Synthetic Methane Research Articles

Performance Analysis of a Power-to-Gas Storage System based on r-SOC

Abstract Power-To-Power (P2P) systems represent a promising technology to store the overgeneration from renewables generating a synthetic gas (mostly hydrogen or methane) and to convert the chemical carrier back into electricity during periods of energy demand peaks. In this context, the aim of this work is to propose, model and analyse an innovative P2P system that includes, as key components, a reversible Solid Oxide Cell (r-SOC) device and a reversible chemical reactor (RCR) working both as methanator and reformer. In the synthetic fuel production phase, water and electricity are converted into hydrogen by the r-SOC, which operates as an electrolyzer. Then, the hydrogen is in turn converted into synthetic methane by the RCR, operating as a methanator. During the discharge phase, instead, the RCR device operates as a reformer, fed by methane and water, and the r-SOC operates as a fuel cell, feeding the electricity production into the grid. The whole reversible P2P is modelled in Aspen HYSYS environment allowing to simulate both the design and off-design operation of the system. In addition, to increase the whole system’s performance, a heat recovery section is included in the model and optimized. Finally, a preliminary analysis to reproduce the behaviour of the system on varying the input available electric power will be analyzed and discussed, introducing and evaluating the key performance parameters for the system.

Dynamic Adsorptive Carbon Capture in Power-to-Gas Plants

Abstract Energy transition can be addressed in the very near future with low investment costs by utilizing already-available technologies and infrastructures. In this regard, among innovative energy carriers, green synthetic methane can tackle the issue by taking advantage of natural gas facilities. Power-to-gas systems enable methane synthesis by combining electrolytic hydrogen and captured carbon dioxide. This work investigates the adsorptive carbon capture in the context of a power-to-gas system. Carbon dioxide is trapped onto the porous surface of a packed bed by adsorption and is then released during bed regeneration. The alternating process operation is analyzed by means of a dynamic model capable of reproducing both adsorption and desorption. The other system components are dynamically modeled as well to simulate their interaction during the cyclic operation. The whole cycle is analyzed. Bed regeneration by means of a hydrogen purge flow is evaluated considering the possibility of utilizing the mixture of hydrogen and desorbed carbon dioxide as reactants in a subsequent catalytic methanation process. The boundary limits for the pressure of the hydrogen purge source are identified in order to obtain the desired reactants proportion. Regarding adsorption, different post-combustion flue gases are evaluated as carbon dioxide sources from a plant-management perspective.

Optimization of Power to Gas system with cooled reactor for CO2 methanation: Start-up and shut-down tests with Ru-based and Ni-based kinetics

The dynamic behavior of a methanation process is analyzed in the context of Power to Gas (PtG) technology, to convert carbon dioxide from different sources and hydrogen produced via electrolysis with renewable energy to synthetic methane. The process configuration consists of a single cooled plug flow reactor (PFR) where both ruthenium and nickel-based kinetic models are tested in the Aspen Dynamics simulation environment. In particular, dynamic analyses are performed to study the start-up and shut-down phases and respect injection parameters in the existing gas network. The process consists of three main sections: conditioning, reaction and separation. After the development and optimization of the control system, the start-up and shut-down tests are carried out, to study the trend of composition for the injection in the gas network. The plant size is set according to the following values: 700 Nm3/h of hydrogen and 175 Nm3/h of carbon dioxide, which correspond to the methanation reaction stochiometric ratio. Different cases are considered in both the start-up and shut-down tests, by changing the GHSV values and the catalyst adopted. Moreover, in the shut-down test two different rates are considered to evaluate the behavior of the system.

DEVELOPMENT OF AN ENERGY-SAVING TECHNOLOGY FOR THE PRODUCTION OF SYNTHETIC METHANE FROM CARBON DIOXIDE. 1. RESEARCH OF KINETICS AND MACRO-KINETICS OF THE SABATIER REACTION ON MODIFICATIONS OF THE SERIAL NI/Α-AL2O3 CATALYST GIAP-3-6N

