While many control problems fall into the general category of regulation or setpoint following, the control of renewable energy systems has a wider variety of objectives, including energy conversion maximization or minimization of the cost of the converted energy. Given the intermittent and potentially unpredictable nature of many renewable energy sources, there may also be objectives related to matching supply with demand. This chapter focuses primarily on intermittent renewable energy sources, such as wind, wave, tidal, solar, while some consideration is also given to salinity gradient, and ocean thermal. This chapter discusses resource and system modeling, and outline solutions to typical renewable energy control problems.