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ARID

Advanced Research In Dry cooling

ARPA-E's Advanced Research In Dry cooling (ARID) program comprises projects that are aimed at maintaining the efficiency of U.S. electric power generation, which otherwise could suffer due to regional water shortages. To achieve this objective, ARID project teams will create novel air-cooled heat exchangers, supplemental cooling systems, and/or cool-storage systems that can cost-effectively and efficiently dissipate, or reject, waste heat with no net water consumption. Project teams will design kilowatt-scale testing prototypes to ensure the technologies can scale up to the megawatt-cooling capacities of real systems without significant performance loss. If successful, these dry-cooling technologies will significantly reduce water use at power plants without sacrificing efficiency and with minimal additional costs.
  For a detailed technical overview about this program, please click here.    

Advanced Cooling Technologies, Inc.

Heat-Pipe PCM Based Cool Storage for Air-Cooled Systems

Advanced Cooling Technologies, Inc. (ACT) will work with Lehigh University, the University of Missouri, and Evapco, Inc. to design and build a novel cool storage system that will increase the efficiency of a plant's dry-cooling system. During the day, the system will transfer waste heat from the plant's heated condenser water via an array of heat pipes to a cool storage unit containing a phase-change material (PCM). The planned PCMs are salt hydrates that can be tailored to store and release large amounts of thermal energy, offering a way to store waste heat until it can be efficiently rejected. When temperatures are lower, such as at night, a novel system of self-agitated fins will be used to promote mixing and enhance heat transfer to air. The effectiveness of the fins will allow a reduction in the size of the storage media and the power required to operate it, both of which could lower costs for the system. Because the PCM materials are salts, their storage temperature can be tuned by changing the water content. Therefore, the storage system can potentially be customized to provide supplemental dry cooling for different climates, including regions with high ambient temperatures, such as the southwestern United States.

Applied Research Associates, Inc. (ARA)

Active Cooling Thermally Induced Vapor-Polymerization Effect (ACTIVE)

Applied Research Associates, Inc. (ARA) will design and fabricate a dry-cooling system that overcomes the inherent thermodynamic performance penalty of air-cooled systems, particularly under high ambient temperatures. ARA's ACTIVE cooling technology uses a polymerization thermochemical cycle to provide supplemental cooling and cool storage that can work as a standalone system or be synchronized with air-cooled units to cool power plant condenser water. The cool storage will be completed in two stages. During the day, the cool storage is maintained near the ambient temperature, and then at night the remainder of cooling can be done using the low temperature nighttime air. The cool storage unit is then ready for plant condenser reuse the next day. This technology will provide power plant condensers with return water at the necessary temperature levels to maintain power production at their optimum thermal efficiency.

Colorado State University

Ultra-Efficient Turbo-Compression Cooling

Colorado State University (CSU) and its partners, Modine and Barber-Nichols, will develop a thermally powered supplemental cooling system for thermoelectric power plants that will enable dry cooling. The technology features a transformational turbo-compressor and low-cost, high-performance heat exchangers that are currently mass produced for the HVAC industry. To operate, low-grade waste heat from the power plant combustion exhaust gases, or flue gas, is captured and used to power a highly efficient turbo-compressor system. The compressor pressurizes vapor in a refrigeration cycle to remove up to 30% of the power plant cooling load. The cooling system utilizes proprietary technology to maximize the turbo compressor and total system efficiencies, enabling a low production cost and an overall smaller, less expensive dry-cooling system. As a result, the cooling system could allow thermoelectric power plants to maintain a high efficiency while eliminating the use of local water resources. Furthermore, due to its very high performance, the turbo-compression cooling system has potential applications in a range of other markets, including commercial HVAC systems, data center cooling, and distributed cooling industries.

