THE COST OF UNCERTAINTY
How much energy can this plant produce? Given a variety of cost- to-output considerations, how much should it ideally produce? The margins of error on the answers to these questions can make or break the economic success of a solar project.
Developers need accurate data – the more precise and site-specific, the better – to inform their energy output estimate. To gain the best return on investment when selling a project, the plant should neither over- nor under-deliver on the estimated energy output. To sell for $2 million a plant that could have sold for $2.2 million is just leaving money on the table.
Construction of a solar plant typically costs $20 to $200 million. A met station at the construction site runs perhaps $30,000 – a comparatively tiny investment in the accuracy of the energy estimate, which can translate into such potentially significant gains for a developer. In wind farm development, where construction costs tend to be even higher,
met stations have become standard practice. In solar development, savvy developers are beginning to appreciate their role in reducing risk and enabling more accurate calculation of multiple factors affecting costs and return on investment.
For example, met stations enhance the likelihood of strong returns when financing is based on P75+ values. PXX, the probability of exceedance of the energy estimate, is a value used in assigning risk
to investments. It refers to the chance of overproducing and is a product of a project’s uncertainty values. The greater the uncertainty, the lower the P75 value assigned. For example, P50 indicates a 50/50 chance the output will match predictions; P75 means in three out of four years it would generate as anticipated.
When a met station delivers actual -- as opposed to generic or eneralized or regionalized data -- it reduces the margin of error on the energy output prediction. Greater certainty yields a tighter probability distribution. Many projects are financed based on P90 projects where
uncertainty is all the more damaging. In short, the met station’s higher accuracy of data drives higher PXX ratings, an important factor in gaining better returns.