The idea is appealing: a two in one system for green power generation; a photovoltaic sub-system for the times when the wind isn't blowing or is blowing at a slow speed, and a wind powered sub-system for nighttime and periods without sunlight.
Hybrid systems can minimize the intermittency problem of renewable systems
A typical hybrid solar-wind power system comprises photovoltaic modules, a small wind electric turbine, electronic controllers, a battery bank and a diesel engine-generator.
To provide a given output, each individual parts of the hybrid system is designed with a smaller output than the one it would have if operating separately. That is, to get an output of, say, 300 kWh of electricity per month the system is designed with, say, a 4 kW wind turbine instead of, say, a 6kW one; and the same goes for the photovoltaic part of the system.
Obviously, the output will depend on the site's solar and wind resources.
If the wind sub-system has a rated capacity of, say, 3 kWh (kilowatts per hour), do not expect it to produce such output. The real output is often estimated at 10-40% of the rated capacity.
As to the photovoltaic subsystem, its output will depend on the size of the solar array and on factors like solar irradiation, shading and panel orientation. Image: EERE.
Prices of hybrid systems are higher than simple solar (or a wind) systems, for the same electric output.
When to consider a hybrid system
As mentioned earlier, hybrid systems can minimize the intermittency problem of renewable systems, which is important.
But they are subject to the same ultimate constraints of non-hybrid systems. They will only perform their best with good wind and solar resources.
Hybrid-Solar-Wind Powered system & advantages
Hybrid solar-wind powered systems only become a cost-competitive option in areas where wind and solar patterns supplement each other significantly; otherwise they will be too pricey.
Also do not forget that energy efficiency comes first. In other words: if you want to install a hybrid system to meet your home's electricity needs, consider insulating your home to high levels and install high-performace windows, appliances and lighting, in order to reduce the electricity consumption to the lowest extent possible. Only then a hybrid wind-solar system can make sense. Otherwise you'll need a very large and expensive system.
There is a growing number of companies with hybrid solar-wind electric systems, including some big Asian manufacturers: American Southwest Windpower, Alfa Power, Prolight Systems, Suntechnics, Windpowerindia, ZenithSolar...