Lead-acid batteries or Compressed air storage?
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Lead-acid batteries or Compressed air storage?

solar energy storage system

Lead-acid batteries or Compressed air storage? Featured

29 Jun 2022 / News

In terms of energy stored per cubic meter, prices, and payback period, researchers in the United Arab Emirates have evaluated the performance of compressed air storage and lead-acid batteries. They discovered the former has a payback period of just two years and a significantly lower Capex.

In an experimental setting, researchers from the University of Sharjah in the United Arab Emirates compared the storage capacity of compressed air energy storage (CAES) systems and traditional lead-acid batteries and discovered that CAES has a number of operational advantages over electrochemical systems. According to Abdul Hai Alami, the research's corresponding author, "Our CAES idea is suitable to various settings as it only requires tanks placed below." "but in hot areas it would really shine,"

Energy stored per cubic meter, cost, and payback period were used to gauge the effectiveness of both storage systems. Three loads—a 6 W fan, a 100 W lamp, and a 250 W drill—are operated in order to evaluate the performance of the system, according to the researchers. To ascertain the system's maximum capacity and evaluate it against theoretical estimates for voltage and time of discharge, a no-load condition was also carried out.
In order to test the CAES system's feasibility for industrial applications, the researchers additionally erected electrical cabinets to receive load wires from the generator. They underlined that they include "industry standard sockets for single phase and three phases with two different colors, guard against accidental electric shocks, give earth leakage prevention, and finally the coated panel provides protection against environmental factors."

The academics explained that operating the generator at its rated rotational speed in order to satisfy the minimum output voltage and operational frequency that will eventually be supplied to the end-users ensures the quality of the energy generated by the air motor, which is in turn activated by the kinetic energy from the storage air cylinders of the CAES system.
They calculated that the CAES system's theoretical maximum output power at 12 bar pressure should be 0.048 kW and that its theoretical roundtrip efficiency should be 86.6 percent. However, the system's experimental roundtrip efficiency was around 60%, and its maximum output power was 27 percent lower at 0.035 kW.

Larger air storage volumes to ensure constant pressure input to the air motors, better thermal management of air temperature, connecting more than one tank to the system and operating them in series or in tandem, and finally having an air motor/generator as a single unit to overcome mechanical losses are the main factors to enhance roundtrip efficiency, according to Alami. Another crucial element in improving operation and scaling up is the simulation and control of system operation, which allows input pressure fluctuation to match demand.
The researchers compared the costs of a 1400 kWh lead acid battery coupled with a 3.5 kW battery inverter and an 840 kWh/3.5 kW CAES configuration. The second configuration was anticipated to cost $130,307, and the third setup was CAES system at $23,780.

They noted that if the CAES capacity is solely a function of the storage tanks capacity and space available for them, the above-ground footprint of the system is small and comparable with a battery storage system. They added that depending on the charge-discharge cycles required from the battery and not including the price for battery cabinet, air conditioning, and the costs of the cooling load, breakeven point with a battery storage system can be achieved within 3-5 years. "In this situation, the payback period would be roughly 1-2 years," they stated.

The study group is now thinking about ways to speed up the development of the suggested storage technology. According to Alami, the technology is inherently compatible with off-grid solar farms and charges the tanks using high-pressure air compressors with a capacity of about 30 kW and a pressure of 100 bars. The primary technical challenges of the system are obvious and doable for such installations because tanks are readily available and suitable for underground burial. Additionally, the system can run EV chargers outside the grid.


Source: Compressed air storage vs. lead-acid batteries – pv magazine International (pv-magazine.com)