Let us continue to use the hypothetical case study from an earlier article:
“I just returned from Houston and my friend got a message on her cell phone that the power was out at their house, but that it would be back on in two hours, so we kept playing tennis. When she checked the app, she also showed me her car was only charged 80 percent, but it was OK, because she was using her solar cells to charge it and it would be complete in three hours. She smiled and said she sold $75’s worth of power last month back to her retailer and it paid for lunch today. She said her electricity bill now only includes a connection charge, unless she uses an unusual amount of power. I am calling PSE to see what they can provide.”
Case credit to Charles Filewych, CEO, Smart Grid Interconnect. Used here with permission.
Using this same case study, let us focus on another aspect of utility transformation — energy storage. Electric energy storage (EES) is a set of technologies capable of storing previously generated electric energy and releasing that energy later. It uses forms of energy such as chemical, kinetic, thermal or potential energy to store energy that will later be converted to electricity. So, what does this mean?
- Electric energy storage mechanisms: Energy can be stored using a variety of mechanisms that cover chemical, hydro (potential energy), flywheel (kinetic), thermal and other new and innovative mechanisms to store and discharge pregenerated energy.
- Charge/discharge capacity: The mechanisms to store and discharge energy also drive the potential applications of this specific storage mechanism that can range from high energy to high power.
- Speed of discharge: These same mechanisms that determine energy versus power also drive the charge/discharge rates. Flywheel storage, for example, can deliver energy extremely fast and can be used to provide regulation support to the grid, whereas Li-ion-based storage mechanisms are used in cars and buildings to deliver a lot of energy over a sustained period.
- Scale/size of storage: The type of storage mechanism also determines the scale to which these devices can size up, in terms of energy and/or power delivery. Some pumped hydro can deliver power in the hundreds of MW over a sustained period, whereas flywheels deliver multiple MW of power in very short periods of time.
Who are the users here?
Like DERs from the previous article, storage mechanisms can be installed and used by a broad range of stakeholders:
- Generation and independent power producers: These are the owner-operators of the power plants and, especially when it is a pumped hydro plant, they can both generate and/or store energy. The decision to either generate or store energy is made by the operator based on economics.
- RTO/ISO: Wholesale market operators use storage mechanisms such as flywheels to provide localized sources of regulation support where needed and get around congestion zones.
- Individual customers (residential and/or commercial/industrial): The entry of systems like the Tesla Powerwall have also thrust the residential customer into the limelight. Storage mechanisms provide an alternate mechanism for the customer to offset their solar/PV installations by storing energy when it is more than their localized needs and discharging at night when the sun is not shining.
- Utilities: In many states, utilities can install storage to avoid substation enhancements and defer capital expenditure. By installing storage, the utility can smooth out the load, thereby reducing the need for peak infrastructure support.
Conclusions and closing thoughts — how does the utility transform itself with these disruptors from the edge?
The future in this area is moving more and more toward increased penetration of DER in the utility, most of which is coming from customer installations. From an operations perspective, the variability of power generation from these DERs is already causing perturbations and quality issues at the utility. It is to be expected that as the penetration of DERs from renewables increases, the operational problems will also increase.
Enter the disruptor — storage. These types of storage have multiple uses:
- Power quality: To assure continuity of quality power and smooth out the variability of power from the DER.
- Bridging power: To assure continuity of service when switching from one source of energy generation to another.
- Energy management: To decouple timing of generation and consumption of electric energy. Load leveling, which involves charging of storage when energy cost is low and discharging when cost is high.
The utility industry is transforming itself from the present one-way flow of energy from a centralized set of a few large generators to a distributed world in which a significant percentage of generation comes from large numbers of small generators distributed across the grid.
Storage is that disruptor which will allow this transformation to happen.
Author’s note: This is part of a series of articles written by this author for Intel.
The author: Dr. Mani Vadari is founder and president of Modern Grid Solutions (MGS), delivering consulting and training services to a global set of smart grid companies seeking deep subject matter expertise in setting the business, technical and strategic direction to develop the next-generation electric/energy system. Dr. Vadari’s Smart Grid Training is designed to educate the executives and management of the new workforce, and his book, “Electric System Operations: Evolving to the Modern Grid,” is receiving five-star reviews by industry leaders. Dr. Vadari has published more than 50 articles and 30 blogs in leading business and technical journals.