Common types of photovoltaic deployment include off-grid and on-grid systems. Off-grid systems are typically small (e.g., 10 s of kilowatts at most) and tied closely to an energy storage system such as a system of deep-cycle lead acid batteries or, in some cases, to a fueled gen-set. In an off-grid configuration, the energy stored in the battery acts as a buffer between energy production and demand. As such, short-term variability in the solar resource may not be an issue. On-grid systems, by contrast, may be quite large, with systems up to the 100 s of megawatts. To date, sizing of on-grid systems may be such that existing methods of handling load variability (e.g., by provision of ancillary services from generators on the grid) have been sufficient to ensure stability of the grid.
However, with advances in photovoltaic system technology, ever larger systems are being proposed and actually installed for use. Such larger systems may pose challenges for power management in at least two end markets, e.g., in island- or micro-grid systems or in very large photovoltaic plants integrated onto large grids. In either case, there may be restrictions on the maximum allowable ramp rates (both “up” and “down”) that are permitted in order to maintain grid stability. Typically, the proposed method of managing variability of renewable resources is to add an energy storage component. However, there may be a lack of reliable, commercially proven, and cost effective storage unit compatible with a facility scale at the 100 s of kilowatts level or higher.
USPTO Backgrounds
USPTO Backgrounds