Water Use Reduction at Thermoelectric Plants


Topic Area 1 Projects

Topic Area 1 Lead:

Per Peterson, UC BerkeleyPer Peterson, UC Berkeley
CV | Website






Conventional approaches to reducing water consumption in thermoelectric plants typically result in reduced efficiency and increased carbon dioxide emissions. Technological breakthroughs in the areas of dry cooling, non-conventional power conversion, dry carbon- capture methods, and reduced fuel consumption are urgently needed in order to address electricity needs in regions where water is, or will become, scarce. The CERC-WET portfolio includes an array of research projects aimed at developing new approaches to reduce water consumption and carbon dioxide emissions from thermoelectric plants.

Specifically, in terms of reducing water use in modern thermal power plants, several projects in Topic Area 1 are applicable to IGFC (Integrated Gassification Fuel-cell Cycle) and NGFC (Natural Gas Fuel-cell Cycle), spanning from coal utilization to natural gas and biogas.  The IGFC saves water consumption exceeding 50% compared with current generation of thermal power plants, and has the potential to be water neutral.  Several projects are applicable also to NGCC (Natural Gas Combined Cycle) to reduce water consumption, are compatible with dry cooling, and approach zero water consumption. 



Project 1.1: Dry CO2 capture based on nanoscale framework materials

Jeffrey Long, UC BerkeleyJeffrey Long, UC Berkeley
CV | Website

Context: Post-combustion CO2-capture process requires large amounts of energy and water. By replacing traditional aqueous amine absorbent capture technology with solid adsorbents, savings in both energy and water resources can be realized.
Objective: Identify the diamine-appended metal-organic framework best suited to minimize this energy and water consumption. Develop strategies and partnerships to advance technology readiness of the chosen adsorbent through scale-up, process modeling and slipstream testing. 

The Long Group recently discovered a class of solid adsorbents that can capture CO2 with minimal impact on water and energy resources. These materials, diamine-appended metal–organic frameworks of the form (diamine)2M2(dobpdc) (dobdc4– = 2,5-dioxidobenzene-1,4-dicarboxylate), feature inorganic nodes connected by organic dobpdc4– ligands to form one-dimensional, hexagonal channels of 18 Å diameter. One end of each dibasic diamine species binds each metal site lining the channels; this orients the other end of the diamine into the pore to initiate the capture process upon exposure to acidic CO2 gas.

The choice of a solid adsorbent allows the fundamental benefit of capture technology that can function without need for water or other solvents, which can comprise up to 70% of the volume of traditional amine absorbers. Further, adsorbents can afford intrinsically lower regeneration energy requirements due to the elimination of energy inputs in a temperature swing process associated with the high heat capacity of water. Beyond these fundamental gains, we are able to achieve unparalleled working capacities and energy savings with the diamine-appended M2(dobpdc) frameworks by virtue of their recently-elucidated mechanism of operation: CO2 binding takes place in a cooperative manner, resulting in step-like adsorption isotherms with onset pressures that increase with increasing temperature.

While classical adsorbents with Langmuir-type adsorption profiles require either significant heating or vacuum to initiate regeneration, we can regenerate materials with step-shaped adsorption profiles simply by decreasing the pressure or increasing the temperature. This allows access to full working capacity of the material by positioning the operating partial pressure of CO2 below that of the critical step pressure. Importantly, we have found that this threshold adsorption pressure for our materials can be tuned over 6 orders of magnitude by varying the constituent metal and diamine.

Metal–organic frameworks are highly promising new materials for next-generation technology in selective gas adsorption. In this project, we will identify the diamine-appended metal–organic framework best suited to minimize energy and water consumption in a post-combustion CO2 capture process. The greatest challenge in this endeavor will be selecting the specific step position and corresponding material that can minimize the temperature swing required for regeneration while preserving performance in the presence of H2O and other common flue gas components. Based on our preliminary screening of over 100 diamine-appended adsorbents, we are confident in our ability to deliver an optimal solid adsorbent for CO2 capture. 


