Contributed by Kleber Facchini, Director of Product Management, Commercial & Industrial, SolarEdge Technologies
As the pace of commissioning commercial PV systems increases while in parallel current systems mature, the market is looking at PV systems as more than just a source of clean energy. Instead, PV systems are now being viewed as long-term investments that need to be closely managed in order to improve their ROI and bottom line. As with any investment, the two main ways to improve the ROI of a commercial PV system are to increase energy production (and therefore annual revenue) and decrease lifetime costs. Let’s take a deeper look at how this can be done in commercial PV installations.
A common method for assessing the efficiency of a commercial PV site is performance ratio (PR). The PR measures the difference between the actual and estimated potential energy output of a commercial PV system. The measurement is the percentage of energy produced by the system out of the potential energy as calculated by the measurement of irradiance and temperature. Operation and maintenance (O&M) activities are performed in order to bring the actual output closer to the theoretical potential output of the system.
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However, one of the first ways to increase system energy production is actually during the design and planning process. When analyzing the different PV options available, plant designers and asset owners should select a system based on its ability to place more solar modules on the array (roof-top or ground-mounted). Many standard systems will reduce the number of modules that can be placed on the array due to design limitations, for instance by not allowing for different module layouts or string lengths, or due to objects or natural obstacles that partially obstruct sunlight. By selecting a system that is designed to overcome these obstacles, and therefore allows more modules in the system, a commercial PV system becomes more profitable from day one.
Another key way to improve the PR of a commercial system is to minimize power losses due to module mismatch, and thus increase system production. System owners and EPCs can work to future-proof commercial systems by implementing technology that mitigates mismatch and aging losses and protects against unpredictable environmental changes, new obstructions (e.g., antenna erected, growing trees, etc.), and factors such as soiling, uneven surfaces, irregular irradiance and self-shading under bifacial modules. Technology, such as module-level power electronics (MLPE), helps to minimize energy losses to only the affected modules versus impacting the entire string, by optimizing the DC power production per module. However, no matter how much future losses can be diminished, the likelihood is that there will be defective modules that will need to be replaced, even with high-quality modules. If a system uses technology that can allow replacement using any module available in the market, versus having to rely on costly stocking of modules, then costs can be further decreased.Powerflex developed the 2.4 MWDC rooftop solar system for Medline in Tracy, California. (Courtesy: Powerflex)
At the O&M level, providing a fast response to any sources that cause decreased production is another important factor in improving system uptime. O&M can be a very costly endeavor with slow response times. But with the advent of module-level, cloud-based monitoring systems that allow automatic alerts, real-time detection and remote troubleshooting, this process has become as simple as a few clicks in an air-conditioned office. Instead of O&M being a labor-intensive process of searching for “a needle in a haystack”, asset management teams can choose systems that provide targeted information so that the field crew knows where the issue is before they go to the field. This not only increases system uptime; it also improves the efficiency of O&M and potentially decreases costs.
Another factor when analyzing O&M solutions is to differentiate between two different types of O&M activities – preventative versus corrective. Preventative maintenance is intended to maintain the PV system at its highest working condition and limit system downtime. This usually requires an annual site visit to thoroughly evaluate the components of the PV system and check the system’s health. Standard systems require that each module be inspected to confirm they are properly working. This is a particularly burdensome, costly, and inefficient procedure. In some large-scale sites, it might even require the use of drones for inspection. In addition, it can expose maintenance personnel to unsafe conditions such as high voltages, heights, and even wild animals.
During preventative maintenance activity, maintenance personnel often uncover latent problems that have caused the system to have decreased energy production for an extended amount of time. This would then call for corrective maintenance to be performed. Corrective maintenance is conducted after an issue has been discovered and includes the actual repair process.
However, there is also an optional maintenance style – selective maintenance. With the use of advanced monitoring systems, particularly module-level monitoring, the asset manager is able to receive alerts to system issues in order to reduce trips to the site and time spent on site. This type of monitoring enables O&M service providers to perform site analysis for the AC and DC systems of the plant and only dispatch field personnel when it makes sense. For example, with such module-level monitoring, if a module has a failed diode, then an automatic alert will notify the O&M provider. The module can be easily identified, and a screenshot can be provided to the module manufacturer for a warranty claim. This means that during the next site visit, the O&M provider can take a module to replace the failed one, saving a field trip and positively impacting the O&M budget. This type of monitoring requires MLPE which is typically not offered by third-party services. More importantly, any type of third-party monitoring service will add costs, thus negatively impacting the system ROI.DSD’s 415.6 kW rooftop installation at the City of White Plains Sanitation Building. (Courtesy: DSD Renewables)
The optimization of revenue and costs can be directly related back to the original inverter selection. In recent years, the inverter selection became renowned for its influence on BoS costs, but more recently it has been directly associated with system production and O&M expenses. This is because the inverter manages 100% of system production and can control O&M expenses. For instance, choosing a DC-optimized inverter solution that offers cloud-based, module-level monitoring for free, not only eliminates a CAPEX cost, but also reduces ongoing maintenance costs and helps to increase system uptime. By taking advantage of selective maintenance, the plant O&M requires less time onsite and fewer trips. With rising labor costs, selective and remote troubleshooting which is enabled by module-level monitoring can dramatically reduce long-term O&M costs. Further, these types of monitoring solutions offer reports on array performance, such as panel degradation, that are often required by investors, banks, or utilities.
Because of these factors, inverter selection is seen as increasingly important for the ongoing health and production of a PV system. And as the competition heats up for which inverter can best improve the PR of a system, each of these factors becomes more essential. Therefore, when planning a large investment like a PV system, it is crucial to understand how inverters can increase system revenue and decrease costs throughout the system’s lifetime.
About the author
Kleber Fachini, Director of Technical Marketing, Commercial & Utility, SolarEdge North America
Kleber has over 15 years in electrical engineering, applications, and product management in the renewables and utility equipment industry. As Director of Technical Marketing, Commercial & Utility, he is responsible for conceiving, defining, and launching all related products across the continent. He also oversees the applications engineering team, who work directly with SolarEdge’s installer partners.
Kleber is a champion of processes that leverage his team’s strengths, cultivate collaboration, and result in a positive impact on the customer. He has a Bachelor’s Degree in Electrical Engineering and a Master’s Degree in Power Conversion from the University of Wisconsin-Madison.