations currently equipped with steam turbines, or a 40 percent improvement for simple gas turbines. It is also very compact, meaning that capital costs would be relatively low.
Research focuses on supercritical carbon dioxide (S-CO2) Brayton cycle turbines, which typically would be used for bulk thermal and nuclear generation of electricity, including next-generation power reactors (see Sandia Lab News, Dec. 5, 2008). The goal is eventually to replace steam-driven Rankine cycle turbines, which have lower efficiency, are corrosive at high temperature, and occupy 30 times as much space because of the need for very large turbines and condensers to dispose of excess steam. The Brayton cycle could yield 20 megawatts electrical (MWe) from a package with a volume as small as four cubic meters.
“This machine is basically a jet engine running on a hot liquid,” says principal investigator Steve Wright of Advanced Nuclear Concepts Dept. 6221. “There is a tremendous amount of industrial and scientific interest in supercritical CO2 systems for power generation using all potential heat sources including solar, geothermal, fossil fuel, biofuel, and nuclear.”
Sandia currently has two supercritical CO2 test loops (the term loop derives from the shape taken by the working fluid as it completes each circuit). A power production loop is located at the Arvada, Colo., site of contractor Barber Nichols Inc., where it has been running and producing approximately 240 kilowatts (electrical) during the developmental phase that began in March 2010. It is now being upgraded and is expected to be shipped to Sandia this summer. A second loop, located in Sandia’s Tech Area 5, is a research device to understand the unusual issues of compression, bearings, seals, and friction that exist near the critical point, where the carbon dioxide has the density of liquid but otherwise has many of the properties of a gas.
Immediate plans call for Sandia to continue to develop and operate the small test loops to identify key features and technologies. Test results will illustrate the capability of the concept, particularly its compactness, efficiency, and scalability to larger systems. Future plans call for commercialization of the technology and development of an industrial demonstration plant at 10 MWe.
A competing system, using Brayton cycles with helium as the working fluid, is designed to operate at about 925 Celsius and is expected to produce electrical power at 43 percent to 46 percent efficiency. By contrast, the supercritical CO2 Brayton cycle provides the same efficiency as helium Brayton systems but at a considerably lower temperature (250-300 Celsius). The S-CO2 equipment is also more compact than that of the helium cycle, which in turn is more compact than the conventional steam cycle.
Under normal conditions materials behave in a predictable, classical, “ideal” way as conditions cause them to change phase, as when water turns to steam. But this model tends not to work at lower temperatures or higher pressures than those that exist at these critical points. In the case of carbon dioxide, it becomes an unusually dense “supercritical” liquid at the point where it is held between the gas phase and liquid phase. The supercritical properties of carbon dioxide at temperatures above 500 Celsius and pressures above 7.6 megapascals enable the system to operate with very high thermal efficiency, exceeding even those of a large coal-fired power plant and nearly twice as efficient as that of a gasoline engine (about 25 percent).
In other words, as compared with other gas turbines the S-CO2 Brayton system could increase the electrical power produced per unit of fuel by 40 percent or more. The combination of low temperatures, high efficiency, and high power density allows for the development of very compact, transportable systems that are more affordable because only standard engineering materials (stainless steel) are required, less material is needed, and the small size allows for advanced-modular manufacturing processes.
“Sandia is not alone in this field, but we are in the lead,” Steve says. “We’re past the point of wondering if these power systems are going to be developed; the question remains of who will be first to market. Sandia and DOE have a wonderful opportunity in the commercialization effort.”
Other individuals who contributed substantially to this project are Robert Fuller (Barber Nichols Inc.), Paul Pickard (Sandia retired), Milton Vernon (6221), Keith Barrett (PrimeCore Inc.), Ross Radel (former Sandian), Thomas Conboy (6221), and Gary Rochau, (manager 6621).
Sandia’s S-CO2 Brayton cycle program is supported by DOE with funding from the Labs’ Laboratory Directed Research & Development (LDRD) program. -- Nigel Hey
By Patti Koning
After 30 years of research into how things burn, it was fitting that at the grand opening of the Combustion Research Computation and Visualization (CRCV) facility, the ribbon wasn’t cut with the traditional pair of oversized scissors. Instead, it was torched by Div. 8000 VP Rick Stulen (8000), Eric Rohlfing of DOE’s Office of Science, and Stephen Goguen of DOE’s Office of Energy Efficiency and Renewable Energy (EERE).
The grand opening of the CRCV marks the start of a new chapter for the Combustion Research Facility (CRF), harnessing the power of supercomputers to further understand and develop combustion processes. Bob Carling (8300), director of the CRF, recalled the origins of the facility in the nuclear weapons program.
“Back during the time of the oil embargo, some folks here thought you could use the lasers from the nuclear weapons program to interrogate combustion systems. The idea was that with research and collaborative work with scientists and engineers from around the world, you could improve combustion processes, from the point of view of both better efficiency and reduced pollutants,” he said.
