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Advanced turbomachinery solutions for improved and emerging green energy technologies
The world’s growing demand for renewable, sustainable, and environmentally friendly electricity is being provided by a broad and fragmented mix of green energy technologies. And virtually all refined, new, and proposed technologies for generating “green” electricity rely on improved designs for turbines, compressors, expanders, pumps, and fans to make them economically and environmentally viable. Solar, wind, hydro, tidal, wave, geothermal, and biomass energy resources require advanced turbomachinery designs to efficiently extract power from low-density flows, and to help justify the value proposition required for project success.
A Total “green” Turbomachinery Resource
The success of a highly effective and sustainable turbo-green machine operating over a wide range of conditions can often depend on advances and breakthroughs in turbomachinery design and manufacturing facilitated by highly specialized CAE and CAM software systems. To meet optimum performance goals, many turbo-green impeller designs will utilize thin, highly sculpted, and closely spaced blade shapes. But to be cost competitive with fossil-fueled power generation, these elegant solutions must be complemented with sophisticated tool-path programs for accurate and economical 5-axis milling.
Advancing and optimizing designs to provide energy saving and manufacturable solutions is considered a core capability at Concepts NREC, and those skills and proprietary tools are well demonstrated by the variety of advanced technology turbomachinery CN has developed for green energy technologies.
Recent advances in turbine design and rotor materials are helping realize the objectives of generating reliable and economical electricity from repetitive wave action.
Fish-safe hydroelectric turbine design reduces fish kill while efficiently generating power.
Software and services to meet turbo-green system challenges include:
Engineering development services for turbomachinery products and components
Manufacturing services for prototypes and production
CAE and CAM software for performance, efficiency, compact size, and viable cost
Education programs and publications addressing turbomachinery design
Advancements in turbomachinery design and manufacturing for turbo-green technologies
The engineering practices perfected in traditional turbomachinery development are now being applied to the newest generation of turbo green equipment being incorporated into virtually all the latest technologies for renewable and sustainable power. Some of these turbomachines are relatively mature but continue to be optimized for even better performance, efficiency, and energy conservation, as well as for new applications and special requirements. And the turbomachinery implications for each technology reveal many opportunities for performance improvements as well as potential engineering breakthroughs.
Wind Turbines and Compressors
Newer blade designs operating more efficiently on low flows
Utility-scale commercial wind farms are now considered a mature technology and have become economically competitive (even with coal-fueled generation) in select coastal locations. Micro wind-capture designs for onsite power generation are now being developed to operate on gentle and less consistent winds.
Several radically different and highly efficient axial and radial impeller designs are now emerging that will effectively accommodate urban and onsite installations. To be viable, these small wind turbines will require much less wind for start-up (as low as 5 mph) and for optimum levels of efficiency.
Wind-turbine turbomachinery is also being further refined to reduce the environmental impacts of noise and bird kills. New bird-safe blade shapes are especially needed for offshore regions within migratory flight paths. In another wind-power cycle, a wind turbine is used to drive a compressor. The stored compressed air is available to drive a turbine generator (or some other application) at times when needed.
Multifuel turbines driven by concentrated solar-thermal energy
Both electrical and thermal-solar-powered energy systems will primarily focus on distributed generation for industrial/commercial-scale sites. Utility-scale solar plants will require even more sophisticated and efficient turbomachinery to overcome several limiting factors that include only partial predictability for periods of solar generation and the amount of power that will be produced.
However, newer and better solar technologies using concentrated solar heat (at 400°F and considerably higher) to drive a steam or gas turbine are promising to more effectively, efficiently, and practically utilize solar energy for electrical generation or to power some other thermal application such as an absorption chiller. The overlying turbomachinery challenge in all solar technologies and applications is to further advance turbine and pump efficiency in an effort to reduce their $/Watt installed cost.
Capturing energy in ocean estuary flows and in rivers without dams
There is still potential for improving the “water to wire” efficiency of most existing hydropower turbines, and with no further negative consequence to the environment. And there is also enormous potential for new hydroelectric designs that can provide continuous and predictable power from various low-head, low-power water flows – without the need for dams – that may also vary dramatically by location or season. With an energy density 850 times greater than wind, even slow flowing waters can be an effective energy resource for a highly efficient hydrokinetic turbine.
These same turbo-green technologies are also planned to operate effectively in the low flows of underground streams and falling water. The underwater streams of ocean estuaries are an especially reliable energy resource for driving a hydrokinetic turbine.
Tidal-Current and Wave-Compressor Turbines
Dependably extracting energy without affecting flow or the environment
Within the mix of natural (and national) energy resources, the enormous potential in repetitive ocean waves and tidal currents is now being addressed by several turbo-green technologies that propose to most efficiently extract energy without affecting the flow or the environment. Because all water-flow and wave-powered systems operate in a relatively harsh environment, turbomachinery must be designed to operate at peak effectiveness over a wide range of conditions, as well as be optimized for reliability and durability.
