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Abstract The worldwide energy demand has been continuously increasing, thus requesting more sustainable alternatives to the rapidly depleting fossil fuels. Therefore, biofuels such as hydrogen, bioethanol and biodiesel are gaining more importance as a renewable and pollution-free solution, which might give a significant contribution to the future energy mix. In recent years, the exponential growth of biodiesel production has led to a glycerol glut, however, according to some authors, crude glycerol might represent a suitable, abundant and low-priced feedstock for fermentation technologies. In this study we performed an energetic and economic assessment of an innovative process, which is under development in our lab, for the bioconversion of crude glycerol into ethanol and hydrogen. Ongoing experiments showed the possibility to reach at least 26 g/L of ethanol, together with 9 L of hydrogen, in non-sterile conditions and without nutrient supplements. Since kinetics and ethanol concentration need to be further improved, we performed this study with a view to evaluate the possibility of reaching economic viability. Results showed that with 26 g/L of ethanol and a retention time as high as 120 h, the calculated energy cost would be about 0.019 €/kW hth and 0.057 €/kW hel, considering the contribution of both, hydrogen and bioethanol. Moreover, bioethanol cost would be as low as 0.21 €/L, even without taking into account the possible hydrogen revenues. These results are very promising and suggest that the process has reasonable chances to achieve economic viability, thus deserving further attention. The procedure followed in this work provided a realistic and concrete target to pursue in the future lab experiments, in order to bring this technology closer to the market.

This paper is aimed to present an experimental criterion that allows researchers and designers to evaluate the performance of DC micro-grids dedicated to charging operations of full EV. The laboratory methodology is explained through tests on a demonstrator of power architecture, specifically designed as simplified case study of a DC charging station for fully-electrified low-power two-wheeler, such as: electric scooters and bikes. This experimental prototype is composed by a 20. kW AC/DC bidirectional grid-tied converter, which realizes the DC conversion stage, and two DC/DC power converters, interconnected with the micro-grid through a DC bus. The power architecture provides on one hand the charging operations of electric two-wheeler battery packs and on the other hand the integration of the micro-grid with an ES buffer, which has the main function of supporting the main grid while an electric vehicle is on charge. The performance of the considered architecture is characterized and analyzed in different operative conditions, through a specific management of the energy fluxes. The laboratory tests evaluate efficiency, charging times and impact on the main grid, with specific reference to the DC charging operations of electric scooters. The obtained experimental results show the advantages of adopting the DC buffer architecture, compared with an AC commercial battery charger, considered as reference in this work. Finally, the numerical data of this paper, related to the single power components and to the experimental results evaluated for the whole demonstrator, effectively support the lack of knowledge in the literature about charging stations for EVs. In fact, these pieces of information, based on experimental tests, are expected to support the building of simulation models and the identification of the best energy management and control strategies to be adopted in a smart-grid scenario, characterized by distributed generation systems including renewable energy sources.

A diffuse interest on cycle modifications for R744 applications that allow to achieve better CO2 cycles performance can be inferred from the literature. The parallel compression cycle in flash tank configuration seems to be an interesting solution and the authors conducted an experimental campaign to estimate the critical parameters that influence its performance in an actual cycle. Previous to that a thermodynamic analysis was lead to investigate the expectable performance of the cycle and the influence of key parameters such as compressors volumetric flow ratio and separator efficiency. The thermodynamic model designed also allowed the definition of the limit conditions for an optimal operability of the cycle of interest. The experiments showed that the theoretically reachable improvements in terms of refrigerating capacity and coefficient of performance are threatened by several phenomena which may occur in a real system. These detrimental effects are described and commented in the paper. The paper also includes experimental data obtained during the experimental activity for operating conditions typical of commercial refrigeration applications.