This study presents the results of laboratory research of kinetics and mechanisms of heterogeneous catalytic reactions of hydrogenation of carbon dioxide to carbon monoxide and methane through the Sabatier reaction on modifications of the serial Ni/α-Al2O3 catalyst GIAP-3-6N manufactured in Ukraine. The research was carried out on a laboratory bench using a classic glass gradientless reactor with internal piston stirring, which provides kinetic equations at the level of physicochemical constants of the reactions under consideration. A detailed analysis and review of the literature in the areas of kinetic research of our interest was carried out. A detailed comparison of the kinetic parameters obtained by us for the powder (kinetic) form of contact with a nickel content of 7.5 % (NiO = 7.5 %) with a similar and one of the best foreign analogs containing nickel, Katalco 57-4 (NiO = 15−18 %), produced by the British chemical and metallurgical company Johnson Matthey, was performed. The results of the research confirmed almost equal parameters of the kinetic activity of the compared catalysts in the reactions of hydrogenation of carbon dioxide with hydrogen, including the «Sabatier» reaction, which made it possible to propose a similar mechanism of the processes, calculate the reaction rate constants and their activation energy, propose (determine) kinetic equations for design of reactors and processes, both with the loading of a domestic catalyst and its replacement with a foreign analog. Kinetic equations will be used in the development of multi-ton synthesis gas plants for the production of methanol, ammonia, and synthetic methane, as well as carbon-free e-fuel for internal combustion engines that meet modern climate requirements. Bibl. 28, Fig. 4, Tab. 6.

Application of Analytical Solutions of the Reactive Transport Equation for Underground Methanation Reactors

Fluctuations in the production of renewable-based electricity have to be compensated by converting and storing the energy for later use. Underground methanation reactors (UMR) are a promising technology to address this issue. The idea is to create a controlled bio-reactor system in a porous underground formation, where hydrogen obtained from renewable energy sources by electrolysis and carbon dioxide from industrial sources are fed into the reactor and converted into methane. Microorganisms, known as methanogenic archaea, catalyze the chemical reaction by using the two non-organic substrates as nutrients for their growth and for their respiratory metabolism. The generated synthetic methane is renewable and capable to compete with the fossil methane. Mathematical models play an important role in the design and planning of such systems. Usually, a numerical solution of the model is required since complex initial-boundary problems cannot be solved analytically. In this paper, an existing bio-reactive transport model for UMR is simplified to such an extent that an analytical solution of the advection-dispersion-reaction equation can be applied. A second analytical solution is used for the case without dispersion. The analytical solutions are shown for both the educt (hydrogen) and the reaction product (methane). In order to examine the applicability of the analytical models, they are compared with the significantly more complex numerical model for a 1D case and a 3D case. It was shown that there is an acceptable agreement between the two analytical solutions and the numerical solution in different spatial plots of hydrogen and methane concentration and in the methane concentration in the withdrawn gas. The mean absolute error in the mole fraction is well below 0.015 in most cases. The spatial distribution of the hydrogen concentration in the comparison to the 3D case shows a higher deviation with a mean absolute error of approx. 0.023. As expected, the model with dispersion shows a slightly lower error in all cases, as only here the gas mixing resulting in smeared displacement fronts can be represented. It is shown that analytical modeling is a good tool to get a first estimation of the behavior of an UMR. It allows to help in the design of well spacing in combination with the injection rate and injected gas composition. Nevertheless, it is recommended to use more complex models for the later detailed analysis, which require a numerical solution.

Pure copper extrusion additive manufacturing of lattice structures for enabling enhanced thermal efficiency in hydrogen production

The high geometrical complexity allowed by Additive Manufacturing (AM) of pure copper can support the development of more efficient catalytic supports that can enable the design of efficient reactors for key processes for energy transition, i.e., hydrogen production with methane steam reforming or CO2 conversion to synthetic methane, thanks to the enhanced thermal conductivity of the catalytic support. Low relative density lattice geometries with open cell copper geometries can be adopted as catalyst supports in the new generation chemical reactors to improve the heat transfer. This work presents a manufacturability study about pure copper lattice filters produced via metal Extrusion AM i.e., via feedstock 3D printing and sintering. The results show that feasible parts design can be reached and produced and that heat-exchange performances can be increased with respect to conventional supports, as confirmed by lab-scale heat transfer tests. A specific metrological assessment based on CTscan data is implemented on the printed parts to qualify them and to ensure a good thermal coupling between the printed filters and the heat exchanger main tube elements.

