Water circularity in Power-to-X: strategies for integrating water reuse into emerging energy systems

Modeling and simulation of Power-to-X systems: A review

The transition to a sustainable energy system is crucial to meet climate targets and reduce fossil fuel dependence. Solar hydrogen systems offer a promising route for renewable hydrogen production. This study presents a techno-economic assessment of hydrogen production using integrated solar hydrogen panels combined with balance-of-plant equipment such as compressors. The analysis combines detailed Aspen Plus process design with an hourly solar model to capture the impact of system scale and hydrogen storage under intermittent operation. Results show that large-scale integrated systems can achieve costs comparable to photovoltaic–electrolyzer setups, suggesting a feasible and streamlined alternative. System scale is the dominant factor influencing the levelized cost of hydrogen (LCOH). At a small scale (1000 panels), the LCOH is about 49 €/kg. Including hydrogen storage reduces costs by up to 40% through better utilization of capital-intensive components. At larger scales, costs decrease substantially: 100,000 panels yield an LCOH of 9.1 €/kg, and 10 million panels reach 7.3 €/kg. In these large systems, storage slightly increases costs because added capital expenditures outweigh operational gains. If solar-to-hydrogen efficiency improves to 23% and panel costs drop to 120 €/m2, hydrogen could be produced at around 3.8 €/kg. These findings emphasize the importance of scale, efficiency gains, and cost reduction to enable affordable renewable hydrogen directly from sunlight and water.

Solar-integrated blue hydrogen production with optimized post-combustion carbon capture: A techno-economic and exergoeconomic assessment

The topic of energy islands is currently a focal point in the push for the energy transition. An ambitious project in the North Sea aims to build an offshore wind-powered electrolyser for green hydrogen production. Power-to-X (PtX) is a process of converting renewable electricity into hydrogen-based energy carriers, such as natural gas, liquid fuels and chemicals. PtH2 represents a subset of PtX, wherein hydrogen is the resultant green energy from the conversion process. Many uncertainties surround PtH2 plants, affecting the economic success of the investment and making the price of hydrogen and the levelized cost of hydrogen (LCOH) of this technology uncompetitive. Several studies have analysed PtH2 layouts to identify the hydrogen price without considering how component capacities and external inputs affect the breakeven price. Unlike previous works, this paper investigates component capacity dependencies under variables such as wind and hydrogen demand shape for dedicated/non-dedicated system layouts. To this end, the techno-economic analysis finds the breakeven price, optimising the components to reach the lowest selling price. Results show that the hydrogen price can reach 2.2 €/kg for a non-dedicated system for certain combinations of maximum demand and electrolyser capacity. Furthermore, the LCOH analysis revealed that the offshore wind electrolyser system is currently uncompetitive with hydrogen production from carbon-based technologies but is competitive with renewable technologies.The sensitivity analysis reveals the green electricity price in the non-dedicated case for which a dedicated system has a lower optimum hydrogen price. The price limit for the dedicated case is 116 €/MWh.

The escalating demand for renewable energy solutions and the imperative for efficient energy storage mechanisms have catalyzed the evolution of Power-to-X (PtX) technologies. Germany has the most PtX projects, accounting for 44% of all projects that have been reported. PtX encompasses a spectrum of processes engineered to convert surplus renewable energy into versatile energy carriers or chemical commodities, such as hydrogen, methane, or synthetic fuels. The Paramount to this domain is to synergistically harness renewable energy sources and hydrogen carriers to curtail waste and bolster sustainability. Central to achieving this synergy is the effective control of PtX processes, ensuring optimal performance, cost efficiency, and seamless integration within existing energy frameworks. This paper delves into the control processes and environmental prerequisites within the PtX landscape, elucidating key challenges, and strategies within this dynamic realm. While providing an initial overview of fundamental PtX process chains, this paper accentuates the critical role of geographical considerations. Subsequently, it conducts a thorough analysis of equipment modeling challenges, addressing performance metrics, operational requisites, and capital investments, particularly focusing on methanol and hydrogen production and storage. Through holistic examination, this paper endeavors to delineate the evolving landscape of PtX control processes and conditions, advancing our understanding of this expanding field.

