| 1. |
- Abdallah, Mohammed, et al.
(författare)
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Daily global solar radiation time series prediction using variational mode decomposition combined with multi-functional recurrent fuzzy neural network and quantile regression forests algorithm
- 2023
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Ingår i: Energy Reports. - 2352-4847. ; 10, s. 4198-4217
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Tidskriftsartikel (refereegranskat)abstract
- Global solar radiation (GSR) prediction capability with a reliable model and high accuracy is crucial for comprehending hydrological and meteorological systems. It is vital for the production of renewable and clean energy. This research aims to evaluate the performance of combined variational mode decomposition (VMD) with a multi-functional recurrent fuzzy neural network (MFRFNN) and quantile regression forests (QRF) models for GSR prediction in daily scales. The hybrid VMD-MFRFNN and QRF models were compared with standalone MFRFNN, random forest (RF), extreme gradient boosting (XGB), and M5 tree (M5T) models across the Lund and Växjö meteorological stations in Sweden. The meteorological data from 2008 to 2017 were used to train the models, while the prediction accuracy was verified by using the data from 2018 to 2021 under five different input combinations. The various meteorological-based scenarios (including the input are air temperatures (Tmin, Tmax, T), wind speed (WS), relative humidity (RH), sunshine duration (SSH), and maximum possible sunshine duration (N)) were considered as input of predictor models. The current study resulted that the M5T model exhibited higher accuracy than RF and XGB models, while the QRF model showed equivalent performance with the M5T model at both study sites. The MFRFNN model outperformed QRF and M5T models across all input combinations at both study sites. The hybrid VMD-MFRFNN model showed the best performance when fewer input variables (Tmin, Tmax, T, WS at Lund station and Tmin, Tmax, T, WS, SSH, RH at Växjö station) were used for GSR prediction. We conclude that the MFRFNN model best predicts average daily GSR when combining all meteorological variables (Tmin, Tmax, T, WS, SSH, RH, N).
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| 2. |
- Abugabbara, Marwan, et al.
(författare)
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How to develop fifth-generation district heating and cooling in Sweden? : Application review and best practices proposed by middle agents
- 2023
-
Ingår i: Energy Reports. - : Elsevier Ltd. - 2352-4847. ; 9, s. 4971-4983
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Tidskriftsartikel (refereegranskat)abstract
- Sweden has an ambitious plan to fully decarbonise district heating by 2030 and to contribute with negative emissions of greenhouse gases in 2050. The vagaries of the energy market associated with climate, political, and social changes entail cross-sectoral integration that can fulfill these national targets. Fifth-generation district heating and cooling (5GDHC) is a relatively new concept of district energy systems that features a simultaneous supply of heating and cooling using power-to-heat technologies. This paper presents best practices for developing 5GDHC systems in Sweden to reach a consensus view on these systems among all stakeholders. A mixed-method combining best practice and roadmapping workshops has been used to disseminate mixed knowledge and experience from middle agents representing industry professionals and practitioners. Four successful implementations of 5GDHC systems are demonstrated and the important learned lessons are shared. The best practices are outlined for system planning, system modeling and simulation, prevailing business models for energy communities, and system monitoring. A roadmap from the middle agents’ point of view is composed and can be utilised to establish industry standards and common regulatory frameworks. © 2023 The Author(s)
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| 3. |
- Abugabbara, Marwan, et al.
(författare)
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Modelica-based simulations of decentralised substations to support decarbonisation of district heating and cooling
- 2021
-
Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 7:4, s. 465-472
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Tidskriftsartikel (refereegranskat)abstract
- District heating and cooling are considered effective solutions to decarbonise the energy use in the building sector. The latest generation of district heating and cooling also increases the potential of integrating heat pumps and chillers in each building substation. The benefits of such integration are the reduction of network temperature and distribution losses; the recovery of waste heat through a bidirectional network; and the decentralised production of heating and cooling. Sizing the network depends mainly on the heat flows between connected buildings. The substation performance and technical installations determine these heat flows. We present in this paper Modelica-based simulations of two design cases for substations. The first design case involves installed heat pump, chiller, and circulation pumps. Alternatively, the second design enables the heat pump to provide direct cooling through a heat exchanger. The models for these installations were developed using the Modelica language to perform continuous-time simulations. The performance in each design case was evaluated in terms of seasonal coefficient of performance and total electric energy use. An analysis on a cluster of 11 buildings suggests that the addition of the direct cooling heat exchanger can save up to 10% of the total annual electric energy use. Additional savings can be achieved by optimising the building supply temperatures and the district network temperature.
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| 4. |
- Agar, David, et al.
