Hard-Magnet L1[subscript 0]-CoPt Nanoparticles Advance Fuel Cell Catalysis
Abstract not provided
Li, Junrui↗
Engineering topics
Shen, Bo
Publications and source records attributed to Shen, Bo.
Energy and Economics Analyses of Condenser Evaporative Precooling for Various Climates, Buildings and Refrigerants
Condenser evaporative pre-coolers provide a low cost retrofit option for existing packaged rooftop air conditioning application units. This paper aimed to provide a comprehensive study to assess energy savings and peak power reductions of condenser evaporative cooling. Condenser evaporative cooling leads to a lower temperature of the air entering the condenser of a rooftop unit, which results in smaller compressor power consumption. Utilizing EnergyPlus building energy simulations, we mapped the impacts on energy savings and energy reductions at peak ambient temperatures in three building types and 16 locations with levels of pad effectiveness and demonstrated the effects on air conditioner using either R22 or R410A as refrigerants. Economics and control strategy to maximize the cost saving were also investigated. The conclusions demonstrate that energy savings are much greater for HVAC systems with the refrigerant R410A than they are with R22, and evaporative pre-cooling provides the opportunity for annual energy savings and peak demand reductions, with significant potential in hot, dry climates. Additionally, we validated an improved mathematical model for estimating the condenser pre-cooling wet bulb efficiency which shows clear advantage over the current EnergyPlus model.
29 ENERGY PLANNING, POLICY, AND ECONOMY↗
Life cycle cost analysis comparing redesigned CCHP to existing heat pump systems for cities in cold climates
This report indicates that the project progress has met the Go criterion, i.e. demonstrating favorable results of life cycle cost assessment for the redesigned CCHPs. Considering the market price of a baseline heat pump, and required improvements in heat exchangers, fans and an electronic expansion valve of the CCHPs, we estimated that the CCHP using a 3-stage scroll compressor will incur with a cost increment of $\$386$ per rated cooling tonnage, and the CCHP using tandem compressors will increase by $\$770$. Based on the energy savings of the CCHPs, simulated by EnergyPlus, the two CCHPs achieve payback periods less than 4 years among all the cold climate cities. Within a typical heat pump life cycle of 20 years, the CCHPs can achieve cost savings around $\$2000$ per rated cooling tonnage, and the savings are even higher for the extremely cold cities like Duluth and Fairbanks.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Gasification of coal and biomass as a net carbon-negative power source for environment-friendly electricity generation in China
Realizing the goal of the Paris Agreement to limit global warming to 2 °C by the end of this century will most likely require deployment of carbon-negative technologies. It is particularly important that China, as the world’s top carbon emitter, avoids being locked into carbon-intensive, coal-fired power-generation technologies and undertakes a smooth transition from high- to negative-carbon electricity production. We focus here on deploying a combination of coal and biomass energy to produce electricity in China using an integrated gasification cycle system combined with carbon capture and storage (CBECCS). Such a system will also reduce air pollutant emissions, thus contributing to China’s near-term goal of improving air quality. We evaluate the bus-bar electricity-generation prices for CBECCS with mixing ratios of crop residues varying from 0 to 100%, as well as associated costs for carbon mitigation and cobenefits for air quality. We find that CBECCS systems employing a crop residue ratio of 35% could produce electricity with net-zero life-cycle emissions of greenhouse gases, with a levelized cost of electricity of no more than 9.2 US cents per kilowatt hour. A carbon price of approximately $52.0 per ton would make CBECCS cost-competitive with pulverized coal power plants. Therefore, our results provide critical insights for designing a CBECCS strategy in China to harness near-term air-quality cobenefits while laying the foundation for achieving negative carbon emissions in the long run.
