Italian researchers have investigated how flywheel storage and reversible solid oxide cells could be integrated with lithium-ion batteries in solar-powered mini-grids. They found that flywheels combined with batteries could be the cheapest option for power smoothing.
“Our analysis noted annual solar electricity production and electricity load is a real dataset,” said researcher Linda Barelli pv magazine. “We included a statistical analysis to obtain the most representative days, dynamic modeling of the storage systems, simulations to determine the size of the components and extrapolate the evolution of the annual battery state of charge, the estimation of the battery life using the rainflow cycle calculation algorithm. and a detailed financial assessment of the levelized cost of energy (LCOE) and the levelized cost of storage (LCOS) , including subsidies for own consumption.”
The Italian group presented their findings in the paper “Battery-Hydrogen vs. Flywheel-Battery Hybrid Storage Systems for Renewable Energy Integration in the Mini-Grid: A Techno-Economic Comparison” published recently Journal of Energy Storage The researchers said the two storage system configurations are designed for applications in mini-grids equipped with solar power plants.
Their modeling was based on a mini-grid with a 245 kW solar power system incorporated for common AC bus through an inverter where connection to the medium voltage network via a transformer. They considered the following main parameters: dlow power, daily power bandwidth, the ratio between daily bandwidth and average power and daily average power ramp.
For the flywheel-battery system, the researchers considered a low–speed steel mechanical flywheel ceramic bearings and an operating speed range is 3500 rpm th 8500 rpm. In the rSOC battery assembly, they hypothesized an rSOC stack that can can achieve round trip efficiency 38-48%. For battery–flywheel system, the battery size was 260 kWh and the flywheel capacity was 180 kW. In the rSOC battery architecture, the battery capacity was 450 kWh and the power of rSOC was up to 80 kW.
The scientists assumed the costs of the solar power system to be 970 euros ($1,058)/kW and 411 euros/kWh for the batteries. For the RSOC system and the flywheel technology, they estimate initial costs of €2,930/kW and €162/kW.
“It is noteworthy to mention that because of the current energyy crisis, such an the index has risen rapidly since the last months of 2021,” the researcher said. “Therefore, LCOE the assessment is based on a short–Long-term electricity price instability may lead to a fleeting result.”
The research team found that based system rSOC and batteries is LCOE 0.22 euros480/kWh when based flywheel and batteries reached € LCOE0.18/kWh.
“None of the proposed schemes will achieve market valuet parity, and the results are quite far from the 2020 IRENA target for solar PV systems,” said.
The rSOC+battdifferent the combination can potentially reach network parity when the market price is above 0.38 euros0/kWh and the flywheel battery system can become competitive when the market price exceeds €0.320/kWh.
“The main result of this integrated method appears to be that the feed-in premiums allow the flywheel/Li-ion battery storage system to achieve an LCOS that agrees with the 2021 average market parity,” said Barelli. “I see good applications for this configuration in power balancing and hybrid storage systems to handle the most variable profiles by reducing the load on other systems, which can then be reserved to meet storage needs over a longer period of time, increasing system efficiency and durability.”
