In the family of heat engines, the gas turbine is unique in that it is used to produce two different kinds of useful power. By converting combusted fuel heat into work, a gas turbine engine can produce external shaft power (e.g., to drive a connected electric generator) or jet power (e.g., as a jet engine, to produce thrust forces to propel an aircraft). This means that the gas turbine’s thermodynamic figure of merit, thermal efficiency, is multifaceted, and calls for a nuanced examination.

James Hobson, a mechanical engineer better known as The Hacksmith, has fashioned a YouTube career from building real-world versions of video game and comic book gadgets—Make It Real videos. Like every inventor, Hobson has a garage packed with tools. These range from laser cutters to 3D printers. Sometimes, they provide cosmetic packaging for his concoctions. Other times, like his metal printed 20-kilowatt heat saber, they are highly functional. This article charts his career journey.

Concentrated solar plants have been designed to store thermal energy so as to produce power after sundown, but heat storage should also be of interest to operators of nuclear power plants. Adding heat storage to light-water reactors is the enabling technology for a carbon-free electricity industry based on solar, wind, and nuclear power. And it can accomplish this with little disruption to the operations of existing nuclear plants. This article delves into the current heat storage technologies that are at various states of readiness to be deployed.

Almost every form of energy conversion creates heat, making it one of the most prevalent forms of energy. When used for mechanical work, thermal energy is most efficient when it can be moved, stored, and converted at its highest possible temperature. But most of today’s pumps and compressors are made from superalloys and ceramics and can’t handle that extreme heat. A team from Georgia Tech has developed a ceramic pump they and others expect to spur a new generation of highly efficient, low-cost systems for storing, transporting, and converting surplus thermal energy produced by renewables like solar and wind.

The promises of increased efficiency, simplicity, and high power density are driving the current research focus on rotating detonation engines (RDEs). An engine that uses detonation rather than deflagration could have some key advantages. If harnessed in a gas turbine or rocket, detonation could reduce the need for some expensive hardware, lighten engine weight and increase power output and efficiency. Today, variants of the RDE as a combustor for gas turbines, rockets, and scramjets are being explored at the Air Force Research Laboratory (AFRL), Naval Research Laboratory, Naval Postgraduate School, and the Department of Energy. Similar work is being conducted in several other countries. This study provides a deeper look into RDEs.

This article discusses the technology used at the John W. Turk Jr. Power Plant in Fulton, Ark., to tackle the challenges of raising the pressure and temperature of the steam to new heights. The Turk plant is the first in the United States where the final steam conditions exceed both the critical pressure and a temperature of 1,100°F. Operating as an ultrasupercritical boiler, the Turk plant has the highest net plant efficiency of any solid fuel power plant in the United States. In this plant, Southwestern Electric Power Company tapped Babcock & Wilcox to design, supply, and erect the 600-MW advanced supercritical steam generator. To best optimize efficiency, the design team selected a single reheat cycle with elevated steam pressure and temperature. Babcock & Wilcox engineers also employed computational fluid dynamics modeling to place burners and overfire air ports to make the best use of low-sulfur coal.

The article presents an overview of the compressed air energy storage gas turbines (CAES GT). The CAES GT works at low turbine inlet temperatures and is capable of fast start and loading 10 minutes to full load. It is characterized by high ramp rates up or down with minimum load as low as 10%, and flat heat rate for most of the load range. With exceptional low fuel input efficiency of 85%, the kW/hr equivalent Btu input to the compression cycle must be added, resulting in an overall efficiency of close to 55%, impressive versus a 300 MW GTCC plant that is required to load follow when integrating renewable energy source. The metamorphosis from that of a “peak shaving” unit to that of a grid support and renewable energy enabler is now complete. Advanced Reheat Gas Turbines such as the GT24/26 with higher operating temperatures offer further potential development for CAES.

This article elaborates the features of Multi-Fluid/CO2 Plume Geothermal (CPG) energy storage system. This system provides utility-scale diurnal and seasonal energy storage and dispatchable power, while permanently sequestering carbon dioxide (CO2) from industrial-scale fossil-energy power plants. Operationally, a Multi-Fluid/CPG system is radically different from traditional power plants or energy storage systems, such as pumped hydroelectric. Most of the system resides below the ground surface, consisting of horizontal injection and production wells arrayed in concentric rings that could be five miles or more across. This ring configuration is used to pressurize and confine CO2 in the region in the center of the array and to pressurize brine between the outer two rings. Because the Multi-Fluid/CPG system relies on the injection of carbon dioxide, the cost of sequestration is turned into an operational investment. Just as enhanced oil recovery has made geological CO2 sequestration economically viable in the petroleum industry. Multi-Fluid/CPG can make it profitable to lock away CO2 that would otherwise be emitted.

