P2G System Research Articles

Techno-economic modelling of a Power-to-Gas system based on SOEC electrolysis and CO2 methanation in a RES-based electric grid

Renewable energy sources (RES) are growing rapidly as an alternative to fossil energy sources in order to disjoin the society from carbon sources. Wind and photovoltaic power generation is intermittent due to weather conditions. Therefore, remarkable centrality is given to the storage of the electric excess of production, and Power-to-Gas (P2G) systems seem to be one of the most promising technologies to achieve this purpose. In the case analysed in this research, a high temperature electrolyser based on solid oxide cells technology was considered, coupled to catalytic reactors for the hydrogenation of carbon dioxide into methane. The product is a synthetic natural gas (SNG) which could by directly injected into the natural gas distribution network.This work investigates the coupling between a completely RES-based electric profile in a future scenario and a P2G plant to perform a comprehensive technical, managemental and economic assessment of the system. A P2G model was built on MATLAB environment to examine the P2G plant behaviour when it was coupled with the RES-based intermittent electric profile. Firstly, the P2G plant arrangement has been discussed by varying the P2G plant capacity which has been coupled to the electric profile; the P2G capacity was then selected based on the levelized cost of product (LCOP). Secondly, the electrochemical storage has been introduced to perform a continuing operation also when excess of electricity is not available, thanks to the storage of electric energy. Finally, chemical storage tanks of hydrogen (feed for the methanation) and steam (feed for the electrolyser) were considered to reduce the number of shutdowns of the P2G plant. An assessment of the long-term gas storage in the gas distribution network was additionally performed.An optimal plant capacity with respect to the investigated scenario of local electric residual profile was sized, being equal to 7 MW, with a recovery equal to 70% of the total available electric energy from the grid. Moreover, the P2G system could be economically competitive, because the LCOP varies between 60.2 €/MWh and 224.9 €/MWh (LHV basis), which suits with current levelized natural gas prices. The overall efficiency of the plant reached around 77%, with a plant utilization factor of about 30%. The accumulators and the electrolyser are the most expensive technologies, and the LCOP strongly depends on their size (if the batteries are considered). For this scenario, the SNG yearly productivity reached a value of 18.5 GWh/y (LHV basis): in the hypothesis of using SNG to repower the electric grid (efficiency 45%), such a P2G plant could compensate the 29.6% of the amount of deficit energy, with a consequent reduction in CO2 associated emissions.

The Research on P2G Gas-Electric Hybrid Optimal Economic Dispatch Strategy

In many forms of the multi-energy complementary system, the regional multi-energy complementary distributed energy distribution system including distributed photovoltaic power generation (PV) and power-to-gas (P2G) equipment is a typical form. The P2G system uses non-peak excess power to produce hydrogen gas. Hydrogen can be stored directly for use as fuel, or it can be converted to natural gas for storage, enabling conversion of electrical energy to chemical energy. In this paper, the energy conversion and interconnection between electric energy and gas realizes the coordinated operation of distribution network and natural gas network, reduces the distribution pressure of distribution network, and improves the economic efficiency of energy utilization. First, the principle of P2G technology is introduced, and then the mathematical models of source device, conversion device and energy storage device are constructed separately. On this basis, an economic optimization-based micro-network system optimization scheduling model is established to investigate the economic benefits of gas-electric hybrid. Finally, the micro-grid system of the two scenarios is compared in the example, and the results prove that P2G has a good promotion effect on the economic benefits of the park.