One promising technology is a tidal-current turbine designed to harness energy from various marine currents. The unique Golay vertical-axis tidal-current turbine uses hydrofoil blades placed helically around an axis to operate bi-directionally as tides go in and out. An underwater tidal turbine farm would operate much like an offshore wind farm except for the added complexities involved in a relatively harsher underwater environment.
Another turbo-green solution uses an oscillating water column (OWC) to capture and convert ocean-wave energy into compressed air to drive an air-turbine generator. The core technology incorporates a patented high-efficiency, variable-pitch turbine in which an electro-mechanical blade-pitch control enables rotation in the same direction irrespective of the bidirectional airflow of the OWC system.
Geothermal Pumps and Turbines
More effectively utilizing thermal-energy resources below the earth’s crust
Newer geothermal electric-power plants using binary-cycle systems are capable of operating efficiently at relatively low temperatures of about 225°F to 360°F (compared to dry-steam or flash-steam plants). However, to further reduce the high capital cost per kilowatt of power generated, there is a great incentive to modify the turbomachinery used in this Organic Rankine Cycle (ORC) in an attempt to achieve maximum potential effectiveness.
To obtain meaningful improvements, these turbomachinery systems require more efficient pumps and turbines. One such gravity head energy system (GHES) uses a compact and highly efficient turbo-expander pump installed deep within the wellbore. This highly advanced turbo-green design significantly increases the overall cycle efficiency by at least 20% and up to 30%.
Biomass Steam Turbines
Operating on combustible wood waste and fuel crops
Steam turbines have long been a natural green energy choice for onsite CHP plants with access to a nearby supply of low-cost biomass fuel. On a utility scale, many operators are now converting coal plants to operate on much cleaner biomass wood chips.
A wood chip-fired boiler can generate pressurized steam at 950°F to drive a steam turbine, and biomass power plants can operate 24/7 or on call as needed. And although steam-turbine technology in a biomass cycle is considered quite mature, advanced capabilities in turbomachinery design will now allow even higher efficiencies, cleaner emissions, and reduced expenses.
Fueled by combustible waste gas from landfills and wastewater digesters
Today’s second and third generation microturbines are now employing advanced and refined turbomachinery designs that permit operation at higher temperatures to achieve ever better efficiencies and cleaner emissions. And new turbine designs are in development for multifuel hybrid cycles that might, as in one case, operate alternatively on biogas fuel when solar-thermal energy is not available.
Even with grid availability, some small gas turbines operating on methane collected from landfills or wastewater digesters can provide continuous electricity at efficiencies and rates comparable to a utility. And many sites currently operating reciprocating-engine generators supplied by a biogas fuel are retrofitting gas turbines for onsite power because the latest gas-turbine technology provides significantly lower emissions, better reliability, longer service intervals, and reduced maintenance.
Other Turbo-Green Machinery
For nuclear plants, fuel cells, and energy storage
Nuclear power plants. Considering that nuclear fuel releases a million times (projected up to 50 million times) more energy per unit than fossil fuels, with zero harmful emissions, this alternative energy technology is gaining renewed interest for refinement – but not for application in the U.S. If nuclear generating capabilities are to be expanded in the U.S., what you can expect for future plants (and their turbomachinery systems) is one standardized design to dramatically confine costs. Variations to accommodate some variables will be developed and supplied by capable vendors.
Fuel cells. Although extraordinary electrical efficiencies have resulted from fuel-cell and turbine-compressor combined-cycle, closed-loop systems, turbomachinery development is currently focused on future hydrogen supply-line compressors for fuel cells. Reciprocating compressors currently in use rely on lubricants that can seep into cylinders and contaminate the hydrogen. A centrifugal compressor avoids such contamination and allows higher compression efficiency for an equivalent duty.
A large-scale centrifugal compressor now being designed for hydrogen pipeline transmission is expected to service a future demand to be created by the adoption of practical fuel-cell power plants and cars. The 8,000 hp, six-stage compressor will move 240,000 kg of hydrogen a day at pressures up to 1,200 psi, and be considerably smaller (1/4 the size) and more efficient than compressors currently in use on hydrogen pipelines.
Energy storage. The rapidly advancing development and acceptance of green energy technologies for both distributed generation and to supply the smart grid, demand that renewable energy be paired with energy storage. With the exception of battery systems, all other storage methods depend on the efficiency of various turbomachines for pumping fluids and compressing gases.
Of recent interest is a new generation of flywheels using multiton carbon-fiber rotors spinning on magnetic bearings in a vacuum. Each flywheel is expected to store up to several megawatts of backup power for buffering power fluctuations from intermittent energy sources (wind and solar) or to stabilize power for changing loads. In one system, a motor powered by green energy accelerates a flywheel to terminal speed, then the rotor maintains its inertial energy “indefinitely” until released by reversing the process and using the motor as a generator.