Applications & Pathways
A Smart Strategy for Sizing of Hybrid Renewable Energy System to Supply Remote Loads in Saudi Arabia
Oct 2021
Publication
The use of hybrid renewable energy systems (HRES) has become the best option for supplying electricity to sites remote from the central power system because of its sustainability environmental friendliness and its low cost of energy compared to many conventional sources such as diesel generators. Due to the intermittent nature of renewable energy resources there is a need however for an energy storage system (ESS) to store the surplus energy and feed the energy deficit. Most renewable sources used battery storage systems (BSS) a green hydrogen storage system (GHSS) and a diesel generator as a backup for these sources. Batteries are very expensive and have a very short lifetime and GHSS have a very expensive initial cost and many security issues. In this paper a system consisting of wind turbines and a photovoltaic (PV) array with a pumped hydro energy storage (PHES) system as the main energy storage to replace the expensive and short lifetime batteries is proposed. The proposed system is built to feed a remote area called Dumah Aljandal in the north of Saudi Arabia. A smart grid is used via a novel demand response strategy (DRS) with a dynamic tariff to reduce the size of the components and it reduces the cost of energy compared to a flat tariff. The use of the PHES with smart DRS reduced the cost of energy by 34.2% and 41.1% compared to the use of BSS and GHSS as an ESS respectively. Moreover the use of 100% green energy sources will avoid the emission of an estimated 2.5 million tons of greenhouse gases every year. The proposed system will use a novel optimization algorithm called the gradually reduced particles of particle swarm optimization (GRP-PSO) algorithm to enhance the exploration and exploitation during the searching iterations. The GRP-PSO reduces the convergence time to 58% compared to the average convergence time of 10 optimization algorithms used for comparison. A sensitivity analysis study is introduced in this paper in which the effect of ±20% change in wind speed and solar irradiance are selected and the system showed a low effect of these resources on the Levelized cost of energy of the HRES. These outstanding results proved the superiority of using a pumped-storage system with a dynamic tariff demand response strategy compared to the other energy storage systems with flat-rate tariffs.
Performance Analysis of Hydrogen Fuel Cell with Two-stage Turbo Compressor for Automotive Applications
May 2021
Publication
This paper discusses the numerical modeling of an automobile fuel cell system using a two-stage turbo-compressor for air supply. The numerical model incorporates essential input parameters for air and hydrogen flow. The model also performed mass and energy balances across different components such as pump fan heat-exchanger air compressor and keeps in consideration the pressure losses across flow pipes and various mechanical parts. The compressor design process initiates with numerical analysis of the preliminary design of a highly efficient two-stage turbo compressor with an expander as a single-stage compressor has several limitations in terms of efficiency and pressure ratio. The compressor’s design parameters were carefully studied and analyzed with respect to the highly efficient fuel cell stack (FCS) used in modern hydrogen vehicles. The model is solved to evaluate the overall performance of PEM FCS. The final compressor has a total pressure and temperature of 4.2 bar and 149.3°C whereas the required power is 20.08kW with 3.18kW power losses and having a combined efficiency of 70.8%. According to the FC model with and without expander the net-power outputs are 98.15kW and 88.27kW respectively and the maximum efficiencies are 65.1% and 59.1% respectively. Therefore it can be concluded that a two-stage turbo compressor with a turbo-expander can have significant effects on overall system power and efficiency. The model can be used to predict and optimize system performance for PEM FCS at different operating conditions.
