Wind and solar PV generation ramping events from farm to national level: the case of Ireland

Renewable energy sources (RES), such as wind and solar photovoltaic (PV), already account for a large share of today’s electricity systems. This share is set to grow significantly in the near future, due to ambitious emission reduction targets. A significant proportion of energy generation in the future, therefore, will be dependent on local weather conditions, which can change significantly over short time horizons. These sudden changes in renewable generation will need to be managed by electricity grid operators, who will need to ensure sufficient reserve capacity to maintain grid stability, particularly if an increase/decrease in renewable generation is coincident with a decrease/increase in electrical demand.

RES-induced ramps are generally caused by changes in weather, which result in rapid, large changes in electricity generation, particularly as weather fronts sweep across a country with the associated winds and cloud coverage. Other events linked to large ramps are solar eclipses for PV and high-wind periods that can lead to wind farm shutdowns. RES ramps are defined as changes in generation, taking place over a number of hours, that exceed a given threshold. In this work, we explore ramping events over Ireland at farm and national scale. First, we explore ramps at individual farm level using data provided by EirGrid, the Irish transmission system operator. Next, we evaluate how ramping events at a national level compare, derived from the combination of all farms. The aim of this first part is to characterise the behaviour of current wind and PV ramps, by means of their duration, magnitude and timing, as well as their temporal and spatial patterns.

We will then extend our analysis beyond the available historical generation data, by using models driven by ERA5 reanalysis data to generate hourly, farm-level wind and PV data from 1940 to today. We will quantify the skill of our modelled data, and use it for temporal and spatial analysis of RES ramping events, allowing us to capture a broader range of extremes and return periods, and better understand the seasonality and temporal cycles linked to ramps. Finally, anticipated changes in ramp patterns under the 2030 target of 80% RES in Ireland will be explored, considering the planned developments in capacity for the different technologies, located both onshore and offshore.