Energies

Hydrogen fuel-cell forklifts are attracting increasing attention as low-noise and zero-emission alternatives to conventional forklifts. Owing to its high volumetric hydrogen density and favorable safety characteristics, metal-hydride storage shows strong potential for such applications. This work focuses on a hydrogen fuel-cell forklift using metal hydride-based hydrogen storage. A hybrid powertrain model with a PEMFC and battery is developed from thermodynamic and electrochemical formulations. Hydrogen desorption behavior in the storage tank and transient responses of both power sources are considered, and three energy management strategies are evaluated: rule-based, fuzzy logic, and adaptive fuzzy logic strategies. Under typical operating conditions, each strategy satisfies the forklift power demand in simulation. Compared with rule-based control, adaptive fuzzy logic control markedly suppresses fuel-cell power fluctuations. Compared with basic fuzzy logic control, the proposed adaptive strategy improves SOC retention and overall energy distribution. These findings may provide preliminary support for powertrain matching, hydrogen storage system parameter selection, and energy management design in hydrogen fuel-cell forklift applications.

Nighttime setback is widely applied in residential heating, yet its net benefit for inverter-driven air-to-air heat pumps in high-thermal-mass buildings remains insufficiently characterised in Mediterranean climates. This study evaluates continuous operation (R1), timer-based setback (R2), and reactive threshold-based control (R3) for a residential building in Zadar, Croatia, using a validated physics-based model calibrated with high-resolution IoT measurements over a 180-day heating season. Simulations cover building heat loss coefficients of 60–120 W/K and both 3.5 kW and 5 kW heat pumps. Timer-based setback increases electricity consumption by 1.8–4.5% (3.5 kW) and 5.4–6.3% (5 kW) relative to continuous operation, driven by a morning recovery penalty. Reactive control eliminates thermal comfort deficits but offers no energetic benefit. Both effects generalise across heat pump capacity, with penalty magnitude scaling with unit size. A formal energy balance shows that, for the timer-based and reactive setback rules investigated here, the recovery term is set by the thermal state at the start of reheating and is not removed by better knowledge of the same weather. The conclusions apply to high-thermal-mass masonry dwellings of the type investigated; they are not intended for lightweight or low-thermal-mass envelopes, where nocturnal decay and the setback energy balance can differ. These findings provide a quantitative basis for assessing conventional setback rules in this building class.

This paper concerns the modeling of the static and dynamic characteristics of the SEPIC converter. Simulation models of this system were developed for three different programs: SPICE, PLECS, and ANSYS Simplorer. These models utilized the built-in models of the passive and semiconductor components present in each of the considered programs. Additionally, an electrothermal model of this converter was formulated for SPICE. Transient analyses of the considered system were performed using all presented models, and the obtained calculation results were compared with the measurement results. The conditions under which the calculation results were obtained for the mentioned programs were identified. The calculation times for the individual programs and the considered electronic component models were also compared. The presented results show that the most accurate are those analyses performed using ANSYS Simplorer and SPICE with the electrothermal model. The fastest are those analyses performed using PLECS, and the most time-consuming are those analyses performed using SPICE with the electrothermal model.