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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Unconventional desalination: The use of cyclone separators in HDH desalination to achieve zero liquid discharge

Research in water desalination technologies is constantly growing to meet global demands for freshwater. Though acting to meet these demands, the rapid growth and spread of desalination technologies poses environmental issues due to the increasing brine concentrates that are ultimately discharged back to nature. This article presents a cyclone separator to transform a humidification-dehumidification (HDH) cycle to a dual-product cycle to produce freshwater and solid salt crystals for highly saline streams. A desalination cycle equipped with a cyclone separator is used to treat water with 3.5%–81% salinity. The separation efficiency is well above 99% and can produce potable water from hyper saline feed in a once-through process. Further, the cyclone separator performance was tested under different conditions including humidity ratios, relative humidities, and feed stream's salinities. The cyclone separator is self-cleaning and overcomes salt scaling. This behavior is a direct function of the walls' temperature and the carrier air dew point. Self-cleaning capability allows the cyclone separator to treat feed water of extreme salinities (up to 810,000ppm) down to freshwater salinity with zero liquid discharge. The cyclone separator was utilized in a novel HDH desalination technology to treat different salinities. The product was freshwater of salinity <500ppm.

42 ENGINEERING↗
DOE OSTI2021

Sandwich-Structured Photothermal Wood for Durable Moisture Harvesting and Pumping

Moisture capture coupled with photothermal regeneration provides an alternative and sustainable way to acquire fresh water. Composite moisture absorbents based on hygroscopic salts are environmentally friendly, economically feasible, and of high efficiency but suffer from the unavoidable desiccant leakage during absorption and evaporation-induced salt accumulation on material surfaces during desorption. Additionally, in this study, we develop a superhydrophobic–hydrophilic–hydrophobic photothermal wood embedded with CaCl 2 to promote the durability of the absorbents. The sandwich structure serves as a liquid/vapor gate allowing vapor transport but forbidding liquid permeation, enabling the condensation and evaporation within the wood. Beyond moisture harvesting, the sandwich-structured photothermal wood exhibits potential in indoor dehumidification by pumping the moisture through an absorption–desorption cycle.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The levelized cost of exergy: a technoeconomic framework for energy system comparison

While the levelized costs of electricity and heat have been quantified before, these two metrics cannot be directly compared, due to the different exergy content of heat and work. To address this, we develop a levelized cost of exergy (LCOEx) framework that enables direct comparisons between energy sources and processes. We find that moderate- and high-grade heat have an LCOEx that is comparable to electricity (5–10 ¢ per kWh ex ), while low-grade heat sources have much higher LCOEx values (>50 ¢ per kWh ex ). The LCOEx of a system's output is affected by (i) the LCOEx of the system input, (ii) the CAPEX of the system, and (iii) the exergetic efficiency of the system. We use our framework to identify which processes are already achieved with relatively high cost effectiveness (production of fuels, hydrogen, and ammonia) and which have room for improvement (dehumidification, food production).

08 HYDROGEN↗
DOE OSTI2022

Electrohydrodynamic Enabled Electrochemical Membrane Dehumidifier for Separate Sensible and Latent Cooling

In hot and humid parts of the world, air conditioning is a necessity for an adequate standard of living. Cooling and heating represent one-third of building energy consumption. When cooling humid air, a substantial amount of the cooling energy is absorbed by water vapor condensation. The dehumidification cooling load is referred to as the latent cooling load and the dry bulb cooling load is referred to as the sensible cooling load. In most residential applications, the total cooling load is processed by a vapor compression cycle. Processing the latent load separately would not only reduce energy consumption. It would also reduce the required refrigeration capacity. Refrigerants often have adverse ecological impacts, contributing to the greenhouse effect and depletion of the ozone layer. Reduction of the cooling capacity in a system could reduce the amount of refrigerant charge required.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Enhanced cooling tower technology for power plant efficiency increase and operating flexibility

The Final Report describes the results of the work completed during the “Enhanced Cooling Tower Technology for Power Plant Efficiency Increase and Operating Flexibility” project. The objectives of work were to develop and demonstrate the prototype (up to 100 kWth) of an economically viable “all weather” Sub-Dew Point Cooling Tower (SDPCT) with inlet air cooling and dehumidification including testing in laboratory-controlled environment for simulating various ambient conditions. The inlet air is cooled and dehumidified by a Pressure Dehumidifying System (PDHS) installed at the cooling tower inlet.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2021

