Associate Laboratory of  Energy, Transports and Aeronautics

Funder

Organizational Unit

Publications

Thermal resistance of solar volumetric absorbers made of mullite, brown alumina and ceria foams under concentrated solar radiation

Publication . Oliveira, Fernando Almeida Costa; Fernandes, Jorge Cruz; Galindo, José; Rodríguez, José; Cañadas, Inmaculada; Rosa, Luís Guerra

ABSTRACT: Three semi-closed open cell ceramic foams, namely mullite, brown alumina and ceria-based materials, were subjected to thermal cycles by direct concentrated solar irradiation to study their thermal resistance in view of their potential application as photothermal devices, such as volumetric solar absorbers. After cycling, the extent of the damage in the samples was determined by measuring the retained crushing (compressive) strength. The extent of the damage was found to depend on the composition, the applied surface temperature difference (Delta T) of thermal cycling and the temperature gradient across the foams. It was found that the retained crushing strength gradually decreased with an increase in Delta T and was independent of the number of thermal cycles in the range investigated. The ceria foams displayed the poorest thermal shock resistance. Experimental data fit the Gibson-Ashby model for the thermal shock resistance of ceramic foams, for a constant C = 0.65.

2019Journal article

Open access

Portland cement clinker production using concentrated solar energy : a proof-of-concept approach

Publication . Oliveira, Fernando Almeida Costa; Fernandes, Jorge Cruz; Galindo, José; Rodríguez, José; Cañadas, Inmaculada; Vermelhudo, V.; Nunes, A.; Rosa, Luís Guerra

ABSTRACT: The aim of this work was to demonstrate the feasibility of producing Portland cement clinker upon direct exposure of the raw materials under concentrated solar radiation using the PSA high concentration solar furnace SF40. For this purpose, a short thermal cycle ( < 40 min) was devised including 5 min dwell times at temperatures in the range 900-950 degrees C and 1250-1300 degrees C, followed by 10-15 min at 1500-1550 degrees C. The chemical and mineralogical data of the grey clinker produced are encouraging since values of 51.0 +/- 6.9% C3S, 22.7 +/- 5.3% C2S, 8.6 +/- 0.4% C(3)A and 10.8 +/- 0.7% C(4)AF are similar to those observed for conventional clinker used for the production of Portland cement in accordance to EN 197-1 standard. White clinker, in turn, could not be produced by direct irradiation in this setup conditions because of its low absorptance of solar energy.

2019Journal article

Open access

Numerical investigation of a novel hybrid wind-wave system and its variable pneumatic chamber volume control

Publication . Marreiros, João; Portillo, Juan C. C.

ABSTRACT: This work presents a numerical investigation of a novel control system for a new hybrid wave-wind energy floating platform. It comprises the design of a control system for controlling the variable pneumatic chamber volumes coupled with the hydrodynamics of the floating platform to maximise wave power production. The numerical model is developed in the object-oriented non-casual language Modelica, for which a new module for the control system was integrated into an existing package developed at IST/ULisboa. A sensitivity analysis of the main control parameters in terms of techno-economic parameters is performed and analysed. Results show that the envelope of control parameters’ values for increasing conversion efficiencies and power production is narrow, and an increase of about 30% was achieved with the best case compared with the base case. Moreover, it was observed that the variable volume of the pneumatic chambers shows significant variations on a part of the operational periods typical of the west of Portugal.

2025-09Conference paper

Open access