Supercapacitor HESS for Frequency Regulation in Thermal Power Generation Systems

2023-01-03 [14:51]
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Supercapacitor-Based Hybrid Energy Storage Systems for Frequency Regulation in Thermal Power Generation Systems
Adam Song, Victor Sazonov, VINATech Co.

1. Global Safety Challenges Related to Using Lithium-Ion Batteries in Energy Storage Systems

According to some estimates, the global market of Energy Storage Systems (ESS) is expected to grow at a 30% rate annually. However, one of the factors slowing down the growth of the ESS market is caused by the variety of issues related to using lithium-ion batteries (LIB) as the most common energy storage type.

Although LIB-ESS is considered to be relatively cost-effective, there are certain problems related to durability, maintenance, safety, and non-eco-friendliness. In particular, in the case of an energy storage system for frequency regulation (FR-ESS), frequent charging and discharging caused by short-cycle frequency fluctuations shortens battery life, increases maintenance costs, and causes battery combustion.

Fire accidents have been occurring in battery energy storage plants globally (Figure 1). The most recent cases have been occurring in China, Korea, and the US. In October 2022, the 100MW energy storage plant at Yingge Haiyan Salt Field in Hainan Province had a fire accident raising concerns about the safety aspect of using LIB. Similar accidents were occurring in the US, including the ESS explosion in Arizona. South Korea has been dealing with over 30 ESS plant fire accidents over the past few years which raised the government’s concern about the safety of LIB in ESS and the possible measures that could help to improve safety and avoid fire accidents. Thus, any country in the world can experience fire accidents related to the usage of LIB-ESS.

Figure 1 - A breakdown of the stationary energy storage failure events (Source: BESS Failure Event Database)
The maintenance aspect of LIB has also been an issue that is hard not to take into account. Since batteries need to be replaced relatively more often, this creates additional ongoing expenses related to operating the ESS in the long term.

2. Supercapacitor Solution for Frequency Regulation Hybrid Energy Storage Systems in Thermal Power Generation: Increased Lifespan and Safety

There are different types of ESS in terms of functions and energy source technologies. We will consider the Frequency Regulation Energy Storage Systems (FR-ESS) used for the regulation of frequency in thermal power generation systems.

A stable frequency is essential for power management and power quality stabilization for the safe operation of customer appliances. However, the frequency can change depending on the changes in demand and supply. The frequency should be maintained within a certain range for a normal operation (± 3/100 Hz). The frequency regulation (FR) is implemented by using ESS which maintains the balance between power supply and demand by either providing additional power during peak times or storing the surplus of power when the power supply is in surplus.

The best alternative to a traditional LIB-based FR-ESS is a hybrid type of FR-ESS (HESS) that uses the existing lithium-ion batteries along with the new Supercapacitor Solution Technology developed by VINATech. The graph presented below visually illustrates how VINATech supercapacitors regulate the short and instantaneous frequency fluctuations (up to 30 seconds) while batteries regulate the long fluctuation cycles (longer than 30 seconds).
Figure 2 – LIB-ESS VS. HESS: Frequency Regulation (Source: KEPCO)

FR-ESS operates through several thousand to tens of thousands of cycles a day. In the case of HESS, the SC-ESS is responsible for 60% to 80% of the frequency adjustments, which is why lithium-ion batteries experience lower Depth of Discharge (DOD) and go through a fewer number of cycles which extends the entire lifespan by 1.87 times.

According to multiple recent studies, the lifespan of lithium-ion batteries is significantly increased in Hybrid Energy Storage Systems that utilize supercapacitors. Let us consider the example of a 5MW HESS. In this system, the supercapacitors and batteries are used in the proportion of 1 to 4. We have analyzed the total cost of ownership of a traditional LIB-ESS and HESS based on VINATech Supercapacitor Solution technology. All the estimates are presented in terms of current price levels and may vary depending on different factors.
Here is the simple calculation of the total cost of ownership of 5MW LIB-ESS and 5MW HESS that uses VINATech Supercapacitor Solution:

1. 1MW LIB Cost = $115,000; 1 MW SC Cost = $268,000;
2. 5MW LIB-ESS Cost: $115,000*5 = $575,000;
3. 5MW LIB-SC Hybrid ESS Cost: 4MW LIB + 1MW SC = $115,000*4 + $268,000 = $728,000.