(författare)
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Combining behavioural TOPSIS and six multi-criteria weighting methods to rank biomass fuel pellets for energy use in Sweden
- 2023
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Ingår i: Energy Reports. - 2352-4847. ; 10, s. 706-718
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Tidskriftsartikel (refereegranskat)abstract
- EU energy and climate policies continue to drive interest in biomass fuel pellets which can be produced from a wide variety of feedstock. The use of multi-criteria decision analysis (MCDA) to support feedstock selection has the potential for more transparent and better decision-making. This study applies the behavioural TOPSIS, a prominent MCDA technique, to rank pellets for energy use in Sweden produced from under-utilised forest and agricultural biomass. Seven criteria were used to assess and rank the biomass pellets. The alternatives include 88 types of pellets from 11 biomass materials. Possible attitudes of an expert towards the risk of losses (risk averse, risk neutral and risk-seeking) were combined with six sets of criteria weights obtained using six weighting methods – a total of 18 input settings (scenarios). Despite having different input settings, almost identical results were obtained in all scenarios, meaning that the rankings were stable and consistent. Across all 18 scenarios, pellets produced from a reference spruce/pine sawdust blend are ranked ahead of other pellet types. Pellets produced from Scots pine bark exhibited stable and consistent rankings across all scenarios; and thus this biomass is the second-best overall. The next best materials overall are poplar, reed canary grass and wheat straw, whereas torrefied pellets (torrefied beech, poplar and wheat straw) were ranked last in all scenarios. Combining behavioural TOPSIS and a variety of criteria-weighting methods is a meaningful way of improving decision-making with respect to producing a more valid and reliable ranking of biomass fuel pellets for energy use in Sweden.
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| 5. |
- Agyekum, Ephraim Bonah, et al.
(författare)
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Towards a reduction of emissions and cost-savings in homes: Techno-economic and environmental impact of two different solar water heaters
- 2024
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Ingår i: Energy Reports. - : ELSEVIER. - 2352-4847. ; 11, s. 963-981
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Tidskriftsartikel (refereegranskat)abstract
- South Africa currently has the highest carbon emission intensity per kilowatt of electricity generation globally, and its government intends to reduce it. Some of the measures taken by the government include a reduction of emissions in the building sector using solar water heating (SWH) systems. However, there is currently no study in the country that comprehensively assesses the technical, economic, and environmental impact of SWH systems across the country. This study therefore used the System Advisor Model (SAM) to model two different technologies of SWH systems (i.e., flat plate (FPC) and evacuated tube (EPC) SWH) at five different locations (i.e., Pretoria, Upington, Kimberley, Durban, and Cape Town) strategically selected across the country. According to the study, the optimum azimuth for both the evacuated tube and flat plate SWH system in South Africa is 0 degrees. Installing FPC and EPC at the different locations would yield payback periods of 3.2 to 4.4 years and 3.5 to 4.3 years, respectively. Comparably, levelized cost of energy for the FPC and EPC will range from 7.47 to 9.62 cents/kWh and 7.66 to 9.24 cents/kWh, respectively, based on where the SWH system is located. Depending on where the facility is located, the annual cost savings for the FPC system would be between $486 and $625, while the EPC system would save between $529 and $638. Using SWHs can reduce CO2 emissions by 75-77% for the evacuated tube system and 69-76% for the flat plate system annually, depending on the location.
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| 6. |
- Al-Sulttani, Ali Omran, et al.
(författare)
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Thermal effectiveness of solar collector using Graphene nanostructures suspended in ethylene glycol–water mixtures
- 2022
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Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 8, s. 1867-1882
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Tidskriftsartikel (refereegranskat)abstract
- Flat plate solar collectors (FPSCs) are the most often used as solar collectors due to their easiness of installation and usage. The current research investigates the energy efficiency of FPSC using different mass concentration with varied base fluids containing Graphene nanofluids (T-Gr). Mass concentration of 0.1%-wt., 0.075%-wt., 0.050%-wt. and 0.025%-wt. were mixed with ethylene glycol (EG) and distilled water (DW) in different rations. The operating conditions were volumetric flowrate (1.5, 1 and 0.5) LPM 50 °C-input fluid temperature and 800 W/m2-global solar irradiation. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) were used to synthesize the thermally treated nanomaterial. The theoretical investigation indicated that using T-Gr nanosuspensions increased the FPSC efficiency in comparison with the host fluid for all examined mass concentrations and volumetric flowrates. In quantitative terms, the maximum thermal effectiveness improvement for the EG, (DW:70 + EG:30) and DW:EG (DW:50 + EG:50) and using flowrates of (1.5, 1 and 0.5) LPM were 12.54%, 12.46% and 12.48%. In addition, the research results pointed that the essential parameters (i.e., loss energy (FRUL)) and gain energy (FR (τα)) of the T-Gr nanofluids were increased significantly.
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| 7. |
- Andersson, Elias, 1989-, et al.
