DOI: 10.5281/zenodo.16312688
title: Open model for calculating the LCO (Levelized Cost Of) of different solar fuels
title: Modelo abierto para el cálculo del LCO (Levelized Cost Of) de distintos combustibles solares

description: The attached Excel file allows you to calculate the LCO of different solar fuels supposedly manufactured, in a process similar to that of water electrolysis, by means of CO2 electrolyzers.

Its implementation in an Excel file allows the user to easily identify the input parameters on which the model is based and, by accessing the content of the corresponding boxes, to visualize the formula that has been used in the calculations. The user will thus be able to evaluate the reliability of the calculation, identify possible errors that may be affecting the result and even use the file as a starting source to adapt it to their own needs, complementing it, for example, with other parameters of interest.

In one of its columns, the case of hydrogen production by electrolysis has been included as a reference, not only as a comparative element for the calculation but also because some of the input parameters could be common for both types of electrolyzers.

As a reference for the consideration of which parameters could be relevant in the model, we have considered the following sources

 ·         Lazard. Lazard’s Levelized Cost of Hydrogen Analysis. 2021.

·         https://observatory.clean-hydrogen.europa.eu/tools-reports/levelised-cost-hydrogen-calculator

although we have not included all the parameters mentioned in these models, which are only valid for the case of hydrogen, we have added others specific to the case of CO2 and the formulas used have been independently deduced by us.

 The description of the input parameters used is self-explanatory in the Excel file and, as we have advanced, by accessing the content of the boxes, the model used in the calculations can be checked. However, we clarify below some of the parameters whose interpretation may generate greater difficulty.

 ·                     The "CO2 cost" included by default in the sheet (400 €/t) corresponds to an estimate of the cost based on the assumption that this CO2 comes from its direct extraction from the atmosphere and is based on the Shherwood diagram (K. Z. House, A. C. Baclig, M. Ranjan, E. A. van Nierop, J. Wilcox, H. J. Herzog,  Proc. Natl. Acad. Sci. U.S.A. 2011, 108, 20428–20433.) assuming a dilution of CO2 in the atmosphere of 400 ppm.

·                     In the "Gibbs reaction free energy" box, you will find expressions such as, for example, for the case of methanol "=702.5/3600/F25*1000". The number 702.5 corresponds to the value of the Gibbs free energy of the reaction in kJ/mol which is the value normally found in the literature. The rest of the quantities correspond to their conversion to kWh/kg.

·                     The cost of electricity must assume its average value over the life of the installation.

·                     The formula that considers the production of the compound in question with degradation updates the efficiency of the electrolyzer at hourly intervals, i.e. it assumes that the efficiency is constant for one hour and, the next hour, it works with a constant efficiency again, but degrades by the corresponding value according to the value entered in the "stack degradation" box.

·                     The box "CO2 mol efficiency utilization" counts what percentage of moles of CO2 have contributed to the generation of the desired product, taking into account that the unused CO2 could not have been recycled. In the case of CO2 electrolyzers, this parameter can be important, since CO2 molecules are often used to generate more than one organic compound, of which only one is of interest or only one it can be separated from the rest." The concept of "H2O mol efficiency utilization" is similar: it counts what percentage of water molecules have been used to generate the desired compound. In the case of water, the impact of this parameter is less critical as long as its cost is much lower than that of CO2. 

This work has been funded by the DEFY-CO2 DEFYCO2 Project (TED2021-129694B-C22), funded by the Spanish Ministry of Science, Innovation and Universities and the European Union through NextGeneration EU funds.