Opportunities for Catalytic Reactions and Materials in Buildings

Residential and commercial buildings are responsible for over 30% of global final energy consumption and accounts for ~40% of annual direct and indirect greenhouse gas emissions. Energy efficient and sustainable technologies are necessary to not only lower the energy footprint but also lower the environmental burden. Many proven and emerging technologies are being pursued to meet the ever-increasing energy demand. Catalytic science has a significant new role to play in helping address sustainable energy challenges, particularly in buildings, compared to transportation and industrial sectors. Thermally driven heat pumps, dehumidification, cogeneration, thermal energy storage, carbon capture and utilization, emissions suppression, waste-to-energy conversion, and corrosion prevention technologies can tap into the advantages of catalytic science in realizing the full potential of such approaches, quickly, efficiently, and reliably. Catalysts can help increase energy conversion efficiency in building related technologies but must utilize low cost, easily available and easy-to-manufacture materials for large scale deployment. This entry presents a comprehensive overview of the impact of each building technology area on energy demand and environmental burden, state-of-the-art of catalytic solutions, research, and development opportunities for catalysis in building technologies, while identifying requirements, opportunities, and challenges.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Extreme Water Uptake of Hygroscopic Hydrogels through Maximized Swelling‐Induced Salt Loading

Abstract Hygroscopic hydrogels are emerging as scalable and low‐cost sorbents for atmospheric water harvesting, dehumidification, passive cooling, and thermal energy storage. However, devices using these materials still exhibit insufficient performance, partly due to the limited water vapor uptake of the hydrogels. Here, the swelling dynamics of hydrogels in aqueous lithiumchloride solutions, the implications on hydrogel salt loading, and the resulting vapor uptake of the synthesized hydrogel–salt composites are characterized. By tuning the salt concentration of the swelling solutions and the cross‐linking properties of the gels, hygroscopic hydrogels with extremely high salt loadings are synthesized, which enable unprecedented water uptakes of 1.79 and 3.86 gg −1 at relative humidity (RH) of 30% and 70%, respectively. At 30% RH, this exceeds previously reported water uptakes of metal–organic frameworks by over 100% and of hydrogels by 15%, bringing the uptake within 93% of the fundamental limit of hygroscopic salts while avoiding leakage problems common in salt solutions. By modeling the salt‐vapor equilibria, the maximum leakage‐free RH is elucidated as a function of hydrogel uptake and swelling ratio. These insights guide the design of hydrogels with exceptional hygroscopicity that enable sorption‐based devices to tackle water scarcity and the global energy crisis.

Graeber, Gustav↗
DOE OSTI2022

Influence of the Anions on the Interaction Energy between Water and Ionic Liquids

It is essential to understand the interaction energy between water and ionic liquids (ILs) in search of ILs for dehumidification applications. In this paper, the intermolecular interaction energy between water and 1-ethyl-3-methylimidazolium ([EMIM])-based ILs was investigated. The vapor-liquid equilibrium data were first measured for solutions of [EMIM][BF 4 ], [EMIM][N(CN) 2 ], [EMIM][CF 3 SO 3 ], and [EMIM][CH 3 SO 3 ] with water molar fractions of 8–95 % at temperatures of 303–343 K. The IL-IL and water-IL intermolecular interaction energies were determined by using the correlated non-random two-liquid model. The results revealed that fluorine atoms in anions reduce the attraction energy between IL and water, and thus, decrease the water affinity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Desalination metamodels and a framework for cross-comparative performance simulations

There is an opportunity to save energy and reduce operational expenses when choosing a suitable desalination method aided by computational modeling. Existing models are not conducive to generalized comparisons between different desalination methods. Therefore, the work in this study developed metamodels for six desalination methods, grouped them into thermal and molecular transport families, and validated their predictive performance within 9% difference from published data. This validated framework allowed comparisons of desalination methods at their prescribed ranges of operational conditions that they were designed for. These conditions specify feed salinity ranges of 1.6 to 2.4 g/kg for Capacitive Deionization and Reverse Osmosis (RO), 2.8 to 4.2 g/kg for Electrodialysis, 28 to 42 g/kg for Thermovapor Compression and Humidification-Dehumidification, and 37 to 55 g/kg for Multi-Effect Distillation (MED). Despite different operational conditions, all models exhibit non-linear, positive correlation between energy consumption and system size in response to feed salinity and production rate. The framework is also employed in a cross-comparative analysis between MED and RO whose results suggest that energy intensity for MED is an order of magnitude greater than RO for the same operational conditions, but actual operational costs are comparable. Overall, the framework is ready for deployment in case studies of actual desalination plants.