(författare)
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Decarbonization of industry : Implementation of energy performance indicators for successful energy management practices in kraft pulp mills
- 2021
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 7, s. 1808-1817
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Tidskriftsartikel (refereegranskat)abstract
- Energy management is the most prominent means of improving energy efficiency, and improved energy efficiency constitutes the cornerstone in decarbonization. For successful industrial energy management, defining accurate energy performance indicators (EnPIs) is essential. Energy-intensive industries have previously been found to have an improvement potential regarding the current monitoring of EnPIs, especially at process level. While general models for developing and implementing EnPIs exist, manufacturing industries are diverse in terms of their production processes, which is why industry-tailored models for EnPI development are needed. One major outcome of this paper is a unique model specifically tailored for kraft pulp mills. The model derives from a practice-based approach for EnPI development, building on real-life experiences from a Swedish group of companies. This paper’s developed model, and the validation of the EnPIs, further increase the understanding of the kraft pulp industry’s processes and how to apply descriptive and explanatory indicators. The developed model can potentially be generalized to other sectors.
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| 8. |
- Andrei, Mariana, et al.
(författare)
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Decarbonization of industry : Guidelines towards a harmonized energy efficiency policy program impact evaluation methodology
- 2021
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 7, s. 1385-1395
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Tidskriftsartikel (refereegranskat)abstract
- The decarbonization of EU energy system is under way, but manufacturing industry is still using approximately 25% of the EU total final energy use. To maintain long-term competitiveness while contributing to the EU goal of carbon neutrality by 2050, manufacturing industry needs to improve energy efficiency in a cost-effective way. One important way to achieve this is through energy audits. The Energy Efficiency Directive promotes member states development of energy efficiency programs to encourage industry to undergo energy audits. Previous studies have reviewed industrial energy efficiency policy program evaluations and argued that there is no harmonized way to conduct them. This leads to difficulties in: i) comparing energy efficiency and cost saving potentials throughout different programs, and ii) providing necessary information that supports the improvement of the policy program. Therefore, we argue that a harmonized methodology for industrial energy efficiency policy program evaluation is of great importance, and, we have developed a set of five-steps guidelines that lay the foundation for an ex-ante energy efficiency policy program evaluation methodology. The guidelines are to be be conducted during the lifetime of the program, in five steps, as follows: (s1) define key issues, (s2) set the objectives for each key issue, (s3) identify the options for each key issue, (s4) analyze options from an energy and environmental perspective, and (s5) compare options and select the recommended one. Our proposed methodology will support policymakers and evaluators answer questions such as: i) how can the objectives of the policy program be achieved? ii) is there any need to change the policy program? Furthermore, a comparison in terms of relevance, efficiency, effectiveness, and sustainability of all major policy options developed, including the status quo option is proposed in the methodology. This paper can be seen an important step towards the goal of creating a harmonized policy evaluation methodology. (C) 2021 The Authors. Published by Elsevier Ltd.
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| 9. |
- Andrei, Mariana, 1981-, et al.
(författare)
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Exploring the design of voluntary initiatives from the transition management perspective – A means for industrial decarbonization
- 2024
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Ingår i: Energy Reports. - : ELSEVIER. - 2352-4847. ; 11, s. 5894-5909
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies claim that national policies fall short of the ambitious goal to limit global temperature increase to well below 2°C, preferably 1.5°C, revealing an ambition gap between current commitments and those needed to reach climate neutrality. To bridge this gap, commitments must increase more than fivefold to achieve the necessary reduction in GHG emissions. Voluntary initiatives (VIs), gaining interest as an approach to support the Paris Agreement's ambition, have the potential to bridge the commitment gap and limit the expected temperature increase to 2°C if all their voluntary commitments to climate neutrality are fulfilled. While decarbonizing the manufacturing sector is crucial for climate targets, no prior study has explored the theoretical potential of industry-related VIs to bridge the gap for industrial decarbonization. This paper addresses this gap by examining the potential contribution of these VIs, analyzing criteria related to arena and agenda creation, operationalization, and accountability. By applying the transition management framework innovatively, the study investigates eighty-three industry-related VIs led by both state and non-state actors. The research process, involving the development of an analytical framework, VIs selection, data collection and validation, categorization, and analysis, provides insights into how the design affects VIs' potential for industrial decarbonization. The main findings highlight, firstly, the need for clearly defined and measurable targets, enhanced commitments, and robust accountability mechanisms, especially for non-state actor-led initiatives. Secondly, increased participation from energy-intensive sector companies due to their pivotal role for GHG emission reduction. Lastly, collaboration between state and non-state actors is critical for bridging the decarbonization gap in manufacturing industries. Additionally, the similarity between VIs and voluntary agreement programs (VAPs) is highlighted, with VAPs been overseen by governmental bodies with administrative authority. Given the urgency of addressing climate change, an unanswered question remains: Will future policies transition away from voluntariness towards more mandatory administrative character?
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| 10. |
- Asim, Muhammad, et al.