THE POTENTIAL FOR THE DEVELOPMENT OF THE HYDRO- GEN ECONOMY IN UKRAINE UNTIL 2030

The proposed study is devoted to defining a set of means, methods and conditions that enable the creation of a sustainable and efficient hydrogen economy in Ukraine for the period up to 2030. The study itself is aimed at studying the features of the operation of the hydrogen square concept, which illustrates the various stages of the hydrogen value chain from production to final use, and the potential opportunities for the development of the hydrogen economy in Ukraine until 2030. Using the hydrogen square, safeguards across the entire hydrogen value chain – production, storage, transport and use – are discussed, highlighting the need for a balanced approach to ensure a sustainable and efficient hydrogen economy. It has been determined that the greatest potential opportunities for the development of the hydrogen economy in Ukraine for the period up to 2030 are the transportation of a mixture of hydrogen with natural gas (gitan) through the Ukrainian GTS and the production of methane from green hydrogen (synthetic methane) through the implementation of Power-to-Gas technology. It has been found that the readiness of gas transport networks to transport a mixture of hydrogen with natural gas (gitan) differs greatly in different EU countries, and the industry itself is currently at a very early stage of development. Blending is likely to be a temporary or transitional solution, given the existence of a technical and economic limit to the volume of hydrogen concentration that traditional gas infrastructure can handle. The possibility of using Power-to-Gas technology in Ukraine, in the city of Dnipro, is described. The production of synthetic methane through the implementation of the Power-to-Gas technology will provide an opportunity to obtain the gitan mixture without the use of fossil fuels in the future, which will enable the hydrogen economy to function completely without fossil fuels.

Dynamic model of a power-to-gas system: Role of hydrogen storage and management strategies

Tackling climate change requires a drastic decarbonization of the energy system through the introduction of renewable energy technologies. However, a greater penetration of intermittent renewables requires large-scale flexible energy storage. This need, combined with the growing interest in the use of hydrogen in mobility and industry, makes tangible the prospect of including this energy vector in our daily lives. However, the problems related to the development of dedicated infrastructures make its positioning in the market complex. In a transition phase, power-to-gas systems constitute an emerging solution that allows the use of existing structures for natural gas and, at the same time, solves the problem of hydrogen storage. In this study, a power-to-gas system producing synthetic methane from wind energy was modeled. Management strategies for both the electrolysis system and the hydrogen storage were implemented. In particular, the impact of the storage on the mitigation of the operating condition fluctuation of the methanation unit was analyzed. To verify the influence of the sizing of the subsystems over the system performance, a sensitivity analysis on the sizes of the methanation unit and hydrogen storage was carried out. The conducted sensitivity analysis suggested selecting the smallest size of the hydrogen storage and the size of the methanation unit equal to 80% of the electrolysis system nominal production to achieve good performances of the power-to-gas system. However, the sizing of the subsystems depends on the context in which the power-to-gas system is integrated (i.e., characteristics of wind source), the possibility to valorize the hydrogen surplus (i.e., proximity to hydrogen users), and the specific objective for which the system has been designed.

Enhanced degradation and methane production of food waste anaerobic digestate using an integrated system of anaerobic digestion and microbial electrolysis cells for long-term operation.

The integrated system of anaerobic digestion and microbial electrolysis cells (AD-MEC) was a novel approach to enhance the degradation of food waste anaerobic digestate and recover methane. Through long-term operation, the start-up method, organic loading, and methane production mechanism of the digestate have been investigated. At an organic loading rate of 4000mg/L, AD-MEC increased methane production by 3-4 times and soluble chemical oxygen demand (SCOD) removal by 20.3% compared with anaerobic digestion (AD). The abundance of bacteria Fastidiosipila and Geobacter, which participated in the acid degradation and direct electron transfer in the AD-MEC, increased dramatically compared to that in the AD. The dominant methanogenic archaea in the AD-MEC and AD were Methanobacterium (44.4-56.3%) and Methanocalculus (70.05%), respectively. Geobacter and Methanobacterium were dominant in the AD-MEC by direct electron transfer of organic matter into synthetic methane intermediates. AD-MEC showed a perfect SCOD removal efficiency of the digestate, while methane as clean energy was obtained. Therefore, AD-MEC was a promising technology for deep energy transformation from digestate.

