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Bierlaire_35671900_2024.pdf
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- Assuming that energy emissions account for more than three-quarters of total global green- house gas (GHG) emissions, and considering a HDPE plant owned by TotalEnergies emitting around 8,000 tonnes of CO2 per year in direct emissions and 115,000 tonnes of CO2 per year in indirect energy-related emissions, it goes without saying that reducing energy-supply related emissions to meet 2050 zero-carbon targets becomes a priority. Therefore, this work, carried out in collaboration with TotalEnergies, aims to design decarbonized energy supply models for three of its HDPE production sites in Antwerp, Houston and Jubail, through the massive integration of renewable energies. The HDPE manufacturing process is a continuous petrochemical pro- cess that requires electricity and steam to operate. The project studies the constraints associated with continuous demand fed by intermittent energy sources, and the consequences and designs resulting from these constraints are studied for each desired reduction in CO2. The demand considered is primarily electrical, with a power consumption of 25 MW every hour of the year. Taking a reference case where this supply is provided by a combined-cycle gas turbine, the aim will be to replace its use by wind turbines, photovoltaic panels, solar concentrators, and battery storage systems. At the same time, the project will examine how to deal with the issue of steam supply, a power consumption of 15 MW, by replacing a reference case where it is provided by a gas boiler with electrical boilers or heat pumps. The design found for each reduction of CO2 emissions will be that minimizes a cost function, i.e., the cost of replacing the current system. Therefore, it will be an optimization project with constraints, variables, and parameters that are studied in detail. The optimization is made up of continuous and discrete variables, the problem to be solved is complex and is also known as mixed integer linear programming (MILP). The studies, centered on the penetration rate (fossil fuel replacement rate), show the speed with which technologies are integrated into the energy mix as a function of available resources and economic criteria, while compensating for the intermittency of resources. Under cover of the parametric assumptions made, common trends in the results are ob- served for the three study sites. For Antwerp, the electrification of the system plays an extremely important role in reducing CO2 emissions. In addition, the primary energy used to power the system is notably reduced, from the reference case of 584 GWh to 542 GWh. For the most decarbonized scenario, offshore wind production accounts for a large share of total production, i.e., 372 GWh and 141 GWh for photovoltaic panels. This energy proves crucial, offering a more stable base load than solar power. However, concentrated solar power plants (CSP) are not recommended due to their high costs. The capacity of renewable energies varies from 0 to 400 MW, depending on the penetration rate. The economic analysis shows that investment in wind power followed by photovoltaic panels is optimal, reducing costs for a 35% penetration rate to 27 M€/y, compared with 29 M€/y in the reference case. Depending on the penetration rate criterion, the total cost of the system ranges from 29 to 64 M€/y. For the carbon-free scenario, the economic distribution between technologies is as follows: offshore wind 21 M€/y, onshore wind 9 M€/y, photovoltaic panels 13 M€/y, electric boiler 2 M€/y, heat pump 2.5 M€/y and battery storage 16 M€/y. Photovoltaic panels, despite lower capacity factors, are invaluable in reducing production variability by complementing wind power, diversifying the energy mix, and benefiting from resource decorrelation. Decarbonization involves not only electrification but also the creation of synergies between different energy sources, notably by dividing and delocalizing energy production. The economic optimum is an important point in the study, and its displacement is essential to make systems that no longer use natural gas attractive. The study shows the impact of various factors on the shift of this optimum. In particular, it shows that modulating consumption from 0 to +/- 30% shifts the optimal penetration rate from 35 to 50%. Furthermore, with projected changes in resource costs up to 2050, the total cost of the system is also expected to fall, with the total cost of the decarbonized system dropping from 64 to 37 M€/y, shifting the penetration rate from 35 to 75%. In particular, the study shows the independent impact of variations in each resource, demonstrating that reductions in the costs of offshore wind and battery storage have the greatest impact on total replacement costs.
Citations
Bierlaire, N. (2024). Reducing greenhouse gas emissions on the ADL process for manufacturing HDPE. https://dial-mem.test.bib.ucl.ac.be/handle/2078.2/37975