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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Model predictive control for optimal dispatch of chillers and thermal energy storage tank in airports

Cost of energy consumption is one of the biggest operational cost for airports, and it is increasing from time to time as airports expand to support growing number of passengers. Various factors affect the energy consumption including efficiency of airport Heating Ventilation and Air conditioning (HVAC) systems, which in turn depends on the efficiency of individual subsystems. Here, in this paper, we present an optimal scheduling method for the central plant system at Dallas Fort Worth airport, involving chillers, pumps, and a thermal energy storage (TES) system. A model predictive control (MPC) problem is formulated to minimize both energy and demand charge costs while satisfying the cooling needs of the airport. The proposed Mixed-Integer Nonlinear Programming (MINLP) formulation includes performance curve based models for chillers and pumps and a simplified state of charge model for TES. The formulation also includes predictions of cooling load and chilled water return temperature. Simulation results for a month in summer show savings around 10% compared to the baseline. Initial recommendations based on insights from simulation results to the manual operation procedures resulted in significant savings. Field test results show a 7% chiller efficiency improvement.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Highly-Efficient Microemulsion-Based Absorption Chillers for HVAC Application

Air conditioning is a necessity to achieve a comfortable, habitable home or office for many places in US. However, vapor compression air conditioners are largely made with chlorofluorocarbon refrigerants, or CFCs, which create problems for a world grappling with climate change. In addition, vapor compression air conditioners are driven by electricity. Cooling and heating represent one-third of building electrical energy consumption in US. An absorption chiller is different to vapor compression chillers or air conditioners because it doesn’t use conventional refrigerants, like CFC. Instead, they may use water as the refrigerant which is mixed with safe and nontoxic absorbents. The research performed in this project advanced the understanding of absorption cooling technology and its application in HVAC. Various technologies were explored to improve the performance of the desorber and absorber components in the absorption chillers.

42 ENGINEERING↗
NASA NTRS1976

Measured performance of a 3 ton LiBr absorption water chiller and its effect on cooling system operation

A three ton lithium bromide absorption water chiller was tested for a number of conditions involving hot water input, chilled water, and the cooling water. The primary influences on chiller capacity were the hot water inlet temperature and the cooling water inlet temperature. One combination of these two parameters extended the output to as much as 125% of design capacity, but no combination could lower the capacity to below 60% of design. A cooling system was conceptually designed so that it could provide several modes of operation. Such flexibility is needed for any solar cooling system to be able to accommodate the varying solar energy collection and the varying building demand. It was concluded that a three-ton absorption water chiller with the kind of performance that was measured can be incorporated into a cooling system such as that proposed, to provide efficient cooling over the specified ranges of operating conditions.

Namkoong, D.↗
NASA NTRS1976

Measured performance of a 3-ton LiBr absorption water chiller and its effect on cooling system operation

A 3-ton lithium bromide absorption water chiller was tested for a number of conditions involving hot-water input, chilled water, and the cooling water. The primary influences on chiller capacity were the hot water inlet temperature and the cooling water inlet temperature. One combination of these two parameters extended the output to as much as 125% of design capacity, but no combination could lower the capacity to below 60% of design. A cooling system was conceptually designed so that it could provide several modes of operation. Such flexibility is needed for any solar cooling system to be able to accommodate the varying solar energy collection and the varying building demand. It is concluded that a 3-ton absorption water chiller with the kind of performance that was measured can be incorporated into a cooling system such as that proposed, to provide efficient cooling over the specified ranges of operating conditions.

Namkoong, D.↗
DOE OSTI2021

Improving chiller performance and energy efficiency in hydrogen station operation by tuning the auxiliary cooling

In a hydrogen station that operates with direct fueling through the use of a 700 bar boost compressor, the outlet hydrogen temperature can significantly increase, stressing the chiller system. Here, this paper evaluates improvements that can be made to the auxiliary cooling system integrated with the compressor. Both theoretical modeling and experiments were performed at Cal State LA Hydrogen Research and Fueling Facility. The findings suggest that adjusting the auxiliary closed-loop cooling system from 15 °C to 10 °C reduced the station energy consumption and decreased the demand on the station chiller that needed to provide –20 °C hydrogen at the hose. The overall energy consumption for a single fueling reduced by between 2.86 and 9.43% for the set of experiments conducted. After the temperature of the closed-loop cooling system was reduced by 5 °C, the boost compressor outlet temperature dropped from 46-50 °C–40 °C and consequently at the hose the hydrogen temperature declined by 3 °C. Results were scaled up with a forecast on the number of daily refueling events. With a low number of daily fuelings, the proposed set-up showed a minor influence on the overall station energy consumption. However, the benefits were more pronounced for a connector station with sales at 180 kg/day, where the energy efficiency improved by between 1.4 and 5.5%, and even more so for a higher capacity station at 360 kg/day, where the improvement was between 2.9 and 8%.

