Water, Air Emissions, and Cost Impacts of Air-Cooled Microturbines for Combined Cooling, Heating, and Power Systems： A Case Study in the Atlanta Region

The increasing pace of urbanization means that cities and global organizations are looking for ways to increase energy efficiency and reduce emissions. Combined cooling, heating, and power （CCHP） systems have the potential to improve the energy generation efficiency of a city or urban region by providing energy for heating, cooling, and electricity simultaneously. The purpose of this study is to estimate the water consumption for energy generation use, carbon dioxide （CO2） and NOx emissions, and economic impact of implementing CCHP systems for five generic building types within the Atlanta metropolitan region, under various operational scenarios following the building thermal （heating and cooling） demands. Operating the CCHP system to follow the hourly thermal demand reduces CO2 emissions for most building types both with and without net metering. The system can be economically beneficial for all building types depending on the price of natural gas, the implementation of net metering, and the cost structure assumed for the CCHP system. The greatest reduction in water consumption for energy production and NOx emissions occurs when there is net metering and when the system is operated to meet the maximum yearly thermal demand, although this scenario also results in an increase in greenhouse gas emissions and, in some cases, cost. CCHP systems are more economical for medium office, large office, and multifamilv residential buildings.

Forced Compressed Air Cooling System for a 300 MW Steam Turbine in Waigaoqiao Power Plant

The 300 MW steam turbine installed in Waigaoqiao Power Plant with combined HPIP cylinders of double casing structure is a product of the Shanghai Turbine Works utilizing licensed technology. It has a large heat storage capacity and good thermal insulation, so the metal temperature of first stage of HP cylinder (FSMTI) may reach 400-450℃ after shut down and it takes 7-8 days to cool to 150℃ by natural cooling, Now with a forced cooling system the cooling time may be reduced to 40 hours, so that the turbine may be opened for repair work in about 5-6 days. The cooling system for #2 unit and test procedure are briefly described below.

A Comprehensive Study of a Low-Grade Heat-Driven Cooling and Power System Based on Heat Current Method

Combined cooling and power(CCP)system driven by low-grade heat is promising for improving energy efficiency.This work proposes a CCP system that integrates a regenerative organic Rankine cycle(RORC)and an absorption chiller on both driving and cooling fluid sides.The system is modeled by using the heat current method to fully consider nonlinear heat transfer and heat-work conversion constraints and resolve its behavior accurately.The off-design system simulation is performed next,showing that the fluid inlet temperatures and flow rates of cooling water as well as RORC working fluid strongly affect system performance.The off-design operation even becomes infeasible when parameters deviate from nominal values largely due to limited heat transfer capability of components,highlighting the importance of considering heat transfer constraints via heat current method.Design optimization aiming to minimize the total thermal conductance is also conducted.RORC efficiency increases by 7.9%and decreases by 12.4%after optimization,with the hot fluid inlet temperature increase from 373.15 to 403.15 K and mass flow rate ranges from 10 to 30 kg/s,emphasizing the necessity of balancing system cost and performance.

Efficient realization of daytime radiative cooling with hollow zigzag SiO_(2) metamaterials

A tunable selective emitter with hollow zigzag SiO_(2) metamaterials, which are deposited on Si_(3) N_(4) and Ag film, is proposed and numerically investigated for achieving excellent radiative cooling effects. The average emissivity reaches a high value of 98.7% in the atmospheric window and possesses a high reflectivity of 92.0% in the solar spectrum. To reveal the enhanced absorptivity, the confined electric field distribution is investigated, and it can be well explained by moth eye effects. Moreover, tunable emissivity can also be initiated with different incident angles and it stays above 83% when the incident angle is less than 80°, embodying the excellent cooling performance in the atmospheric transparency window.Its net cooling power achieves 100.6 W·m^(-2), with a temperature drop of 13°, and the cooling behavior can persist in the presence of non-radiative heat exchange conditions. Therefore, high and tunable selective emitters based on our designed structure could provide a new route to realizing high-performance radiative cooling. This work is also of great significance for saving energy and environmental protection.