(författare)
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Techno-economic assessment of energy and environmental impact of waste-to-energy electricity generation
- 2023
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 9:Suppl 1, s. 1087-1097
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Tidskriftsartikel (refereegranskat)abstract
- This study explored cumulative 127.5MW waste to energy (WtE) potential in five populous cities of Pakistan based on local waste characterization profiles and global standards. The 50MW WtE plant in Lahore using National electricity regulator codes and practices resulted in an attractive Levelized cost of electricity (LCOE) of US¢ 7.86/kWh over 25 years with a $151.5 million investment cost. The net savings to Lahore Waste Management Company can be $103.4 and $137.7 million respectively with and without tipping fees on account of waste disposal cost, bricks revenue using bottom ash, and waste fee. The project developers can get net savings of $16.9 and $51.5 million respectively with and without tipping fees other than LCOE. Furthermore, the greenhouse gas emissions of 216.6 million tons of CO2eq can be saved throughout plant life against 279 GWh/year energy generation, in terms of grid emission factor and current methane release into the atmosphere from the dumping site.
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| 11. |
- Averfalk, Helge, 1988-, et al.
(författare)
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Domestic hot water design and flow measurements
- 2021
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Ingår i: Energy Reports. - Amsterdam : Elsevier. - 2352-4847. ; 7:Suppl. 4, s. 304-310
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the sizing of primary side components for preparation of domestic hot water are analysed, both qualitatively and based on measurements of domestic hot water demand in one multi-family building with 268 apartments. The collected data spans a period of 18 days during the end of 2020 and is collected in 15-min, 1-min, and 6-s intervals. An overview of the historic development for the design of domestic hot water flow in Sweden is also presented. There is a long-standing argument in Sweden, that the current district heating guidelines result in an overdesign of the flow for domestic hot water. The consequence of this is oversizing heat exchangers and valves in the substations. This study assesses, qualitatively, the issues related to overdesigned primary side valves for preparation of domestic hot water. A revised design for domestic hot water flow for the Swedish context is also conceptualised. The study suggests that an improved design flow for domestic hot water in multi-family buildings can be derived based on empirical measurements. The 15-min intervals are observed to tone down information of peaks to a degree where it is unsuitable to use as basis for a new design flow. The 1-min data does appear to preserve information to a degree where it can be used to assess a design flow when related to data with a 6-s interval. The 6-s data is expected to constitute a resolution that may be less available, and in this study, it constitutes a representation of the real domestic hot water demands. However, to find a fitted curve to empirical data, for the design flow based on number of apartments per multi-family building, the population of datasets needs to be increased. © 2021 The Authors. Published by Elsevier Ltd.
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| 12. |
- Bahaghighat, Mahdi, et al.
(författare)
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Using machine learning and computer vision to estimate the angular velocity of wind turbines in smart grids remotely
- 2021
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 7, s. 8561-8576
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Tidskriftsartikel (refereegranskat)abstract
- Today, power generation from clean and renewable resources such as wind and solar is of great salience. Smart grid technology efficiently responds to the increasing demand for electric power. Intelligent monitoring, control, and maintenance of wind energy facilities are indispensable to increase the performance and efficiency of smart grids (SGs). Integration of state-of-the-art machine learning algorithms and vision sensor networks approaches pave the way toward enhancing the wind farms performance. The generating power in a wind turbine farm is the most critical parameter that should be measured accurately. Produced power is highly related to weather patterns, and a new farm in a near area is also likely to have similar energy generation. Therefore, accurate and perpetual prediction models of the existing wind farms can be led to develop new stations with lower costs. The paper aims to estimate the angular velocity of turbine blades using vision sensors and signal processing. The high wind in the wind farm can cause the camera to vibrate in successive frames, and the noise in the input images can also strengthen the problem. Thanks to couples of solid computer vision algorithms, including FAST (Features from Accelerated Segment Test), SIFT (Scale-Invariant Feature Transform), SURF (Speeded Up Robust Features), BF (Brute-Force), FLANN (Fast Library for Approximate Nearest Neighbors), AE (Autoencoder), and SVM (support vector machines), this paper accurately localizes the Hub and track the presence of the Blade in consecutive frames of a video stream. The simulation results show that determining the hub location and the blade presence in sequential frames results in an accurate estimation of wind turbine angular velocity with 95.36% accuracy. (C) 2021 The Authors. Published by Elsevier Ltd.
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| 13. |
- Bhattacharjee, Shimantika, et al.
