考虑热能动态平衡的含氢储能的综合能源系统热电优化

在综合能源系统中,电力系统和热力系统通过热电联产机组、电锅炉等装置耦合,对系统内电能和热能进行协调管理,可提高系统的运行灵活性,为系统消纳可再生能源提供新途径。为此,提出了一种考虑热能动态平衡的含氢储能的综合能源系统热电优化模型。首先,建立氢能系统模型,对系统内电解槽、氢燃料电池等设备进行精细化建模,挖掘氢能的利用潜力,提高了系统的运行经济性。然后,基于用户对室温要求的模糊性,引入热功率松弛项使热能保持动态平衡,提高了系统设备出力的灵活性。最后,以综合能源系统运行成本最低为目标函数,以能量平衡、网络安全为约束条件,建立综合能源系统热电优化模型。仿真结果表明,所提模型可在满足用户用能需要的同时降低系统的运行成本,提高风电消纳水平。

考虑碳捕集技术的虚拟电厂热电联合优化

碳捕集技术作为电力系统低碳转型的关键技术,应用到热电联合系统可降低虚拟电厂的碳排放。为此,提出将碳捕集技术应用至虚拟电厂热电联合优化的技术路线,以促使其低碳经济运行。一方面,依托阶梯碳交易机制、需求响应和电-热之间的互转,以减少虚拟电厂热电联合运行的碳排放;另一方面,以虚拟电厂运行成本最小为目标,综合考虑负荷调节潜力、新能源出力上限等虚拟电厂内部约束,以及电-热-碳互转的物理约束,以提高虚拟电厂运行经济性。基于某园区实况运行数据,围绕是否配置碳捕集技术和需求响应来设计对照场景,验证了所提虚拟电厂热电联合优化模型具有一定的现实可用性和鲁棒性。

基于虚拟电厂“热电解耦”的负荷优化调度及经济效益分析

我国北方冬季供暖期,大量热电联产机组工作在"以热定电"运行模式下,造成了系统调峰能力不足,弃风形势严峻。能有效减少弃风的风电供热由于经济效益问题和调度平台尚未完善,难以大规模推广应用。针对上述问题,该文将一定供热区域内的热电厂、风电场、光伏电站组成虚拟电厂,形成利益整体,并加入风电供热设备实现热电联产机组的"热电解耦"。首先描述了虚拟电厂的组成结构和运行方式,其次建立了虚拟电厂热电负荷优化调度模型,对比了不同的虚拟电厂运行策略,并采用自适应免疫遗传算法进行求解,实现了虚拟电厂内部热电负荷优化调度。通过算例分析,验证所建立模型的合理性与有效性;表明在虚拟电厂中加入风电供热设备的运行策略可以有效地减少出力偏差与环保代价,提高经济效益;风电供热容量在一定范围内越高或风光预测精度越高,虚拟电厂经济效益越好,同时体现了虚拟电厂作为一个利益整体的经济性优势。

区域热电厂负荷优化分配的研究

根据热负荷,通过区域内电负荷的优化分配,可以降低一次能源的耗量。建立了供热机组变工况模型,并进行了模型验证,满足工程要求。以标准煤耗量最小为目标函数,采用穷举法将区域内总电负荷分配给不同热电厂,再以粒子群优化算法在热电厂内进行厂级热电负荷优化分配。以区域内3座热电厂为例,根据热负荷,对该区域内的电负荷进行了优化分配。以区域内3种负荷分配方案为例,结果表明:平均每台机组减少标准煤耗率约为0.58g/(k W·h)、0.46g/(k W·h)、0.67g/(k W·h)。因此,该方法可降低煤耗量,对区域内供热机组节能降耗具有一定的参考价值。

供热电厂热电负荷优化分配系统的研制

针对供热电厂热电负荷优化分配中存在的问题,研制开发了热电负荷优化分配系统,具有明显的节能效益和经济效益,为同类机组的节能工作提供了经验。

供热汽轮机组热电负荷优化分配系统的开发与应用

针对热电厂热电负荷调度中存在的不经济因素 ,在分析传统热电负荷分配计算方法缺陷的基础上 ,提出了“逐点法”分配的数学模型 ,以此研制开发了热电负荷优化分配系统。阐述了系统的结构和主要功能 ,并对取得的经济效益进行了测算 ,为供热电厂的经济调度提供了经验。

