影响冷热电联产系统经济性因素的灰关联分析

1引言发展天然气冷热电联产项目,对于削减电网的高峰负荷、缓解能源供需矛盾、提高能源综合利用效率、减轻污染,改善环境、降低因燃料调整带来的成本增加十分有利。燃气轮机冷热电联产运行的经济性是系统应用研究的一个重要内容。而影响系统运行经济性的因素是多方面的。如燃气     

华东区域电力客户与发电企业直接交易的可行性分析

电力客户与发电企业直接交易是电力市场深化改革的重要内容之一。介绍了华东区域电力客户与发电企业跨省直接交易模式开展的前提条件和经济利润的可行性分析。从经济角度提出了利润空间的概念以及计算模型,通过计算跨省交易的利润空间,得出上海地区典型大客户与安徽省发电企业进行跨省直接交易和在上海市内部进行直接交易相比,更具诱惑力,更能充分利用资源、体现价值和促进资源的优化配置。同时还验证了:输配电价的不同,将直接影响利润空间的大小;输配电价的合理性,将直接影响利润空间的准确度。     

High-performance gas–electricity cogeneration using a direct carbon solid oxide fuel cell fueled by biochar derived from camellia oleifera shells

Direct carbon solid oxide fuel cells (DC-SOFCs) are promising for generating electricity cleanly and efficiently from solid carbon fuel. Biochar from Camellia oleifera shells is used in a tubular electrolyte-supported 2-cell DC-SOFC stack with a yttrium-stabilized zirconia (YSZ) electrolyte and silver–gadolinium-doped ceria (Ag-GDC) as symmetrical electrodes. The DC-SOFC exhibits comparable electrical performance to the same cell operated on hydrogen fuel and can cogenerate CO and electricity when fueled by biochar. The gas–electricity cogeneration performance of the DC-SOFC is tested under constant-current discharge in terms of electrical power output, CO output rate and purity, electrical conversion efficiency, and gas–electrical cogeneration conversion efficiency. The purity of the output CO can reach more than 80%. Considering the chemical energy of CO a part of the output power, the energy conversion efficiency of >70% is attained. Furthermore, the gas–electricity cogeneration performance is relatively stable before the biochar fuel is exhausted.     

Energy and exergy performance assessments of a high temperature-proton exchange membrane fuel cell based integrated cogeneration system

High-temperature proton exchange membrane fuel cell (HT-PEMFC), which operates between 160 °C and 200 °C, is considered to be a promising technology, especially for cogeneration applications. In this study, a mathematical model of a natural gas fed integrated energy system based on HT-PEMFC is first developed using the principles of electrochemistry and thermodynamics (including energy and exergy analyses). The effects of some key operating parameters (e.g., steam-to-carbon ratio, HT-PEMFC operating temperature, and anode stoichiometric ratio) on the system performance (electrical, cogeneration, and exergetic efficiencies) are examined. The exergy destruction rates of each component in the integrated system are found for different values of these parameters. The results show that the most influential parameter which affects the performance of the integrated system is the anode stoichiometric ratio. For the baseline conditions, when the anode stoichiometric ratio increases from 1.2 to 2, the electrical, cogeneration, and exergetic efficiencies decrease by 42.04%, 33.15%, and 37.39%, respectively. The highest electrical power output of the system is obtained when the SCR, operating temperature, and anode stoichiometric ratio are taken as 2, 160 °C, and 1.2, respectively. For this case, the electrical, cogeneration, and exergetic efficiencies are found as 26.20%, 70.34%, and 26.74%, respectively.     

European CO2 prices and carbon capture investments

We assess the option to install a carbon capture and storage (CCS) unit in a coal-fired power plant operating in a carbon-constrained environment. We consider two sources of risk, namely the price of emission allowance and the price of the electricity output. First we analyse the performance of the EU market for CO₂ emission allowances. Specifically, we focus on the contracts maturing in the Kyoto Protocol's first commitment period (2008 to 2012) and calibrate the underlying parameters of the allowance price process. Then we refer to the Spanish wholesale electricity market and calibrate the parameters of the electricity price process.We use a two-dimensional binomial lattice to derive the optimal investment rule. In particular, we obtain the trigger allowance prices above which it is optimal to install the capture unit immediately. We further analyse the effect of changes in several variables on these critical prices, among them allowance price volatility and a hypothetical government subsidy.We conclude that, at current permit prices, immediate installation does not seem justified from a financial point of view. This need not be the case, though, if carbon market parameters change dramatically, carbon capture technology undergoes significant improvements, and/or a specific governmental policy to promote these units is adopted.     

