There are technically feasible solutions to the intermittency problem, but - as the paper discusses - it's very difficult to scale them up to provide utility-scale backup for 12 or 24 hours without sun or wind. (This is presumably why they are rarely put in place.) So there are hidden challenges here: financial costs of building energy storage systems; land requirements; mineral demands; and environmental impacts of each option.

We recommend you read the full paper to consider our discussion of such issues.