Massimiliano Renzi

This study comparatively investigated the ageing behaviour of a conventional lubricant and a biolubricant modified with 0.25–1.00 wt.% KH570-coated SiO₂ nanoparticles. Nanolubricants and nanobiolubricants were prepared using a two-step dispersion method and subjected to accelerated thermal ageing at 220 and 260 °C for exposure times ranging from 120 to 240 h. Density, kinematic viscosity at 40 and 100 °C, viscosity index, Total Acid Number (TAN), Total Base Number (TBN), Fourier Transform Infrared Spectroscopy (FTIR), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) were used to evaluate their physicochemical and chemical degradation. The results showed that increasing temperature and exposure time generally intensified density growth, viscosity thickening, viscosity-index deterioration, and oxidation, whereas SiO₂-containing formulations exhibited more moderate changes in several responses under severe ageing conditions. At 260 °C and 168 h, the viscosity at 40 °C of the conventional lubricant decreased from 193.7 mm²·s⁻¹ without nanoparticles to 135.1 mm²·s⁻¹ with 1.00 wt.% SiO₂, corresponding to a reduction of 30.25%. For the biolubricant, viscosity decreased from 312.9 mm²·s⁻¹ to 98.6 and 116.8 mm²·s⁻¹ with 0.75 and 1.00 wt.% SiO₂, corresponding to reductions of 68.49% and 62.67%, respectively. Under the same severe ageing conditions, oxidation in the conventional lubricant decreased by 27.19% at 1.00 wt.% SiO₂, while oxidation in the biolubricant decreased by 34.11% and 22.08% at 0.75 and 1.00 wt.% SiO₂, respectively. Response Surface Methodology combined with ANOVA and backward elimination identified temperature, exposure time, nanoparticle concentration, and their interactions as response-dependent controlling factors. The resulting reduced regression models provided high goodness of fit; for example, the coefficients of determination ranged from 0.9976 to 0.9981 for density and from 0.9954 to 0.9999 for viscosity at 40 °C. The response surfaces confirmed that temperature and time generally promoted degradation, whereas SiO₂ addition was associated with lower excessive viscosity and oxidation increases under specific concentrations at high thermal severity, with a more pronounced effect in the biolubricants. Overall, KH570-modified SiO₂ nanoparticles showed potential for mitigating changes associated with accelerated thermo-oxidative ageing, although the optimum concentration depended on the lubricant formulation and the investigated response. Because all formulations were tested under identical nominal ageing conditions, the observed differences support a comparative assessment of nanoparticle effects; however, the contribution of evaporation and concentration effects could not be independently quantified.

Electricity-market decarbonisation increasingly relies on portfolios of long term instruments layered over short-term wholesale markets. Their joint design matters because contracts governing the same assets can interact through physical capabilities, locational constraints and settlement rules. Using Italy as a case, this article examines the Capacity Market, the FER X renewable-remuneration regime, the Electricity Storage Capacity Procurement Mechanism (MACSE), and Power Purchase Agreements (PPAs). The analysis combines a targeted synthesis of electricity-market and contract design literature with primary Italian regulatory, procurement and auction documents. A common framework links the service remunerated and settlement boundary to power-system capabilities and to the allocation of price, volume, availability, profile, credit and locational risk. The comparative analysis indicates that coherent coexistence depends on three conditions: payments must correspond to distinguishable services, simultaneous obligations must be physically feasible, and settlement boundaries must make residual risk transparent. The principal coordination issues concern dependable capacity, storage power and state of charge, congestion and locational signals, revenue stacking, reference-price consistency, metering and public–private risk transfer. The article derives four design principles for service attribution, compatibility testing, locational settlement and ex-post monitoring. These principles are relevant to electricity systems combining capacity remuneration, renewable contracts, storage procurement and private long-term contracting above short-term markets.

Flexibility markets are evolving rapidly across Europe, but national implementations differ in products, participation rules, baseline methodologies, aggregation and settlement—differences that matter even more in constrained grids and island systems. This paper compares the Spanish and Italian flexibility-market frameworks and assesses their implications for dispatch, revenues and system KPIs in two real-world contexts: the island power system of El Hierro, in the Canary Islands, and and the CEIS cooperative grid in Trentino, analysed within the PROGRESS project. El Hierro represents an electrically isolated system where flexibility is mainly linked to renewable integration, wind–pumped-hydro storage operation, curtailment reduction, reserve adequacy and security of supply. The Italian case represents an Alpine cooperative grid where flexibility is mainly associated with local congestion management, voltage support, self-consumption and resilience. A harmonised assessment framework is developed, coupling regulatory and market-design mapping with optimisation-based simulation aligned with the Adapters philosophy. In the Italian case, the PROGRESS pilot compares a utility-scale BESS located at the Ponte Pià hydroelectric plant with distributed BESS units installed at critical MV/LV substations. Results show thatcentralised BESS configurations achieve stronger financial performance through energy arbitrage and ancillary-service revenue stacking. In the CEIS grid, the 3 MW centralised BESS reaches an NPV of approximately EUR 388k, an IRR of 6.34%, a payback period of 7.49 years and an LCOS of 0.077 EUR/kWh. By contrast, distributed BESS units mainly provide local selfconsumption, voltage support, peak shaving and resilience benefits, with only the 1600 kW aggregated configuration becoming marginally profitable. These findings suggest that current market arrangements reward centralised, controllable and revenue-stacking assets more clearly than distributed or locational flexibility services. For El Hierro, the hourly dataset shows annual demand around 48–52 GWh, wind generation up to approximately two thirds of demand in selected years, and persistent diesel-backup requirements.

