Fabrizio Alberti

Development of a pellet boiler with Stirling engine for m-CHP domestic application

A new sustainable technology has been designed by Fondazione Bruno Kessler through its unit Renewable Energies and Environmental Technologies. This technology is realized integrating in a single system (1) a Stirling engine (mRT-1K) from a pre-engineering design of Allan J. Organ; (2) a micro-heat exchanger technology, to reduce the net transfer unit deficit on the hot side of the heat engine; (3) a customized pellet boiler, able to extract electrical and thermal power; and (4) a customized hydraulic circuit, connecting the cool side of the Stirling engine and the heat generation on the second section of the pellet boiler. The objective of this paper was to present a new technology for the micro-cogeneration of energy at a distributed level able to be integrated in domestic dwellings. Most part of the available biomass is used in buildings for the generation of thermal power for indoor heating and, in minor cases, for hot sanitary water. In the Province of Trento, 88% of the biomass is used for this purpose. The full system is actually under integration for the test phase and not yet tested. The first tests on the single components have confirmed preliminary results on the Stirling engine with respect to the tolerances, pressurization, and proper integration of the electrical generator-driven control system. The pellet boiler has been tested separately, confirming an overall thermal efficiency of 90%.

State of the art of performance evaluation methods for concentrating solar collectors

For the development and establishment of concentrating solar thermal collectors a reliable and comparable performance testing and evaluation is of great importance. To ensure a consistent performance testing in the area of low- temperature collectors a widely accepted and commonly used international testing standard (ISO 9806:2013) is already available. In contrast to this, the standard ISO 9806:2013 has not completely penetrated the testing sector of concentrating collectors yet. On that account a detailed literature review has been performed on published testing procedures and evaluation methodologies as well as existing testing standards. The review summarizes characteristics of the different steady-state, quasi-dynamic and fully dynamic testing methods and presents current advancements, assets and drawbacks as well as limitations of the evaluation procedures. Little research is published in the area of (quasi-) dynamic testing of large solar collectors and fields. As a complementary a survey has been ...

Heat Transfer Analysis for a Small-Size Direct-Flow Coaxial Concentrating Collector

A coaxial evacuated solar tube has been analyzed. The tube is included in a small-scale concentrated solar power (CSP) system, which runs a cogeneration Stirling engine unit. The engine provides electricity and at the same time generates hot water for heating and sanitary purposes, by cooling down the compression cylinder. The present work is focused on the thermodynamic characterization for a forced-flow in the coaxial evacuated tube, which can heat thermal oil up to 300 C, when coupled with a parabolic trough collector. The single coaxial tube is 2 m long, it has one glass penetration, it is provided with a glass–metal seal and it has an absorber tube in the focal point with a diameter of 12 mm. A model based on heat transfer analysis coupled with fluid dynamic is presented and discussed. The model is then used to investigate spatial temperature profiles and thermal behaviors for the whole solar collector. It improves previous works in the field of concentrating solar collectors and covers the research in small-size concentrating system using thermal oil as heat transfer fluid. [DOI: 10.1115/1.4007297]

Numerical analysis of radiation propagation in innovative volumetric receivers based on selective laser melting techniques

Volumetric absorbers constitute one of the key elements in order to achieve high thermal conversion efficiencies in concentrating solar power plants. Regardless of the working fluid or thermodynamic cycle employed, design trends towards higher absorber output temperatures are widespread, which lead to the general need of components of high solar absorptance, high conduction within the receiver material, high internal convection, low radiative and convective heat losses and high mechanical durability. In this context, the use of advanced manufacturing techniques, such as selective laser melting, has allowed for the fabrication of intricate geometries that are capable of fulfilling the previous requirements. This paper presents a parametric design and analysis of the optical performance of volumetric absorbers of variable porosity conducted by means of detailed numerical ray tracing simulations. Sections of variable macroscopic porosity along the absorber depth were constructed by the fractal growth of sing...