Electric Power Research Institute, Inc. (EPRI)

Indirect Dry Cooling Using Recirculating Encapsulated Phase-Change Materials

The Electric Power Research Institute (EPRI) and its partners will design, fabricate, and demonstrate an indirect dry-cooling system that features a rotating mesh heat exchanger with encapsulated phase-change materials (PCMs) such as paraffin, which can absorb and reject heat efficiently. The novel system can be used downstream from a water-cooled steam surface condenser to cool water to a temperature near ambient air temperature, eliminating the need for a cooling tower. The team's design capitalizes on the high latent heat of the solid-to-liquid transition in the PCMs to provide an extremely effective way to lower the temperature of hot water exiting the condenser. The encapsulated PCMs are embedded in polymer tubes that form a porous, mesh-like structure. These modules are then mounted on a rotating system that continuously circulates the encapsulated PCMs from the hot water - where they absorb heat - into a dry section where ambient air passes by the encapsulated PCMs, causing the PCMs to solidify and reject heat to the atmosphere. The multidisciplinary team includes leading industry and academic partners that will provide technical and market assistance, and help build and test a 50 kWth prototype to demonstrate the technology's commercial viability.

General Electric

Low-Cost Heat Pump with Advanced Refrigerant/Absorbent Separation

GE will design, manufacture, and test an absorption heat pump that can be used for supplemental dry cooling at thermoelectric power plants. The team's project features a novel, absorbent-enabled regenerator that doubles the coefficient of performance of conventional absorption heat pumps. The new absorbents demonstrate greater hygroscopic potential, or the ability to prevent evaporation. To remove heat and cool condenser water, these absorbents take in water vapor (refrigerant) and release the water as liquid during desorption without vaporization or boiling. GE's technology will use waste heat from the power plant's flue gas to drive the cooling system, eliminating the need for an additional power source. GE estimates the system will cost half that of conventional absorption heat pumps.

Palo Alto Research Center

Metamaterials-Enhanced Passive Radiative Cooling Panels

PARC, working with SPX Cooling Technologies, is developing a low-cost, passive radiative cooling panel for supplemental dry cooling at power plants. PARC's envisioned end product is a cooling module, consisting of multiple radiative cooling panels tiled over large, enclosed water channels that carry water from an initial cooling system, such as a dry-cooling tower. The cooling panel consists of a two-layer structure in which a reflective film sits atop a unique metamaterial-based emitter. In this architecture, the top layer completely reflects sunlight while the bottom layer effectively emits infrared radiation through a spectral window in the earth's atmosphere. This combination enables radiative cooling of the water even in full illumination by the sun. The cooling panel will be made using a lithography-free process compatible with roll-to-roll fabrication. In a large-scale system, the water temperature at the outlet of the cooling module is expected to be 8oC cooler than the temperature of the water at the inlet, which will result in a 3% efficiency gain for the power plant.

SRI International

STATIC Radiative Cooling for Cold Storage

SRI International (SRI) and PPG Industries, Inc. are integrating SRI's proprietary Spectrally Tuned All-Polymer Technology for Inducing Cooling (STATIC) technology into a novel structure for use as a radiative cooling system that can provide supplemental cooling for power plant water during the daytime or nighttime. The two-layer polymer structure covers a pool holding power plant condenser discharge water. The cover prevents sunlight from penetrating it and warming the water, while allowing thermal energy to radiate to the sky, even during the day. The STATIC structure provides an insulating air gap to prevent conductive and convective heating, and both layers work in concert to reject solar energy. Specifically, the bottom layer acts as an emitter at the water temperature and radiates heat to the sky, while the top layer and key component, produced using STATIC technology, enables transmittance of the thermal radiation. The cooling power can achieve greater than 100 W/m2 without evaporation. All materials are inexpensive and amenable to scalable manufacturing techniques, which could lower the cost of the system.

