November 11, 2011 | by NRG Team Voices | Engineering + Technology, Solar Resource Measurement

Last month I attended the Solar Power International conference in Dallas, TX -- North America’s largest solar industry trade show with 24,000 attendees -- to gain greater insight about the industry we recently entered with our complete solar resource assessment (SRA) system.

NRG Systems' Solar Resource Assessment System


To measure or not to measure?

Based on what I learned, some developers are estimating the future energy production of a project without directly measuring the resource at the site. They use solar data derived from satellite and/or nearby measurements, and modeling. For smaller projects – residential and commercial scale – this is usually adequate. For utility-scale projects, not  measuring can increase the level of uncertainty and risk from the financier’s point of view. This can result in higher interest rates, and therefore higher project costs. Directly measuring the resource typically lowers the uncertainty; and the savings in the cost of capital often outweigh the cost of the measurement campaign.

Lessons from wind power

In the wind industry, resource assessment is widely accepted as standard practice for wind plant development. Not true yet for the solar industry. At SPI I attended a session on utility-scale project financing, and did not hear mention once of solar resource assessment.

There also appears to be a lack of standardization around what measurements are needed. Some of the available systems are quite costly. They require frequent maintenance (mainly to clean the sensors) and are power-intensive – which can be challenging during the pre-construction phase when grid power may not be available. As an industry, solar needs to find the cost-benefit sweet spot: the place where measuring to reduce uncertainty is worth the effort.

Delivering on solar’s promise

As the renewable portfolio standards, feed-in tariffs and other incentives drive solar projects to bigger sizes, it’s likely that financiers will require resource assessment as a standard process in project development. The solar industry needs to develop common, acceptable practices that balance the high standards of the scientific community with the practical demands of project development. If that happens, we all stand to win. Manufacturers, developers and financiers alike will benefit from solar projects that deliver as promised.

Brendan Taylor is NRG Systems' engineering manager for instruments.

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