Clean Energy and Sustainability Open Access

Carbon Neutrality and Life Cycle Thinking

Climate change is one of the most critical sustainability challenges facing the humanity. International communities have joined forces to mitigate climate change impact and aim to achieve carbon neutrality in the coming decades. To achieve this ambitious goal, life cycle thinking can play critical roles. Specifically, life cycle thinking helps evaluate the true climate impacts to avoid shifting emissions across processes in a product life cycle. It can also help inform consumers with carbon footprint information to make climate-conscious choices. Finally, it can help identify key processes dominating the carbon footprint of a product so that future improvement can set priorities. High quality data is required for accurate and timely carbon footprint accounting and critical challenges exist to obtain and share such data.

A Review of the Energy Policy in Greece in the Last 50 Years and Its Implications for Prosperity

This paper elucidates the development of electricity production and distribution in Greece from the 1950s to date, in correlation with national and European energy policy. During this period, Greece experienced a multifaceted energy transition, including both the transition of ownership of energy generation companies from public to private and a transition from an energy mix in which coal (lignite) served as a major and inexpensive resource to a mix in which wind power, solar power and natural gas gained a primary role, but with high costs for energy generation. The correlation between electrical energy consumption and economic growth is explored in this context, revealing an increase in consumption before the 2009 recession and a decline thereafter. The study investigates the correlation between escalating electricity prices and legislative dependencies that mandated the purchase of wind- and solar-generated electricity at exorbitant rates, the closure of cost-effective lignite units, and the reliance on natural gas—a commodity susceptible to geopolitical shifts. It also shows that, given the structure of the Greek energy mix, the increase in the share of wind and solar energy in the mix is directly related to the increase in the price of electricity. Highlighting the importance of energy costs for prosperity, this paper underscores, through the detailed review of the Greek energy “landscape”, that the major determinants of electricity prices are both the accessibility to natural resources but also their proper and judicious management.

Advancing Green Hydrogen Production in Saudi Arabia: Harnessing Solar Energy and Seawater Electrolysis

The transition to clean and sustainable energy sources is crucial for combating the challenges posed by climate change. Green hydrogen, produced through renewable energy-driven electrolysis, holds significant promise as a viable clean energy carrier. The study introduces a system that leverages abundant solar energy and utilizes seawater as the feedstock for electrolysis, potentially offering a cost-effective solution. A comprehensive mathematical model, implemented in MATLAB, is employed to simulate the design and operational efficiency of the proposed green hydrogen production system. The system’s core components include solar panels as a clean energy source, an advanced MPPT charge controller ensuring optimal power delivery to the electrolyzer, and a seawater tank serving as the electrolyte source. The model combines these elements, allowing for continuous operation and efficient hydrogen production, addressing concerns about energy losses and cost-effectiveness. Results demonstrate the influence of solar irradiance on the system’s performance, revealing the need to account for seasonal variations when designing green hydrogen production facilities. Theoretical experiments are conducted to evaluate the behavior of a lithium battery, essential for stabilizing the system’s output and ensuring continuous operation during periods of low solar radiation. 

Reduced Climate Impacts of Dairy Sludge Management by Introducing Hydrothermal Carbonization

Dairies which produce cheese and milk products can, however, produce large volumes of wastewater that require treatment, usually via activated sludge treatment. Disposal of the resulting activated sludge to land is viewed favorably as the sludge is rich in phosphorus (P) and nitrogen (N) and enables nutrient recycling. Nonetheless, sludge management can significantly influence the greenhouse gas (GHG) emissions to the atmosphere. This manuscript has modelled the GHG emissions arising from two sludge management strategies currently adopted by Danish dairies whereby: (i) sludge is stored and later applied to fields; or (ii) sludge is treated by anaerobic digestion (AD), stored, and the digestate will later be applied to fields. This is compared to (iii) an alternative sludge management strategy with treatment by Hydrothermal Carbonization (HTC). HTC is a technologically simple sludge treatment that could lower the cost for dewatering dairy sludge, forming a biochar-like material known as hydrochar. The produced hydrochar can be applied to the land for the purpose of carbon sequestration, P and N recycling. Our calculations indicate that GHG balances of HTC sludge management can result in a net carbon sequestration of 63 kg CO_2eq per ton sludge, as opposed to net emissions of 420 and 156 kg CO_2eq per ton sludge for strategies (i) and (ii), therefore offering significant reductions GHG emissions for the dairy sector.

