Sizing of integrated solar photovoltaic and electrolysis systems for clean hydrogen production

This work presents a method to design an optimised system that combines electrolysers and solar photovoltaic panels for sustainable hydrogen production. Given the daily and seasonal variations of the electricity output vs. a stable hydrogen demand, power exchange to/from the electric grid and hydrogen storage systems are considered. The aim is to determine the optimal size of the PV field, the electrolyser, and the storage, for a given hydrogen demand, by minimising the cost of the hydrogen produced

On-off cyclic testing of a micro-cogeneration Stirling unit

Stirling engines are a promising candidate for micro-cogeneration in residential and small-scale tertiary applications. Due to the variability of energy demand profiles and electricity tariffs, real applications often require to operate the cogeneration unit with multiple daily starts and stops, especially during summer and intermediate seasons. This work focuses on the experimental analysis of a commercial 1 kWel Stirling unit, burning natural gas and generating 8 kWth of useful heat through hot water and up to 12 kWth with an auxiliary burner, when subjected to cyclic on-off operation. The scope is collecting useful data about energy balances and emissions during on-off transients, which can be later used to optimize the management of the cogeneration unit when coupled with real users. Different cyclic tests are experimented (with intermediate stops and operation of either one or two burners), keeping the temperature of the cogeneration water at the unit inlet at 50°C and its mass flow rate at the nominal value of 0.194 kg/s. The Stirling unit has shown an electrical efficiency of 8.9%, based on Lower Heating Value (LHV), in the most favorable cyclic test and 8.2% in the worst case, while thermal efficiency ranges between 91.0 and 92.6%. For comparison, the steady state electrical efficiency is 10.8% (LHV) while the thermal is 90.1% with only one burner running in full cogeneration mode. Steady state efficiencies become 7.2% and 92.0% (LHV), respectively, with the auxiliary burner running. The significant reduction of average electrical efficiency suggests the necessity to limit the frequency of starts and stops in real operation. Emissions show modest peaks in NOx and CO, which do not compromise the environmental impact, confirming the low emission combustion features of the Stirling unit

Experimental and numerical study of a micro-cogeneration Stirling unit under diverse conditions of the working fluid

Micro-cogeneration Stirling units are promising for residential applications because of high total efficiencies, favorable ratios of thermal to electrical powers and low CO as well as NOx emissions. This work focuses on the experimental and the numerical analysis of a commercial unit generating 8 kW of hot water (up to 15 kW with an auxiliary burner) and 1 kW of electricity burning natural gas. In the experimental campaign, the initial pressure of the working fluid is changed in a range from 9 to 24 barg – 20 barg being the nominal value – while the inlet temperature of the water loop and its mass flow rate are kept at the nominal conditions of, respectively, 50°C and 0.194 kg/s. The experimental results indicate clearly that the initial pressure of the working fluid – Nitrogen – affects strongly the net electrical power output and efficiency. The best performance for the output and efficiency of 943 W and 9.6% (based on the higher heating value of the burnt natural gas) are achieved at 22 barg. On the other hand, the thermal power trend indicates a maximum value of 8420 W at the working pressure of 24 barg, which corresponds to a thermal efficiency of 84.7% (again based on higher heating value). Measurements are coupled to a detailed model based on a modification of the work by Urieli and Berchowitz. Thanks to the tuning with the experimental results, the numerical model allows investigating the profiles of the main thermodynamic parameters and heat losses during the cycle, as well as estimating those physical properties that are not directly measurable. The major losses turn to be the wall parasitic heat conduction from heater to cooler and the non-unitary effectiveness of the regenerator

Application of MCFCs for active CO2 capture within natural gas combined cycles

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Modeling and Testing of a Micro-cogeneration Stirling Engine Under Diverse Conditions of the Working Fluid

