The world is facing a major threat of fast depletion of the fossil fuel reserves and highly polluting our environment. Most of the present energy demand is met by fossil and nuclear power plants. A small part is met by renewable energy technologies such as the wind, hydro, solar, biomass, geothermal etc.

As per the law of conservation of energy, “Energy can neither be created, nor be destroyed, but it can only be converted from one form to another”. Most of the research now is about how to conserve the energy and how to utilize the energy in a better way. Research has also been into the development of reliable and robust systems to harness energy from nonconventional energy resources. Among them, the wind and solar power sources have experienced a remarkably rapid growth in the past 10 years. Both are pollution free sources of abundant power.

All renewable energy sources have drawbacks. Wind and solar sources are dependent on unpredictable factors such as weather and climatic conditions. Due to both sources’ complementary nature, some of these problems can be overcome, the weaknesses of one with the strengths of the other hence making Hybrid solar-wind energy stations advantageous.

Solar energy is energy from the Sun. It is renewable, inexhaustible and environmental pollution free. By adopting the appropriate technology for the concerned geographical location, we can extract a large amount of power from solar radiations.
Wind energy is the kinetic energy associated with the movement of atmospheric air. Wind energy systems convert kinetic energy to more useful forms of power including electric.

Hybrid Solar-Wind System
A stand-alone wind system with solar photovoltaic system is the best hybrid combination of all renewable energy systems and is suitable for most of the applications, taking care of seasonal variations.

Solar and wind energy independent systems have drawbacks. The one that is common to solar and wind energy is their dependence on environmental factors such as weather and climatic conditions.

The Solar PV wind hybrid system suits to Zimbabwean conditions where sunlight and wind have seasonal shifts. As the wind does not blow throughout the day and the sun does not shine for the entire day.

Hybrid systems are usually built with lowest possible cost and maximum reliability. The high cost of solar PV cells makes it less competent for larger capacity designs whereas wind turbines cost relatively cheaper per same. Battery system is needed to store solar and wind energy produced during the day time. During night time, the presence of wind is an added advantage, which increases system reliability.

Advantages of the Wind /Solar System
– Reliability of the system is enhanced.
– The size of battery storage can be reduced significantly as there is less reliance on one method of power production.
– Significant improvement in terms of output and performance.
– Lower atmospheric contamination.
– Savings in maintenance.
– Silent system.

Solar and wind power generation complement each other better than previously thought, according to a study released by the Reiner Lemoine Institute and Solarpraxis AG.

 

Mrehwa Test Run Project
The wind speeds in Zimbabwe are considerably sufficient for wind systems .Ranging from 2m/s to 15 m/s depending on time of year and seasonal variations.
A wind /solar hybrid test run project comprising of 200 watt wind turbine,100 watt solar was carried out in Mrehwa near St Paul’s Musami Mission.

This hybrid system is catering for the household needs of a four member family in a 5 roomed house and enjoying electricity for 24 hours a day.
Before the inception of the wind turbine, the house was being powered by a 100 watt solar panel feeding into a 100 AH battery. They only enjoyed their entertainment system for about three hours maximum at full capacity before switching off other electrical appliances to save some power in the battery for lighting.

Upon installation of the Wind/solar hybrid system the family can enjoy access to electricity 24/7 without need to ration electrical gadgets. The battery is hardly drained to below 50% Depth of Discharge (DoD) which greatly prolongs the lifespan of the battery.

Conclusions:
Wind –solar hybrid technology is very feasible given the encouraging results obtained from the Murehwa project.
The project proves that the complementary nature of wind and solar energy can be utilized to our advantage, giving optimum utilization of resources and thus improved efficiency as compared with their individual generation mode can achieve.
However if funding permits more wind –solar hybrid systems can be installed in different areas to ascertain if the technology produces the same results.

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