Browsing by Subject "Renewable energy"

Now showing 1 - 12 of 12

Open Access
Adaptive contextual learning for unit commitment in microgrids with renewable energy sources
(Institute of Electrical and Electronics Engineers, 2018) Lee, H. -S.; Tekin, Cem; van der, Schaar, M.; Lee, J. -W.
In this paper, we study a unit commitment (UC) problem where the goal is to minimize the operating costs of a microgrid that involves renewable energy sources. Since traditional UC algorithms use a priori information about uncertainties such as the load demand and the renewable power outputs, their performances highly depend on the accuracy of the a priori information, especially in microgrids due to their limited scale and size. This makes the algorithms impractical in settings where the past data are not sufficient to construct an accurate prior of the uncertainties. To resolve this issue, we develop an adaptively partitioned contextual learning algorithm for UC (AP-CLUC) that learns the best UC schedule and minimizes the total cost over time in an online manner without requiring any a priori information. AP-CLUC effectively learns the effects of the uncertainties on the cost by adaptively considering context information strongly correlated with the uncertainties, such as the past load demand and weather conditions. For AP-CLUC, we first prove an analytical bound on the performance, which shows that its average total cost converges to that of the optimal policy with perfect a priori information. Then, we show via simulations that AP-CLUC achieves competitive performance with respect to the traditional UC algorithms with perfect a priori information, and it achieves better performance than them even with small errors on the information. These results demonstrate the effectiveness of utilizing the context information and the adaptive management of the past data for the UC problem.
Open Access
Benefits of transmission switching and energy storage in power systems with high renewable energy penetration
(Elsevier, 2018) Peker, Meltem; Kocaman, Ayşe Selin; Kara, Bahar Y.
Increasing the share of renewable energy sources in electricity generation helps address concerns about carbon emissions, global warming and energy security (i.e. dependence on fossil fuels). However, integrating intermittent and variable energy sources into the grid imposes new challenges for power system reliability and stability. To use these clean sources in electricity generation without endangering power systems, utilities can implement various control mechanisms, such as energy storage systems, demand side management, renewable energy curtailment and transmission switching. This paper introduces a two-stage stochastic programming model that co-optimizes transmission switching operations, and transmission and storage investments subject to limitations on load shedding and curtailment amounts. We discuss the effect of transmission switching on the total investment and operational costs, siting and sizing decisions of energy storage systems, and load shedding and renewable energy curtailment in a power system with high renewable penetration. An extensive computational study on the IEEE 24-bus power system with wind and solar as available renewable sources demonstrates that the total cost and total capacity of energy storage systems can be decreased up to 17% and 50%, respectively, when transmission switching is incorporated into the power system.
Open Access
Bi‐objective optimization of a grid‐connected decentralized energy system
(John Wiley and Sons, 2018) Altıntaş, Onur; Ökten, Büşra; Karsu, Özlem; Kocaman, Ayşe Selin
Motivated by the increasing transition from fossil fuel-based centralized systems to renewable energy-based decentralized systems, we consider a bi-objective investment planning problem of a grid-connected decentralized hybrid renewable energy system. In this system, solar and wind are the main electricity generation resources. A national grid is assumed to be a carbon-intense alternative to the renewables and is used as a backup source to ensure reliability. We consider both total cost and carbon emissions caused by electricity purchased from the grid. We first discuss a novel simulation-optimization algorithm and then adapt multi-objective metaheuristic algorithms. We integrate a simulation module to these algorithms to handle the stochastic nature of this bi-objective problem. We perform extensive comparative analysis for the solution approaches and report their performances in terms of solution time and quality based on well-known measures from the literature.
Open Access
Contextual learning for unit commitment with renewable energy sources
(IEEE, 2017) Lee, H. -S.; Tekin, Cem; Schaar, M.; Lee, J. -W.
In this paper, we study a unit commitment (UC) problem minimizing operating costs of the power system with renewable energy sources. We develop a contextual learning algorithm for UC (CLUC) which learns which UC schedule to choose based on the context information such as past load demand and weather condition. CLUC does not require any prior knowledge on the uncertainties such as the load demand and the renewable power outputs, and learns them over time using the context information. We characterize the performance of CLUC analytically, and prove its optimality in terms of the long-term average cost. Through the simulation results, we show the performance of CLUC and the effectiveness of utilizing the context information in the UC problem.
