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This paper investigates the energy distribution and the waste heat energy characteristics of a compression ignition engine for micro-cogeneration applications, at different engine speeds and loads. The experimental activity was carried out on a three-cylinder, 1028 cc, common-rail engine. Tests were performed with diesel fuel and a 20% v/v biodiesel blend (B20). The quantity and the quality of the waste heat energy were studied through energy and exergy analyses, respectively. Combustion characteristics were investigated by means of indicating data. Gaseous emissions were measured and particles were characterized in terms of number and size at exhaust. It was found out that the addition of 20% v/v of RME to diesel fuel does not affect significantly the brake fuel conversion efficiency and the energetic flows. On the other hand, biodiesel blend allows to reduce the combustion noise and the pollutants emissions in most of the operating conditions. A proper phasing of the injection strategy for the biodiesel blend could further reduce the exhaust emissions, mainly at high engine speeds. The results presented in this paper could be useful for the development of diesel engine based micro-cogeneration systems working at different engine speeds and loads.

Abstract Generally, off-grid fossil fuel generators provide energy supply to remote regions. The integration of photovoltaic (PV) plants to battery energy storage (BES) systems potentially increases reliability, the system autonomy and lifetime, reducing the generator working hours and the system environmental impact. PV–BES–Diesel generator hybrid energy systems (HESs) offer technical, economic and environmental benefits compared to traditional off-grid systems. This paper proposes a bi-objective design model for off-grid PV–BES–Diesel generator HESs. The aim is to identify the PV plant rated power, the BES system capacity and the technical configuration able to jointly reduce the levelised cost of the electricity ( LCOE ) and the carbon footprint of energy ( CFOE ) . Furthermore, the comparison of the LCOE and CFOE values of the HES against a traditional diesel generator allows determining the economic and environmental advantages coming from the described system. Despite the proposed model is general and suitable for any installation site and HES configuration, this paper exemplifies its application designing a HES to be installed in a remote village in Yakutsk, Russia. The model takes into account the hourly energy demand, the irradiation and temperature profiles of the installation location calculating the hourly PV plant yield, the battery charge–discharge processes and the required generator energy. Results highlight the technical, economic and environmental feasibility of the system for a context with a medium irradiation level, i.e. ∼1400 kW h/(m2 year), and relatively low fuel cost, i.e. 0.7 €/l. For the best economic scenario LCOE and CFOE reductions are of about 8% and 28%, respectively. Finally, the most effective trade-off between economic and environmental performances leads to a CFOE decrease of about 48% and a slight decrease of the economic performances (−2%).

Abstract This work discusses the integration of an externally-fired-gas-turbine power plant in a waste disposal facility where municipal solid waste is disposed in a landfill while green waste is pre-treated and selected to be sold as fuel for biomass power plants. The advantages deriving from the in situ green waste biomass conversion using the externally-fired-gas-turbine power plant is simulated using a thermodynamic model implemented in Matlab Simulink. Two different configurations are simulated: a Standard-Externally-Fired-Gas-Turbine (S-EFGT) power plant fuelled with green-waste-derived wood chips and a Hybrid-Externally-Fired-Gas-Turbine (H-EFGT) power plant fuelled with the previous biomass together with landfill gas. Power plant subsystems are modelled through a black box approach. Inputs and outputs of each box are interconnected together to create the overall models. Preliminary simulations were performed for each configuration at the same working fluid flow rate to compare the electrical and thermal efficiency of both power plants. Full scale simulations, considering an existing case study, are then developed. First, energy fluxes and the resulting efficiencies of each configuration are evaluated. Then the techno-economical comparison between the proposed solutions is discussed. Results show a net electrical energy production of 9392 MWh/year with an electrical efficiency of 14.03% for the S-EFGT using about 18,294 ton/year of wood biomass; the H-EFGT energy yield is 25,392 MWh/year with an electrical efficiency of 17.89% using the same biomass consumption and an average flow rate of 1200 Nm3/h of landfill gas. The economic analysis is completed considering the wood biomass sale, the Net Present Value (NPV) analysis showed a payback time of 7 years for the S-EFGT investment and 5.5 years for the H-EFGT one, the NPV value is 1.310.600,00 € and 6.655.792,00 € for the S-EFGT and H-EFGT configuration, respectively.

Abstract The viability of 2nd generation bioethanol processes is dependent on achieving high ethanol titers, which requires the use of high solid loadings that will negatively affect the fermentative microorganism besides increasing enzyme-associated costs. To solve this, and also problems of feedstock availability, lignocellulosic biomass can be mixed with dairy by-products to increase carbon content. In this study, industrial strains of Saccharomyces cerevisiae, with improved thermotolerance and stress resistance, were engineered for the cell surface display of cellulolytic enzymes and were evaluated in consolidated bioprocessing of cellulose. Additionally, β-galactosidase was also displayed to enable lactose consumption, resulting in high ethanol titers (>50 g/L) from the simultaneous use of cheese whey and pretreated corn cob as substrate. The multi-feedstock valorization approach together with this lactose-consuming cellulolytic yeast allowed the reduction on materials costs by 60% with a 2.5-fold increase in the annual ethanol production, therefore contributing to the establishment of economic viable ethanol processes.

