ReVision Energy has been installing solar electric (also, photovoltaic, or PV) arrays in Maine, New Hampshire, and Massachusetts since the early days of the industry, when collector sizes were very modest and systems were truly only suited for remote locations where grid connections were not possible.  We’ve witnessed the introduction of grid-connected solar electric systems, which started a revolution in the industry, accompanied with a stunning drop in the cost of solar panels which has accelerated its growth by leaps and bounds.

While grid-tied solar technology continues to improve by iterations, the core components have not changed much, and, while the finer points are quite detailed, the basic concept is simple.  Grid-tied solar arrays need solar modules and one or more inverters.

Solar Modules

Solar modules come in all sorts of aesthetics as well as performance choices, such as these all black collectors installed on a home in Candia, New Hampshire

Nearly all solar electric modules sold in the United States are crystalline silicon modules (cSi), a form of modules that consist of rigid silicon wafers (which may be ‘poly’ or ‘mono’ crystalline – referring to the process by which they are manufactured and grade of silicon from which they are cut) housed in a weatherproof enclosure (tempered glass and aluminum).  All electronics are soldered to a backing board and positive and negative electrical outputs allow the module to be connected to others in a string.  This is the same basic design of solar collector that has been used since the 1970s.

We frequently hear about upcoming future generations of PV (everything from thin film to building integrated PV) however we strongly feel that cSi modules remain the right choice for the New England market.  Solar modules need to endure decades of abuse from wind, snow, and hail, and we know that cSi modules can do that.  With over 100,000 modules in the field, we can say that roof leaks and module failures are nearly unheard of.

Lest you think that a 30+ year old technology is stale and dusty, recall that loudspeaker technology is essentially the same as it’s been since the 1920s!

The advancements in cSi technology have mainly concerned reducing the cost of production of these modules and improvements in performance.  For example, in 2009 a typical 3′ x 5′ collector would be rated to produce around 230 watts of electricity.  These days, the same footprint may produce 260 watts or even 305 watts!

There are a variety of choices in solar modules today.  Nearly all reputable manufacturers will offer a 25-year power production warranty (guaranteeing output of 80% over 25 years, though people have found collectors from the 1970s that still produce 100% of their rated power today).  The better manufacturers will also offer at least a 10-year aesthetic warranty, which covers defects in the look of the collector that do not affect performance.

Our team that procures modules have over 50 years combined experience in the solar energy industry and scrutinizes manufacturers and their products over a wide range of factors including: performance, build quality of the product, aesthetics, capitalization of the manufacturer (i.e. will they be around 20 years from now to honor a warranty should it be required), product availability, and price.  We make large product acquisitions with our partners in the Amicus Solar Cooperative when possible such that we can pass through volume savings onto you.

Know that any proposal received from ReVision Energy includes modules that any member of our company would be proud to install on their own roof.

Solar Inverter

This elaborate home solar installation has both an SMA SunnyBoy inverter (gray box) as well as the add-on Sunny Island (yellow box) which creates a ‘micro-grid’ in the home, allowing a home to fail-over to a battery bank and operate without grid availability.

Other than modules, the other major component of a solar electric installation is the solar inverter(s), a piece of electrical equipment that generates grid-compliant alternating current (AC) electricity from the direct current (DC) electricity produced by the solar panels.  It is responsible for allowing the electricity from the solar modules to flow and ensuring that power is clean (from an electrical perspective) and able to interact with the grid.

Modern grid-integrated inverters feature a suite of performance-enhancing, safety, and reliability features.  For example, the modern range of SMA inverters features dual multi-point power tracking (MPPT), a transformer-less design, and optimizations that make them much more shade-tolerant than predecessors (obviating the need for micro-inverters in a number of situations).

New fire codes are requiring increasing module-level controls, and in those situations our preferred solution is generally is the SolarEdge inverter system with DC Optimizers on each inverter.  This system claims nominally better solar harvest (because of the optimization on the module level) though for simplicity’s sake and reliability we tend to prefer single string inverter installations when feasible.  Micro-inverters and other module-level electronics have become very trendy, but we have experienced much higher failure rates with this new equipment (which also costs more) than the rugged, reliable string inverters from manufacturers like SMA.

A more in-depth discussion of ReVision’s experience with microinverters is contained in our comments in the July, 2015 edition of Solar Pro magazine.

Data Monitoring

SMA Webbox Data Monitoring Dashboard

Dashboard for a live PV installation (at our office in Portland, ME)

Solar PV is an extremely reliable technology, but truth is, it’s also really fun to see what’s happening during a sunny day and to track a system’s progress against its modeled performance. While all inverters feature some sort of read-out on a their display, most systems offer web-based data monitoring either for free out of the box or for a nominal add-on fee.  An internet router at your home with ability to add a wired connection is required.

The data monitoring package looks a bit different for each manufacturer, but general features include daily and historical tracking of array performance, cumulative stats, a website and often also a mobile application.