Power-to-gas Systems Research Articles

Adaptive robust self‐scheduling for a wind‐based GenCo equipped with power‐to‐gas system and gas turbine to participate in electricity and natural gas markets

AbstractIntegrating renewable energy, particularly wind generation, into power systems brings significant uncertainty and intermittency, challenging generation companies (GenCos) to maintain economic operations. This paper proposes a strategy for a wind‐based GenCo equipped with a gas turbine and a power‐to‐gas (PtG) system to balance wind variability. The gas turbine offsets power shortfalls by consuming natural gas, while the PtG system absorbs excess wind energy, converting it to natural gas and injecting it into the natural gas network as a form of storage. The GenCo operates in day‐ahead electricity and natural gas markets and the real‐time electricity market, addressing uncertainties from wind output, energy prices, and natural gas access. A tri‐level adaptive robust optimization model is introduced for the GenCo’s short‐term operational scheduling. At the first level, decisions related to the GenCo's participation in the day‐ahead electricity and natural gas markets are made. The second level deals with determining the worst‐case realization of the uncertainties, constrained by the budget of uncertainty and the limited range of variations of uncertain variables. The third level sets the operational strategy on the actual day, considering power and gas balance, as well as constraints for the wind farm, gas turbine, and PtG unit. A column & constraint generation (C&CG) algorithm is used to solve the model. Numerical results demonstrate the model’s effectiveness in various case studies, showing that the GenCo can manage wind uncertainties, benefit from arbitrage opportunities in electricity and gas markets, and improve economic outcomes. This approach supports the broader integration of renewable energy into power systems.

Techno-Economic Energy Optimization of the Off-Grid Electrical System with Power to Gas Storage Technology

Renewable energy sources (RESs) have undeniable advantages over the recent years not only to supply electrical demand but also electrical demand. However, maximum use of the RES’s power has always been challenging as high penetration of the RESs as well as their intermittent nature might compromise the distribution networks power flow constraints. This paper proposes optimal energy operation of the off-grid distribution network (DN) with participation of the power-to-gas (PtG) storage system. In this regard, PtG system is considered as an energy supplier in the DN. The natural gas generated by using PtG is applied to backup diesel generators for meeting demand at peak times. The objective functions in the system are modeled based on technical and economic modeling including minimize the operation cost and maximize the system reliability. The optimal energy operation in the two case studies is assumed considering non-participation and participation of the PtG system. To solving of the energy optimization, particle swarm optimization algorithm is proposed. Finally, proposed case studies under numerical simulation are implemented for validation of the participation of the PtG system.

Risk-assessment of carbon-dioxide recycling in a gas-fired power plant using CVaR-based convex optimization

With the rise of renewable resources’ penetration, the use of clean excessive renewable energy as the primary source of a Power to Gas (PtG) system for the reduction of CO2 pollution is quite advantageous. This paper presents a mixed integer linear formulation for modeling the optimal operation of a gas-fired power plant (GFPP)-PtG system that utilizes an excessive renewable resource, wind power, as the primary mover of the proposed PtG system for capturing and recycling the produced CO2 pollution. CO2 and CH4 gas storages are considered in the proposed PtG system to boost the operational efficiency of the system. Additionally, the scenario generation method models both wind power generation and electrical demand. The effective conditional value at risk (CVaR) method, which is a convex risk modeling approach, models the risks imposed by the generated scenarios for wind power and electrical demand. Due to the convexity of the proposed formulation for the PtG system and the risk modeling method, the ultimate model can be simply solved by using any available LP solver. To evaluate the outcomes of an optimization problem based on CVaR, a comparative analysis is conducted with chance constraints programming, which demonstrates the optimality and computational efficiency of the CVaR results due to convexity. The effectiveness of the proposed model is approved by modeling a test system based on real data, and the obtained numerical results are discussed comprehensively.