高性能新型Mg_(3)(Sb,Bi)_(2)基热电材料的发展现状

热电材料能够实现热能与电能的相互转换,是一种可以应用于余热回收及半导体制冷等相关领域的功能性材料。传统热电材料的发展目前已趋于成熟,但仍然面临着高昂的原料成本及较低的热电转换效率等问题。Mg_(3)(Sb,Bi)_(2)基热电材料自被发现以来就以其低成本的元素组成和作为Zintl相具备的本征低热导率受到广泛关注。其中n型传导样品由于高能带简并度的优势更是有着较高的塞贝克系数,相较于传统中低温热电材料具备更大的发展潜力。然而,较大的带隙使得Mg_(3)(Sb,Bi)_(2)基热电材料载流子浓度整体偏低,同时还存在着由Mg空位引起的热稳定性较差的问题。为此,在保证该材料低热导率的同时,研究者们尝试了不同的制备工艺,并通过组分优化和结构优化来不断改善其电输运性能及热稳定性。目前Mg_(3)(Sb,Bi)_(2)基热电材料的最大ZT值已经达到1.8以上,同时其器件化后的热电转换效率也可媲美于传统Bi_(2)Te_(3)基热电器件。本文总结了Mg_(3)(Sb,Bi)_(2)基热电材料的基础物理性能与制备方法,从不同的优化手段出发依次介绍了现阶段该材料的研究成果,并展望了其在未来可行的发展方向。

燃机电厂9F型机组热电负荷优化分配研究

电厂热电负荷优化分配是指在全厂总调度负荷下,根据各机组的热力性能确定各机组应承担的热电负荷,使得全厂效益最大或能耗最小的一种最优化问题.不同于燃煤热电厂,燃机电厂9F型机组由于设计为燃气轮机加蒸汽轮机的组合方式运行,因此在联合循环热力性能模型建立上较为复杂.提出了将余热锅炉新蒸汽参数作为中间变量,建立了机组天然气燃料消耗与电负荷、热负荷之间的关系模型,确定了优化计算的目标函数和边界约束条件,并采用非线性规划方法求解.模拟与实际运行结果均表明,该优化分配方法能有效降低燃机电厂燃料消耗水平,可以为同类型燃机电厂热电负荷优化分配提供参考.

联合网电时母管制供热机组热电负荷优化分配策略研究

母管制供热机组为了满足热电的供应常多发电、造成发电过剩的情况,由于热电厂发电仅适用于园区热电负荷,无法发电上网产生收益,不但造成了能源的浪费,而且使运行成本增加。首先,以母管制热电厂运行成本为优化目标,建立了联合网电时母管制系统汽机侧混合类型供热机组负荷优化模型;然后,提出了基于小微增原则,对2种不同情形下混合类型机组的热电负荷优化分配策略进行研究;最后,以某热电厂的热电负荷为例进行优化分配。结果表明,对热电负荷优化后的运行成本低于未优化的运行成本,同时也验证了本文所提基于联合网电时母管制供热机组热电负荷优化分配策略的有效性。

基于电-热分时间尺度平衡的综合能源系统日前经济调度

综合能源系统能够提高能源利用效率、促进可再生能源消纳,已成为能源领域的重点研究方向。如何实现多能源的联合规划、协同运行是综合能源系统运行的重要问题。在热电联供型综合能源系统中,电能可实现实时调度;而热能具有热惯性,其供需可能不满足实时平衡,可依据某一调度时段内的总量平衡进行调度。基于此,提出了考虑电-热分时间尺度平衡的综合能源系统优化模型,寻求最优热调度时间尺度以满足用户舒适度及系统运行经济性双重要求。所提模型中电能为实时平衡,热能为调度时间尺度内的总量平衡,通过电-热分时间尺度平衡提高了机组运行的灵活性。用户舒适度采用国际ISO标准热舒适模型,可更加人性化地反映供热效果。以某省某区域冬季典型日为例进行仿真分析,结果表明所提模型能够得到最优的热调度平衡时间尺度与调度计划,在满足用户舒适度的同时提高了系统的运行经济性。

Optimized Operation of a Solar-Driven Thermoelectric Dehumidification System for Fresh Water Production

The work presents a parametric analysis of the performance of a solar-driven thermoelectric system to dehumidify air and produce fresh water. The system is combined with a solar distiller humidifying ambient air to enhance distillate output to meet the specified fresh water needs for a residential application. The presented system is a totally renewable energy-based system taking advantage of the clean solar energy. A model is developed to simulate the air dehumidification process using TEC （thermoelectrically cooled） channels. An optimization problem for setting system operational parameters is formulated to meet the fresh water requirement of 10 liters per day for a typical residential application in the Lebanese coastal humid climate. Using five TEC channels of length of 1.2 m and area of 0.07 - 0.05 m^2 integrated with 1.2 m^2 solar distiller is capable of meeting the water demand, where the air mass flow rate introduced to each TEC channel is optimally set at 0.0155 kg/s. The optimal electrical current input to the TEC modules from the photovoltaic solar panels varied depending on the month and is set at 2.2 A in June, 2.1 A in July and 2.0 A in August, September and October per each TEC module.

