(Press-News.org) ALBUQUERQUE, N.M. — Sandia National Laboratories researchers are 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 equipped with steam turbines, or a 40 percent improvement for simple gas turbines. The system 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. 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 of electricity from a package with a volume as small as four cubic meters.
The Brayton cycle, named after George Brayton, originally functioned by heating air in a confined space and then releasing it in a particular direction. The same principle is used to power jet engines today.
"This machine is basically a jet engine running on a hot liquid," said principal investigator Steve Wright of Sandia's Advanced Nuclear Concepts group. "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 of electricity 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 at Sandia in Albuquerque, is used to research 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 MW of electricity.
A competing system, also at Sandia and using Brayton cycles with helium as the working fluid, is designed to operate at about 925 degrees C 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 C). 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 C and pressures above 7.6 megapascals enable the system to operate with very high thermal efficiency, exceeding even those of a large coal-generated 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," Wright said. "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."
INFORMATION:
Sandia's S-CO2 Brayton cycle program is supported by DOE with funding from the Labs' Laboratory Directed Research & Development (LDRD) program.
Sandia National Laboratories is a multiprogram laboratory operated and managed by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.
Sandia news media contact: Neal Singer, nsinger@sandia.gov (505) 845-7078
END
A new carbon model allows scientists to estimate sources and losses of organic carbon in surface waters in the United States. Study results indicate that streams act as both sources and sinks for organic carbon.
"Model estimates help managers and researchers track carbon transport in streams, which is information that is ultimately needed to improve our understanding of the fate of rising carbon dioxide levels in the atmosphere," said Dr. Richard Smith, a USGS hydrologist and coauthor of the study. "The study contributes new information on the role of rivers as sources ...
May vaccinations put too much strain on or weaken children's immune systems and are therefore harmful? Roma Schmitz and her colleagues from the Robert Koch Institute investigate exactly this research question in the current issue of Deutsches Ärzteblatt International (Dtsch Arztebl Int 2011; 108(7): 105-11). Their data are based on the results of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS).
In their study, the authors compare the occurrence of infections and allergies in vaccinated and unvaccinated children and adolescents. These ...
Analysis of the early data from Understanding Society based on 14,000 UK households found that overall the best sleep was reported by people with higher levels of education and by married people. The type of work a person does also impacts on sleep, with those in routine occupations reporting worse sleep than those in professional occupations.
Professor Sara Arber at the University of Surrey who analysed the findings said: "Given the links between sleep, social and economic circumstances and poor health found in this and other surveys, health promotion campaigns should ...
ESA's Mars Express has returned new images of an elongated impact crater in the southern hemisphere of Mars. Located just south of the Huygens basin, it could have been carved out by a train of projectiles striking the planet at a shallow angle.
The large Huygens basin (not visible in the main image but seen in the wider contextual image) is about 450 km in diameter and lies in the heavily cratered southern highlands. In this area there are many impact scars but none perhaps are more intriguing than the 'elongated craters'.
One of these craters is seen in this new image, ...
Some of the most dreaded diseases in the world such as plague, typhoid and cholera are caused by bacteria that have one thing in common: they possess an infection apparatus which is a nearly unbeatable weapon. When attacking a cell of the body, they develop numerous hollow-needle-shaped structures that project from the bacterial surface. Through these needles, the bacteria inject signal substances into the host cells, which re-program the latter and thereby overcome their defense. From this time on it's easy game for the pathogens; they can invade the cells unimpeded and ...
Biologically targeted BNCT treatment is based on producing radiation inside a tumour using
boron-10 and thermal neutrons. Boron-10 is introduced into cancer cells with the help of a special carrier substance (phenylalanine), after which the tumour is irradiated with lowenergy neutrons. The latter react with the boron to generate high-LET radiation, which may destroy the cancer cells. One to two BNCT treatment sessions may be sufficient to destroy a tumour, while keeping the impact of radiation on surrounding healthy tissue to a minimum.
A research reactor is currently ...
EAST LANSING, Mich. — Black people who identify more strongly with their racial identity are generally happier, according to a study led by psychology researchers at Michigan State University.
The study, funded by the National Institute of Mental Health, appears in the current issue of Cultural Diversity and Ethnic Minority Psychology, a research journal published by the American Psychological Association.
"This is the first empirical study we know of that shows a relationship between racial identity and happiness," said Stevie C.Y. Yap, doctoral candidate in psychology ...
AUGUSTA, Ga. - Overweight adolescents already struggling with risk factors such as insulin resistance may need to add weak bones to their list of health concerns, researchers report.
A study of 143 overweight 14-18 year olds showed those with risk factors such as the precursor for diabetes and low levels of the blood-vessel protecting HDL cholesterol have less bone mass – an indicator of bone strength – than their overweight but otherwise healthy peers, according to researchers at Georgia Health Sciences University's Georgia Prevention Institute.
Other risk factors ...
Seismologists have developed a new system that could be used to warn future populations of an impending tsunami only minutes after the initial earthquake. The system, known as RTerg, could help reduce the death toll by giving local residents valuable time to move to safer ground. The study by researchers at the Georgia Institute of Technology appears in the March 5 edition of Geophysical Research Letters.
"We developed a system that, in real time, successfully identified the magnitude 7.8 2010 Sumatran earthquake as a rare and destructive tsunami earthquake. Using this ...
A Cardiff University study has established a link between pub violence and happy hour-style drinking promotions.
The findings also show that pub staff themselves need to do more to stop heavily intoxicated customers from continuing to drink.
The team studied pubs and nightclubs with a history of violence across five different cities and towns in the UK. Customers entering and leaving the premises were breathalysed. The team also recorded data about the price of beer and any drink promotions at each establishment. Their findings were then linked to police and hospital ...