01 COAL, LIGNITE, AND PEAT↗
Accelerating renewable energy electrification and rural economic development with an innovative business model: A case study in China
Not Available
Li, Changsheng (ORCID:0000000202251036)↗
Development of HPWH System Model, Using All Microchannel Heat Exchangers
In this report, 24-hour energy factor (EF) and first-hour draw rating (FHR) simulations were conducted on two heat pump water heater systems (HPWHs), one using a fin-and-tube evaporator and wrapped-tank condenser coil with D-shape tubes, and the other using a micro-channel evaporator and wrapped-tank condenser coil with microchannel tubes. Alternative refrigerants as drop-in replacements of R-134a were evaluated, including R-1234yf, R-1234ze(E), propane (R-290), R-450A and R-513A. The results are summarized below: 1.Microchannel heat exchangers can decrease the system charge down to 30% relative to fin-and-tube evaporator and wrapped-tank D tubes.2.Having the same contact surface area to the water tank and evaporator frontal flow area, the system using microchannel heat exchangers (MHXs) results in 5% efficiency degradation. Due to the very small cross-sectional flow area of a microchannel tube, MHXs tend to have multiple parallel tubes to restrict the refrigerant pressure drop. The parallel pattern can’t utilize the water temperature stratification as effectively as the D-shape tubes, which are arranged in one or two circuits and counter flow to the water stratification. 3.Refrigerant drop-in system simulations were conducted for R-1234yf, R-1234ze(E), propane, R450A and R513A in comparison to R-134a. Among the alternatives, propane has the largest volumetric capacity, which results in shortest HPWH run time and highest first-hour rating. Propane leads to the smallest energy factor because its largest volumetric capacity overloads the heat exchangers. R-1234ze(E) has the smallest volumetric capacity, highest energy factor, but smallest first-hour rating. R-1234yf, R-450A and R-513A achieve similar performance indices as R-134a. 4.Propane requires the least refrigerant mass (45% relative to R-134a). If a wrapped-tank microchannel condenser and microchannel evaporator are used, the required system charge can be limited below 150 grams, which makes it feasible to use propane for domestic HPWH.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Annual Energy Savings and Peak Power Reduction Simulated for CCHP Design and Baseline HP in Cold Climate Cities
This report assesses energy savings and peak power reduction of three heat pumps in multiple US cold climate cities and building types. The three heat pumps comprise a baseline heat pump and two high efficiency cold climate heat pumps (CCHP). The DOE/ORNL Heat Pump Design Model was used to simulate the heat pumps and generate performance curves for EnergyPlus building energy simulations. The annual energy simulations were performed over seven cold climates: 1) Minneapolis, MN; 2) Duluth, MN; 3) Fairbanks, AK; 4) Helena, MT; 5) Indianapolis, IN; 6) Peoria, IL and 7) Eagle County, CO. In order to assess impact of residential building types matching different energy codes, we simulated six single-family houses in Indianapolis, IN, including : 1) single-family house having a crawlspace; 2) having a slab foundation; 3) having a heated basement; 4) having an unheated basement; 5) one single-family house having a heated basement matching IECC code of 2009, 6) and one single-family house having a heated basement matching IECC code of 2012. The former 4 houses match the IECC 2006 code.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
An efficient correlation for heat and mass transfer effectiveness in tumble-type clothes dryer drums
A heat and mass transfer effectiveness definition relevant to clothes dryers is developed in this work. A correlation is presented for determining the effectiveness of heat and mass transfer in a horizontal-axis, tumble-type clothes dryer drum with axial airflow. The correlation is a function of four measurable quantities: air mass flow rate, cloth mass, air mass in the drum, and the fall time experienced by a cloth falling the full height (i.e. diameter) of the drum. The Buckingham Pi Theorem is applied to the problem in order to derive dimensionless terms upon which the effectiveness depends. Empirical data from several dryers are used to derive an empirical correlation as a function of the dimensionless variables. Three cloth types were investigated, and a separate empirical correlation is proposed for each. Accordingly, the drum effectiveness concept and the correlation presented provide a new, more accurate, computationally efficient, and readily implemented framework for modeling and simulating clothes dryers. It is relevant to conventional gas and electric clothes drying appliances, vapor compression heat pump dryers, and thermoelectric heat pump clothes dryers. Along with appropriate empirical inputs, the framework is extensible to any thermal-evaporative cloth drying systems, including radial-flow horizontal axis tumble drying drums.
