Surplus Generation Research Articles

Costs Impact of a Transition to Hydrogen-fueled Vehicles on the Spanish Power Sector

It is expected that demand response might provide soon ancillary services to the power system. This could be done, for example, by managing the use of Electric Vehicles (EV) batteries, or the production of flexible energy commodities such as hydrogen (H2), that can be used for fuel cell vehicles (H2EV) or in industrial processes. This paper analyses the impact of a transition to H2EV as an alternative to EV for passengers’ cars on a Spanish-like power sector. A simple H2 demand estimation is developed and provided to CEVESA, an operation and expansion model for the Iberian Power System Electricity Market (MIBEL). For this study, CEVESA was extended to include the investments and operation decisions of H2 production. Simulations were performed to determine the optimal evolution of the H2 production capacity and of the electricity generation mix, considering scenarios with different shares of EV and H2EV. The impact of H2EV vs EV mobility is assessed based on the recent Spanish National Plan for Energy and Climate (NECP) as the base case scenario. Results show that, even if H2EV mobility alternative is still more costly than EV, H2 production could provide a significant flexibility to the system that should also be appraised. Indeed, H2EV mobility could become a feasible and complementary alternative to decarbonize mobility by powering H2 production with the renewable generation surplus. This, together with the on-going learning process of this technology that will decrease its production costs and increase its efficiency in the coming years, could boost, even more, the development of the H2 economy.

Modeling and scheduling of residential electric loads for energy self‐sufficiency

AbstractThe utility company enforces a limit on the amount of energy injected into the utility grid from residential renewable plants due to the stability/protection concerns caused by the reverse power flow. Under this scenario, a proper load scheduling at the consumer end is necessary to ensure maximum renewable energy utilization during the surplus generation. This article proposes a novel objective function to impart energy self‐sufficiency for residential consumers who own electric vehicles and renewable energy power plants. The proposed objective function aims to promote the consumers to utilize the local sources such as the battery of an electric vehicle, solar PV, wind, etc., effectively through load scheduling. A dedicated program in MATLAB platform is developed for load scheduling, and an experimental case study is conducted using the forecasted demand and generation profiles collected from 10 typical residential consumers. Three new techno‐economic parameters namely, aggregate daily exchanged energy, daily average discharged energy, and daily average self‐sufficiency hours are proposed to conduct the comparative study. An Average Rank ranking method is introduced to evaluate the effectiveness of the proposed and conventional objective functions statistically. The result analysis proves that load scheduling using the proposed objective function secure the best Average Rank of 2.02 compared to the conventional objective functions.

Capacity credit and market value analysis of photovoltaic integration considering grid flexibility requirements

Abstract Rising share of integrated variable renewable energy production may create power curtailment and renewable market value drop. In this work, the states of examined objectives that experienced rising photovoltaic (PV) penetration are described, challenges considering ramp rates and renewable curtailment illustrated. Meanwhile, a renewable capacity credit analysis approach was introduced, scenarios for PV integration were illustrated through an integration model considering the grid operational constraints, and the resulting PV power capacity credit was also presented. Results indicated that surplus generation presented significant monthly variations, and PV capacity credit value presented a lower increasing rate with rising integrated PV power capacity. The effect of a rising integrated PV power system on electricity trading price was illustrated based on open market data. The value of real-time market trading price presented a decreasing trend in response to a rising contribution of PV power production to flexible load. A decrease was obvious at initial rising integrated PV production, and more than half a drop was observed when flexibility limitation was reached. Furthermore, the economic performance of power to heat and power to gas for excess PV power production utilization was assessed and compared, annual utilization ratio plays a crucial role in their cost competitiveness.

