SolarEdge, Now in Mega-Size

Transcription

1 SolarEdge, Now in Mega-Size Region Solar Installed a 1 MW ground mount array in Monticello, Florida using 45 SE20k inverters, over 1,600 P700 power optimizers and more than 3,200 Lightway 72-cell solar modules. With SolarEdge, you have just two strings per inverter, and BAM! you re done! There is a simple elegance to being able to do that. Brad Carlson, Sol Integrators At the beginning of the U.S. PV solar ramp, the industry focused mainly on the Day-1 costs of building the solar array. Today, as we see more systems reach Day 1,000, the focus has shifted. Owners now realize that PV assets can be profit-generating machines when properly designed, operated and maintained. To generate more revenue, owners must place greater focus on risk management. Moving away from the lowest cost wins idea and focusing instead on highest power production wins is driving the industry to capitalize on distributed generation and optimized inverters. And when it comes to optimization of plant production, there is no better choice than SolarEdge.

2 SolarEdge Optimized Inverters SolarEdge s module-level power electronics solution consists of three parts: a power optimizer, an inverter and a monitoring portal. Power optimizers improve energy harvest by placing a maximum power point tracker (MPPT) at the module level, with 15 milliseconds resolution. Power optimizers also condition the modules power output by eliminating losses stemmed from current mismatch, while decreasing voltage to increase string length. SolarEdge s power optimizers can improve string length up to 12,750 watts per string over 100 percent longer than traditional string inverters. Furthermore, the 2:1 power optimizer configuration helps bring down costs on the rooftop through a 50-percent reduction in parts count. SolarEdge offers 2:1 configuration for both 60 and 72-cell modules. inverter, each string would have required attention to the specific wattage and current levels on the modules. However, because they used SolarEdge, they were able to incorporate varying module power levels within the same string. SolarEdge s module-level MPPTs have the ability to condition the current and voltage output for each module pair. Power Optimizer 2:1 configuration Inverter 9kW - 20kW Monitoring Communication & Control Gateway Firefighter Gateway Designing with Optimized Inverters Region Solar created a two-module-high portrait configuration with a separate string at each level. The two strings were connected directly into a SolarEdge inverter at the end of the racking. Modules were wired in 2:1 configuration horizontally. Each module pair was connected in series to a single power optimizer. By keeping the top or bottom row on a single optimizer, the installer could reduce the impact of inter-row shading on the module pair. Region Solar sought to simplify its installation process as much as possible. By deploying SolarEdge SE20k inverters, this was easy; installers were able to connect up to 12,750 watts on a single string. So, with 310-watt modules, installers could create two strings of 40 modules and directly connect them to the SolarEdge SE20k inverters. Fully loaded on just two strings, the inverters did not require combiner boxes or fuses, which greatly simplified the installation process 1. Region Solar installed modules ranging from 300 to 310 watts. Had Region Solar designed the system with a central 1

3 The inverters were located on the same side near the center of the array for easy AC homerun construction. This design lowered the cost of wiring and the labor required to install cables. With SolarEdge s 2:1 architecture, connecting two solar modules to a single power optimizer, the cost of the SolarEdge solution was highly competitive with traditional inverter designs. Performance on larger inverters is risky. If you lose the inverter, you lose a large amount of the production. If any part for the array sees lower production due to clouds, vegetation or other reasons, it will create a high amount of mismatch losses. Andrew Tanner, President, Region Solar Why Not a Central Inverter? In the past, large PV installations traditionally featured large central inverters. This was an effort to decrease the upfront, day-1 cost as much as possible. However, as the industry matures and contracts are calling for more guarantees around production, lifetime energy yield is more critical to winning contracts. This puts an emphasis on risk reduction during the project s lifetime and motivates installers to build with string-level inverters in an effort to reduce the financial burden of servicing a large central inverter system. Originally, the system designed by Region Solar called for a central inverter. However, installations in Florida typically see variable cloud cover throughout the day, combined with rapid vegetation growth and soiling, which can severely affect production. With central inverters, having part of the array shaded results in performance issues that ripple throughout the remainder of the modules power_optimization.pdf SolarEdge can easily mitigate cloud cover effects. The power optimizers ability to adjust their MPPT within 15 milliseconds allows them to keep modules at their highest production levels throughout the entire lifetime of the array. Additionally, maintenance can cause a large central inverter to be down for many days. Service is complicated and typically involves an onsite visit from a highly trained technician often an employee of the inverter company. With smaller string inverters, spare parts can be stored on site. The technical knowhow to repair or replace an inverter is also lower. Furthermore, replacements are often as easy as with a small residential inverter. Smaller inverters also mean less energy loss during a service call. With a large central inverter, the entire site may be unable to produce energy. This can equal up to $1,000 in lost revenues. With a smaller string inverter (eg: 20kWac), the energy loss can be mitigated to only two percent of the array, or just $20 in lost revenues. The combined benefits of reduced green-to-green time (the time from component servicing required until the system is back up and running again) and reduced financial impact of a service event (two percent of energy yield vs. 100 percent with a central inverter) help the PV sites stay up and running longer. They are also better able to meet their contracted energy commitments under power purchase agreements (PPAs).