Process simulation and energy analysis of synthetic natural gas production from water electrolysis and CO2 capture in a waste incinerator

Power-to-gas (PtG) and carbon capture and utilisation are expected to play a key role in promoting a sustainable energy transition. In this work, a detailed energy analysis of a complete PtG system integrated with a real waste incinerator is performed. A fraction of the renewable electricity and heat produced by the waste incinerator is used in the PtG system to produce hydrogen, which is further converted into SNG by methanation with CO2 recovered from the plant flue gases. A PtG plant able to produce up to 500 m3/h of SNG is considered. A total of six different plant configurations are analysed, obtained by the combination of different electrolysis and post-combustion carbon capture technologies. Specifically, alkaline and PEM electrolysers are considered for the production of hydrogen, while absorption with monoethanolamine solution, absorption with monoethanolamine and ionic liquid solution, and temperature swing adsorption with solid sorbent are selected for carbon capture. The main sections of the PtG system are modelled and the performance of the overall system is evaluated by computing key performance indicators, such as the global energy efficiency and the Specific Plant Energy Consumption for CO2 Avoided (SPECCA). Special attention is also paid to the thermal integration between the methanation unit and the carbon capture unit. The heat produced during the methanation process is sufficient to cover the entire heat demand of the CO2 capture unit in almost all configurations investigated. In particular, thermal integration increases the global energy efficiency by 5–9% and reduces the SPECCA indicator by 5–8%. Considering the thermally integrated configurations, the global energy efficiency is estimated to be between 44.6% and 46.7%, while the SPECCA value ranges from 40.5 MJ/kg to 42.4 MJ/kg. Finally, some technical considerations are given, including the quality of SNG produced and the degradation phenomena in the considered technologies.

Economic assessment of hydrogen production in a Renewable Energy Community in Italy

Renewable Energy Community (REC) is a new paradigm in European Union to produce, transform, share and sell renewables at a local consumer level, also via e-fuel (i.e. hydrogen). This work investigates the economic feasibility of a hydrogen Power-to-Gas (PtG) system realized inside a REC, using only excess renewable electricity, not consumed by REC itself. A single centralized photovoltaic (PV) plant is directly connected to an electrolyser; a hydrogen compressor and two hydrogen storages at low and high pressure complete the PtG system. A scenario of a REC composed by 450 residential electric users (around 1,000 people) has been analysed, coupled with described PtG considering eight different sizes of PV plant. In the study, Italian subsidies to REC shared energy are evaluated as incentives to hydrogen production. An optimal size of PtG components for each PV size is investigated at the limit of economical sustainability, evaluating net present value (NPV) positive and near zero. Results show that for the considered REC, it is possible to produce and sell up to around 3 tons per year of green hydrogen at most to the same lowest selling price declared currently in the Italian market (5 €/kg).

Potential Evaluation of Power-to-Gas system by using Wind Turbine and PEM

The Power-to-Gas (PTG) is one of the progressing technologies that enables the conversion of electrical energy into hydrogen or methane gas. This study focuses on the comprehensive analysis of energy efficiency, exergy efficiency, and exergy destruction rate within the PTG overall system. The investigation covers the evaluation of the wind turbine for power generation, the proton exchange membrane (PEM) employed in hydrogen production, and the methanation unit dedicated to methane production. The analysis examines the overall system as well as each individual component. By quantifying the energy and exergy efficiencies, this study provides potential improvements for maximizing the PTG system's overall effectiveness. The outcomes of this study contribute to the advancement and deployment of PTG technologies, thereby facilitating the integration of renewable energy sources and promoting sustainable energy solutions.

Power-to-gas as an option for improving energy self-consumption in renewable energy communities

Renewable Energy Communities (RECs) have been introduced by the Renewable Energy European Directive (REDII) in order to allow their members to collectively produce, consume, store and sell renewable energy. With the distributed generation deployment, the electricity injection into power grids has to be limited. Thereby, the RES management has to maximise the local energy self-consumption (SC). The present work deals with Power-to-Gas (PtG) application for blending hydrogen in the local gas grid for maximising the energy-SC, comparing it with traditional electric batteries (PtP). Moreover, this study investigate how SC-based tariffs for RECs can represent an indirect incentive for hydrogen production. To do so, a case study, consisting of 200 dwellings, has been analysed. Four PV configuration have been considered for evaluating different RES excess conditions. PtP and PtG systems have been implemented and compared each other. The hydrogen production cost has been assessed exploiting the renewable electricity incentive scheme.