Stony Brook University

Condensing Flue Gas Water Vapor for Cool Storage

Stony Brook University will work with Brookhaven National Laboratory, United Technologies Research Center, and the Gas Technology Institute to develop a thermosyphon system that condenses water vapor from power plant flue gas for evaporative cooling. The system could provide supplemental cooling for thermoelectric power plants in which the combustion process - burning fossil fuel to produce heat - results in a significant quantity of water vapor that is typically discharged to the atmosphere. In Stony Brook's system, an advanced loop thermosyphon will allow the liquid and vapor phases to flow in the same direction, and the working fluid (water) is actively managed with a fluid delivery system to create a thin film on the wall of the thermosyphon. This thin film will enable significantly higher heat transfer rates than traditional thermosyphon evaporators that use a pool of liquid. The cooled flue gas condensate is then stored and used for subsequent evaporative cooling when the ambient temperature exceeds acceptable operating limits, such as on a hot day when a dry-cooling system alone could not cool water sufficiently for reuse. In addition to creating a novel design and control architecture, the team will also design innovative, polymer-based components to minimize corrosion from the flue gas. The team estimates its system can capture 320,000 gallons of water per day for evaporative cooling, helping to eliminate the consumption of local water resources for evaporative cooling on high-temperature days.

TDA Research, Inc.

Novel Desiccant Cycle for Flue Gas Water Recovery and Cool Storage

TDA Research (TDA) will develop a water recovery system that extracts and condenses 64% of the water vapor produced by the gas turbine in a natural gas combined cycle's (NGCC) power plant and stores this water for use in evaporative cooling. The system will provide supplemental cooling to NGCC power plants in which the combustion process - burning the natural gas to produce heat - produces a significant quantity of water vapor that is typically discharged to the atmosphere. First, a direct-contact condensation cycle will recover 27% of water vapor from the flue gas. To increase the amount of water recovered, a desiccant, which is a substance that attracts water, will be used to absorb an additional 37% of the water vapor. TDA's desiccant cycle utilizes the waste heat in the exhaust to regenerate the desiccant for reuse. This water recovery cycle would occur during cooler months when the water from combustion is easier to capture. Much of the water collected during this period will then be stored in an adjacent lake and saved for use during hotter summer months when evaporative cooling offers the maximum benefit to improve power plant efficiency. The project team estimates that its technology can reduce the performance penalty of a dry-cooling system by 30% compared to wet cooling. Moreover, the team is designing the system to use low-cost materials, which reduces capital costs.

The Boeing Company

A Case Study on the Impact of Additive Manufacturing for Heat/Mass Transfer Equipment used for Power Production

The Boeing Company is developing a next-generation air-cooled heat exchanger by leveraging technological advances in additive manufacturing (AM). The work builds on a previous ARPA-E IDEAS award to the University of Maryland that included the fabrication of geometrically complex heat exchanger coupons. Boeing subsequently demonstrated AM fabrication of thin-walled structures with a thickness of 125 to 150 microns, which represents a 50% reduction relative to then-state-of-the-art AM processes. The high temperature heat exchanger currently under development employs complex internal geometries to achieve an expected 20-30% improvement in thermal performance and up to 20% reduction in weight. Current manufacturing techniques include manual stacking of heat exchangers, brazing in a thermal vacuum chamber, and welding of external features. Each of these manufacturing steps is time consuming, expensive, and may damage the part. A validated AM process for heat exchangers could lead to fabrication cost savings well in excess of 25% by eliminating these steps. If successful, these high performance, lightweight heat exchangers would enable more energy-efficient aircraft. AM can also expand the design space for heat exchangers, enabling advanced designs that conform to challenging form factor requirements. Advances in efficient air-side cooling could also have significant spillover benefits in additional industries such as power plant and distributed energy systems, automotive, air-conditioning and refrigeration, power electronics, and chemical processing.

University of Cincinnati

Enhanced Air-Cooling System with Optimized Asynchronously-Cooled Thermal Energy Storage

University of Cincinnati (UC) researchers will develop a dry-cooling system, featuring an enhanced air-cooled condenser and a novel daytime peak-load shifting system (PLSS) that will enable dry cooling for power plants even during hot days. The team will transform a conventional air-cooled condenser by incorporating flow-modulating surfaces and modifying the tubular geometry of the system, both of which will reduce heat transfer resistance and increase the thermal surface area. Whenever the air temperature becomes too high for the air-cooled heat exchanger to be effective, the PLSS will cool the air inlet temperature back down to acceptable temperatures. This inlet air-cooler technology removes heat from the incoming air and stores it in a thermal energy storage (TES) system that incorporates phase-change materials, which can store and release heat over a range of temperatures. During periods when the ambient air is cooler, the TES will release the stored heat to the atmosphere. Together, the combined innovations could quadruple the condenser's coefficient of performance, while the system's compact design will result in a smaller footprint than other air-cooled designs.