4 Savings with Optimized Inverters SolarEdge s inverters operate in an advanced, fixed-voltage mode and have been designed to work exclusively with power optimizers. SolarEdge three-phase inverters offer native support for 208Vac and 480Vac grids, avoiding additional transformer costs and energy losses. When the 20kWac inverter is loaded with a 1.25 DC:AC ratio or 25kWdc, an installer can build with only two strings. This eliminates the need to combine or fuse the DC side of a SolarEdge system, using instead the SE20kW inverters two native inputs to make all connections. The cost of homerun cables can be greatly reduced as well. 12,750 Watts 600V 1000V SolarEdge In an independent study conducted by third-party engineering firm Solvida Energy Group, engineers compared three inverter solutions: 600V central inverters, 1,000V string inverters, and SolarEdge s three-phase commercial inverters. SolarEdge demonstrated the greatest cost reduction in ebos costs, nearly eliminating the DC-side ebos entirely. Central 600 String 1000 SolarEdge c/w c/w c/w DC Labor DC Materials AC Labor AC Materials Total More specifically, SolarEdge reduced 50 percent of the ebos cost of wiring, labor, combiners and fuses when compared to a traditional 600V central inverter; when compared to a 1,000V string inverter, SolarEdge was able to reduce the ebos cost by over 30 percent, or about 4-5 cents per watt. Most inverters today come with a standard 10-year warranty. Thus, to avoid any hidden charges, installation owners should include the cost of an inverter replacement to accurately forecast the cost of electricity during a system s 20-year lifetime. For the central and string inverters that cost can be modeled in a few different ways: warranty extensions to 25 years, net present value of replacement inverters or service contracts. If we look at the warranty extension price for 25 years, we discover additional lifetime benefits to owning SolarEdge. Lifetime Costs Commercial Inverter System SolarEdge 1000V String ebos (M+L) Power Optimizer Inverter Replacement AC Materials AC Labor DC Materials DC Labor Central 600 String 1000 SolarEdge V Central The SolarEdge system offers the lowest lifetime costs. The SolarEdge inverter includes a standard 12-year warranty, while the power optimizer s warranty guarantees 25 years. Thus, the warranty extension is only required for the inverter portion of the SolarEdge installation. As a result, the warranty extension total cost is about one-third the cost of competing warranty extensions.