Table 1 visually compares the 20-year total cost of ownership for the analyzed systems.
5MW ESS Type Installation Cost Life Cycle 20-Year Cost 
LIB ESS  $575,000 10 years $1,150,000
LIB-SC Hybrid ESS  $728,000 20 years $728,000

Table 1 – LIB-ESS and LIB-SC ESS: 20-Year Total Cost of Ownership (TCO)
And since supercapacitors are considered to be eco-friendly energy storage devices that don’t explode or combust even when being exposed to open fire, creating a hybrid system that includes both batteries and supercapacitors helps to decrease the number of batteries used in the system by 20%, increase their life span by redistributing the role of regulation of the short-cycle high-power output fluctuations to supercapacitor systems and, as a result, decrease battery waste and increase eco-friendliness of the whole system. Moreover, supercapacitor HESS can potentially be more beneficial not only for an operator but also for the end consumer, resulting in reduced electricity bills. To summarize, HESS is a strategy that compensates for the disadvantages of LIB and maximizes the advantages by using the most cutting-edge supercapacitor solutions developed by VINATech and, as a result, improves the durability, maintenance, safety, and eco-friendliness and also ensures efficient power quality stabilization with low maintenance costs of the Frequency Regulation Energy Storage Systems.

3. VINATech Supercapacitor Solution for FR-ESS

Currently, VINATech Supercapacitor Solutions are considered to be the best in the world on the market of FR-ESS due to the following main reasons:

1. Master CMS Technology (Capacitor Management System)
2. Firmware, SOC/SOH Algorithm Technology (Operating System, Battery Charge/Discharge Status, Battery Life Prediction Algorithm)
3. Quick Development and Testing Cycles
4. Experience and expertise from collaborating with KEPCO (Korea Electric Power Corporation)
Figure 3 – VINATech Supercapacitor Solutions for FR-ESS
If you are interested in increasing the durability, decreasing maintenance costs, improving safety, and eco-friendliness of your Frequency Regulation Energy Storage System, feel free to contact us to discuss how we can help you develop the best-customized supercapacitor solution for your operation.

Figure 4 – VINATech Supercapacitor Solutions for Korea Electric Power Corporation (KEPCO)

4. About VINATech
VINATech is a global energy solutions provider specializing in the manufacturing of supercapacitors and fuel cell components. VINATech started its business in 1999 and became an elite energy solutions provider for the global leading companies in a variety of industries such as automotive, IoT, consumer electronics, logistics, healthcare, renewable energy, and many others. VINATech Headquarters and R&D Center are located in Jeonju, South Korea. VINATech’s products are currently produced in factories in South Korea and Vietnam.
5. Sources
1. U. Akram, N. Mithulananthan, R. Shah and S.A. Pourmousavi, "Sizing HESS as inertial and primary frequency reserve in low inertia power system", IET Renewable Power Generation, vol. 15, no. 1, pp. 99-113, 2021. https://ietresearch.onlinelibrary.wiley.com/doi/full/10.1049/rpg2.12008

2. Cao Y. Optimal sizing of hybrid energy storage system considering power smoothing and transient frequency regulation, Int J. Electr. Power Energy Syst (2022) https://www.sciencedirect.com/science/article/abs/pii/S0142061522002575

3. Punna, S., Manthati, U.B. Optimum design and analysis of a dynamic energy management scheme for HESS in renewable power generation applications. SN Appl. Sci. 2, 495 (2020). https://doi.org/10.1007/s42452-020-2313-3 https://link.springer.com/article/10.1007/s42452-020-2313-3

4. BES Failure Event Database, Electric Power Research Institute: https://storagewiki.epri.com/index.php/BESS_Failure_Event_Database  



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