These files are the core subset of the updated and expanded versions of the data originally collated for the 'UKERC Costs and Impacts of Intermittency - 2016 update' project, see https://ukerc.ac.uk/project/the-intermittency-report/
The data was updated for a paper in the journal Nature Energy 'A systematic review of the costs and impacts of integrating variable renewables into power grids', anticipated to be published in 2020.
Each file contains the data for a particular category of impact of Variable Renewable Energy (VRE). Detailed explanations of the nature of these impacts can be found in the UKERC report (see above).
File formats are CSV (comma separated variables) with text variables in quotes. File descriptions and column headings are given below.

Data_sources.csv
The 'Data sources' file contains a list of the original data sources. Column descriptions are as follows:
'Reference ID' - a unique ID allocated by the project team to each original data source.
'Relevance Rating' - the project team's assessment of how relevant to the project a particular source document was. The rating is between 1 and 4 with 1 indicating most relevant and 4 least relevant. Generally speaking, numerical data was extracted only from sources given a relevance rating of 1 or 2.
'Year' - publication year of the original data source.
'Title' - title of the original data source.
'Journal' - journal where the original data source was published, or publishing organisation if not a journal paper.
'Leading author' - name of the lead author of the original data source.

Operating_reserve_costs.csv
The 'Operating reserve costs' file contains collated data for the cost of additional operating reserves required by the addition of VRE to an electricity system. Column descriptions are as follows:
'Reference ID' - the unique ID allocated by the project team to each original data source.
'Penetration level (%)' - the share of annual electricity demand met from VRE.
'2017 Euros/MWh' - the cost of additional operating reserves, normalised to 2017 Euros.
'Region' - the geographical region to which the cost values relate.

Capacity_costs.csv
The 'Capacity costs' file contains collated data for the cost of additional capacity required by the addition of VRE to an electricity system. These costs are derived from the capacity credit. Column descriptions are as follows:
'Reference ID' - the unique ID allocated by the project team to each original data source.
'Penetration level (%)' - the share of annual electricity demand met from VRE.
'2017 Euros/MWh' - the cost of additional capacity, normalised to 2017 Euros.
'Region' - the geographical region to which the cost values relate.

Aggregated_integration_costs.csv
The 'Aggregated integration costs' file contains collated data for the aggregated integration costs resulting from the addition of VRE to an electricity system. Aggregated integration costs are an attempt to encapsulate all the other categories of VRE cost impacts into a single figure, but the interaction between impacts means that cost categories are not simply additive. Column descriptions are as follows:
'Reference ID' - the unique ID allocated by the project team to each original data source.
'Penetration level (%)' - the share of annual electricity demand met from VRE.
'2017 Euros/MWh' - aggregated integration cost, normalised to 2017 Euros.
'Region' - the geographical region to which the cost values relate.

Profile_costs.csv
The 'Profile costs' file contains collated data for the profile costs resulting from the addition of VRE to an electricity system. Profile costs are the costs arising from the temporal mismatch between VRE generation and system demand. Column descriptions are as follows:
'Reference ID' - the unique ID allocated by the project team to each original data source.
'Penetration level (%)' - the share of annual electricity demand met from VRE.
'2017 Euros/MWh' - profile cost, normalised to 2017 Euros.
'Region' - the geographical region to which the cost values relate.

Capacity_credit.csv
The 'Capacity credit' file contains collated data for the capacity credit values for VRE. Capacity credit is a measure of how much conventional plant can be replaced by VRE whilst maintaining overall reliability at peak demand. Column descriptions are as follows:
'Reference ID' - the unique ID allocated by the project team to each original data source.
'Penetration level (%)' - the share of annual electricity demand met from VRE.
'Capacity credit (%)' - capacity credit values.
'Type of VRE' - the type of VRE to which the capacity credit values relate.

Curtailment.csv
The 'Curtailment' file contains collated data for the curtailment values for VRE. Curtailment is the proportion of variable renewable output that cannot be accommodated on an electricity system. Column descriptions are as follows:
'Reference ID' - the unique ID allocated by the project team to each original data source.
'Penetration level (%)' - the share of annual electricity demand met from VRE.
'Curtailment (%)' - curtailment values.
'Region' - the geographical region to which the curtailment values relate.