Assessing the influence of time-dependent power grid efficiency indicators on primary energy savings and economic incentives for high-efficiency cogeneration

In Italy, the economic support scheme for high-efficiency cogeneration annually provides tradable White Certificates to new constructed or refurbished high-efficiency cogeneration plants over a period of 10 years, proportionally to their annual primary energy saving. In contrast to the legislation currently in force, which assumes the power grid efficiency constant, this paper aims at assessing the adoption of a time-dependent approach, based on the use of the thermoelectric-based power grid efficiency, for evaluating the primary energy saving ensured by high-efficiency cogeneration as well as the relating economic incentives. The case study being analysed includes two 5.5 kWel micro-cogenerators installed in Naples (South Italy). Beyond the conventional, three scenarios have been outlined, depending on the time accuracy adopted (yearly, monthly and hourly basis). Starting from 2016, the scenarios have been replicated over the ten-year incentive period. In particular, the annual average thermoelectric-based power grid efficiency has been forecasted from 2021 to 2025. Following the innovative approach proposed in this study, the White Certificates would have increased by 9.2% in 2016, by 6.1% in 2017 and by 6.1% in 2018 too, thus fostering the achievement of the targets about high-efficiency cogeneration at national level.