The impact of the integration of renewable energy sources in the electricity price formation: is the Merit-Order Effect occurring in Portugal?

This study investigates the relationship between wholesale electricity price behaviour and the integration of new renewable energy sources in the electricity system in Portugal. The research analyses two different samples, namely: the significant deployment of wind power versus the abrupt increase in the installed capacity of solar photovoltaic. Daily data from 2011 until 2019 and, a SARMAX/EGARCH approach has been conducted to assess the merit-order effect. The main results suggest that electricity production from wind power is decreasing the price of electricity but increasing its volatility. In addition, there is evidence for the leverage effect in electricity price.     

Multi-objective optimal control of an air-to-water heat pump for residential heating

The current study investigates the optimal operation of an air-to-water heat pump system. To this end, the control problem is formulated as a classic optimal control or dynamic optimization problem. As conflicting objectives arise, namely, minimizing energy cost while maximizing thermal comfort, the optimization problem is tackled from a multi-objective optimization perspective. The adopted system model incorporates the building dynamics and the heat pump characteristics. Because of the state-dependency of the coefficient of performance (COP), the optimal control problem (OCP) is nonlinear. If the COP is approximated by a constant value, the OCP becomes convex, which is easier to solve. The current study investigates how this approximation affects the control performance. The optimal control problems are solved using the freely available Automatic Control And Dynamic Optimization toolkit ACADO. It is found that the lower the weighting factor for thermal discomfort is, the higher the discrepancy is between the nonlinear and convex OCP formulations. For a weighting factor resulting in a quadratic mean difference of 0.5°C between the zone temperature and its reference temperature, the difference in electricity cost amounts to 4% for a first scenario with fixed electricity price, and up to 6% for a second scenario with a day and night variation in electricity price.     

天然气分布式能源系统高效性、经济性评价

结合工程实例,对天然气分布式能源系统的高效性(评价指标为节能率)进行评价,对经济性的影响因素进行分析。经济性指标为静态投资回收期,影响因素:单因素:项目总投资额、天然气价格、运行时间、售电价格、售冷价格;双因素:单位发电功率投资额+电气比(售电价格与天然气价格比)、单位发电功率投资额+冷气比(售冷价格与天然气价格比)。运行时间、售电价格、售冷价格对静态投资回收期的影响一致,随着运行时间、售电价格、售冷价格的延长和增大,静态投资回收期缩短,3个因素的影响显著性依次减弱。天然气价格、项目总投资额对静态投资回收期的影响一致,随着天然气价格、项目总投资额的增大,静态投资回收期延长,天然气价格的影响更.显著。单位发电功率投资额一定时,静态投资回收期随电气比的增大而缩短。电气比一定时,静态投资回收期随单位发电功率投资额的减小而缩短。单位发电功率投资额越小,电气比越大,静态投资回收期越短。单位发电功率投资额一定时,静态投资回收期随冷气比的增大而缩短。冷气比一定时,静态投资回收期随单位发电功率投资额的减小而缩短。单位发电功率投资额越小,冷气比越大,静态投资回收期越短。     

Gas and electricity demand in Spanish manufacturing industries: An analysis using homogeneous and heterogeneous estimators

A comparative analysis of electricity and gas demand in the industrial sector over a long period of time appears to be absent in the literature. In fact, unlike electricity demand, natural gas demand in the industrial sector has not been well researched. Our paper aims to cover this gap. It analyses electricity and gas consumption patterns by the Spanish manufacturing sector, between 1995 and 2010. A novel and innovative quantitative approach based on, both, homogenous and heterogeneous estimators was used for this purpose. The results of the no-spurious estimations (the Augmented Mean Group Estimator) show that the price elasticity of gas demand is significantly negative and within the −0.44 to −0.48 range. In contrast, the price elasticity of electricity demand is not statistically significant. The income elasticities show the opposite pattern: those of natural gas are not statistically significant, whereas the income elasticities for electricity are statistically significant and within the 0.22 to 0.29 range. Compared to previous findings, our preferred estimation shows some variation regarding price elasticities of natural gas demand.     

