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This study introduces an innovative solution to address the challenges arising from the volatile natural gas market and the growing integration of renewable energy sources within the industrial sector. The research strives to confront this challenge by including renewable methanol (CH3OH) and converting it into methane (CH4), with an intermediate step involving synthesis gas (CO/H2) by using concentrating solar power. This approach provides a sustainable and adaptable solution to reduce dependence on natural gas. The process entails a methanol decomposition reaction at moderate temperatures (<350 °C). Subsequently, the synthesis gas is compressed to 40 bar, stored, and discharged through a methanation process that can be conducted at high temperatures (>500 °C). The resulting methane is used as fuel for gas turbines and can also serve as feedstock in the chemical industry. The simulations were conducted in ASPEN HYSYS and yielded overall system efficiencies exceeding 29% and roundtrip efficiencies of 44%. Through techno-economic optimisation of the reaction conditions, competitive levelized fuel costs (LCOF) of €172/MWh and future LCOE values of €145/MWh were achieved. These findings present an innovative strategy for integrating gas turbine cycles and additional conversion pathways for green methanol.

The security of the supply of clean energy resources and the production of renewable fuels for industry are some of the strategies to combat climate change. In this sense, the massive implementation of green fuels that is foreseen forces the industrial park to operate on hydrogen and/or ammonia, methanol and others, with a cost overrun for stakeholders. This work proposes an alternative through a methanol-to-methane conversion system from the intermediate step to synthesis gas. Methanol decomposition is a process that can be produced with solar energy (CSP) at moderate temperatures (<350 °C) and at low cost, whereas methanation is a well-known and industrially mature process that occurs at temperatures < 625 °C. The integration of both processes is employed as a method of solar storage, namely through high-pressure syngas and its discharge for power production in conventional cycles. Recuperative ORC configurations, Rankine steam, and a sCO2 Brayton cycle were integrated; all of them of techno-economic interest, offering round-trip efficiencies higher than 50 % and levelized costs (LCOE) lower than EUR 55/MWh, considering a high-energy methane stream at the outlet. This offers a system that proposes a solution for the massive deployment of methanol as a green hydrogen carrier molecule, where it is capable of cleanly and efficiently storing thermochemical energy and producing high-purity methane at the output, usable in other power cycles, or as an industrial feedstock.

La intermitencia del recurso renovable conduce cada vez más a la necesidad de implementar sistemas de almacenamiento de energía, que aseguren el suministro energético y evitar los denominados curtailments. En este trabajo se desarrolla un sistema de almacenamiento de energía termoquímico, integrado a un sistema de energía solar de concentración (CSP) para promover la reacción de descomposición del amoníaco, para su posterior almacenamiento a alta presión en forma de gas de síntesis. Cuando así lo requiera la demanda, se liberará el syngas en la fase de descarga, produciendo amoníaco y liberando calor que podrá ser aprovechado para distintos usos, como será ha discutido. El sistema propuesto en el punto nominal de operación alcanza un rendimiento térmico del 50% y un rendimiento de conversión de energía solar a química del 46%, ofreciendo 8 horas de almacenamiento. Los costes nivelados de almacenamiento alcanzan valores de 130 €/MWh, siendo competitivo respecto a otras tecnologías de almacenamiento de su misma tipología. La flexibilidad del sistema permite la integración de un bloque de potencia a media temperatura compuesto por un ciclo de Rankine o un ORC, así como para la producción de calor de distrito., The intermittency of the renewable resource increasingly leads to the need to implement energy storage systems to ensure the energy supply and avoid the so-called curtailments. In this work, a thermochemical energy storage system is developed, integrated to a concentrating solar power system (CSP) to promote the ammonia decomposition reaction, for its subsequent storage at high pressure in the form of synthesis gas. When required by demand, syngas will be released in the discharge phase, producing ammonia, and releasing heat that can be used in different ways, as discussed. The proposed system at nominal operating point achieves a thermal efficiency of 50% and a solar to chemical energy conversion efficiency of 46%, providing 8 hours of storage. The levelized storage costs reach values of 130 €/MWh, being competitive with other storage technologies of the same type. The flexibility of the system allows the integration of a medium temperature power block composed of a Rankine cycle or Organic Rankine cycle, as well as for district heat production.