Minimum Emissions Configuration of a Green Energy–Steel System: An Analytical Model
May 2022
Publication
The need to significantly reduce emissions from the steelmaking sector requires effective and ready-to-use technical solutions. With this aim different decarbonization strategies have been investigated by both researchers and practitioners. To this concern the most promising pathway is represented by the replacement of natural gas with pure hydrogen in the direct reduced iron (DRI) production process to feed an electric arc furnace (EAF). This solution allows to significantly reduce direct emissions of carbon dioxide from the DRI process but requires a significant amount of electricity to power electrolyzers adopted to produce hydrogen. The adoption of renewable electricity sources (green hydrogen) would reduce emissions by 95–100% compared to the blast furnace–basic oxygen furnace (BF–BOF) route. In this work an analytical model for the identification of the minimum emission configuration of a green energy–steel system consisting of a secondary route supported by a DRI production process and a renewable energy conversion system is proposed. In the model both technological features of the hydrogen steel plant and renewable energy production potential of the site where it is to be located are considered. Compared to previous studies the novelty of this work consists of the joint modeling of a renewable energy system and a steel plant. This allows to optimize the overall system from an environmental point of view considering the availability of green hydrogen as an inherent part of the model. Numerical experiments proved the effectiveness of the model proposed in evaluating the suitability of using green hydrogen in the steelmaking process. Depending on the characteristics of the site and the renewable energy conversion system adopted decreases in emissions ranging from 60% to 91% compared to the BF–BOF route were observed for the green energy–steel system considered It was found that the environmental benefit of using hydrogen in the secondary route is strictly related to the national energy mix and to the electrolyzers’ technology. Depending on the reference context it was found that there exists a maximum value of the emission factor from the national electricity grid below which is environmentally convenient to produce DRI by using only hydrogen. It was moreover found that the lower the electricity consumption of the electrolyzer the higher the value assumed by the emission factor from the electricity grid which makes the use of hydrogen convenient.
Assessment of Operational Performance for an Integrated ‘Power to Synthetic Natural Gas’ System
Dec 2021
Publication
This article presents a power to SNG (synthetic natural gas) system that converts hydrogen into SNG via a methanation process. In our analysis detailed models for all the elements of the system are built. We assume a direct connection between a wind farm and a hydrogen generator. For the purposes of our calculations we also assume that the hydrogen generator is powered by the renewable source over a nine-hour period per day (between 21:00 and 06:00) and this corresponds to the off-peak period in energy demand. In addition a hydrogen tank was introduced to maximize the operating time of the methanation reactor. The cooperation between the main components of the system were simulated using Matlab software. The primary aim of this paper is to assess the influence of various parameters on the operation of the proposed system and to optimize its yearly operation via a consideration of the most important constraints. The analyses also examine different nominal power values of renewables from 8 to 12 MW and hydrogen generators from 3 to 6 MW. Implementing the proposed configuration taking into account the direct connection of the hydrogen generator and the methanation reactor showed that it had a positive effect on the dynamics and the operating times of the individual subsystems within the tested configuration
Energy Essentials: A Guide to Hydrogen
Jan 2020
Publication
Climate change and air quality concerns have pushed clean energy up the global agenda. As we switch over to new cleaner technologies and fuels our experience of using power heat and transport are going to change transforming the way we live work and get from A to B. Explore this guide to find out what hydrogen is how it is made transported and used what the experience would be like in the home for transport and for businesses and discover what the future of hydrogen might be.
Visit the Energy Institute website for more information
Visit the Energy Institute website for more information
Roadmap to Hydrogen in the NTS - National Grid Gas Transmission
Jan 2020
Publication
DNV GL believes that the National Transmission System (NTS) will be central to the future of decarbonised energy in the UK. The future NTS could transmit natural gas hydrogen blends of the two and carbon dioxide. New pipelines will be built however a large cost-saving is available if the existing NTS assets can also be re-purposed. To move towards this future National Grid Gas Transmission wants to develop a project to trial injection hydrogen into the NTS. This is an opportunity to show that National Grid is part of the solution to achieving Net Zero. The trial will demonstrate to the Government and public that re-purposing the NTS is cost-effective safe and involves minimal disruption.