The stranger in the German energy system? How energy system requirements misalign with household preferences for flexible heat pumps

By combining findings from techno-economic modelling with those from a survey of households, this article pursues an interdisciplinary approach to answer the question to what extent flexibly operated heat pumps (FHP) offer the potential to reduce the surplus generation from renewable energy sources (RES) through demand response (DR). First, we used an optimisation model to evaluate the potentials of two different DR signals to minimise the electricity costs for heat pump operation and surplus generation from RES. Second, we conducted a survey study (n = 985), the design of which was informed by the outcomes of the optimisation model. Third, we combined the findings from the two analyses to estimate market shares and link these back to the expected contribution of FHPs for RES integration. Our main findings include: even if the monetary savings due to DR were passed on fully to FHP adopters, the RES integration by FHPs would be limited due to a lack of FHP adoption. One of the main challenges is that to make FHPs useful for RES integration, an external data exchange is needed. This is, however, unattractive to consumers and thus reduces market shares. In particular, despite external data exchange allowing for higher financial savings (€110/a with data exchange vs. €57/a without), we find that FHPs without data exchange are evaluated as overall more attractive. Thus, policy measures are needed to leverage the RES integration potential of FHPs.

A Novel and Optimal Battery Sizing Procedure Based on MG Frequency Security Criterion Using Coordinated Application of BESS, LED Lighting Loads, and Photovoltaic Systems

This paper proposes a novel and optimal battery sizing procedure for the primary frequency control (PFC) of islanded microgrid (MG). The Battery Energy Storage System (BESS), Photovoltaic (PV) systems and LED Lighting Loads (LEDLLs) are coordinated to quickly intercept frequency deviation in the stage of PFC. The PVs decrease their power generation in the case of surplus of power generation. The LEDLLs decrease their power consumption in the case of power shortage. The BESS participates in PFC in both cases by injecting/absorbing power. Some batteries with overloading characteristics are capable of fast discharge/charge for a short period, which can be used to reduce the required battery size for PFC application. The conventional overloading characteristics is based on constant power discharge/charge, but the BESS power varies in response to frequency deviation. To overcome this problem, a modified overloading characteristic is presented based on variable power discharge/charge, which is used to propose a battery sizing algorithm. The Genetic Algorithm is used to optimally determine the frequency controllers’ coefficients of the BESS, PVs and LEDLLs to minimize the required battery size while maintaining the MG frequency within safe operational limits. The proposed battery sizing procedure is evaluated on the CIGRE low voltage benchmark system using simulation in MATLAB/Simulink software. The results show that beside the overloading characteristics of the battery, the participation of PVs and LEDLLs in PFC also reduces the required battery size, because their participation reduces the share of BESS participation in PFC.

Discovery and Instrumentation: How Surplus Knowledge Contributes to Progress in Science

An important fact about human labor is that it can result not just in reproduction of what it started with, but in something new, a surplus product. When the latter is a means of production, it makes possible a mechanism of change consisting of reproduction by means of the expanded means of production. Each iteration of the labor process can differ from the preceding one insofar as it incorporates the surplus generated previously. Over the long-term, this cyclical process can lead to the self-transformation of labor and, through it, of human societies and cultures. In this paper, I argue that this mechanism of change is also at work in the history of science. I argue that the form this mechanism takes in science is that of a feedback loop between discovery and instrument construction. This process requires the integration, and transformation into material form, of different kinds of knowledge. Based on this mechanism, I defend a concept of scientific progress as transcendence of the limitations of native human epistemic abilities. I also criticize narrowly biologistic approaches to the history of science for ignoring the role of surplus generation in transforming the labor process, and discuss some problems associated with viewing science as labor.

The impacts of an integrated European adjustment market for electricity under high share of renewables

