Monday, August 12, 2013
But it CAN make sense for utilities—largely because they can make those batteries perform far more tasks, each of which has a payback value. Stacking those services a battery performs can make a compelling argument for them.
For this second piece in a series on Hawai`i energy storage , we are relying primarily on a new industry/government report, the DOE/EPRI/NRECA Electricity Storage Handbook for 2013, which was released earlier this summer. It is available without cost here.
The report makes the point that one of the most critical functions of a battery system is to make energy travel through time. That is, they let you collect energy at one time, and hold it for delivery at another time.
That is particularly valuable if there are times when you don’t have enough generating capacity to meet the load, or if (think solar, wind) there are energy sources whose production doesn’t coincide with when you need the power.
We won’t go into lots of detail here. You can find a much broader discussion in the 340-page report. But briefly, some of the services include:
TIME SHIFTING, LOAD SHIFTING. The energy time-travel service discussed above.
COST CONTROL. A good storage system may not only be able to shift energy from periods of periods of excess to periods of shortage, but may also be able to shift energy from periods when it’s cheap to periods when it’s expensive. (Often, these may be the same.)
COST DEFERRAL. Meeting peaks in demand with stored energy may allow you to hold off on spending new money for generation to meet those peaks. The construction of transmission and distribution equipment can also be deferred through energy storage.
CUTTING GENERATOR WEAR AND TEAR. Since many generators wear more quickly if their output needs to vary, a storage option can reduce wear by taking up the variable load while the generator operates at stable output.
SPINNING RESERVE, SUPPLEMENTAL RESERVE. This refers to using a battery as a source for quick power delivery in case of a generator failure or transmission problem. Spinning reserve is defined as that which can be delivered within 10 minutes, while supplemental reserve is electricity that can be available within an hour. Utilities often meet this need now by burning oil to keep generators hot and running without load—so they can be quickly called into service.
BLACK START. This is a term for starting up a system that has shut down entirely. Many generators need power (think pumps, blowers, etc.) to start up. You can fire up a diesel generator to power the startup of a big steam generator, or you can use stored energy to deliver that power immediately.
VOLTAGE SUPPORT, FREQUENCY RESPONSE. In being able to respond quickly to add power or remove power from the grid, some kinds of storage can provide reliability, stability and better power quality.
As discussed earlier, it might not make sense to pay for a storage system for just one of these things, but it might if you consider all the potential uses. Example: having a massive battery just to provide black start capacity might be cost prohibitive, but if that battery also allows you to shift energy through time, reduce generator wear and create spinning reserve—then it might make economic sense.
It is clear that not every storage technology is appropriate for every one of these energy services. Example: pumped hydro and compressed air energy storage are great for bulk power management, but may not be much use for frequency response. And while high-energy supercapacitors might be wonderful for maintaining power quality, they’re not so good for load shifting.
In our next segments, we’ll begin looking at some of the energy storage options that are available now, or may soon be ready.
© Jan TenBruggencate 2013