Clean Energy and Sustainability: A New Open-Access Journal to Share Your Research Results on Renewable/Clean Energies and Sustainability

Estimate of Economic Impact of EVs Li-ion Batteries Recovery

Nowadays, increasing attention is directed towards the sustainable use of raw materials. For a circular economy, recovery from spent devices represents a fundamental practice. With the transition to electric mobility, an increasing number of devices powered by lithium batteries are produced. Indeed, this is the fastest growing sector producing spent batteries, which are an important secondary source of critical raw materials, such as lithium, cobalt, graphite, and nickel. Therefore, this work aims to quantify the economic impact of recovering raw materials from lithium batteries used in the electric vehicles sector. Based on the chemical composition of the various lithium batteries and their market diffusion, the intrinsic economic value of this waste has been estimated to be around 6500 €/ton. Starting from the literature data on the global energy demand from lithium batteries and deriving the trend of their specific energy over time, the mass of material introduced into the market annually is estimated to reach 60 Mton/year by 2040. The annual amount of end-of-life lithium batteries was calculated by applying the Weibull distribution to describe the probability of failure, yielding 10 Mton/year by 2040. Finally, based on these results, the economic impact of the recovery market was assessed for two different scenarios.

The Potential of Salinity Gradient Energy Using Reverse Electrodialysis to Generate Electricity for Seawater Desalination Plants, an Example from Western Australia

Seawater desalination plays a vital role in addressing the increasing global demand for freshwater. However, the energy-intensive nature of desalination processes and the generation of brine by-products pose environmental challenges. In Western Australia (WA), approximately 48% of freshwater is supplied by two seawater desalination plants employing the energy-intensive seawater reverse osmosis (SWRO) method. These plants are powered by a combination of renewable and conventional energy sources. Typically, the most efficient approach for desalination plants involves a blend of renewable energy sources. Salinity gradient energy (SGE) harnessed through the reverse electrodialysis (RED) system, which derives energy from mixing waters with varying salinities, has emerged as a potential solution. RED utilizes ion-exchange membranes to convert the chemical potential difference between two solutions into electric power. The net specific energy of SGE, calculated based on the Gibbs free energy associated with mixing seawater and wastewater, is estimated at approximately 0.14 kWh per cubic metre of brine for SWRO desalination plants. The combined SGE potential of WA’s two desalination facilities theoretically amounts to approximately 87.4 MWh of energy. However, due to the inherent limitations of the RED system’s current energy efficiency, only about 2.5% of the desalination plant’s energy requirements can be met through this technique. This paper addresses a significant gap in the literature by analyzing the technical and economic constraints of utilizing salinity gradient energy (SGE) through the reverse electrodialysis (RED) system for seawater desalination plants. This marks the first examination of its kind, shedding light on both the technical feasibility and economic challenges of SGE-RED application in this context. The scientific contribution lies in its innovative approach, integrating technical and economic perspectives to provide an understanding of SGE-RED technology’s potential drawbacks and opportunities. By identifying and tackling these challenges, this paper aims to pave the way for optimizing SGE-RED systems for practical implementation in seawater desalination plants.

Thermal and Economic Evaluations of a Drain Water Heat Recovery Device under Transient Conditions

This study explores the transient characteristics of a drain water heat recovery (DWHR) device employed for heat recovery from warm grey water in buildings. Experimental measurements were conducted to investigate the response time of the DWHR device under various flow conditions. The thermal performance of the system was assessed using both transient and steady-state effectiveness analyses. The findings reveal that the response time is influenced by the water volume within the system, with an increase observed, and by the water flow rate, which leads to a decrease in response time. Additionally, a decrease in effectiveness is noted when hot water is used in short and frequent intervals. Furthermore, an economic analysis demonstrates that considering the transient behavior of the device results in a significant overall decrease of 37% in annual savings. Specifically, the usage of sinks exhibits a reduction in annual savings by 56%, while showers show a decrease of 13% in annual savings.

