A novel grid-oriented indicator for evaluating the performance of energy systems

Although increasing renewable integration challenges grid operators, existing grid-oriented metrics fail to distinguish beneficial from detrimental exchanges to grid flexibility. These limitations call for a more comprehensive approach to assess energy systems based on their impact on grid flexibility. This study introduces the Negative Grid Impact (NGI) indicator, which complements traditional metrics by assessing energy system performance based on exchanges that hinder grid flexibility. The NGI is applied across three case studies (in Italy and Spain), each characterized by the same load demand, but with different energy system configurations. In particular, wind turbines and photovoltaic plants are considered, both without and with storage, and in the latter case, four storage capacities. The findings demonstrate that the NGI can provide different insights compared to traditional grid impact indicators that disregard the positive effects of some energy exchanges. Indeed, across all case studies, while traditional grid impact metrics would favour photovoltaic systems, the NGI favours wind turbines, whose minimum share of negative exchanges relative to the load is around 31%, compared to 37% of photovoltaics with a 4-hour storage capacity. The widespread adoption of the NGI could realign incentives toward renewable solutions that enhance flexibility, mitigating blackout risks and reducing operational and investment costs.