In recent years, cogeneration systems have gained increasing attention especially when dealing with distributed generation for residential buildings. One of the main problems with using cogenerative systems in residential building applications is that the demand for heat and electricity is not synchronized. For this reason, when the Combined Heat and Power system operates during electricity peak hours (i.e. the rate of the electricity is higher), it could be profitable to store the heat in order to satisfy delayed demands. This paper presents a model for the calculation of the profitability of Micro Combined Heat and Power systems for residential building applications. The model takes into account hourly demands calculated by means of monthly and daily load profiles for heat and electricity. The system under consideration is composed of a CHP system, an auxiliary boiler and a heatstorage tank. The model is applied to a single-family dwelling in order to evaluate the effect of the size of the thermal energy storage unit on the energy and economic performance of four different prime movers (an internal combustion engine, a Stirling engine, a micro Rankine cycle and a thermophotovoltaic system).

This paper deals with an experimental evaluation regarding the real performance of lithium based energy storage systems for automotive applications. In particular real working operations of different lithium based storage system technologies, such as Li[NiCoMn]O-2 and LiFePO4 batteries, are compared in this work from the point of view of their application in supplying full electric and hybrid vehicles, taking as a reference the well-known behavior of lead acid batteries. For this purpose, the experimental tests carried out in laboratory are firstly performed on single storage modules in stationary conditions. In this case the related results are obtained by means of a bidirectional cycle tester based on the IGBT technology, and consent to evaluate, compare and contrast charge/discharge characteristics and efficiency at constant values of current/voltage/power for each storage technology analyzed. Then, lithium battery packs are tested in supplying a 1.8 kW electric power train using a laboratory test bench, based on a 48 V DC bus and specifically configured to simulate working operations of electric vehicles on the road. For this other experimentation the test bench is equipped with an electric brake and acquisition/control system, able to represent in laboratory the real vehicle conditions and road characteristics on predefined driving cycles at different slopes. The obtained experimental results on both charge/discharge tests and driving cycles demonstrate the advantages of using lithium technologies, mainly in terms of their high efficiency, particularly at high current values. That represents a feasible solution to offer vehicle designers and users extended driving ranges and reduced recharging times. (C) 2014 Elsevier Ltd. All rights reserved.

Thermophilic co-digestion of sewage sludge with three different doses of trapped grease waste (GW) from the pre-treatment of a WWTP has been assessed in a CSTR bench-scale reactor. After adding 12% and 27% of grease waste (on COD basis), the organic loading rate increased from 2.2 to 2.3 and 2.8 kgCOD m-3 d-1 respectively, and the methane yield increased 1.2 and 2.2 times. Further GW increase (37% on COD basis) resulted in an unstable methane yield and in long chain fatty acids (LCFA) accumulation. Although this inestability, the presence of volatile fatty acids in the effluent was negligible, showing good adaptation to fats of the thermophilic biomass. Nevertheless, the presence of LCFA in the effluent worsens its dewatering properties. Specific methanogenic activity tests showed that the addition of grease waste ameliorates the acetoclastic activity in detriment of the hydrogenotrophic activity, and suggests that the tolerance to LCFA can be further enhanced by slowly increasing the addition of lipidrich materials.

Residential energy consumption in China increased dramatically over the period of 2002-2010. In this paper, we undertake a decomposition analysis of changes in energy use by Chinese households for five energy-using activities: space heating/cooling, cooking, lighting and electric appliances. We investigate to what extent changes in energy use are due to changes from appliances and to change in floor space, population and energy mix. Our decomposition analysis is based on the logarithmic mean Divisia index technique using data from the China statistical yearbook and China energy statistical yearbook in the period of 2002-2010. According to our results, the increase in energy-using appliances is the biggest contributor to the increase of residential energy consumption during 2002-2010 but the effect declines over time, due to energy efficiency improvements in those appliances. The second most important contributor is floor space per capita, which increased with 28%. Of the four factors, population is the most stable factor and energy mix is the least important factor. We predicted electricity use, with the help of regression-based predictions for ownership of appliances and the energy efficiency of appliances. We found that electricity use will continue to rise despite a gradual saturation of demand