Fuel blending impact on decarbonizing cold energy for district cooling and data centers

Abstract

Fuel blends are seen as a transitional strategy for decarbonising combustion-based energy conversion processes while retaining dispatchable service for electricity-critical cooling loads. This paper presents a 0-dimensional model for fuel-mixing integrated into a mixed-integer linear optimisation framework for both designing and operating a district cooling plant to meet a data center load. The model considers the Lower Heating Value, delivered cost and comprehensively the upstream carbon intensity of methane-hydrogen blends. It covers the on-site cogeneration, electrically and thermally driven types of chillers, photovoltaic generation and thermal storage. The hypothesis is that the system-level decarbonization performance is affected more by hydrogen production cost and carbon intensity than by the volumetric blend share. A 20 % hydrogen volumetric part is equal to only 7 % chemical-energy substitution. Therefore, it limits the direct point-of-use carbon-dioxide reduction to the same magnitude. As a matter of fact, a full substitution by green hydrogen reduces specific emissions by 46.4 % while it increases the levelised cold energy cost by 37.1 % due its high production cost shifts operation towards grid electricity. Yet, biomass-derived hydrogen reduces specific emissions by 96.5 % under the assumption of biomass carbon neutrality and lowers the levelised cold energy cost by 8.5 %. Moreover, in the case of brown hydrogen specific emissions increase by 124.4 %. The results show demonstrate that volumetric blending targets alone do not guarantee decarbonisation within the considered deterministic prices and emission factors. Certification of upstream hydrogen is crucial for a comprehensive carbon avoidance cost assessment for fuel-specific economic screening.