Bob recalled how, 30 years ago, the CRF began with one big laser piped to a few different labs, a model that worked for a time. Eventually lasers became so ubiquitous that most labs in the CRF have several — an evolution similar to that of computers. Back when the CRF was first opened, scientists and engineers were still using punch cards to run programs. Today, noted Bob, computers are so common that everyone has one on their hip.
“The founding concept of the CRF remains the same, to bring together people from throughout the world to work collectively with our scientists and engineers,” he said. “As we’ve evolved from heavy experimental work, we know and understand that to face the next challenges in combustion we need sophisticated models and predictive capabilities.”
The new collaborative research facility will serve as a focal point to accelerate the realization of predictive modeling and simulation for combustion. The CRCV will provide interactive data visualization and collaborative workspaces, as well as a 2,000-square-foot machine room for the dedicated computational capability. Sandia is in the process of achieving LEED certification for the use of “green” technologies in the building’s construction.
Collaboration is ‘outstanding’
The CRCV is cofunded by the DOE’s Office of Science and EERE. Rohlfing, director of the chemical sciences, geosciences, and biosciences division at the Office of Science, noted that this partnership, while unique, is one that DOE would like to replicate elsewhere. He has a distinct vantage point, as both an alumni of the CRF — he recalled working with one of those facility lasers — and now as a leader at one of the funding organizations.
“The collaboration between Basic Energy Science and EERE’s vehicle technologies program is outstanding and effective. This is probably one of the only examples where these two organizations have come together to fund a modest, yet very effective, building,” he said. “The work that this building will facilitate is a natural part of the evolution of combustion science and technology and we are delighted to help cosponsor it.”
Goguen, a senior engineer in EERE’s office of vehicle technologies, commented that proof of the CRF’s success is visible on roads everywhere. He recalled as a child seeing big belches of black smoke coming off buses and spewing from big trucks, something that doesn’t exist anymore, thanks, in part to the CRF.
“It’s amazing, but at the same time, you’d think there’d be a penalty to be paid, but there wasn’t. In that same time period, the efficiency of engines also has gone up significantly. From what I saw today, walking around and listening to new ideas being explored in the labs, it’s a new beginning,” he said.
In the audience at the grand opening were current and past CRF researchers, including former Div. 8000 VP Tom Cook, who oversaw the startup of the CRF. Also on hand were regional elected officials and their representatives and educators from Las Positas College, the University of California, Davis, and the University of Michigan. Rick received certificates of commendation from US Representatives John Garamendi and Jerry McNerney, State Assemblymember Joan Buchanan, State Senator Loni Hancock, the Alameda County Board of Supervisors, and the City of Livermore.
“This facility represents a very important step toward the accomplishment of the innovation hub, i-GATE, which the City of Livermore, other Tri Valley cities, Sandia, and Lawrence Livermore National Lab have been working on for over a year,” said Jeff Williams, a Livermore city council member. “Speaking on behalf of the surrounding cities and region, Livermore enthusiastically supports the new opportunities that this capability brings to the area and we congratulate Sandia and DOE for taking the bold step of creating and building this facility.”
To conclude the program, two invited speakers spoke of the history and future of large-scale computing. Jeffrey Nichols, associate lab director at Oak Ridge National Laboratory, gave a talk on complexity and how work done at the CRCV will aid researchers in making sense of massive volumes of data. Daniel Haworth, a professor of mechanical engineering at Pennsylvania State University, led the audience on journey through the history of computational combustion.In 30 years, the CRF has come a long way — from a single laser and punch cards to lasers as regular lab equipment and a 50-teraflop computer, which puts it in the top 100 fastest computers worldwide. What combustion research will look like in 2040 is still the stuff of science fiction, but perhaps 50 teraflops of visualization capability can give us a hint of what the future might hold. -- Patti Koning
By Mike Janes
Graduate students pursuing careers in energy, policy, science, and environmental matters are encouraged to submit applications for Technology and Policy Tools for Energy in an Uncertain World, a week-long summer institute at Sandia/California. The program will take place Aug. 7–12 and is open to US citizens and foreign nationals.
Twenty students will be selected to participate. Applications are due by March 15 (see http://www.sandia.gov/summer_institute for details and online application).
Participating students will collaborate in small teams, working side-by-side with leading Sandia scientists and researchers at the Labs’ world-renowned Combustion Research Facility (CRF) and other cutting-edge Sandia facilities.
“A summer institute for graduate students is one of many ideas we are pursuing to increase awareness and collaboration with our staff,” says Bob Carling, director of Transportation Energy Center 8300. Bob says Sandia/California has an ongoing interest in exposing a variety of outside scientists and engineers — including students — to the lab and its new open access.
Bob says he hopes the experience will help persuade participating students to consider Sandia as a future place of full-time employment.
“We also hope they will spread the word back at their home institutions regarding the importance of the work we do at Sandia and the high quality of our staff and facilities,” he says.
Students will select from the following technical focus areas:
Institute participants will be provided housing at a Livermore suites hotel located near Sandia. Transportation and meals will also be provided. - Mike Janes