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:
Source: CAISO.com
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.