The European Commission has set a target of establishing an integrated Europe-wide electricity market for day-ahead and intraday transactions. However, there are still many open questions on the potential benefits of a Europe-wide intraday market integration and the harmonizing market rules. This paper intends to provide a precise insight into the potential impacts of EU policies regarding integrating electricity markets on market efficiency and on different market players with the aim of supporting policy makers to increase the penetration of renewables in a cost efficient manner. In this paper, we investigate and compare the current option of regional intraday electricity market with the option of an integrated Europe-wide one, with reference to the three European test cases with high renewable penetration: the Iberian electricity market including Spain and Portugal, the Italian electricity market including Italy and Slovenia, and the electricity market of Germany. We consider two 2030 scenarios: (i) the regional/local intraday electricity market, and (ii) the integration of the current regional intraday market of the test cases into a single intraday market in Europe. The two scenarios are modelled through stochastic Monte Carlo simulation, considering uncertainty on electricity demand, wind and solar power. The performance of the intraday market under the two options are compared in terms of generation cost, electricity prices, producer’ surplus, and load expenditure inside the European test cases. The simulation results lead to the conclusion that integrating to a Europe-wide intraday electricity market is not advantageous for power producers inside the European countries with high share of variable renewable generation, in terms of annual generation surplus. However, from the customers’ point of view, intraday market integration is beneficial, leading to lower cost to loads. Furthermore, it is shown that the flexibility provided by the installed capacity of hydro pumped-storage generators within Europe, by 2030, eliminates the planned curtailment of renewable energy sources in day-ahead and intraday markets and confines the impact of market integration on the market performance indicators.

Distributed Piecewise Approximation Economic Dispatch for Regional Power Systems Under Non-Ideal Communication

Appropriate distributed economic dispatch (DED) strategies are of great importance to manage wide-area controllable generators in wide-area regional power systems. Compared with existing works related to ED, where dispatch algorithms are carried out by a centralized controller, a practical DED scheme is proposed in this paper to achieve the optimal dispatch by appropriately allocating the load to generation units while guaranteeing consensus among incremental costs. The ED problem is decoupled into several parallel sub-problems by the primal-dual principle to address the computational issue of satisfying power balance between the demand and the supply from the distributed regional power system. The feasibility test and an innovative mechanism for unit commitment are then designed to handle extreme operation situations, such as low load level and surplus generation. In the designed mechanism, the on/off status of units is determined in a fully distributed framework, which is solved using the piecewise approximation method and the discrete consensus algorithm. In the algorithm, the push-sum protocol is proposed to increase the system adaptation on the time-varying communication topology. Moreover, consensus gain functions are designed to ensure the performance of the proposed DED under communication noise. Case studies on a standard IEEE 30-bus system demonstrate the effectiveness of our proposed methodology.

Porous Silicon-Based Catalysts for the Dehydration of Glycerol to High Value-Added Products

Increasing worldwide biodiesel production has led to the generation of an important glycerol surplus, which needs to be valorized in order to improve the economic and environmental sustainability of the biodiesel industry. In this context, glycerol dehydration to acrolein by acid catalysis appears to be a potential route of glycerol valorization, since acrolein is an important intermediate for many chemical industries. The main drawback of this catalytic process is catalyst deactivation. Different alternatives have been proposed for overcoming it, such as the use of mesoporous materials in order to facilitate the diffusion of glycerol and reaction products, thus minimizing deactivation. This review compiles the main achievements of the use of mesoporous silica-containing materials that have been deployed either as a catalyst or for support in glycerol dehydration to acrolein. Thus, the effect of mesoporosity on both catalytic performance and deactivation will be discussed, as well as the blocking of pores by coke deposition.

The impact of social and weather drivers on the historical electricity demand in Europe

Climate change, technological innovation, as well as electrification of energy services to meet carbon targets, have a significant impact on electricity demand magnitude and patterns. Increasing generation from renewable energy sources is already changing supply variability at the hourly and seasonal timescales. Our aim is to conduct a rigorous study of European historical demand, to understand its relationship with social and weather drivers and, therefore, to gain insights into appropriate storage needs.Daily activity profiles exhibit notable differences across European countries, with some of them reporting a consistent demand reduction, up to 25%, during school closures and Christmas festivities. In addition, temperature sensitivity differentiates demand by countries’ latitude (north vs. south), and by technologies (electric heating vs. other fuel based heating). Assuming a 100% renewables scenario, European countries would display quite distinct periodicities and amplitudes of their residual electricity demands.Annual load curves and temperature sensitivities of nations with high electric heating or cooling demand can assist in the prediction of future electricity and other fuel consumption under increased electrification and climate change scenarios. Fourier periodicity and residual demand analysis suggest that, in addition to grid storage, European countries with mutual energy needs – in terms of seasonal demand and generation surplus – might benefit from international trade to balance unmet demand. Our study of consumption variability in response to social and weather drivers constitutes a valuable resource to formulate country-specific demand scenarios, as well as to improve the design of energy system models.

