The Renewables Symphony
Renewable sources of power are often called "intermittent" because wind blows most strongly in the afternoon and at night, while the sun shines only during the day. However, demand for energy – e.g., the switching on and off of lights or the plugging and unplugging of electronic devices throughout the day – can also be said to be intermittent. In fact, on aggregate, demand for power and supply of renewables follow a similar pattern. Based on summertime data from the Electric Reliability Council of Texas, this graph (included in the task force report) demonstrates that the shape of the load (demand) curve – which declines as people sleep at night, then rises gradually throughout the day – mirrors that of the renewables curve, because solar generation picks up during the day just as West Texas winds die down, and South Texas and coastal winds peak as the sun begins to wane. Moreover, as Michael Osborne points out, the same force that drives these wind and solar patterns drives the demand pattern as well, particularly in the summer – namely, the sun. In a nod to this harmony, he refers to the combination of solar and winds from around the state as the "renewables symphony."