POWER OPTIMIZER: Smart Module Technology

Solar power technology isn’t a new discovery; in fact, it was discovered way back in 1800 when Alexandre-Edmond Becquerel—a nineteen-year old French scientist—was experimenting with an electrolytic cell composed of two metal electrodes. He was surprised as he discovered that the materials would emit energy when exposed to light. That was when PV effect came to light. Likewise, relatively new to the solar marketplace is a new type of technology that helps boost efficiency and hence the output of solar PV systems. When deciding on solar equipment it’s important to know what options are available? Different equipment suits different situations better. Solar modules in an array are connected in a series, like batteries. The array is producing optimally when all modules are performing the same. But what happens when temperature changes, or fall leaves, winter snow or shade covers part of a module, causing it to underperform? The module not only outputs less energy, it can also heat up and drag down the performance of the other modules by constricting the flow of energy through the array. This can cause the array to lose power. However, this is where power optimizers can help. Power optimizers are DC/DC converters attached at the module level. Installers can connect optimizers on-site, or manufacturers can connect them to the module in the factory, replacing the traditional junction box. Power optimizers can correct for module “mismatch” by allowing each module to function at its maximum power point tracking (MPPT) and then converting the energy to the optimal voltage and current for the array. This enables the entire array to harvest more energy. Power optimizer is ideal for situations where shading is prevalent or when your solar system falls on multiple roof surfaces with different orientations. Let’s dive into the details!

A power optimizer is a combination of both a string and micro-inverter. It is a Module-Level Power Electronic (MLPE) device that increases the solar panel system’s energy output by constantly measuring the Maximum Power Point Tracking (MPPT) of each individual solar panel and adjusts DC characteristics to maximize energy output. The panel optimizers relay performance characteristics via a monitoring system to facilitate operations and any necessary solar panel maintenance.

Photovoltaic modules are capable of generating power in direct relation to how much sun hits them. It means that the energy generated from modules also fluctuates depending on how much sun is striking the solar panels. This puts additional stress on the wiring and the system inverter, which converts the DC power produced by a module to more readily usable AC power, the type of power used in most household appliances. While micro-inverters exist to convert the DC power from a PV module to AC power at the module level, the technology is usually a little more expensive than using a string inverter where 10s to 100s of PV modules are stringed or tied together to one inverter where MPPT is applied. But when that’s done, the inverter can’t maximize the power from each module and its output is diminished by the lowest performing modules on a string.

That’s where the power optimizer comes into the scene. The power optimizer is designed as a less expensive cousin than a micro-inverter. Like micro-inverter, a power optimizer can replace a module’s junction box, where it wires to other PV modules or the inverter, or it can be added on as an aftermarket piece of the system. The power optimizer can be added to each module in an array, or depending on the type of power optimizer, can be wired to a number of modules in an array to optimize the power from each of them. In arrangement Over the past several years, DC optimizers a series of power optimizers will feed electricity to the array’s inverter or inverters depending on the system’s size. The inverter then converts the power to AC electricity for use in the home, bussiness or before sending the power on the grid.

Over the past several years, DC optimizers have become an important technological ingredient in many residential, commercial and utility-scale solar designs. By utilizing modules integrated with this technology, system designers can reduce the power loss from shade obstructions, thus safeguarding systems against long-term module mismatch caused by uneven soiling or debris. Many PV module OEMs are now incorporating the next generation of DC performance optimization: a highly integrated power regulator included on each cell-string within the solar module.

Technology and Innovations

Power optimizers offer many of the advantages of micro-inverters, including MPPT and monitoring at the module level, without DC-AC conversion. Additionally, some power harvesting systems offer for parallel DC architecture, which allows PV modules to be wired in parallel instead of series. Similar to micro-inverters, this helps to reduce problems due to shading, module mismatch, and other issues. Like micro-inverters, power optimizers are located at each panel, usually integrated into the panels themselves. However, instead of converting the DC electricity to AC electricity at the panel site, they “condition” the DC electricity and send it to a string inverter. This approach results in higher system efficiency than a string inverter alone. Similar to micro-inverters, power optimizers reduce the impact of panel shading on system performance, and also offer panel performance monitoring. Systems that use optimizers are typically more affordable than those that use micro-inverters.

Power optimizers can also be used in a fi xed-voltage mode where the inverter determines current draw based on a predefined voltage target. The optimizers will all lock in on the same current value and deliver the remainder of the power as voltage. This advanced mode of operation means that string length is no longer determined by voltage but is now determined by power. The benefit is string lengths that are boosted by 60% in residential systems and by over 4-times in commercial systems. An added benefit is that inverter manufacturers can design inverters to accept voltages at the optimal level for DC to AC conversion reducing the need for DC boosters and other internal components. These reduced parts lead to lower cost products.

