多类型热电机组群实时负荷动态分配方法

在运行灵活性提升背景下,考虑热电厂内不同类型热电机组的可行运行区间及其相关辅机运行动态安全边界,以实现热电厂整体效益最大为目标,提出一种多类型热电机组群实时负荷动态分配方法。该方法计及热电厂的售电收益、运行成本、辅助调峰市场收益、负荷跟踪惩罚,并通过设置机组出力最小调整量降低各机组出力调整频次。基于东北地区某热电厂实际数据的算例结果验证了所提方法的有效性和优越性。     

以总能系统观点与用热终端高效化为特征的大中型火电机组联产供热系统新模式

以总能系统观点为指导,本文把联产供热系统视为由六个子系统组成,提出了各子系统火用效率的计算方法和这些效率对供热煤耗和成本的影响,并在此基础上提出了能适用于大中型火电机组的热电联产供热系统的新模式。新模式以用热终端高效化为特征,带动提高一系列子系统的火用效率,并把行之有效的,但一般是小规模孤立使用的现代化节能技术与节能设备,大规模地有机地与热电联产系统融为一体,扩大热网水的降温幅度,对热网水低品位能量进行梯级利用,形成采暖节能与增供电力相互促进相得益彰的机制,使联产供热的煤耗和供热成本大幅度地降低。文中结合世界技术现状和我国经济发展阶段分析了新模式的现实可行性。     

Life cycle assessment of domestic fuel cell micro combined heat and power generation: Exploring influential factors

Residential Fuel Cell micro combined heat and power (FC-μCHP) systems can help decarburizing the energy system. In the European ene.field project, the environmental performance of FC-μCHP under different conditions was therefore evaluated by means of a comprehensive Life Cycle Assessment (LCA). Important influential factors were explored, i.e. heating demands, full load hours (FLHs) and electricity replacement mixes (ERMs). The systems were compared with a stand-alone Gas Condensing Boiler (GCB) and a heat pump (HP, only in single family homes, SFHs). For the initially assumed FLHs and the current ENTSO-E ERM, relevant environmental impacts including climate change are generally smaller for the FC-μCHPs than for the HP and the stand-alone GCB. In the setting “existing SFHs in central climate” with the highest deployment potential, GHG emission savings are higher the more carbon-intensive the ERM is and/or higher the net electricity export into the grid is. The results are discussed and put into perspective. Further research demands as well as product development opportunities are outlined. The importance of a green hydrogen economy is emphasized.     

The effect of alkali treatment on rice husk moisture content and drying kinetics

The utilization of rice husks for energy production is often problematic due to their high ash content. A simple method for silica ash removal is the treatment of the husks with sodium hydroxide solutions. The alkali treatment can induce other changes to the husks which need to be investigated. Here, the effects of alkali treatment on the moisture content and drying kinetics of the samples were investigated. The alkali treatment is shown to result in an increase in moisture retention by the as-prepared biomass. Response surface methodology (RSM) using a Box–Behnken design (BBD) is employed to investigate the effects of various input parameters, namely reaction temperature, duration, and alkali mass ratio on moisture uptake of the rice husk. In addition, the drying kinetics of the as-prepared samples are modeled and compared to raw husk prior to treatment. The results show a small increase in the effective diffusivity and a significant decrease in the activation energy required for drying the treated samples.     

Optimal control of combined heat and power units under varying thermal loads

This paper describes a model based optimizer that allows a combined heat and power (CHP) unit to supply backup power to a Smart Grid on the one hand and minimize the cost for heat and power supply on the other hand. The model of the CHP unit is lean but nevertheless accurately represents the unit behavior, including thermal behavior of the storage as well as the aging effect of engine starts. Thanks to the small model dimension we can solve the optimal dispatch problem efficiently using dynamic programming. Two selected soft- and hard-ware in the loop tests are discussed to demonstrate the performance of the approach. A re-optimization strategy is discussed that allows reactions to wrong predictions of external influences like weather.     

Design and analysis of hybrid energy systems: The Brazilian Antarctic Station case

This paper presents the design and analysis of a hybrid energy system for an Antarctic Station. The research considered the constraints of the extreme climate, the logistics limitations and the technical assets of the Brazilian Antarctic Station. The thermal and electrical annual profiles of the Station, the spreadsheets of the organic solid waste, and the local measured data of wind and sun were investigated. The application of anaerobic digestion, combined heat and power generation, use of photovoltaic panels and wind turbines were analysed. In the renewables analyses, 25 years of local climatic data were assessed. The influences of air density, temperature and ground reflectance on the renewable generation were also investigated. In order to assess potentials hybrid energy systems for the Brazilian Antarctic Station, possible topologies were organized in groups and then analysed by consumption, performance and feasibility. The methodology supported the identification of an efficient and feasible energy system for the Brazilian Station. The proposed system reached 37% of fuel saves considering the original demand profile of the Station. This work adopted the liter of oil as a currency, thus in any future time the results can be used for financial studies.     

