Daniel Helmut König

The potential of using power-to-liquid plants for power storage purposes

The Power-to-Liquid (PtL) concept offers the potential to interlink the power and fuel market by producing high quality fuels from electricity and CO2. In addition, gaseous by-products from fuel synthesis can be used to generate electricity in peak load hours. In this work, a PtL concept comprising of a reversible solid oxide cell (SOC) is presented and evaluated in terms of 2014 fuel net production costs (NPC) and power storage potential. Results were compared with a reference system operating steady-state in electrolysis mode. A 100 % SOC run factor was realized, whereby the SOC unit runs primarily in co-electrolysis mode. Fuel net production costs (NPC) were slightly higher for the reversible SOC system, since increased capital costs exceed the revenue from lower average electricity costs. Though, fuel costs below 1 €/l are possible if every kWh of effectively stored electricity is credited with 3-9 €ct/kWh, which is the typical storage costs of state-of-the-art pump storage plants.

Power-to-liquids: Synthetic fuels from a sustainable pathway

Introduction Liquid fuels will be the fuel of choice for air and cargo transport for the coming decades. Synthetic fuels produced by the power-to-liquid route together with CO2 from industrial processes are a promising alternative to biofuels and can contribute significantly to the production of sustainable liquid fuels. Different process routes using hydrogen obtained by electrolysis from renewable power sources combined with Fischer-Tropsch process are analyzed by process simulation. Results Integration of SOEC with the FTS is highly advantageous in terms of process efficiency. The high pressure steam that is obtained by cooling of the FTS can be used as input for the SOEC that can in this way attain an electrolyser efficiency (electrical) of >95%. The total system efficiency calculated for Power-to-Liquid can be more than 60% for optimal conditions and unit operations. Discussion and Conclusion A sustainable pathway for the production of synthetic liquid fuels is technically feasible. The fluctuating power supply from renewable sources poses questions with regard to system design, operational characteristics and economic viability that will be discussed.