Performance modeling for solar energy has many complexities and processes to navigate, but the fundamental goal for many project stakeholders is to understand how much energy a site is anticipated to produce long-term. This analysis ultimately underpins the financial modeling that allows a project to “go,” but there are often areas that are overlooked. Here is an overall breakdown of the most important aspects to be aware of and consider before you begin.
1. Adapt Early & Often
Perhaps the most critical element of performance modeling is the need to adapt swiftly and often. The utility-scale solar market is always changing with new technological advances. Leaders in this space must be progressive and reevaluate the modeling process frequently for new efficiencies. As an EPC (engineering, procurement, and construction) provider, Mortenson keeps a pulse on the latest updates in various tools, equipment, and methodologies and applies them to each project through a formal analytical process.
For example, the company has noticed a preferential shift in the usage of more bifacial modules in recent years. This technology has different production profiles that are currently being evaluated and tested in long term scientific test sites. Assessments must now be continually using updated data from test sites and other projects coming online using similar hardware and adjusted for weather.
National Renewable Energy Laboratory PV Testing Facility 2. Understand All the "Buckets"
In the performance modeling sequence there are hundreds of “buckets” of items to account for between Point A and Point B, or from sunlight to energy respectively. In the simplest terms, the goal is to determine how much sunlight the site is provided and how much energy will be produced to drive project financials.
Some examples of these steps, or buckets, that should be paid close attention to are:
- The unpredictability of weather since it is likely based on past assumptions
- The localized complexities of any particular site constraints
- The equipment and installation methods being used
- If any item is being under/overestimated
Did you know most of the racking systems used on Mortenson projects today are ground-based single-axis trackers? These trackers are continually improving in hardware design and supplemental software that can be programmed to improve yield from the project. Inverters, which convert direct current (DC) to alternating current (AC) electricity, are not all created equally and have large implications for projects as well. Mortenson proudly leverages strong relationships with many major equipment providers in the industry to help its customers navigate the procurement process and optimize plant designs.
3. Anticipate the Complexity
Following the same theme of main items to account for when performance modeling, characteristics of the site such as terrain and topography play an even more critical role now than ever. When utility-scale solar first gained popularity, project viability was initially limited to predominantly flat, open, and sunny land, like in southern California. As valuable land is being taken, the occurrence of working with less desirable land with more severe slopes and more irregular weather patterns is becoming more common. This of course creates a new layer of complexity with shading that wasn’t previously as much of a concern. If designed effectively and efficiently, the solar plant layout and energy model should accurately address these potential issues.
New data on the solar productivity is being published more often as the assets are online for longer periods of time. For more Information on terrain mis-modeling, higher-than-expected degradation and other causes of underperformance, read the latest kWh Analytics Solar Risk Assessment.
4. Test Thoroughly as a Final Check
Curating an accurate and realistic performance model for your solar project can also prove valuable during the close-out phase of the job, through a performance test. The purpose of the test is to validate that what was built is representative of what was promised and serves as assurance to the owner and the project’s financier, to ensure the quality and longevity of their investment.
These performance tests typically take place during the final stages of the project, and usually last anywhere from three to five days. Depending on the project, the industry is also seeing a growing trend to explore alternative testing methodologies and expand test duration beyond five days. While it may be handled differently from client to client and on a case-by-case basis, it is always a recommended practice to leverage the project’s performance model to ensure quality workmanship and long-term profitability of the solar facility.
At Mortenson we have customers from all ranges of experience on the subject, but we always make it our mission to coach customers on how the performance of their plant will affect their bottom line, even over a 30 year project lifecycle.
The list of considerations for evaluating assumptions in an energy model in solar is continually growing. Energy output is the best measure of productivity and ultimate likelihood of success for a project. Despite that, it is very easy to relegate all assumptions and implications of energy productivity to a single cell in a financial assessment without vetting out the real world variables that may affect it.
The next time you are building a solar project, discuss the assumptions you have for energy productivity with your partners through design phase and throughout the construction and commissioning of the asset. These conversations will ensure all project stakeholders go into the process with eyes wide open.
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