42 ENGINEERING↗
Cost-Optimized CCHP Model Developed Using HPDM Meeting Performance Targets
This report documents the equipment design and analysis work to meet the first project milestone (M1). Our industry partner, Emerson Commercial & Residential Solutions recently developed a 3-stage scroll compressor product, able to deliver capacity at three levels without using an inverter. Based on ORNL’s previous cold climate heat pump (CCHP) prototype and the preliminary compressor performance data, the CCHP was redesigned for cost reduction and better performance. The 3-stage compressor, using the middle capacity level to deliver the rated capacity of the heat pump (HP), will replace the previous tandem compressors, using one single-speed compressor to deliver the rated capacity. In this way, it will reduce the compressor footprint to fit in most residential HPs’ chassis. The compressor replacement increases the nominal capacity by 17%. Approximately, 30% cost reduction in the compressor and 17% reduction in the heat exchangers per nominal tonnage can be achieved relative to the prior tandem compressor design. Advanced features using an electronic expansion valve for head pressure control and an Ebm-papst variable-speed, backward-curved indoor blower can be adopted for higher efficiency.The DOE/ORNL Heat Pump Design Model (HPDM) was used to model and redesign the CCHP. Following AHRI 210/240, heating and cooling performance results were predicted at the conditions for certifying a 2-stage CCHP, regarding various design scenarios. The predicted HSPF reaches 12.0, and predicted SEER reaches16.2.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Low-GWP Refrigerant Evaluation in AC Systems for High Ambient Temperature Applications – Acquire Nortek Residential AC/HP Units for Evaluation and Model the Units Using HPDM
For the upcoming refrigerant transition from HFCs to minorly flammable HFO refrigerants (A2L), refrigerant charge reduction is important to mitigate the fire hazard. Microchannel heat exchangers (MHXs) are a mature technology, which is effective in reducing system charge while maintaining similar heat transfer performance. MHXs will be applied more widely when the new refrigerants are used. Prior studies of the A2L HFO blends were mostly focused on fin-and-tube coils (FTC). An in-depth study for an air conditioner (AC)/heat pump (HP) system using all microchannel heat exchangers is still lacking. In FY19, a side-to-side comparison will be conducted between two residential split heat pumps, one using all FTCs and the other using all MHXs for drop-in investigation, to identify potential issues for future design. The two heat pumps have similar rated capacity, SEER, HSPF levels, similar fan, blower and compressor, but differ in heat exchangers. Both the HPs use two-stage compressors to facilitate investigating different refrigerant flow rates. We will drop-in HFO refrigerants (replacements for R-410A, e.g. R452B, R447B, R32, etc.). The experiments will reveal the potential of MHXs for charge reduction, and how the two systems using A2L refrigerants operate under standard SEER and HSPF rating conditions. The two units were donated by our partner, i.e. Nortek Global HVAC, an industry leader in making heat pumps using all MHXs as well as FTCs. The units were shipped to ORNL this week, and the product design data were also shared for modeling the two units using HPDM.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Extending ORNL HPDM Capabilities for Design and Optimization of New Refrigerant Blends – FY19 1st Quarterly Milestone Report: Development of Heat Pump System Models (Space Heating) for HFO Blends
We recently published numerous heat pump system models at the HPDM website, in the category of “Space Heating”. The published system configurations include single-stage heat pumps using TXV for expansion or a short-tube fixed-orifice coupled with a suction line accumulator, a two-stage heat pump system putting two compressors in series, single state heat pump using two parallel compressors (tandem), vapor injection systems with a vapor injection compressor coupled with an intermediate economizer or a flash tank. These configurations should cover all the residential heat pump products on the market. Additionally, to accelerate the refrigerant transition and make thousands of existing compressor maps reusable by the new refrigerants, ORNL created a mathematical approach to scale typical vapor injection compressor maps, developed from one baseline refrigerant to be used by the new HFO refrigerants/blends.
