Are we about to experience a DC boom with the growth of solar plus storage?
In case you missed it, Bloomberg New Energy Finance just revised its already bullish estimates for the growth in storage deployments upward – again, predicting a 122-fold boom in the installation of stationary energy storage over the next two decades. For its part, solar continues its high double-digit growth, making it the fastest-growing form of new generation.
Solar plus storage is rapidly entering the vernacular of popularly associated words and will no doubt soon be joining the ranks of peanut butter and jelly and ham and cheese in frequent use. Like those classic culinary combinations, solar and storage just go so well together. Pairing storage with solar allows solar to move from an intermittent source of energy to a dispatchable one. Achieving the base-load reliability storage offers solar will be a major step to allowing us to achieve our renewable energy goals and combat climate change.
Besides for their more frequent concatenation, solar and storage share another feature common: They are both DC energy sources, batteries are actually both DC sources and loads. When the sun’s rays hit solar panels, they generate DC current. Batteries store energy in DC. Of course, our distribution grid transmits power in AC. Amazingly though, most collocated solar and storage projects today connect the solar panel and the batteries on the AC side of the inverter, a technique referred to as ‘AC coupling.’ With such a topology, the energy generated from the Solar panels needs to make a long ‘round trip’ from the PV field, through an inverter back through another inverter before arriving at the battery.
While AC coupling still represents the most common way of connecting Solar and Storage, it does seem a rather unintuitive way to connect to a DC source (PV) to a DC load (storage). As logic would dictate, there is another method to combine solar and storage – DC coupling.