• Energy Research
• Open Access close
• Restricted close
• Open Source close
• CA close

Abstract. The assessment of wind conditions in complex terrain requires the use of Computational Fluid Dynamics (CFD) simulations incorporating an accurate parameterization of forest canopy effects and variable thermal stability effects. This study aims to investigate how incorporating the presence of trees can improve flow predictions. A three-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations model is set up using OpenFOAM to simulate the flow over a complex terrain site comprising two parallel ridges located near Perdigão, Portugal. A 7.5 km × 7.5 km terrain of the Perdigao site is constructed from elevation data centered around a 100 m met-mast located on the northeast ridge. A 30-min averaged stationary period corresponding to near-neutral conditions on a single met-mast tower is simulated. The impact of incorporating different source terms is studied such as forest canopy, Coriolis forces as well as also buoyancy forces. The prediction capability of the models is analyzed for different groups of towers on the South-West ridge, inside the valley, and on the North-East ridge based on the flow topology. The inclusion of a canopy model is shown to improve predictions close to the ground for most of the towers, while reducing prediction accuracy on top of the ridges, illustrating the need to represent terrain heterogeneity.

Abstract. The assessment of wind conditions in complex terrain requires the use of Computational Fluid Dynamics (CFD) simulations incorporating an accurate parameterization of forest canopy effects and variable thermal stability effects. This study aims to investigate how incorporating the presence of trees can improve flow predictions. A three-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations model is set up using OpenFOAM to simulate the flow over a complex terrain site comprising two parallel ridges located near Perdigão, Portugal. A 7.5 km × 7.5 km terrain of the Perdigao site is constructed from elevation data centered around a 100 m met-mast located on the northeast ridge. A 30-min averaged stationary period corresponding to near-neutral conditions on a single met-mast tower is simulated. The impact of incorporating different source terms is studied such as forest canopy, Coriolis forces as well as also buoyancy forces. The prediction capability of the models is analyzed for different groups of towers on the South-West ridge, inside the valley, and on the North-East ridge based on the flow topology. The inclusion of a canopy model is shown to improve predictions close to the ground for most of the towers, while reducing prediction accuracy on top of the ridges, illustrating the need to represent terrain heterogeneity.

Abstract Thermal energy storage (TES) systems are growing to a relevant role in solar cooling applications. Hence, high energy density is a desirable property of the TES system. Phase change materials (PCM) helps to increase this characteristic. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly of three parts: heating system, cooling system, and different storage tanks. Two identical storage tanks based on the shell-and-tubes heat exchanger, one of them including 196 squared fins in the bundle of the tubes and the other without, were experimentally tested. Hydroquinone was selected as the storage material, having a latent heat of 205 kJ/kg and a phase change temperature between 168 and 173 °C. The aim of this paper is to test experimentally, and compare the average effectiveness of the TES systems analyzed using PCM for solar cooling and refrigeration applications. It was found out that for the same tank configurations (shell-and-tubes) even changing drastically the dimensions of the tank or the number and the diameter of the tubes, the average effectiveness curve proposed in the literature fits well with the results showed here.

Abstract Thermal energy storage (TES) systems are growing to a relevant role in solar cooling applications. Hence, high energy density is a desirable property of the TES system. Phase change materials (PCM) helps to increase this characteristic. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly of three parts: heating system, cooling system, and different storage tanks. Two identical storage tanks based on the shell-and-tubes heat exchanger, one of them including 196 squared fins in the bundle of the tubes and the other without, were experimentally tested. Hydroquinone was selected as the storage material, having a latent heat of 205 kJ/kg and a phase change temperature between 168 and 173 °C. The aim of this paper is to test experimentally, and compare the average effectiveness of the TES systems analyzed using PCM for solar cooling and refrigeration applications. It was found out that for the same tank configurations (shell-and-tubes) even changing drastically the dimensions of the tank or the number and the diameter of the tubes, the average effectiveness curve proposed in the literature fits well with the results showed here.

Abstract Thermal properties of the different building envelopes, such as thermal transmittance in steady state, heat storage capacity and dynamic thermal responses, must be taken into account during the design phase of buildings. The evaluation and measurement of these parameters in multilayered samples are difficult because of the irregular morphology of the used materials and the difficulty in providing the well-controlled environment needed for the measurements. A new equipment has been designed to measure the thermal response and heat capacity of composite walls of different materials simulating real building envelopes. The equipment presented in this paper was used to test the improvement in the thermal response of a building envelope due to the incorporation of PCM. This study is focused on wood structural panels attached to a gypsum board, which is either impregnated or not with PCM. The four edges of the composite sample are properly insulated to ensure one-dimensional heat flow. The two faces of the sample are exposed to controlled environments heated and cooled by copper coils with thermo stated water supplied by water baths. The measured surface heat fluxes at both surfaces of the sample and temperature distribution in the sample provide accurate assessment to thermal mass and dynamic response of the composite wall, while the steady state measurements provide an accurate estimate of its effective thermal transmittance.

Abstract Thermal properties of the different building envelopes, such as thermal transmittance in steady state, heat storage capacity and dynamic thermal responses, must be taken into account during the design phase of buildings. The evaluation and measurement of these parameters in multilayered samples are difficult because of the irregular morphology of the used materials and the difficulty in providing the well-controlled environment needed for the measurements. A new equipment has been designed to measure the thermal response and heat capacity of composite walls of different materials simulating real building envelopes. The equipment presented in this paper was used to test the improvement in the thermal response of a building envelope due to the incorporation of PCM. This study is focused on wood structural panels attached to a gypsum board, which is either impregnated or not with PCM. The four edges of the composite sample are properly insulated to ensure one-dimensional heat flow. The two faces of the sample are exposed to controlled environments heated and cooled by copper coils with thermo stated water supplied by water baths. The measured surface heat fluxes at both surfaces of the sample and temperature distribution in the sample provide accurate assessment to thermal mass and dynamic response of the composite wall, while the steady state measurements provide an accurate estimate of its effective thermal transmittance.