Enphase is introducing its next-gen microinverter. How is this going to change the market?
The next-generation Enphase
microinverter achieves a CEC efficiency of 96 percent, a record for microinverter technology. This level of performance will be a key factor in accelerating the transition away from traditional centralized inverter technology.
In addition, the design of the next-generation microinverter allows for direct integration into solar modules, enabling a new breed of “AC Module”products. These integrated products save significant time and cost during the design and construction of a solar system. Specifically, the “AC Module”eliminates any need to install inverters, and it reduces the cost of wiring, grounding, fastening and other balance-of-system equipment.
What is the main advantage of microinverters over traditional inverter technology?
The advantages of Enphase Microinverters over traditional inverter technology can be broken down into four categories: productive, reliable, smart and safe.
Solar systems are constantly affected by varying environmental factors, such as shade, dust, debris, non-uniform temperatures, sub-optimal irradiance angles and more. In a traditional solar system, a single solar module affected by one of these issues can impact the performance of the entire system. This is commonly known as, "The Christmas Light Effect," and can cost system owners significant amounts of money.
Microinverters do not suffer the Christmas Light Effect because they perform maximum power point tracking (MPPT) and power conversion on a per-module basis. The Enphase Microinverter uses a combination of advanced semiconductors and power electronics to apply our proprietary MPPT algorithm. The efficiency of our inverters combined with our MPPT performance allows Enphase Microinverters to significantly increase lifetime energy production of the solar system.
Having per-module power conversion also addresses a common problem outside of variable environmental conditions, a problem that affects solar systems persistently over their 20-year lifetime: “module mis-match.”Every solar modules varies slightly from its nameplate power rating, due to slight differences in manufacturing conditions. This variance can be as much as +/-5%, and it can increase as modules age. In traditional solar systems, the lowest-performing module will dictate the performance for the whole system. In contrast, microinverters allow each module to be independent, rather than subjecting the entire solar system to the lower end of the variance.
Another unique benefit to the Enphase Microinverter is its performance during low-light conditions. When only a trickle of sunlight reaches a solar module, Enphase Microinverters go into what’s called “Burst Mode”where the microinverter stores up the small trickle of energy until there’s enough to send a burst of AC electricity. Even though the amount of power being produced by the module at these times is extremely low (sometimes less than a watt), burst mode is utilized quite regularly (at minimum, twice everyday during sunrise and sunset), increasing the lifetime energy production of a solar system by about 1%.
At Enphase we talk about reliability in two ways: Unit reliability and system reliability.
Microinverters’distributed power conversion means they process low amounts of power and emit small amounts of heat. As a result, microinverter electronics experience very low electrical and thermal stresses, making them inherently more reliable than traditional inverters. As a result of this, Enphase Microinverters offer a 15-year warranty, which is 50% longer than any traditional inverter.
The distributed approach of the microinverter means that you eliminate the single point of system failure. In the rare case of a microinverter failure, it would only affect a single solar module, constituting a very small percentage of the entire array. This means that inverter replacements are no longer emergency situations but can be replaced at a convenient time or during routine maintenance. The monitoring system will also alert you when there is a problem.
This distributed approach, combined with the incredible reliability of our microinverters, allows us to achieve a system availability metric of more than 99.8%, and provide an unmatched 100% uptime guarantee.
The simplicity and flexibility of a microinverter system makes the design and installation of solar systems faster and easier. Enphase Microinverters install quickly using the existing racking for the PV modules. There is no central inverter to install, and they connect to AC branch circuits, eliminating the need for string design, DC combiners, DC conduit runs and DC disconnects.
After installation, Enphase Microinverters provide per-module performance information through a web-based platform. This introduces a new level of intelligence into the monitoring and management of PV systems.. In addition, the communications and IT backbone that makes monitoring possible is also able to support other smart energy technologies. In fact, Enphase recently introduced a smart thermostat device that integrates with the Enphase Microinverter System.
Safety is the fourth and final category of the Enphase Microinverter’s advantages. Because you now have an AC-based solar system, there is no high-voltage DC wiring on your rooftop. This dramatically reduces the risks of shock and fire.
Is there an optimum project size where the use of microinverters makes the most sense or is there no upper or lower limit to the size of installation?
In an AC-based system each module is utility-interactive and shuts down if there’s a fault or a disconnection in the wiring. In contrast, DC wiring in solar systems is live as long as the sun is shining, and as a result, a faults or disconnections can create continuous arc faults, like an arc welder. These arcs can be more than 6000 degrees and pose fire and injury risks. In fact, the 2011 NEC mandates that DC-based solar systems have arc fault detection and interruption devices to prevent these dangers.
Microinverters deliver significant value to both residential and commercial installations. We already have installations up to 350kW, and we are working with partners on systems over 500kW. We plan to continue pushing into larger and larger projects, and we will be developing additional products to better serve these markets.
Where do you see the inverter market in the next five years?
The inverter industry is growing and evolving quickly. We introduced our first generation microinverter in 2008, and since then, we’ve introduced two new generations and shipped more than 400,000 microinverters. This rate of innovation and growth is havinga significant impact on the global inverter industry. Considering all that we’ve achieved in just two years, it’s almost crazy to predict where things will be five years from now.
Do you sell your products to individual installers or is the main focus to have manufactures build them into their panel design?
Today, we primarily sell our products through distributors and wholesalers, and we work closely to train and educate installers on how to use our systems.
Our AC Module technology uses a special junction box that allows easy connection, either at the factory or anywhere in the value chain. We are not dictating where the microinverter gets installed; instead we are focused on making it easy to install, wherever that happens.
What are the biggest challenges to the solar market? How will Enphase overcome these obstacles better than its competition?
The most important factor in the solar market is ensuring stable demand. In the past, the market was regularly destabilized by shifting policies and incentives. This can kill any industry, but especially a budding industry that’s competing against the well-established fossil fuels industry, which has been developing and benefiting from policies for more than a hundred years. As long as we can create a stable and level playing field with the incumbent energy technologies, renewable solutions, and solar in particular, will continue to thrive.
How is Enphase helping solar adoption become more mainstream and what difference can the company make?
The Enphase Microinverter System is driving down the cost and eliminating many of the technical hurdles traditionally associated with solar technology. In addition, it makes solar systems more intelligent, more connected
and more feature-rich than every before. As we continue down this path, solar technology will continue becoming more practical and more desirable for the mainstream.
Raghu Belur - Co-founder, Vice President of Products
Raghu Belur has 15 years of experience in engineering and engineering management. He started his career at the Indian Institute of Science where he worked on a team developing an alternative energy gasification system. He was an early engineer at Cerent where he was responsible for the development of the optical 2.5Gig interface for the Cerent-454 ADM. Cerent was subsequently acquired by Cisco for $7 Billion. At Cisco, Raghu was managing the team developing the 10Gig interface products for the ONS-15454. He co-founded Enphase Energy Inc. with Mr. Fornage in March of 2006. Raghu has a MSEE from Texas A&M University.