# The role of spatial scale in joint optimisations of generation and transmission for European highly renewable scenarios

## TL;DR

This study investigates how the spatial resolution in optimization models affects the planning of renewable generation and transmission in Europe, revealing that limited grid expansion can be nearly as cost-effective as fully expanded grids.

## Contribution

It quantifies the impact of spatial scale on joint generation and transmission optimization in Europe, highlighting trade-offs and cost implications of different spatial resolutions.

## Key findings

- Higher spatial detail improves identification of transmission bottlenecks.
- Limited grid expansion increases costs by about 20%.
- Finer spatial resolution enhances renewable site exploitation.

## Abstract

The effects of the spatial scale on the results of the optimisation of transmission and generation capacity in Europe are quantified under a 95% CO2 reduction compared to 1990 levels, interpolating between one-node-per-country solutions and many-nodes-per-country. The trade-offs that come with higher spatial detail between better exposure of transmission bottlenecks, exploitation of sites with good renewable resources (particularly wind power) and computational limitations are discussed. It is shown that solutions with no grid expansion beyond today's capacities are only around 20% more expensive than with cost-optimal grid expansion.