(författare)
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Energy and indoor thermal performance analysis of a glazed façade high-rise building under various Nordic climatic conditions
- 2023
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 10, s. 3039-3053
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Tidskriftsartikel (refereegranskat)abstract
- Research has shown that glazed buildings can have higher energy use and are more prone to overheating than other types of buildings. However, few studies have explored the performance of glazed buildings in cold climates. This article aims to evaluate the energy and indoor thermal performance of a high-rise residential building with glazed façades and balconies under Nordic climatic conditions, through a parametric study. Dynamic, whole-year simulations are used to evaluate the impact of four design parameters (with and without glazed balconies, type of balcony glazing, window to wall ratio, and building location within the Nordic region) on the energy and indoor thermal performance of the building. The results show that the building without glazed balconies outperformed that with glazed balconies. Changing from single- to double-pane glazing also helped to reduce energy use and overheating, as did lowering the window-to-wall ratio. Overheating of apartments was found to occur during the summer in five of the six locations simulated, which suggests that solar control strategies might be needed for glazed buildings even in a Nordic climate. This study highlights the importance of further research on glazed residential buildings, which are becoming more common in contexts subject to such climates.
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| 14. |
- Blomqvist, Stefan, 1988-, et al.
(författare)
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Ten years of energy efficiency—Exploring the progress of barriers and drivers in the swedish residential and services sector
- 2022
-
Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 8, s. 14726-14740
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Tidskriftsartikel (refereegranskat)abstract
- Making buildings more energy efficient is an important part of achieving the European Union's energy and climate goals, which several directives, policies, and measures has addressed over the years. This paper aims to study changes over a 10-year period in perception on barriers to and drivers for energy efficiency in the Swedish building sector and identifying success factors. The data collection consists of surveys conducted in 2010 and 2020 among organizations that mainly build, own, and manage multi-dwelling buildings. Besides the overall result, special focus is given to changes depending on type of ownership, size of organization, and organizational hierarchy. Lack of time or other priorities and slim organizations remain the most important barriers, which is most evident among small organizations. Reducing cost remains the major driver. The uncertainty surrounding a rising energy price has diminished and cost-effective solutions are more adaptable. More capital for energy efficiency is available, particularly in the private sector. Furthermore, the result acknowledges the impact of regulatory measures. The study recognizes a connection between organizational development and the integration of energy efficiency in an organizations’ agenda. Future challenges are related to hidden costs and knowledge acquisition.
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| 15. |
- Cabral, Diogo, PhD, 1990-, et al.
(författare)
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Parametric comparison of a CPVT performance evaluation under standard testing procedures - ISO 9806:2017 and IEC 62108:2016 - for an automated and manual 2-axis tracking solar system stand
- 2024
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 11, s. 1242-1255
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Tidskriftsartikel (refereegranskat)abstract
- Currently, a noticeable lack of literature with respect to a wide-ranging comparison of the precision exhibited by automated and manual two-axis tracking solar systems, particularly within the context of adhering to the standard testing protocols delineated by ISO and IEC. To address this research gap, a symmetrical concentrating Photovoltaic-Thermal solar collector underwent a detailed evaluation encompassing two standard testing procedures such as ISO 9806:2017 and IEC 62108:2016. This comprehensive assessment covered thermal and electrical performance parameters, unfolding across two distinct geographical locations: Athens (Greece) and Gävle (Sweden). Within this experimental framework, an automated two-axis tracking solar system stand was employed at the Greek testing site, while in Sweden it was characterized by the employment of a manual two-axis tracking solar system. The collective peak power performance presented marginal divergence within a narrow range of ± 1% across both testing sites. This culminated in an overall peak power output of 1550 Wpeak, which included an electrical peak capacity of 218 Wpeak and a thermal peak power of approximately 1332 Wpeak. Notably, the most pronounced deviation has been materialized in the transversal and longitudinal Incidence Angle Modifier coefficients, with disparities remaining limited to a threshold of < 5%. These findings underscore the commendable precision hallmarking. In summary, the outcomes presented in this study not only contribute to the extant body of knowledge by bridging the existing gap in literature, but also emphasize the precision inherent to manual two-axis tracking solar systems when compared with automated equivalents.
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| 16. |
- Çelik, Onur, et al.
(författare)
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Consumer purchasing behavior and its organizational evaluation toward solar water heating system
- 2023
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 10, s. 1589-1601
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Tidskriftsartikel (refereegranskat)abstract
- Renewable energy sources are fundamental to a country’s economic growth. Solar energy is one of these resources that has a favorable effect on economic growth. Turkey’s solar energy industry is still in its early stages. Due to its location and degree of sunshine each year, the country has a great solar potential. Despite the huge potential, solar energy awareness and utilization are not widespread in all parts of Turkey. In order to identify the factors that affect consumers’ decisions to utilize water heating systems, which is a sort of solar energy system, the purpose of this research is to examine these systems. In this study, all factors influencing consumers’ decisions to acquire solar water heating systems were evaluated holistically for the first time. A questionnaire was used in the study, which is a quantitative research technique. The study identifies the variables that influence consumers’ attitudes toward solar collector purchases and assesses the consequences from an organizational point of view. The study’s results act as a guide for decision-makers.
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| 17. |
- Cruz, Igor, 1986-, et al.