Milner, Phillip J., et al. "A Diaminopropane-Appended Metal–Organic Framework Enabling Efficient CO2 Capture from Coal Flue Gas via a Mixed Adsorption Mechanism." Journal of the American Chemical Society 139.38 (2017): 13541-13553.


Project 1.2: Reheat air combined cycles (RACC)

Per Peterson, UC BerkeleyPer Peterson, UC Berkeley
CV | Website

Context: Molten salts can transport and store heat at temperatures useful for combined cycle power conversion, enabling coupling to non-fossil energy sources including nuclear reactors and concentrating solar power towers.
Objective: Evaluate RACC system performance with computer simulation and experiments, with specialized models for heat exchange, duct, and thermal storage systems. Collaborate with Chinese partners to develop a roadmap to achieve the major outcomes projected by 2020. 

A key factor affecting the use of fission reactors and concentrating solar power (CSP) in regions with scarce water has been their relatively low operating temperatures, resulting in low thermal efficiency in power conversion and significant water consumption for cooling.  Fluoride salts have emerged as a technologically interesting option for heat transport in these applications because they can transfer heat in the temperature range from 600-850°C using currently available structural materials. The near-term demonstration of a 370-kW molten fluoride salt test loop is expected to occur in China at the Shanghai Institute of Applied Physics before 2020, complementing parallel research efforts in the U.S. and at UC Berkeley. 

UC Berkeley has investigated a range of power conversion technologies optimized to this temperature range, and recently found that conventional gas-turbine combined-cycle thermo-electric plants can be reconfigured to produce base-load electricity using these heat sources, providing highly-flexible, dispatchable peaking power by co-firing with natural or syn-gas. In this configuration, a modified GE 7FB can generate 100 MWe operating with a turbine inlet temperature of 670°C and a single stage of reheat. Co-firing with gas to increase the turbine inlet temperature in the second expansion stage can boost power output to 242 MWe. This enables Reheat Air Combined Cycle (RACC) power conversion to produce rapidly dispatchable peaking power, with 66% efficiency in converting gas to electricity, significantly reducing CO2 emissions to produce peak power.

Furthermore this efficiency is sufficiently high that high-temperature thermal storage using electric-resistance heating with off-peak power should be feasible and attractive, because electric resistance heating can heat firebrick thermal storage media to temperatures >1200°C. This type of thermal storage warrants further investigation because of its potential low cost and potential net efficiency >60%. In the first year of this project, we develop plans for a test facility to demonstrate air heating by molten salts at temperatures and pressures of interest for combine cycle power conversion. In subsequent years we will perform scaled separate-effect test experiments and modeling for air heating and thermal storage for RACC, and will work with Chinese partners to develop the test facility and demonstrate air heating in a closed-loop system. 


Andreades, Charalampos, and Per Peterson. "Nuclear Air Brayton Combined Cycle and Mark 1 Pebble Bed Fluoride-Salt-Cooled High-Temperature Reactor economic performance in a regulated electricity market." Nuclear Engineering and Design (2016).

Andreades, C., Greenop, A., Gallagher, S., Choi, J. K., & Peterson, P. Coiled Tube Air Heater Test Loop Design. In 2017 25th International Conference on Nuclear Engineering(pp. V009T15A053-V009T15A053). American Society of Mechanical Engineers, (2017, July).


Project 1.3: Integrated gasification and natural gas hybrid fuel cell power plants

Scott Samuelsen, UC IrvineScott Samuelsen, UC Irvine
CV | Website

Context: Integrated solid oxide fuel cell (SOFC) gas turbine (GT) hybrid power plants can contribute to achieving air quality and climate goals. Higher efficiency of hybrids reduces heat rejection and makeup water to wet cooling towers typically used.

Objective: Develop integration schemes to fully realize the potential of hybrid SOFC/GT power plants in small to large scale applications with fossil and renewable bio fuels. 

