Off-grid Revamp

Project Profile


Solar Electric

This project spotlight strays from our usual format in several ways. First, this project exemplifies the capacity of our Service Department, an incredible asset to our operations that often goes unrecognized. Beyond performing maintenance and repairs to our existing systems (as well as those installed by other companies) our service team, under the Management of Steve Werner, provides expertise  for bringing existing systems into improved condition. This off-grid revamp is one that he and Service Technician Allen Lushbough worked with, increasing the system’s capacity by a third. Secondly, I’m taking the opportunity to address developing battery storage technologies, in which there has been so much interest lately. Thirdly, as the customer wishes to remain anonymous for privacy reasons, this will be more about the system than the customer’s story.

This off-grid solar energy system serves a hunting  cabin in a remote part of South Carolina and was installed by the building contractor about 6-7 years ago. The customer contacted us a few months ago as he was never satisfied with the amount of power available in the battery bank, and the storage capacity had been declining over the years. After consulting with the  owner about his needs and examining the current equipment, Steve presented a solution that involved increasing the pv array, replacing the battery bank, and moving the  equipment into a new shed to protect them from the elements and increase their lifespan.

The existing solar array consisted of eight ground-mounted modules. Four SolarWorld Sunmodule Plus SW 275 Watt modules were added, increasing the output from 2.2 kW to 3.3 kW.  SolarWorld modules are manufactured in America and carry a 25-year linear performance guarantee, and a 20-year product workmanship warranty. In addition, the whole array was rewired so that the existing charge controller could be used  after the expansion.  For storage, twelve new Rolls Surrette S-605 6 Volt  flooded deep cycle batteries were specified  to provide a 24V 1446 Amp-Hour battery. This should provide ample  power for the cabin’s electrical loads  for at least 5 days of cloudy weather. The batteries carry a seven year warranty, and with regular maintenance and being housed in the new shed they should last longer than the first set.  In addition to the battery bank, the shed houses the balance of system components (the inverter and charge controllers) that were relocated from simple boxes out in the yard so  they will be more easily accessible as well as more  protected.  These improvements should serve the customer  for many years, and he is pleased with the results thus far.

Battery storage with solar PV systems is a hot topic these days, thanks to a renewed interest in self-sufficiency and resiliency, as well as the publicity around the Tesla Powerwall product. Therefore, this is a good opportunity to address the developing technologies.  Sundance has been designing and installing battery-based solar PV systems for more than 20 years, so we have loads of experience to help you navigate the confusing landscape of battery storage options.

Historically, lithium-ion batteries have not been used for battery- based solar PV systems due to their high cost and questions about their life-cycle longevity when cycled deeply on a daily basis.

We are now seeing a move to market Li-ion batteries for use with solar systems, but primarily for grid- connected systems rather than off-grid systems that require daily deep cycling.  Sundance is a preferred installation contractor for Tesla car chargers as well as the Powerwall battery once it is readily available.

We are excited to compare the cost and performance of the Powerwall with our current battery options.  Currently, we recommend deep cycle  Lead Acid AGM (Absorbed Glass Mat) batteries for grid connected solar PV systems, where the battery bank is sitting on standby and not deeply cycled regularly, and for peak load shifting/shaving.  We recommend Deep Cycle Flooded Lead Acid (FLA) batteries for true off-grid systems due to their longer life cycle longevity and low cost per amp hour.  FLA batteries are less expensive than AGMs and can be used for grid connected systems if exercised regularly.

It remains to be seen how well the new generation of LI-ion batteries can compete with AGM and deep cycle FLA batteries on performance and cost.  Until LI-ion is more widely installed in real-life solar installations, we can say only that they are winning the marketing competition.  Stay posted for more updates in future newsletters.

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