燃气轮机冷热电联产系统技术与经济性分析

分析了现有商业燃气轮机用于热电联产系统和冷热电联产系统时的性能。与常规分产系统相比,两系统在热力学性能上均有较大优势,绝大多数节能率超过20％。功率较小的燃气轮机单位造价偏高,用于冷热电联产系统时经济性较差;随着功率的增加经济性不断改善,冷热电联产系统的经济性受到很多因素的影响,其中运行时间和电价的影响最明显,其次为燃料价格的影响,热价和冷价的影响相对最小;这些因素在燃气轮机功率较小时影响较大,随功率的增加影响逐渐减小。     

Multi-criteria optimization in a methanol process

Opportunities for additional profit in retrofits depend very much on the existing plant structure, its parameters and energy system. Combined production of heat flow rate, power and chemical products can improve process efficiency. This paper presents an application of the nonlinear programming (NLP) optimization techniques, including increased chemical product output, heat integration and electricity cogeneration by changing amount flow ratios of raw material, and modifying the separation and reaction systems. The existing NLP model has been extended with basic chemical kinetics, including the effects of changing raw material flow rate ratios on product yield.A case studied methanol plant was optimized using the NLP model developed earlier by including an additional flow rate of hydrogen (H₂), decreasing flow rate of high-pressure steam in crude methanol recycling, and increasing methanol production by 2.5%. The potential additional profit from the cogeneration and additional methanol production was estimated to be 2.51 MEUR/a.     

考虑源荷不确定性的分时电价动态修正机制研究

针对新型电力系统中可再生能源出力及负荷需求的不确定性造成源荷协调困难,导致难以制定合理的分时电价的问题,该文提出一种考虑源荷不确定性的分时电价动态修正机制。首先,根据可再生能源出力的波动性以及不确定性,建立新能源并网功率与并网电量偏差量化模型;其次,根据需求侧负荷的变化特征,结合可再生能源出力不确定性,通过多种不确定性因素影响条件的误差计算方法,建立电价概率密度模型。然后,根据负荷上报的用电量以及预报电价,建立考虑源荷不确定性的电力市场分时电价动态修正与优化模型,并采用粒子群算法进行模型求解。最后,通过实际运行数据仿真验证该文所提方法的有效性。     

Consumer loss in Czech photovoltaic power plants in 2010–2011

This paper provides a financial survey of a small sample of Czech photovoltaic (PV) plants. To evaluate the extent of market losses, we calculate the shadow market price of solar electricity. From the profit and loss accounts of the PV plants and the shadow market price we estimate the total economic loss generated by PV electricity sector in the Czech Republic. The presented microeconomic approach has two main advantages: firstly, we work with real observed data, which offsets the drawback of a limited sample. Secondly, the profit accounting calculation enables sensitivity analysis with respect to key variables of the plants. We show that money invested in PV plants would generate an annual loss of 8%. Given the estimated solar assets of CZK 165.6 billion (EUR 6.6 billion) as of December 2011, this translates in at least CZK 12.6 billion lost in the Czech solar sector in 2012. About 43% of this loss is due to high technology costs and corresponds to pure dead weight loss, while the remaining 57% constitute the redistributive profit component of subsidies. Finally, we calculate that unless electricity prices increase or technology costs decrease approximately sevenfold, PV plants will remain loss making.     

A method for the correction of the feed-in tariff price for cogeneration based on a comparison between Croatia and EU Member States

The European Commission has adopted Directive 2004/8/EC on the promotion of cogeneration, which the EU Member States, as well as candidates including Croatia, were obliged to accept. Among other terms and conditions, the Directive requires certain support mechanisms, such as feed-in tariff prices and premiums added to market electricity prices. In this paper, the cost effectiveness of selling electricity at the feed-in tariff prices in the selected EU Member States is compared to selling it on the European electricity market, with or without premiums. The results of this comparison will indicate whether correction of the Croatian feed-in tariff price to a higher value would be justified. The cost effectiveness ratio of a cogeneration unit upgraded with mean reverting and jump diffusion processes is used for comparison. At the end of this paper, a method is suggested for the correction of feed-in tariff prices, with examples of corrected prices for the years 2008 and 2009. Such corrections have been proven to be justified and are compared to the feed-in tariff prices in most of the selected EU Member States.     