Research on Thermal Management Control Strategy of Electric Vehicle Liquid Cooling Battery Pack

Due to the risk of thermal runaway in the charging and discharging process of a soft packed lithium battery pack for electric vehicles,a stamping channel liquid cooling plate cooling system is designed,and then the heat dissipation problem of the battery pack is solved through reasonable thermal management control strategy.Using computational fluid dynamics simulation software star-CCM+,the thermal management control strategy is optimized through simulation technology,and the temperature field distribution of battery pack is obtained.Finally,an experimental platform is built,combined with experiments,the effectiveness of the thermal management control strategy of the cooling system is verified.The results show that when the battery pack is in the environment of 25℃,the maximum temperature of the cooling system can be lower than 40℃,the maximum temperature difference between all single batteries is within 5℃,and the maximum temperature difference between inlet and outlet coolant is 3℃,which can meet the heat dissipation requirements of the battery pack and prevent out of control heat generation.

Overall optimization of Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines considering the cooling power consumption

The Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines has been regarded as a promising tech- nique to reduce fuel consumption. Its heat dissipation in the condensation process, however, should be take：l away in time, which is an energy-consuming process. A fan-assisted auxiliary water-cooling system is employed in this paper. Results at 1300 r/min and 50% load indicate that the cooling pump and cooling fan together consume 7.66% of the recovered power. What＇s worse for the heavy load, cooling accessories may deplete of all the recovered power of the Rankine cycle system. Af- terwards, effects of the condensing pressure and water feeding temperature are investigated, based on which a cooling power consumption model is established. Finally, an overall efficiency optimization is conducted to balance the electric power gener- ation and cooling power consumption, taking condensing pressure, pressure ratio and exhaust bypass valve as major variables. The research suggests that the priority is to increase condensing pressure and open exhaust bypass valve appropriately at high speed and heavy load to reduce the cooling power consumption, while at low speed and light load, a lower condensing pressure is favored and the exhaust bypass valve should be closed making the waste heat recovered as much as possible. Within the sub-critical region, a larger pressure ratio yields higher overall efficiency improvement at medium-low speed and load. But the effects taper off at high speed and heavy load. For a given vehicular heavy-duty diesel engine, the overall e：＇ficiency can be improved by 3.37% at 1300 r/min and 25% load using a Rankine cycle system to recover exhaust energy. The improvement becomes smaller as engine speed and load become higher.

Effect of gallium doping on the magnetocaloric effect of LaFe_(11.2)Co_(0.7)Si_(1.1)

The lattice parameter and magnetocaloric properties of three samples of LaFe11.2Co0.7Si1.1-xGax with x = 0, 0.03 and 0.05 have been investigated by X-ray powder diffraction and magnetization measurements. The lattice parameter increases slightly and the Curie temperature increases somewhat with increasing gallium content. However, a small amount of Ga doping into the sample decreases the magnetic entropy change of the sample. All the samples remain in the first-order magnetic phase transition. The most striking effect of the Ga doping is that the cooling capacity in the samples increases significantly. The maximum magnetic entropy change, ASM and the cooling capacity of the sample LaFe11.2Co0.7Si1.07Ga0.03 are 11.9 J·kg^-1·K^-1 and 254.8 J·kg^-1, respectively.

Liquid Air Energy Storage for Decentralized Micro Energy Networks with Combined Cooling,Heating,Hot Water and Power Supply

Liquid air energy storage(LAES)has been regarded as a large-scale electrical storage technology.In this paper,we first investigate the performance of the current LAES(termed as a baseline LAES)over a far wider range of charging pressure(1 to 21 MPa).Our analyses show that the baseline LAES could achieve an electrical round trip efficiency(e RTE)above 60%at a high charging pressure of 19 MPa.The baseline LAES,however,produces a large amount of excess heat particularly at low charging pressures with the maximum occurred at~1 MPa.Hence,the performance of the baseline LAES,especially at low charging pressures,is underestimated by only considering electrical energy in all the previous research.The performance of the baseline LAES with excess heat is then evaluated which gives a high e RTE even at lower charging pressures;the local maximum of 62%is achieved at~4 MPa.As a result of the above,a hybrid LAES system is proposed to provide cooling,heating,hot water and power.To evaluate the performance of the hybrid LAES system,three performance indicators are considered:nominal-electrical round trip efficiency(ne RTE),primary energy savings and avoided carbon dioxide emissions.Our results show that the hybrid LAES can achieve a high ne RTE between 52%and 76%,with the maximum at~5 MPa.For a given size of hybrid LAES(1 MW×8 h),the primary energy savings and avoided carbon dioxide emissions are up to 12.1 MWh and 2.3 ton,respectively.These new findings suggest,for the first time,that small-scale LAES systems could be best operated at lower charging pressures and the technologies have a great potential for applications in local decentralized micro energy networks.