This report sets out a roadmap of projects to provide the knowledge needed for the trial. The roadmap was developed by assessing the knowledge required and how much of it already existed. The knowledge already available is summarised in this report with references to where further details can be found. Gaps in the knowledge are then described. The roadmap consists of projects to conduct work to close the knowledge gaps. The results are summarised in the figures below and in the box to the right.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
This report sets out a roadmap of projects to provide the knowledge needed for the trial. The roadmap was developed by assessing the knowledge required and how much of it already existed. The knowledge already available is summarised in this report with references to where further details can be found. Gaps in the knowledge are then described. The roadmap consists of projects to conduct work to close the knowledge gaps. The results are summarised in the figures below and in the box to the right.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Mach 4 Simulating Experiment of Pre-Cooled Turbojet Engine Using Liquid Hydrogen
Jan 2022
Publication
This study investigated a pre-cooled turbojet engine for a Mach 5 class hypersonic transport aircraft. The engine was demonstrated under takeoff and Mach 2 flight conditions and a Mach 5 propulsion wind tunnel test is planned. The engine is composed of a pre-cooler a core engine and an afterburner. The engine was tested under simulated Mach 4 conditions using an air supply facility. High-temperature air under high pressure was supplied to the engine components through an airflow control valve and an orifice flow meter and liquid hydrogen was supplied to the pre-cooler and the core engine. The results confirmed that the starting sequence of the engine components was effective under simulated Mach 4 conditions using liquid hydrogen fuel. The pre-cooling effect caused no damage to the rotating parts of the core engine in the experiment.
Hy4Heat Conversion of Industrial Heating Equipment to Hydrogen - Work Package 6
Jan 2020
Publication
The study focuses on converting current industrial natural gas heating technologies to use 100% hydrogen considering the evidence which must be available before a decision on the UK’s decarbonisation pathway for heating could be made. The aim of the study is to assess the technical requirements and challenges associated with industrial hydrogen conversion and estimate the associated costs and timeframes.
This report and any attachment is freely available on the Hy4Heat website here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
This report and any attachment is freely available on the Hy4Heat website here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Hydrogen Impact on Gas Engine CHP - Cadent Ltd
Feb 2019
Publication
The key project objectives include:
The output from this project will also inform the HyDeploy NIC project in relation to potential hydrogen content limits. The project will be presented at the IGEM Gas Quality Working Group (IGEM GQWG).
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
- Understand the range size type mode of operation and control system of installed gas engines in the UK. This will include equipment for CHP and for stand-by power operation.
- Produce data sets on the impact of hydrogen on gas engine operational performance.
- Develop knowledge on the impact of hydrogen content on the operation of the gas engine including overall efficiency changes to emissions profiles overall system operability.
- Providing outline guidance on a potential hydrogen limit that should be considered regarding use of natural gas/hydrogen mixed fuels in gas engines.
- Outlining a high-level view on the reliability and impact on maintenance and replacement regimes if gas engines operate on natural gas/hydrogen mixed fuels for extended time periods.
- Highlight any existing barriers to use of natural gas and hydrogen blends in gas engine and through contact with OEMs develop an understanding of future technology developments that may be needed to enable the use of “high” hydrogen blends.
The output from this project will also inform the HyDeploy NIC project in relation to potential hydrogen content limits. The project will be presented at the IGEM Gas Quality Working Group (IGEM GQWG).
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Hydrogen and Fuel Cell Technologies for Heating: A Review
Jan 2015
Publication
The debate on low-carbon heat in Europe has become focused on a narrow range of technological options and has largely neglected hydrogen and fuel cell technologies despite these receiving strong support towards commercialisation in Asia. This review examines the potential benefits of these technologies across different markets particularly the current state of development and performance of fuel cell micro-CHP. Fuel cells offer some important benefits over other low-carbon heating technologies and steady cost reductions through innovation are bringing fuel cells close to commercialisation in several countries. Moreover fuel cells offer wider energy system benefits for high-latitude countries with peak electricity demands in winter. Hydrogen is a zero-carbon alternative to natural gas which could be particularly valuable for those countries with extensive natural gas distribution networks but many national energy system models examine neither hydrogen nor fuel cells for heating. There is a need to include hydrogen and fuel cell heating technologies in future scenario analyses and for policymakers to take into account the full value of the potential contribution of hydrogen and fuel cells to low-carbon energy systems.
Hy4Heat Understanding Commercial Appliances - Work Package 5
Nov 2020
Publication
The 'Hydrogen for Heat' (Hy4Heat) programme aims to support the UK Government in its ambitions to decarbonise the UK energy sector in line with the targets of the Climate Change Act 2008 by attempting to evaluate and de-risk the natural gas to hydrogen network conversion option. The impact on the commercial sector is an important factor in understanding the feasibility of utilising hydrogen to decarbonise heat in the UK. The overall objective of the market research study Work Package 5 (WP5) was to determine if it is theoretically possible to successfully convert the commercial sector to hydrogen. This work will contribute to the understanding of the scale type and capacity of gas heating appliances within the sector providing a characterisation of the market and determining the requirements and feasibility for successfully transitioning them to hydrogen in the future.
