Solar energy is only available during the day, whilst wind energy is available throughout the day, but it is more unpredictable as it depends on weather conditions. The generation of solar and wind energy on an independent basis is a major challenge: its discontinuity. Solar systems can provide a continuous source of energy during peak solar hours. On the other hand, the energy production of wind turbines is highly sensitive to variations in wind speed from one hour to the next, which makes it difficult to meet a constant load. In addition, fluctuations in solar and/or wind power generation do not typically match the time distribution of energy demand. This discontinuity is smoothed out by combining solar and wind in a hybrid system. Both nature resources are complementary to each other since, while solar energy produces during sunshine hours, the wind speed is usually stronger during nighttime.
A hybrid system consists of two or more sources of energy, in this case solar and wind power. The main components of the hybrid solar and wind system are the photovoltaic modules, the wind turbine and the tower, the inverter, a controller and an optional energy storage system. The resulting electricity can be fed into the utility grid, stored in battery systems and/or used directly in DC/AC applications. It is important to note that due to the combination of both energy sources, the battery bank size requirement is reduced when it is needed.
Despite the fact that the climate conditions of the site, solar radiation and wind resource, characterize the viability of a hybrid solar and wind system, under the right conditions, a hybrid power system that combines a variable speed wind turbine and a photovoltaic array will provide continuous energy according to the load with an optimal hybrid controller design as it is shown in the following figure. Designed accordingly, the hybrid controller ensures that energy demand is met throughout the year by smartly managing the energy flow between system components, while reducing energy costs.
Based on the location, grid specifications and time profile, a hybrid system can optimize the energy feed-in, increase grid stability and improve the capacity factor. Therefore, the combination of solar and wind hybrid systems is becoming more attractive as an alternative to fossil fuels.
ApriSolar has designed hybrid systems where solar photovoltaic technology has been combined with vertical axes wind turbines as well as horizontal axes wind turbines. In this way, the first solution is oriented to inner-cities large consumers where the space is limited and the wind speeds are low, while the second responds to large areas of land for energy injection into the grid.