Energetic, economic, and environmental analysis of solid oxide fuel cell-based combined cooling, heating, and power system for cancer care hospital

In this study,energetic,economic,and environmental analysis of solid oxide fuel cell-based combined cooling,heating,and power(SOFC-CCHP)system is proposed for a cancer care hospital building.The energy required for the hospital power,cooling,and heating demands was obtained based on real and detailed field data,which could serve as a reference for future works in the field.These data with a 3D model for the hospital building are constructed and created in eQUEST software to precisely calculate the energy demands of the existing system(baseline case).Then,energetic,economic,and environmental models were developed to compare and assess the performance of the proposed SOFC-CCHP system.The results show that the proposed system can cover about 49% to 77% of the power demand of the hospital with an overall efficiency of 78.3%.Also,the results show that the levelized cost of electricity of the system and its payback period at the designed capacity of the SOFC is 0.087S/kWh and 10 years,respectively.Furthermore,compared to the baseline system of the hospital,the SOFC-CCHP reduces the CO_(2) emission by 89% over the year.The sensitivity analysis showed that a maximum SOFC efficiency of 52%and overall efficiency of 80%are achieved at cell operating temperature of 1027℃ and fuel utilization factor of 0.85.

WHR （Waste Heat Technology） Method in Tri-generation Model

This paper is focused on description of cool production in using WHR （Waste Heat Technology） Technology-a new method of centralized production of heat by using the waste heat from generated exhaust gas, which has been in 2009 developed and operated by companies HELORO s.r.o, and COMTHERM s.r.o.

Adiabatic Temperature Changes in (Gd_(1-x)Ho_x)_5Si_4 Magnetic Refrigeration Materials

A series of alloys (Gd1-xHox)5Si4(x=0, 0.05, 0.15, 0.25) have been prepared. Adiabatic temperature changes of(Gd1-xHox)5Si4 alloys is exactly investigated by a control and analysis system for ΔH=1.4 T, and the measurement results are trustworthy. Curie temperatures of these alloys are tunable in a wide temperature region, and decrease almost linearly with the increasing of Ho content. Magnetic entropy changes in the (Gd1-xHox)Si4 compounds are about 2.35 J/(kg·K) when magnetic field change are 0～1.4 T. The adiabatic temperatures of these alloys at Curie Points are larger than 1 K about 40% of that of Gd in a field change 0～1.4 T, and the curves of ΔTad are as wide as that of Gd. The relative cooling power RCP(S) or RCP(T) of these alloys are about 0.5～0.7 J·cm-3 and 42～50 K2 on the field 0～1.4 T, about 58% and 55% of that of Gd respectively. These alloys are potential magnetic refrigerants working in a refrigerator at room temperatures.

Time-efficient Strategic Power Dispatch for District Cooling Systems Considering Evolution of Cooling Load Uncertainties

District cooling system(DCS)provides centralized chilled water to multiple buildings for air conditioning with high energy-efficiency and operational flexibility.It is one of the most popular cooling systems for large buildings in modern cities and an important demand response source for power systems.In order to enhance its energy efficiency and utilize its flexibility,strategic operation is indispensable.However,finding an optimal policy for DCS operation is a challenging task because of the high inter-connectivity among components.The evolution of cooling load uncertainties further increases the difficulties.This paper addresses the aforementioned challenges by proposing a novel optimal power dispatch model for DCS.The proposed model optimizes water temperature and mass flow rates simultaneously to improve the energy efficiency as much as possible.It also explicitly describes the uncertainty accumulation and propagation.Chance-constrained programming is employed to guarantee the cooling service quality.We further propose a more timeefficient formulation to overcome the computational intractability caused by the non-smooth and non-convex constraints.Numerical experiments based on a real DCS confirm that a time-efficient formulation can save about half of solution time with negligible cost increase.