Open Access
Energy operations management for renewable power producers in electricity markets
(2023-05) Karakoyun, Ece Çiğdem
Renewable energy generation has grown dramatically around the world in recent years, and policies targeted at reducing greenhouse gas emissions that cause global warming are expected to ensure a consistent expansion of renewable power generation in the electricity sector. With the increasing contribution of renewable sources to the overall energy supply, renewable power producers participate in electricity markets where they are imposed to make advance commitment decisions for energy delivery and purchase. Making advance commitments, however, is a complex task due to the inherent intermittency of renewable sources, increasingly volatile electricity prices, and penalties incurred for possible energy imbalances in electricity markets. Integrating renewable sources with energy storage units is among the most effective methods to address this challenging task. Motivated by the recent trends of paired renewable energy generators and storage units, we study the energy commitment, generation and storage problem of a wind power producer who owns a battery and participates in a spot market operating with hourly commitments and settlements. In each time period, the producer decides how much energy to commit to selling to or purchasing from the market in the next time period, how much energy to generate in the wind power plant, and how much energy to charge into or discharge from the battery. The existence of the battery not only helps smooth out imbalances caused by the fluctuating wind output but also enables the producer to respond to price changes in the market. We formulate the wind power producer's problem as a Markov decision process by taking into account the uncertainties in wind speed and electricity price. In the first part of this dissertation, we consider two different problem settings: In the first setting, the producer may choose to deviate from her commitments based on the latest available information, using the battery to support such deviations. In the second setting, the producer is required to fulfill her commitments, using the battery as a back-up source. We numerically examine the effects of system components, imbalance pricing parameters, and negative prices on the producer's profits, curtailment decisions, and imbalance tendencies in each problem setting. We provide managerial insights to renewable power producers in their assessment of energy storage adoption decisions and to power system operators in their understanding of the producers' behavior in the market with their storage capabilities. In the second part of this dissertation, we establish several multi-dimensional structural properties of the optimal profit function such as supermodularity and joint concavity. This enables us to prove the optimality of a state-dependent threshold policy for the storage and commitment decisions under the assumptions of a perfectly efficient system and positive electricity prices. Leveraging this policy structure, we construct two heuristic solution methods for solving the more general problem in which the battery and transmission line can be imperfectly efficient and the price can also be negative. Numerical experiments with data-calibrated instances have revealed the high efficiency and scalability of our solution procedure. In the third part of this dissertation, we characterize the optimal policy structure by taking into account the battery and transmission line efficiency losses and showing the joint concavity of the optimal profit function. In the last part of this dissertation, we consider an alternative problem setting that allows for real-time trading without making any advance commitment. We analytically compare the total cash flows of this setting to those of our original problem setting. We conclude with a numerical investigation of the effect of advance commitment decisions on the producer's energy storage and generation decisions.
Restricted
Enerji ve değişim: TEK’ten EPDK’ye Türkiye’nin elektrik piyasasındaki dönüşüm
(Bilkent University, 2025) Kızıloğlu, Lütfü Heysem; Anbar, Emin Mete; Tekeli, Eser Tekin; Akdaş, Aybala; Yüksel, Arda; Erdem, Sıla Yağmur
Bu çalışma, TEK ve EPDK dönemlerinin karşılaştırılması ile enerji sektörünün gelişim ve dönüşüm süreçlerini ele alacaktır. Türkiye Elektrik Kurumu (TEK), 1970 yılında kurulmuş ve 1994 yılında kapanana kadar Türkiye’de elektrik üretim, iletim ve dağıtım faaliyetlerini birleştirmeyi hedeflemiş olan bir kamu kurumudur. Ayrıca TEK, kırsal elektrifikasyon projeleri ile ülkenin kırsal bölgelerine elektrik enerjisi ulaştırmayı amaçlamıştır. Ancak, bürokratik sorunlar ve ekonomik krizler kurumun başarısını olumsuz etkilemiştir. 2001 yılında yürürlüğe giren 4628 sayılı Elektrik Piyasası Kanunu ile enerji sektöründe serbestleşme ve özelleşme süreci başlamış, Enerji Piyasası Düzenleme Kurumu’nun (EPDK) kurulmasıyla özelleşme süreci ivme kazanmıştır. Bahsi geçen reformlar, yenilenebilir enerji projelerinde ilerleme ve kaynak oluşumuna katkıda bulunmuş olsa da, yüksek fiyatlanma ve bölgesel dalgalanmalar gibi sorunlara yol açmıştır.
