How 5-minute solar data improved Wärtsilä's forecast capabilities

18 December 2023

About Wärtsilä Energy Storage, Inc.

Finland-based Wärtsilä Oyj Abp remains committed to a sustainable future. Driving a mission of 100% renewable energy, the company’s 189-year history, combined with the 15+ years of proven performance by Wärtsilä Energy Storage Inc.’s (WESI) GEMS Digital Energy Platform in energy markets, provides a sense of trust for customers who are looking to modernize their assets, without sacrificing safety or quality. WESI continues to develop solutions that provide the reliability and flexibility that utilities, IPPs, and other energy customers are looking for to harness the potential of intermittent energy sources while strengthen the grid. With safety and intelligence at the heart of their innovative storage solutions, WESI delivers technology with purpose-built end-to-end grid management capabilities.

Wärstilä GEMS Digital Energy Platform (“GEMS”)

The Wärstilä GEMS Digital Energy Platform (“GEMS”) is an energy management system that integrates, optimizes, and controls generation assets, ranging from energy storage and renewables to thermal generation. As the penetration of renewables increases, power and energy management is more difficult given the larger volume of variable and intermittent generation. At the same time, however, renewables bring enormous opportunity – one which is carbon-free and low-cost. To compensate for variability and intermittency, we often think of energy storage for its superior response and flexibility. However, the optimum value of storage and renewables is unlocked by using sophisticated controls informed by accurate weather forecasts.

WESI’s GEMS has a long history operating both grid-connected and islanded projects that exploit renewables for their maximum benefit. One trend on the rise in many markets is co-located solar+storage. Though the business models are still evolving, they all benefit from powerful energy management systems (EMS) that demand accurate and precise weather forecasts. Leading the way is WESI’s GEMS Renewables+ solution that leverages Solcast’s advanced weather forecasting.

Day-Ahead Renewables Forecasting

Day-ahead renewables forecasting is valuable in deregulated energy markets and increasingly in bilateral contracts, independent of storage. GEMS includes an off-the-shelf capability for solar+storage plants that are contracted under PPAs which mandate the submission of day-ahead hourly energy declarations each morning, with various configurable parameters for the optimization including penalty structures for ramp rate violations (resulting in firm fixed power) or day-ahead hourly energy declarations being met within some tolerance (e.g. +/- 10%). Smaller commitments are easier to achieve, but these reduce energy revenues. Maximizing revenue requires balancing energy delivery with accuracy.

To perform this function effectively, GEMS employs stochastic optimization to produce an hourly resolution day-ahead commitment that accounts for the uncertainty in the PV forecast. Solcast provides confidence intervals for all the important variables necessary for accurate PV production forecasting.

Real-time optimization of a solar + storage plant requires updated weather forecasts

In both grid-connected and islanded contexts, GEMS orchestrates renewable and hybrid systems to reliably produce clean power that reduces and will eventually eliminate the need for conventional thermal generation. GEMS leverages Model Predictive Control to craft multi-day forecasted operational plans that take into account the Solcast data, ground-level measurements, and equipment availability, among others. True to the essence of Model Predictive Control, GEMS continually recalibrates its course through perpetual re-optimizations using the latest Solcast data available.

Integrated Solcast Data into Wartsila's GEMS.png Wärstilä GEMS Digital Energy Platform
Source: Wärstilä Energy

Combined with Solcast’s powerful weather forecasting, GEMS improves the dispatchability of solar+storage plants, making clean energy ever more competitive than fossil generation. Concretely, GEMS determines the optimal control strategy, comprising both the top-level plant schedule as well as the equipment-level setpoints, in an integrated and fully automated solution. As the solar conditions evolve throughout the day, Solcast’s regular forecast updates allow GEMS to continuously re-optimize plants as they deliver the scheduled power in a context of changing weather and changing battery state of charge.

The power of accurate 5-minute solar data in tracking weather patterns

Since integrating the Solcast API into its GEMS Digital Energy Platform, WESI has gained access to high-resolution, frequently updated weather forecasts that it uses for load, renewables, and price forecasting. This is essential to the Renewables+ solution, because many power markets are operating under five-minute schedules to address the volatility of solar and wind.

Because the team can focus on delivering more accurate insights to their customers, WESI is launching new features, and their customers are seeing better results. Plant performance is optimized, and customers can save money by accurately predicting the performance of their assets.

Impacts on Wärtsilä's operations

Wartsila Quote - Benefits of 5-minute solar data.png

  • Accurate and reliable forecasts enable WESI to focus on making control decisions.

  • Continuously updated, high-resolution forecasts improve the performance of renewables and storage plants.

  • Confidence intervals in Solcast’s data underpin the stochastic optimization to incorporate uncertainty in WESI’s GEMS controls.

Impacts of integrating Solcast data into Wärtsilä's GEMS.png

Access 5-minute solar data to effectively manage your solar assets and storage projects

Understanding weather patterns and their impact on solar production is crucial for making well-informed decisions about your solar projects. Like Wärtsilä, you can also access Solcast's high-resolution, frequently updated data for improved forecasting capabilities.

Our team would love to connect you with Solcast API access to begin evaluating our data. You can create a commercial toolkit account, or speak with one of our solar data managers to learn more or request a quote.

Learn more about Solcast's 5-minute data here.


[1] Solcast, a DNV company is a leading provider of solar irradiance data and forecasting technology, dedicated to bringing accurate data to the market and helping enable the energy industry to deliver the resilient power grids it will take to build a solar-powered future.

[2] For a ~250 MW solar+storage plant, this is approximately 1,000,000 new setpoints per day across all inverters to minimize curtailment, balance SOC, and optimally allocate power based on capability.

Harry Woods

Harry Woods


Harry is our Head of Marketing, and works with our customers and industry partners to discover and share the new and innovative applications of Solcast data that are being built every day inside the Solar Industry. He holds a Bachelor of Laws and Bachelor of Arts and has experience in Go-To-Market working with complex enterprise grade technology solutions ranging from Ethical AI to Telecommunications.