Hybrid Systems

Many homeowners and business owners, especially in rural areas, install hybrid systems to meet their needs, as discussed earlier (Figure 3.8). In fact, most residential off-grid wind systems in use in North America are hybrids that combine solar electricity with wind.

In some locations (like the North American Great Plains) you can count on consistent winds for power production. But for most of the world, wind turbines and PVs are a marriage made in heaven because winds vary throughout the year. They tend to be strongest in the fall, winter and spring — from October or November through March or April. At Dan’s educational center in central Missouri, The Evergreen Institute’s Center for Renewable Energy and Green Building, for instance, the highest average wind speeds occur from October through May (Figure 3.9). During these



Fig. 3.8: Hybrid System. This system consists of a PV array and wind turbine, two renewable energy technologies that complement each other very nicely.

months, a properly sized wind generator can meet most of a family or business’s needs.

Winds continue to blow, but less frequently and less forcefully through the rest of the year. Fortunately, though, sunshine is more abundant during this less-windy period. In such instances, a solar electric system can supplement a wind energy system, providing the bulk of the electricity while the wind turbine plays a backup role.

Because solar and wind resources are often complementary, hybrid systems provide a more consistent year-round output than either wind-only or PV-only systems. Sized correctly, in areas with a sufficient solar and wind resource, hybrid wind/PV systems can provide 100 percent of one’s electricity This complementary relationship is shown graphically in Figure 3.9.



Fig. 3.9: The Complementary Nature of Wind and Solar. Wind and solar energy often complement each other, creating a reliable, year-round source of electricity. Note how well solar makes up for the reduction in wind during the summer months at Dan’s education center, The Evergreen Institute, in east-central Missouri.

A hybrid wind/PV system may even eliminate the need for a backup generator. Moreover, hybrid systems often require smaller solar electric arrays and smaller wind generators than if either were the sole source of electricity. However, if the combined output of a solar and wind system is not sufficient throughout the year, you will either need to cut back on consumption or run a backup generator. A generator is useful because it is used to maintain batteries in peak condition, and it may allow installation of a smaller battery bank.