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Integrated High-Temperature ELectrolysis and METHanation for Effective Power to Gas Conversion

Technology assessment

Technology assessment - LCA, market and socioeconomic studies

Renewable energy systems have to confront two major challenges: the fluctuating renewable sources need to be matched with the energy demand and a substitution for high energy density fuels in heat and transport has to be found. The newly developed concept of producing Substitute Natural Gas (SNG) claims to have the potential to address these problems.
The SNG production is a new approach of converting renewable power into methane via hydrogen and CO2 methanation (figure 1). In this way, renewable power can be stored in the natural gas network and used temporarily and spatially flexible for balancing power, for process heat and for long-distance transportation. Theoretically, it can be produced basically anywhere where water, air and renewable power are available and thus decrease import dependence on fossil fuels. It can recycle CO2 in the energy system or even act as carbon sink in combination with CO2 storage.

PtG scheme
Figure 1: Basic concept of a renewable power to methane plant (Wind/Solar-to-SNG) with concentrated CO2 from a tank, integrated into power and gas grid. (Sterner, 2009)

Within the framework of the HELMETH project, scenarios of integrated concept systems will be evaluated both in terms of economic viability and environmental impacts. The objectives of the economic analysis are:

  • Elaboration of business cases for various operation scenarios of the Power-to-Gas units. Considering intermittent operation using surplus renewable power, continuous operation at economically optimal points and cases of load break-off at peak load times.
  • Definition of operation requirements for the overall units derived from the most promising business case.
  • Summary of regulations and funding initiatives for the most-promising markets.

An integrated system having the innovative features of the HELMETH concept (Electricity to Gas, plus methane exploitation opportunities) has not been yet evaluated in terms of its Socio-Environmental impact. Implementing LCA within HELMETH is considered not at all trivial, exceeding the current methodological State of the Art. The objectives to be pursued are the following:

  • Quantification of the life cycle environmental impact of a “base case” configuration of the HELMETH concept system.
  • Definition of benchmark systems to be used in the comparative analysis. The reference systems formulated will also consider the option of no renewable energy storage.
  • Evaluation of alternative methane exploitation and operational mode scenarios of the HELMETH system versus the environmental performance of the reference scenarios.
  • Assessment of the life cycle CO2-eq impact of the alternative CO2 sources. As seen in fig.1 and 2, several integrated concepts with CO2 from air, biomass, and fossil fuels can be considered.
CO2 sources
Figure 2: Possible CO/CO2 sources for PtG (Bajohr and Götz, 2013)

Bajohr, S., Götz, M., 2013. Development of a methanation process for PtG appliances. EDGaR/DVGW Conference. Arnhem, Holland
Sterner, M., 2009. Bioenergy and renewable power methane in integrated 100% renewable energy systems: Limiting global warming by transforming energy systems. Kassel University Press GmbH