• Solar-driven power-to-X potential of 30 countries is assessed. • An integrated approach combining MCDM and data-driven optimization is proposed. • The region is analyzed for its resources, economic and environmental factors. • Levelized cost of hydrogen and its derivatives in the region are evaluated. • Life cycle assessment is conducted to evaluate the environmental impact. The use of solar energy to produce key chemicals such as hydrogen, ammonia, and methanol is rapidly gaining momentum as part of the global transition toward cleaner fuel sources. Countries located near the equator, within the global sunbelt, hold significant potential for solar-driven Power-to-X (P-to-X) pathways. This comprehensive study employs advanced Geographic Information System spatial analysis and the Analytical Hierarchy Process (AHP) technique to assess land suitability for solar-powered P-to-X production pathways, including hydrogen, ammonia, and methanol, across 30 countries (hereafter referred to as the ’macro-region’). The results indicate that water availability is the most critical constraint, rendering 57% of the land unsuitable. Overall, the AHP results reveal that only 3.8% of the entire macro-region is highly suitable, while 44.6% is moderately suitable for solar-driven hydrogen facilities. A two-stage data-driven predictive model is utilized to assess the hydrogen production potential and levelized cost of hydrogen (LCOH) and other derivatives for highly suitable areas in 2024 and 2050 under various cases. The results indicate that by 2050, the macro-region has the potential to achieve a hydrogen production of up to 1,590 Mt/y, while simultaneously avoiding approximately 16,589 Mt/y of CO 2 emissions if all highly suitable land is effectively utilized. By 2050, the LCOH is projected to decrease to between 2.56–4.17 $/kg, while the costs of green ammonia and methanol are anticipated to range from 0.56 to 0.79 $/kg and 0.67–0.93 $/kg, respectively. Although this study highlights the region’s remarkable potential for power-to-X technologies, effective deployment and distribution will depend on regional cooperation, robust infrastructure development, and strategic measures—such as seawater desalination—to overcome critical water scarcity constraints.

Multi-criteria framework for rainwater-to-hydrogen systems in tropical residential energy transitions

The present paper evaluates the composite risk of anthropogenic and climate change on the future water status in Jordan during the period 2030–2050. The projected water status in the country is evaluated based on the more likely population growth and climate change scenarios. The most likely figure for the population of Jordan, excluding refugees from neighboring countries, in 2040 would be ∼15 million people. Given this likely projection, though conservative, annual water needs for the domestic sector alone are expected to be between 700 and 800 million m3, with the current level of water consumption. A rise in near surface air temperature by 2 °C and a drop in total precipitation by 15%, as projected by most Global Circulation Models, would diminish renewable water resources in the mountainous region by ∼ 25–40%, being more severe as aridity increases.1. IntroductionThere is almost a consensus among earth scientists that the buildup of greenhouse gases in the atmosphere is lea...

Techno – Economic assessment of flexible decarbonized hydrogen and power co-production based on natural gas dry reforming

This work explores the integration of Proton Exchange Membrane (PEM) electrolysis waste heat with district heating networks (DHN), aiming to enhance the overall energy efficiency and economic viability of hydrogen production systems. PEM electrolysers generate substantial amounts of low-temperature waste heat during operation, which is often dissipated and left unutilised. By recovering such thermal energy and selling it to district heating systems, a synergistic energy pathway that supports both green hydrogen production and sustainable urban heating can be achieved. The study investigates how the electrolyser’s operating temperature, ranging between 50 and 80 °C, influences both hydrogen production and thermal energy availability, exploring trade-offs between electrical efficiency and heat recovery potential. Furthermore, the study evaluates the compatibility of the recovered heat with common heat emission systems such as radiators, fan coils, and radiant floors. Results indicate that valorising waste heat can enhance the overall system performance by reducing the electrolyser’s specific energy consumption and its levelized cost of hydrogen (LCOH) while supplying carbon-free thermal energy for the end users. This integrated approach contributes to the broader goal of sector coupling, offering a pathway toward more resilient, flexible, and resource-efficient energy systems.

Juba, the capital city of South Sudan while, presenting a unique case as a rapidly growing city in a post-conflict country, its water infrastructure has been severely affected by decades of conflict, leaving it inadequate and underdeveloped. This study was conducted with the main objective of establishing factors causing the inadequacy of clean and safe water among households in Juba City. This study employed a proposed AA-QQ-RD (Availability, Affordability, Quality, Quantity, Reliability, and Distance) framework. The research employed a qualitative methodology, gathering data through in-depth interviews, Focus Group Discussions (FGDs), and Key Informant Interviews (KIIs) with household heads, government officials, and community leaders. The findings reveal significant challenges across all components of the AA-QQ-RD model. Availability of water is severely impacted by poor infrastructure which collectively disrupt water distribution while affordability issues arise from the high cost of water. In addition, water quality is compromised at multiple stages posing serious health risks while quantity of water is insufficient, particularly in larger households and densely populated areas. Further, reliability is undermined by irregular water supply and frequent service interruptions whereas distance to the nearest water points is a significant barrier with many residents traveling long distances to fetch water. These findings underscore the need for comprehensive infrastructural improvements, effective regulatory frameworks, and community-driven initiatives to address these barriers. The study's implications for Sustainable Development Goal 6 (SDG 6) highlight the critical need for coordinated efforts to ensure the availability and sustainable management of water and sanitation for all.