42 ENGINEERING↗
Optimal scheduling of isolated microgrid with an electric vehicle battery swapping station in multi-stakeholder scenarios: A bi-level programming approach via real-time pricing
In order to coordinate the scheduling problem between an isolated microgrid (IMG) and electric vehicle battery swapping stations (BSSs) in multi-stakeholder scenarios, a new bi-level optimal scheduling model is proposed for promoting the participation of BSSs in regulating the IMG economic operation. In this model, the upper-level sub-problem is formulated to minimize the IMG net costs, while the lower-level aims to maximize the profits of the BSS under real-time pricing environments determined by demand responses in the upper-level decision. To solve the model, a hybrid algorithm, called JAYA-BBA, is put forward by combining a real/integer-coded JAYA algorithm and the branch and bound algorithm (BBA), in which the JAYA and BBA are respectively employed to address the upper- and lower- level sub-problems, and the bi-level model is eventually solved through alternate iterations between the two levels. The simulation results on a microgrid test system verify the effectiveness and superiority of the presented approach.
29 ENERGY PLANNING, POLICY, AND ECONOMY↗
Heat Pump Water Heater Using Wrapped-Tank Microchannel Condenser Coil for Charge Reduction – FY19 1st Quarter (Regular) Milestone Report: Development of Wrapped-Tank Condenser Model (Round Tube and Microchannel), Coupled with Water Tank Model
We recently grew the DOE/HPDM model library to enhance its heat pump water heater (HPWH) design and simulation capability. The new additions include wrapped-tank round tube coil, microchannel coil and a one-dimensional stratified water tank. A wrapped-tank condenser coil has strong coupling with a stratified water tank, which leads HPWH simulation a transient process. The new one-dimensional stratified water tank model is an improvement to the open-source EnergyPlus water tank model, by introducing a calibration factor to account for bulk mixing effect due to water draws and circulations, etc. The wrapped-tank condenser coil model, using a segment-to-segment modeling approach to simulate round tubes or microchannel ports. The heat exchanger models can accept arbitrary refrigerant types, e.g. HFCs, HFOs, natural refrigerants like CO 2 and propane, etc.
42 ENGINEERING↗
Chemical Synthesis of Magnetically Hard and Strong Rare Earth Metal Based Nanomagnets
Abstract We report a general chemical approach to synthesize strongly ferromagnetic rare‐earth metal (REM) based SmCo and SmFeN nanoparticles (NPs) with ultra‐large coercivity. The synthesis started with the preparation of hexagonal CoO+Sm 2 O 3 (denoted as SmCo‐O) multipods via decomposition of Sm(acac) 3 and Co(acac) 3 in oleylamine. These multipods were further reduced with Ca at 850 °C to form SmCo 5 NPs with sizes tunable from 50 to 200 nm. The 200 nm SmCo 5 NPs were dispersed in ethanol, and magnetically aligned in polyethylene glycol (PEG) matrix, yielding a PEG‐SmCo 5 NP composite with the room temperature coercivity ( H c ) of 49.2 kOe, the largest H c among all ferromagnetic NPs ever reported, and saturated magnetic moment ( M s ) of 88.7 emu g −1 , the highest value reported for SmCo 5 NPs. The method was extended to synthesize other ferromagnetic NPs of Sm 2 Co 17 , and, for the first time, of Sm 2 Fe 17 N 3 NPs with H c over 15 kOe and M s reaching 127.9 emu g −1 . These REM based NPs are important magnetic building blocks for fabrication of high‐performance permanent magnets, flexible magnets, and printable magnetic inks for energy and sensing applications.
