Back to the Basics: AC Modules and DC Modules

AC Modules

One of the newest technologies on the solar market are AC modules (or AC panels).  These are solar modules with microinverters already mounted on the back. Although they cost more, AC modules can be a great solar option for sites with shading and/or irregularly shaped roofs.

Here’s how it works: Standard DC modules are connected in series to make one or more strings that feed into one or more inverters.  Shading on one panel can affect the production of other unshaded panels in the same string.  With AC modules, however, an inverter is mounted on each module, so shading on one module will not affect the output of other unshaded modules.  For example, a tree might create shade on a single panel, and typically that obstruction would affect the output of the entire series-string of panels. With AC modules, the shade would reduce solar output for only the shaded panel(s).

Since AC modules are not constrained to stringing requirements, they can be added in any number to improve aesthetics and fully utilize roof space.

AC panels use what is called Maximum Power Point Tracking (MPPT) on a panel level, whereas string inverters use MPPT at the string level. Panel level MPPT extracts the maximum power from each module in the array and provides energy production insight that was once previously unavailable. Online monitoring with AC modules allows us to monitor the output production of each panel.

Sharp and SunPower AC modules come with 25 year warranties, versus the typical 10 year warranty for string inverters.  Other advantages include a reduction of hardware and installation time. One drawback is that there are more units to fail.  The part is warrantied, but the service would be an additional cost to the system owner.

“AC modules make a lot of sense in some situations,” says solar sales consultant JP Plumlee.  “It’s an advanced technology that is made for roofs with less than ideal solar conditions.”

LightWave Solar currently has three customers who have chosen to use AC panels, and their installations are underway.

LightWave Solar Completes 1 MW Solar Tracking Array in Memphis

System is the largest single-axis tracking array in Tennessee, and boosts local economy 
April 23, 2012

Memphis, Tenn. The largest area installer of solar PV systems in Tennessee, LightWave Solar, recently completed the installation of 998.4 kW at Agricenter International in Memphis, Tennessee.  Project completion was celebrated at a Green Ribbon Cutting Ceremony following the 2012 Tennessee Valley Solar Solutions Conference in Memphis on April 11.  Notable participants included U.S. Rep. Steve Cohen, Memphis Mayors Wharton and Luttrell, and project partners Silicon Ranch, LightWave Solar, and Sharp.

“The 1MW solar farm at Agricenter is a great example of the growth of Tennessee’s Solar Value Chain,” said Steve Johnson, President of LightWave Solar.  “We’re a Tennessee company, we hired other Tennessee companies to help build the project, and we utilized solar technology manufactured right here in the state.  This project is great for our economy.”

Residing on five acres, the system incorporates 4,160 Sharp 240-watt solar panels that were locally-manufactured in Memphis.  The panels are mounted on Array Technologies DuraTrack single-axis tracking platform, and follow the movement of the sun to increases solar electric production by 20%.  The largest single-axis tracking system in Tennessee, it will produce over 1,600,000 kilowatt-hours per year which is enough electricity to power at least 100 homes.  Over the next 25 years, the system will offset carbon dioxide (CO2), nitrous oxide (NOX), and sulfur dioxide (SO2) emissions that are equivalent to planting 6,600 acres of trees.

LightWave Solar began project construction on December 14, 2011.  On April 2, 2012, the system was commissioned and grid-interconnected by Memphis Light, Gas and Water (MLGW) and Tennessee Valley Authority (TVA).  Other system components include a PV Powered MV-1040kW inverter and SPX Arguson Solar Power Monitoring.  Silicon Ranch provided the funding for the project and owns and maintains the system.

To learn more about this project, contact LightWave Solar at 615-641-4050 and Monitoring data and time lapse video are located here: