Characterization and evaluation of utility-scale intermittent renewable generation variations and implications for electric grid load balancing

Concerns over the increased impact of electrical energy use trends on the physical, economic, and political environments have motivated a shift to a low-carbon, renewable-based grid mix. The intermittent nature of wind and solar power, however, pose challenges for their use in conjunction with conventional generators.;To quantify these challenges, power spectrum-based methods for evaluating the magnitude and timescale of intermittencies in wind and solar power generation have been developed. The results reveal that the average magnitude of wind and solar power fluctuations decreases with increasing spatial diversification of the wind and solar resources. The reasons are associated with decoupling of the intermittency-causing events between the sites such as wind disturbances and cloud passes for solar arrays. The timescales of highest power fluctuation reductions are dependent on the spatial scale and governing weather or geographical factors. This implies a decrease in the typical fluctuations that must be managed by the electric grid as a fraction of total wind and solar capacities with increased spatial diversification.;To evaluate the effect of renewable power dynamics on the character of the load demand signal to which the conventional generator fleet must respond, the power output of different renewable resource mixes as a function of different renewable penetration levels was imposed on a load demand signal. Without a base load, isolated wind and solar power integration was found to pose severe challenges for balance generators in terms of low utilization, unused renewable energy, and highly dynamical operation at penetration levels starting at 22% and 28% respectively. Using a diverse renewable portfolio delayed the onset of such challenges until the 50% renewable penetration level. The use of a diverse renewable portfolio with an energy storage system mitigated the challenges posed by high renewable penetration levels to different extents depending on the power capacity and size of the bulk energy storage system. The scale of the bulk energy storage system, however, was found to be economically and physically impractical. It was determined that to reach high renewable penetration levels, a diverse energy management strategy portfolio must be implemented in combination with a diverse renewable resource portfolio.