Solar power intermittency reduction using supercapacitors integrated with solar panels

Solar power is fundamentally very intermittent. The majority of the power is produced when the sun is shining brightly and is significantly reduced during substantial cloud cover and dust settlement. As solar Photovoltaic (PV) sources grow in use and the percentage of grid power met by them increases, grid stability becomes an increasingly important issue. In principle, the usage of an energy storage at the solar farm would reduce the effects of intermittency. However, batteries which are commonly used for storage of DC power are not a suitable option with intermittent power sources due to their high cost and low lifetimes (2000-3000 cycles). Supercapacitors have excellent power and cycling capabilities (100 000 cycles) make them ideal for storing and discharging energy from intermittent sources. They can be easily integrated with individual solar panels, offering an attractive option to reduce intermittency right at the panel level. In this paper, simulations have been carried out to understand the effect of intermittency on the PV system performance and it was found that the power output drastically decreases due to intermittency. Simulations show that a 50% solar shading causes a 50%-60% loss in solar power output. To manage the intermittency, we have designed and built two systems (Model 1 and Model 2) where a supercapacitor is being used as the storage element and is directly connected to the solar panels. The first model uses a simple relay based switching for reducing intermittencies. However, it is not efficient under all shading intermittencies. The second model uses a semiconductor switching integrated with dynamic threshold limiter which works successfully in all types of intermittencies for a period of 45 to 75 s (with a minimal switching time of 40 ms). The system proposed here is easily scalable to accommodate higher storage requirements. (C) 2015 AIP Publishing LLC.