| Smart Solar Energy Management Drives Solar Adoption |
 Today’s solar inverters try to optimize the entire array from a central vantage point, which severely limits their effectiveness. National’s SolarMagicTM technology is revolutionizing photovoltaic systems by distributing intelligence in solar arrays.Ralf J. Muenster, Director Renewable Energy Segment, National Semiconductor Corp. Energy constraint is a global megatrend. With increased demand and limited conventional sources, renewable energy is an increasingly critical component of our world economy. Converting solar irradiation into electricity through the use of solar photovoltaic (PV) technology is the most promising and under-represented alternative energy technology on the market. Today, solar comprises less than 0.1 percent of the total energy production worldwide. Continuing advances in PV technology make this form of renewable energy particularly well-positioned for future growth. With many new production capacities and new technologies entering the market, 2009 could become a banner year for solar. One promising new technology is a micro-optimizer technology, like National Semiconductor’s SolarMagicTM technology, which makes solar energy management smarter. Today, the typical solar photovoltaic installation consists of a number of carefully matched panels that are connected in a series of strings and put in parallel with other series strings. The DC current generated by this array subsequently feeds into an inverter on the side of the array. Inside PV panels are strings of cells, and it is not uncommon to end up with hundreds of PV cells connected in series within these arrays. Similar to Christmas lights, if one cell in this link fails to produce current, the entire string drops out. This is exactly what happens when partial shading or soiling occurs on PV installations. As a remedy, modern panels have panel-integrated bypass diodes that will attempt to re-route the current around heavily impaired sections of the strings. If active, these bypass diodes will reroute the current around big sections of string, not only losing the potential energy contribution of these cells, but worse, lowering the overall voltage of that string. Coming back to the concept of maximum operating point for the cells, the inverter will now have to decide if it should optimize the voltage for the impaired string or maximize the energy harvest from the non-impaired strings. In most cases, the inverter will choose to optimize for the non-impaired strings, causing the energy harvest of the impaired string to drop to near zero. The result is that a PV system affected by just 10 percent shade can cut its energy production in half. This phenomenon has to do with an extreme sensitivity of the solar architecture to mismatches in the PV system. Clearly, after more than 30 years, solar energy management is due for a major overhaul. We need smarter solar energy management to propel this promising form of renewable energy to its full potential. Over the past few years, researchers in National Semiconductor’s labs have been studying this problem. They realized that today’s inverters still happen to be the least reliable component in PV systems, lasting only five to ten years. Panels, on the other hand, last about 25 years. Today’s panels feature solely passive electronics because nobody had managed to integrate smart, reliable, active electronics. The main feature that needs to be distributed in PV systems is an optimization function, which can be highly integrated into a few sophisticated ICs. It turns out that National has created and delivered reliable ICs for very demanding applications for nearly 50 years. The advent of micro-optimizer technology can make solar more efficient by monitoring and maximizing the energy harvest of each individual panel and maximizing the energy flow through the array. SolarMagic technology, which leverages National’s expertise and competence in advanced algorithms combined with leading-edge mixed-signal and power management technology, allows solar installations to recoup up-to-50 percent of lost power due to shading and panel mismatches. Distributing intelligence down to the panel level, it enables each panel to operate at its maximum power point regardless of what is happening in the string. This means PV arrays can now be installed even if there is partial shading, making way for green solar energy. Essentially, new micro-optimizer technology will truly enable solar to be more pervasive and efficient in real-world conditions. www.national.com |