42 ENGINEERING↗
DOE OSTI2022

Modeling and experimental validation of direct contact crossflow packed beds condenser used in HDH desalination systems

Humidification and dehumidification (HDH) desalination systems are alternatives to reverse osmosis desalination systems, especially for high salinity waters. A HDH system is essentially equipped with a humidifier (also called as evaporator) for air to pick up vapor from saline water, a dehumidifier (also called as condenser) to produce freshwater, and a heating source. HDH systems based on direct contact packed beds heat exchangers have remarkably lower costs than traditional HDH systems due to their inexpensive materials and simple configurations. This paper specifically focuses on direct contact crossflow packed beds condensers, in which cooling water vertically drips through the packed beds, directly contacting the horizontal air-vapor flow. A two-dimensional mathematical model that solves for the enthalpy values of the working fluids is proposed in this paper, and the PDEs are solved using finite differences. To validate the model, an experimental condenser was built and tested. Water temperatures inside the test section at twenty-nine locations were measured, as well as the air vapor temperatures of five locations at the outlet. The measured water and air-vapor temperatures agree with the simulation results with less than 10 % error in most of the compared domain.

42 ENGINEERING↗
DOE OSTI2020

Performance study of the cross-flow Maisotsenko cycle in humid climate conditions

This paper presents a first numerical analysis of the cross-flow Maisotsenko cycle (M-Cycle) below dew-point evaporative cooler for humid climates with model including the water vapor condensation phenomenon. Proposed solution allows to cool ambient air below its dew-point temperature, by utilizing cooling energy in air extracted from the building, due to that it can be used as effective pre-cooling solution for traditional systems. Proposed unit has significant advantage over traditional counter and cross-flow units operating in heat recovery mode, hence it is almost insensitive on temperature of exhaust air. This is caused by effective pre-cooling of the exhaust air in its initial part. Operation in humid climates using cold extracted air results in condensation occurrence in the primary air channels, and hence partial dehumidification of the primary airflow (which allows to cool the air before its dew- point temperature). The Maisotsenko cycle exchanger used to recover heat in the air-conditioning system is compared with Maisotsenko exchanger that operates only on the ambient airflow and does not allow to recover heat from the exhaust airflow from a conditioned space. Achieved results showed that M-Cycle below dew-point air cooler can operate more effectively in humid climates than traditional cross-flow Maisotsenko cycle exchanger.

Condensation↗
DOE OSTI2025

Material properties of aqueous potassium acetate solutions for use in liquid desiccant air conditioning

We present thermophysical properties of aqueous potassium acetate solutions relevant to their application as a liquid desiccant in air-conditioning systems. Liquid desiccant air conditioners could provide up to 80% energy savings compared to high-efficiency vapor compression air conditioners. However, the commonly used liquid desiccants, particularly chloride salt solutions, are highly corrosive. This precludes the use of metallic components, necessitating specialized plastics and thereby driving up cost, weight, and limiting operational temperature and pressure ranges. Potassium acetate has been identified as a less corrosive alternative, potentially enabling broader material compatibility in LDAC components. In this study we systematically measured and modelled key thermophysical properties of KAc solutions density, vapor pressure, viscosity, specific heat capacity, phase behavior, and diffusion coefficient across a range of concentrations (10 - 70wt%) and temperatures. For instance, KAc exhibits a vapor pressure of 3.1 kPa at 50wt% and 40degrees C, demonstrating dehumidification capability comparable to chloride salts. By providing an extended dataset and associated models, this work advances the understanding needed to design energy-efficient, corrosion mitigating LDAC system.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Additively manufactured multiplexed inertial coalescence filters

