Operational Behaviour of SWT

Abstract

Alongside photovoltaics, small scale wind turbines (SWT) represent one of the few possibilities to yield energy in an environment friendly way in urban areas and thus a step towards “nearly zero energy”-buildings. However, due to a lack of experience in this regards, in many cases the impact of the environment on the SWT’s performance has been neglect. A poor energy yield, frequent faults and failures are the result [1]. On top of this, safety aspects as well as the repercussions on the building and the people living in it, need to be considered. Therefore, the objective of the presented work is to examine three different roof mounted SWT technologies (Savonius, Derrieus-Helix and three blade horizontal rotor) in simulation environment as well as under real life conditions while considering the influence of the roof shape. The main focus thereby is: A validation of currently available simulation models. An evaluation of the impact of complex obstacles on the local flow pattern as well as on the SWT under real working and environment conditions. A metrological evaluation of the repercussions of roof mounted SWT on its performance as well as on the building, the resident people and the direct environment in terms of noise, infra-sound, body-borne sound, vibrations and safety relevant aspects. In order to meet this target, two buildings (one with flat roof and one with gabled roof) are built in the “Lichtenegg” energy research park. While previous studies relied on simulations and wind tunnel tests on scaled models to gain understanding for the undisturbed operation of SWT [2, 3], the test infrastructure deployed in the presented work allows monitoring a SWT installed on the roof of a building under real life conditions. In order to get the full picture of the operational behaviour of the tested SWTs, the following parameters are measured: Inflow conditions at several points around the building. Energy yield and selected operating parameters of the SWT (e.g. power, RPM, …). Vibration on the SWT and on/in the building. Noise, infra-sound and body-borne sound. Since vibrations have caused issues on building mounted SWT in several occasions [1], the efficiency of vibration decoupling elements are evaluated. This is done by measuring the vibrations as well as structure-borne sound in the building over a measurement period of 3 months and comparing the results with those obtained with the custom fitted decoupling elements installed. Based on this comparison, recommendations regarding the use of vibration decoupling elements for building mounted small wind turbines are given. In regard to an estimation of the social and ecological impact of SWT, a technological impact assessment of the three deployed models is performed. Besides the Global Warming Potential, other factors such as energetic and financial amortisation periods are determined.