The increasing penetration of variable renewable energy sources (vRES), such as wind and solar power plants, requires these technologies to actively contribute to power system operation, namely by providing ancillary services while participating in multiple electricity market products, including day-ahead and balancing markets. In this context, hybrid power plants (HPPs), in which wind and solar PV technologies share a common point of common coupling (Pcc) being managed a single plant, usually offer several economic and technical advantages whith respect to the individual vRES plants, especially if generation complementarity and energy storage systems exist. These include smoother aggregated generation profiles and higher combined capacity factors, as well as the potential to increase the power capacity that can be delivered with a high degree of confidence. As a result, HPPs are a more reliable renewable-based energy source for the power system that is capable of participating effectively in market mechanisms that require guarantee of availability.

This work investigates the power capacity that can be offered with a high level of confidence in balancing markets, by comparing existing traditional wind power plants with newly wind power plants hybridised with PV systems, based on a probabilistic power forecasting tool. Feature-based indicators are also explored to assess whether a dynamic selection of forecast quantiles, for example, as a function of forecast uncertainty or hour of the day, can enable to increase the “firm capacity” that can be traded in markets. Using several case studies in Portugal, the technical and economic metrics are evaluated with open-access market models capable of simulating revenues in both the day-ahead and balancing markets.

Preliminary results show that, although the share of time in which observed production exceeds low forecast quantiles is similar for standalone wind plants and hybrid power plants, the average power available during these periods is significantly higher in hybrid configurations. For the analysed case studies, this increase in available power represents more than 15% of the nominal capacity of the wind power plant. Thus, hybridisation can reliably deliver more capacity using the same Pcc enhancing the value of existing grid assets. As power systems progress towards near 100% renewable penetration, this additional “firm capacity” allows hybrid power plants to contribute more effectively to roles traditionally provided by conventional generation, particularly in balancing markets and ancillary service provision.