Decision-making framework for supplying electricity from distributed generation-owning retailers to price-sensitive customers

In this paper, a robust bi-level decision-making framework is presented for distributed generation (DG) owning retailers to supply the electricity to price-sensitive customers. Uncertainties about client demand and wholesale prices are the main difficulties faced by the electricity retailer. Clients can adjust their consumption according to the retailer's selling price. A higher selling price increases retailers' profit but decreases client consumption. Hence, the retailer faces a tradeoff between the price and sales. In the proposed model, the optimal selling price and the retailer's energy-supply strategy are modeled in the lower sub-problem. According to the proposed selling price, the optimal energy consumption of price-sensitive clients is determined in the upper sub-problem. To evaluate the financial risk arising from uncertain prices, the Information Gap Decision Theory (IGDT) approach is addressed in the lower sub-problem. Additionally, the risk-based optimization problem is formulated for risk-averse and risk-taker retailers via the robustness and opportunity functions, respectively. The robustness of the optimal solution against price variations is evaluated such that the associated profit will be more than the electricity retailer's acceptable threshold. The efficiency and performance of the decision-making framework are analyzed via a case study, and the numerical results are discussed.     

Asymmetric price response of industrial electricity demand in India

This paper analyses the asymmetric effects of electricity prices on industrial electricity demand in India from 1981 to 2016 using the two-threshold nonlinear autoregressive distributed lag (NARDL) model. The results show that customers react more strongly to a large price cut than a large price increase, whereas a small price change does not affect electricity consumption. A large price decrease, which raises the quantity demanded by a higher percentage, makes it more challenging to reach net-zero emissions as electricity generation relies mainly on fossil fuels. Since demand is inelastic for price increases, a large price hike minimally reduces electricity consumption.     

Investment under RPI-X: Practical experience with an incentive compatible approach in the GB electricity distribution sector

Regulatory price controls on the British (GB) electricity distribution sector have been a marked success. Charges to customers have been reduced, network reliability has improved and companies have made above average returns along the way. Nonetheless, each review brings new challenges. This article describes one of the main innovations introduced at the fourth electricity distribution price review (DPCR4) – an incentive compatible approach to setting capex allowances. We set out the rationale for its adoption, the practicalities in applying the mechanism and its position in the broader context of regulatory developments in the sector.     

Coordination between clean energy generation and thermal power generation under the policy of “direct power-purchase for large users” in China

The inefficient utilization of clean energy and distorted pricing mechanism are the most critical problems that have hampered the reform of China's electric power industry for many years. A large number of clean energy generators have recently been constructed, but water spillage at hydroelectric facilities and wind curtailment persist due to integration challenges. The adjustment of electricity price has relied on executive orders of the Chinese government and the National Development and Reform Commission (NDRC). Distorted prices that are not derived from a market economy have seriously hampered the development of China's electricity market. Therefore, in recent years, the Chinese government has issued a number of reform measures concerning “direct power-purchase for large users”. The main idea of this pricing mechanism is to form direct negotiations between large users and generators to determine the electricity price. To a certain extent, this pricing mechanism is conducive to the electricity market reform in China. However, the coordination between clean energy generation and thermal power generation under the policy of “direct power-purchase for large users” has become the key issue in China's electric power industry. This paper summarizes the policies of “direct power-purchase for large users” in different provinces in China. The electricity market in Yunnan, for which the contradiction between thermal power generation and hydropower generation is increasingly severe, is the focus of the research. At last, a feasible electricity market scheme has been derived to coordinate thermal power generation and hydropower generation. This scheme has considerable theoretical and practical significance to the future of China's electricity market reform.     

Electricity consumers under the state and the private sector: comparing the price performance of the French and UK electricity industries 1990–2000

Particularly because a preoccupation with process has tended to dominate the debate about electricity privatisation and liberalisation, this paper focuses on price outcomes by comparing the relative price performance of the French and UK electricity industries between 1990 and 2000. The main conclusion is that in 1990 the state-owned French electricity industry was performing better for most consumers than the state-owned UK industry, and a decade later it was still doing so with respect to the privately-owned UK industry. While this conclusion could be qualified by saying that, heavily prompted or assisted by the Regulator, the UK privately-owned industry has shown itself capable of achieving faster reductions in prices to close the gap between itself and the French, this achievement has been concentrated in the industrial market and even there the very significant gains were mainly restricted to the very largest consumers. In the context of the European Union the UK is shown to have performed relatively poorly for the smallest domestic consumers and, while both countries did much better in the rankings of industrial prices, they were still a long way behind the top performers.     

Organisation and reforms of the electricity sector in Slovenia

As a new member state of the EU, Slovenia has been required to adopt EU legislation in full. The Slovenian electricity market has been partially opened since 2001. From 1 July 2007, when households became eligible customers, the electricity market opened fully. The electricity reforms carried out so far comprise of market liberalization, unbundling of activities, allowing regulated TPA, formation of an organized power market, adoption of incentive-based price cap regulation and the establishment of an independent regulatory body. The challenge that remains to be addressed is how to enhance competition in an electricity market that has a net importer position with limited cross-border capacity. Envisaged investments in generating and cross-border capacities will partially close the gap between domestic generation and consumption. Furthermore, since Slovenia has one of the largest levels of state ownership in the electricity sector among EU member states, privatization of electricity companies is envisaged in the near future.     