This report and any attachment is freely available on the Hy4Heat website here. The report can also be downloaded directly by clicking on the pdf icon above
This report and any attachment is freely available on the Hy4Heat website here. The report can also be downloaded directly by clicking on the pdf icon above
A Socio-technical Perspective on the Scope for Ports to Enable Energy Transition
Jan 2021
Publication
The paper applies the multi-level perspective (MLP) in a descriptive study of three Norwegian ports to shed new light on the sociotechnical processes that structure their efforts to develop into zero emission energy hubs. While exogenous pressures cause tensions over port governance the studied ports utilize their full spectre of functions; as landlords operators authorities and community managers to enable transition. The respective approaches vary related to their local context market situation and social networks including port's relations with their owners. Individual orientations and organizational capacity further influence their engagement with radical innovation niches (e.g. OPS hydrogen LNG). The study highlights the active role of ports in sustainability transition. It shows how the interaction between geographical factors and institutional work influences the scope for new solutions around the individual port and how this makes for different feedback loops and contributions to sustainability transition in wider transport and energy systems.
Combustion Analysis of Hydrogen-diesel Dual Fuel Engine with Water Injection Technique
Dec 2018
Publication
In this paper the effect of direct diesel injection timing and engine speed on the performance and emissions of CI engine operating on RCCI (H2/diesel mixture) coupled with water injection have been numerically investigated and validated. The simulation have been carried out using GT-Power professional software. A single cylinder dual fuel compression ignition model has been built. The diesel fuel was injected directly to the cylinder. The hydrogen and water were injected to the engine intake manifold and engine port with constant mass flow rate and constant temperature for all engine speed. During the simulation the engine speed was varied from 1000 to 5000 rpm and the diesel injection timing was varied from (−5° to −25° CAD). In addition the optimized diesel injection timing for specific engine operation parameters has also been performed. The results show that for specific injection timing and constant hydrogen and water mass flow rate the increase of engine speed results in an increase in the cylinder temperature engine brake power brake specific fuel consumption and NO emissions; but decreases brake thermal efficiency. Moreover the analysis performed shows that the advanced injection timing decreases the engine power brake thermal efficiency and CO emissions; but increases NO emissions.
Hydrogen: A Critical Part of Heat Decarbonisation
Feb 2021
Publication
The use of clean hydrogen is likely to form a key part of a net-zero emissions future and has the potential to replace natural gas for end use heating. As part of BDR Thermea Group Baxi Heating UK are at the forefront of hydrogen boiler development. Working with the Hy4Heat programme hydrogen fuelled boilers have been produced for inclusion in trial sites across the UK. This presentation will explore progress to date together with the hydrogen-ready boiler concept.
Path to Hydrogen Competitiveness: A Cost Perspective
Jan 2020
Publication
This latest Hydrogen Council report shows that the cost of hydrogen solutions will fall sharply within the next decade – and sooner than previously expected. As scale up of hydrogen production distribution equipment and component manufacturing continues cost is projected to decrease by up to 50% by 2030 for a wide range of applications making hydrogen competitive with other low-carbon alternatives and in some cases even conventional options.
Significant cost reductions are expected across different hydrogen applications. For more than 20 of them such as long-distance and heavy-duty transportation industrial heating and heavy industry feedstock which together comprise roughly 15% of global energy consumption the hydrogen route appears the decarbonisation option of choice – a material opportunity.
The report attributes this trajectory to scale-up that positively impacts the three main cost drivers:
To deliver on this opportunity supporting policies will be required in key geographies together with investment support of around $70 billion in the lead up to 2030 in order to scale up and achieve hydrogen competitiveness. While this figure is sizable it accounts for less than 5% of annual global spending on energy. For comparison support provided to renewables in Germany totalled roughly $30 billion in 2019.
The study is based on real industry data with 25000 data points gathered and analysed from 30 companies using a rigorous methodology. The data was collected and analytical support provided by McKinsey & Company and it represents the entire hydrogen value chain across four key geographies (US Europe Japan/Korea and China). Data was also reviewed by an independent advisory group comprised of recognised hydrogen and energy transition experts.
