Performance assessment of a solar-powered Organic Rankine Cycle for combined heat and power generation in small size rural applications

The recent interest in the installation of micro-grids in developing countries led researchers to the investigation of different renewable energy concepts to the strongly decentralized ("localized") generation of electric and thermal energy in remote locations. Among the different technologies proposed, Solar-powered Organic Rankine Cycle (S-ORC) results as a promising option for the combined production of heat and power, since it can reach fairly high electrical efficiencies within rather low heat source temperatures (350-500 K). This work presents a performance assessment of a small-scale S-ORC system capable of producing 10KWe. The system consists of an array of solar collectors and an Organic Rankine Cycle engine. The capability of the aforementioned system to produce combined heat and power at various latitudes and at different heat source temperatures is investigated. The paper is organized as follows. First, the mathematical model of the S-ORC system is presented. Then, the size and cost of the solar collector are evaluated, based on different inlet temperature for the heat source. This study highlights the potential of S-ORC systems in providing thermal and electrical energy in off-grid applications

Analysis of Radiation Propagation inside a Hierarchical Solar Volumetric Absorber

none4The solar receiver is a critical component of concentrated solar power technology; it works as a heat exchanger, transforming the concentrated solar radiation into high-temperature heat. Volumetric receiver technologies, using air as a heat transfer fluid, are designed to reach higher temperatures than the current receiver technology, which is limited by material resistance and fluid instability. The higher temperature, up to 1200 K, could be used in high-temperature industrial processes or a high-temperature thermodynamic cycle. A correct radiation propagation is essential to develop their performances, reducing reflection and emission losses and promote the heat transfer to the fluid. In this study, the optical behaviour of a hierarchical volumetric receiver (HVR) developed in Bruno Kessler Foundation (FBK) has been studied using Monte Carlo ray tracing (MCRT) simulations. The simulations have been validated in an experimental setup that evaluates the light transmissivity of the HVR porous structure. Two different HVR structures are evaluated with MCRT simulations that use a real solar dish geometry to configure a complete concentrated solar power (CSP) plant. Results show that frontal and rear losses are, respectively, 12% and 3% of the incoming concentrated radiation. Inside the HVR, 15% of the incoming power is propagated trough the lateral void spaces. Therefore, the power spreading avoids the overconcentration of the centre of the focalized area. The HVR optical behaviour has been investigated, showing an optical efficiency of 85%.nonePratticò, Luca; Bartali, Ruben; Crema, Luigi; Sciubba, EnricoPratticò, Luca; Bartali, Ruben; Crema, Luigi; Sciubba, Enric

Solar Thermal Technologies for Low-Carbon Industrial Processes: Dynamic Modelling, Techno-Economic Analysis and Environmental Impact

Solar thermal technologies are already available on the market, and they are robust and relatively cheap. Unfortunately, solar heat is seldom used in the industrial processes, and the main obstacle of solar heat diffusion is often the lack of adequate predictive modelling of solar plant integration that identifies its energy potential, economic feasibility, and environmental benefits. In this paper, we aim to investigate and evaluate the possibility of supplying solar heat to the pasta-drying process located in the northeast of the Italian Alps (“Felicetti”). The methodology proposed is structured with the combination of several software, namely, PVGIS®, Matlab®, Dymola®. The methodology developed is tested, considering solar thermal energy as the primary source, in different geographical context

Study on Carnauba wax as Phase Change Material Integrated in Evacuated Tube Collector for Solar Thermal Heat Production

Evacuated tube collector (ETC) for solar heat production is one of the most efficient systems to convert sun energy into usable energy. Unfortunately, some technological barriers are still present in solar thermal heat systems that limit the use of these technologies to decarbonize processes. An important obstacle is the requirement of heat at stable temperatures, which are not always achievable by solar fields, e.g. variable sky. For that reason, in this work, we studied the phase change materials embedded in the evacuated tube collector to keep stable the water temperature for a short period (min, hours). In this study, carnauba wax was used as a sustainable phase change material (PCM), to avoid the use of PCM based on hydrocarbon waxes. The phase - change material has been packaged using a polyethylene bag inserted in an evacuated tube collector with heat pipe technologies and tested. The collector has been tested outdoor under solar irradiation and in the shading condition. The experimental results show that is possible to detect a sensible effect of PCM on the temperature using 4 kg of carnauba wax while important effect on the temperature stabilization using 9kg of PCM. Using 9kg of the PCM we observed a stability of the outlet water temperature at 65°C for 30 minutes in shading condition

Bent & Broken Bicycles: Leveraging synthetic data for damaged object re-identification

Instance-level object re-identification is a fundamental computer vision task, with applications from image retrieval to intelligent monitoring and fraud detection. In this work, we propose the novel task of damaged object re-identification, which aims at distinguishing changes in visual appearance due to deformations or missing parts from subtle intra-class variations. To explore this task, we leverage the power of computer-generated imagery to create, in a semi-automatic fashion, high-quality synthetic images of the same bike before and after a damage occurs. The resulting dataset, Bent & Broken Bicycles (BBBicycles), contains 39,200 images and 2,800 unique bike instances spanning 20 different bike models. As a baseline for this task, we propose TransReI3D, a multi-task, transformer-based deep network unifying damage detection (framed as a multi-label classification task) with object re-identification

Water Sludge Drying: modelling of solar thermal plant for solar vacuum dryer

none1sinoneBartali, RubenBartali, Rube

Decarbonization of industrial processes: technologies, applications and perspectives of low-temperature solar heat (80-150°C)

Low-temperature (80-150°C) solar collectors guarantee a very high efficiency (up to 60%) in the conversion of solar radiation into useful thermal energy. Moreover, solar thermal technologies are already reliable solutions, relatively cheap and widely available in the market. For that reason, solar collectors operating at low temperatures are among the most important sustainable technologies that can reduce the fossil fuel consumption of industrial processes and their corresponding carbon footprint. Unfortunately, Solar Heat for Industrial Processes (SHIP) is still mostly unused for several reasons, e.g., not easy identification of the appropriate applications (e.g., cleaning processes, drying, desalination) or lack of knowledge of the potential environmental and economic benefit of the use of SHIP technologies. For that reason, this work includes i) an overview of solar technologies for low/medium -temperature SHIP (80-150°C) ii) results obtained on the innovative design of the mirrors used in evacuated receiver tube by means of a variation in the shape of its internal reflector iii) estimation of CO2 saving using a solar field based on evacuated tube collector (ETC). The work also includes a comparison of the standard ETC solar plant with an ETC solar plant embedded with reflectors with innovative shape