Fuel cell power plants can help achieve air quality and climate goals through several high value attributes, including high efficiency, ultra-low pollutant emissions, zero demand for water, and near zero acoustic emissions. When integrated into a Brayton cycle, the resultant “hybrid” technology releases the Carnot Efficiency constraints (due to materials limitations) and combustion pollutant emissions of the heat engine and thereby results in highly efficient generation of electricity with coal, natural gas, and/or biogas from central plant generation to distributed generation. The solid oxide fuel cell (SOFC) is a suitable fuel cell for these applications. This research will develop integration schemes to fully realize the potential of hybrid SOFC/GT systems in both central plant and distributed generation applications. 

Central plant Integrated Gasification Fuel Cell (IGFC)/gas turbine hybrid technology, combining coal and/or biomass gasification, is deployable at large scales (~100 MW). IGFC has the potential to generate electricity at efficiencies approaching 60% on coal higher heating value (HHV) basis, while capturing >90% of the evolved CO2 with substantially reduced water demand. Operated on natural gas in the absence of gasification, the NGFC hybrid has the potential for efficiencies approaching 75%. The higher overall plant thermal efficiency of SOFC/GT hybrid power plants leads to a lower amount of heat rejection, thus requiring less makeup water to wet the cooling towers typically used in current power plants. Further, by keeping the anode and the cathode exhaust gases separate, the H2O vapor entering with the fuel and formed by fuel oxidation may be more easily recovered by cooling the anode exhaust gas, because the H2O vapor will be at a much higher partial pressure than typical flue gases. This further reduces the net water consumption of the plant.

SOFC/GT hybrid technology is ideal for distributed power generation fueled either by natural gas or biogas derived from sources such as wastewater treatment facilities and landfills. Further, because of the increasing demand on electric grids to support high penetrations of intermittent renewables, enhance power quality, increase reliability and resiliency, and provide ancillary services, local power is being generated on both sides of the meter in the U.S. and may also be expected in China in the future. Clusters of SOFC/GT hybrids in the size range of 10 to100 MW, referred to as Transmission Integrated Grid Energy Resource (TIGER) Stations, are ideal to enable electric grid support by providing baseload and various levels of load following services.


Rosner, F., Chen, Q., Rao, A., Samuelsen, S., Jayaraman, A., & Alptekin, G. (2019). Thermo-economic analyses of IGCC power plants employing warm gas CO2 separation technology. Energy185, 541-553.

Rosner, F., Rao, A., & Samuelsen, S. (2020). Water gas shift reactor modelling and new dimensionless number for thermal management/design of isothermal reactors. Applied Thermal Engineering, 115033


Project 1.4: Dry cooling for steam condensation

Yanbao Ma, UC MercedYanbao Ma, UC Merced
CV | Website

Context: Approximately 1% of thermoelectric power plants utilize air-cooled condensers due to much lower thermal efficiency compared with water-cooled condensers.

Objective: Develop enhanced modular air-cooled condensers (EMACC) to increase the air-side heat transfer coefficient, hair about 3X without net increase in pressure drop. 

To improve the hair of the ACCs by a factor of 3 requires a transformative heat sink design that can introduce flow disturbances to generate significant vorticity without large frictional losses as air flows cross the heat sink surfaces. The innovative design of the EMACC relies on the integration of four effective vortex generation mechanisms for hairenhancement: (a) corrugated fins; (b) a punched delta wing vortex generator array; (c) a V-shape winglet vortex generator array; and (d) dimpled surface design. The major challenge is to optimize the design with a large number of design parameters in conjugate heat transfer. To overcome this challenge, we will implement a new optimization methodology using a volume-averaging theory (VAT) hierarchical physical model and a genetic algorithm (GA) numerical optimizer.

We will achieve this objective through the following four tasks:

Subtask 1.4.1 Conduct CFD simulations for parametric studies of wavy fin with longitudinal vortex generators (LVGs) on both sides of the fin surface [Goal: demonstrate a 2X improvement in the hair compared with that of flat fins];

Subtask 1.4.2 Conduct targeted CFD simulations for design and assessment of dimpled surface [Goal: identify two most promising dimpled surface designs];

Subtask 1.4.3  Develop a design and optimization tool based on CFD-VAT [Goal: demonstrate the validity of the CFD-VAT design tool];

Subtask 1.4.4  Find the optimal design of a lab-scale EMACC with 3X improvement in the hair[Goal: demonstrate the 3X improvement goal is achieved]. 