Price and income elasticities of residential electricity demand in Brazil and policy implications

The research objective was to estimate Brazil's residential electricity consumption behavior, given alterations in price and income. A balanced panel with monthly data was used for the 27 states of the country between 2004 and 2019, distributed into the five regions of Brazil. This approach enabled the calculation of price elasticity and income parameters, in the short and long terms, for both national and regional scenarios. They were used, as control variables, the average temperature, which was not used in previous research due to the use of a database with a higher level of aggregation, and the rainfall, that can be considered an important parameter in the Brazilian case where most of the electricity is obtained from hydroelectric generation, however, it has never been used in previous studies. The econometric model was estimated using the Generalized Method of Moments (GMM), version System - GMM (SY - GMM), to avoid dynamic bias of the panel and a serial correlation problem, which has not been considered in previous studies in Brazil. The results show that, although the short and long-term elasticities for the national scenario are similar to previous studies when analyzed regionally, the parameters proved to be quite different from previous research. Based on the results, adjustments were proposed for the Brazilian electricity price policy.     

基于v-SVR和MVPSO算法的边坡位移反分析方法及其应用

 针对传统粒子群算法存在搜索空间有限、容易陷入局部最优点的缺陷,通过引入迁徙算子和自适应变异算子,提出基于粒子迁徙和变异的粒子群优化(MVPSO)算法。基准测试函数结果表明,改进的MVPSO算法较传统的粒子群优化算法在收敛效率上有大幅度提高,在处理非线性、多峰值的复杂优化问题中能快速地搜索,得到全局最优解。应用改进的MVPSO算法搜索最佳的支持向量机(v-SVR)模型参数,建立岩体力学参数与岩体位移之间的非线性支持向量机模型,提高v-SVR的预测精度和推广泛化性。然后,利用v-SVR模型的外推预测替代耗时的FLAC正向计算,利用改进的MVPSO算法搜索岩体力学参数的最优组合,提出v-SVR和MVPSO相结合的边坡位移反分析方法(v-SVR-MVPSO算法),与传统的BP-GA算法和v-SVR-GA算法相比,该算法在反演精度和反演效率上均有较大幅度提高。最后,将本文发展的v-SVR-MVPSO算法应用到大岗山水电站右岸边坡岩体参数反演分析,并对边坡后续开挖位移和稳定性进行预测,取得较好的效果。     

基于改进的遗传模拟退火算法的钢框架优化设计

将遗传算法的全局寻优性能好和模拟退火的局部搜索能力强的优点相结合,提出了用于钢框架优化设计的遗传模拟退火算法,并对其进行了改进。在遗传算法部分提出了基于阈值的动态交叉、变异概率,并且采用联赛精英选择策略和最优保存策略,在种群的整体适应度提高的同时,增强了进化后期的种群多样性,提高了算法的收敛速度。在退火部分,针对钢框架优化的具体问题提出了一种更加紧凑灵活的邻域结构,提高了算法寻优性能。最后,将改进的算法用于工程实例,并与其他优化方法相比较,结果表明,该改进算法是一种用于钢框架结构优化设计的更加行之有效的方法。     

A counterfactual price analysis of British electricity privatisation

The aim of this paper is to challenge the widely held view that electricity privatisation in Great Britain (comprised of the markets of England and Wales, and Scotland) was beneficial simply because the price of electricity has subsequently fallen in real terms. This is carried out by comparing the electricity prices actually observed with those that might have been charged had the industry remained in public ownership. In order to do this the paper develops a counterfactual scenario for the likely decisions and effects of a publicly owned industry. This leads the paper to conclude that observed prices are indeed significantly higher than they would have been had privatisation not occurred.     