Costs and perspectives of synthetic methane and methanol production using carbon dioxide from biomass-based processes

Costs and perspectives of synthetic methane and methanol production using carbon dioxide from biomass-based processes

Energetic, Exergetic, and Techno-Economic Analysis of A Bioenergy with Carbon Capture and Utilization Process via Integrated Torrefaction–CLC–Methanation

Bioenergy with carbon capture and storage (BECCS) or utilization (BECCU) allows net zero or negative carbon emissions and can be a breakthrough technology for climate change mitigation. This work consists of an energetic, exergetic, and economic analysis of an integrated process based on chemical looping combustion of solar-torrefied agro-industrial residues, followed by methanation of the concentrated CO2 stream with green H2. Four agro-industrial residues and four Italian site locations are considered. Depending on the considered biomass, the integrated plant processes about 18–93 kg h−1 of raw biomass and produces 55–70 t y−1 of synthetic methane. Global exergetic efficiencies ranged within 45–60% and 67–77% when neglecting and considering, respectively, the valorization of torgas. Sugar beet pulp and grape marc required a non-negligible input exergy flow for the torrefaction, due to the high moisture content of the raw biomasses. However, for these biomasses, the water released during drying/torrefaction and CO2 methanation could be recycled to the electrolyzer to eliminate external water consumption, thus allowing for a more sustainable use of water resources. For olive stones and hemp hurd, this water recycling brings, instead, a reduction of approximately 65% in water needs. A round-trip electric efficiency of 28% was estimated assuming an electric conversion efficiency of 40%. According to the economic analysis, the total plant costs ranged within 3–5 M€ depending on the biomass and site location considered. The levelized cost of methane (LCOM) ranged within 4.3–8.9 € kgCH4−1 but, if implementing strategies to avoid the use of a large temporary H2 storage vessel, can be decreased to 2.6–5.3 € kgCH4−1. Lower values are obtained when considering hemp hurd and grape marc as raw biomasses, and when locating the PV field in the south of Italy. Even in the best scenario, values of LCOM are out of the market if compared to current natural gas prices, but they might become competitive with the introduction of a carbon tax or through government incentives for the purchase of the PV field and/or electrolyzer.

Cross-sectoral assessment of CO2 capture from U.S. industrial flue gases for fuels and chemicals manufacture

Although CO2 impacts the environment negatively, it can be a valuable resource due to its carbon content. The U.S. industry emits over 825 Mt of CO2 annually, with an expected increase in the future. This article analyzes 27 different technology combinations for capturing and using CO2 for industrial feedstocks, including the production of synthetic methane, methanol, and Fischer-Tropsch fuels. The study also estimates and compares the energy requirements for capturing and converting CO2 from 16 different industrial sources, as well as the energy requirements for hydrogen production through state-of-the-art and emerging electrolyzer technologies. Additionally, the study develops a combined scenario that outlines a design for applying an inclusive approach to achieve net-zero CO2 emissions in the industrial sector, incorporating multiple decarbonization measures. The results suggest that the use of CO2 for methane production has the potential to replace all natural gas demands considered in the base case and combined scenarios. However, using CO2 utilization-based Fischer-Tropsch products alone to replace naphtha feedstock and transportation fuels is not sufficient to achieve complete decarbonization in the studied end uses. CO2 utilization-based methanol could potentially substitute for several times the current U.S. methanol production and meet the current global demand for methanol. Moreover, the study conducts an economic analysis to estimate the costs of CO2 utilization, which vary for different industrial sectors and depend on the technologies employed. Overall, this study provides valuable information for policymakers and industry stakeholders who are striving to develop effective strategies to decarbonize the industrial sector.

Economy of scale for green hydrogen-derived fuel production in Nepal.

Opportunity for future green hydrogen development in Nepal comes with end-use infrastructural challenges. The heavy reliance of industries on fossil fuels (63.4%) despite the abundance of hydroelectricity poses an additional challenge to the green transition of Nepal. The presented work aims to study the possibility of storing and utilizing spilled hydroelectricity due to runoff rivers as a compatible alternative to imported petroleum fuels. This is achieved by converting green hydrogen from water electrolysis and carbon dioxide from carbon capture of hard-to-abate industries into synthetic methane for heating applications via the Sabatier process. An economy-of-scale study was conducted to identify the optimal scale for the reference case (Industries in Makwanpur District Nepal) for establishing the Synthetic Natural Gas (SNG) production industry. The techno-economic assessment was carried out for pilot scale and reference scale production unit individually. Uncertainty and sensitivity analyses were performed to study the project profitability and the sensitivity of the parameters influencing the feasibility of the production plant. The reference scale for the production of Synthetic Natural Gas was determined to be 40 Tons Per Day (TPD), with a total capital investment of around 72.15 Million USD. Electricity was identified as the most sensitive parameter affecting the levelized cost of production (LCOP). The 40 TPD plant was found to be price competitive to LPG when electricity price is subsidized below 3.55 NPR/unit (2.7c/unit) from 12 NPR/unit (9.2c/unit). In the case of the 2 TPD plant, for it to be profitable, the price of electricity must be subsidized to well below 2 NPR/kWh. The study concludes that the possibility of SNG production in Nepal is profitable and price-competitive at large scales and at the same time limited by the low round efficiency due to conversion losses. Additionally, it was observed that highly favorable conditions driven by government policies would be required for the pilot-scale SNG project to be feasible.

