Awetisjan, V. (2022). Techno-economic assessment of a power-to-gas facility at the biogas plant Bruck/Leitha [Master Thesis, Technische Universität Wien]. reposiTUm. https://doi.org/10.34726/hss.2022.101887
Biomethane; Methanation; Hydrogen; Electrolysis; Sector Coupling; Renewable Gas
A flexible, resilient, and renewable energy system, where all sectors are coupled via an integrated energy grid is the key to reach climate neutrality by 2040. The power-to gas technology can be such a sector coupling technology by providing short- and longterm flexibility to the electricity grid by converting electricity into a gas, namely synthetic methane, which can be fed into the gas grid already today without any concern and can be seasonally stored in existing gas storage facilities. In order to produce synthetic methane with hydrogen from an electrolyser, a CO2 source is required. A biogas upgrading plant, which already produces pure CO2 as a by-product can be such a source. Therefore, this thesis will assess the technical and economic feasibility of a power-to-gas facility in combination with a biogas upgrading plant in order to produce synthetic biomethane, a renewable gas. This assessment was conducted as a case study for the biogas plant Bruck/Leitha. Based on a detailed literature and market review as well as real historic data from the biogas plant Bruck/Leitha and historic market prices for electricity and control reserve energy in Austria, the applicable electrolyser and methanation technologies, sizes and economic input data were gathered for the techno-economic assessment. The results showed, that even with a 45% investment grant and very low electricity prices (40-50 EUR/MWh),the long run generation costs (LRGC) of synthetic biomethane are not lower than 100 EUR/MWh and therefore, not economically feasible. It therefore makes sense, to use the ability of the alkaline or PEM electrolyser and the biological methanation reactor and provide positive or negative control reserve energy to the electricity grid by reducing or increasing the electrical consumption of the electrolyser. In this case, also a liquid CO2 storage is necessary to compensate for fluctuations in the biogas production stream and increase the availability. When participating in the positive control reserve market, the power to gas plant becomes profitable. The profitability even increases with increasing electricity prices because the positive control reserve energy price correlates with the spot market price for electricity. Therefore, a 5 MWel AEL power-to-gas unit with an output of 250 Nm3/h of synthetic biomethane could generate profits of 375,000 EUR/a with 2020 prices and 1,800.000 EUR/a with 2021prices when participating in the positive control reserve market. The total production of synthetic biomethane is then around 8 GWh/a with approx. 3000 full load hours.