Integrating Energy Storage in Power Production: A Design and Scheduling Approach

Renewable energy sources (RES) are essential to reduce the carbon footprint of power generation. In the power generation field, an increase in the share of RES from 25% in 2017 to 85% by 2050 should be carried out to meet the sustainable requirements (IRENA, 2018). The two main renewable sources to achieve this goal are wind and solar. However, a new paradigm arises from their use. The traditional power systems are designed following the concept of large and controllable power generation units. But, with the introduction of RES, a distributed system appears where fluctuations over different time horizons impose a new operation of the electricity grid. To mitigate the high uncertainty using these renewable sources, energy storage is a powerful technology to help in the integration of variable renewable energies in traditional electrical power systems (Guerra et al., 2020). Several alternatives have been suggested to store energy for different power rates and discharged times (Gür, 2018). To integrate energy storage in the power grid, a suitable combination of the different technologies could mitigate the shortcomings of each of them. For instance, batteries could be appropriate for a short-term storage horizon to allay the hourly fluctuations in solar and wind availability. Also, different chemical fuels could be used on a seasonal scale storing a fraction of the energy avoiding an oversize in the energy caption unit.

In this work, the objective is to determine the optimal combination of wind and solar sources along with several energy storage technologies to be able to meet given power demand. The two most promising technologies to capture solar and wind have been considered: solar photovoltaic (PV) panels and wind turbines. To store energy, three different alternatives have been studied to integrate different storage horizons in the problem formulation: batteries, hydrogen, and methane. Batteries are suitable for a low capacity range but with a response time of the order of minutes. Hydrogen could be used for short/medium storage horizons due to the limited storage capacities and its high cost. Additionally, renewable methane can be used for long-term storage using the current natural gas infrastructure. Furthermore, biomass is a non-intermittent renewable source that can be used to provide a stable power production. Therefore, the integration of biomass with intermittent resources is also interesting in order to stabilize the power system. The effects of the integration of biomass into a wind/solar facility in order to provide stable power have been evaluated together with the storage alternatives proposed.

A scheduling approach has been employed to solve this problem. An hourly discretization of the time is necessary to capture the fluctuations in wind and solar resources and how to deal with them using the storage alternatives. The optimal capacities for the solar/wind capture units and the storage technologies (batteries, H₂ production/consumption, CH₄ production/consumption) are determined. The operation of the facility for a time horizon of one year is also calculated as well as the optimal capacities for these biomass processing facilities are determined considering the integration with wind and solar production.

The results closely depend on the weather conditions (wind and solar availability) and the biomass availability when biomass to power is introduced. Therefore, location is a key variable in the size and operation of these kind of integrated facilities. Therefore, a comparison of different sites in a country (Spain) has been presented, determining what are the variances between the design and operation of the facilities and proving a tool to determine what is the best location to set up this kind of facilities in the power grid of a given country. A social metric is also included in the comparison to deal with the problems of a fair energy transition. With this integration of technologies, a great step to reach a high rate of RES in the power system is get allowing it to meet the sustainability goals in the next years.

References:

Guerra, O.M., Zhang, J., Eichman, J., Denholm, P., Kurtz, J., Hodge, B.M. The value of seasonal energy storage technologies for the integration of wind and solar power. Energy & Environmental Science 13, 1909 (2020).

Gür, T.M., Review of electrical energy storage technologies, materials and systems: challenges and prospects for large-scale grid storage. Energy & Environmental Science 11, 2696 (2018).

IRENA. Global Energy Transformation: A roadmap to 2050, International Renewable Energy Agency, Abu Dhabi (2018).