Multiphase flows often pose a significant challenge to the efficient and reliable design of thermofluidic systems. This paper describes multiplexed inertial coalescence filters composed of parallel helical pathways, designed to capture fine droplets (<40 µm) through inertial separation while maintaining a low pressure drop (<400 Pa). Filtration efficiencies for 7 µm and 30 µm droplets were characterized for varying flow conditions, with complete capture observed above a threshold flow rate. Models for filtration efficiency and pressure drop were developed and validated against experimental results to allow system design and optimization, enabled by the tunable additive manufacturing approach used to fabricate the filters. Filter quality factor was computed for varying droplet sizes, showcasing exceptional quality factor when compared to state-of-the-art filters documented in the literature. In conclusion, this multiplexed inertial coalescence filtration approach could find use in dehumidification systems, fog harvesting, chemical reactors, and microgravity droplet capture.

3D Printing↗
DOE OSTI2026

Elucidating the Microscale Behavior and Phase Separation Kinetics of Thermally Responsive Ionic Liquid–Water Mixtures

Thermally responsive ionic liquids (ILs) exhibit liquid-liquid phase separation into a water-rich (WR) and ionic-liquid-rich (ILR) phase when heated above a lower critical solution temperature (LCST). This phase behavior has been leveraged for applications ranging from forward osmosis (FO) desalination, where the IL acts as a draw solute, to refrigeration and dehumidification cycles, where the IL acts as a liquid desiccant. While significant effort has been devoted to characterizing the thermodynamic and thermophysical properties of LCST ILs, their phase separation kinetics have not been investigated. In this work, we describe the macroscale phase separation kinetics (phase separation time) by gleaning insight into the microscale colloidal behavior of aqueous mixtures of four different materials, P 4444 TFA (tetrabutylphosphonium-2,4-trifluoroacetate), P 4444 DMBS (tetrabutylphosphonium-2,4-dimethyl-benzenesulfonate), N 4444 Sal (tetrabutylammonium salicylate), and P 4444 Sal (tetrabutylphosphonium salicylate) as a function of IL concentration at a separation temperature of 70 °C. We report the discontinuous microscale size distributions for each material and correlate their theoretical settling velocities to experimental phase separation times. The results indicate that a simple Stokes' law model can predict the phase separation time within reasonable accuracy. Overall, this work lays the foundation for understanding the micro- to macroscale phase separation behavior and kinetics of LCST ILs for various water-energy applications.

LCST↗
DOE OSTI2020

Improving AHU Performance by Minimizing Approach Temperature, Reducing Air Maldistribution, and Efficiently Handling Sensible and Latent Loads (Phase 1 Interim Final Technical Report)

Residential air handling units (AHUs) have stayed the same in form and efficiency for the past 30+ years, with incremental improvements made to address safety, functionality, and energy-efficiency. The purpose of this research in Phase I, Topic 9a: Next Generation Residential Air Handlers, was to improve AHU performance by minimizing heat exchanger (HX) approach temperature, reducing air maldistribution, and developing alternative system configurations which more efficiently handle sensible and latent loads. In this research Optimized Thermal Systems (OTS) developed, modeled, and evaluated multiple alternative system concepts. A dual vapor compression system separate sensible and latent cooling (SSLC) concept was studied to inform work on alternative concepts and to show best-case performance benefit. System concepts included ejector enhanced vapor compression cycles, desiccant assisted dehumidification, dual evaporator SSLC, and alternative AHU HX configurations. A dual vapor compression system showed COP improvement of 20%, however, required additional components, increased unit size, and increased cost. Two types of ejector enhanced vapor compression cycles with dual evaporators improved system COP by 9 to 11%, and reduced AHU losses by as much as 18%, with design changes limited to the AHU, no unit physical size increase, and a moderate increase to system first cost. Desiccant assisted air-conditioning required increased air flow rate resulting in higher fan power and the desiccant wheel increased sensible heat load leading to increased compressor power and reduced system COP. Dual evaporator cycles were found to degrade performance due to increased expansion losses. Optimized single slab HX designs used in place of the traditional A-coil HX led to 44–49% reduction in aluminum, 47–60% less refrigerant charge, and improved HX velocity distribution.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Mobile Sorption-based Thermal Battery for Harvesting Low-Temperature Geothermal Energy

