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A hybrid Closed Loop Thermosyphon/Pulsating Heat Pipe with an inner diameter bigger than the capillary threshold is tested both on ground and in hyper/microgravity conditions. The device, partially filled up with FC-72, consists of an aluminum tube (inner diameter: 3 mm) bent into a planar serpentine with five curves at the evaporator. A transparent section closes the loop in the condenser zone, allowing fluid flow visualization. Five heaters are mounted alternatively on the branches, just above the turns and controlled independently, in order to investigate the effect of non-uniform heating configurations. On ground, where the device works as a thermosyphon, the non-uniform heating configurations promote the fluid net circulation in a preferential direction, increasing the thermal performance with respect to the homogeneous heating. Parabolic flights point out that during the 20 seconds of microgravity, the sudden absence of the buoyancy force activates an oscillating slug/plug flow regime, typical of the Pulsating Heat Pipes, allowing the device to work also without the assistance of gravity. Furthermore, peculiar heating configurations can shorten the stop-over periods and stabilize the pulsating two-phase flow motion.

Rural electrification in remote areas of developing countries has several challenges which hinder energy access to the population. For instance, the extension of the national grid to provide electricity in these areas is largely not viable. The Kenyan Government has put a target to achieve universal energy access by the year 2020. To realize this objective, the focus of the program is being shifted to establishing off-grid power stations in rural areas. Among rural areas to be electrified is Habaswein, which is a settlement in Kenya's northeastern region without connection to the national power grid, and where Kenya Power installed a stand-alone hybrid mini-grid. Based on field observations, power generation data analysis, evaluation of the potential energy resources and simulations, this research intends to evaluate the performance of the Habaswein mini-grid and optimize the existing hybrid generation system to enhance its reliability and reduce the operation costs. The result will be a suggestion of how Kenyan rural areas could be sustainably electrified by using renewable energy based off-grid power stations. It will contribute to bridge the current research gap in this area, and it will be a vital tool to researchers, implementers and the policy makers in energy sector.

Nowadays, mini-grids can provide reliable and cheap electricity also to far communities of developing countries. Diesel generators can ensure backup power, in addition to renewable sources and energy storage devices. However, poor infrastructures, severe weather conditions and a difficult procurement chain can strongly influence the fuel delivery, thus reducing the continuity of supply. The present paper proposes a stochastic method to optimize the design of a rural mini-grid composed by a photovoltaic plant, a lithium battery, a diesel generator and a fuel tank. The fuel procurement strategy and its mathematical model are also discussed and simulated. A Particle Swarm Optimization (PSO) procedure is applied to the optimal sizing of components, in combination with a Monte Carlo technique aimed to handle the uncertainties of fuel delivery, irradiance and load. A case study for a possible mini-grid in Uganda is discussed, also performing a sensitivity analysis of the results with respect to the fuel delivery time, the fuel price and the cost of load curtailment

Hybrid mini-grids are promising solutions to foster the universal electricity access in developing countries. While renewable sources, possibly combined with energy storage devices, help in reducing the environmental impact and the operational costs of electricity supply, a backup diesel generator can increase the continuity of service when RES are not available or very discontinuous. The fuel procurement can be a serious issue in rural areas, due to lack of good infrastructures, combined to long distances existing between the mini-grid and the fuel station; however, this aspect is usually disregarded in designing the mini-grid. Moreover, the traditional sizing of rural mini-grids is based on simulating simple operational strategies. Rolling horizon strategies can be more efficient since the system is redispatched also infradaily, thus leading to possible reductions of operational costs and load curtailment. The present paper proposes a novel probabilistic technique for the optimal sizing of a mini-grid, considering both the fuel procurement issues and a short-term rolling-horizon scheduling of resources. This method is applied to a system composed by a photovoltaic plant, a lithium battery, a diesel generator, and a fuel tank, minimizing the net present cost of the system over the project lifetime. A numerical case study is discussed

Energy communities (ECs) are essential policy tools to meet the Energy Transition goals, as they can promote renewable energy sources, demand side management, demand response and citizen participation in energy matters. However, to fully unleash their potential, their design and scheduling requires a coordinated technical operation that the community itself may be ill-equipped to manage, in particular in view of the mutual technical and legal constraints ensuing from a coordinated design. Aggregators and Energy Service COmpanies (ESCOs) can perform this support role, but only provided that their goals are aligned to those of the community, not to incur in the agency problem.In this study, we propose a business model for aggregators of ECs, and its corresponding technical optimization problem, taking into account all crucial aspects: i) alleviating the risk of the agency problem, ii) fairly distributing the reward awarded to the EC, iii) estimating the fair payment for the aggregator services, and iv) defining appropriate exit clauses that rule what happens when a user leaves the EC. A detailed mathematical model is derived and discussed, employing several fair and theoretically-consistent reward distribution schemes, some of which are, to the best of our knowledge, proposed here for the first time. A case study is developed to quantify the value of the aggregator and compare the coordinated solution provided by the aggregator with non-coordinated configurations, numerically illustrating the impact of the reward distribution schemes.The results show that, in the case study, the aggregator enables reducing costs by 16% with respect to a baseline solution, and enables reaching 52.5% renewable share and about 46% self/shared consumption, whereas these same numbers are only 28-35% for the non-coordinated case. Our results suggest that the aggregator fair retribution is around 16-24% the added benefit produced with respect to the noncoordinated solution, and that stable reward distribution schemes such as Shapley/Core or Nucleolus are

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