The Interplay between Experimental Data and Uncertainty Analysis in Quantifying CO₂ Trapping during Geological Carbon Storage

Numerical simulation is a widely used tool for studying CO₂ storage in porous media. It enables the representation of trapping mechanisms and CO₂ retention capacity. The complexity of the involved physicochemical phenomena necessitates multiphase flow, accurate fluid and rock property representation, and their interactions. These include CO₂ solubility, diffusion, relative permeabilities, capillary pressure hysteresis, and mineralization, all crucial in CO₂ trapping during carbon storage simulations. Experimental data is essential to ensure accurate quantification. However, due to the extensive data required, modeling under uncertainty is often needed to assess parameter impacts on CO₂ trapping and its interaction with geological properties like porosity and permeability. This work proposes a framework combining laboratory data and stochastic parameter distribution to map uncertainty in CO₂ retention over time. Published data representing solubility, residual trapping, and mineral trapping are used to calibrate prediction models. Geological property variations, like porosity and permeability, are coupled to quantify uncertainty. Results from a saline sandstone aquifer model demonstrate significant variation in CO₂ trapping, ranging from 17% (P10 estimate) to 56% (P90), emphasizing the importance of considering uncertainty in CO₂ storage projects. Quadratic response surfaces and Monte Carlo simulations accurately capture this uncertainty, resulting in calibrated models with an R-squared coefficient above 80%. In summary, this work provides a practical and comprehensive framework for studying CO₂ retention in porous media, addressing uncertainty through stochastic parameter distributions, and highlighting its importance in CO₂ storage projects. 

Comprehensive Evaluation of Sustainable Treatment Technology of Oily Sludge Based on AHP-FCE

Oil is an unsustainable energy since it is non-renewable. However, oil may not be completely replaced in a short time, so the environmental problems caused by the oil development still require our attention. The oily sludge is a kind of hazardous waste produced during the oil development. To reduce the environmental impact caused by oily sludge, low-carbon and sustainable treatment technologies need to be selected. The incineration, chemical extraction and thermal desorption are common technologies for treatment of oily sludge. We calculated the carbon emissions of these technologies. Then the index evaluation system of oily sludge treatment technology was established with the environmental, economic, social, and technical factors. And the weight of evaluation index was determined by the analytic hierarchy process (AHP). Through the investigation of industry experts, we evaluated the treatment technologies by the fuzzy comprehensive evaluation method (FCE). The results showed that the carbon emissions of incineration are 42.70 t CO₂-eq/t which is the highest. Meanwhile, it is 4.80 t CO₂-eq/t and 0.10 t CO₂-eq/t for chemical extraction and thermal desorption, respectively. The comprehensive scores of incineration, chemical extraction and thermal desorption were 4.59, 5.16 and 4.95, respectively. Therefore, the chemical extraction technology is an optimal treatment technology for oily sludge with the relatively low carbon emission and the highest comprehensive technical score. At the same time, the thermal desorption technology has strong application potential with the lowest carbon emissions. This result provides a reference for achieving clean and sustainable energy development processes.

