Dispa-SET 2.0: unit commitment and power dispatch model

In line with the Swedish target of carbon neutrality by 2045, the municipality of Växjö in Kronoberg County has set its own target to be carbon neutral in 2030. Currently, the Municipality's partially decentralized energy system relies heavily on interconnected electricity supply from the national grid, and fuels imports from other parts of Sweden. Under this circumstance, several concerns arise, including: in which ways future demand changes induce supply changes, and whether a future carbon-neutral energy system will be less costly in a sustained-electricity supply condition. In this study, techno-economic evaluations are conducted for different carbon-neutral scenarios for Växjö’s future energy system in 2030 and 2050, using an hour-by-hour dynamic energy simulation tool of EnergyPLAN. Projections for the future energy demands for Växjö were developed and modeled, based on the development strategies and on the national sustainable future scenarios in Sweden. Results for the Växjö’s carbon-neutral scenarios showed that the current energy system is sufficient to satisfy future heat demand. However, fulfilling demands of electricity for all sectors and fuels for transport and industry is a challenge. In the short term and at increased energy demand and price, being carbon neutral is technically viable without major changes in energy supply technologies. However, in the long term, investment for intermittent renewable energy resources, together with carbon capture and storage is considered to be viable financially. Therefore, planning for a carbon-neutral Växjö based on local investments showed to be a feasible strategy.

BackgroundThis paper seeks to explore the roles of distribution system operators (DSOs) in future energy systems. Measures to combat climate change have led to a transition in the energy sector, where old system fundamentals are becoming obsolete, which results in changing rules for incumbent actors, such as DSOs. These actors must uphold heavily regulated operations within their distribution networks, while landscape trends are changing with a growing number of prosumers and distributed energy resources. To understand these future roles and increase the preparedness for future scenarios and facilitate thinking beyond current lock-ins, action-oriented workshops were held with two Swedish DSOs, departing from pre-developed future imaginaries, structured through transition theory. Researchers were actively involved in the workshops, to guide the participants in the discussions and to provide additional knowledge from transition processes. This was structured through transition theory, mainly in terms of linking transition management fundamentals to the topics in the workshops and basing the workshop discussions on an imagined future socio-technical system-wide approach using four focus areas.ResultsResults included descriptions of roles within future energy systems and their connection to specified value logics from different target groups which would, from the DSO perspective, create value in a future energy system. Roles included sustainable developer, facilitator for increased collaboration, balancing actor, and communicator. In addition, competence requirements were outlined concerning the described roles. The future logic was also described in a conceptual value model for an active DSO in a prosumer-oriented energy system, creating value in all different value logics. Moreover, it provided the steps necessary to develop a pathway aimed at the transformation of DSOs.ConclusionsThe study provided a constructive approach for DSOs to prepare for a future, more prosumer-oriented and flexible energy system, avoiding being locked in current system thinking and focusing on necessary roles and competencies suitable for a DSO. In addition, the utilization of the value logics approach helped place the prosumers in a differentiated manner, which can have implications for strategies among DSOs to create the necessary relations and collaborations for an efficient and value-creating future energy system.

Introduction: To date, a variety of studies have been published on the topic of long term energy system transition. Most studies on future energy systems, however, have a shorter time frame or adopt a supranational focus (e.g. the Energy Roadmap, 2011 or the World Energy Outlook, 2015). It then constitutes a sincere challenge to perform a national energy system transition study with as time horizon 2050 and covering a far-reaching transformation of the energy system. VITO, together with the FPB (Federal Planning Bureau) and ICEDD, performed a study to scrutinise the transition of the Belgian national energy system towards a future mix entirely based on renewable energy sources. The focus on renewable energy sources and on building a national energy system completely running on renewable energy can be traced back to three main concerns: – Climate change: Renewable energy sources (RES) are a major instrument in the fight against climate change as RES do not release (net) greenhouse gas emissions. – Security...

Assuming that all electric vehicles (EVs) integrated to the grid are managed by aggregators, it is possible to make full use of the controllability of the charging EVs. Based on this, the charging load of each EV aggregator is defined as one of the optimal scheduling variables in the unit commitment (UC) model. This can be accomplished by assessing the upper and lower limit of charging load of each EV aggregator in different scenarios, which is simulated by Monte Carlo method. According to this, a UC model is proposed for optimal coordination of EV aggregators and wind generation, considering the EV owner's requirement, the range of charging load and the unit constraints. Using the10-units system as the test system, the results of UC models with different EVs charging strategies and the wind power integration indicators such as utilization rate are investigated. Simulation results show that both the abandoned wind power and the unit operating costs can be decreased more effectively in the proposed UC model.

