Photovoltaic systems, more commonly known as solar panels, are a great way to hedge against future increases in fuel costs that ultimately drive up utility rates. They’ve also been known to both increase the life of roofs, as well as property value. In fact, the State of California wants all new homes to be net-zero energy (i.e. they generate as much energy as they consume) by 2020. But what happens when all those solar arrays come online and start winding meters backwards?
The California Independent System Operator (CAISO) has actually thought about this question, and provided a chart with how they expect the future to look:
As you can see from the chart, beginning at 8am the net load (actual minus distributed generation like rooftop solar) drops. While everyone is at work, our solar panels are beginning to generate electricity. Since most of us aren’t at home, this energy goes straight to where it’s being used and you get a credit on your bill. The “duck belly” indicates just that, and it only gets bigger as solar becomes increasingly commonplace. This is fantastic, because when solar distributed generation supplies an abundant amount of electricity, more polluting power plants can be shut down or ramped down. However, as the workday comes to an end and we all drive home, the sun goes down, we kick on our heaters and air conditioners, resulting in a big load that solar panels can’t support. That sudden jump in demand around 6pm requires an orchestrated effort on CAISO’s side to ramp up massive plants to meet the state’s need. But ideally, the demand curve should be flat, making the need to purchase energy very stable and thus reliable and cheaper.
There’s been a lot of interesting ideas floating around on how to store the energy generated during the day, which would either smooth out or flatten the “duck’s head”. Smoothing or flattening out the demand curve would presumably make purchasing energy a lot easier and thus cheaper, because electricity has to be consumed (or stored) when generated—if you purchase too much, then you must consume or store it; if you purchase too little, you have rolling blackouts. Currently PG&E has a reservoir plant that pumps water from a lower reservoir to one higher when energy is in low demand (thus low costs) and feeds it through turbines when prices and demand are higher. Other ideas include sending excess power to electric water heaters (storing in the sense that you won’t have to heat water as much when hot water is in demand), storing the energy in concrete in the form of heat, forming huge ice blocks that cool large buildings, and of course large-scale batteries. With battery technology becoming more popular due to hybrid-electric, plug-in electric and all-electric vehicles, we could very well have our grid supported solely by renewables and stored energy technologies in the coming years.