Technology in the renewable energy industry and especially in solar photovoltaics (PV) is advancing at a rapid rate, increasing efficiency and lowering cost. The next major development in solar PV is storage.
Energy Storage Is a Necessity
As utility circuits reach higher levels of renewable energy penetration the necessity for some type of “smoothing “ or energy storage becomes vital. Solar PV systems are considered “as-available” resources, meaning that the system is not always available. For instance cloud cover can significantly reduce the power produced thereby requiring the utility to quickly make up that lost power. A high level of renewable systems on a circuit can cause grid instability. In locales like Hawaii where rooftop solar is prevalent many circuits are reaching high penetration levels. In order for the utility to accept more solar PV in any particular area a storage component may be necessary.
This is what the Hawaiian Electric Companies Self Supply Distributive Energy Resource program (DER) program encourages.
There are many types of storage technologies on the market but only a few that are reliable and affordable. Rechargeable batteries have been traditionally used to store excess electricity in standalone PV systems. With prices rapidly declining, rechargeable batteries are increasingly being used to store surplus power to be later used at night. Batteries help stabilize the electrical grid by leveling out peak loads because they charge during periods of low demand and feed their stored energy into the grid when demand is high.
Battery Storage Technologies
Common battery technologies used in today’s PV systems include the valve regulated lead-acid battery– a modified version of the conventional lead–acid battery, nickel–cadmium and lithium-ion batteries. Lead-acid batteries are currently the predominant technology used in small-scale, residential PV systems, due to their high reliability, low self-discharge and investment and maintenance costs, despite shorter lifetime and lower energy density.
However, lithium-ion batteries have the potential to replace lead-acid batteries in the near future. They are being intensively developed and lower prices are expected due to economies of scale provided by large production facilities such as the Gigafactory being developed by Tesla in Nevada. In addition, the Li-ion batteries of plug-in electric cars may serve as future storage devices in a vehicle-to-grid system. Since most vehicles are parked an average of 95 percent of the time, their batteries could be used to let electricity flow from the car to the power lines and back. Other rechargeable batteries used for distributed PV systems include, sodium–sulfur and vanadium redox batteries, two prominent types of a molten salt and a flow battery, respectively.
Advances in inverter technology (the device that converts the power generated by the solar panels to usable AC energy) also allows the utility to manage the variability inherent in solar PV systems. Hawaii is the leader in developing protocols for inverter manufacturers to follow. New software and inverter technology permits the utility to increase the level of renewables on a circuit.
Solar Panels More Efficient
Solar panels also are achieving unprecedented levels of efficiency, but the biggest impact on the industry is the dramatically lower prices for the panels. Although Hawaii reached grid parity years ago (this is where the price of a solar PV system is equal to the traditional cost of electricity to the consumer) due to its high electric costs, the benefits of solar PV continue to benefit the consumer.