(författare)
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Assessment of the potential for small-scale CHP production using Organic Rankine Cycle (ORC) systems in different geographical contexts: GHG emissions impact and economic feasibility
- 2022
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Ingår i: Energy Reports. - Amsterdam, Netherlands : Elsevier. - 2352-4847. ; 8, s. 7680-7690
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Tidskriftsartikel (refereegranskat)abstract
- According to the European Commission’s 2050 Climate Strategy, renewable electricity is the most important driver for decarbonising the energy system. The intermittent nature of wind and solar creates a demand for dispatchable electricity production that can contribute to a stable and steady supply all year. This supply can be provided, for example, by biomass boilers with combined heat and power production. This paper analyses the potential for small-scale electricity production in Organic Rankine Cycle systems (ORC) in different geographical contexts. The focus is on installing ORC systems with existing biomass-fired boilers in district heating (DH) systems or industry, and with industrial excess heat streams. Economic and climate effects are studied in three countries with different climates and energy-market conditions, namely Sweden, the United Kingdom and Brazil. The results show that there is the potential to install ORC systems around the world that are both economically viable and reduce global greenhouse gas emissions. Equipment size has a large effect on the profitability of the investments. Moreover, the benefits of tax exemptions and certificates for renewable electricity production significantly impact profitability, particularly for smaller equipment sizes.
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| 18. |
- Djaafari, Abdallah, et al.
(författare)
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Hourly predictions of direct normal irradiation using an innovative hybrid LSTM model for concentrating solar power projects in hyper-arid regions
- 2022
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Ingår i: Energy Reports. - : Elsevier. - 2352-4847. ; 8, s. 15548-15562
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Tidskriftsartikel (refereegranskat)abstract
- Although solar energy harnessing capacity varies considerably based on the employed solar energy technology and the meteorological conditions, accurate direct normal irradiation (DNI) prediction remains crucial for better planning and management of concentrating solar power systems. This work develops hybrid Long Short-Term Memory (LSTM) models for assessing hourly DNI using meteorological datasets that include relative humidity, air temperature, and global solar irradiation. The study proposes a unique hybrid model, combining a balance-dynamic sine–cosine (BDSCA) algorithm with an LSTM predictor. Combining optimizers and predictors, such hybrid models are rarely developed to estimate DNI, especially in smaller prediction intervals. Therefore, various commonly adopted algorithms in relevant studies have been considered references for evaluating the new hybrid algorithm. The results show that the relative errors of the proposed models do not exceed 2.07%, with a minimum correlation coefficient of 0.99. In addition, the dimensionality of inputs was reduced from four variables to the two most cost-effective variables in DNI prediction. Therefore, these suggested models are reliable for estimating DNI in the arid desert areas of Algeria and other locations with similar climatic features.
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| 19. |
- Duvnjak Zarkovic, Sanja, 1989-, et al.
(författare)
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Integrated reliability centered distribution system planning — Cable routing and switch placement
- 2021
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Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 7, s. 3099-3115
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Tidskriftsartikel (refereegranskat)abstract
- Distribution utilities aim to operate and plan their network in a secure and economical way. The prime focus of this work is to assist utilities by developing a new integrated approach which considers the impacts of system reliability in distribution system planning (DSP). This approach merges different problems together and solves them in a two-stage process, as follows: 1. cable routing and optimal location and number of switching devices (circuit breakers and reclosers); 2. optimal location and number of tie switches. Moreover, the possibility of installing different cable options, with different prices and capacities, is included. The optimization algorithm is designed using mixed-integer programming (MIP). The developed algorithm analytically evaluates relationships between different components in the system and dynamically updates reliability indices, failure rate and restoration time, of every node in the system. This approach has been tested on two distribution systems. Despite the complexity and the exhaustiveness of the problem, MIP converges and provides the optimal solution for every studied scenario. The results show that an integrated approach enables utilities to obtain more comprehensive solutions. Moreover, by understanding the impact of parameter variation enables utilities to categorize their priorities in the decision making process and optimally invest in distribution network with respect to reliability.
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| 20. |
- Ebeed, Mohamed, et al.
