Case study

AT&T Mt Patterson 2019

SUPERCAPACITORS ENABLE WINTER OPERATION WITHOUT GENERATOR REFUELING

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LEAD ACID BATTERIES VS. SUPERCAPACITORS

Genset Runtime:

Lead Acid Batteries required generator to run 4,824 hours per year

Supercapacitors required generator to run 1,023 hours per year

"This site is under 10' of snow from November to May. With lead acid batteries we would have run out of fuel by January and wouldn't be able to keep the site on air. With the supercaps, we only refuel the generator tanks 1 time per year and it's only 1/2 empty when we do. We could not keep this site going year around without supercaps."
Charles Newdigate ,
Cell Technician, AT&T Mobility

85.2 kWh:

42.6 KWh of Supercapacitors

POWER HANDLING

16kW Vertiv Rectifiers
7 Solar Controllers

SOLAR & GENERATOR POWER SOURCES

15 KW of Solar power

6,000 Gallons of Propane

COST

4G and 5G implementation was increasing the load of the site by a factor of 5 of this AT&T Mt Patterson communication site. The site was constructed more than 10 years prior as a solar off grid site. Upgrading the solar panels would help increase the PV gain by a factor of 4 but more power was needed. Additional real estate was not available to increase the size of the PV array, the additional power must come from a generator. The site's 10,000 foot elevation made it impossible to refuel in the winter. A solution was needed to minimize generator fuel consumption to keep the site on air.

 

The optimal number of lead acid batteries was 5 strings equalling 240 KWh of storage. At 5:00 PM each day the stored battery power would be called upon, by midnight the lead acid batteries would be drained to 50% and needing a recharge. Due to the slow charge rate of lead acid batteries (.5 C-rate), the generator would then run for another 8 hours to charge the battereis. At that rate the 6,000 gallons of fuel would be consumed in 3 months. Additionally, at this daily cycle rate, the lead acid batteries would need replacement within 3 years.

 

Supercapacitors were analyzed to determine if they would be a solution to reduce the generator runtime. Supercapacitors can be rapidly charged (1.7 C-rate), allow for a 90% Depth of Discharge (high availability of stored energy) and have a very high cycle life (over 25 years at daily cycling). Due to these advantage, fewer KWh of storage would be needed to provide the needed energy for the site, making for a much smaller footprint and reducing the generator runtime by 75% over the lead acid batteries.

The supercapacitor integration company, CIC prepared the engineering and cost benefit analysis using its proprietary energy analysis software, and provided the complete turnkey solution, engineer, furnish and installation. Monitoring and follow up have shown that the system continues to operate as designed, the site’s minimal generator runtime means that the site is fueled just one time per year. This site has been in operation cycling two times per day since October 24, 2019.

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