Enterprise 3500服务器指示灯状态分析与硬件故障定位

在地震数据处理、解释中心或野外地震数据采集质量监控当中,使用较广泛的设备是SUN公司服务器及工作站。Enterprise3500服务器是SUN公司生产的企业级服务器,其多用户多任务性能优于单一的SUN工作站,在地震数据处理和地震解释工作中发挥着重要作用。因此,对该系统的故障分析、定位与故障排除就显得尤为重要。

Development of a cryogen-free dilution refrigerator

With thermal fluctuation strongly suppressed,low temperature environment is essential for studies of condensed matter physics and developments of quantum technologies.Ultra-low temperature below 20 m K has demonstrated its importance and significance in physical sciences and information techniques.Dilution refrigeration is by far the best feasible and reliable method to generate and keep lattice temperature in this range.With a potential shortage of helium supply,cryogen-free dilution refrigerator(CFDR),eliminating the necessity of regular helium refill,becomes the main facility for the purpose of creating ultralow temperature environments.Here we describe our successful construction of a CFDR which reached a base temperature of around 10.9 m K for continuous circulation and 8.6 m K for single-shot operation.We describe its operating mechanism and the designs of key components,especially some unique designs including heat switch and alumina thermal link.Possible improvements in the future are also discussed.

A multi agent-based optimal control method for combined cooling and power systems with thermal energy storage

Combined cooling,heating and power(CCHP)systems have been considered as a potential energy saving technology for buildings due to their high energy efficiency and low carbon emission.Thermal energy storage(TES)can improve the energy efficiency of CCHP systems,since they reduce the mismatch between the energy supply and demand.However,it also increases the complexity of operation optimization of CCHP systems.In this study,a multi-agent system(MAS)-based optimal control method is proposed to minimize the operation cost of CCHP systems combined with TES.Four types of agents,i.e.,coordinator agents,building agents,energy management agents and optimization agents,are implemented in the MAS to cooperate with each other.The operation optimization problem is solved by the genetic algorithm.A simulated system is utilized to validate the performance of the proposed method.Results show that the operation cost reductions of 10.0%on a typical summer day and 7.7%on a typical spring day are achieved compared with a rule-based control method.A sensitivity analysis is further performed and results show that the optimal operation cost does not change obviously when the rated capacity of TES exceeds a threshold.

Operation Strategy Analysis and Configuration Optimization of Solar CCHP System

This paper proposed a new type of combined cooling heating and power(CCHP)system,including the parabolic trough solar thermal(PTST)power generation and gas turbine power generation.The thermal energy storage subsystem in the PTST unit provides both thermal energy and electrical energy.Based on the life cycle method,the configuration optimization under eight operation strategies is studied with the economy,energy,and environment indicators.The eight operation strategies include FEL,FEL-EC,FEL-TES,FEL-TES&EC,FTL,FTL-EC,FTL-TES,and FTL-TES&EC.The feasibility of each strategy is verified by taking a residential building cluster as an example.The indicators under the optimal configuration of each strategy are compared with that of the separate production(SP)system.The results showed that the PTST-CCHP system improves the environment and energy performance by changing the ratio of thermal energy and electric energy.The environment and energy indicators of FEL-TES&EC are superior to those of FTL-TES&EC in summer,and the results are just the opposite in winter.The initial annual investment of the PTST-CCHP system is higher than that of the SP system,but its economic performance is better than that of the SP system with the increase of life-cycle.