You can download the full report from the Hydrogen Council website here
The executive summary can be found here
Significant cost reductions are expected across different hydrogen applications. For more than 20 of them such as long-distance and heavy-duty transportation industrial heating and heavy industry feedstock which together comprise roughly 15% of global energy consumption the hydrogen route appears the decarbonisation option of choice – a material opportunity.
The report attributes this trajectory to scale-up that positively impacts the three main cost drivers:
- Strong fall in the cost of producing low carbon and renewable hydrogen;
- Lower distribution and refuelling costs thanks to higher load utilisation and scale effect on infrastructure utilisation; and
- Dramatic drop in the cost of components for end-use equipment under scaling up of manufacturing.
To deliver on this opportunity supporting policies will be required in key geographies together with investment support of around $70 billion in the lead up to 2030 in order to scale up and achieve hydrogen competitiveness. While this figure is sizable it accounts for less than 5% of annual global spending on energy. For comparison support provided to renewables in Germany totalled roughly $30 billion in 2019.
The study is based on real industry data with 25000 data points gathered and analysed from 30 companies using a rigorous methodology. The data was collected and analytical support provided by McKinsey & Company and it represents the entire hydrogen value chain across four key geographies (US Europe Japan/Korea and China). Data was also reviewed by an independent advisory group comprised of recognised hydrogen and energy transition experts.
You can download the full report from the Hydrogen Council website here
The executive summary can be found here
Medium-Energy Synthesis Gases from Waste as an Energy Source for an Internal Combustion Engine
Dec 2021
Publication
The aim of the presented article is to analyse the influence of synthesis gas composition on the power economic and internal parameters of an atmospheric two-cylinder spark-ignition internal combustion engine (displacement of 686 cm3 ) designed for a micro-cogeneration unit. Synthesis gases produced mainly from waste contain combustible components as their basic material (methane hydrogen and carbon monoxide) as well as inert gases (carbon dioxide and nitrogen). A total of twelve synthesis gases were analysed that fall into the category of medium-energy gases with lower heating value in the range from 8 to 12 MJ/kg. All of the resulting parameters from the operation of the combustion engine powered by synthesis gases were compared with the reference fuel methane. The results show a decrease in the performance parameters for all operating loads and an increase in hourly fuel consumption. Specifically for the operating speed of the micro-cogeneration unit (1500 L/min) the decrease in power parameters was in the range of 7.1–23.5%; however the increase in hourly fuel consumption was higher by 270% to 420%. The decrease in effective efficiency ranged from 0.4 to 4.6% which in percentage terms represented a decrease from 1.3% to 14.5%. The process of fuel combustion was most strongly influenced by the proportion of hydrogen and inert gases in the mixture. It can be concluded that setting up the synthesis gas production in the waste gasification process in order to achieve optimum performance and economic parameters of the combustion engine for a micro cogeneration unit has an influential role and is of crucial importance.
Renewables Readiness Assessment: The Hashemite Kingdom of Jordan
Feb 2021
Publication
Jordan's energy diversification strategy is centred around renewables which are expected will provide the low-cost reliable secure and environmentally sustainable energy required to power its new engines of economic growth – manufacturing transport construction and agriculture.
The National Energy Strategy 2020–2030 presents the evolution of the energy sector under its vision for stimulating demand achieving efficiency and improving electricity system flexibility.
This Renewables Readiness Assessment (RRA) highlights key actions for the short and medium-term that could create more conductive conditions for renewable energy development. It aims to help unlock Jordan's renewable energy potential and provide the means to meet the energy diversification goals of its national strategy.
The study was undertaken by the Ministry of Energy and Mineral Resources (MEMR) in collaboration with the International Renewable Energy Agency (IRENA).
Key recommendations:
The National Energy Strategy 2020–2030 presents the evolution of the energy sector under its vision for stimulating demand achieving efficiency and improving electricity system flexibility.
This Renewables Readiness Assessment (RRA) highlights key actions for the short and medium-term that could create more conductive conditions for renewable energy development. It aims to help unlock Jordan's renewable energy potential and provide the means to meet the energy diversification goals of its national strategy.