The transition to a fully renewable electricity system poses fundamental challenges for current electricity market design. In systems dominated by zero-marginal-cost generation, marginal pricing may lead to persistently low prices, undermining investment incentives and threatening system adequacy. Achieving European and national decarbonization targets therefore requires new regulatory and market mechanisms to ensure both reliability and economic sustainability. This paper analyses the role of Capacity Markets, Contracts for Difference and Power Purchase Agreements in supporting a renewable-dominated power system, with a focus on the Italian market. Combining regulatory analysis with quantitative simulations of alternative Contracts for Difference designs under different price scenarios, the study evaluates how these instruments contribute to maintaining adequacy and stabilizing investment conditions. The results show that Capacity Markets remain essential to guarantee system reliability, while long-term financial instruments such as Contracts for Difference and Power Purchase Agreements play a key role in mitigating revenue uncertainty and supporting renewable investments. As renewable penetration increases and wholesale prices decline, these mechanisms evolve from complementary tools to structural components of market design. The findings provide policy-relevant insights for the development of cost-efficient and reliable electricity markets aligned with decarbonization objectives.

This study proposes a novel numerical strategy to guide combustion process optimization of renewable green producer gas by identifying Safe/Stable combustion operating limits. A computationally cost-effective 2D premixed flame model is developed and validated using experimental tests and flame thermal imaging information derived from precise emissivity calibration. The volumetric composition of the reference Producer Gas (PG), 1.90% CH4, 18.50% H2, 8.85% CO2, 22.20% CO, 7.40% H2O, and 41.15% N2 is used in this study. The Flamelet Generated Manifold (FGM) model is employed to incorporate the FFCM-2, thereby modelling the effects of thermodynamic and transport properties with detailed chemistry. The default setting is modified by adding the optimal progress variables for NO and NO2 to capture NOx emissions. The flame temperature and shape were found to agree well with variable emissivity-based flame temperature. The systematic variation in Thermal Load (TL; 10 – 28 kW) and Equivalence Ratio (Φ; 0.43 –0.85) revealed a range of Safe Inlet Velocity (SIV) and permissible Safe Thermal Load (STL). The flame flashes back with super-adiabatic temperature characteristics due to density-based hydrodynamic flame instability at Φ = 0.85 at partial thermal loads (5 – 24 kW), wherein increasing the load does not lift the flame base from the burner and requires the nominal load operation to overcome unstable flame behaviour. Moreover, reducing the Φ from 0.85 to 0.43 leads to flame extinction behaviour, in which lift-off is observed only at higher loads (TL ≥ 15 kW). Further analysis suggests that lower Safe Thermal (STL) limits must be elevated with H2 % ≥ 30 co-firing cases to avoid safety and flame stability issues. The generalised STL scaling for different H2 fractions is performed with non-dimensional load ratios of STL to rated thermal load capacity ([[EQUATION]]) of the burner. Furthermore, high in-flame NOx on certain conditions does not lead to high outlet NOx. Specifically, the flashback events restrict the flame zone within the burner, resulting in a deceptively low amount of outlet NOx emissions, at Φ = 0.85, which may mislead one into thinking the clean combustion.

Modern agriculture depends heavily on machinery to maximize operational efficiency and, consequently, profitability, but the wear-and-tear on the mechanical components of machinery due to ageing can lead to reduced efficiency, more downtime, and higher maintenance expenses, thus raising the operative costs. These problems have been addressed by the use of specific lubricant additives for machinery; however, additives have known disadvantages, such as compatibility restrictions and environmental concerns, which represent critical issues especially in case of possible dispersion in the environment. Modern industry is always looking for techniques and solutions to increase efficiency and productivity, and this study investigates the possible advantages of employing nanotechnology in lubricant formulations. Amongst all possible substances, SiO₂ nanoparticles are increasingly promising as lubricant additives due to their unique properties, which include heat resistance, high levels of stability, and good biocompatibility. Moreover, biolubricants, derived from renewable sources, offer an environmentally friendly alternative to conventional lubricants. This article contributes to the field of agricultural technology by demonstrating the potential of SiO₂ nanoparticles in formulations of biolubricants thought to be used in agricultural machines. Key degradation parameters, including density, viscosity, total acid number (TAN), total base number (TBN), oxidation, and elemental composition, were systematically analysed. The results showed that SiO₂ nanoparticles mitigate viscosity loss and density increase, optimize TAN and TBN, reduce oxidation of the biolubricants by up to 17.7% at 1.00 wt% SiO₂, and stabilize elemental composition during ageing. Nanoparticles remained uniformly dispersed without sedimentation for over 30 days. This provides insights that can prevent machinery performance degradation over time, reduce lubricant changes, and suggest a more sustainable and environmentally friendly lubrication solution, thus promoting more sustainable industry.

Anion Exchange Membrane (AEM) water electrolysis is emerging as a costeffective technology. Currently, the modeling of pressurized AEM stacks remains limited for fast system-level simulations. This work presents a semi-empirical zero dimensional (0D) model accounting for pressure effects in AEM electrolyzers and validates it against an experimental campaign on a 2.4 kW stack operating at 10-30 bar, 30-50 • C, and current densities up to 0.48 A/cm 2. Experimental results show that increasing hydrogen-side pressure leads to a net reduction in cell voltage, overcoming the Nernstian penalty. This behavior is attributed to pressure-induced mitigation of gas bubble coverage, resulting in lower apparent ohmic losses and a 17% reduction in area-specific resistance. To capture this effect, a linear pressure-correction factor, θ p , is introduced in the resistance formulation. Model parameters are identified using a global weighted non-linear least-squares approach. The pressure-corrected model improves accuracy, reducing voltage errors by 33% and lowering the Akaike Information Criterion (AIC). The framework provides a physically grounded tool for real-time control of pressurized AEM systems.