Open Access
How science communication delivers meaningful frameworks about Industry 4.0 to the public sphere
(Springer Science and Business Media Deutschland GmbH, 2020) Becerir, Murat Can; Peschke, Lutz; Durakbasa, N.; Gençyılmaz, M.
With the emergence of new media and interactive media technologies, the mediatized transformative process began. Specifically within the science communication context, the way we perceive issues transformed drastically. With the mediatization of forms of understanding and literacy, the public perception towards many topics, including environmental sciences has gained recognition. This research paper will be focusing on the connection between Industry 4.0 and science communication. By making a valuable contribution to the communication process through constructing a bridge between the industry and the general public, science communication provides a smooth and effective transition of mutually beneficial relationships. This paper concentrates upon the notion of sustainability and its relevance to the industrial revolution, which is also known as Industry 4.0. The paper will be exploring the ways in which how humanity can stay within the safe operating limits with the existing technology and resources. By taking into consideration the notion of sustainability, the paper will attempt to discover possible ways that how people can construct their discourse on the big framework where everything is interconnected to one another. By meaning, Industry 4.0 indicates the connection between automation, computers, smart technologies and the cloud system in which the flow of information has increased in unprecedented levels. Since Industry 4.0 is already happening and has an immense impact on our lives, science communication plays a big part in generating the accessible and relatable message of the implications regarding the age of Industry 4.0. From the automobile industry to the electronic products that we use every day, the majority of the markets use renewable energy in order to lower the costs of production and increase their profits. A disruption in the sustainable development of any given society may cause irreparable damages which can result in colossal economic and political instability. Hence, science communication plays a vital role in terms of providing an understanding of possible pros and cons regarding the practices of the industrialists and the business world. Since it can be quite hard to comprehend the full scale of the consequences of technical occupations and practices, science communication will be the vanguard in terms of constructing a meaningful framework for the general society. This paper will explore what might happen in the lack of understanding of sustainability in Industry 4.0 through renewable energy consumption. Particularly, how a situation looks like when a country experiences a huge setback for its economy, massive loss of life and property in an unsettled global economy. What kind of a scenario would people witness with a disruption in one part of the world, in a world of interconnected production of supply chains that stretch across the world? Therefore, this paper will explore the possible implications of Industry 4.0 through renewable energy consumption on a grand scale.
Open Access
Optimization of hybrid energy systems with pumped hydro storage: a case study for Turkey
(Gazi Üniversitesi Mühendislik-Mimarlık, 2019) Kocaman, Ayşe Selin
There is a need for energy models that include renewable energy sources to reduce the role of fossil fuels in electricity generation. However, renewable energy sources are intermittent and cannot be predicted precisely. Designing hybrid systems that combine alternative resources and energy storage helps reduce the intermittency of renewable sources and result in cost effective and reliable solutions. The most widely used energy storage form in the World is to store the potential energy of water in the pumped hydroelectricity systems (PHES). Pumped hydroelectricity systems can be designed in two types: mixed systems, if there is a natural water inflow to the system and pure systems, if the system is closed to water inflow. In this study, we present two-stage stochastic programming models for both types of PHES, which take into account the uncertainty of resources and electricity demand. For the first time in the literature, we consider the sizing problem of hybrid systems that include solar generation supported by pure and mixed PHES systems separately and present the results for Turkey, which currently does not have any PHES system and highly depends on fossil fuels for electricity generation, despite of the rich renewable energy potential.
Open Access
Renewable energy system design and operational planning for demand fulfillment
(2024-08) Yurter, Gülin
Renewable energy sources have gained prominence in reducing the dependency on fossil fuels and minimizing their negative environmental impacts. Considering renewables' uncertain and variable nature, an effective design and operational planning of hybrid energy systems is key to success in clean energy transition. We study the optimal design and operational planning problem of hybrid energy systems involving a renewable energy source and a storage unit. We first develop two-stage stochastic mixed-integer programming models to determine the optimal sizing and investment decisions for solar/wind farms co-operated with pumped hydro energy storage facilities in decentralized areas. We then utilize a Markov decision process to find the optimal energy generation and storage decisions for decentralized grid-connected wind farm-battery systems with demand-fulfillment obligations. This is a novel study that compares several pumped hydro energy storage configurations with respect to optimal sizing decisions for system components and allows for uncertainties in electricity price, wind speed, and electricity demand for optimal operational planning. Using real-life data and considering economic benefits, we demonstrate how the renewable energy systems should be designed and managed to mitigate the adverse effects of uncertainties in matching supply with demand.