Carbon abatement cost evolution in the forthcoming hydrogen valleys by following different hydrogen pathways

The need to develop a forthcoming hydrogen economy emphasises the emerging concept of ‘hydrogen valleys', where hydrogen production and consumption are being developed. This study assesses the Levelized Cost of Hydrogen (LCOH) and Carbon Abatement Cost (CAC) for various hydrogen end-use applications within the context of a hydrogen valley located in the southern Italy over different time horizons (Today 2023, Mid-Term 2030, Long-Term 2050). Examined applications include blending into the gas grid, reconversion into electricity for grid balancing by means of fuel cells, hydrogen refuelling stations for fuel cell electric vehicles (FCEVs), synthetic methane production, and electro-fuel synthesis. Employing a parametric approach, the study compares LCOH and decarbonisation costs across different pathways. Results indicate current LCOH production values of 3.66–4.90 €/kgH2, projected to decrease to 1.41–1.94 €/kgH2 by 2050. Decarbonisation cost analysis identifies blending and FCEV scenarios as the most cost-effective, contrasting with Power-to-Power scenarios, particularly in the mid and long terms.

Least-cost solutions to household energy supply decarbonisation in temperate and sub-tropical climates

Decarbonisation of building energy supply is key to achieving current targets of greenhouse gas emission reduction. However, the least-cost, net-zero supply of electrical and thermal loads in residential buildings is affected by building type, local climate and grid emissions intensity and is subject to uncertain future energy prices. This work investigated a typical detached house and an apartment in two climates – temperate and sub-tropical – in Australia. Least-cost optimisation of the technology mixes required to serve building energy loads was undertaken, including a range of appliances powered by electricity, natural gas and hydrogen and the use of distributed energy resourced, notably rooftop solar and residential battery energy storage. Solutions were investigated with increasingly stringent greenhouse gas emission abatement constraints and a range of future prices for electricity and hydrogen, demonstrating: i) progressive electrification is the likely cheapest pathway to net-zero emissions for the two building types studied; ii) should grid decarbonisation lag the abatement constraint applied to the homes, a net-zero dwelling is likely unachievable and the deepest achievable abatement is very expensive; and iii) network-delivered hydrogen may be optimal in a subset of buildings with limited distributed energy resources potential and more peaky heating and hot water demands. In such cases, bio-methane or even synthetic methane may also be preferred. Through significant adoption of distributed energy resources, results suggest an affordable route to deep (i.e. > 50 %) abatement for homeowners that relies less on grid emissions and, beyond the Australian case study, can be extended to a significant proportion of dwellings in other countries.

Electrolysis-boosted substitute natural gas from biomass: Kinetic modeling of fluidized bed gasification and system integration

The present work deals with the modeling of electrolysis-boosted biomass gasification for the production of green synthetic methane (or substitute natural gas) with a composition that enables its potential injection into the natural gas distribution grid.A kinetic and hydrodynamic model has been built to simulate a bubbling fluidized bed reactor using a mixture of steam and oxygen as gasifying agent. The model was firstly validated by comparing it with experimental results available in the open literature. Outlet temperature spans from about 730 to 1060 °C depending on the used amount of oxygen and steam within the gasifying agent, expressed through parameters like equivalence ratio and steam-to-biomass ratio.Then, process modeling for the integration between biomass gasification and high-temperature steam electrolysis has been carried out. Electrolysis has been sized to enrich the hydrogen content of the syngas, enabling a stoichiometric composition in terms of hydrogen, carbon monoxide, and carbon dioxide for the subsequent catalytic methane synthesis via carbon oxides hydrogenation. Thermal integration has been carefully designed to improve the overall process efficiency up to about 71 % (based on lower heating value of both biomass and substitute natural gas).