(författare)
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A Modified Artificial Hummingbird Algorithm for solving optimal power flow problem in power systems
- 2024
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Ingår i: Energy Reports. - : ELSEVIER. - 2352-4847. ; 11, s. 982-1005
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Tidskriftsartikel (refereegranskat)abstract
- Optimal power flow (OPF) problem solution is a crucial task for the operators and decision makers to assign the best setting of the system components to obtain the most economic, environmental, and technical suitable state. Artificial Hummingbird Algorithm is a recent optimization algorithm that has been applied to solving several optimization problems. In this paper, a Modified Artificial Hummingbird Algorithm (MAHA) is proposed for improving the performance of the orignal Artificial Hummingbird Algorithm as well as effectivelly solve the OPF problem. The proposed MAHA is based on improving the searching capability by boosting the exploitation using the bandwidth motion around the best solution, while the exploration process is improved using the Levy flight distribution motion and the fitness-distance balance selection. This modified version helps overcome issues such as stagnation, premature convergence, and a propensity for local optima when tackling complex, nonlinear, and non-convex optimization problems like OPF. In order to confirm the effectiveness of the proposed algorithm, a series of tests are conducted on 23 standard benchmark functions, including CEC2020. The resulting outcomes are then compared to those obtained using other algorithms such as fitness-distance balance selection-based stochastic fractal search (FDBSFS), antlion optimizer (ALO), whale optimization algorithm (WOA), sine-cosine algorithm (SCA), fitness-distance balance and learning based artificial bee colony (FDB-TLABC), and traditional artificial hummingbird algorithm (AHA).The proposed algorithm is evaluated by solving the OPF problem with multiple objective functions on the IEEE 30-bus system. These objectives include fuel cost, fuel cost with valve loading effects, power losses, emissions, and voltage profile. Additionally, the algorithm's effectiveness is further assessed by testing it on single objective functions using medium and large-scale IEEE 57 and 118-bus networks.The results obtained by the proposed MAHA demonstrate its power and superiority for solving the OPF problem as well as the standard benchmark functions , surpassing the performance of other reported techniques.
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| 21. |
- Edsand, Hans -Erik, 1979, et al.
(författare)
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Power struggles: Advances and roadblocks of solar powered mini grids in Tanzania
- 2024
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Ingår i: ENERGY REPORTS. - 2352-4847. ; 11, s. 342-354
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Tidskriftsartikel (refereegranskat)abstract
- Rural energy poverty persists in Tanzania, with 77% of the population not having access to electricity. A com-bination of high solar radiation and slow extension of the national energy grid has raised off-grid solar PV based mini-grids as a potential solution. In this paper, a novel extension to the Technological Innovation System (TIS) function approach is used to analyze the positive and negative trends of solar PV based mini-grid diffusion in the country. This framework, adapted for a Global South context, considers key dynamic processes (functions) and structural components (actors and institutions) that are considered essential for diffusion of technological sys-tems, along with the general institutional infrastructure, informal institutions and other contextual factors that may influence the development and implementation of solar PV based mini-grid systems. Based on a combination of semi-structured interviews with key stakeholders and secondary data, the paper identified negative trends in several functions such as market formation, entrepreneurial activities and guidance of the search. The paper demonstrates a clear link between the worsening conditions for solar PV mini-grids with institutional changes as a result of the new political direction for the energy sector that followed the 2015 presidential election in Tanzania.
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| 22. |
- Fang, Yin, et al.
(författare)
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An accelerated gradient-based optimization development for multi-reservoir hydropower systems optimization
- 2021
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Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 7, s. 7854-7877
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Tidskriftsartikel (refereegranskat)abstract
- Hydropower is one of the significant renewable energy resources. It is regularly requested at peak time steps to meet the load requirements of power systems resources allocation. Therefore, modeling the optimal operation of hydropower systems to maximize the entire energy production of reservoir systems can be a vital task for energy investment. Deriving optimal unknown decision parameters of these reservoir systems is a nonlinear, nonconvex, and complex optimization problem. Herein, a novel optimization algorithm, called an accelerated version of gradient-based optimization (AGBO), is developed to solve a complex multi-reservoir hydropower system. This advised technique uses an efficient adaptive control parameters mechanism to stabilize the global and local search; utilizing an enhanced local escaping operator (ELEO) to extend the chances of getting away from local optima; expanding the exploitation search by applying the sequential quadratic programming (SQP) technique. At first, the developed AGBO algorithm is employed to solve the optimal operation of a complex 10-reservoir hydropower system. Secondly, the possibility of the AGBO algorithm within the global optimization problems is illustrated by numerical tests of 23 mathematical benchmark functions. Optimal results show that the proposed AGBO can approach to 0.9999% of the optimal global solution. As a result, the advised method is the most superior one compared to the other advanced optimization algorithms for maximizing the load demands in hydropower system. In conclusion, this offers a productive tool to solve the complex hydropower multi-reservoir optimization systems.