Reversible Power-to-Gas systems for energy conversion and storage

In the transition to decarbonized energy systems, Power-to-Gas (PtG) processes have the potential to connect the existing markets for electricity and hydrogen. Specifically, reversible PtG systems can convert electricity to hydrogen at times of ample power supply, yet they can also operate in the reverse direction to deliver electricity during times when power is relatively scarce. Here we develop a model for determining when reversible PtG systems are economically viable. We apply the model to the current market environment in both Germany and Texas and find that the reversibility feature of unitized regenerative fuel cells (solid oxide) makes them already cost-competitive at current hydrogen prices, provided the fluctuations in electricity prices are as pronounced as currently observed in Texas. We further project that, due to their inherent flexibility, reversible PtG systems would remain economically viable at substantially lower hydrogen prices in the future, provided recent technological trends continue over the coming decade.

Economic Evaluation of Implementation of Power-to-Gas: Application to the Case of Spain

An economic analysis of the implementation of the power-to-gas (PtG) system between 2030 and 2055 is presented at a large scale. The capacity of the PtG system is adapted to two scenarios in Spain (Bailera and Lisbona 2018), corresponding to growing scenarios of 1.73 and 1.36%/y of its electricity market. The total power capacity of the PtG system has been fixed to 12.7 and 3.84 GW, respectively, at the end of 2055. The levelized cost of storage (LCOS) of the implementation of PtG has been evaluated. Assuming uncertainties in the current cost projections for CAPEX and OPEX, LCOS estimations are between 136 and 686 EUR/MWh with a payback time of 16 years in the best scenario for a reference electricity purchase of 100 EUR/MWh and a CO2 penalty of 100 EUR/ton. A sensitivity analysis and the viability dependence versus energy purchase and CO2 penalty certificates is shown. This work sheds some light for the comparison of PtG implementation costs in comparison with other storage options, such as batteries, pumped-storage hydroelectricity or compressed air storage for future energy scenarios.

CO2 Reutilization in the Residential Sector Through Power to Gas and Oxyfuel Combustion

A novel concept of Power-to-gas (PtG) has been investigated as a versatile technology for storage and utilization of carbon dioxide coming from energy installations. The proposed PtG solution takes advantage of the synergies of different processes to integrate energy storage efficiently with carbon utilization to produce a ‘CO2 neutral’ natural gas. PtG converts surplus electricity into synthetic natural gas by combining H2 from water electrolysis and CO2 through methanation reaction and oxyfuel combustion. This carbon capture option releases thermal energy from the synthetic fuel producing a near-pure stream of CO2 that close the carbon loop used for methanation. Under this framework, the present work proposes to study and validate the hybridization between Power-to-Gas energy storage technology and CO2 oxyfuel combustion in the residential sector. This combination is a novel strategy focused on solving: (i) the intermittent and seasonal electricity generation from renewable resources; (ii) the large energy and economic penalties associated with CO2 capture and utilization (especially at small scale); (iii) and the development of energy storage systems of small-medium size and high flexibility. This hybridization allows managing the excess of renewable electricity in the Power-to-Gas installation and producing hydrogen (stored energy) and oxygen (by-product). Subsequently, oxygen is used to meet the needs of the oxyfuel combustion process, in this case, in the residential sector, with two important advantages: a high concentration CO2 flow is obtained, and the oxygen production neither requires an air separation unit (ASU) nor additional energy requirements. The stored hydrogen and the captured carbon dioxide are combined by methanation to produce synthetic natural gas stored for future uses. From CO2 capture point of view, the proposed hybrid system presents an additional advantage: there would also be no penalty associated with the compression and underground storage of captured CO2, since it is reused in the oxyfuel burner along with the oxygen, obtained in the electrolyzer, closing the carbon cycle. A PtG installation with recycled CO2 utilization has been designed to fully supply the thermal heating demand and partially the electrical demand of a single-family house located in the northeast of Germany, from a photovoltaic generator. The PtG system's characteristics, the CO2 storage and utilization strategy, the equipment necessary and energy balances are presented and illustrated with a case study. The proposed design can supply the 87% of the energy consumed by a single-family home and avoid the emissions of 2.8 tons of CO2 every year.

Energy Conversion and Storage: The Value of Reversible Power-to-Gas Systems

In the transition to decarbonized energy systems, Power-to-Gas (PtG) processes have the potential to connect the existing markets for electricity and hydrogen. Specifically, reversible PtG systems can convert electricity to hydrogen at times of ample power supply, yet they can also operate in the reverse direction to deliver electricity during times when power is relatively scarce. Here we develop a model for determining when reversible PtG systems are economically viable. We apply the model to the current market environment in both Germany and Texas and find that the reversibility feature of unitized regenerative fuel cells (solid oxide) makes them already cost-competitive at current hydrogen prices, provided the fluctuations in electricity prices are as pronounced as currently observed in Texas. We further project that, due to their inherent flexibility, reversible PtG systems would remain economically viable at substantially lower hydrogen prices in the future, provided recent technological trends continue over the coming decade.