The study was undertaken by the Ministry of Energy and Mineral Resources (MEMR) in collaboration with the International Renewable Energy Agency (IRENA).
Key recommendations:
- Provide the necessary conditions for renewables growth in the power sector.
- Foster continued growth of renewable power generation.
- Plan the integration of higher shares of renewable power.
- Incentivise the use of renewables for heating and cooling.
- Support renewable transport and mobility options.
- Catalyse renewable energy investment. Strengthen local industries and create jobs in renewables.
A Dynamic Performance Diagnostic Method Applied to Hydrogen Powered Aero Engines Operating under Transient Conditions
Apr 2022
Publication
At present aero engine fault diagnosis is mainly based on the steady-state condition at the cruise phase and the gas path parameters in the entire flight process are not effectively used. At the same time high quality steady-state monitoring measurements are not always available and as a result the accuracy of diagnosis might be affected. There is a recognized need for real-time performance diagnosis of aero engines operating under transient conditions which can improve their condition-based maintenance. Recent studies have demonstrated the capability of the sequential model-based diagnostic method to predict accurately and efficiently the degradation of industrial gas turbines under steady-state conditions. Nevertheless incorporating real-time data for fault detection of aero engines that operate in dynamic conditions is a more challenging task. The primary objective of this study is to investigate the performance of the sequential diagnostic method when it is applied to aero engines that operate under transient conditions while there is a variation in the bypass ratio and the heat soakage effects are taken into consideration. This study provides a novel approach for quantifying component degradation such as fouling and erosion by using an adapted version of the sequential diagnostic method. The research presented here confirms that the proposed method could be applied to aero engine fault diagnosis under both steady-state and dynamic conditions in real-time. In addition the economic impact of engine degradation on fuel cost and payload revenue is evaluated when the engine under investigation is using hydrogen. The proposed method demonstrated promising diagnostic results where the maximum prediction errors for steady state and transient conditions are less than 0.006% and 0.016% respectively. The comparison of the proposed method to a benchmark diagnostic method revealed a 15% improvement in accuracy which can have great benefit when considering that the cost attributed to degradation can reach up to $702585 for 6000 flight cycles of a hydrogen powered aircraft fleet. This study provides an opportunity to improve our understanding of aero engine fault diagnosis in order to improve engine reliability availability and efficiency by online health monitoring.
Scottish Hydrogen Assessment
Dec 2020
Publication
During 2020 the Scottish Government in partnership with Highlands and Islands Enterprise and Scottish Enterprise commissioned Arup and E4Tech to carry out a hydrogen assessment to deepen our evidence base in order to inform our policies on hydrogen going forward. The assessment aims to investigate how and where hydrogen may fit within the evolving energy system technically geographically and economically. To assist in this consideration a key part of the Hydrogen Assessment is the development of distinct viable scenarios for hydrogen deployment in Scotland and the economic assessment of those scenarios.<br/>From our assessment it is clear that hydrogen is not just an energy and emissions reduction opportunity; it could also have an important role in generating new economic opportunities in Scotland. The assessment forms an important part of the evidence base that informed the development of the Hydrogen Policy Statement.
Assessment of the Impact of Material Selection on Aviation Sustainability, from a Circular Economy Perspective
Jan 2022
Publication
Climate change and global warming pose great sustainability challenges to the aviation industry. Alternatives to petroleum-based fuels (hydrogen natural gas etc.) have emerged as promising aviation fuels for future aircraft. The present study aimed to contribute to the understanding of the impact of material selection on aviation sustainability accounting for the type of fuel implemented and circular economy aspects. In this context a decision support tool was introduced to aid decisionmakers and relevant stakeholders to identify and select the best-performing materials that meet their defined needs and preferences expressed through a finite set of conflicting criteria associated with ecological economic and circularity aspects. The proposed tool integrates life-cycle-based metrics extending to both ecological and economical dimensions and a proposed circular economy indicator (CEI) focused on the material/component level and linked to its quality characteristics which also accounts for the quality degradation of materials which have undergone one or more recycling loops. The tool is coupled with a multi-criteria decision analysis (MCDA) methodology in order to reduce subjectivity when determining the importance of each of the considered criteria.
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