Why Storage? Part 3: Time of Use Optimization

by Matt Maroon

Energy storage can do a number of jobs when connected to a solar-enabled residence. 

We’ve already outlined some of the benefits of energy storage when it comes to maximizing solar usage— self-consumption, backup power during  outages, and islanding (increased autonomy).  Another useful application is time of use optimization. For the homeowner, this means using energy from your batteries when variable rates for grid power are high due to increased demand based on time of day/year. Batteries can be charged from the grid overnight when power is cheapest and then, for example, used to power your AC at the hottest (and most expensive) time of day. But, time of use optimization has other major advantages. Did you know that energy storage, even when installed at private residences, can contribute to solving larger grid and environmental issues?  

→ Did you miss Parts 1 & 2? Read them here:
Why Storage? Part 1: Solar Self-Consumption    |    Why Storage? Part 2: Backup Power & Islanding

The duck curve. If you’ve kept up with energy storage initiatives (or read arcane CAISO policy papers) you’ll be familiar with this discussion.  If you haven’t, the duck curve is an overarching hypothesis about how solar power generation impacts the overall centralized grid network.  Unfortunately, for all of the benefits of large scale utility and distributed solar generation, the fact is that these resources are not dispatchable— meaning that we cannot pick and choose when we want that power to be put onto the grid.  The natural result of increasing the number of solar installations is an increase of power on the grid from solar starting at 9:00am and falling off around 5:00pm. This leaves grid system operators to cope by ramping traditional generators of power up and down typically natural gas generators—  all resulting in increased emissions and efforts to maintain grid stability.AquionCharts-time-of-use.png

A diagram depicting how energy storage can be used at home for time of use optimization.

Enter: energy storage. Even in the smallest residential installation, coupling energy storage with solar will help offset the duck curve by storing the extra PV in batteries instead of pushing it back onto the grid.  More and more energy storage systems have the ability to interact with the utility SCADA system, meaning that grid system operators (those responsible for maintaining grid reliability) could dispatch these energy storage systems to charge/discharge based on grid needs.  If you aggregate millions of homes with 6-10 kWh of energy storage in each, the grid operator now has a significant tool at his or her disposal: the ability to better manage the ramping-up of solar power in the morning  and the increasing load in the early evening  when solar power is beginning to wane.

What does all of this mean?  While society will not be able to wean itself off fossil-fuel power generation in the near future, we can make significant strides to fully utilize the sources of renewable power that we do have.Energy storage is the key to making this happen, from the smallest residential systems to large scale utility systems.  


See how a  home in Germany is using energy storage to save on electricity bills, increase autarky, and more.

germany grid tied residential solar

Topics: Grid Tied, Residential

Written by
Matt Maroon
Matt is Aquion Energy's vice president of product management. He joined Aquion Energy in early 2014, bringing with him over 10 years of experience scaling new energy storage electrochemistries from the laboratory into commercial products.


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