The introduction and expansion of biomass use in Swedish district heating systems

District heating satisfies about 60% of the heat demand in Swedish buildings. Today, more than two thirds of the heat supply to the district heating systems is based on biomass and waste, and biomass alone accounts for about half of the heat supply. The purpose of this paper is to present the Swedish experiences of introducing and expanding the use of biomass in the district heating systems and to identify the main drivers behind this development. Our five research questions and the corresponding conclusions consider the driving forces from energy policy tools and local initiatives, the biomass prices, the established infrastructures in forestry and district heating, the technology paths for biomass conversion, and finally the future challenge of competing uses of biomass.     

Estimating the value of energy saving in industry by different cost allocation methods

In complicated systems, such as a highly integrated industrial plant with its own energy production, estimating the value of energy conservation is not so straightforward. Often, heat is priced using different kinds of methods for allocating the fuel cost to heat and electricity. However, there is no consistent way to valuate the process steam in industry, and not just one useful method for allocating costs to heat and power. In this paper, the energy method, exergy method, benefit distribution method and market‐based method are evaluated and compared from different decision‐making perspectives. The results of this study indicate that the allocation methods may overestimate by up to 200–300% the benefits from the mill perspective compared to the benefits from the mill site perspective. So, the most suitable method may vary, depending on the selected system boundary, i.e. the decision‐making perspective, the type of CHP plant and energy prices. Based on the results of this study, the exergy method fits well with the CCGT plant with a condensing unit and constant fuel input. On the other hand, the market‐based method is the most correct way to estimate the value of heat when heat conservation reduces the production of CHP electricity. Copyright © 2010 John Wiley & Sons, Ltd.     

New design of CHP for hypermarket of higher energy efficiency,less-fugitive refrigerant emissions and a remarkable reduction in initial and operating cost

High initial cost of power plant, limited power capacity of the existing plant and the frequent black out of many districts due to the continuous increase in electrical demands, in addition to the adverse effect of the blackout on hypermarkets, especially on foodstuff such as meat, chicken, etc. strongly encourage the adoption of a regenerating process and the principle of combined heat and power. This work investigates the upgrading of the combined cooling heat and power system and improving the regenerating process adopted in the first design of an existing project. Linking between refrigeration and air-conditioning systems is proposed in scheme-II. A single-effect absorption chiller operating in the range of refrigeration scale (i.e. aqueous-ammonia refrigeration, not air-conditioning scale, LiBr–H₂O employed in scheme-I) will be adopted using pressurised hot water recovered from the generators. The chilled water system will be serving three categories in the following order, namely, refrigeration stores, cold stores and air-conditioning units, respectively. The chilled water output of the first category will be the input of the second one. This will enhance the overall system efficiency, reduce the generator load and lessen the fugitive refrigerant emissions, which mainly participate in ozone-depleting potential and global-warming potential. This is in addition to the dramatic reduction in initial and operating cost, which can be estimated to be 50% and 79.6%, respectively.     

考虑压降的开式布雷顿CHP装置性能优化

考虑工质在流动过程中的压降不可逆性,建立开式简单布雷顿热电联产装置的有限时间热力学模型。以可用能率、火用输出率、利润率、第一定律效率和火用效率为目标研究装置的性能。通过Matlab数值计算,在无燃料消耗和装置尺寸约束下,优化了压气机进口相对压降,得到了最优可用能率、火用输出率和利润率,进一步优化压比,得到了最大火用输出率和利润率;在有约束条件下,优化压气机进口相对压降,得到了最优第一定律效率和火用效率,同时得到了各部件最佳的流通面积分配,进一步优化压比,得到了最大第一定律效率和火用效率。研究设计参数对装置最优性能的影响,发现分别存在最佳的供热温度使火用输出率、利润率和火用效率取得双重最大值。通过比较发现按最大火用输出率设计能使装置具有较大的可用能率和较低的压比,按最大利润率设计能使装置具有较大的第一定律效率和火用效率以及较低的燃料和空气消耗。