AQUIFER PARAMETER ESTIMATION USING GENETIC ALGORITHMS AND NEURAL NETWORKS

Computational tools such as genetic algorithms and neural networks are becoming increasingly popular in scientific applications involving mathematical modeling. These tools emulate natural biological processes in an attempt to build more robust and efficient mathematical models. The present study explores the applicability of genetic algorithms and neural networks for aquifer parameter estimation, in an optimization framework. Although optimization models based on genetic algorithms are more robust than conventional nonlinear programming techniques, they often necessitate many computationally expensive function evaluations. On the other hand, genetic algorithms can also tolerate approximate function evaluations. The present study employs artificial neural networks that provide quick but reasonably accurate function evaluation, in conjunction with genetic algorithms. Such an optimization framework makes the resulting calibration model highly robust and efficient. Applicability of the proposed model is demonstrated on a hypothetical aquifer using synthetic test data. Through an extensive sensitivity analysis, the present study reiterates that a low probability of mutation (0.02-0.03) and a moderately high probability of crossover (0.6-0.7) are essential for good convergence of a genetic optimization model.     

The responses of manufacturing businesses to geographical differences in electricity prices

The price of electricity varies considerably across localities and states. This paper focuses on the geographical differences in electricity prices and the consequences of those differences for business production and location. It accounts for the dynamic nature of business responses to these geographical differences by classifying manufacturing businesses into three groups based on intensity of electricity use and business mobility: (1) heavy users of electricity that are relatively highly mobile; (2) heavy users that are relatively tied to their location; and (3) businesses for which electricity is not a significant cost of production. For empirical analysis, plant- or firm-level data is most desirable, but was not available. As an alternative, the most disaggregate (6-digit NAICS) industry data has been utilized. Findings suggest that heavy users of electricity, regardless of the degree of business mobility, tend to stay in their current location rather than relocate, as they often have a greater technical ability to substitute away from electricity when electricity prices are high.     

Effect of mutation schemes on convergence to optimum design of steel frames

In this paper an attempt is made to modify a distributed genetic algorithm (DGA) to minimize the weight of steel frames. The main aspects of modifications include the twin analogy and a number of mutation schemes. Although the mutation is a secondary operator in the GA, it plays an influential role in diversifying the population and exploring more feasible design space. In this research, four different mutation schemes are examined and their effects on convergence to optimum solutions are evaluated. Using three benchmark examples, it is demonstrated that mutation operator can efficiently influence on the speed of convergence and consequently saving computation time. As coding a program is required, the DO-DGA software has been developed to handle the algorithm. DO-DGA applies modified DGA, including different mutation schemes, to obtain the global optimum solution.     

Forward risk premia in long-term transmission rights: The case of electricity price area differentials (EPAD) in the Nordic electricity market

Hedging behaviour among players in derivatives markets have long been explained by forward risk premia. We provide new empirical evidence from the Nordic electricity market and explore the forward risk premia dynamics on power derivative contracts called electricity price area differentials (EPAD). This contract is critical for the market, but its efficiency has been questioned. The study investigates the significance, direction, and magnitude of forward risk premia in individual bidding areas and contract maturities during the period 2001–2013. We test the hypothesis of a negative relationship between forward risk premia and time-to-maturity, for which we find only partial support.     

European Union emissions trading scheme impact on the Spanish electricity price during phase II and phase III implementation

The European Union Emissions Trading Scheme (EU ETS) is a cornerstone of the European Union's policy to combat climate change and its key tool for reducing industrial greenhouse gas emissions cost-effectively. The purpose of the present work is to evaluate the influence of CO₂ opportunity cost on the Spanish wholesale electricity price. Our sample includes all Phase II of the EU ETS and the first year of Phase III implementation, from January 2008 to December 2013. A vector error correction model (VECM) is applied to estimate not only long-run equilibrium relations, but also short-run interactions between the electricity price and the fuel (natural gas and coal) and carbon prices. The four commodities prices are modeled as joint endogenous variables with air temperature and renewable energy as exogenous variables. We found a long-run relationship (cointegration) between electricity price, carbon price, and fuel prices. By estimating the dynamic pass-through of carbon price into electricity price for different periods of our sample, it is possible to observe the weakening of the link between carbon and electricity prices as a result from the collapse on CO₂ prices, therefore compromising the efficacy of the system to reach proposed environmental goals. This conclusion is in line with the need to shape new policies within the framework of the EU ETS that prevent excessive low prices for carbon over extended periods of time.     

The impact of renewable energy on household electricity prices in liberalized electricity markets: A cross-national panel data analysis

The main research questions addressed in this paper are: first, have electricity market reforms achieved lower household electricity prices and, second, has the introduction of renewable energy increased household electricity prices in deregulated markets Answers to the questions were derived using static and dynamic panel data analysis from 1991 to 2014 employing explanatory variables such as the extent of electricity market reform and the share of generation from renewable energy resources. The dynamic model suggests that a lower household electricity price is associated with the degree of electricity market reform, while the share of renewable energy in electricity generation is not statistically significant.