Intermittent and stochastic character of renewable energy sources: consequences, cost of intermittence and benefit of forecasting

Abstract : Solar and wind energy are inherently time-varying sources of energy on scales from 10 minutes to seasons. Thus, the incorporation of such intermittent and stochastic renewable 11 energy systems (ISRES) into an electricity grid provides some new challenges in managing a 12 stable and safe energy supply, in using energy storage and/or 'back-up' energy from other 13 sources. In such cases, the ability to accurately forecast the output of "unpredictable" energy 14 facilities is essential for ensuring an optimal management of the energy production means. This 15 review syntheses the reasons to predict solar or wind fluctuations, it shows that variability and 16 stochastic variation of renewable sources have a cost, sometimes high. It provides useful 17 information on the intermittence cost and on the decreasing of this cost due to an efficient 18 forecasting of the source fluctuation; this paper is for engineers and researchers who are not 19 necessarily familiar with the issue of the notions of cost and economy and justify future 20 investments in the ISRES production forecasting. 21 Keywords: photovoltaic systems; wind energy systems; production prediction; cost 22 effectiveness. 23 24 25 26