P2G System Technology Development Aiming at Building a CO2-Free Hydrogen Society

The government's "Basic Energy Plan" decided on April 11, 2014 has been decided to promote initiatives aimed at realizing "hydrogen society", a society that utilizes hydrogen in everyday life and industrial activities It was. Following this, the Ministry of Economy, Trade and Industry will formulate the "Hydrogen / Fuel Cell Strategy Roadmap" in June 2014 and aim to establish a CO2-free hydrogen supply system around the year 2040. According to the Government's "Long-Term Energy Supply and Demand Outlook" published in July 2015, the renewable energy ratio to total electricity generation in FY 2030 is estimated to be 22 to 24%. On the other hand, renewable energy has large output fluctuations due to the influence of the natural environment, and geographically unevenly, there are concerns such as suspension of connection to the transmission and distribution electric power network. One solution to this problem would be the Power-to-Gas system utilizing the conversion using electric power from renewable energy into hydrogen. The obtained hydrogen can reduce CO2 emissions by replacing fossil fuels in heating sector. At the Agency for Natural Resources and Energy, the report of the "CO2 Free Hydrogen Working Group" was compiled in March, In the report, technical issues such as low cost and high efficiency of various technologies including water electrolysis equipment, improvement of durability, improvement of utilization rate were taken as technical issues. In this research, we demonstrate technological development from hydrogen production using renewable energy to transportation, storage and use in the real society, and establish the basic technology for practical application of "Power to Gas system". ACKNOWLEDGEMENT This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Modeling and operation of the power-to-gas system for renewables integration: a review

Power-to-Gas (P2G) plays an important role in enhancing large-scale renewable energy integration in power systems. As an emerging inter-disciplinary subject, P2G technology requires knowledge in electrochemistry, electrical engineering, thermodynamic engineering, chemical engineering and system engineering. Aiming at P2G modeling and operational problems concerning the research field of power systems and the energy internet, this paper briefly reviews the main technologies and application potentials of the P2G system, and makes systematic summaries of major progresses related to P2G's integration into the power grid in a bottom-top manner, including the modeling of high/room-temperature electrolysis cells, steady-state/dynamic optimization control of the P2G system, P2G's integrated model and operational strategies at the grid level. In the final part of this paper, suggestions are put forward on future research directions of P2G systems from the aspects of modeling and operational optimization.

Long-term power-to-gas potential from wind and solar power: A country analysis for Italy

Challenges related to variability of renewable energy sources (RES) recently arose in many countries and several solutions based on energy storage were proposed; among them, a promising option is Power-to-Gas (P2G), able to recover excess and unbalanced electrical energy. In this work, an assessment of long-term P2G potential is performed on a country scale, based on the analysis of electrical system historical data series, rescaled in order to consider the evolution of load and installed wind and solar capacity. In a long-term perspective, it is assumed the complete exploitation of the technical potential of the RES, which represents an upper deployment boundary with current technology. Once satisfied the electric load, residual energy to the P2G system and hydrogen production are calculated on a hourly basis; P2G installed capacity is a consequence of the assumed target on minimum operation on a yearly basis. The Italian case is analyzed, evidencing that the recovered excess energy from RES could substitute nearly 5% of current natural gas consumption or about 7% of national fuel consumption when used for hydrogen mobility. A range of options and a sensitivity analysis on assumptions is presented, showing scenarios with up to 200 GW of installed RES and a 50% additional load with respect to current one. In addition, the extension of the model to a zonal grid structure evidences the impact of transmission lines saturation that may increase gas production up to 50%. Results are compared with the German case, considered in a previous work, evidencing differences due to the diverse energy production mix.

Use of surplus wind electricity in Ireland to produce compressed renewable gaseous transport fuel through biological power to gas systems

Power to gas (P2G) may be used to store curtailed electricity whilst converting the energy vector to gas. To be economically viable these systems require cheap electricity and a cheap concentrated source of CO2. Biogas produced from anaerobic digestion typically comprises of 60% methane and 40% CO2. The P2G system substitutes for the conventional upgrading system by using hydrogen (derived from surplus wind electricity) to react with CO2 and increases the methane output. The potential CO2 production from biogas in Ireland associated with typical wet substrates is assessed as more than 4 times greater than that required by the potential level of H2 from curtailed electricity. Wind energy curtailment in 2020 in Ireland is assessed conservatively at 2175GWeh/a. Thus P2G is limited by levels of curtailment of electricity rather than biogas systems. It is shown that 1 GWeh of electricity used to produce H2 for upgrading biogas in a P2G system can affect a savings of 97 tonnes CO2. The cost of hydrogen is assessed at €0.96/m3 renewable methane when the price of electricity is €c5/kWeh. This leads to a cost of compressed renewable gas from grass of €1.8/m3. This drops to €1.1/m3 when electricity is purchased at €c0.2/kWeh.