Significance of methanation reactor dynamics on the annual efficiency of power-to-gas -system

Power-to-gas (PtG) is one option to integrate more renewable electricity production to the energy system, by offering flexible load, seasonal energy storage and low-GWP (Global Warming Potential) methane. The first step of the PtG process, hydrogen production by water electrolysis, requires electricity with low specific CO2 emissions. Therefore, the operation of electrolyser is most likely variating according to the intermittency of renewable electricity production.The downstream processes of PtG should be capable to follow the dynamics and utilize the produced hydrogen, avoiding curtailment. This could be done with a very dynamic reactor system, or with aid of buffer storages for feed gases.This paper studies the effect of dynamic properties of methanation reactor, hydrogen buffer storage and electrolyser full load hours on PtG system efficiency. The operation of electrolyser is following intermittent renewable electricity production and electricity markets, leading to varying full load hours (FLH) with different characteristics.Enhancement of single parameters related to thermal dynamics of the reactor could improve the system efficiency more than parameters related to the loading of the reactor. Coupled threshold were found for FLH and H2 storage size, after which average efficiencies became nearly similar as in steady-state operation.

Calculation and analysis of efficiencies and annual performances of Power-to-Gas systems

This paper describes a generic and systematic method to calculate the efficiency and the annual performance for Power-to-Gas (PtG) systems. This approach gives the basis to analytically compare different PtG systems using different technologies under different boundary conditions. To have a comparable basis for efficiency calculations, a structured break down of the PtG system is done. Until now, there has not been a universal approach for efficiency calculations. This has resulted in a wide variety of efficiency calculations used in feasibility studies and for business-case calculations. For this, the PtG system is divided in two sub-systems: the electrolysis and the methanation. Each of the two sub-systems consists of several subsystem boundary levels. Staring from the main unit, i.e. the electrolysis stack and/or methanation reactor, further units that are required to operate complete PtG system are considered with their respective subsystem boundary conditions.The paper provides formulas how the efficiency of each level can be calculated and how efficiency deviations can be integrated which are caused by the extended energy flow calculations to and from energy users and thermal losses. By this, a sensitivity analysis of the sub-systems can be gained and comprehensive goal functions for optimizations can be defined.In a second step the annual performance of the system is calculated as the ratio of useable output and energetic input over one year. The input is the integral of the annual need of electrical and thermal energy of a PtG system, depending on the different operation states of the plant. The output is the higher heating value of the produced gas and – if applicable – heat flows that are used externally.The annual performance not only evaluates the steady-state operating efficiency under full load, but also other states of the system such as cold standby or service intervals. It is shown that for a full system operation assessment and further system concept development, the annual performance is of much higher importance than the steady-state system efficiency which is usually referred to.In a final step load profiles are defined and the annual performance is calculated for a specific system configuration. Using this example, different operation strategies are compared.

Coordination of battery energy storage and power-to-gas in distribution systems

Concerning the rapid development and deployment of Renewable Energy Systems (RES) and Energy Storage System (ESS) including Power-to-Gas (PtG) technology can significantly improve the friendliness of the integration of renewable energy. The purpose of this paper is to develop a coordination strategy between a battery energy storage and a PtG system. A simulation case is created with an electrical and a natural gas grid as well as steady-state models of RES and PtG. Charging strategies are developed accordingly for the ESS as well as production strategies for the PtG system. The size of the ESS is then observed with regards to the RES and PtG systems. As a result, it is found that surplus energy from RES can be stored and then used to support the electrical grid and the natural gas grid. It is also concluded that the capacity of the ESS can be affected, given a proper charging and production strategy, which needs to be tailored to each system. As shown in the paper, due to an improper charging strategy in the first quarter of a month, the ESSPC size has increased from its optimal size of 314 MWh to roughly 576 MWh. It can also be seen that given a proper charging strategy, this capacity can be less than 200 MWh.