Project 1.5: Synthesis of flexible, low-temp thermoelectrics and heat exchangers

Jeffrey Urban, LBNLJeffrey Urban, LBNL
CV | Website

Context: Our custom hybrid materials provide water-free cooling and also enable waste heat recovery for co-generation. We aim to eliminate high water consumption on spray cooled condensers. 

Objective: Prepare nanostructured phase-change "tapes" (PCT) that do water-free cooling, providing passive thermal management. Additionally, our materials perform energy co-generation via direct thermal to electrical energy conversion (DTEC), thus reducing water use and enhancing energy generations.

Two important levers to reduce water-intense energy generation needs are: (1) increasing the productive use of waste heat from plant operations, which enhances the efficiency of energy generation while mitigating water cooling needs; and (2) using heat exchangers that enhance dry heat transfer coefficients and make water-free cooling more efficient. Recent advances in novel classes of hybrid thermoelectric and thermal interface materials now enable efficient direct thermal-to-electrical energy conversion (DTEC) with exceptional performance below 400°C and zero net water dissipation. Average energy conversion efficiencies from power plants range from 35-55%, thus plants are typically rejecting hundreds of MW of low temperature waste heat, which we propose to use for energy generation. 

         The Urban group has expertise in design of hybrid inorganic/ organic materials that have best-in-class thermoelectric power conversion efficiencies and are made using scalable room temperature, solution processing methods. Uniquely, these devices also offer customizable engineering – our devices are made in flexible and conformable form-factors that facilitate ease of implementation and widespread utilization/retrofitting. The scientific innovation in this project will be to optimize our materials systems to best match and utilize the specific waste-heat temperatures required for industry, as DTEC efficiency is dependent upon a complex mix of material-specific parameters. Our group has developed a new strategy to overcome these limitations using simple, stable, surface atomic modifications; we will customize these solutions for the specific CERC partner interests.                       

            In addition, we propose to deliver water-free passive cooling solutions with cooling capacities that approach that of water. Here, we take advantage of the fact that the latent-heat of melting in nanocrystalline materials is size-dependent and can be tuned across a wide range by simple chemical growth processes. We will use these characteristics to prepare nanostructured phase-change “tapes” that can be directly applied to hot surfaces where water or spray cooling is used—the nanocrystalline materials will go through phase transition locally on the hot side, absorbing heat, and will then re-radiate this heat on the cool side due to their large surface area and high emissivity. While supplemental air-cooling may be used to enhance this effect if necessary, we have demonstrated water free cooling in preliminary results.


Project 1.6: Nanostructured surface enhancement of spray cooling water vaporization processes

Van Carey, UC BerkeleyVan Carey, UC Berkeley
CV | Website

Context: Inadequate heat transfer and high water consumption for water spray cooling of power plant air cooled condensers.

Objective: Develop scalable methods to create nanostructured superhydrophilic surface coatings on aluminum, and experimentally assess coating durability and effectiveness to enhance heat transfer and reduce water consumption for water spray cooling of power plant air cooled condensers.



Nanostructured superhydrophilic surfaces enhance impinging water droplet vaporization through spreading and thin film evaporation. This can result in lower steam condensing temperatures as well as higher power cycle efficiency and reduced water consumption. Significant progress in these areas could be made through the development of durable, low-cost superhydrophilic heat exchanger surface coatings that provide highly effective spray cooling heat transfer performance with ultra-low water usage. Applications include reduction of water use for spray cooling of power plant condensers, water desalinization, and manufacturing process such as water quenching of metal forgings and castings. 

