Solar costs have dropped dramatically. Yet, the value of solar at mid-day is dropping as more solar comes on-line.  We need to invest in more R&D to keep lowering those costs and also the costs of battery storage.  This article by Virun Sivarum is a good read outlining the need.   It’s adapted from his book, Taming the Sun, published by MIT Press in 2018.   We’re Risking Our Future