SNG Generation via Power to Gas Technology: Plant Design and Annual Performance Assessment

Alessandra Perna,Giorgio Ficco,Laura Canale,Giuseppe Spazzafumo,Linda Moretti,Marco Dell’Isola

doi:10.3390/app10238443

Alessandra Perna, Giorgio Ficco + Show 4 more

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https://doi.org/10.3390/app10238443

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Abstract

Power to gas (PtG) is an emerging technology that allows to overcome the issues due to the increasingly widespread use of intermittent renewable energy sources (IRES). Via water electrolysis, power surplus on the electric grid is converted into hydrogen or into synthetic natural gas (SNG) that can be directly injected in the natural gas network for long-term energy storage. The core units of the Power to synthetic natural gas (PtSNG) plant are the electrolyzer and the methanation reactors where the renewable electrolytic hydrogen is converted to synthetic natural gas by adding carbon dioxide. A technical issue of the PtSNG plant is the different dynamics of the electrolysis unit and the methanation unit. The use of a hydrogen storage system can help to decouple these two subsystems and to manage the methanation unit for assuring long operation time and reducing the number of shutdowns. The purpose of this paper is to evaluate the energy storage potential and the technical feasibility of the PtSNG concept to store intermittent renewable sources. Therefore, different plant sizes (1, 3, and 6 MW) have been defined and investigated by varying the ratio between the renewable electric energy sent to the plant and the total electric energy generated by the renewable energy source (RES) facility based on a 12 MW wind farm. The analysis has been carried out by developing a thermochemical and electrochemical model and a dynamic model. The first allows to predict the plant performance in steady state. The second allows to forecast the annual performance and the operation time of the plant by implementing the control strategy of the storage unit. The annual overall efficiencies are in the range of 42–44% low heating value (LHV basis). The plant load factor, i.e., the ratio between the annual chemical energy of the produced SNG and the plant capacity, results equal to 60.0%, 46.5%, and 35.4% for 1, 3, and 6 MW PtSNG sizes, respectively.

Highlights

Background and ScopeIn the context of the climate change mitigation strategies, the European Union (EU) has taken on an international leadership role since the 1990s, designing energy and environmental policies that promote the innovation and radical transformation of the energy system
The plant consists of four sections: (i) the hydrogen generation unit based on the proton exchange membrane (PEM) electrolysis, (ii) the CO2 methanation unit based on the fixed-bed technology, (iii) the hydrogen storage unit based on the pressure vessels technology, and iv) the synthetic natural gas (SNG) upgrading unit based on the membrane technology
A Power to synthetic natural gas (PtSNG) plant coupled with a 12 MW wind farm has been defined and investigated by evaluating nominal and annual efficiencies for different sizes of the electrolysis unit

Summary

Introduction

In the context of the climate change mitigation strategies, the European Union (EU) has taken on an international leadership role since the 1990s, designing energy and environmental policies that promote the innovation and radical transformation of the energy system. Directive (EU) 2018/2011 establishes that Member States must collectively ensure that the share of energy from renewable sources in the EU’s gross final consumption of energy in 2030 is at least 32%. This percentage could be increased by 2023, where necessary, to ensure compliance with the EU’s international commitments for decarbonization.

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