Experimental demonstration of regenerative wind farming using a high-density layout of VAWTs

Abstract. The present study extends the idea of the VAWT "vortex generator mode" for wake recovery on a wind farm scale, working towards the concept of "regenerative wind farming", where upstream turbines entrain vertical momentum for those downstream. An experimental wind tunnel demonstration of the "regenerative wind farming" concept for an array of nine H-type VAWTs arranged in a 3x3 grid layout is performed. Volumetric particle tracking velocimetry measures the wake within the simulated wind farm while using two "vortex generator modes" achieved through fixed blade pitch. The results demonstrate the strong dependence of the wake topology of a VAWT on the streamwise vorticity system, which can be effectively modified by pitching the blades and subsequently changing the load distribution of the different quadrants of a VAWT. An increase in momentum entrainment in the wake is observed for both "vortex generator modes" of operation, highlighting the potential towards the goal of "regenerative wind farming." The derived available power within the farm increases by factors of 6.4 and 2.1 for the pitch-in and -out cases compared to the baseline case, respectively, considering potential rotors directly in line with those upwind.