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A new concept of a system for Combined Heat and Power generation is presented. The concept is based on hybrid use of two renewable energy sources, direct solar (thermodynamic solar) and biomass (indirect solar energy). Biomass combustion is conducted using a fluidized bed combustor. A second source of energy, given by the direct irradiation of the bed with a concentrated solar radiation, is integrated in the same system, using the fluidized bed as solar receiver. A Stirling engine converts heat into mechanical power. A Scheffler type mirror is adopted to allow irradiation of the system in a fixed focal point. Advantages of the proposed solution are illustrated and some preliminary results on the performance of the system, obtained with a simple model, are presented. The principal improvements with respect to existing systems of similar size and primary energy source are illustrated. The most important are the enhanced heat transfer processes that are realized with the help of the fluidized bed, and the possibility of continuous cogeneration during the day. Different working conditions are considered to estimate the contribution given by the burning of fuel, in presence as well as in absence of sun irradiation (as during the night). The distribution of energy shares among the different flux contributes is reported versus the amount of biomass burned per unit time. The results clearly demonstrate the advantage of coupling, in the same system, two sources for heat generation, thus maintaining the option of producing electricity without the supply of biomass fuel.

In this study we show that a chemical ferricyanide cathode can be replaced by a biological oxygen reducing cathode in a plant microbial fuel cell (PMFC) with a new record power output. A biocathode was successfully integrated in a PMFC and operated for 151 days. Plants growth continued and the power density increased reaching a maximum power output of 679 mW/m2 plant growth area (PGA) in a 10 min polarization. The two week record average power densities was 240 mW/m2 PGA. The new records were reached due to the high redox potential of oxygen reduction which was effectively catalyzed by microorganisms in the cathode. This resulted in a 127 mV higher cathode potential of the PMFC with a biocathode than a PMFC with a ferricyanide cathode. We also found that substrate availability in the anode likely limits the current generation. This work is crucial for PMFC application as it shows that PMFC can be a completely sustainable biotechnology with an improved power output.

Distributed power generation and cogeneration of heat and power is an attractive way toward a more rational conversion of fossil and bio fuels. Solid oxide fuel cell (SOFC) – gas turbine (GT) hybrid systems are emerging as the most promising candidates enabling the achievement of a cleaner and more efficient conversion of a large variety of resources across a broad power range covering from small to medium scale applications. This thesis introduces an innovative concept of SOFC-GT hybrid system that allows reaching efficiencies higher than the state of the art while enabling the carbon dioxide separation and avoiding fuel cell pressurisation technical issues. Several hybrid system design alternatives based on this concept are analysed through a thermodynamic optimisation approach combining process modelling, advanced process integration techniques and multi-objective optimisation. A number of optimal hybrid system configurations are determined for different design targets. The results consistently demonstrate the higher energy conversion performance and flexibility enabled with respect to the state of the art. The innovative concept analysis is extended to two applications for which SOFC-GT hybrid cycles are expected to provide the most significant impact toward sustainability: the small scale distributed generation and the conversion of renewable resources. A simplified version of the new hybrid system layout is especially developed for small scale distributed generation, typical of residential building applications (5-10 kWel). Experimental data are used to prove the technical feasibility of the system and to assess the performance potentially achievable with currently feasible technologies. The results of the analysis underline that energy conversion efficiencies higher than traditional centralised power generation can be achieved even at such a small scale. A systematic process integration and optimisation approach is used to assess the energy conversion performance of the original SOFC-GT hybrid cycle fuelled with hydrothermally gasified wet waste biomass. The analysis highlights the considerable potential of the integrated system that allows for converting wet waste biomass into electricity with First Law efficiency higher than 60% while simultaneously enabling the separation of the biogenic carbon dioxide.

Hot water heat stores with stratification are a common technology used in solar energy systems and reuse of waste heat. Adding a PCM module at the top of the water tank would give the system higher storage density, and compensate heat loss in the top layer. The work presented here includes experimental results and numerical simulation of the system using an explicit finite-difference method. Experiments and simulations were carried out using different cylindrical PCM modules. With only 1/16 of the volume of the store being PCM, 3/16 of water at the top of the store was held warm for 50% to 200% longer and the average energy density was increased by 20% to 45%. Furthermore, these 3/16 of water were reheated by the heat from the module after being cooled down in only 20 min.

