Duck Curve and Battery-Supercapacitor Hybrid Energy Storage System

Due to huge price reduction and being the clean source of energy, solar energy is being deployed largely. While shifting towards the solar energy, not only the fossil fuel deployment has decreased, but also it has reduced the impact of gases released by using conventional sources of energy. However, the weather conditions affect the output power of PV generators. Moreover, PV generators can only generate electricity during the day. That is why it creates an imbalance in demand of load between day and night. Since the output of PV is time dependent, also there are various electric generators in the power plant fleet. This affects the actual benefits that could be had from solar PV in various regions. All this is shown by the Duck Curve. The Duck Curve was first published in 2013 by the independent operator of the California system (CAISO). The chart shows the impact of increasing the solar deployment. This chart also shows the ramp rates and range of the demand curve, which the conventional sources of energy would not be able to handle economically. In addition to this, due to higher solar deployment, more energy than the actual demand is produced which leads to over-generation. This would lead to its curtailment, which would increase its cost and reducing its environmental benefits. These issues can be overcome by adopting various energy storage techniques in the system depending upon the requirement of that system. The energy storage provides an efficient way to minimize the fluctuations in the generated power and delivering steady power to the grid. The utilization of the Hybrid Energy Storage System (H.E.S.S), which consists of a battery and a supercapacitor, is one of the methods used to store electrical energy for a short period. The batteries have a high energy density and a low power density. The high energy density of batteries means that they provide a constant current over a long period. However, the low power density of batteries limits their ability to provide immediate changes in energy requirements. Thus, as high intensity energy sources, super capacitors operate in modern H.E.S.S systems to compensate for the shortcoming of the batteries. Moreover, batteries are very expensive and fluctuations in their current result in reduction of their life cycle. Super capacitors can cover load current fluctuations, resulting in a smooth current of batteries.