Around 20% of the total primary energy in the United States is consumed for thermal demands of buildings such as space cooling, dehumidification, and space heating (EIA 2018). Low-temperature geothermal energy is abundant and can effectively satisfy buildings’ thermal demands. However, low-temperature geothermal energy is underutilized because the energy density of geothermal fluid is too low to justify the costs associated with transporting it between existing geothermal resources and buildings. The mobile sorption-based thermal battery (MSTB) system has been developed using three-phase (i.e., vapor–liquid, solution–solid, crystal) sorption technology to harvest low-temperature heat and store it with a much higher energy density than the geothermal fluid. The energy density of salt crystals is over six times higher than geothermal fluid, which makes long-distance transportation of salt crystals economically feasible. Salt crystals can be used to dehumidify air or provide space cooling in buildings, which alleviates peak demand on the electricity grid by offsetting electricity use for these end uses. This helps improve the grid’s stability and resilience. High-energy storage density, fast crystallization, and dissolution of salt crystals are all critical to the viability and performance of the MSTB system. Therefore, the design and operation of MSTB systems need to ensure effective generation and dissolution of salt crystals inside the MSTB. To achieve this target, this seedling project developed an experimental apparatus for characterizing the crystallization and dissolution processes. The energy density and potential latent cooling capacity of the MSTB are also evaluated based on lab test results. The crystallization results showed that the generated lithium chloride hydrate crystals are fluffy, the crystallization process lasts about 50 min, and the maximum crystal fraction (i.e., the ratio of crystal mass to the mass in the MSTB) can be up to 51.1% of the total mass in the MSTB at a solution flow rate of 1.58 g/s. The dissolution results show that the salt crystals in the MSTB can be fully dissolved within 15–28 min, based on different test conditions. Reducing solution flow rate and cooling water temperature can achieve increased energy storage density and crystal fraction. While the increase in the discharge rate (i.e., latent cooling capacity for dehumidifying air) is achieved by increasing flow rate and temperature of inlet diluted solution, as well as by using a pump for internal solution circulation, the discharge rate increases by 38%, from 0.95 kW to 1.31 kW. Compared with increasing the inlet solution flow rate, power consumption of salt solution transportation can be reduced by using a pump for internal solution circulation. The crystallization test results also showed that the maximum energy storage density is 981.8 kJ/kg, and the maximum discharge rate of the dissolution tests is ≤1.79 kW. Both are above the target values of 900 kJ/kg and 1.75 kW) for this project. The work reported here proves the feasibility and advancement of the MSTB system, which is helpful to the further study and improvement of the MSTB system.

15 GEOTHERMAL ENERGY↗
DOE OSTI2021

Field Validation of a Smart Energy Recovery Ventilation System Using Low-Cost Indoor Air Quality Sensors

This project is a field validation, using low-cost indoor air quality (IAQ) sensors, of a smart ventilation system that can help low-load homes in humid environments maintain acceptable indoor humidity conditions while providing adequate ventilation according to ASHRAE 62.2. The objectives of this research were to (1) address builders’ concerns with mechanical ventilation in humid environments and (2) answer the question of whether smart control logic helps with occupant comfort and the creation of a more acceptable indoor environment. To address the objectives of the study, the Southface team collected field data for one year in four Charleston, South Carolina, new construction homes in order to determine the differences in occupant comfort; comfort metrics; IAQ; and heating, ventilating, and air-conditioning (HVAC) energy consumption when toggling biweekly between an energy recovery ventilator (ERV) operating continuously and an ERV operating with smart, time-varying humidity control logic. The smart ventilation algorithm under consideration in this field test did create a less humid indoor environment on an annual basis as quantitatively measured through temperature and relative humidity (T/RH) readings, expressed most discernably as “percentage of time above 60% RH” and “percentage of time above 55°F dewpoint.” However, the difference it made was inconsistent during the spring, summer, and fall months, and it was only directionally consistent during the winter months. We suspect that this is primarily due to the long runtimes and concomitant dehumidification activity of the air-conditioning (A/C) units in response to the high sensible loads in Charleston. The effect of the smart ventilation algorithm was not discernable to the occupants in this study, as recorded through seasonal surveys.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