Shen, Bo↗
Chemical Synthesis of Magnetically Hard and Strong Rare Earth Metal Based Nanomagnets
We report here a general chemical approach to synthesize strongly ferromagnetic rare-earth metal (REM) based SmCo and SmFeN nanoparticles (NPs) with ultra-large coercivity. The synthesis started with the preparation of hexagonal CoO+Sm 2 O 3 (denoted as SmCo-O) multipods via decomposition of Sm(acac) 3 and Co(acac) 3 in oleylamine. These multipods were further reduced with Ca at 850 °C to form SmCo 5 NPs with sizes tunable from 50 to 200 nm. The 200 nm SmCo 5 NPs were dispersed in ethanol, and magnetically aligned in polyethylene glycol (PEG) matrix, yielding a PEG-SmCo 5 NP composite with the room temperature coercivity (H c ) of 49.2 kOe, the largest H c among all ferromagnetic NPs ever reported, and saturated magnetic moment (M s ) of 88.7 emu g -1 , the highest value reported for SmCo 5 NPs. The method was extended to synthesize other ferromagnetic NPs of Sm 2 Co 17 , and, for the first time, of Sm 2 Fe 17 N 3 NPs with H c over 15 kOe and M s reaching 127.9 emu g -1 . These REM based NPs are important magnetic building blocks for fabrication of high-performance permanent magnets, flexible magnets, and printable magnetic inks for energy and sensing applications.
36 MATERIALS SCIENCE↗
Extending ORNL HPDM Capabilities for Design and Optimization of New Refrigerant Blends – FY18 2nd Quarter Milestone Report: Improve HPDM to Adopt New Refrigerant Properties and Correlations
We added new refrigerant properties of HFO blends to the ORNL HPDM, including R-22 alternatives, i.e. N20b, DR3, ARM20a, ARM20b, R444B, DR93; R-410A alternatives, i.e. R447A, R447B, R452B, R32, ARM71a; R-134a alternatives, i.e. R1234yf and R1234ze. It can also simulate natural refrigerants, e.g. propane (R290), Isobutane (R600a), CO2 and Ammonia. In addition, latest heat transfer and pressure drop correlations best for low GWP refrigerants were integrated to the equipment design and simulation software.
36 MATERIALS SCIENCE↗
ECC Refrigerator: Develop a system model using electrochemical (ECC) compressor and metal hydride (MH) heat exchangers- FY18 2nd Quarter Milestone Report
This report describes equations for modeling electrochemical compressors and metal hydride heat exchangers. We developed two new component models into the HPDM model library. Two system simulations were conducted, one was a water heating system using LaNi5, and the other was a refrigeration system using V0.85Ti0.1Fe0.05. The simulations demonstrated that COPs of the electrochemical compression systems decreased drastically with increasing the electric current and capacity, due to reduced electrochemical compression efficiency at larger ohm resistance loss. Cyclic loss caused by the metal hydride and heat exchanger mass had a secondary effect on the system efficiency. Elimination of the heat exchanger cyclic loss could enhance the water heating COP of the LaNi5 system by 12% and increase the refrigeration COP of the V0.85Ti0.1Fe0.05 system by 7%.
42 ENGINEERING↗
Low-GWP Refrigerant Evaluation in AC Systems for High Ambient Temperature Applications - Design and Simulation Practice to Identify Charge Reduction Opportunities for Residential AC/HP Units
Based on three 5-ton, single-speed heat pumps (HPs), using R-410A, which use the same compressor, indoor blower and outdoor fan, the DOE/ORNL Heat Pump Design Model was used to conduct comparative modelling study. Regarding charge reduction opportunities, in general, we recommend: 1. Downsizing the outdoor condenser will reduce the required system charge, i.e. using smaller tube diameters or fewer tubes; reducing the evaporator inner volume is less important; to offset the reduced condenser tube side surface area, one can increase the air side surface area (fin density) or condenser air flow rate via using a more efficient fan. 2. microchannel heat exchangers are most effective in reducing the required charge, by up to 60% in the condenser and evaporator. To develop low charge systems, one should at least use a microchannel heat exchanger as the outdoor condenser. 3. TXV systems are less sensitive to charge reduction. For the drop-in application, one can decrease the charge to minimize the liquid section in the condenser, at the expense of minor performance degradation; for example, when reducing the system charge by 15% (decrease the subcooling degree to 2R), the simulation results prove that the decrease is less than 3% in the EER and less than 6% in the capacity.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