Techno-economic analysis of energy storage devices for microgrid?s ramp rate control using bi-level evaluation method

Recently, energy storage devices (ESDs) have been widely deployed to alleviate high ramp rates in microgrids (MGs), thereby enabling the large-scale penetration of renewable energy resources (RERs) into utility grids. However, there is a lack of general guidelines to assist design engineers promptly evaluate the techno-economic benefits of ESDs under various RERs, RERs-load demand combinations and different ESD combinations. A bi-level evaluation method is devised in this study to assess the techno-economic feasibility of deploying ESDs to control the ramp rate of an MG, and comprehensive case studies are performed to answer the following ques-tions: (i) How do the fluctuations in a single RER, hybrid RERs, and a hybrid RERs-load demand combination influence the techno-economic aspects of ESD?, (ii) What type of ESD should be considered to obtain the best techno-economic benefits? The results suggest that the total energy storage requirements for ramp rate control of the MG can be lowered by hybridizing the RERs at a specific location. Specifically, the power and energy ca-pacities can be reduced by up to 19.4 % and 57.6 %, respectively. The results also revealed that failing to account for fluctuations in load demand when calculating the ESD capacity may result in an underestimation of the power and energy capacities of 7.6 % and 14.3 %, respectively. Regarding the type of ESD, lead-acid batteries were found to be the most expensive option to alleviate the ramp rate of the MG. The results indicated that lithium-ion batteries are the most cost-effective option compared with other types of sole/hybrid combinations. Moreover, it was determined that the initial investment cost and lifetime of the ESD are critical factors in selecting the most suitable ESD/ hybrid ESD for ramp rate control of a MG. In addition, the results demonstrated that hybrid combinations are only economical for stricter ramp rate constraints.