Techno-economic and uncertainty-aware optimization of hybrid renewable systems with small-scale prime movers for commercial buildings

The increasing share of renewables forces combustion-driven power generation machines to operate with high adaptability. Small-scale heat and power units, like micro gas turbines (mGT), could show potential for Hybrid Renewable Energy Systems (HRES) due to their operational and fuel flexibility. However, their economic viability in a variable energy environment remains uncertain. The levelized cost of exergy (LCOX) in HRES with combined heat and power (CHP) units, should be calculated under uncertainties to support decision-making. This paper applies design optimization to a photovoltaic/battery/heat pump system with two prime movers to investigate the required economic relevance of small-scale CHP units in HRES. The considered prime movers are internal combustion engines (ICE) and mGTs, including advanced mGT configurations such as humidified cycles (mGT-wet, mHAT). Test cases include a hospital, office and hotel in Brussels with distinct demand profiles. Uncertainty quantification on optimized system capacities is performed using Polynomial Chaos Expansions (PCE), ensuring computational efficiency. The hospital shows that adding an mGT improves LCOX (227 €/MWh compared to 244 €/MWh of non-PM HRES), while in the hotel case, non-PM systems are more cost-effective due to low electricity demand. Dry mGTs and ICEs enhance flexibility in HRES for suitable applications, but their economic viability depends strongly on energy prices and demand. Humidified mGTs improve self-sufficiency but with higher fuel cost, making their cost-effectiveness questionable if excess electricity is not sold to the grid. • Techno-economic analysis of mGTs in hybrid renewable energy systems. • Optimization balances levelized cost of exergy and self-sufficiency. • Potential of applying CHP units in buildings with high energy demand. • Heat recovery steam generator use is key for cost-effective mGT systems in hospitals. • Micro humid air turbine suits users shifting cost sensitivity from electricity to gas.