多尺度有序结构碲化铋在微型热电器件中的应用

Thermoelectric devices allow direct conversion between electricity and heat,which include thermoelectric generators(TEGs)and thermoelectric coolers(TECs)based on the Seebeck and Peltier effects,respectively[1].Despite suffering from low energy conversion efficiency,thermoelectric devices have played an irreplaceable role in space exploration and solid-state cooling due to their advantages of compactness,fast response,and absence of moving parts and refrigerant.In particular,near-room temperature(250–400 K)TECs play a key role in the precise temperature control of lidar.

炎热气候下基于光谱管理和辐射制冷的温室薄膜材料

炎热气候下,温室内部热量过度累积、气温过高的问题经常发生,严重影响温室内作物的生长发育,大大降低了温室的周年利用率和经济效益.为此,有效调节温室内气温已经成为炎热地区温室栽培需要解决的首要问题.基于光谱管理和辐射制冷原理,本文提出两种不同属性薄膜分别作为温室覆盖材料和地膜,在不牺牲植物光合作用的前提下,减少温室内部热积累,从而延长温室可用生产周期.作为覆盖材料的透明辐射制冷薄膜(T-RC)具有大气窗口波段高发射率,光合有效辐射波段高透过率和近红外辐射波段高反射率,在田间试验中可较PO薄膜温室降温18.6℃,并使樱桃萝卜产量提高62.7%.作为地膜的高反射辐射制冷薄膜(RC)在大气窗口波段具有高发射率,同时在太阳光谱波段保持高反射率.覆盖RC薄膜后,地温可较空白土壤降低12.5℃,并使杭白菜产量增加127.35%.这两种薄膜为炎热气候条件下的温室增产提供了一种被动式、零能耗的新路径.

Origins of three-dimensional charge and two-dimensional phonon transports in Pnma phase PbSnSe_(2)thermoelectric crystal

Recently,PbSnSe_(2)alloy was found to exhibit a large hysteresis effect on transport properties,demonstrating its significant potential for thermoelectric applications.Using ab initio approaches,we studied the carrier transport properties of PbSnSe_(2)crystal,which is a special case of the alloy with the shortest-range order.A peak power factor of 134.2μW cm^(-1)K^(-2)was found along the crossplane direction in the n-type PbSnSe_(2)at a doping concentration of 7×10^(20)cm^(-3)at 700 K.This high power factor originates from delocalized p electrons between intra-plane Pb-Se pairs and between cross-plane Sn-Se pairs that can build up transport channels for conducting electrons,leading to a high electrical conductivity of 5.9×10^(5)S m^(-1).Introducing Pb atoms into Pnma phase SnSe can decrease the phonon group velocities and enhance the phonon-phonon scatterings,leading to a low thermal conductivity of 0.53 W m^(-1)K^(-1)at 700 K along the cross-plane direction.The calculated peak ZT of~3 along the cross-plane direction at an n-type doping concentration of around 5×10^(19)cm^(-3),which represents a theoretical upper limit for an idealized PbSnSe_(2)crystal.This work interprets the origins of three-dimensional charge and two-dimensional phonon transport behavior in PbSnSe_(2)and demonstrates that such crystals are promising high-performance thermoelectric semiconductors.

Simultaneous enhancement in electrical conductivity and Seebeck coefficient by single-to double-valley transition in a Dirac-like band

SnTe possesses a single-to double-valley transition in the conduction band minimum when a compressive strain is applied.Through a tight-binding analysis,it is shown that the variation of the band structure is attributed to the strain-induced delocalization of both the Sn-5s orbitals and Te-5p orbitals with different angular momenta.This effect can largely increase the electron density of states near the band edge and thus keep the Fermi level of the compressed SnTe closer to it,where the electrons have lower scattering rates.The strain-induced double valleys lead to simultaneous increases in the electrical conductivity and the Seebeck coefficient and thereby nearly four times the enhancement of the power factor at the doping concentration of 5×10^(19) cm^(–3).This work suggests a feasible concept that can be employed to promote the power factor of a Dirac semiconductor via manipulating the valley degeneracy in the conduction band minimum.