A proposed market power monitoring model for restructuringelectricity markets

This paper presents a market power monitoring model for electricity markets. It is a social welfare maximization model subject to nonnegative short-term profit constraints. Traditional economics claims that market power exists whenever the price is above the corresponding marginal cost. However, this paper argues that a generator cannot be considered to be exercising any market power if it earns zero profit considering only variable cost     

Coproduction of district heat and electricity or biomotor fuels

The operation of a district heating system depends on the heat load demand, which varies throughout the year. In this paper, we analyze the coproduction of district heat and electricity or biomotor fuels. We demonstrate how three different taxation scenarios and two crude oil price levels influence the selection of production units to minimize the district heat production cost and calculate the resulting primary energy use. Our analysis is based on the annual measured heat load of a district heating system. The minimum-cost district heat production system comprises different production units that meet the district heat demand and simultaneously minimize the district heat production cost. First, we optimize the cost of a district heat production system based on the cogeneration of electricity and heat with and without biomass integrated gasification combined-cycle technology. We considered cogenerated electricity as a byproduct with the value of that produced by a condensing power plant. Next, we integrate and optimize different biomotor fuel production units into the district heat production system by considering biomotor fuels as byproducts that can substitute for fossil motor fuels. We demonstrate that in district heating systems, the strengthening of environmental taxation reduces the dependence on fossil fuels. However, increases in environmental taxation and the crude oil price do not necessarily influence the production cost of district heat as long as biomass price is not driven by policy measures. Biomotor fuel production in a district heating system is typically not cost-efficient. The biomotor fuels produced from the district heating system have to compete with those from standalone biomotor fuel plants and also with its fossil-based counterparts. This is also true for high oil prices. A carbon tax on fossil CO₂ emissions based on social cost damage will increase the competitiveness of biomass-based combined heat and power plants, especially for BIGCC technology with its high electricity-to-heat ratio.     

Grid parity analysis of solar photovoltaic systems in Germany using experience curves

The paper starts with experience curve analysis in order to find out the future prices of solar photovoltaic (PV) modules. Experience curves for 75-90% progress ratio are extrapolated with the help of estimated future growth rate for PV installation worldwide and current module price data until year 2060. A kWh PV electricity generation cost has been calculated for coming decades with the help of local market parameters and module prices data from extrapolated experience curve. Two different prices for grid electricity - wholesale electricity price and end user electricity price - are separately analyzed. Household electricity consumption profile and PV electricity generation profile for Cologne, Germany, have been analyzed to find out the possibility for PV electricity consumption at the time of its generation. This result is used to calculate the real grid parity year - which lies somewhere between grid parity years calculated for wholesale electricity price and end user electricity price.     

偏差电量考核下风光储混合发电商的市场均衡博弈研究

为了更直观地分析风光储混合发电商对市场均衡博弈结果和市场力的影响,在偏差电量考核衡量风光储混合发电出力随机波动性的基础上,综合考虑各发电商的出力限制和储能系统的运行约束,建立以风光储混合发电商和传统发电商收益最大化为目标的市场均衡博弈模型,调用CPLEX软件求解利用非线性互补函数处理得到的混合整数规划模型,并对比分析了风光储混合发电商作为价格接受者和影响者参与电力市场竞争对均衡博弈电价和投标出力的影响。结果表明,风光储混合发电商参与电力市场竞争可抑制传统发电商的市场力,对电价有显著的"削峰填谷"作用;当风光储混合发电商作为价格影响者时,对电价的影响会减弱,但其收益有所增加。     

Potential evaluation of power-to-hydrogen-to methane conversion technology in robust optimal energy management of a multi-energy industrial park

Multi-energy industrial parks are required to render a huge variety of services in an eco-friendly, secure, reliable, and affordable way. The industrial energy park is a separate area consisting of multiple distributed generations, energy storage systems, etc., which supply local gas, heating, and electrical consumers. Meanwhile, the integration of power-to-X technologies such as power-to-gas and power-to-heat, which convert the electricity into other forms of energies while facilitating the integration of renewable energy in the industrial park, can enhance the flexibility and efficiency of energy supply. Therefore, this paper proposes novel robust energy management of multi-energy industrial parks integrated with wind power resources, cogeneration units, power-to-X technologies, and demand response programs to total operation cost minimization. The industrial park can simultaneously participate in a multi-energy market, including power, thermal, and gas markets, to meet local heating, gas, and electrical load. The robust optimization framework is extended to address the power price uncertainty and manage the conservatism level of the operator against price variability. The proposed model is examined on the industrial park test system, and numerical results will be presented for the different cases. Under the robust energy management, the total operation cost of the multi-energy industrial park reduces up to 53 %.     