Our recent preliminary studies have shown that coating a metal copper substrate with a layer of ZnO nanorods creates a superhydrophilic surface that enhances droplet impingement heat transfer and eliminates loss of water by ejection of splash-created droplets. We fabricated this nanostructured ZnO coating by depositing ZnO nanoseeds on a prepared copper surface using a scalable thermal growth methodology. This coating is durable under conditions typical of spray cooling of power plant condensers.

Our major challenge is to develop a superhydrophilic thin film coating for an aluminum substrate that simultaneously enhances heat transfer, maximizes the reduction of water use, and is robust, durable, and inexpensive to produce. We will achieve this goal through three research tasks: (1) Adapt to aluminum the ZnO nanostructured surface fabrication methodology we have used successfully to create superhydrophilic surface coatings on copper substrates. [goal: Create a durable nanostructured coating on aluminum with water contact angles less than 3˚.] (2) Fabricate coatings with at least three different nanoscale surface geometries on aluminum substrates to facilitate the experimental heat transfer testing of the surfaces. [goal: Fabricate nanostructured surperhydrophilic surfaces with three different nansocale geometries on aluminum and document them using the electron microscope imaging and wetting experiments.] (3) Conduct experiments to determine how nanoscale geometry variations affect impinging droplet spreading and the resulting evaporation heat transfer for the different nanosurface geometries on the aluminum substrates fabricated in Task 2, and compare our experimental results to Volume of Fluid (VOF) CFD predictions of droplet impingement fluid dynamics and heat transfer. [goal: Complete droplet spreading and heat transfer testing on three different nanoscale coating geometries on aluminum and document them using the electron microscope imaging and wetting experiments.] (3) Conduct experiments to determine how nanoscale geometry variations affect impinging droplet spreading and the resulting evaporation heat transfer for the different nanosurface geometries on the aluminum substrates fabricated in Task 2, and compare our experimental results to Volume of Fluid (VOF) CFD predictions of droplet impingement fluid dynamics and heat transfer. [goal: Complete droplet spreading and heat transfer testing on three different nanoscale coating geometries on aluminum substrates, and define the best nanoscale superhydrophilic coating design for enhancement of spray cooling of aluminum air cooled condensers.]

Figure 1 displays a time lapse of a droplet being deposited on one of the coated surfaces.

Figure 1: Water droplet deposited on zinc oxide coated Aluminum surface. Superhydrophilic spreading observed.

The rate at which water wicks out on the surface is one of 2 main metrics used to quantify the wettability of the surface. The second is total spreading area. The larger the droplet spreads, the thinner the resulting water droplet is. In a heat transfer situation, this can lead to thin film evaporation, which is a highly effective method of cooling. Figure 2 shows the maximum spreading for a 2μL droplet on the coated surface.

Figure 2: Water droplet spreading on a zinc oxide nano-coated surface.


Mizerak, J.P. and Carey, V.P., Modeling Of Transport During Droplet Deposition And Spreading On Smooth And Microstructured Superhydrophilic Surfaces , Proceedings of the ASME 2016 International Mechanical Engineering Congress & Exposition IMECE 2016, November 11-17, 2016, Phoenix, USA.

Kunkle, C.M. and Carey, V.P., Metrics For Quantifying Surface Wetting Effects On Boiling And Evaporation At Nanostructured Hydrophilic Surfaces, paper PRTEC-15163, Proceedings of the First Pacific Rim Thermal Engineering Conference, PRTEC, March 13-17, 2016, Hawaii's Big Island, USA. 

Kunkle, C.M. and Carey, V.P., Metrics for Quantifying Surface Wetting Effects on Vaporization Processes at Nanostructured Hydrophilic Surfaces, paper HT2016-7203, Proceedings of the ASME 2016 Summer Heat Transfer Conference HT2016, July 10-14, 2016, Washington, DC, USA.

LaBrie, Russell J., Jorge Padilla Jr, and Van P. Carey. "Experimental Study of Aqueous Binary Mixture Droplet Vaporization on Nanostructured Surfaces." Heat Transfer Engineering 38.14-15 (2017): 1260-1273.