Conceptual model of the industry sector in an energy system model: A case study for Denmark

Future highly renewable energy systems will couple to complex weather and climate dynamics. This coupling is generally not captured in detail by the open models developed in the power and energy system communities, where such open models exist. To enable modeling such a future energy system, we describe a dedicated large-scale dataset for a renewable electric power system. The dataset combines a transmission network model, as well as information for generation and demand. Generation includes conventional generators with their technical and economic characteristics, as well as weather-driven forecasts and corresponding realizations for renewable energy generation for a period of 3 years. These may be scaled according to the envisioned degrees of renewable penetration in a future European energy system. The spatial coverage, completeness and resolution of this dataset, open the door to the evaluation, scaling analysis and replicability check of a wealth of proposals in, e.g., market design, network actor coordination and forecasting of renewable power generation.

The study aims to analyze the unit commitment models and mechanisms that are used in the wholesale electricity and capacity market in Russia and other countries, as well as to consider the methods and criteria for taking into account the system security constraints in these models. The subject matter of the study includes energy systems: wholesale energy and capacity markets in Russia, the United Kingdom, EU countries, Australia, and the United States of America. In this work, various scientific information sources were collected and analytically reviewed. The study considers the performance framework of the wholesale electricity and capacity market in different countries and the main control mechanisms in solving the unit commitment problem, as well as studying and analyzing the legal and regulatory framework in solving optimization problems. It is shown that within the domestic model, the Russian Power System Operator conducts unit commitment according to the submitted price bids, taking into account the needs of the market and the energy system balance. The considered and analyzed unit commitment scheme adopted in the Russian electric power industry fails to take full account of system security, which prompts further study of this issue. The performed comparative analysis of principles underlying the performance of models and the specifics of solving unit commitment problems revealed the strengths and weaknesses in the approaches adopted in different countries both in terms of the legislation and models. The conducted analytical study helped to formulate the key points for each model that can be used to solve the unit commitment problem.

Pakistan is currently undertaking a substantial expansion of electricity generation capacity to provide electricity for all its end‐users and to satisfy a fast‐growing economy. Adoption of low‐cost, abundant and clean renewable energy will not only fulfil its growing electricity, heat, transportation and desalinated water demand but also help achieve the goals set under the Paris Agreement. A technology‐rich energy system model applied in hourly resolution has been used for investigating the transition in 5‐year periods until 2050. This study demonstrates that a 100% renewable energy system across the power, heat, transport and desalination sectors is not only technically feasible but also economically viable. Solar photovoltaics emerges as a key technology to generate electricity and contribute a share of 92% to the total primary energy demand across all sectors by 2050. The levelised cost of energy for a 100% renewable energy system is calculated as 56.1 €/MWh in 2050, lower than 70 €/MWh for the current fossil fuel‐based system. A key feature of Pakistan's future energy system is the huge increase in demand across all energy sectors, particularly for desalinated water, which is almost 19% of the final energy demand. This share of energy for desalination is among the highest in the world. Direct and indirect electrification across all demand sectors increases the efficiency of the future energy system. Moreover, GHG emissions from all the sectors will drop to zero by 2050 in a fully sustainable energy scenario.

An evaluation framework for future integrated energy systems: A whole energy systems approach

Energy security and environmental problems are important factors behind the increasing biomass consumption around the world including the lower-income countries such as Pakistan. To utilize local biomass reserves more efficiently in the context of future energy demand, the possession of knowledge about recent energy system in different sectors of the country has become interestingly important. A few initiatives and technologies are currently under process in order to move towards renewable resources from non-renewable resources and minimizing dependency on fossil fuels and reducing greenhouse gas emissions. In recent past, some ideas have been developed for sustainable biofuel production which will make sure a rapid shift from an unsustainable attitude towards a potentially sustainable approach. Hence, in this review, detailed data about the potential of biomass for the production of renewable energy in Pakistan have been presented, keeping in view the recent energy mix and future perspectives. The feasibility of local/indigenous biomass reserves and important conversion methods to transform such biomass reserves to bioenergy has also been discussed. Here, we also highlighted the drivers for consumption of local/indigenous biomass reserves in future energy system along with the challenges related to energy systems among various stakeholders. Finally, the suggestions/recommendations on the government policies and future directions for successful implementation of the energy production from local/indigenous biomass resources have been given which could be sufficient to meet increasing energy demands of Pakistan.