热电联产机组的电力调峰运行模式研究

随着社会发展和产业结构的不断调整,用电结构不断变化,广东电力系统面临着日益加剧的调峰问题,系统调峰能力的不足成为制约电力发展的一个重要因素。利用热电联产机组参与调峰是解决上述问题的有效途径。文章从热电联产机组的建模出发,研究发电热耗、供电气耗、热电比与联合循环供电出力、供热量之间的关系,得出影响机组调峰能力的因素及调峰范围,通过对热电联产机组调峰能力的分析,提出热电联产机组应对电力系统调峰的运行模式。     

Hedging local volume risk using forward markets: Nordic case

With focus on the Nordic electricity market, this paper develops hedging strategies for an electricity distributor who manages price and volume risk from fixed price agreements on stochastic electricity load. Whereas the distributor trades in the spot market at area prices, the financial contracts used for hedging are settled against the system price. Area and system prices are correlated with electricity load, as are price differences. In practice, however, this is often disregarded. Here, we develop a joint model for the area price, the system price and the load, accounting for correlations, and we suggest various strategies for hedging in the presence of local volume risk. We benchmark against a strategy that ignores correlation and hedges at expected load, as is common practice in the industry. Using data from 2013 and 2014 for two Danish bidding areas, we show that our best hedging strategy reduces gross loss by 5.8% and 13.6% and increases gross profit by 3.8% and 9.5%, respectively. Although this is partly due to the inclusion of correlation, we show that performance improvement is mainly driven by the choice of risk measure.     

Achieving emissions reduction through oil sands cogeneration in Alberta’s deregulated electricity market

The province of Alberta faces the challenge of balancing its commitment to reduce CO₂ emissions and the growth of its energy-intensive oil sands industry. Currently, these operations rely on the Alberta electricity system and on-site generation to satisfy their steam and electricity requirements. Most of the on-site generation units produce steam and electricity through the process of cogeneration. It is unclear to what extent new and existing operations will continue to develop cogeneration units or rely on electricity from the Alberta grid to meet their energy requirements in the near future. This study explores the potential for reductions in fuel usage and CO₂ emissions by increasing the penetration of oil sands cogeneration in the provincial generation mixture. EnergyPLAN is used to perform scenario analyses on Alberta’s electricity system in 2030 with a focus on transmission conditions to the oil sands region. The results show that up to 15–24% of CO₂ reductions prescribed by the 2008 Alberta Climate Strategy are possible. Furthermore, the policy implications of these scenarios within a deregulated market are discussed.     

Black liquor gasification—consequences for both industry and society

The pulp and paper industry consumes large quantities of biofuels to satisfy process requirements. Biomass is however a limited resource, to be used as effectively as possible. Modern pulping operations have excess internal fuels compared to the amounts needed to satisfy process steam demands. The excess fuel is often used for cogeneration of electric power. If market biofuel availability at a reasonable price is limited, import/export to/from a mill however changes the amount of such biofuel available for alternative users. This work compares different mill powerhouse technologies and CHP plant configurations (including conventional recovery boiler technology and black liquor gasification technology) with respect to electric power output from a given fuel resource. Different process steam demand levels for different representative mill types are considered. The comparison accounts for decreased/increased electricity production in an alternative energy system when biofuel is imported/exported to/from the mill. The results show that black liquor gasification is in all cases considered an attractive powerhouse recovery cycle technology. For moderate values of the marginal electric power generation efficiency for biofuel exported to the reference alternative energy system, excess mill internal biofuel should be used on mill site for gas turbine based CHP power generation. The remaining excess biofuels in market pulp mills should be exported and used in the reference alternative energy system in this case. For integrated pulp and paper mills, biofuel should be imported, but only for cogeneration usage (i.e. condensing power units should be avoided). If biofuel can be used elsewhere for high efficiency CHP power generation, mill internal biofuel should be used exclusively for process heating, and the remainder should be exported.     

基于电价影响的水电站装机容量选择

针对不同电价对水电站装机容量影响的决策问题，通过水力发电过程相关物理参数的数学建模，揭示了水电站投入产出关系曲线的凸性，利用经济学的边际分析原理，得出在利润最大化的原则下，水电站年化投资的边际单位电度成本等于电价时，水电站取得最优投资和最优装机容量，从而阐明了电价与水电站装机容量相互影响的内在规律，为选择水电站装机容量提供了技术经济理论依据。