Embargo
The impact of pumped hydro energy storage configurations on investment planning of hybrid systems with renewables
(Elsevier Ltd, 2024-02) Yurter, Gülin; Nadar, Emre; Kocaman, Ayşe Selin
The pumped hydro energy storage (PHES) systems can be installed in various configurations depending on the specific geographical and hydrological conditions. Closed-loop PHES systems are off-stream and have no natural inflow to the system. However, open-loop systems are on-stream and have natural inflows to the upper and/or lower reservoirs. In this study, we develop two-stage stochastic programming models for various PHES configurations to investigate how the choice of PHES configuration impacts the sizing decisions and costs of a hybrid system that includes a renewable power generator co-operated with PHES. Our numerical results show that using a PHES facility instead of a conventional hydropower system reduces the expected system cost and mismatched demand significantly. Open-loop PHES facilities perform better than closed-loop PHES and seawater-PHES facilities, dramatically lowering the need for fossil fuels in demand fulfillment. The most cost-efficient PHES configuration is when there is natural inflow to the upper reservoir. Using solar energy instead of wind as the renewable source significantly increases the requirement for larger upper reservoirs in on-stream open-loop PHES facilities, while reducing the expected system cost for all configurations.
Restricted
üzerinde güneş batmayan enstitü: Güneş Enerjisi Enstitüsü
(Bilkent University, 2018) Özbakır, Ayşe Beyza; Aydemir, Beste; Özyedek, Ege Ozan; Altınel, Gül Neslihan; Ertuğrul, Mert
Bu makalede 1978 yılında faaliyete geçen Ege üniversitesi Güneş Enerjisi Enstitüsü incelenmiştir. 1970’lerde yaşanan petrol krizinin dünyada yarattığı etki ve krizin Türkiye’deki sonuçları üzerinde durulmuştur. Krizin yenilenebilir enerjiye yönelimi nasıl etkilediğinden bahsedilmiştir ve enstitünün kuruluşunda sahip olmuş olabileceği etki incelenmiştir. Enstitünün kuruluş aşaması ve erken dönem çalışmaları açıklanmıştır. Devlet ile enstitü arasındaki ilişki ve 1980 – 2018 yılları arasında Türkiye’de hükümetlerin yenilenebilir enerji politikası incelenmiştir. Enstitünün Türkiye içindeki çalışmaları ve uluslararası çalışmalardaki rolü araştırılmıştır. incelenmiştir. 1970’lerde yaşanan petrol krizinin dünyada yarattığı etki ve krizin Türkiye’deki sonuçları üzerinde durulmuştur. Krizin yenilenebilir enerjiye yönelimi nasıl etkilediğinden bahsedilmiştir ve enstitünün kuruluşunda sahip olmuş olabileceği etki incelenmiştir. Enstitünün kuruluş aşaması ve erken dönem çalışmaları açıklanmıştır. Devlet ile enstitü arasındaki ilişki ve 1980 – 2018 yılları arasında Türkiye’de hükümetlerin yenilenebilir enerji politikası incelenmiştir. Enstitünün Türkiye içindeki çalışmaları ve uluslararası çalışmalardaki rolü araştırılmıştır.
Open Access
What is the role of renewable energy resources in terms of state's acts seeking power or security in international order for China?
(2021-02) Kurt, Furkan Vefa
This thesis focuses on renewable energy development in China to examine how China has increased renewable energy production and consumption. Government role in renewable development, supporting policies, and the process of energy transition through the increasing importance of renewable energy resources in the world energy market and China are presented. Chinese renewable firms are also assessed in terms of their roles in renewable energy and related sectors. The findings of the study are discussed according to the basic arguments of realism for future research on whether China’s energy transition increases its power and expands its capabilities in global scale.