Last year, I posted an article from Germany about the damage that increased cycling of power plants, due to balancing of renewables on the grid, is having on generation equipment :
In Eirgrid's Generation Adequacy Report for 2015-2024 published this year, they state that this is in fact the case now in Ireland :
Another aspect of plant availability is that of two shifting, which may result in a change to maintenance patterns. Two shifting is where a generator is taken off overnight or at minimum load times. This will occur more frequently with increased penetration of wind generation, and will result in the requirement for additional maintenance and increased Scheduled Outage Days (SODs)This then represents another cost to be loaded on to people's electricity bills.
Most engineers will tell you that turning on and off a large power plant like this is inefficient and will actually increase emissions. Its a bit like someone continually walking and running. It takes a lot of energy to begin running from a walking position but once you are running it takes less energy. This is because there is momentum behind you. Think of how much energy is required to stop running and to fight the inertia in your body. This is why its better to go running in a park or in the country, having to stop and start in a busy city street is not very efficient. Race tracks are designed like they are to give athletes the best chance. And so it is not very different with a gas or coal generator. But this is now the norm for many of them.