In the last years, even more attention was paid to the alternative fuels that allow both reducing the fossil fuel consumption and the pollutant emissions. Gaseous fuels like methane and hydrogen are the most interesting in terms of engine application. This paper reports a comparison between methane and different methane/hydrogen mixtures in a single-cylinder Port Fuel/Direct Injection spark ignition (PFI/DI SI) engine operating under steady state conditions. It is representative of the gasoline engine for automotive application. Engine performance and exhaust emissions were evaluated. Moreover, 2D-digital cycle resolved imaging was performed with high spatial and temporal resolution in the combustion chamber. In particular, it allows characterizing the combustion by means of the flame propagation in terms of mean radius and velocity. Moreover, the interaction of turbulence with the local flame was evaluated. For both the engine configurations, it was observed that the addition of hydrogen results in a more efficient combustion, even though the engine configuration plays an important role. In PFI mode, the lower density of hydrogen causes a lower energy input. In DI mode, instead, the larger hydrogen diffusivity counteracts the charge stratification especially for larger hydrogen content. © 2016 Elsevier Ltd. All

Governments around the world try to stimulate the development and use of renewable energy technologies, like wind energy. While wind turbines are increasingly being implemented, however. it lack of social acceptance tit the local level remains an important challenge for developers of wind power plant.,;. This article aims to explore the relative importance of social and institutional conditions and their interdependencies in the operational process of planning wind power schemes. The article not only focuses on how negative local social conditions can frustrate public policy (cf. NIMBY syndrome), but also on how positive local social conditions can compensate for a negative public policy framework. We analyzed the cases of implementing wind power of two actors (the regional energy distributor and small private investors) in the municipality of Zeewolde, the Netherlands. Both cases illustrate that the formal institutional framework (formal rules, procedures and instruments) is neutral in a certain sense. Social conditions - management styles, interests and informal contacts - put meaning in this framework. The way stakeholders deal with the prevailing institutional structure clarifies social acceptance and therewith implementation.

The anaerobic digestion of outdoor cultivated Rhizoclonium biomass was investigated in this study. The influence of applying mechanical and biological pre-treatment methods prior to the biomass digestion on the overall methane yields was examined. The results show that the application of a combined biomass blending ( 20% compared to use of a mechanical size reduction method alone. The methane yields from Rhizoclonium biomass were however observed to be considerably lower than those of other algae species from the literature.

An increased interest on electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) is dealing with their introduction into low voltage (LV) distribution grids. Lately, analysis on power quality issues has received attention when considering EVs as additional load. The charging of EVs is expected without a centralized coordination in the first years, therefore a study on voltage variations and loading of LV grids is needed to estimate the immediate impact by EVs. In this work, the modeling and simulation of a Danish residential LV grid is conducted considering the two scenarios of dumb charging and overnight charging. The effect of different shares of EVs on voltage variations and transformer loading is assessed and analyzed. Results have shown that if single-phase, 16 A charging is employed, the actual LV grid would withstand the contingency of up to 30–40% of EVs charging overnight.

Due to the increasing awareness of climate change, depletion of natural resources, and increasing world population, companies in the agri-food sector need to redesign their existing supply chains and take into account both the economic and environmental impact of their operations. In practice not all the required information is available in advance due to various sources of uncertainty in agri-food supply chains. In this research a multi-objective two-stage stochastic programming model is proposed to analyse and evaluate the economic and environmental impacts to account for uncertainty in agri-food supply chains. A mushroom supply chain in the Netherlands is presented as an illustrative case study. Optimal production planning decisions calculated with a two-stage stochastic programming model are compared with the results of an equivalent deterministic model. The results of the optimizations show that accounting for stochasticity in important model parameters can reduce the difference between expected and realized economic performance by approximately 4% on average. Moreover, this paper demonstrates that including stochastic model parameters can reduce the environmental impact without compromising the current economic performance. Given the assumptions in the setup of the case study and the available information, it is concluded that applying a 2-stage stochastic programming approach for production planning decisions can lead to improved economic and environmental performance in an agri-food supply chain. New findings in real-life case studies are needed to get profound insights and understanding on the impact of uncertainty on production planning decisions in sustainable agri-food supply chains.