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| 23. |
- Gebresenbet, Girma
(författare)
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Performance prediction of a pump as a turbine using energy loss analysis
- 2024
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Ingår i: Energy Reports. - 2352-4847. ; 12, s. 210-225
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Tidskriftsartikel (refereegranskat)abstract
- As interest in renewable energy sources grows, interest in small-scale hydropower development and utilization increases. The development of micro- and small-scale hydropower plants is challenging, mainly due to the high cost of hydraulic turbines. If the turbine mode performance can be predicted accurately before installation, pumps as turbines (PATs) are an excellent alternative for small-scale hydropower generation. In this study, a theoretical procedure using a detailed energy loss analysis to determine PAT's energy losses is developed, and a non-dimensional performance prediction model is presented. The models were implemented to determine the pressure, head, torque, power, and efficiency across a wide range of flow rates. This work clearly characterizes the effects of individual losses, thereby acknowledging their influence. The prediction results were tested at ten different flow rates, ranging from 50 % to 180 %. The model result was validated through experiments using a hydro-pump test rig developed at the Bahir Dar Institute of Technology at Bahir Dar University. The numerical and model results have good agreement with the experimental results. at BEP The experimental result gives a 1.6 flow rate, 1.72 head ratios, and an efficiency of 76.53 %, 78.09 %, and 74.04 % using analytical, numerical, and experimental methods, respectively. The PAT off-design efficiency decreases sharply below BEP and smoothly above BEP. At BEP, the CFD and analytical results deviated by -2.04 % and 3.08 %, respectively, from the experimental results. Further, the detailed energy loss analysis revealed that the volute frictional (12.1 %), the throat frictional (11.9 %), the inlet pipe frictional (11.2 %), the impeller frictional (9.4 %), and the volute diffusion (8.9 %) losses take the major energy losses sequentially. This provides full insight for applying performance optimization measures.
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| 24. |
- Gubin, Pavel Y., et al.
(författare)
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Optimizing generating unit maintenance with the league championship method: A reliability-based approach
- 2023
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Ingår i: Energy Reports. - : ELSEVIER. - 2352-4847. ; 10, s. 135-152
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Tidskriftsartikel (refereegranskat)abstract
- The electrical power industry has experienced an unprecedented pace of digital transformation as a prevailing economic trend in recent years. This shift towards digitalization has resulted in an increasing interest in the collection of real-time equipment condition data, which provides opportunities for implementing sensor-driven condition-based repair. As a result, there is a growing need for the development of generator maintenance scheduling to consider probabilistic equipment behavior, which requires significant computational efforts. To address this issue, the research proposes the use of a meta-heuristic league championship method (LCM) for generator maintenance scheduling, considering random generation profiles based on generation adequacy criteria. The experimental part of the study compares this approach and its modifications to widely used meta-heuristics, such as differential evolution and particle swarm methods. The identification and demonstration of optimal method settings for the generation maintenance scheduling problem are presented. Subsequently, it is illustrated that employing random league scheduling expedience can reduce the variance of objective function values in resulting plans by over three times, with values of 0.632 MWh and 0.205 MWh for conventional and proposed techniques respectively. In addition, three approaches are compared to assess generation adequacy corresponding to different schedules. The study emphasizes the efficacy of employing the LCM approach in scheduling generator maintenance. Specifically, it showcases that among all the methods examined, the LCM approach exhibits the lowest variance in objective function values, with values of 38.81 and 39.90 MWh for LCM and its closest rival, the modified particle swarm method (MPSM), respectively.& COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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| 25. |
- Gunasekara, Saman Nimali, Dr. 1982-, et al.
(författare)
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Distributed cold storage in district cooling-Grid dynamics and optimal integration for a Swedish case study
- 2021
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Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 7, s. 419-429
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Tidskriftsartikel (refereegranskat)abstract
- District cooling (DC) is gaining interest with global warming and rising demands on indoor comfort. As DC grid expansions are capital intensive, cost effective alternatives to meet these rising cooling demands are desired. Integrating cold storage (CS) into the grids is one attractive choice, allowing peak shaving, load shifting, and renewable electricity recovery via power-to cold. To analyze the impact of new CSs, the DC distribution grid dynamics must be investigated. This work evaluates the implementation of several new CSs into an existing DC system (called the base case-BC), to find the optimal solution. This is performed considering the case study DC system of Norrenergi AB, Sweden, catering to Solna and Sundbyberg via three production plants Solnaverket, Sundbybergsverket and Frosundaverket, and a 10 MW CS (in Solnaverket). The software tool Netsim is used for distribution grid dynamics analysis of the BC and three scenarios with additional cold storages, for the optimization of differential pressure (dP) of the grids to be within 100-800 kPa. These scenarios include: one additional 15 MW CS in Sundbybergsverket (Scenario 1), one additional 15 MW CS in Frosunda (Scenario 2) and two additional 3 MW CSs in Sundbybergsverket and Frosunda (Scenario 3). The CSs in Sundbybergsverket are centrally placed, whereas, those in Frosunda were positioned in a grid loop experiencing low differential pressure, identified in Netsim simulations of BC. The simulations were done for 24 h at 1-hour resolution, on a chosen historically highest demand day (02 August 2018). The results indicate that the optimal solution is implementing two additional CSs in Sundbybergsverket (centralized) and Frosunda (distributed), each with a capacity between 3-7.5 MW (6-15 MW total capacities). Further evaluations to determine the optimal sizing of these CSs is the next step in this study.
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