Economic feasibility of pipe storage and underground reservoir storage options for power-to-gas load balancing

This paper investigates the economic feasibility of power-to-gas (P2G) systems and gas storage options for both hydrogen and renewable methane. The study is based on a techno-economic model in which the net present value (NPV) method and Monte Carlo simulation of risks and price forward curves for the electricity and the gas market are used. We study three investment cases: a Base Case where the gas is directly sold in the market, a Storage & Arbitrage Case where temporal arbitrage opportunities between the electricity and the gas market are exploited, and a Storage & Balancing Case where the balancing markets (secondary reserve market for electricity, external balancing market for natural gas) are addressed. The optimal type and size of different centralized and decentralized storage facilities are determined and compared with each other. In a detailed sensitivity and cost analysis, we identify the key factors which could potentially improve the economic viability of the technological concepts assessed. We find that the P2G system used for bridging the balancing markets for power and gas cannot be operated profitably. For both, temporal arbitrage and balancing energy, pipe storage is preferred. Relatively high feed-in tariffs (100€MW−1 for hydrogen, 130€MW−1 for methane) are required to render pipe storage for P2G economically viable.

Power-to-gas plants and gas turbines for improved wind energy dispatchability: Energy and economic assessment

Limited dispatchability of wind parks and unexpected grid power injections create unbalances between the generated electric power and the actual required power that has to be reduced for proper operation of the electrical grid. The increasing amount of renewable energy sources stresses this problem in several countries, where the responses in terms of reinforcement of transmission lines and ancillary services are not sufficiently fast or effective. In this study, we analyze the potential of a grid balancing system based on different combinations of traditional gas turbine based power plants with innovative ‘power-to-gas’ plants. Power-to-gas is a promising solution to balance the electric grid, based on water electrolysis, which can effectively contribute to reducing the uncertainty of dispatch plans. According to this system, the excess power produced by renewables is converted into hydrogen, which can be then injected into the natural gas grid. Different economic scenarios are assessed in this work, leading to a set of optimal sizes of the proposed system, using a statistical approach in order to estimate wind farm productivity and forecasting errors, as well as each component load conditions. Economic parameters, equivalent operating hours, CO2 emissions and lost wind energy are the main performances indexes considered in this work to compare gas turbine and electrolysis balancing systems. From an economic point of view, hybrid systems including both balancing technologies generally lead to the best performances. The scenario which leads to the highest power-to-gas capacity (with installed electrolysis power of about 6% of wind park nominal power) is determined coupling a mid-term perspective of reduction in investment costs with favorable energy market conditions or with incentives (“green-gas” or carbon taxes). In such conditions, an equivalence between the two technologies in terms of optimum installed power can be reached at an electricity-to-natural gas cost ratio between 1.8 and 2. In most interesting scenarios, the P2G system brings about a lower total wind electricity injected in the grid, due to wind-to-gas energy conversion, while it allows reducing energy losses due to grid congestion and curtailment of the wind park; however, the additional CO2 emissions due to gas turbines operation and due to the reduced electricity production tend to offset or to limit the positive effect of the carbon-free gas production.

A perspective on the potential role of renewable gas in a smart energy island system

This paper examines the potential role for Power to Gas (P2G) as applied to an island energy system with high levels of renewable electricity penetration. P2G systems require both a supply of green electricity and a source of CO2. Cheap electricity is essential for a financially sustainable P2G system. Using a PLEXOS model it was determined that deploying 50 MWe of P2G capacity on the 2030 Irish electrical grid may reduce absolute levels of curtailed wind by 5% compared to the base case. CO2 capture is expensive. The cheapest method of sourcing CO2 for a P2G system is to employ a methanation process whereby biogas from anaerobic digestion is mixed with hydrogen from surplus electricity. Anaerobic digestion in Ireland has a potential to produce biomethane to a level of 10.2% of energy in transport (19.2 PJ/a). The potential CO2 resource from anaerobic digestion could allow for a further 8.9% of energy in transport (16.6 PJ/a) from P2G production. An optimal model is proposed including for co-location of a biogas system with a P2G system. The model includes for demand-driven biogas concepts allowing electrical grid balancing and the supply of gaseous transportation fuel. Biofuel obligation certificates allows for a financially viable industry.