Supply Chain of Grey-Blue Hydrogen from Natural Gas: A Study on Energy Efficiency and Emissions of Processes

Hydrogen energy offers a significant potential for reducing carbon emissions and integrating clean energy across sectors such as heavy-duty vehicles, energy-intensive industries, and building heating. This study analyzes the energy efficiency and emissions of grey and blue hydrogen supply chains, identifying key issues such as high energy consumption and losses in transportation, steam methane reforming, and liquid hydrogen storage. Truck transportation emerges as the highest emitter, with emissions ranging from 0.140 to 0.150 kg CO_2e per kg of hydrogen. Using a bi-objective Dijkstra Algorithm, the study identifies the most energy-emissions-efficient pathways and reveals a trade-off between energy efficiency and greenhouse gas emissions. Grey hydrogen shows higher energy efficiency (38.0%) but higher emissions (0.1689 kg CO_2e per kg of hydrogen). In contrast, with 60% and 90% carbon capture and storage, blue hydrogen has slightly lower energy efficiencies (37.5% and 36.9%) but reduced emissions (0.1564 and 0.1514 kg CO_2e per kg of hydrogen). Liquefied natural gas and hydrogen offer high energy efficiency but increase emissions, while compressed natural gas and hydrogen slightly reduce efficiency but nearly halve emissions. Hence, compressed options are preferable for an energy-emissions-efficient shortest path.utf-8

Advancing Green Hydrogen Production in Saudi Arabia: Harnessing Solar Energy and Seawater Electrolysis

The transition to clean and sustainable energy sources is crucial for combating the challenges posed by climate change. Green hydrogen, produced through renewable energy-driven electrolysis, holds significant promise as a viable clean energy carrier. The study introduces a system that leverages abundant solar energy and utilizes seawater as the feedstock for electrolysis, potentially offering a cost-effective solution. A comprehensive mathematical model, implemented in MATLAB, is employed to simulate the design and operational efficiency of the proposed green hydrogen production system. The system’s core components include solar panels as a clean energy source, an advanced MPPT charge controller ensuring optimal power delivery to the electrolyzer, and a seawater tank serving as the electrolyte source. The model combines these elements, allowing for continuous operation and efficient hydrogen production, addressing concerns about energy losses and cost-effectiveness. Results demonstrate the influence of solar irradiance on the system’s performance, revealing the need to account for seasonal variations when designing green hydrogen production facilities. Theoretical experiments are conducted to evaluate the behavior of a lithium battery, essential for stabilizing the system’s output and ensuring continuous operation during periods of low solar radiation. utf-8

A Novel High Step-up DC-DC Converter Using State Space Modelling Technique for Battery Storage Applications

This paper focuses a novel non-isolated coupled inductor based DC-DC converter with excessive VG (voltage gain) is analyzed with a state-space modeling technique. It builds up of using three diodes, three capacitors, an inductor and CI (coupled inductor). The main switch S is turn on due to body diode and voltage stress is reduced at the switch S by using diode D1 and Capacitor C1. This paper focuses on design modelling, mathematical calculations and operation principle of DC-DC converter is discussed with state-space modelling technique. The performance has been presented for two different voltages for EV applications, i.e., 12 V, 48 V as input voltages with a high step-up outputs of 66 V and 831.7 V respectively. The converter stability is studied and determined the bode plot along with simulation performance results which are carried out using MATLAB R2022B.utf-8

‘Greening’ an Oil Exporting Country: A Hydrogen and Helium Closed-cycle Gas Turbines Case Study

Holistic decarbonisation requires collaborative efforts and substantial investments across diverse economic sectors. This study introduces an innovative national approach, blending technological insights and philosophical considerations to shape decarbonization policies and practices. Libya is the case study. The proposed framework involves submersible power stations with continuous-duty helium closed-cycle gas turbines to supply electricity demand and hydrogen. Extensive national data is analysed, incorporating factors such as sectoral consumption, sea temperature, and port locations. An analytical model is developed, providing a valuable foundation for realistic decarbonization scenarios. The model aims to maintain the benefits of current energy consumption, assuming a 2% growth rate, while assessing changes in a fully green economy. The results offer qualitative and quantitative insights on hydrogen use and an expected rise in electricity demand. Two scenarios are examined: self-sufficiency and replacing oil exports with hydrogen exports. This study provides a quantitative perspective on decarbonization, focusing on a submersible helium closed cycle gas turbine concept resistant to natural disasters and proliferation. Findings underscore the substantial changes and investments needed for this transition, identifying primary needs of 27 GW or 129 GW for self-sufficiency and exports, respectively. This foundational analysis marks the start of research, investment, and political agendas toward decarbonization.utf-8

