Renewable energy and storage technologies are often thought of as sustainable energy systems and several life cycle analyses point to the positive energy return on energy invested for individual renewable systems. However, in order to power the various life cycle processes such as manufacturing, refining, and installation, fossil fuels are used to generate the required heat and electricity. Thus, there remains a question as to how the whole suite of renewable technologies, as considered in isolation from fossil fuels, can power their own life cycles. Because most renewable technologies have intermittent outputs due to intermittent inputs such as the sun, wind, and waves, it is unclear how compatible those power outputs are for our constant and high-power industrial processes. Storage technologies can possibly play a key role in providing dispatchable power, and storage systems are often quoted as being necessary to promote widespread use of renewable energy. This paper presents a methodology to measure innovation in renewable and storage technologies by using a time-varying renewable energy only energy return on energy invested – rEROI(t). Innovative technologies will therefore be those that make rEROI(t) increase over time. The methodology assumes that the power outputs of existing renewable systems would be the only source of power for the life cycle processes of making the next set of renewable and storage technologies. Thus, renewable systems are required to manufacture themselves.

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