A Study on CO2 Emission Control in Future Energy Systems—The Role of High Temperature Nuclear Heat

The power system inertia is gradually decreasing with the growing share of variable renewable energy (VRE). This may jeopardize the frequency dynamics and challenges the secure operation of power systems. In this paper, the concept of frequency security margin is proposed to quantify the system frequency regulation ability under contingency. It is defined as the maximum power imbalance that the system can tolerate while keeping frequency within the tolerable frequency range. A frequency constrained unit commitment (FCUC) model considering frequency securitymargin is proposed. Firstly, the analytical formulation of system frequency nadir is derived while considering both the frequency regulation characteristics of the thermal generators and the frequency support from VRE plants. Then, the frequency security margin is analytically formulated and piecewise linearized. A novel FCUC model is proposed by incorporating linear frequency security constraints into the traditional unit commitment model. Case studies on a modified IEEE RTS-79 system and HRP-38 system are provided to verify the effectiveness of the proposed FCUC model. The impacts of VRE penetration on system frequency security are analyzed using frequency security margin.

Uncertainty-based unit commitment and construction in the presence of fast ramp units and energy storages as flexible resources considering enigmatic demand elasticity

Unit commitment (UC) is a problem to economically determine the commitment status and generation level for each thermal unit during each time interval of the scheduled periods. The purpose of UC is to minimize the total generation cost while satisfying system demand, reserve requirements, and other unit constraints. The combined-cycled units have been increasingly installed throughout the world because of their high efficiency and fast response. However, the combined-cycle units usually have multiple operating configurations. The multi-configuration characteristic causes that the UC problem is more complex and difficult to be solved. In this paper, the authors present a simplified combined-cycled unit model to efficiently solve the related mixed integer linear programming-based UC problem. By simulating two test systems, results show that the proposed model is effective to reduce the complexity of problem with losing little solution accuracy.

In recent years, high penetration of variable generating sources, such as wind power, has challenged independent system operators (ISO) in keeping a cheap and reliable power system operation. Any deviation between expected and real wind production must be absorbed by the power system resources (reserves), which must be available and ready to be deployed in real time. To guarantee this resource availability, the system resources must be committed in advance, usually the day-ahead, by solving the so-called unit commitment (UC) problem. If the quantity of committed resources is extremely low, there will be devastating and costly consequences in the system, such as significant load shedding. On the other hand, if this quantity is extremely high, the system operation will be excessively expensive, mainly because facilities will not be fully exploited. This thesis proposes computationally efficient models for optimal day-ahead planning in (thermal) power systems to adequately face the stochastic nature of wind production in the real-time system operation. The models can support ISOs to face the new challenges in short-term planning as uncertainty increases dramatically due to the integration of variable generating resources. This thesis then tackles the UC problem in the following aspects: Power system representation: This thesis identifies drawbacks of the traditional energy-block scheduling approach, which make it unable to adequately prepare the power system to face deterministic and perfectly known events. To overcome those drawbacks, we propose the ramp-based scheduling approach that more accurately describes the system operation, thus better exploiting the system flexibility. UC computational performance: Developing more accurate models would be pointless if these models considerably increase the computational burden of the UC problem, which is already a complex integer and non-convex problem. We then devise simultaneously tight and compact formulations under the mixed-integer programming (MIP) approach. This simultaneous characteristic reinforces the convergence speed by reducing the search space (tightness) and simultaneously increasing the searching speed (compactness) with which solvers explore that reduced space. Uncertainty management in UC: By putting together the improvements in the previous two aspects, this thesis contributes to a better management of wind uncertainty in UC, even though these two aspects are in conflict and improving one often means harming the other. If compared with a traditional energy-block UC model under the stochastic (deterministic) paradigm, a stochastic (deterministic) ramp-based UC model: 1) leads to more economic operation, due to a better and more detailed system representation, while 2) being solved significantly faster, because the core of the model is built upon simultaneously tight and compact MIP formulations. To further improve the uncertainty management in the proposed ramp-based UC, we extend the formulation to a network-constrained UC with robust reserve modelling. Based on robust optimization insights, the UC solution guarantees feasibility for any realization of the uncertain wind production, within the considered uncertainty ranges. This final model remains as a pure linear MIP problem whose size does not depend on the uncertainty representation, thus avoiding the inherent computational complications of the stochastic and robust UCs commonly found in the literature.