Synthetic methane for closing the carbon loop: Comparative study of three carbon sources for remote carbon-neutral fuel synthetization

Achieving carbon neutrality is probably one of the most important challenges of the 21st century for our societies. Part of the solution to this challenge is to leverage renewable energies. However, these energy sources are often located far away from places that need the energy, and their availability is intermittent, which makes them challenging to work with. In this paper, we build upon the concept of Remote Renewable Energy Hubs (RREHs), which are hubs located at remote places with abundant renewable energy sources whose purpose is to produce carbon-neutral synthetic fuels. More precisely, we model and study the Energy Supply Chain (ESC) that would be required to provide a constant source of carbon-neutral synthetic methane, also called e-NG (electric Natural Gas) or e-methane (electric methane), in Belgium from an RREH located in Morocco. To be carbon neutral, a synthetic fuel has to be produced from existing carbon dioxide (CO2) that needs to be captured using either Direct Air Capture (DAC) or Post Combustion Carbon Capture (PCCC). In this work, we detail the impact of three different carbon sourcing configurations on the price of the e-methane delivered in Belgium. Our results show that sourcing CO2 through a combination of DAC and PCCC is more cost-effective, resulting in a cost of 146 €/MWh for e-methane delivered in Belgium, as opposed to relying solely on DAC, which leads to a cost of 158 €/MWh. Moreover, these scenarios are compared to a scenario where CO2 is captured in Morocco from a CO2 emitting asset that allow to deliver e-methane for a cost of 136 €/MWh.

Power Systems Transition Using Biofuels, Carbon Capture and Synthetic Methane Storage

Power Systems Transition Using Biofuels, Carbon Capture and Synthetic Methane Storage

Fluidized bed chemical looping for CO2 capture and catalytic methanation using dual function materials

CO2 capture from combustion flue gas combined to its catalytic hydrogenation to synthetic methane is considered as a promising technology in the field of Carbon Capture and Utilization (CCU). In this work, the integrated CO2 capture and methanation process was investigated in an innovative chemical looping configuration using dual function materials (DFMs) recirculated alternately between two interconnected bubbling fluidized bed reactors. By physically separating the CO2 capture step and the catalytic hydrogenation reaction in two coupled fluidized bed reactors it is possible to effectively control and independently optimize the operating temperature of each half cycle while running the process continuously. A high-performing Lithium-Ruthenium/Al2O3 was selected to investigate the effect of the specific temperature level for the CO2 capture and the methanation phases in the range 200 - 400 °C, checking the stability and repeatability of the CO2 sorption and catalytic performance over 5 repeated cycles for each operating condition. Subsequently, under the best conditions in terms of methanation performance, a similar Na-promoted dual function material was also tested. The DFMs performance appeared to be quite reproducible over the cycles, but it was subject to kinetic limitations, especially in the case of Na-Ru/Al2O3. Interestingly, the methane yield approached 100 % under the highest tested temperatures for the Li-based DFM. Despite some limitations due to the experimental purge phases of the lab-scale system, the study provides the proof-of-concept of the process which enables the possibility of decoupling the two steps with the aim of a large potential intensification.

100% Renewable Electricity in Indonesia

The rapid fall in the cost of solar photovoltaics and wind energy offers a pathway to the deep decarbonization of energy at an affordable price. Off-river pumped hydro energy storage and batteries provide mature and large-scale storage to balance variable generation and demand while minimizing environmental and social impacts. High-voltage inter-regional interconnection and dispatchable capacity (existing hydro and geothermal) can help balance supply and demand. This work investigates an Indonesian energy decarbonization pathway using mostly solar photovoltaics. An hourly energy balance analysis using ten years of meteorological data was performed for a hypothetical solar-dominated Indonesian electricity system for the consumption of 3, 6 and 10 megawatt-hours (MWh) per capita per year (compared with current consumption of 1 MWh per capita per year). Pumped hydro provides overnight and longer storage. Strong interconnection between islands was found to be unnecessary for Indonesia, contrary to findings from similar modelling in countries at higher latitudes. Storage requirements for power and energy were found to be smaller than three kilowatts and 30–45 kilowatt-hours per person, respectively. Introducing gas turbines (burning hydrogen or synthetic methane) contributing around 1% of annual generation reduced the levelized cost of electricity (LCOE) by 14% and halved the storage requirements by allowing the system to ride through prolonged cloudy periods at lower cost. This work showed that Indonesia’s vast solar potential combined with its vast capacity for off-river pumped hydro energy storage could readily achieve 100% renewable electricity at low cost. The LCOE for a balanced solar-dominated system in Indonesia was found to be in the range of 77–102 USD/megawatt-hour.