Solar Research Project

NPEC’s Solar Research Project

Updated September 2023

Failing equipment contributes to end of solar project

The 6.56-kilowatt solar system installed at our headquarter facility in Carrington has run into some hardware issues.  In the early months of 2022, one set of micro inverters failed on the solar system which has been impacting its overall production. 

The cooperative would normally replace the broken equipment however the original equipment manufacturer went out of business.  As of today, a direct replacement cannot be found on the open inverter market without replacing the entire panel system.  As a result, Northern Plains Electric Cooperative (NPEC) has made the decision to decommission the solar system in September 2023.

The system has experienced a continual decline in production over the past year and investing additional resources into maintaining the system would not be practical.  We were able to achieve our primary goal of sharing lessons learned from owning and operating a solar system.

The 16-panel system was jointly installed with former sister co-op, Dakota Valley Electric in 2015 as a research project to collect data to present to members as a reference when considering solar options. The co-op initially wanted to learn more about the cost to install, the cost to maintain, how reliable a system would be and what sort of return would members see on their investment.  Lessons were learned on all parts which is summarized below.

System details
The project is similar in size to a typical residential installation.  It is comprised of 16 panels, in an array of four panels wide and for panels deep.  Overall, it takes up an area of about 25 feet long x 28 feet wide.

How much electricity is generated?
Before the failed inverter in 2022, the solar system produced an average of 8,650 kilowatt-hours (KWH) per year. By using 100% of the electricity being produced, there’s an average savings of about $930 per year using our 2023 General Service Rural energy rate. Of course, the output varies from month to month with the total energy generation mostly depending on sunny days.  Decline in production has been attributed to damaged reflector panels and failure of an inverter.

In North Dakota, the winter months will see less electricity production from a solar array due to the limited hours of available sunlight and the number of overcast days we experience. In the winter season, November through April, the system produced an average of 528 kilowatt-hours per month.  By contrast, the summer months, May to October, have a greater potential for solar production with an average of 904 kilowatt-hours per month.  Total energy generated was affected by the failed equipment.

Maintenance
Over the eight years commissioned, NPEC saw minimal maintenance required on the overall system.  Basic cleaning of dust, leaves and snow as well as the resetting of the inverters when they trip.  Besides the current inverter issue, the only major maintenance took place in 2018 when high winds bent the aluminum supports, causing four reflector panels to fall and break.  The cost of materials to repair these damages was $373, plus labor to reinstall the parts.

During those times of repair and maintenance, it was noted that access to fix the inverters and panels would have been much more difficult, especially in the winter, if our system had been roof-top mounted.  NPEC was fortunate to have the space for a ground mount system, free from obstruction that would have impacted the on peak sun-hours. 
 

Return on Investment
Before the detrimental failed equipment, the cooperatives were looking at a 20-year return on their $19,000 investment, which was the net installed cost after receiving $10,000 in grants.  Any repairs to the system extend the payback period.  It is important to note that the life of inverters on any system is shorter than the solar panels themselves.  A typical life of an inverter may be 10-14 years, while the solar panels have an expectancy of 20-25 years.     

Our geographical location is our biggest downfall with it comes to solar.  Typically, in North Dakota, the break-even point financially for investing in and installing a solar array, will take 18-20 years.  This assumes you can receive the 30-33 percent tax credits or grants such as NPEC qualified for.         

Using electricity while the sun shines is a key factor if you are hoping to see a return on your solar array investment.  One needs to utilize nearly 100% of the electricity a solar array generates, otherwise there may not be a financial break-even point during the lifetime of the equipment.  “The key is to size the system for your own use, do not overbuild,” said IT manager Scott Buchholtz.

NPEC’s actual energy production was close to the estimated output for the location, which was calculated using the PVWatts Calculator before installation.  This online tool can be used by homeowners to estimate energy production of grid-connected photovoltaic (PV) energy systems throughout the world. It can be found on the official government website, pvwatts.nrel.gov.

Interested in installing your own Distributed Energy Resource (DER)?
Click here to view our updated policies, forms and procedures updated on January 1, 2023.

Questions?
Give our engineering department a call at 1-800-882-2500 or email at DER@nplains.com