Benefits and Competitiveness

Over the past 20 years, many researchers, engineers and scientists have developed a variety of MLPEs to improve the efficiency of solar module energy output. A growing number of module manufacturers have begun to include first-generation DC optimizers from various system integration manufacturers. This new solution brings more production upside while also addressing the limitations of first generation solutions. Modules with power optimizers tend to be more efficient than not available in other types of PV modules. The most important factors in any PV project are Performance, Predictability, and Profitability; of course there are the significant environmental benefits, but costs and efficiency drive a homeowner’s or business’ decision whether to install a solar system or not. For most projects, using either micro-inverters or power optimizers greatly improves a project’s Levelized Cost of Energy. Both microinverters and power optimizers improve a module’s, and an array’s, performance because they allow module mismatch, track MPPT of each module, and improve the monitoring and tracking of the system. However, for some solar power plants, power optimizers can be a better alternative for three reasons:

• Power Optimizers harvest more energy than micro-inverters. The efficiency of Power Optimizers and central inverters are higher than micro inverters. Power Optimizers derate the module less than micro-inverters because they are smaller and generate less heat. They also have wider operating ranges and higher DC inputs than a micro-inverter.

• Power Optimizers add an additional safety feature and help comply with electrical code. In case of AC loss, power optimizers can reduce the system’s voltage to less than 70 less than 10 seconds.

• Power Optimizers offer more design options. On single-phase systems for various micro inverters the maximum string length is 17 while Power Optimizers allow 25 modules. Power Optimizers are also more scalable because the only additional cost is the optimizer while micro inverters have EBOM and the micro-inverter. Benefits of Power Optimizer over Micro-inverters

• Greater module compatibility and no power clipping

• Higher energy yield through wider MPPT range

• Higher reliability

• Higher efficiency

• Superior communication technology (DC Power Line Comm.)

• Compliance with advanced grid codes

• Lower system cost, faster ROI

• System Scalability

During the long-term operation of a solar power plant, the modules will suffer aging, cell microcracks, potential induced degradation (PID) and so on, which will cause power loss. A module-level optimizer can prevent an underperforming module from harming overall system performance, and yield high efficiency and reliability; which in turn is of course a far more finely-tuned solution than other technologies. As the National Electric Code (NEC) surrounding solar electrical installation undergoes new iterations, MLPE such as power optimizers will play an important role in making solar installations safer to work around and easier to service.

Market Insights

The module-level power electronics (MLPE) market is one of the fastest growing segments in the PV industry, rapidly moving beyond niche status to become a crucial component of residential and commercial installations. The MLPE market includes both micro inverter technologies as well as DC power optimizer technologies. Rising adoption of photovoltaic systems in commercial and residential sectors will propel the market expansion for power optimizer market in solar sector. In addition, high demand for upgraded power harvesting systems embedded with features such as panel monitoring for independent power generation will catalyze industry growth. Prominent companies, increasingly investing in R&D for unique product development will also catalyze the market share. According to Global Market Insights, “Power Optimizer and Solar Micro-inverter Industry is forecast to hit USD 1.4 billion by 2024, increasing at a CAGR of 10% over 2016-2024.”

Technology innovation pertaining to power harvesting systems coupled with decreasing component prices will drive the power optimizer and solar micro-inverter market. Companies such as SolarEdge, SolarBridge and Tigo are working towards the development of integrated smart module technologies to enhance the efficiency of PV architecture and thereby positively impacting overall return on investments of the end consumer. On-grid power optimizer and solar microinverter market is predicted to witness a substantial growth of over 15%. Initiatives including feed in tariff schemes introduced by regulators will positively influence the industry landscape. Commercial applications will exceed USD 300 million by 2024. Growing deployment of rooftop PV systems in commercial complexes including malls, and SEZs will positively impact business growth.

U.S. market share is predicted to grow over 15% from 2016 to 2024. Government programs to augment the installation PV systems across residential and commercial building will complement the industry outlook. For Europe and Germany, the market size for 2015 was valued over USD 30 million. Directive 2009/28/EC has been introduced to promote and produce energy from renewable resources. It sets a target to fulfill 27% of its energy needs through renewable resources by 2030.

China is predicted to exceed 1.4 GW by 2024. In June 2016, China introduced a plan to implement PV poverty alleviation program for the next four years to increase the income of poor households through the installation of solar systems. The National Energy Agency is also framing policies pertaining to the deployment of distributed PV technology across remote off-grid areas.

India power optimizer and solar microinverter market is expected to witness a significant growth of over 20% in terms of volume. Indian Renewable Energy Development Agency Ltd. (IREDA) through National Bank for Agriculture and Rural Development (NABARD) has implemented a subsidy scheme under which 40% subsidy on capital cost has been provided towards the deployment of PV systems in rural and urban areas. South Africa solar microinverter and power optimizer market share is expected to witness significant growth of over 10% during the forecast period. Government favorable initiatives towards the development of distributed generation systems will positively influence the industry landscape.

