Reuniwatt is a leading expert in atmospheric science and solar forecasting with a strong focus on R&D. The company has won EU funding and has been nominated for The Smarter E Awards the second time in the category Smart Renewable Energy in 2019. Founder Nicolas Schmutz has his heart set on cloud observation and satellite-based forecasting techniques. He explains why R&D is so important, and why it’s worth investing in forecasting and monitoring for your solar plants.

Tell us about your background. How did you come up with the idea to start Reuniwatt 10 years ago?

“At the time, I was in charge of developing solar farms in Reunion Island for the French pioneer of photovoltaic. As solar energy developed very fast in Reunion Island, the grid operator was worried about the potential impact on the grid stability, and stopped connecting new solar plants to the grid. Something had to be done to offer a safe and massive penetration of solar on the grid. Solar forecasting is the simplest and cheapest way to mitigate the risk.

Please tell us why Reuniwatt chose to invest into R&D of its own satellite-to-irradiance technology for plant monitoring and how this technology can benefit the solar industry?

“Satellite-to-irradiance is a key technology for intraday solar power production forecasts. It is globally available thanks to 5 geostationary satellites observing all the earth’s surface. It has a suitable refresh rate (from 5 min to 15 min depending on satellite) and parameters are very stable over time, as there’s no soiling of the sensors in space!

As a pioneer in solar forecasting, it was our goal to develop the best skills in earth observation in order to deliver the best in class irradiance reconstruction. We have access to the raw data in real time, no extra time lag. If a new weather geostationary satellite is commissioned, we are the first worldwide to take benefits of its data.

We decided to push this science in the direction of the solar industry’s needs by developing SunSat™ Digital Twin – our easy-to-use monitoring tool which reproduces what a given solar plant from real world shall produce according to its architecture and the received irradiance. SunSat™ Digital Twin considers the meteorological effect and thus confirms the efficiency of operation & maintenance (O&M). Effects on the power output due to soiling of the solar modules, aging of materials, or lack of ground maintenance become visible.

One of your first products, the infrared sky imager Sky InSight™, is offering continuous tracking
and forecasting of the cloud cover. How is this still relevant now that you can use satellite data?

“Satellites are the best partner for intraday solar power production forecasting for the next hours, as well as for region-wide nowcasting, i.e. what is received in that moment on the ground surface; and for climatology, i.e. what has been received over the last decades.

The difference seems simple: Satellites observe clouds from above, Sky InSight™ observes them from below. Sky InSight™’s imaging system reconstructs the 3 dimensions cloud cover over the system, at night and during the day. A typical sampling rate is 30 seconds. Sky InSight™ is the best in class solution for local 5 minutes ahead solar forecasting. It predicts ramp rates of utility scale solar farms.


Your partnership with Voltalia is a huge step towards increasing the rentability of hybrid plants
in microgrids by means of forecasting solutions.
What further developments can we expect from such partnerships?

“We are proud to serve Voltalia in Brazil with our imaging system on their hybrid PV / gensets farm. This project demonstrates, how efficient an integrated solution merging know how of producer (Voltalia), genset controller (DEIF) and Reuniwatt can be used to reduce the cost of electricity while increasing the microgrid’s stability.

Our imaging system announces what PV will produce in the next minutes. It then warns the controller of the risk of production drops due to cloud masking of the sun. The controller adapts the number of operating gensets to our imaging system’s forecast to offer the best capacity factor of gensets. Each genset thus offers the best cost per kWh of electricity.

This complex integrated solution was a huge R&D effort for us, but it is worth it! It leads to an unrivalled low cost of operation for hybrid systems thanks to fuel savings; furthermore solar penetration is maximized, its risk is mitigated and the best cost of operation is guaranteed.

Thank you very much for all this information, Nicolas!

Nicolas Schmutz at Intersolar Europe 2019

About Reuniwatt (
Reuniwatt is a major player of the solar radiation and cloud cover assessment and forecasting. Based on solid Research and Development works, the company offers reliable products and services intended for professionals of various fields, making the best out of two key facets of the meteorology: atmospheric physics and data sciences. A particular focus has been placed on solar energy forecasting, while developing cutting edge solutions to improve the short-term prediction of the solar resource.
The company has won many grants, including H2020’s SME Phase 1 programme, which makes Reuniwatt a European Champion with regard to innovation.