Optimal Analysis of Pure Low-Temperature Waste Heat Recovery Generation System

In this paper, a detailed thermodynamic analysis of the pure low-temperature waste heat recovery generation system is presented. The parameters affecting the system performance are compared to obtain the most significant ones; furthermore, parameter values are optimized for the largest power generating capability of the system. It is found that the most important parameters are inlet flue gas temperature, steam pressure and the pinch point temperature difference. There is an optimal superheated steam pressure value for giving the maximum generation power per unit flue gas. With the increase of inlet flue gas temperature, the generating power increases and the optimized steam pressure rises as well. However, with increase in pinch point temperature difference, the generating power decreases and the optimized steam pressure decreases as well. The theoretical calculation provides a theoretical basis for the parameters optimization in the design of the pure low-temperature waste heat recovery eeneration swtem

Optimization of Heat Spreader Design for Electronic Cooling

The continuing increase in IC （Integrated Circuit） power levels and microelectronics packaging densities has resulted in the need for detailed considerations of the heat sink design for integrated circuits. One of the major components in the heat sink is the heat spreader which must be designed to effectively conduct the heat dissipated from the chip to a system of fins or extended surfaces for convective heat transfer to a flow of coolant. The heat spreader design must provide the capability to dissipate the thermal energy generated by the chip. However, the design of the heat spreader is also dependent on the convection characteristics of the fins within the heat sink, as well the material and geometry of the heat spreader. This paper focuses on the optimization of heat spreaders in a heat sink for safe and efficient performance of electronic circuits. The results of the study show that, for air-cooled electronics, the convective effects may dominate the thermal transport performance of the heat spreader in the heat sink.

块体热电材料的研究进展

文章重点介绍了现役热电材料(Bi2Te3,PbTe,SiGe)、常见结构类型(方钴矿型,笼合物型,Half-Heusler合金型,钠钴氧型和Zn4Sb3型)热电材料及新颖晶体结构类型的热电材料的晶体结构、热电性能、热电性能优化等方面的最新研究进展.

Thermodynamic analyses and optimization for thermoelectric devices:The state of the arts

Thermoelectric effect is the most efficient way to convert electric energy directly from the temperature gradient. Thermoelectric effect-based power generation, cooling and heating devices are solid-stated, environmentally friendly, reliable, long-lived, easily maintainable, and easy to achieve miniaturization and integration. So they have unparalleled advantages in the aerospace, vehicle industry, waste heat recovery, electronic cooling, etc. This paper reviews the progress in thermodynamic analyses and optimizations for single- and multiple-element, single- and multiple-stage, and combined thermoelectric generators, thermoelectric refrigerators and thermoelectric heat pumps, especially in the aspects of non-equilibrium thermodynamics and finite time thermodynamics. It also discusses the developing trends of thermoelectric devices, such as the heat sources of thermoelectric generators, multi-stage thermoelectric devices, combined thermoelectric devices, and heat transfer enhancement of thermoelectric devices.

Entransy dissipation/loss-based optimization of two-stage organic Rankine cycle(TSORC)with R245fa for geothermal power generation

Based on organic Rankine cycle(ORC), the two-stage evaporation strategy is adopted to replace the single-stage evaporation to improve the system performance. In order to evaluate the temperature matching of the two-stage evaporation, a theoretical optimization model was established to optimize the two stage organic Rankine cycle(TSORC) based on the entransy theory and thermodynamics, with the ratio of the entransy dissipation rate of the TSORC to that of the ORC as the objective function. This paper aims to illuminate the improving degree of the system performance of the TSORC. The results show that the TSORC enhances the average evaporating temperature, thereby reducing the entransy dissipation rate in the evaporator and the total entransy dissipation rate. The maximal net power output is proportional to the entransy loss rate and inversely proportional to the entransy dissipation rate. However, compared with the ORC, the TSORC can output more power but requires a higher total thermal conductance. Moreover, there exists an optimal intermediate geothermal water temperature(IGWT) to maximize the net power output of the TSORC. The TSORC can be considered in engineering applications.