Analysing the potential of integrating wind and solar power in Europe using spatial optimisation under various scenarios

The integration of more variable renewable energy sources (vRES) like wind and solar photovoltaics (PV) is expected to play a significant role in reducing carbon dioxide emissions from the power sector. However, unlike conventional thermal generators, the generation patterns of vRES are spatially dependent, and the spatial distributions of wind and PV capacity can help or hinder their integration into the power system. After reviewing existing approaches for spatially distributing vRES, we present a new method to optimise the mix and spatial distribution of wind and PV capacity in Europe based on minimising residual demand. We test the potential of this method by modelling several scenarios exploring the effects of vRES penetration, alternative demand profiles, access to wind sites located far offshore, and alternative PV configurations. Assuming a copper-plate Europe without storage, we find an optimum vRES penetration rate of 82% from minimising residual demand, with an optimum capacity mix of 74% wind and 26% PV. We find that expanding offshore wind capacity in the North Sea is a ‘no regret’ option, though correlated generation patterns with onshore wind farms in neighbouring countries at high vRES penetration rates may lead to significant surplus generation. The presented method can be used to build detailed vRES spatial distributions and generation profiles for power system modelling studies, incorporating different optimisation objectives, spatial and technological constraints. However, even under the ideal case of a copper-plate Europe, we find that neither peak residual demand nor total residual demand can be significantly reduced through the spatial optimisation of vRES.

Energy-Internet-oriented microgrid energy management system architecture and its application in China

In order to address the practical challenges posed by the increasing penetration of distributed energy resources and electric vehicles, the evolution from traditional power systems to Energy Internet and the rapidly changing market and policy environments in China, this paper proposes an Energy-Internet-oriented architecture of microgrid energy management system for China, considering specific technical requirements, markets and policies in China. Following the proposed architecture, the robust operation of a multi-energy microgrid with renewable energy and load uncertainties is formulated as a two-stage robust optimization problem and the column and constraints generation algorithm is used to solve it. A real-life case study in China, Beijing Goldwind Industrial Park, is conducted to demonstrate the proposed architecture and method. Simulation results show that by exporting surplus generation to the external customers and bulk power grid, as an important feature of the market dimension of the proposed architecture, the revenue of the microgrid is improved significantly compared to the traditional business mode. Moreover, as important features of technology and regulation dimensions of the proposed architecture, it is shown that smart charging of electric vehicles is able to improve the revenue of the microgrid as well. Finally, the results also show that the proposed robust operation method achieves robustness at the cost of lower revenue in non-worst scenarios.

Good or bad? Ridesharing's impact on Canadian cities

Ridesharing's phenomenal growth has been fueled by a combination of efficiency gains through technological innovation and disregard for current taxi regulations. The end effect has been the generation of significant consumer surplus, but at what social cost? This dialogue piece debates whether ridesharing services have been good or bad for Canadian cities and then reviews current regulatory status in Toronto and Vancouver.

A PSO-Optimized Fuzzy Logic Control-Based Charging Method for Individual Household Battery Storage Systems within a Community