08 HYDROGEN↗
DOE OSTI2011

Truck Thermoacoustic Generator and Chiller

This Final Report describes the accomplishments of the US Department of Energy (DOE) cooperative agreement project DE-FC26-04NT42113 - Truck Thermoacoustic Generator and Chiller - whose goal is to design, fabricate and test a thermoacoustic piezoelectric generator and chiller system for use on over-the-road heavy-duty-diesel trucks, driven alternatively by the waste heat of the main diesel engine exhaust or by a burner integrated into the thermoacoustic system. The thermoacoustic system would utilize engine exhaust waste heat to generate electricity and cab air conditioning, and would also function as an auxiliary power unit (APU) for idle reduction. The unit was to be tested in Volvo engine performance and endurance test cells and then integrated onto a Class 8 over-the-road heavy-duty-diesel truck for further testing on the road. The project has been a collaboration of The Pennsylvania State University Applied Research Laboratory, Los Alamos National Laboratory, Clean Power Resources Inc., and Volvo Powertrain (Mack Trucks Inc.). Cost share funding was provided by Applied Research Laboratory, and by Clean Power Resources Inc via its grant from Innovation Works - funding that was derived from the Commonwealth of Pennsylvania. Los Alamos received its funding separately through DOE Field Work Proposal 04EE09.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2011

Development of a Low-Lift Chiller Controller and Simplified Precooling Control Algorithm. Final Report

KGS Buildings LLC (KGS) and Pacific Northwest National Laboratory (PNNL) have developed a simplified control algorithm and prototype low-lift chiller controller suitable for model-predictive control in a demonstration project of low-lift cooling. Low-lift cooling is a highly efficient cooling strategy conceived to enable low or net-zero energy buildings. A low-lift cooling system consists of a high efficiency low-lift chiller, radiant cooling, thermal storage, and model-predictive control to pre-cool thermal storage overnight on an optimal cooling rate trajectory. We call the properly integrated and controlled combination of these elements a low-lift cooling system (LLCS). This document is the final report for that project.

25 ENERGY STORAGE↗
DOE OSTI2017

Analysis of a nuclear hybrid energy system using absorption chillers and stratified chilled-water storage with an mPower reactor - 187

The intermittency of renewable energy technology, such as wind and solar power, puts strain on electric grids, often forcing carbon-based and nuclear sources of energy to operate in a load follow mode. Operating nuclear reactors in a load-follow fashion is undesirable due to the associated thermal and mechanical stresses placed on the fuel and reactor components. Various methods of Thermal Energy Storage (TES) can be coupled to nuclear (or renewable) power sources to help absorb grid instabilities caused by daily load demand changes and renewable intermittency. This is known as a Nuclear Hybrid Energy System (NHES). Previous research has found that a stratified chilled-water storage tank can help displace peak cooling loads to off-peak hours. In this study, a dynamic single effect, lithium bromide absorption chiller model was developed as a callable FORTRAN subroutine. Cooling towers, a stratified chilled-water storage tank, and cooling loads characteristic of a large campus were included to form a comprehensive TES model. This TES model was coupled to a high-fidelity mPower sized Small Modular Reactor (SMR) FORTRAN code that provides the transient behavior of primary and secondary-side components. Control algorithms based on excess capacity and conditions in the stratified chilled-water storage tank were used to determine when to divert low-pressure steam from the turbines to the absorption chillers in order to keep reactor power near steady-state. Simulation results depict how the TES system and SMR interact, and demonstrate that stratified chilled-water storage is a viable TES technology for an SMR in a NHES. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Parametric analysis and optimization of CO 2 trans-critical cycle for chiller application in a warm climate

This article presents parametric analysis and subsequent optimization of a CO 2 trans-critical chiller system operating in a warm climate. Additionally, high side pressure and gas cooler face velocities are two controllable parameters investigated. COP of the system is analyzed and optimized using a developed and validated mathematical model. The mean relative error of prediction in COP is found to be within ±10% for physics-based model and within ±1% for Artificial Neural Network (ANN) based model of the experimental findings. The validated mathematical model is utilized to predict optimal high side pressure as well as gas cooler face velocity for the varying ambient and evaporation conditions to achieve best possible COP. A possibility of 5.31% improvement in COP is found based on the optimization of parameters. In conclusion, the proposed methodology is deemed suitable for design and testing of control system for maximization of energy efficiency.