Kunkle, Claire M., Jordan P. Mizerak, and Van P. Carey. "The Effects of Wettability and Surface Morphology on Heat Transfer for Zinc Oxide Nanostructured Aluminum Surfaces." ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017.

Wemp, C.K. and Carey, V.P., Tuning Superhydrophilic Nanostructured Surfaces To Maximize Water Droplet Evaporation Heat Transfer Performance, paper IMECE2017-72679, presented and included in the Proceedings of the ASME 2017 International Mechanical Engineering Congress and Exposition, November 3-9, 2017, Tampa, Florida, USA.

Wemp, Claire K., and Van P. Carey. "Water Wicking and Droplet Spreading on Randomly Structured Thin Nanoporous Layers." Langmuir 33.50 (2017): 14513-14525.

Wemp, Claire K., and Van P. Carey. "Tuning Superhydrophilic Nanostructured Surfaces to Maximize Water Droplet Evaporation Heat Transfer Performance." Journal of Heat Transfer140.10 (2018): 102401.

Carey, V. P., Wemp, C. K., McClure, E. R., & Cabrera, S. (2018, November). Mechanism Interaction During Droplet Evaporation on Nanostructured Hydrophilic Surfaces. In ASME 2018 International Mechanical Engineering Congress and Exposition (pp. V08AT10A029-V08AT10A029). American Society of Mechanical Engineers.

Wemp, C. K., & Carey, V. P. (2019). Heat transport for evaporating droplets on superhydrophilic, thin, nanoporous layers. International Journal of Heat and Mass Transfer, 132, 34-51.

Project 1.7: Durable encapsulation of thermoevaporation brines using coal combustion residuals

Photo of Prof. Gaurav SantGaurav Sant, UCLA
CV | Website

Context: Coal combustion produces flue gas desulfurization wastewater which contains high abundances of alkalis, halide species, and sulfates. It is sought to encapsulate this liquid waste stream using solid coal combustion residuals (e.g., fly ash) to form stable solids, which can be landfilled.
Objective: To develop a computational, and design framework that allows prescription / matching of liquid waste streams with suitable coal combustion residuals, and chemical additives to form durable solids which effectively reduce wastewater volume, and offer effective containment of ionic species. 

Coal combustion produces a multiplicity of solid, liquid and gaseous waste streams. On account of their compatibility, often the solid (fly ash) and liquid waste streams may be combined thereby encapsulating each other prior to disposal in a landfill. The solid minerals remaining from coal combustion form the fly and bottom ash which have cementitious properties and have been used extensively in the construction industry. The liquid faction is produced from the effluent of the flue gas desulphurization (FGD) process and is highly concentrated in salts and dissolved metals. These wastes when combined with each other form a cohesive solid that consists of a multiplicity of hydrated compounds. However, understanding of compatibility, and lack thereof remains limited, as a result of which extensive trial and error operations are needed to define compatible, and appropriate (i.e., which fulfill dual criteria of cohesion and hydraulic conductivity) waste encapsulation solutions.

Thermodynamic modeling based on the minimization of Gibbs free energies can be used to rapidly identify, screen and define robust formulations for brine encapsulation in relation to the brine chemistry, fly ash (FA) composition, across a range of additives including: lime, ordinary Portland cement (PC), calcium aluminate cement (CAC), and/or gypsum. Simulation of the stable phases formed based on the chemistry available in the system will assist in assessing the ideal additive, liquid and FA ratios. The current objectives for the project are: a) Quantifying the extent of brine volume reduction (consumption) in relation to brine and solid composition, b) Characterizing the distributions of solid phases in relation to brine and solid composition, c) Understanding the effects of different additives (e.g., different cement chemistries, lime, etc.) on a) and b), d) Understanding the evolution of coarse porosity of the stabilized solid in relation to brine and solid composition, e) Developing mixture proportioning criteria for brine encapsulation, and, f) Generalized cost analysis of brine encapsulation based on different additive types and mass ratios.


© Copyright UC Regents. All Rights Reserved.  
Privacy | Accessibility | Nondiscrimination