DC optimizers have emerged on the market as an alternative for module level power management and monitoring over microinverters, combining the benefits of module level MPPT of microinverters with the higher operating efficiencies of string inverters. Manufacturer’s claims of 25% increased production with use of DC optimizers hasn’t been sufficiently corroborated with third party field testing which begs the million dollar question: will DC optimizers live up to the hype and become the next evolution in PV system design?
Benefits of DC Optimizers
DC optimizers allow each module to independently operate a maximum power point tracking algorithm, ensuring that each module is producing the greatest amount of energy possible while getting the benefit of the higher DC voltages of string inverters and subsequent higher efficiencies. This arrangement has numerous benefits including mitigating the impacts of module shading, module mismatching, and over or under performing modules. This allows unprecedented versatility in the system design including multiple module types, azimuths and tilts connected to a common string inverter. Some DC optimizers also offer a safety shutdown which interrupts DC current at the optimizer mounted behind the panel resulting no hot DC conduits in the event of an emergency. DC optimizers give you better resolution of monitoring than is possible with string level monitoring and provides the added benefit of increased production.
Applications for DC Optimizers
Perhaps the most exciting aspect of DC Optimizers is their compatibility; they can be used cost effectively in grid-tied and off-grid applications from residential to commercial scale, they’re compatible with 60-cell, 72-cell, 96-cell and thin-film modules – a hurdle that most microinverters have yet to overcome. Additionally, the cost of DC Optimizers is reduced with increased scale making it particularly appealing for larger and commercial arrays, unlike microinverters whose cost is linear in terms of installed cost in $/Wp. Microinverters often require expensive AC trunk cable from the manufacturer and have fixed costs for the components which don’t experience the same economies of scale as large string inverters.
Module level monitoring and levelized cost of energy (LCOE)
When evaluating PV system cost, it has become standard industry nomenclature to evaluate various products and components in terms of $/Wp but this metric does not consider the single most important aspect of the PV system; total lifetime production. In response to this many owners, integrators and financiers are beginning to consider both $/W and Levelized Cost of Energy (LCOE) which is defined as Total Life Cycle Cost over Total Lifetime Energy Production) when making design considerations.
LCOE is a more useful but often nebulous number to determine and requires modeling and analysis that are outside of many installers’ skill sets and available time. If you don’t want to spend time analyzing the time value of money and estimating operation and maintenance expenses over the 25 years, your next best option is to design your PV system to be as versatile, resilient and with the highest resolution of monitoring possible. I often think of the mantra “You can’t manage what you don’t monitor” when designing a system and the greater resolution of data you have, the faster and easier it will be to trouble shoot and repair the system over its lifetime. Similarly, it is incredibly difficult to detect a single point source of failure in a system if you only have array level monitoring; what’s the value of a system that was the lowest $/watt installed but you can’t determine underperformance during 25 year life? With the resolution of monitoring and versatility module MPPT offered by DC optimizers, it is estimated that LCOE can be reduced by 20% or more.
Available DC Optimizers
Californian based Tigo Energy has emerged as the frontrunner in the budding DC Optimizer industry and has had their MM-ES Maximizer( (link to Alt-E Page) lab tested by Photon Magazine and found that Tigo Energy “significantly outperformed all competition”:
Perhaps most visible are the recent breakthroughs in BOS electronics which bring DC power maximization, safety features and advanced system management to the PV project. In the recently completed lab tests by Photon, the journal examined the benefits of five commercially available solutions. The results found Tigo Energy demonstrating clear advantages in energy production and highlighted the unmatched over-all value of the complete Maximizer solution. Tigo Energy departed from the conventional approach of DC/DC voltage conversion to develop a patented Impedance Matching technology. This superior energy harvest can be attributed to the 99.6% statistical efficiency and unmatched distributed MPP control accuracy of the Impedance Matching approach. Tigo Energy generated 3.5 times more power production from unshaded arrays than other tested solutions. These test results solidify Tigo Energy’s position as the clear market leader in DC maximizers and help to explain the rapid worldwide market adoption of the platform.
You can check out the Entire Photon Article Here:
Solaredge also has a DC optimizer product, but it is only able to integrate to Solaredge’s inverters (http://www.solaredge.us/files/pdfs/se_system_overview_na.pdf). Silicon Valley start up eIQ is also offering a DC optimizer as is Oregon based Azuray Technologies. SMA and PowerOne have recently entered the microinverter market and PowerOne now offers a DC optimizers as well.
For more information on DC optimizers check out these resources:
- Cost-Benefit of Microinverters vs. Maximizers, by Andrew Wilkins, Renewable Energy World
- PV Micro Inverters and Optimizers: Not Just for Lazy Designers, by Joseph McCabe, PE, Alt Energy Stocks