The article presents an overview of how connected or smart systems can help improve day-to-day lives and be beneficial for businesses as well. Connectivity opens a world of possibilities for improving occupant experience, reducing energy costs, and managing building equipment—three areas that can increase returns on real estate assets. Smart systems are expected to improve the efficiency of heat, light, sanitation, security, safety, and a host of services. The savings of energy alone could be significant. Connections between things and people, supported by networked processes, will enable everyone to turn vast amounts of heterogeneous data into practical information that can be used to do things that weren’t possible before, or to do familiar tasks better. Cognitive work and service assistants with deep learning and reasoning capabilities will support various human activities. The unprecedented communication can inspire creative thinking and collaborations among businesses and organizations.

This article presents overview of various aspects and use of a solar-powered airplane. The plane, Solar Impulse 2, started on its world tour in March from Abu Dhabi. The founders of the project, Bertrand Piccard and Andre Borschberg, are taking turns as pilots. Solvay, a French company that makes high-performance polymers, became an early partner. The airplane’s 72-meter-long wing spars had extraordinary structural and weight requirements. The Solar Impulse team came up with a laminate, consisting of a honeycomb structure, made of a high-performance Torlon polymer provided by Solvay, sandwiched between super-thin layers of carbon fiber composite. Lightweight, highly efficient foam insulation is being tested by Bayer in affordable housing in the Philippines and Malaysia. Solar Impulse could not afford cabin pressurization or heating because of weight requirements. Instead, designers insulated the cabin so that retaining the pilot’s body heat and that of the instruments would keep conditions bearable. Engineers at Bayer went to work on some ultra-lightweight and highly effective polyurethane foam insulation. Solar Impulse has helped push technological limits.

This article discusses various aspects of snowflake architectures. It is certain that every snowflake conforms to only one architecture: a flat star with six fishbones connected at the center. The latent heat of solidification, which is released by the water vapor that becomes solid at the bead surface. There comes a critical time when the spherical bead is no longer an efficient architecture for dissipating heat. The principle calls for design change, toward faster heat release and solidification. The growth of ice morphs abruptly into a ball continued in one plane by needles. Because of the configuration of the water molecule, the needles grow in six directions. The flat star transfers heat to the surroundings more easily than a spherical bead with the same diameter. In order to give credit to the view that every snowflake is unique, the actual configuration depends on many secondary effects, which are of random origin.

This article explores uses of solar energy as a substitute to fossil fuels. Solar energy is usually considered in terms of making electricity; however, it also has the potential to supplant fossil fuels in the production of liquid fuels, and in driving endothermic industrial processes. Solar thermochemical processes are feasible, and a solar power concentration process that harnesses sunlight’s infrared energy is the best suited technology for making solar fuels a reality. Another area in which solar commodity production may have advantages over traditional industrial practice is in the separation of pure metal and oxygen from metal oxides found naturally in many ore deposits. Solar fuels can provide a stable and strategically important energy resource; some may consider them to be the ideal solution for sustainable energy independence. Solar thermochemistry could potentially have the biggest impact in the production of hydrogen-derived fuels which would be capable of replacing those derived from fossil fuels.

This article discusses the potential use of solar energy in various industrial processes. Solar energy is usually considered in terms of making electricity, but it also has the potential to replace fossil fuels in the production of liquid fuels, and in driving endothermic industrial processes. Solar thermochemical processes are feasible, and a solar power concentration process that harnesses sunlight's infrared energy is the best-suited technology for making solar fuels a reality. However, in spite of their appeal, solar thermochemical processes also have the same drawback that direct solar power has: the transient and diurnal nature of sunshine. Fluctuations of available solar radiation – over the course of a day, across different types of weather, and from season to season – present considerable challenges for potential solar-thermal systems. While there are economically affordable and commercially available solutions to some of those problems, substantial research and development is still required.

This article focuses on various technical and functional aspects of detonation gas turbines. Detonation combustion involves a supersonic flow, with the chemical reaction front accelerating, driving a shock wave system in its advancement. In the 1990s, detonation-based power concepts began with pulse detonation engines (PDEs), and have now moved into the continuous detonation mode, termed rotating detonation engines (RDEs). Modern gas turbine combustors are compact, robust, tolerant of a wide variety of fuels, and provide the highest combustion intensities. The single-spool RDE gas turbine is represented by a detonation cycle, which accounts for the supersonic features of the heat addition, starting at station 2.5′. Continued research and development by the RDE technical community is needed to see if the promise of improved performance and downsized turbomachinery for a detonation cycle is real.

