Case study

AT&T Off Grid – Reducing Generator Fuel Costs

OFF GRID SOLAR SITE UPGRADE TO SUPERCAPACITORS REDUCES COSTS - OPTIMIZES FUEL CONSUMPTION

AT&T Off Grid – Reducing Generator Fuel Costs

Lead Acid Batteries vs. Supercapacitors

Reduce maintenance and replacement

“The Supercapacitors will provide more than 25 years of service. We would need to replace the lead acid batterieis in 3 years with 2 cycles per day. The bonus was that the cost of the supercaps was lower than the lead acid batteries.”
Kyle Locke ,
Project Manager, AT&T Mobility

AT&T ANTELOPE CELL SITE

28.4 KWh of Storage

DC POWER PLANT

16kW Vertiv Rectifiers
7 Solar Controllers

15 KW SOLAR, 4,000 GALLONS OF PROPANE

  • 15 KWs of solar power
  • 4,000 gallons of propane

YEARS OF SERVICE

Supercapacitors vs. Lead Acid Batteries
Years of Service - Supercapacitors
27.4
Years of Service - Lead Acid Batteries
2.05

Off grid facilities that depend on renewable energy (solar, wind, etc.) require storage to maintain a power supply through the night or times when the renewable source is not producing. For critical infrastructure, fossil fuel generators will also be a component of the facility. If the renewable energy source and storage combination is not large enough to supply 100% of the power, then the fossil fuel generation becomes can be called upon to supplement. In either case the combination of renewable and storage will require cycling (charging and discharging) the energy storage system. Every energy storage system is limited by the number of times it can cycle.

 

Lead acid batteries have very limited cycling capabilities. In this case the lead acid batteries planned for the site were rated for 1,500 cycles. The supercapacitor modules are rated for 50,000 cycles. This particuar site cycles the energy storage system two times per day. Charged by the solar panels during the day and then by the generator at about 1:00 AM for the second charge in 24 hours. In our calculations we handicap the supercapacitors to 20,000 cycles. The end result is that the supercapacitors last more than 27 years while the lead acid batteries require replacement every 2 years.

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