Energy saving analysis of a transparent radiative cooling film for buildings with roof glazing

A transparent radiative cooling(T-RC)film with low transmittance in solar spectra and selectively high emissivity in the atmospheric window(8-13𝜇m)is applied on roof glazing for building energy saving.To evaluate the per-formance of the T-RC film,two identical model boxes(1.0 m×0.6 m×1.2 m,L×W×H)were constructed and the inside air temperatures were measured in August in Ningbo,China.Results show that the maximum temperature difference between the two model boxes with and without the T-RC film was 21.6℃during the experiment.A whole building model was built in EnergyPlus for the model box.With a good agreement achieved between the calculation results and the measured temperature data,the experimentally validated EnergyPlus model was then extended to an 815.1 m^(2)exhibition building with roof glazing to analyze the annual air conditioning(AC)energy consumption.The results show that by incorporating both the T-RC film’s cooling benefit in summer and heating penalty in winter,the annual AC energy consumption of the exhibition building can be reduced by 40.9-63.4%,varying with different climate conditions.

A general White–Box strategy for designing thermoelectric cooling system

Thermoelectric cooling(TEC)is critically important in thermal management of laser modules or chips and potentially for personalized thermoregulation.The formulae for efficiency in standard textbooks can only describe the performance of a TEC module with ideal thermal conditions,that is,fixed terminal temperatures,but are unable to deal with a real TEC system where heat transfer at its interfaces with the heat source and sink are finite and with thermal resistances.Here,we define the TEC system-level performance indices,that is,the maximum cooling power,temperature difference,and coefficient of performance,by introducing a set of explicit formulae.The external heat transfer conditions are taken into account as dimensionless thermal resistance parameters.With these formulae,the TEC system performances are evaluated elegantly with errors well within±5%over broad operating conditions.We further optimize the cooling power and the coefficient of performance in practical scenarios and establish a general White–Box design procedure for TEC systems,which enables a transparent design process and straightforward analysis of performance bottlenecks.A set of cooling experiments are performed to validate the analytical model and to illustrate the dependence of system design on realistic thermal conditions.By choosing the suitable TEC module parameter under given external heat transfer conditions,the cooling power can be improved by more than 100%.This work sheds some light on the integral design of TEC systems for broad applications to take full advantage of the advanced thermoelectric materials in the cooling field.

High‑temperature thermal storage‑based cement manufacturing for decarbonization

Cost-effective CO_(2) capture is essential for decarbonized cement production since it is one of the largest CO_(2) emission sources,where 60%of direct emissions are from CaCO3 decomposition and 40%are from fuel combustion.This work presents a low-carbon cement manufacturing process by integrating it with renewable energy for electric heating and thermal storage to replace the burning of fossil fuels in the conventional calciner.The low-carbon renewable energy reduces the indirect CO_(2) emissions from electricity consumption.The high-temperature CO_(2) is employed as the heat transfer fluid between the energy storage system and the calciner.In the proposed basic manufacturing process,the CO_(2) from the CaCO3 decomposition can be directly collected without energy-consuming separation since no impurities are introduced.Furthermore,the remaining CO_(2) from fuel combustion in the kiln can be captured through monoethanolamine(MEA)absorption using waste heat.In the two situations,the overall CO_(2) emissions can be reduced by 69.7% and 83.1%,respectively,including the indirect emissions of electricity consumption.The economic performance of different energy storage materials is investigated for materials selection.The proposed manufacturing process with a few high-temperature energy storage materials(BaCO_(3)/BaO,SrCO_(3)/SrO,Si,etc.)offers a higher CO_(2) emission reduction and lower cost than alternative carbon capture routes,i.e.,oxyfuel.The cost of CO_(2) avoided as low as 39.27$/t can be achieved by thermochemical energy storage with BaCO_(3)/BaO at 1300℃,which is superior to all alternative technologies evaluated in recent studies.

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.