Utility-Scale Solar Surpasses Wind in California for First Time in 2015 - Vaisala

High penetration of grid-connected utility solar increases market demand for accurate regional solar forecasting tools to manage energy scheduling and trading

Recent analysis from Vaisala, a global leader in environmental and industrial measurement, reveals that in 2015 energy from grid-connected, utility-scale solar plants surpassed wind for the first time in California. While this is an exciting milestone for the solar industry, the rise of solar also brings with it a demand for better forecasting information to cope with the challenges that the increase in variable generation poses to the regional energy system.


California has been a national leader in renewables since first establishing its Renewable Portfolio Standard (RPS) in 2002, and, with a 50% RPS mandate recently signed into law, it is likely to maintain its position for years to come. Today the state is still one of the largest U.S. wind markets in terms of capacity, but the exponential growth of large-scale solar in recent years has considerably altered the structure of the regional energy market.

Public records from CAISO (California Independent System Operator) indicate that over the past five years, grid-connected, utility-scale solar generation in California increased fifteen-fold. It went from a total of 1,000 GWh in 2011 to an impressive 15,592 GWh in 2015, composing 6.7% of the system total and surpassing wind for the first time, which made up 5.3% of the system total.

High solar market penetration benefits the state with lower carbon emissions and lower electricity prices, given that there is no associated fuel cost. However, as solar capacity has grown, so too has the effect of its variability on the market. As supply rises and falls, system volatility increases, influencing prices. In order to minimize price while maximizing clean energy generation, it is essential that the market is able to anticipate these supply swings and respond accordingly. In order to do so, energy schedulers and traders in California are increasingly demanding access to a high quality regional solar forecast, particularly for the day-ahead market.

In response, Vaisala has introduced a new regional forecasting service for the CAISO market to help it adapt to the increased volume of variable solar capacity. As renewable energy capacity has grown across the U.S., Vaisala has been at the forefront of regional forecasting. Its new regional solar energy forecast is designed to help the market better manage supply and pricing volatility and benefits from Vaisala's years of experience providing trusted, high accuracy regional forecasts to wind markets across the U.S. and Europe.

Through rigorous validation, Vaisala's CAISO regional solar forecast has proven to be consistently more accurate than the day-ahead public forecast. This is particularly true on cloudy days when anticipating solar availability is both incredibly challenging and highly important for scheduling and trading. For example, in CAISO SP-15 (South of Path 15), which accounts for a majority of the state's solar capacity, Vaisala's forecast successfully predicted reduced production days 60% more often than the public forecast over the last six months of 2015.

"California's continued commitment to renewable energy is very encouraging and creates a great deal of opportunity for the industry," said Pascal Storck, Global Manager of Energy Services at Vaisala. "But, as we've seen in many markets around the world, rapid capacity growth also inevitably places strain on regional systems. We are helping customers adapt and respond to market changes profitably and sustainably with a new state-of-the-art solar forecast that has been well received by clients in CAISO."

In addition to accuracy, Vaisala's regional solar forecast is also robust and intuitive and easily integrates with existing platforms. It provides projections up to seven days in advance as well as six months of historical forecasts and actual production data. Access is available both via API for fast delivery to Excel and other analysis tools as well as through a dynamic online dashboard, where it can be compared side-by-side with public predictions and actual production.

To learn more about the new regional solar energy forecast for CAISO, please contact Vaisala or visit the product information page.

Vaisala is an expert in wind and solar measurement, project assessment, energy forecasting, and asset management. For more information on the range of services offered by Vaisala to the renewable energy sector, please visit www.vaisala.com/energy.

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