This study explores various uses of engineering as a tool for solving problems and improving the quality of life. The experiments in the article show that competitive athletes swim with their fingers spread slightly, because this configuration generates greater speed, the research being based on a principle known as constructional law. The constructional law has been applied to predict all the key features of the design of animal locomotion, which includes human running and swimming. In engineering, the discovery expands a domain of constructal-design results that has been growing fast. Bodies that generate heat volumetrically are endowed with maximum heat transfer density when the spacing between the solid surfaces internal to the volume have certain sizes that are smaller in forced convection than in natural convection. The volumetric cooling of future electronics, avionics, and self-cooling materials rests on this class of constructal designs. The swimming with spread fingers is the corresponding design of a body for maximum momentum transfer density.

This article highlights different research efforts to utilize thermal energy and thermal energy storage technologies. At several technical and panel sessions at the November ASME International Mechanical Engineering Congress and Exposition in Houston, there has been much discussion of cutting-edge work in thermal energy storage, including thermal energy storage materials, applications, and systems. Research into thermal energy storage is not limited to the confines of government and academia. Private companies are investigating whether they can incorporate thermal storage into some of their systems. Another potential advantage for solar thermal power is efficiency. Storing thermal energy as sensible heat is the most straightforward of the three methods, and the one that is the most widely deployed. A wide range of materials from simple concrete to synthetic oils has been tried for storing thermal energy. An energy storage system based on latent heat released as a material changes phase can be cost-effective. Thermal energy storage can become a game-changing technology wherever energy demand does not align exactly with energy supply. However, significant development challenges remain before these potential benefits can be realized.

This article introduces the concept of blending fluid power with mechanical structure through addictive manufacturing. Today, fluid-powered devices are manufactured using conventional fabrication practices. The additive process enables integrated structure, actuation, fluid passages, thermal management, and control within a single fabrication process. Fluid can be routed efficiently through the structure without the need for cross-drilled holes or plugs. Fluid passages can be optimized for heat dissipation and minimized head loss. One of the primary issues regarding parts manufactured using the additive manufacturing process is their mechanical properties. Results show that components made with Ti-6-4 powders have a minimum yield stress and ultimate strength that exceeds Grade 5 specifications. The Arcan system uses a powder bed that has an elevated temperature. Therefore, the part exhibits very little residual stress during the manufacturing process. This leads to improved mechanical strength but induces challenges in powder removal. The specific advantages are reduced weight, potential for lower cost, and reduced part counts.

This article describes the functioning of the gas turbine cogeneration power plant at the University of Connecticut (UConn) in Storrs. This 25-MW power plant serves the 18,000 students’ campus. It has been in operation since 2006 and is expected to save the University $180M in energy costs over its 40-year design life. The heart of the UConn cogeneration plant consists of three 7-MW Solar Taurus gas turbines burning natural gas, with fuel oil as a backup. These drive water-cooled generators to produce up to 20–24 MW of electrical power distributed throughout the campus. Gas turbine exhaust heat is used to generate up to 200,000 pounds per hour of steam in heat recovery steam generators (HRSGs). The HRSGs provide high-pressure steam to power a 4.6-MW steam turbine generator set for more electrical power and low-pressure steam for campus heating. The waste heat from the steam turbine contained in low-pressure turbine exhaust steam is combined with the HRSG low-pressure steam output for campus heating.

This article presents an overview of a turbine that uses supercritical carbon dioxide (CO 2 ) to deliver great power. At around 73 atmospheres and roughly room temperature, CO 2 makes a strange transition from a gas to a state known as a supercritical fluid. A supercritical fluid is dense, like a liquid, but it expands to fill a volume the way a gas does. These properties make supercritical CO2 an incredibly tantalizing working fluid for Brayton cycle gas turbines. Such gas turbine systems promise an increased thermal-to-electric conversion efficiency of 50% over conventional gas turbines. The system is also very small and simple, meaning that capital costs should be relatively low. The plant uses standard materials like chrome-based steel alloys, stainless steels, or nickel-based alloys at high temperatures (up to 800°C). It can also be used with all heat sources, opening up a wide array of previously unavailable markets for power production. For these reasons, the technology is quite promising.

This article elaborates a new design approach that aims at designing products with built-in disassembly means to be activated at the end of a product’s life. Two projects explored in this area are the design of a new class of joints that can be detached by the application of localized heat, and the design of assemblies that can disintegrate via a domino-like process triggered by the removal of one or only a few fasteners. The detachable joints (heat-reversible locator-snap systems) allow easy, non-destructive, and clean detaching of product enclosures. They consist of locators and snaps molded on the internal surfaces of thin-walled product enclosures. During disassembly, thermal expansion of the enclosure walls constrained by locators and the temperature gradient along the wall thickness are exploited to realize the deformation required to release the snaps. In self-disintegrating assemblies, the relative motions of components are constrained by the locators integral to the components, in such a way that the removal of one or few fasteners would cause the self-disintegration of the assembly in a desired sequence.