Introduction: Sustainable Development Goal (SDG)-6 highlights the importance of clean water and sanitation. The Swachh Bharat Mission, a flagship program of the Government of India, aims at ensuring the availability and sustainable management of water, hygiene, and universal access to effective systems for disposing of waste, especially in rural areas; this, in turn, is of mammoth importance for achieving the SDG-6 by 2030. The present study was thus devised to determine the availability of sanitation facilities and assess the knowledge, attitude, and practices regarding hygiene among residents of villages in Southeastern Maharashtra. Materials and Methods: This community-based study used a multistage sampling technique to select study participants. The duration of the study was one month. The study involved 1663 participants. A Marathi-translated version of the pretested questionnaire was used, which enquired about the socio-demographic details, availability of water and sanitation facilities along with questions to assess the knowledge, attitude, and practice regarding sanitary latrines, use of footwear, hand washing, and domestic waste disposal. Association of socio-demographic profile with different parameters assessed in the questionnaire was assessed using SPSS software (version 26.0); results were considered significant if p<0.05. Results: The study involved 1663 participants with a mean age of 36.7 years, (SD=12.9 years). Water was available to all the households. All the villages had an open drainage system. Sanitation facilities were lacking in 23 households. Open-air defecation was practiced in 6.9% of the households. All the family members used footwear while going out in 68% of the households. Hand-washing was practiced by 43% of the population. Sixty-nine percent of the study participants disposed of domestic waste in the garbage pits dug in their backyard which was later burnt, whereas 31% disposed of in the surrounding premises. Conclusion: Open defecation still exists. The awareness regarding sanitation, footwear use, hand washing, and domestic waste disposal was better among literate participants. With just a few years left to the 2030 deadline to achieve the SDGs, we must inject a sense of urgency and immediately accelerate our actions at the individual and community levels.

The 2030 Agenda for Sustainable Development includes Goal 6 (SDG 6): ‘Ensure availability and sustainable management of water and sanitation for all’. SDG target 6.1 aims to achieve by 2030 ‘universal and equitable access to safe and affordable drinking water for all’. The Government of India has also launched the Jal Jeevan Mission (JJM) to provide potable tap water to every rural household by 2024. In this context, this article explains the findings of a study to assess the domestic water demand and the availability of water in seven villages in the Ballari and Raichur districts in North Karnataka. This study indicates that groundwater is predominantly used for domestic purposes in these districts due to the lack of adequate and reliable surface water. Only 14% of households in the study area receive adequate water as per the JJM norms and this water stress is projected to worsen due to the increasing supply–demand mismatch in the future. The authors recommend the implementation of the revised configuration of the Krishna (Almatti)–Pennar river interlinking project by 2030 since this alignment is optimised to reduce project-related deforestation, people displacement, project duration and costs. This is critical for the sustainable development of North Karnataka.

Core of most Power-to-X (PtX) concepts is the utilization of renewable electricity to produce hy-drogen via water electrolysis. This hydrogen can be used directly as final energy carrier or can be converted further into e.g. methane, synthesis gas, liquid fuels, electricity or chemicals. To inte-grate PtX into energy systems, technical demonstration and systems integration are of major im-portance. In total 220 PtX research and demonstration projects to analyze these issues have been realized, are already finished or in the planning in Europe by June 2020. Key issue of this review is the identification and assessment of relevant projects regarding year of commissioning, location, electricity and carbon dioxide sources, applied technologies for electrolysis, capacity, type of hy-drogen post-processing, as well as the aimed field of application. Latter changed over the years. At the beginning, it was fuel production, e.g. for hydrogen busses, and combined heat and power gen-eration, later injection into the natural gas grid. Today industrial applications and once again fuel production are important applications. Focus for the fuel production is synthetic gaseous fuels, while production of liquid fuels is severely under-represented. The SOEC (solid oxide electrolyzer cell) has a very small share in projects compared to PEM (polymer electrolyte membrane) and alka-line electrolyzers. This is also reflected by the different installed capacities. While alkaline electro-lyzers are installed with capacities between 50 and 5000 kW (2019/20) and PEM electrolyzers be-tween 100 and 6000 kW, SOEC have a size of 150 kW. France and Germany show the biggest ef-forts into the development of PtX technologies compared to other European countries. Overall, ac-tivities have progressed considerably faster than predicted just a couple of years ago.

This article challenges the view that zero carbon hydrogen from steam methane reforming (SMR) is prohibitively expensive and that the cost of CO2 capture increases exponentially as residual emissions approach zero; a flawed narrative often eliminating SMR produced hydrogen as a route to net zero. We show that the capture and geological storage of 100% of the fossil CO2 produced in a SMR is achievable with commercially available post-combustion capture technology and an open art solvent. The Levelised Cost of Hydrogen (LCOH) of 69£/MWhth HHV (2.7£/kg) for UK production remains competitive to other forms of low carbon hydrogen, but retains a hydrogen lifecycle carbon intensity of 5 gCO2e/MJ (LHV) due to natural gas supply chain and embodied greenhouse gas (GHG) emissions. Compensating for the remaining lifecycle GHG emissions via Direct Air Capture with geological CO2 Storage (DACCS) increases the LCOH to 71–86 £/MWhth HHV (+3–25%) for a cost estimate of 100–1000 £/tCO2 for DACCS and the 2022 UK natural gas supply chain methane emission rates. Finally, we put in perspective the cost of CO2 avoidance of fuel switching from natural gas to hydrogen with long term price estimates for natural gas use and DACCS, and hydrogen produced from electrolysis.