With the benefits of enhanced design flexibility, convenient installation procedure, and module level monitoring, both power optimizer and solar micro-inverter systems find widespread applications in the residential, utility, and commercial sectors, which will catapult solar MLPE market. Also, features such as upgraded safety and high energy yield will boost solar power optimizer and microinverter industry in commercial applications, which contributed to more than 15% of the overall share in 2015. Government initiatives such as tax rebate, investment tax credit, net metering and FIT to increase the number of PV system installations across commercial buildings.

Three phase solar microinverters and power optimizers help enhance the system downtime, in addition to possessing features such as upgraded conversion efficiency coupled with high circuit density in comparison with their counterparts. High demand for uninterrupted power supply will fuel solar microinverter and power optimizer market in the utility sector in the years to come. Compact size and design flexibility are two major characteristics of standalone connectivity that help eliminate the requirement for an electrolyte capacitor, fan, and a large transformer. Driven by these convenient features, standalone solar microinverter and power optimizer market is slated to grow at a CAGR of more than 10% over 2016-2024.

Owing to the rising adoption of rooftop solar PV systems, solar microinverter and power optimizer industry in residential applications is slated to witness healthy gains over 2016-2024, having recorded a revenue of more than USD 440 million in 2015. Government encouragement toward the utilization of solar rooftop systems in residential applications will subsequently stimulate on-grid solar microinverter and power optimizer market, which was worth more than USD 120 million in 2015. Favorable initiatives such as tax rebate, low interest rate loans, feed in tariff, subsidies, and other financial benefits will also drive on-grid solar micro inverter and power optimizer industry growth over 2016-2024. With the PV market experiencing significant growth across the world, new technologies are continuously being developed to increase system performance and return on investment (ROI) for project owners. One of the most rapidly expanding segments in the industry, the module-level power electronics (MLPE) sector is at the forefront of this innovation, providing essential components for residential and commercial installations. Analyst reports estimate that MLPE solutions are already featured in about two out of three residential systems in the US and are expected to reach 5GW installed globally by 2017. The module level power electronics (MLPE) market is one of the fastest growing segments in the PV industry, rapidly moving beyond niche status to become a crucial component of residential and commercial installations. The fastest-growing technology solution within the MLPE market is the DC power optimizer. Unlike traditional inverters which track maximum power point (MPP) at the string level, power optimizers track the MPP at the module level, effectively mitigating mismatch effects and allowing each module to operate to the best of its ability. Power optimizers can be added to new installations, retrofitted to existing installations, or embedded directly into PV modules during the manufacturing process. Forward-thinking PV module OEMs are now incorporating the next generation of DC performance optimization: a highlyintegrated power regulator included on each cell-string within the solar module. This new solution brings more production upside while also addressing the limitations of first-generation solutions. Widespread adoption of this technology is expected in geographies and solar market segments that have never before considered DC optimizers.

Within the MLPE space, power optimizers are showing the largest percentage increase in customer acceptance. Whereas micro inverter technologies replicate the inverter completely at the module level, power optimizers only deploy a minimal amount of electronics on the rooftop to handle the MPP tracking and DC to DC conversion, leveraging a centrally located inverter at the end of the string. The benefit of this approach is that installers can reduce the hardware on the rooftop improving reliability and slashing costs. Rising installations of rooftop solar in AsiaPacific, especially in China and India, will see the market moving towards Asia-Pacific from North America. The reduced MLPE costs will lead to a higher adoption in many developed and developing nations. The increased R&D investments and development of innovative products are also the key strategies that have helped to expand the market for power optimizers. It is expected that the prices of MLPEs are expected to be on par in the near future with traditional inverters, leading to higher adoption by consumers. Moreover, competition from other technologies, increased usage of other sources of power, lack of protocol standards, and regulations and tariffs are key factors that are hindering growth in the market.

Moreover, public awareness regarding the advantages of renewable energy sources over conventional energy sources will eventually lead to increased product demand, positively influencing solar microinverter and power optimizer industry. The value proposition for power optimizers is compelling, and the market will only grow as providers enhance their performance capabilities and cost structures at the residential, commercial and utility scales. Look for this technology to be a standard component of PV systems of all shapes in sizes in the not-so-distant future. But even while analysts forecasts that global shipments of modules with DC optimizers will grow, broader adoption of these devices will continue to be limited by cost and installation complexity.

According to a report from Frost & Sullivan, with movement towards renewable power and distributed power sources, the MLPE (read: Power optimizers) market is expected to sustain further significant growth in all regions of the globe. To gain a competitive advantage and increase market share in a highly consolidated and fiercely competitive market, MLPE companies must innovate their products to reduce prices, seek geographic expansion, and invest in partnerships or merger and acquisition strategies.