DOI: 10.17033/data.00000258
title: Cleanergy

description: The present project is based on a research and development collaboration between the company CLEANERGY in Gothenburg, the University of Brighton and the Federal University of Santa Catarina in Florianopolis. In the framework of the EU-FP7 project BIO_STIRLING, CLEANERGY is developing a hybrid system for the generation of electrical power through the combination of a solar concentration system and a gas burner. The concept is aiming to produce a continuous power generation, decreasing consistently the ratio CO2/MWh and using the solar energy to obtain a decrease of the pay-back time. Having an external combustion, Stirling engines can be interesting for all the applications where low-grade fuels and gas are present, even as waste products from other processes. Moreover the system might achieve very low levels of maintenance with respect to I.C. engines. The hybrid system shows a very complex issue linked to the alternative and partially superposed thermal management. The solar radiator and the burner need to produce the necessary thermal power (about 40kW) to be transferred to a working gas, which is oscillating with a frequency between 15 and 40Hz in a finned small tube at high pressure. The solar radiator has a variable flux coming from the multi-curvature mirror (solar concentration factor higher than 2000), while the burner is producing a constant idle power in presence of the solar radiation and a constant full thermal power in absence of solar radiation. A first concept has already been developed and can be considered as the starting point of the present collaboration. CLEANERGY is asking for a collaboration in order to simulate the thermal system, to test a prototype and finally producing a final design of the system. The collaboration is carried on through a commissioned research, which should be terminated at the end of February 2015 with a total duration of 8 months. TECHNOLOGY CONCEPT The present concept is based on the use of a circumferential array of high temperature thermosyphons, partially filled with sodium. The sodium thermosyphon can work between about 400° and 1000°C and are made by INCONEL 625 or 718. The principle of thermosyphon is based on a gravity assisted closed thermodynamic loop where the condenser is positioned in a higher position with respect to gravity, in a way that the liquid sodium fall down to the evaporator where is again boiled and bring to the status of vapour, which expands toward the condenser side. The thermosyphons can be initially considered for the first prototype as made in form of circular tubes, vacuumed and filled partially with sodium. The condenser temperature should remain above the sodium solidification temperature and/or above a critical temperature, which allows a low value of the liquid viscosity. The diameter of the tubes should be defined in order to avoid, for a given power, the sonic limit and an acceptable heat flux. COLLABORATION GOALS The definition of the number, dimension and characteristics of the sodium thermosyphon is part of the present collaboration, together with an experimental thermal characterization of a first test prototype. CLEANERGY would like to re-use most of the components that have been designed and built. CLEANERGY is aware that technical and operational compromises are necessary in order to accomplish a feasible result in a reasonable time.
description: The data are collected from the results of the code we developed to simulate the sodium thermosyphons