Spinning Reserves: The Rapid-Response Team of the Electrical Grid
You flip the switch and the lights come on. There’s no thought of the lights coming on, or at least that’s the case for me. But have you ever wondered how our energy markets provide a constant and reliable supply of electricity, especially during unforeseen supply shortages? This is where spinning reserves come into play. In this blog post, we’ll dive into all things spinning reserves, exploring what they are, how they work, and why spinning reserves are crucial to preserving a stable electricity grid.
What Are Spinning Reserves?
Operating reserves are generation capacity on standby to provide electricity to the market to meet demand in a short amount of time when supply disruptions occur like a generator going offline. Spinning reserves, like non-spinning reserves, are a type of operating reserve.
You can think of a spinning reserve as a backup team of generators. They’re always on standby ready to supply electricity to the market when it’s needed quickly. Spinning reserves are one tool that’s used as a safeguard against blackouts, which market operators are always trying to prevent.
Spinning Reserve vs. Operating Reserve
Spinning reserves are a subset of operating reserves, which encompass different types of generation resources that can be called upon to meet demand in the market. Operating reserves include spinning reserves, non-spinning reserves, and demand response programs, whose goal is to supply the electricity grid with power.
Non-spinning reserves, as the name suggests, are not running and synchronized with the electricity grid, unlike spinning reserves. Instead, non-spinning reserves are offline but can ramp up quickly, typically within 10 minutes. Both spinning reserves and non-spinning reserves play a crucial role in the stability and reliability of the electricity grid.
How Spinning Reserves Work
Now, let’s take a peek into how spinning reserves operate. To set the stage, picture a power plant comprised of multiple generators. These generators are constantly running but not at full capacity, allowing the generators to increase their output when called upon. In other words, a spinning reserve.
The market suddenly has an increase in demand or a large power plant trips offline. Within seconds, the grid operator calls upon these spinning reserves to ramp up their generation. The market needs the additional generation to balance supply and demand. Think of spinning reserves in this scenario as a team of sprinters ready to dash to the finish line to finish out a relay race.
The Role of Batteries in Spinning Reserves
Like solar and wind over the past 20 years, the cost curve for battery energy storage systems continues to decline. Batteries, like spinning reserves, offer another type of operating reserve for the market. Due to its ability to quickly dispatch its stored electricity, batteries offer an excellent way to provide supply to the market when called upon by a grid operator.
Intermittent resources like solar and wind continue to advance the energy transition. One of the missing components of these generators is the ability to provide firm (constant) generation. The ability of a battery, either as a stand-alone resource or coupled with a solar or wind project, can provide more firepower to the reliability and stability of the grid.
Spinning Reserve Requirements and Markets
There are seven independent system operators (ISO) and renewable transmission organizations (RTOs) in the US. Each of these grid operators has different requirements for spinning reserves. Generally speaking, ISOs and RTOs strike the balance between providing reliability with cost-effectiveness.
That’s the goal, right? Electricity consumers want a constant and reliable source of supply no matter what’s happening in the market. Yes, there are outlier extreme events like wildfires out west, hurricanes in the southeast, or snow storms in the northeast that knock out the supply of electricity. How the market can quickly respond to grid disruptions is one key area that spinning reserves are suited for.
The Price of Reliability
In conclusion, there’s a trade-off involved with spinning reserves - generators aren’t running at maximum capacity which can be inefficient and costly. However, that’s the price you pay to have reliability. Spinning reserves are the emergency first responders for the electricity grid, springing into action when called upon. So, the next time you’re at your office and turn on the lights, know that spinning reserves are on standby waiting to be called upon at a moment’s notice.
