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There are several small energy sources that can be exploited to provide useful energy: small temperature differences, mechanical vibrations, flow variations, latent exhausts are just some examples. The recovery of such common and small energy sources, usually wasted, for example with the conversion into useful amounts of electrical energy, is called energy harvesting. Energy harvesting allows low-power embedded devices to be powered from naturally-occurring or unwanted environmental energy (e.g. pressure or temperature difference). The main aim in the last years of researches in such field, was the increasing of the efficiency of such components, with a higher power output and a smaller size. At present, a wide range of systems incorporating energy harvesters are now available commercially, all of them specific to certain types of energy source. Energy harvesting from dissipation processes such as fluid lamination is a challenge for many different applications. In addition, control valves to dissipate overpressures are common usage of many plants and systems. This paper surveys the market opportunities of such harvesting systems, considering the trade-offs affecting their efficiency, their applicability, and ease of deployment. Particular attention will be devoted to small energy harvesters than can exploit small expansions, such as from lamination valves or to systems that can feed mini sensors from small pressure drops, promising compactness, efficiency and cost effectiveness.

The cluster on Enabling Technologies in the framework of the Fast Track on Energy Communities workshop held in Rome during the Sustainable Places 2021 conference presented a series of H2020 projects and their innovative technological solutions to facilitate the uptake of energy communities, demand-response and energy efficiency projects in Europe.

The analysis of different energy systems has shown various sources of variability and uncertainty; hence the necessity to quantify and take these into account is becoming more and more important. In this paper, a steady state, off-design model of a solid oxide fuel cell and turbocharger hybrid system with recuperator has been developed. Performances of such stiff systems are affected significantly by uncertainties both in component performance and operating parameters. This work started with the application of Monte Carlo Simulation method, as a reference sampling method, and then compared it with two different approximated methods. The first one is the Response Sensitivity Analysis, based on Taylor series expansion, and the latter is the Polynomial Chaos, based on a linear combination of different polynomials. These are non-intrusive methods, thus the model is treated as a black-box, with the uncertainty propagation method staying at an upper level. The work is focused on the application on highly non-linear complex systems, such as the hybrid systems, without any optimization process included. Hence, only the uncertainty propagation is considered. Uncertainties in the fuel utilization, ohmic resistance of the fuel cell, and efficiency of the recuperator are taken into account. In particular, their effects on fuel cell lifetime and some simple economic parameters are evaluated. The analysis distinguishes the specific features of each approach and identifies the strongest influencing inputs to the monitored output. Both approximated methods allow an important reduction in the number of evaluations while maintaining a good accuracy compared to Monte Carlo Simulation.

Nowadays the research in energy field is focused on conversion technologies which could achieve higher efficiencies and lower environmental impact. Among these, fuel cells are considered an extremely promising technology and pressurized solid oxide fuel cell (SOFC) systems are particularly attractive for their high electric efficiency, potential for cogeneration applications, low carbon emissions and high performance at part-load. This paper aims to perform a robust design of an innovative turbocharged hybrid system model, featuring components validated with industrial data, where a turbocharger is used to pressurize the fuel cell, promising better cost effectiveness than a microturbine-based hybrid system, at small scales. This study will evaluate the impact of the main operating parameters (fuel cell area, stack current density and recuperator surface) on the plant performance, considering uncertainties in the system and creating a response surface of the model to perform the study. Finally, a study of the operating costs of such plant is performed to evaluate its profitability in the Italian market scenario.

This workshop brought together a selection of H2020 EU-funded projects involving experts from the biomass, geothermal, solar thermal, and heat pump sectors to discuss a common strategy for increasing the use of renewable energy technologies for heating and cooling for buildings and industry.

Abstract In thermal grids and district heating, thermal storage devices play an important role to manage energy demand. Additionally, in smart polygeneration grids, thermal energy storage devices are essential to achieve high flexibility in energy demand management at relatively low cost. In this scenario, accurate evaluation of state of charge of storage vessels based on available measurements is critical. The aim of this paper is to develop and compare three different models for state of charge estimation in stratified water tanks (discrete temperature measurements) and the related application in an experimental polygeneration grid with a real-time management tool. The first model is based on the empirical calculation of the state of charge considering the thermal power difference between generation and consumption, and afterwards correction based on measured temperatures. The second model is a mathematical approach considering a pre-defined temperature shape fitted with experimental data. The latter model is based on a 1-D physical approach using a multi-nodal method forced on the basis of the measured temperatures. The models were compared considering an experimental test performed in the polygeneration laboratory by the Thermochemical Power Group (TPG). As a result of the comparative analysis, the first model was selected for applications in complex polygeneration grids, due to its good compromise between accuracy and computational effort. Several tests were carried out to demonstrate the performance of the empirical approach selected for the thermal storage model and the economic benefit related to the utilization of this vessel. The experimental plant, constituted by two different prime movers (a 100 kW microturbine and a 20 kW internal combustion engine) and a thermal storage tank, was able to demonstrate the performance of a real-time management tool. For this reason, special attention was devoted to the variable cost comparisons. The novelty of this work lies in the development of the real-time management tool coupled with a thermal storage model by considering the simplified modelling approach. This is an essential requisite for complex polygeneration grids including hundreds or thousands of prime movers and thermal storage devices. Additionally, it is important to state that in such cases the required real-time performance could be difficult to obtain. The results, produced with the innovative and flexible experimental rig, demonstrate the positive impact of thermal storage as well as the effective management performance of this quite simple dispatching approach. Another important novel aspect regards this experimental assessment considering both specific 3-h tests and extended conditions typical of a possible real application.

Abstract This paper examines the main non-technical factors that influence social and market acceptance of solar photovoltaic panels and heat pumps in buildings. The paper discusses results from a literature review and a survey of European stakeholders. Statistical analysis results of survey data identify the most common barriers to adoption of renewables as: limited information about the technology, financial concerns, and sociodemographic factors. Survey results indicate variability in market and social acceptance of renewables between stakeholders and countries. The investment cost of the technologies is identified as a barrier to adoption for all countries. Legal and organizational issues are identified as barriers in Spain. Economic and legal barriers are identified as barriers in Latvia and Belgium. The respondents from Germany only identify investment cost as a barrier. Economic aspects are identified as the main barriers among public building owners and the general public. Businesspeople identified the largest number of barriers, including economic aspects, lack of information, trust, business models, and legal issues, while private building owners identified the least number of barriers, with concerns only related to economic aspects. Results of this study provide valuable information for policymaking focused on increasing the adoption of renewables in the building sector. Additionally, this study identifies the need to increase environmental awareness among citizens and increase the availability of information about technologies to stakeholders. Citizens should be informed about the recoupment of the investment costs of the technologies to offset the perception of high investment costs, long payback time, and lack of proper business models.

Abstract The coupling of a pressurized solid oxide fuel cell (SOFC) and a gas turbine has been proven to result in extremely high efficiency and reduced emissions. The presence of the gas turbine can improve system durability compared to a standalone SOFC, because the turbomachinery can supply additional power as the fuel cell degrades to meet the power request. Since performance degradation is an obstacles to SOFC systems commercialization, the optimization of the hybrid system to mitigate SOFC degradation effects is of great interest. In this work, an optimization approach was used to innovatively study the effect of gas turbine size on system durability for a 400 kW fuel cell stack. A larger turbine allowed a bigger reduction in SOFC power before replacing the stack, but increased the initial capital investment and decreased the initial turbine efficiency. Thus, the power ratio between SOFC and gas turbine significantly influenced system economic results.