Thermal energy storage systems are an emerging option for efficient energy conversion and storage, especially if they can concentrate solar energy. This work studies a flexibleCH₃OH-to-CH₄ conversion system from intermediate conversion to synthesis gas. The design is based on a combination of processes already tested experimentally and applied in industry. The concept we develop integrates the decomposition of CH₃OH and methanation processes, providing different pathways for energy use, such as natural gas, direct heat, and power supply, or storage in chemical bonds. This flexibility in adapting the operation of the system to different energy availability and energy needs makes the concept appealing for changeable application. Thermal efficiencies of 39% are possible for the CH₃OH decomposition phase and of 26% for the overall system for CH₄ production. Thus, from the high energy density of CH₃OH, levelized storage costs of €134.8/MWh can be obtained, which is lower than systems based on molten salts. These results should spur interest in further advances for the proposed flexible concept.

With the increasing volatility in natural gas markets and the need for residential heat, research for alternative fuels is necessary for several regions. This paper presents a high-duration thermochemical energy storage system (TCES) based on methanol, evaluating its integration with district heating networks, offering a renewable solar-based storage solution and low-temperature heat generation from the exothermic discharge reaction heat. The system eliminates greenhouse gas emissions by using concentrated solar thermal energy to decompose methanol into synthesis gas. Applying the optimised operational thermodynamic parameters, it is possible to satisfy the thermal demand of 892 households in Spain through 12 MW of concentrated solar energy supported by 10 hours of energy storage. Storage efficiencies exceeding 30% and chemical conversion efficiencies exceeding 65% have been demonstrated, resulting in a combined efficiency of 55% for the heating network and methanol TCES. The results show a levelized cost of storage (LCOS) highly competitive with other storage systems (<100 €/MWh), given the simplicity and flexibility of the proposed system.

Among the portfolio of energy systems for local power generation, Organic Rankine cycles (ORCs) for residential applications are an opportunity for local cogeneration based on synergies with existing thermal heating and storage systems. They can be highly competitive for isolated installations and the refurbishment of existing solar heating installations based on solar domestic hot water. This article evaluates the potential for hybrid solar ORC integration in residential buildings. The analyses focus on the annual yields of a domestic 1 kW ORC cycle to assess the advantages and disadvantages of the variation of demand and the availability of solar resources. The models are developed, integrating TRNSYS and EES to allow a detailed evolution characterisation. Performance and impact of CHP adaptation are considered based on demand, storage volume-collectors area ratio, and production strategies. The analysis is completed with a thermo-economic analysis under different ranges of thermodynamic parameters. Positive IRR results of 8.61% are obtained for the installation located in Seville, Spain, operating the ORC 15% of the year. It also reduces the overheating associated with the lack of heat demand and excess solar irradiation in the solar system for the warm months by 20%.

