Mini wind farms for urban roof tops
Despite the intensity felt when standing at the railing of a terrace on a tall building, the wind on top of buildings is typically too turbulent and slow to be of much use in powering a turbine. Scientists decided to accelerate and channel the wind with EU funding of the project 'Innovative design for wind energy capture in urban environments' (ROOF-CAPTURE) for a micro-generation solution in new or retrofit buildings. Through knowledge developed regarding air flow over the flat roof surface and a model of how to accelerate it, scientists developed a modular system in which 5-metre–long modules can be connected in parallel and extended along the roofline of the building. Photovoltaic (PV) and aerodynamic elements increase airflow through multiple small wind turbines, enabling them to significantly enhance overall output. Intelligent control maximises the system efficiency by optimising the positioning of either solar or wind energy harvesters depending on the best available resource at the time. Careful attention was given to ensure that the prototype system would be financially feasible and provide return on investment within 5 years in comparison to conventional wind turbines that typically have a payback period of 15–30 years. The prototype is installed and undergoing testing, expected to provide power, heating and passive ventilation to its host building with significant cost savings and a reduction in harmful emissions. Designed to be barely visible from the street level, the novel modular ROOF-CAPTURE systems could even make a significant impact on energy supply in windy seaside resort towns and national park hillsides. Bigger is not always better and ROOF-CAPTURE's micro-turbines are proving the point when it comes to renewable forms of energy for urban locations. The combined PV and aerodynamic elements could ensure that buildings get the energy they need — sustainably — when the Sun is shining or there is a breeze.