Performance Improvement of Combined Cycle Power Plant Based on the Optimization of the Bottom Cycle and Heat Recuperation

Many F class gas turbine combined cycle （GTCC） power plants are built in China at present because of less emission and high efficiency. It is of great interest to investigate the efficiency improvement of GTCC plant. A combined cycle with three-pressure reheat heat recovery steam generator （HRSG） is selected for study in this paper. In order to maximize the GTCC efficiency, the optimization of the HRSG operating parameters is performed. The operating parameters are determined by means of a thermodynamic analysis, i.e. the minimization of exergy losses. The influence of HRSG inlet gas temperature on the steam bottoming cycle efficiency is discussed. The result shows that increasing the HRSG inlet temperature has less improvement to steam cycle efficiency when it is over 590℃. Partial gas to gas recuperation in the topping cycle is studied. Joining HRSG optimization with the use of gas to gas heat recuperation, the combined plant efficiency can rise up to 59.05% at base load. In addition, the part load performance of the GTCC power plant gets much better. The efficiency is increased by 2.11% at 75% load and by 4.17% at 50% load.

Optical analysis of a hybrid solar concentrating Photovoltaic /Thermal (CPV/T) system with beam splitting technique

A novel hybrid solar concentrating Photovoltaic/Thermal (CPV/T) system with beam splitting technique is presented. In this system, a beam splitter is used to separate the concentrated solar radiation into two parts: one for the PV power generation and the other for thermal utility. The solar concentrator is a flat Fresnel-type concentrator with glass mirror reflectors. It can concentrate solar radiation onto solar cells with high uniformity, which is beneficial to improving the efficiency of solar cells. The thermal receiver is separated to the solar cells, and therefore, the thermal fluid can be heated to a relatively high temperature and does not affect the performance of solar cells. A dimensionless model was developed for the performance analysis of the concentrating system. The effects of the main parameters on the performance of the concentrator were analyzed. The beam splitter with coating materials Nb2O3 /SiO2 was designed by using the needle optimization technique, which can reflect about 71% of the undesired radiation for silicon cell(1.1m < 3m) to the thermal receiver for thermal utility. The performance of this CPV/T system was also theoretically analyzed.

Optimization of the thermoelectric properties of poly(nickel-ethylenetetrathiolate) synthesized via potentiostatic deposition

The coordination polymer poly（nickel-ethylenetetrathiolate） （poly（Ni-ett））, formed by nickel（Ⅱ） and 1,1,2,2-ethenetetrathiolate （ett）, is the most promising N-type organic thermoelectric material ever reported; it is synthesized via potentiostatic deposition, and the effect of different applied potentials on the optimal performance of the polymers is investigated. The optimal thermoelectric property ofpoly（Ni-ett） synthesized at 0.6 V is remarkably greater than that of the polymers synthesized at 1 and 1.6 V, exhibiting a maximum power factor of up to 131.6μW/mK2 at 360 K. Furthermore, the structure-property correlation ofpoly（Ni-ett） is also extensively investigated. X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analyses revealed that the larger size of crystalline domains and the higher oxidation state of poly（Ni-ett） synthesized at 0.6 V possibly results in the higher bulk mobility and carrier concentration in the polymer chains, respectively, accounting for the enhanced power factor.

Excellent thermoelectric performance of boron-doped n-type Mg_(3)Sb_(2)-based materials via the manipulation of grain boundary scattering and control of Mg content

Thermoelectric devices require thermoelectric materials with high figure-of-merit(ZT)values in the operating temperature range.In recent years,the Zintl phase compound,n-Mg_(3)Sb_(2),has received much attention owing to its rich chemistry and structural complexity.However,it hardly achieves high ZT values throughout the medium temperature range.Herein,by increasing the sintering temperature as much as possible,we successfully increased the average grain size of the compound by 15 times,and the grain boundary scattering was manipulated to obtain high carrier mobility of up to 180 cm^(2)V^(-1)s^(-1).Simultaneously,we optimized the Mg content for ultralow lattice thermal conductivity.We first doped the Mg_(3)Sb_(2)-based materials with boron for higher sintering temperature,good thermal stability,and higher hardness.The synergistic optimization of electrical and thermal transport resulted in excellent ZT values(0.62 at 300 K,1.81 at 773 K)and an average ZT of 1.4(from300 to 773 K),which are higher than the state-of-the-art values for n-type thermoelectric materials,demonstrating a high potential in device applications.