Abstract Micro-cogeneration Stirling engines are promising for residential applications. This work focuses on the experimental and numerical analyses of a commercial unit generating 8 kW of hot water and 1 kW of electricity burning natural gas. Measurements are coupled to a detailed model based on a modification of Urieli and Berchowitz's work. The results indicate that the thermal efficiency is influenced by the water loop inlet temperature, varying from 90% at 30 °C to 84% at 70 °C (HHV-based). The measured and simulated powers of the engine are in the 900-964 W range depending on the water temperature and differ by less than 4%. Net electric efficiency of the engine is 15% and of the whole cogeneration unit above 9% (HHV-based). Helium instead of Nitrogen as working fluid is expected to increase the performance

Reevaluation of Photoluminescence Intensity as an Indicator of Efficiency in Perovskite Solar Cells

The photoluminescence (PL) intensity is often used as an indicator of the performance of perovskite solar cells and indeed the PL technique is often used for the characterization of these devices and their constituent materials. Herein, a systematic approach is presented to the comparison of the conversion efficiency and the PL intensity of a cell in both open-circuit (OC) and short-circuit (SC) conditions and its application to multiple heterogeneous devices. It is shown that the quenching of the PL observed in SC conditions is a good parameter to assess the device efficiency. The authors explain the dependence of the PL quenching ratio between OC and SC on the cell efficiency with a simple model that is also able to estimate the carrier extraction time of a device

Integration of Ca-Looping Systems for CO2Capture in Cement Plants

Ca-Looping (CaL) has been demonstrated as a promising technology for CO2capture in coal-fired power plants. A promising application is also in cement plants, where the CaO-rich material purged from the CaL process can replace part or all of the raw material used for clinker production. The aim of this work is to investigate two process integration options of the CaL system based on fluidized bed and entrained flow reactors in a clinker burning process. The main advantages, constrains and research questions of the two configurations are discussed, and the mass and energy balances of the whole processes are detailed and analyzed

Classes de genes de resistência expressos por Urochloa decumbens cv. Basilisk e outras seis espécies de Poaceae.

O Urochloa decumbens cv. Basilisk é uma forrageira utilizada devido a sua tolerância a solos com alto teor de alumínio e baixa fertilidade, além de rápido estabelecimento. As forrageiras são constantemente atacadas por outros organismos e possuem, assim, mecanismos pré-formados e induzíveis de autodefesa, que estão relacionados a genes de resistência (Genes R). Esses genes têm papel fundamental no reconhecimento de proteínas específicas expressadas por genes de avirulência (Avr) e podem ser distribuídas em classes que apresentam diferentes mecanismos moleculares, sendo as principais, CNLs, TNLs, RLPs e RLKs. Assim, o objetivo do trabalho foi descobrir os genes de resistência expressos por U. decumbens que sejam comuns aos genes de resistência de outras gramíneas. Foi realizado um estudo do transcritoma de U. decumbens através do sequenciamento Illumina. As sequências foram tratadas e anotadas, e então, organizadas em um banco de dados. Em seguida, retribuíram-se sequências de transcrito primário das gramíneas Setaria italica, Sorghum bicolor, Brachypodion distachyon, Zea mays, Panicum virgatum e Oryza sativa do banco de dados Phytozome, organizando-as em um banco de dados local através de SQL

The Electrochemical Performance and Applications of Several Popular Lithium-ion Batteries for Electric Vehicles - A Review

The Lithium-ion battery is one of the most common batteries used in Electric Vehicles (EVs) due to the specific features of high energy density, power density, long life span and environment friendly. With the development of lithium-ion battery technology, different materials have been adopted in the design of the cathodes and anodes in order to gain a better performance. $LiMn_{2}O_{4}$ , $LiNiMnCoO_{2}$ , $LiNiCoAlO_{2}$ , $LiFePO_{4}$ and $Li_{4}Ti_{5}O_{12}$ are five common lithium-ion batteries adopted in commercial EVs nowadays. The characteristics of these five lithium-ion batteries are reviewed and compared in the aspects of electrochemical performance and their practical applications

Evoluzione delle tecnologie cogenerative

Atti congresso Ecomondo 200