The UK Government seeks to reduce green house gas emissions by at least 80% by 2050. As a contribution towards they they have a target to have 15% of UK electricty generation from renewables by 2020. The Scottish Government have a target for renewable sources to generate the equivalent of 100 per cent of Scotland's gross annual electricity consumption by 2020.
As the proportion of unpredicatable intermittent input to the system increases, thermal generators used to balance the system need to operate at less efficient levels resulting in extra emissions and extra fuel costs.These emissions are denoted here as system emissions. It may be that the level of system emissions will increase disproportiately as the proportion of intermittent generation increases. The effect of system emissions on the GB System is uncertain since no study of it is known.
Reliable information about the amount of emissions from the Electricity System must be based on estimates that include emissions over the lifetime of all facilities including those due to fuel extraction, transportation, construction, firing, maintenance, decommissioning and of system emissions. Of these, emissions those due to firing and system emissions are denoted as operational emissions. The proposed Total System Analysis would include estimates of the operational emissions. Estimates of non-operational emissions would be made in a separate study.
In the absence of such a study, the level of reliability of any policy for reducing CO2 emissions should be treated as low.