La transición energética ha tomado las energías renovables como pilar, a pesar de las restricciones de variabilidad climática con las que cuenta. El uso de sistemas de almacenamiento termoquímico se plantea como una opción de vital interés para escenarios futuros de gestión de la demanda y el suministro de energía eléctrica a red. En este trabajo se plantea el estudio de un sistema basado en metanol altamente flexible que hace uso de reacciones de metanación y desplazamientos para la producción de gas natural sintético. Se propone también un modelo basado en la conversión de metano a metanol, para completar el ciclo. En ambas rutas se podrá extraer potencia a partir de la combustión del gas natural producido a partir de un ciclo Joule-Brayton, así como aprovechar la potencia procedente de las reacciones exotérmicas en ciclos orgánicos de Rankine regenerativos. Se obtienen así rendimientos globales de conversión del 50 % para la ruta CH3OH-CH4 y del 43 % en la ruta CH4-CH3OH, a partir de ocho horas de almacenamiento en cada caso. Los costes nivelados de energía resultan de 0.10 €/kWh y 0.15 €/kWh, respectivamente. La integración del bloque de potencia con la configuración propuesta indica rendimientos para una turbina de gas de 100 MW del 35 % y del 10.5 % para ORC de 450 kW que usa Tolueno como fluido de trabajo., Energy transition has taken renewable energies as a pillar, despite the constraints of climate variability. The use of thermochemical storage systems is considered as an option of vital interest for future demand and supply management scenarios of electricity to grid. This work studies a highly flexible methanol-based system that makes use of methanation reactions and shifts for the production of synthetic natural gas. A model based on methane to methanol conversion is also proposed to complete the cycle. In both routes, power can be extracted from the combustion of natural gas produced from a Joule-Brayton cycle, as well as recovering residual energy from the exothermic reactions in regenerative organic Rankine cycles. Overall conversion efficiencies of 50 % for CH3OH-CH4 route and 43 % for CH4-CH3OH route are obtained, from eight hours of storage in each case. The levelised energy costs are 0.10 €/kWh and 0.15 €/kWh, respectively. The integration of the power block with the proposed configuration indicates efficiencies for a 100 MW gas turbine of 35 % and 10.5 % for a 450 kW ORC using toluene as the working fluid.

El crecimiento de la demanda eléctrica y térmica en el sector residencial se debe principalmente a un estado de bienestar cada vez más exigente. Dentro de la cartera de sistemas energéticos para la generación de energía local, los ciclos orgánicos de Rankine son una oportunidad de sinergias con los sistemas de calefacción y almacenamiento térmico existentes. Los sistemas ORC en el sector residencial son de especial interés para instalaciones aisladas y para la rehabilitación de instalaciones de calefacción solar basadas en agua caliente sanitaria (ACS). Este tipo de instalaciones está muy extendido en algunas regiones del sur de Europa como España. Este trabajo evalúa el potencial de la integración solar híbrida ORC en edificios residenciales. Los análisis se centran en los rendimientos anuales de un ciclo ORC de 1-3 kW en combinaciones de los dos sistemas: Solar con y sin Almacenamiento. Los modelos se desarrollan integrando TRNSYS y EES para permitir una caracterización detallada de la evolución. El rendimiento y el impacto de las integraciones se consideran en función de la integración, las características de los componentes, el fluido de trabajo y las estrategias de control para un conjunto de zonas climáticas diferentes. Los análisis se completan con un análisis económico basado en las demandas características para diferentes características de la demanda integrada (edificios residenciales, bloques y edificios terciarios). Los resultados obtenidos muestran los rangos de viabilidad para diferentes escenarios de costes de sistemas y zonas climáticas., The growth in electricity and thermal demand in the residential sector is mainly due to an increasingly demanding welfare state. Among the energy systems portfolio for local power generation, Organic Rankine Cycles are an opportunity for synergies with existing thermal heating and storage systems. ORC systems in the residential sector are of particular interest for isolated installations and the refurbishment of solar heating installations based on solar domestic hot water (SDHW). This kind of installations is widely extended in some regions of southern Europe like Spain. This paper evaluates the potential for hybrid ORC solar integration in residential buildings. The analyses are focused on the annual yields of a 1-3 kW ORC cycle in combinations of the two systems: Solar with and without Storage. The models are developed, integrating TRNSYS and EES to allow a detailed evolution characterisation. The performance and the impact of the integrations are considered as a function of the integration, components characteristics, working fluid and control strategies for a set of different climatic zones. The analyses are completed with an economic analysis based on the characteristic demands for different integrated demand characteristics (residential buildings, blocks, and tertiary buildings). The results obtained show the viability ranges for different systems costs scenarios and climatic zones.