Ultimately, the use of forecasting allowed the plant operator to send commitments in line with what is required by the grid operator.

Solar Energy Becoming More Predictable Thanks to Forecasting

Buessler Etienne | Reuniwatt


The energy transition is the most ambitious revolution of the early century. Planet Earth is affected by our huge energy consumption, including that from fossil resources. The latter represent the dominant share of our energy mix since the beginning of the industrial period. This fierce resource consumption is causing unprecedented environmental events, thereby forcing both large and small powers of this world to gradually change their way of producing energy. And in this new era, renewable energy resources (RES) are the solution, including a dominant development for electricity production in photovoltaic (PV) and wind sectors.

Solar energy represents the largest potential on the planet, even if one must take into account its variability. The complexity to adapt the solar irradiance (energy due to the sunlight received by the Earth) in our energy consumption is mostly due to the presence of clouds above photovoltaic power plants. These create some difficulties in the coupling of solar power with the rest of the energy mix. In the case of PV, a plant’s output power may drop by 70% from one moment to another because of a passing cloud. A problem that is growing with an increasingly installed capacity of this resource and which can cause a serious imbalance on the network between the production and consumption of energy.

In recent years, the development of the energy sector has focused largely on the growth of RES. But our energy transition goals cannot be focused only on this, it should also guide us towards finding auxiliary technologies to support them. Suffering from the inherent variability of solar energy is no longer an option if we want to use more renewables in our energy mix.  Solar forecasting brings a reliable answer to this challenge.


Soleka, Reuniwatt’s solar forecasting tool

Soleka is a decision-making tool for all stakeholders in the PV value chain: plant operators, electricity providers, DSOs, TSOs and energy traders.

Soleka provides solar forecasting from one minute to several days in advance, through a combination of the most efficient methods:


Day-ahead forecasting (6 hours to several days ahead) uses weather data, downscaling methods (data refining and weather modelling) and a statistical method to obtain accurate data for forecasting irradiance in the coming days.

These information provided for the following day enable:

  • The power producer to send the network manager's commitment announcements;

  • Network managers to forecast the expected production for the next day and therefore to adapt the balance between production and consumption;

  • Traders in the energy market to have reliable information to speculate, which indirectly helps stabilize the volatility of the price of solar energy.

Intra-day forecasting (from 30 minutes to 6 hours in advance) uses satellite images to predict the movement of clouds and later extract the irradiance data on the study area.

This solution optimizes:

  • a more stable network management (intra-day balancing of supply and demand, use of backup systems and plants)

  • storage tools for industrials such as storage monitoring

  • a possible management by energy producers of commitment notifications at intra-day level.

Intra-hour forecasting, or shortcasting, (a few minutes to an hour in advance) is based on the observation of the sky from an imaging system developed and patented by Reuniwatt.

The information collected will help:

  • energy storage and microgrid stakeholders to better pilot their infrastructure ;

  • improve the accuracy of other types of forecasts in solar PV plants


Solar forecasting for PV + Storage

The Portail site in Saint-Leu, Reunion Island (French Overseas Department), is a project led by Albioma which corresponds to a photovoltaic plant of 986 kilowatts installed on the roof of a supermarket. The installation is coupled with a lithium ion battery of 1200 kWh storage capacity. Due to the important issues in the development of RES in non-interconnected areas, the entire installation is piloted by solar forecasts provided by Reuniwatt.

The key point of this technology is that it initially allows to have an accurate model of the production facility a day in advance (required by the transmission system operator). Secondly, the management of the system through the EMS is possible thanks to the forecasts, which provide a daily production of electricity with a trapezoidal shape, an appropriate management model for an easier monitoring of the grid operator.

Source : Reuniwatt

Ultimately, the use of forecasting allowed the plant operator to send commitments in line with what is required by the grid operator. Moreover, with a better control of the installation, Albioma was able to increase the share of the energy it injected into the grid from 88 to 95% thanks to Reuniwatt’s solar forecasts. The latter allow to know precisely when it is more appropriate to store/unstore energy. Thus, the whole project is a development model for a sustainable energy transition with photovoltaics.

About Reuniwatt
Reuniwatt is a young and innovative French company, which develops services for renewable energy operators, based on three core activities:
- Solar energy prediction, thanks to its patented solar power production forecasting tool: SOLEKA;
- Climatic database management;
- Energy mix expertise.
The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag

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