Abstract Energy costs, carbon dioxide emissions, security of supply and system stability are common challenges in small islands. Many European islands have become pilot sites of energy innovation, but this green transition goes slowly in other ones usually not connected to the national grid. This study investigates the economic and environmental sustainability related to the integration of hydrogen and batteries storage in small islands, considering at the same time the use of the stored hydrogen for fuelling Fuel Cell Electric Vehicles and Hydrogen Compressed Natural Gas vehicles to meet electricity and public transportation demand of islands, so as to increase the Renewable Energy Sources penetration level. Selecting the island of Favignana (Italy) as case study, HOMER software has been used to carry out the energy analysis of different scenarios, in order to identify the most effective energy solution from both technological and economical point of views. Using economic and environmental indicators, the outcomes show that the implementation of a hybrid storage system with batteries and electrolyser can be an adequate and reliable option for increasing energy independency of small island and decarbonizing transport sector optimizing economic and environmental sustainability.

Abstract Oxy-fuel combustion is the most promising carbon capture and storage technology, which eliminates carbon dioxide emissions into the atmosphere and also decreases nitrogen oxides emissions thereby lowering global warming potential. In order to implement oxy-fuel combustion technology in full scale power plants, its costs, mainly connected with the amount of pure oxygen produced, must be lowered. The main hypothesis is that it is possible to maintain similar velocity and heat transfer distribution while maintaining stable and efficient burner operation during both combustion technologies modifying burner aerodynamics. Excess oxygen is chosen as a representative parameter of burner’s performance and investigation is carried out for four different oxy-fuel burner oxygen excess ratios (λ: 0.8, 0.98, 1.07, and 1.24) together with reference air combustion case. This study suggests a workflow, based on semi-industrial experimental investigations and computational fluid dynamics model composed of advanced sub-models for different combustion phases for development of real scale dual-mode coal swirl burners able for efficient operation during both combustion regimes. The results show that the temperature in near-burner zone and nitrogen oxides emissions increase, while carbon monoxide emissions decrease with the increase of burner oxygen excess ratio, and stable combustion with similar velocity and temperature distributions for both combustion modes is achieved for oxygen excess ratio of 1.07, with decrease in nitrogen oxides and carbon monoxide emissions during oxy-fuel combustion. The performed study demonstrates that it is possible to choose the appropriate burner settings regarding nitrogen oxides and carbon monoxide emissions and burner’s ability to operate stably in both air and oxy-fuel combustion modes.

Abstract The management of municipal solid waste (MSW) has been identified as one of the global challenges that must be carefully faced in order to achieve sustainability goals. European Union (EU) has defined as Waste to Energy (WTE) technology is able to create synergies with EU energy and climate policy, without compromising the achievement of higher reuse and recycling rates. The methodology used in this paper is based on two levels. A strategy analysis defines the amount of waste to incinerate with energy recovery considering different approaches based on unsorted waste, landfilled waste and separated collection rate, respectively. Consequently, it is evaluated the sustainability of a WTE plant as an alternative to landfill for a specific area. Two indicators are used: the Reduction of the Emissions of equivalent Carbon Dioxide (ERCO2eq) and Financial Net Present Value (FNPV). Furthermore, a social analysis is conducted through interviews to identify the most critical elements determining the aversion toward the WTE realization. The obtained results show the opportunity to realize a 150 kt plant in the only electrical configuration. In fact, the cogenerative configuration reaches better environmental performances, but it is not profitable for this size. Profits are equal to 25.4 € per kiloton of treated waste and 370 kgCO2eq per ton of treated waste are avoided using a WTE plant as an alternative to landfill. In this way, the percentage of energy recovery ranges from 21% to 25% in examined scenarios and disposal waste is minimised in order to preserve resources for the future.

Abstract Internal combustion engines are well spread in traditional power-generation systems: given their reliability, low-cost and performance it is desirable to avoid their full substitution in the short term, but, rather, to rely on the reduction of their environmental impact. This can be achieved by implementing solutions that involve minor modifications on the devices, such as the use of different fuels. In this work, the fossil fuels replacement approach has been applied to a micro-cogeneration system based on a small water-cooled compression ignition engine. The effect of bioethanol introduction as a diesel substitute in six diesel-biodiesel blends has been studied in terms of performances of the whole energy-conversion system and of the exhaust gas emissions. Positive results have been obtained showing that with a small amount (3%) of bioethanol, enhancements can be fulfilled both on performances (with approximately an average 13%-boost of the electrical and thermal efficiency) and emissions (reaching nearly a 80% of smoke opacity reduction).