Renewable build-up pathways for the US: Generation costs are not system costs

TL;DR

This study models renewable energy build-up pathways in the US, highlighting that generation costs alone do not determine system costs, and emphasizes the importance of combining wind and solar with storage or transmission to reduce surplus and costs.

Contribution

It introduces optimized pathways for wind and solar deployment in the US, considering backup needs and costs, using a lightweight model based on weather data, and highlights the importance of system integration.

Findings

Optimal pathways favor wind/solar mix of about 80/20 for minimal backup.

Least cost development starts with lowest-cost technology, then shifts as surplus costs rise.

Combining wind and solar reduces surplus generation and overall costs.

Abstract

The transition to a future electricity system based primarily on wind and solar PV is examined for all regions in the contiguous US. We present optimized pathways for the build-up of wind and solar power for least backup energy needs as well as for least cost obtained with a simplified, lightweight model based on long-term high resolution weather-determined generation data. In the absence of storage, the pathway which achieves the best match of generation and load, thus resulting in the least backup energy requirements, generally favors a combination of both technologies, with a wind/solar PV energy mix of about 80/20 in a fully renewable scenario. The least cost development is seen to start with 100% of the technology with the lowest average generation costs first, but with increasing renewable installations, economically unfavorable excess generation pushes it toward the minimal backup pathway. Surplus generation and the entailed costs can be reduced significantly by combining wind and solar power, and/or absorbing excess generation, for example with storage or transmission, or by coupling the electricity system to other energy sectors.