Dynamic Simulation and Performance Analysis on Multi-Energy Coupled CCHP System

Although the Combined Cooing,Heating and Power System(hereinafter referred to as“CCHP”)improves the capacity utilization rate and energy utilization efficiency,single use of CCHP system cannot realize dynamic matching between supply and demand loads due to the unbalance features of the user’s cooling and heating loads.On the basis of user convenience and wide applicability of clean air energy,this paper tries to put forward a coupled CCHP system with combustion gas turbine and ASHP ordered power by heat,analyze trends of such parameters as gas consumption and power consumption of heat pump in line with adjustment of heating load proportion of combustion gas turbine,and optimize the system ratio in the method of annual costs and energy environmental benefit assessment.Based on the analysis of the hourly simulation and matching characteristics of the cold and hot load of the 100 thousand square meter building,it is found that the annual cost of the air source heat pump is low,but the energy and environmental benefits are poor.It will lead to 6.35%shortage of cooling load in summer.Combined with the evaluation method of primary energy consumption and zero carbon dioxide emission,the coupling system of CHHP and air source heat pump with 41%gas turbine load ratio is the best configuration.This system structure and optimization method can provide some reference for the development of CCHP coupling system.

Radiative cooling and cold storage for concentrated solar power plants

Concentrated solar power(CSP)plants are generally located in solar-abundant yet hot and water-stressed loca-tions.In such circumstances,efficient but water-intensive once-through wet cooling and water-free but inefficient air cooling are both unfavorable.Considering both thermal efficiency and water availability/temperature,recir-culating evaporative cooling is a better alternative.However,evaporative cooling still loses large amounts of water into the atmosphere and thus requires a nonstop water supply.Therefore,simultaneously reducing water loss and maintaining thermal efficiency requires efficient means of supplemental cooling for CSP plants.Follow-ing our previous work on scalable radiative cooling films and a kW-scale radiative cooling system,we explore the potential of consumptive water use reduction in recirculating wet-cooled CSP plants by integrating supplemental radiative cooling and cold storage.Through modeling of a reference CSP plant with a supplemental radiative cooling system as large as the plant solar field,the results show that 40%-60%of the annual consumptive water use can be potentially reduced in the hot southwestern U.S.region with daytime-only radiative cooling,whereas the annual potential water saving can be as much as 65%-85%if the radiative cooling system works both day and night with cold storage.

Operation Strategy and Matching of Supply and Demand of CCHP System with Various Building Types

The important indications for assessing CCHP(combined cooling,heating and power)systems are their supply-demand matching characteristics between the user demand side and the energy supply side.These characteristics are primarily influenced by different building types and operating strategies.In view of the energy redundancy of the following electric load(FEL)and following thermal load(FTL)operation strategies and the energy deficiency of the following hybrid electric-heating load(FHL)operation strategy,this paper proposes an improved following balanced heat-electrical load(IFBL)operation strategy based on the following balanced heat-electrical load(FBL)operation strategy.Based on the energy utilization rate as the objective function,this paper optimizes the installed capacity of CCHP systems in different buildings and proposes an energy factor for evaluating the supply-demand matching characteristics of the system.The results show that the energy utilization rate and energy factor of the system under IFBL are optimal relative to the other operation strategies.Secondly,the hotel building has the highest energy utilization rate and the lowest energy factor;on the contrary,the office building has the lowest energy utilization rate and the highest energy factor.Finally,the analysis of supply-demand matching for different building types under multiple operating strategies shows that the hospital and hotel systems exhibit optimal supply-demand matching performance under the IFBL strategy,with values of 0.945 and 0.938,respectively;on the contrary,the office system has an optimal supply-demand matching of 0.935 under the FEL strategy.Under the FTL strategy,the systems of all three buildings exhibit poor matching performance.

Tunable nano Peltier cooling device from geometric effects using a single graphene nanoribbon

Based on the phenomenon of curvature-induced doping in graphene we propose a class of Peltier cooling devices, produced by geometrical effects, without gating. We show how a graphene nanorib- bon laid on an array of curved nano cylinders can be used to create a targeted and tunable cooling device. Using two different approaches, the Nonequilibrium Green＇s Function （NEGF） method and experimental inputs, we predict that the cooling kW/cm2, on par with the best known techniques power of such a device can approach the order of using standard superlattice structures. The structure proposed here helps pave the way toward designing graphene electronics which use geometry rather than gating to control devices.