Power-to-gas and power-to-liquid for managing renewable electricity intermittency in the Alpine Region

Large-scale deployment of renewable energy sources (RES) plays a central role in reducing CO2 emissions from energy supply systems, but intermittency from solar and wind technologies presents integration challenges. High temperature co-electrolysis of steam and CO2 in power-to-gas (PtG) and power-to-liquid (PtL) configurations could utilize excess intermittent electricity by converting it into chemical fuels. These can then be directly consumed in other sectors, such as transportation and heating, or used as power storage. Here, we investigate the impact of carbon policy and fossil fuel prices on the economic and engineering potential of PtG and PtL systems as storage for intermittent renewable electricity and as a source of low-carbon heating and transportation energy in the Alpine region. We employ a spatially and temporally explicit optimization approach of RES, PtG, PtL and fossil technologies in the electricity, heating, and transportation sectors, using the BeWhere model. Results indicate that large-scale deployment of PtG and PtL technologies for producing chemical fuels from excess intermittent electricity is feasible, particularly when incentivized by carbon prices. Depending on carbon and fossil fuel price, 0.15–15 million tonnes/year of captured CO2 can be used in the synthesis of the chemical fuels, displacing up to 11% of current fossil fuel use in transportation. By providing a physical link between the electricity, transportation, and heating sectors, PtG and PtL technologies can enable greater integration of RES into the energy supply chain globally.

TECNOLOGÍAS ASOCIADAS AL SISTEMA POWER TO GAS

The Power-to-Gas (PtG) system allows to store electrical energy by transforming it into chemical energy in the form of hydrogen or methane. These gases can be injected into the natural gas grid for further distribution and use. This article explains the different technologies related to the PtG system: electrolysis, for the production of hydrogen, and methanation, for the production of methane.

Power-to-Gas as an Emerging Profitable Business Through Creating an Integrated Value Chain

Abstract Power-to-gas (PtG) technology has received considerable attention in recent years. However, it has been rather difficult to find profitable business models and niche markets so far. PtG systems can be applied in a broad variety of input and output conditions, mainly determined by prices for electricity, hydrogen, oxygen, heat, natural gas, bio-methane, fossil CO 2 emissions, bio-CO 2 and grid services, but also full load hours and industrial scaling. Optimized business models are based on an integrated value chain approach for a most beneficial combination of input and output parameters. The financial success is evaluated by a standard annualized profit and loss calculation and a subsequent return on equity consideration. Two cases of PtG integration into an existing pulp mill as well as a nearby bio-diesel plant are taken into account. Commercially available PtG technology is found to be profitable in case of a flexible operation mode offering electricity grid services. Next generation technology, available at the end of the 2010s, in combination with renewables certificates for the transportation sector could generate a return on equity of up to 100% for optimized conditions in an integrated value chain approach. This outstanding high profitability clearly indicates the potential for major PtG markets to be developed rather in the transportation sector and chemical industry than in the electricity sector as seasonal storage option as often proposed.

Role of power-to-gas in an integrated gas and electricity system in Great Britain

Power-to-gas (PtG) converts electricity into hydrogen using the electrolysis process and uses the gas grid for the storage and transport of hydrogen. Hydrogen is injected into a gas network in a quantity and quality compatible with the gas safety regulations and thereby transported as a mixture of hydrogen and natural gas to demand centres. Once integrated into the electricity network, PtG systems can provide flexibility to the power system and absorb excess electricity from renewables to produce hydrogen. Injection of hydrogen into the gas network reduces gas volumes supplied from terminals.In order to investigate this concept, hydrogen electrolysers were included as a technology option within an operational optimisation model of the Great Britain (GB) combined gas and electricity network (CGEN). The model was used to determine the minimum cost of meeting the electricity and gas demand in a typical low and high electricity demand day in GB, in the presence of a significant capacity of wind generation. The value of employing power-to-gas systems in the gas and electricity supply system was investigated given different allowable levels of hydrogen injections. The results showed that producing hydrogen from electricity is capable of reducing wind curtailment in a high wind case and decreasing the overall cost of operating the GB gas and electricity network. The northern part of GB was identified as a suitable region to develop hydrogen electrolysis and injection facilities due to its vicinity to a significant capacity of wind generation, as well as the existence of gas network headroom capacity, which is expected to increase as a result of depletion of UK domestic gas resources.