5 By comparing the material costs, ebos and life time costs of a central inverter, 1,000V string inverter and SolarEdge system, the Solvida study demonstrates that the SolarEdge system offers the lowest total cost of electricity. The SolarEdge system is able to achieve the lowest cost through the elimination of ebos components and the efficient deployment of fixed-voltage inverters and power optimizers. System Production Modeling To estimate energy yield over the system s lifetime, we use a PVsyst model to determine year-1 production. Production in years 2-20 are modeled with standard degradation rates for PV modules and a degradation rate for string induced mismatch losses. The array was built into PVsyst to build an accurate shading profile. Overall, the SolarEdge optimized inverter system recovered 1.5 percent more energy in year 1. This assumes that the site does not see added shade from vegetation or induced mismatch from varying cloud cover. A study of the loss diagrams in PVsyst reveals the sources of energy boost for the SolarEdge system: an elimination of module mismatch due to module-level MPP tracking. Since there is only one current (amps) value in series connections, all current outputs in the circuit must be the same. Typical PV modules accomplish this by moving away from their MPP, which results in lost energy. SolarEdge is able to isolate the module pair from the series connection. The power optimizers keep the modules at their individual MPP points while conditioning the output current from the optimizers to all match. Perspective of the PV-field and surrounding shading scene Production for each month was estimated to create a final yearly energy yield. Normalized productions (per installed kwp): Nominal power 1000kWp To calculate lifetime energy production, years 2-20 must also be modeled. Most simulation tools generate the simulation for the first year of installation, and do not take into account the module aging and mismatch growth. Lifetime yield must include module aging degradation of -0.5 percent to -1 percent per year (depending upon module manufacturer) and induced string-level losses due to additional module mismatch. A conservative value for this loss is an additional percent per year.

6 Inverter Over the lifetime of the system, the total advantages of optimized production yield an additional 2.7 percent greater energy output. This will generate an expected increase in revenues of $150,000 over the lifetime of the array 3. Monitoring Portal Year 1 Year 20 Lifetime Deg. (MWh) (MWh) (MWh) SolarEdge % Central % Benefit 1.5% 4.0% 2.7% The layout tab provides a birds eye view of the array s performance, inverter by inverter. Here, one can also observe the difference between residential and commercial layout tabs. In commercial sites, SolarEdge provides the option to consolidate modules down to the inverter level. This reduces the amount of data required to populate the view, while also increasing the speed and usability of the site. SolarEdge s dashboard view gives users an overlay of an entire site s production with real-time weather information and a comparison of performance by day, month or year. Installers are also able to place their logos on this page if desired. 3 Assumes $0.15/kWh electricity price with 3% escalator per year. Energy year 1 modeled using PVsyst. Years 2 20 modeled using -0.70% degradation rate for SolarEdge array and -0.82% degradation for central array. By selecting inverter groups and expanding the data, a user can see the individual module-level performance. Lighter blue modules indicate a higher energy production level, while darker blue modules indicate a lower production level.

7 By selecting any group of modules and right-clicking, a user can create graphs of power, energy, current or voltage. For this example, we we will create a current graph. Current Curve with Inter-row Shading Current Curve A graph of current production is useful to see the effect of varying light levels that strike the cells. Differences in current can be caused by a number of environmental or design factors. Installations with shading, soiling, vegetation or narrow ground coverage ratio (GCR) can display different levels of current production. In this graph, we are displaying the current production for a group of modules. Some of the modules are producing less current early in the day, which is due to inter-row shading on the site. You can also see how modules not affected by the shade are still producing at maximum power, although they may be in the same string as modules that are shaded. Voltage Curve with Inter-Row Shading Voltage Curve Voltage graphs have a different profile, as they tend to have a top hat shape since the voltage for a PV cell is not as sensitive to light. Voltages will increase rapidly in the morning, stay consistent throughout the day, and then decrease rapidly in the afternoon. It is common to see a bow in the middle of the day as rising heat levels will cause a decrease in voltage. This is a voltage graph of the exact same modules that have been shaded. In the morning, we can see a voltage increase relative to other modules that are unshaded. This is mainly due the shaded modules running cooler than the ones exposed to full sunlight. In some cases, you may also see the voltage decline by 33 percent in shaded conditions. This would be evidence of diode activation at the module level. Both conditions are examples of the modules and optimizers performing as designed.

8 Economics of Going Solar Overall, SolarEdge proved to be the best cost option to create an optimized system. With the ability to offset many production risks like cloud cover, soiling and vegetation, and to lower the cost of the 20-year warranty extension, the value for the customer, Florida-based VizCO-US, was compelling. I wanted to move to solar to mitigate the effect of brownouts. Each brownout costs between $300 and $400 in lost output from our manufacturing facility, said Chris Cantolino, Owner of VizCO-US Inc. Now, VizCO- US generates enough solar energy to cover 100 percent of its manufacturing needs. We are probably the only 100-percent solar-powered plastics manufacturer in the United States.