Self-consumption of household photovoltaic (PV) storage systems has become profitable for residential owners under the trends of limited feed-in power and decreasing PV feed-in tariffs. For individual PV-storage systems, the challenge mainly lies in managing surplus generation of battery and grid power flow, ideally without relying on error-prone forecasts for both generation and consumption. Considering the large variation in power profiles of different houses in a neighborhood, the strategy is also supposed to be beneficial and applicable for the entire community. In this study, an adaptable battery charging control strategy is designed in order to obtain minimum costs for houses without any meteorological or load forecasts. Based on fuzzy logic control (FLC), battery state-of-charge (SOC) and the variation of SOC (∆SOC) are taken as input variables to dynamically determine output charging power with minimum costs. The proposed FLC-based algorithm benefits from the charging battery as much as possible during the daytime, and meanwhile properly preserves the capacity at midday when there is high possibility of curtailment loss. In addition, due to distinct power profiles in each individual house, input membership functions of FLC are improved by particle swarm optimization (PSO) to achieve better overall performance. A neighborhood with 74 houses in Germany is set up as a scenario for comparison to prior studies. Without forecasts of generation and consumption power, the proposed method leads to minimum costs in 98.6% of houses in the community, and attains the lowest average expenses for a single house each year.

Pollution, environmental taxes and public debt: A game theory setup

As is well known, public debt accumulation can produce disutility and that its accumulation over time must be economically sustainable. Equally, pollutants generated during the production process also result in disutility. One of the policy weapons available to governments in regard to public debt is the generation of primary surpluses in order to sustain a capacity to repay the debt. Affecting this capacity are the cost/benefits involved in reduction of emissions through taxation. In this paper, we address the above factors in an extremely simple, dynamic game in order to find linkages between the notions of public debt, pollution, and taxation. The starting point of the model is identification of the current account as the basis of the equation of motion of the public debt which is considered as a stock. A regulator’s task is to raise the nation’s primary surplus to reduce the stock of public debt. Nash and Stackelberg differential game solutions are used to explore the strategic interactions. For the Nash equilibrium, it is found that in establishing the cyclical strategies during the game between the polluters on the one hand and the government on the other, the discount rate of the polluters is required to be greater than the government’s discount rate. That is, polluters must be more impatient than the government. In the case of the hierarchical setting, the analytical expressions of the strategic variables and the steady state value of the public debt stock are important outcomes of this study. We find the analytical expressions of the reward functions, making the implementation by policy makers an easier task. Finally, we are able to show the conditions under which conflict is more intensive in the two cases of equilibrium, according to the shadow price of the environmental damages.

A Method for Optimal Load Dispatch of a Multi-zone Power System with Zonal Exchange Constraints

This paper presented a method for economic generation scheduling of a multi-zone power system having inter zonal operational constraints. For this purpose, the generator rescheduling for a multi area power system having inter zonal operational constraints has been represented as a two step optimal generation scheduling problem. At first, the optimal generation scheduling has been carried out for the zone having surplus or deficient generation with proper spinning reserve using co-ordination equation. The power exchange required for the deficit zones and zones having no generation are estimated based on load demand and generation for the zone. The incremental transmission loss formulas for the transmission lines participating in the power transfer process among the zones are formulated. Using these, incremental transmission loss expression in co-ordination equation, the optimal generation scheduling for the zonal exchange has been determined. Simulation is carried out on IEEE 118 bus test system to examine the applicability and validity of the method.

Identificación de ventajas y desventajas de los canales de comercialización en las economías campesinas de dos municipios de Meta y Cundinamarca, Colombia

Una de las principales funciones de la economía campesina es la producción de alimentos para autoconsumo. Esta actividad es realizada sin desmedro de la generación de excedentes para comercializar y así satisfacer otras necesidades básicas; de esta forma las familias campesinas organizan su producción. En este contexto, los campesinos buscan diferentes canales para comercializar sus productos. Para los casos estudiados, municipios de Fuente de Oro, departamento del Meta; y El Colegio, departamento de Cundinamarca, la comercialización se hace a través del Programa Mercados Campesinos, pero también por medio de otros canales fuera del Programa. Mediante la metodología ‘Circuitos de Mercados Campesinos’ se hizo acompañamiento a una familia de cada municipio, con el fin de identificar ventajas y desventajas de los canales de comercialización usados por ellos. Los hallazgos muestran que la comercialización a través de los Mercados Campesinos es la preferida, aún cuando se continúa en la búsqueda de canales propios para comercializar. La limitante más relevante que se identificó durante el proceso es el transporte, lo cual hace que el campesinado recurra a la intermediación.