Estimate of Economic Impact of EVs Li-ion Batteries Recovery

Nowadays, increasing attention is directed towards the sustainable use of raw materials. For a circular economy, recovery from spent devices represents a fundamental practice. With the transition to electric mobility, an increasing number of devices powered by lithium batteries are produced. Indeed, this is the fastest growing sector producing spent batteries, which are an important secondary source of critical raw materials, such as lithium, cobalt, graphite, and nickel. Therefore, this work aims to quantify the economic impact of recovering raw materials from lithium batteries used in the electric vehicles sector. Based on the chemical composition of the various lithium batteries and their market diffusion, the intrinsic economic value of this waste has been estimated to be around 6500 €/ton. Starting from the literature data on the global energy demand from lithium batteries and deriving the trend of their specific energy over time, the mass of material introduced into the market annually is estimated to reach 60 Mton/year by 2040. The annual amount of end-of-life lithium batteries was calculated by applying the Weibull distribution to describe the probability of failure, yielding 10 Mton/year by 2040. Finally, based on these results, the economic impact of the recovery market was assessed for two different scenarios.utf-8

The “Global Change Data Base” GCDB Facilitates a Transition to Clean Energy and Sustainability

This article presents the opportunities for constructing a global data base picturing underlying trends that drive global climate change. Energy-related CO₂ emissions currently represent the key impact on climate change and thus become here the object of deep, long-term and historiographic analysis. In order to embrace all involved domains of technology, energy economy, fuel shares, economic efficacity, economic structure and population, a “Global Change Data Base” (GCDB) is suggested, based on earlier worldwide accepted data repositories. Such a GCDB works through regressions and statistical analysis of time series of data (on extensive magnitudes such as energy demand, population or Gross Domestic Product, GDP) as well as generation of derived data such as quotients of the former, yielding intensive magnitudes that describe systems and their structural properties. Moreover, the GCDB sets out to compute the first and second time derivatives of said magnitudes (and their percentual shares) which indicate new long-term developments already at very early phases. The invitation to participate in this foresight endeavour is extended to all readers. First preliminary GCDB results quantitatively portray the evolutionary structural global dynamics of economic growth, sectoral economic shifts, the shifts within energy carriers in various economic sectors, the ongoing improvements of energy intensity and energy efficiency in many economic sectors, and the structural changes within agricultural production and consumption systems.utf-8

A Review of Multi-Domain Urban Energy Modelling Data

Urban energy models (UEMs) simulate energy use at the urban scale and are used to inform urban planning, policy development, infrastructure development, and digital twin monitoring and forecasting. Recent technological improvements have spurred interest in large, multi-domain UEMs, which analyse multiple interconnected parts of these energy systems, such as geography, transport, and buildings. Reviews have focussed on single domains or aspects of UEM data. However, multi-domain UEMs require detailed multi-domain data inputs to provide accurate results. This paper provides a comprehensive review of data requirements and a repository of data-specific information for researchers, including data formats, sources, acquisition methods, bridging methods, and challenges. The review was conducted using academic search engines and the authors’ direct research experience. Domains are characterised by Climate, Geographic, Building, Transportation, Demographics, Energy Networks and Consumption, and Distributed Energy Resources. Additionally, challenges common to multiple sectors are identified, and methods for addressing these are proposed. The paper concludes with a series of recommendations drawing from the general and sector-specific challenges. Overall, a large amount of data exists, but their use by urban energy modellers is limited due to lack of coordination and standardisation, and concerns over privacy and commercial interests. Coordinated public effort is required to overcome these limitations and improve the results of UEMs in the future.utf-8

The Interplay between Experimental Data and Uncertainty Analysis in Quantifying CO₂ Trapping during Geological Carbon Storage