University of Colorado, Boulder

Radiative Cooled-Cold Storage Modules and Systems (RadiCold)

Researchers from the University of Colorado at Boulder (CU-Boulder) will develop Radicold, a radiative cooling and cold water storage system to enable supplemental cooling for thermoelectric power plants. In the Radicold system, condenser water circulates through a series of pipes and passes under a number of cooling modules before it is sent to the central water storage unit. Each cooling module consists of a novel radiative-cooling surface integrated on top of a thermosiphon, thereby simultaneously cooling the water and eliminating the need for a pump to circulate it. The microstructured polymer film discharges heat from the water by radiating in the infrared through the Earth's atmosphere into the heat sink of cold, deep space. Below the film, a metal film reflects all incoming sunlight. This results in cooling with a heat flux of more than 100 W/m2 during both day and nighttime operation. CU-Boulder will use roll-to-roll manufacturing, a low-cost manufacturing technique that is capable of high-volume production, to fabricate the microstructured RadiCold film.

University of Maryland

Novel Microemulsion Absorption Systems For Supplemental Power Plant Cooling

The University of Maryland (UMD) and its partners will utilize a novel microemulsion absorbent, recently developed by UMD researchers, for use in an absorption cooling system that can provide supplemental dry cooling for power plants. These unique absorbents require much less heat to drive the process than conventional absorption materials. To remove heat and cool condenser water, microemulsion absorbents take in water vapor (refrigerant) and release the water as liquid during desorption without vaporization or boiling. UMD's technology will use waste heat from the power plant's flue gas to drive the cooling system, eliminating the need for an additional power source. The design will improve upon the efficiency of commercially available chillers by 300%, even though the cost and size of UMD's technology is smaller. The indirect, absorption cooling system will lower condenser water temperatures to below the ambient temperature, which will ensure the efficiency of power plant electricity production.

University of Maryland

Novel Polymer Composite Heat Exchanger for Dry Cooling of Power Plants

The University of Maryland (UMD) and its partners will utilize UMD's expertise in additive manufacturing (3D printing) and thermal engineering to develop novel, polymer-based, air-cooled heat exchangers for use in indirect dry-cooling systems. The innovation leverages UMD's proprietary, cross media heat exchanger concept in which a low-cost, high-conductivity medium, such as aluminum, is encapsulated as a fiber in a polymeric material to facilitate more effective heat dissipation. To realize the innovative heat exchanger design, the team will develop an advanced, multi-head, composite 3D printer. The heat exchanger modules will be arranged in uniform rows with large spacing between the rows, which optimizes heat transfer while allowing for easier cleaning and maintenance. In addition to the system's advanced cooling capacities, the heat exchangers will also be low-cost, low-weight, and resistant to corrosion. Ideally, UMD's technology will be used in conjunction with a direct contact steam condenser in order to provide power plant cooling with performance comparable to evaporative, or wet-cooling, systems. UMD estimates that additive manufacturing could enable transformational heat exchanger designs with high performance at low cost, including the potential for onsite manufacturing of the heat exchanger, which could save additional transportation and installation costs.

University of Wisconsin

Optimized Air-Side Heat Transfer Surfaces via Advance Additive Manufacturing

The University of Wisconsin and its partner Oak Ridge National Laboratory will develop enabling technologies for low-cost, high-performance air-cooled heat exchangers. The objective is to create an optimization algorithm in order to identify and design a novel heat exchanger topology with very high heat transfer performance. The team also plans to develop a high-thermal conductivity polymer composite filament that can be used in additive manufacturing (3D printing) to produce the high-performance heat exchanger design. Due to the design freedom enabled by additive manufacturing, the team plans to develop 3D heat exchanger geometries that optimize heat transfer and decrease the total footprint required for an air-cooled system. Both of these innovations could enhance air-side heat transfer and improve the efficiency and cost of heat exchangers.
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