Public Policy Reform and Informal Institutions: The Political Articulation of the Demand for Work in Rural India

Summary The emphasis on rights that individual citizens can claim from the state represents a significant institutional development for poverty alleviation policies. In India, important legislation was passed in 2005 to guarantee rural households 100 days of work paid at a statutory wage rate. This Right to Work legislation has enabled the implementation of the world’s largest public works program—the “Mahatma Gandhi” National Rural Employment Guarantee Scheme or NREGS. This study explores variation in policy outcomes under NREGS within a rural district of North India (Uttar Pradesh). It finds that this variation is the product of the interaction between formal and informal institutions. As such, the demand for work benefits does not emerge spontaneously from self-selecting rural citizens, but is articulated by local elected officials who are pressurised to accommodate demands for rents from the bureaucracy. Specifically, local elected officials are compelled to proceed to a selective activation of the demand for benefits to ensure the generation of a surplus which will form the basis of bureaucratic rent payments. The study relies on qualitative data, specifically interviews with past beneficiaries of the scheme, bureaucrats tasked with policy implementation, and elected village leaders (the Gram Pradhans in the Indian state of Uttar Pradesh) to document the conditions under which a surplus is extracted and rent payments made. The study shows that caste and political leadership structures at the local level affect the generation of surpluses and the payment of rents by Gram Pradhans to the bureaucracy. While the Right to Work legislation represents progress for poverty alleviation, policies such as NREGS that emphasize rights and the expression of a demand for benefits need to consider more carefully the conditions under which this demand emerges as well as the ways in which discretionary authority can thwart the goals of public policy.

Oxidative Stress: Mechanistic Insights into Inherited Mitochondrial Disorders and Parkinson's Disease.

Oxidative stress arises when cellular antioxidant defences become overwhelmed by a surplus generation of reactive oxygen species (ROS). Once this occurs, many cellular biomolecules such as DNA, lipids, and proteins become susceptible to free radical-induced oxidative damage, and this may consequently lead to cellular and ultimately tissue and organ dysfunction. Mitochondria, as well as being a source of ROS, are vulnerable to oxidative stress-induced damage with a number of key biomolecules being the target of oxidative damage by free radicals, including membrane phospholipids, respiratory chain complexes, proteins, and mitochondrial DNA (mt DNA). As a result, a deficit in cellular energy status may occur along with increased electron leakage and partial reduction of oxygen. This in turn may lead to a further increase in ROS production. Oxidative damage to certain mitochondrial biomolecules has been associated with, and implicated in the pathophysiology of a number of diseases. It is the purpose of this review to discuss the impact of such oxidative stress and subsequent damage by reviewing our current knowledge of the pathophysiology of several inherited mitochondrial disorders together with our understanding of perturbations observed in the more commonly acquired neurodegenerative disorders such as Parkinson’s disease (PD). Furthermore, the potential use and feasibility of antioxidant therapies as an adjunct to lower the accumulation of damaging oxidative species and hence slow disease progression will also be discussed.

Simultaneous co-integration of multiple electrical storage applications in a consumer setting

In a consumer setting, storage systems can be dispatched in order to shift surplus generation to periods when a local generation deficit exists. However, the high investment cost still makes the deployment of storage unattractive. As a way to overcome this problem existing literature looking at storage installed at the grid-level suggests dispatching the storage device for multiple applications simultaneously in order to access several value streams. Therefore, in this work, a Mixed Integer Linear Program is developed in order to schedule the operation of a storage device in a consumer context for multiple objectives in parallel. Besides shifting locally generated energy in time, the peak demand seen by the electric grid is reduced and the storage device is operated to provide primary reserve control. The model is applied in a case study based on the current German situation in order to illustrate the value contribution of stacking multiple services. When pursuing multiple applications simultaneously, the revenues of storage can be increased significantly. However, the revenues are not additive due to conflicting operations which originates a revenue gap as illustrated in the paper.