Numerical simulation is a widely used tool for studying CO₂ storage in porous media. It enables the representation of trapping mechanisms and CO₂ retention capacity. The complexity of the involved physicochemical phenomena necessitates multiphase flow, accurate fluid and rock property representation, and their interactions. These include CO₂ solubility, diffusion, relative permeabilities, capillary pressure hysteresis, and mineralization, all crucial in CO₂ trapping during carbon storage simulations. Experimental data is essential to ensure accurate quantification. However, due to the extensive data required, modeling under uncertainty is often needed to assess parameter impacts on CO₂ trapping and its interaction with geological properties like porosity and permeability. This work proposes a framework combining laboratory data and stochastic parameter distribution to map uncertainty in CO₂ retention over time. Published data representing solubility, residual trapping, and mineral trapping are used to calibrate prediction models. Geological property variations, like porosity and permeability, are coupled to quantify uncertainty. Results from a saline sandstone aquifer model demonstrate significant variation in CO₂ trapping, ranging from 17% (P10 estimate) to 56% (P90), emphasizing the importance of considering uncertainty in CO₂ storage projects. Quadratic response surfaces and Monte Carlo simulations accurately capture this uncertainty, resulting in calibrated models with an R-squared coefficient above 80%. In summary, this work provides a practical and comprehensive framework for studying CO₂ retention in porous media, addressing uncertainty through stochastic parameter distributions, and highlighting its importance in CO₂ storage projects. utf-8

Mixed Matrix Membranes Produced from a Fluorinated MOF and Pebax for CO₂/H₂ Separation

Hydrogen (H₂) emerges as a promising clean energy source, but its efficient purification from various sources needs advanced separation technologies. This study explores the use of CO₂-selective membranes, especially mixed matrix membranes (MMM) incorporating KAUST-7 metal-organic framework (MOF), for hydrogen purification. The MMM was fabricated with various KAUST-7 content in a polymer matrix (Pebax 1657) and characterized via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and gas permeation tests. The XRD analysis confirms the incorporation of KAUST-7 into the MMM, while SEM reveals a homogeneous particle distribution at low content (below 10%) but agglomeration at higher ones (above 10%). FTIR confirms good interfacial interactions between the MOF and polymer matrix. TGA results show that the MMM thermal stability slightly decreases with increasing MOF content. Gas permeation results reveal improved CO₂ permeability (79%) and CO₂/H₂ selectivity (19%) for MMM compared to neat Pebax membranes, with an optimal performance observed at 10 wt.% KAUST-7. Beyond this threshold, the performance deteriorates, possibly due to polymer rigidity and MOF agglomeration. Overall, the study highlights the potential of KAUST-7/Pebax MMM for enhanced hydrogen purification.utf-8

Reduced Climate Impacts of Dairy Sludge Management by Introducing Hydrothermal Carbonization

Dairies which produce cheese and milk products can, however, produce large volumes of wastewater that require treatment, usually via activated sludge treatment. Disposal of the resulting activated sludge to land is viewed favorably as the sludge is rich in phosphorus (P) and nitrogen (N) and enables nutrient recycling. Nonetheless, sludge management can significantly influence the greenhouse gas (GHG) emissions to the atmosphere. This manuscript has modelled the GHG emissions arising from two sludge management strategies currently adopted by Danish dairies whereby: (i) sludge is stored and later applied to fields; or (ii) sludge is treated by anaerobic digestion (AD), stored, and the digestate will later be applied to fields. This is compared to (iii) an alternative sludge management strategy with treatment by Hydrothermal Carbonization (HTC). HTC is a technologically simple sludge treatment that could lower the cost for dewatering dairy sludge, forming a biochar-like material known as hydrochar. The produced hydrochar can be applied to the land for the purpose of carbon sequestration, P and N recycling. Our calculations indicate that GHG balances of HTC sludge management can result in a net carbon sequestration of 63 kg CO_2eq per ton sludge, as opposed to net emissions of 420 and 156 kg CO_2eq per ton sludge for strategies (i) and (ii), therefore offering significant reductions GHG emissions for the dairy sector.utf-8