Energy payback for energy systems ensembles during growth

During periods of growth, the energy payback performance of new energy generating technologies deviates substantially from the usual static measures of energy return on investment (EROI), and time to breakeven (t_B) for single systems. Here we examine the performance of growing ensembles, develop new measures of dynamic performance, and identify an optimum growth rate (largest value of net energy production) and critical growth rate (rate at which the ensemble generates no new energy). Hence, if ensembles grow too fast they can look like net energy sinks in spite of good (static) single system performance indicators.