42 ENGINEERING↗
DOE OSTI2025

ComStock Measure Scenario Documentation: Chiller Replacement

Building on a 3-year effort to calibrate and validate the U.S. Department of Energy's ResStock (TM) and ComStock (TM) models, this work produces national datasets that empower analysts working for federal, state, utility, city, and manufacturer stakeholders to answer a broad range of questions regarding their commercial building stock. ComStock is a highly granular, bottom-up model that uses multiple data sources, statistical sampling methods, and advanced building energy simulations to estimate the annual energy consumption (at a subhourly resolution) of the commercial building stock across the United States. The baseline model intends to represent the U.S. commercial building stock as it existed in 2018. The methodology and results of the baseline model are discussed in the final technical report of the End-Use Load Profiles project. The goal of this work is to develop energy efficiency and demand flexibility end-use load shapes that cover high-impact, market-ready (or nearly market-ready) measures. "Measures" refers to various "what-if" scenarios that can be applied to buildings. An end-use savings shape is the difference in energy consumption between a baseline building (or collection of buildings) and a building with an energy efficiency or demand flexibility measure applied. It results in a time-series profile broken down by end use and fuel (electricity or on-site gas, propane, or fuel oil use) at each time step, as well as annual aggregations. This report describes the modeling methodology for a single end-use savings shape measure - chiller replacement - and briefly introduces key results. The full public dataset can be accessed on the ComStock (TM) data lake or via the Data Viewer at comstock.nrel.gov. The public data set enables users to create custom aggregations of results for their use case (e.g., filter to a specific county).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Site demonstration and performance evaluation of MPC for a large chiller plant with TES for renewable energy integration and grid decarbonization

Thermal energy storage (TES) for a cooling plant is a crucial resource for load flexibility. Traditionally, simple, heuristic control approaches, such as the storage priority control which charges TES during the nighttime and discharges during the daytime, have been widely used in practice, and shown reasonable performance in the past benefiting both the grid and the end-users such as buildings and district energy systems. However, the increasing penetration of renewables changes the situation, exposing the grid to a growing duck curve, which encourages the consumption of more energy in the daytime, and volatile renewable generation which requires dynamic planning. The growing pressure of diminishing greenhouse gas emissions also increases the complexity of cooling TES plant operations as different control strategies may apply to optimize operations for energy cost or carbon emissions. This paper presents a model predictive control (MPC), site demonstration and evaluation results of optimal operation of a chiller plant, TES and behind-meter photovoltaics for a campus-level district cooling system. The MPC was formulated as a mixed-integer linear program for better numerical and control properties. Compared with baseline rule-based controls, the MPC results show reductions of the excess PV power by around 25%, of the greenhouse gas emission by 10%, and of peak electricity demand by 10%.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2013

Project to Develop and Demonstrate an Advanced Low Temperature Heat Recovery Absorption Chiller Module at a Distributed Data Center

The proposed Low Temperature Absorption chiller project was to test and apply standard design operating strategies that will significantly enhance the single stage hot water fired absorber performance for CHP applications. The project was terminated because the host site required to serve at the basis of design and where measurement and verification testing was to be undertaken could not support the project in a manner consistent with the project delivery schedule.

Sweetser, Richard↗
DOE OSTI2017

Variable-Speed Screw Chiller, Sidney Yates Building, Washington, DC

This report captures the findings from an evaluation ORNL performed on a new chiller technology as part of GSA's Proving Ground Program. Note: Appendices B&C were removed from this report while the author looks for a way to insert them without consuming over 200MB of file size.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Preconcentrator with high volume chiller for high vapor pressure particle detection

Apparatus and method for collecting particles of both high and low vapor pressure target materials entrained in a large volume sample gas stream. Large volume active cooling provides a cold air supply which is mixed with the sample gas stream to reduce the vapor pressure of the particles. In embodiments, a chiller cools air from ambient conditions to 0-15.degree. C. with the volumetric flow rate of the cold air supply being at least equal to the volumetric flow rate of the sample gas stream. In further embodiments an adsorption media is heated in at least two stages, a first of which is below a threshold temperature at which decomposition products of the high vapor pressure particle are generated.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Monitoring Based Commissioning: Step-by-Step Approach to Implementation in Chiller Plants

Chilled water systems consume a significant portion of the energy in manufacturing, and inefficient operation could significantly influence utility bills and the environmental footprint of a facility. One way to ensure long-term energy-efficient plant operation is to ensure that chilled water system equipment, such as chillers, cooling towers, and pumps, are running at their best. Periodic operational assessments help to meet efficiency objectives for cooling plants. However, occasional set point and operational changes resulting from short-term fluctuations cause the plant operation to deviate from optimal. These changes accumulate over time, and operational efficiency deteriorates. Significant energy efficiency improvement potential in chilled water systems can be achieved by operational changes alone. Recent developments in information technology and the industrial internet of things data processing ability have overcome traditional problems and given rise to a new paradigm: monitoring-based commissioning (MBCx). Commissioning platforms and fault detection and diagnostics capabilities have evolved over time and presented more sophisticated abilities to efficiently control process cooling plants. The typical architectures of the MBCx process and a detailed approach to implement the process for chilled water systems are presented. A case study highlighting the energy-and cost-savings potential of MBCx systems is also presented.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