ENGLISH MICROINVERTER ANALYSIS Tigo Energy Inc. 420 Blossom Hill Road Los Gatos, CA 95032
DO I WANT TO DESIGN WITH A MICROINVERTER? When considering a balance-of-system (BOS) architecture for a PV project, there are many good reasons to specify a Microinverter. When many designers, installers and system owners say, I want a Microinverter, they really mean, I want the attractive features that Microinverters offer : 1. Ease of Design 2. Shade tolerance from MPPT on each panel 3. Rooftop safety with no high voltage when the inverters are off 4. Panel-level monitoring Conventional thinking is that to get these features, the project must suffer from the additional costs, reliability issues of having inverters on the roof, and lower conversion efficiencies associated with Microinverters. But no longer Tigo Energy is the path to gaining all the value of a Microinverter without the downsides. A Microinverter design takes all the functionality and components of a string/central inverter and puts it on EVERY module. As simply a small capacity inverter, a microinverter faces the downsides of full distribution. Tigo Energy takes a very different approach to solving the same issues by putting the least amount of electronics at the panel. This semi-distributed approach puts only critical sensing, communications, and power control at the module, but leaves MPP calculation and inversion centralized. The central functions can be placed in a climate-controlled location that can be easily accessed for maintenance if needed. Figure 1 - size and component count of leading microinverter vs. Tigo Energy module electronics 2
TIGO ENERGY DELIVERS 1. Ease of Design Tigo Energy s local MPP control allows system designers to configure strings from 5 to 20 modules without additional conversion losses. A 4kW system can be configured in a single string, eliminating the need for complex sizing and placement decisions. The localized MPP control enables modules to be placed in multiple orientations in the same string East, West and South facing roof surfaces can be fully utilized. Wiring is done with simple DC leads not with complex, rigid and proprietary parallel bus cables, drops and whips. Tigo Energy Maximizers are attached directly onto the module frame, eliminating the need for special mounting hardware, additional grounding, or rooftop labor. System designers can address any size system, any modules, in any worldwide geographic location by selecting an inverter that fits the project needs the best. The Tigo Energy solution will be compatible with any inversion solution both on & off grid. 2. Shade tolerance and more Tigo Energy s unique technology provides module-level MPP control without adding a power stage, enabling DC conversion efficiencies exceeding 99.5%. This means when used with the industry s leading inverters, total system DC-AC conversion efficiency can exceed 97.5%. System owners can achieve shade tolerance equal to that of a microinverter while enjoying 2-4% more energy than the leading microinverter due to a more efficient DC/AC conversion. Even in un-shaded conditions, Tigo Energy can achieve 3-4% performance gain by correcting for small variances in module strength, dust or temperature. 1 Figure 2 - Tigo Energy system performance (yellow) compared to that of leading microinverter in independent testing (by month) 1 Photon Labs testing 3
3. Rooftop safety The Tigo Energy PV Safe feature ensures that the modules are not contributing voltage to the DC wiring when the AC main is disconnected. The Tigo Energy system owner is able to actively enable PV Safe with a disconnect button and eliminate high voltage DC from the rooftop at anytime. A microinverter, on the other hand, is required to eliminate high voltage AC. The Tigo Energy system can also detect arc conditions and turn off modules or strings to eliminate the risk of arc fire. 4. Module level monitoring plus advanced system management Like a microinverter system, the Tigo Energy Maximizers can report the performance of an individual module. But Tigo Energy provides functionality well beyond simple inverter-direct monitoring. As Tigo Energy samples each panel in the array simultaneously each second, advanced analytics can be automated in the datacenter. Tigo Energy actively provides complex system analysis, debug tools, and alerts which can pinpoint costly problems while filtering out normal environmental effects (clouds, birds, shade, etc.). The Tigo Energy software tools can offer significant cost reductions in commissioning, operations and maintenance of a PV project. WITHOUT THE DOWNSIDES 1. Cost Effective for Systems of All Sizes Tigo Energy puts minimal electronics at the module, ensuring a low cost and simple architecture. The central functions (such as MPP calculation and inversion) take advantage of traditional cost structures of scale providing a cost-effective solution for both large and small installations. Microinverters have a fixed cost per watt (the same at 10 modules or 1000 modules), limiting cost-effective deployment to very small residential systems. The Tigo Energy solution enables the use of transformer-less string/central inverters and considerable elimination of other BOS costs (string wiring, fuses, combiner boxes, data loggers, etc) so that a commercial system that includes Tigo Energy is similar in cost to a traditional implementation. Scale Economies for Inverters 1.2 1 Microinverter Inverter Price (US$/watt) 0.8 0.6 0.4 0.2 String Inverter Central Inverter with Tigo Energy Central Inverter 0 0 200 2000 20000 200000 2000000 Inverter Size (AC watts, log scale) 4 Figure 3 - cost scaling comparison - Tigo Energy vs. Microinverter
2. High Reliability The space behind the module in any given solar installation is the harshest environment. Heat is trapped between the module and the rooftop resulting in an unfriendly condition for any electronics. Tigo Energy uses the fewest components at the module, contributing to higher reliability by design. But more importantly, the Tigo Energy circuit is so efficient that there is no heat being created to stress the module or the Tigo Energy components. In contrast, a 94% efficiency microinverter must dissipate 12W of heat (assuming a 200W module) into the module that is above it. This further reduces the performance and longevity of the module and microinverter components, especially during the summer in warmer climates. The microinverter is simply a small inverter. While it has all the same components as a central inverter, they are housed in a smaller enclosure and placed in an environment that is much more hostile (under the module) than where a central inverter is kept. There is nothing about the small inverter that is inherently more reliable - but it suffers from being trapped between the roof and the module. Figure 4 - Thermal image of microinverter indicating heating of PV cells 3. Highest System Efficiencies As microinverters convert DC to AC for each module, there is a typical voltage conversion from ~ 30V DC (module Vmp) to 240V AC. This represents a large boost multiple that inherently results in low conversion efficiencies. Best in class microinverters boast efficiencies of 95-96% while most are at 92-94%. Conversely, transformer-less string/central inverters (standard in Europe, increasing availability in US) can perform at 97.5% and above due to conversion at high voltages. The Tigo Energy solution compliments the industry s best inverter technologies, providing extremely efficient (99.6%) DC optimization. 5
CONCLUSION: Tigo Energy provides a BETTER PATH to Microinverter features for systems of all sizes. For more information on installation of a trial system contact Tigo Energy or your solar distribution partner. Tigo Energy, Inc. P: +1.408.402.0802 F: +1.408.358.6279 tigoenergy.com Headquarters: 420 Blossom Hill Road Los Gatos, California U.S.A. Offices: Frankfurt, Germany contact.europe@tigoenergy.com Genova, Italy contact.italy@tigoenergy.com Paris, France contact.france@tigoenergy.com Shanghai, China contact.china@tigoenergy.com Tel Aviv, Israel contact.israel@tigoenergy.com Tokyo, Japan contact.japan@tigoenergy.com Seoul, South Korea contact.korea@tigoenergy.com 6 Printed on recycled paper Micro_ENG_04.12.2012