ABSTRACT
This chapter deals with the role of agricultural sky in farm power generation and related aspects. Wind and solar energy generation are two important aspects of agrarian regions.
Wind above cropping expanses is a vast source of power. It could serve the entire world’s need for electricity if we adopt suitable methods. Wind is an integral part of any agrarian sky. Wind gets generated based on differential atmospheric pressure in the sky. Wind speed is an important determinant of power generation. Wind could be erratic or steady. Wind that blows at low altitude and possesses a certain degree of turbulence can affect ground surface. Loss of topsoil from the felds due to it is common. Low altitude wind encounters obstructions to its free fow. Slower wind produces low amounts of farm power. There are a few distinct types of windmills adopted in farming regions. Simplest of technology was already in vogue in 12th century in European farms. They were originally adopted to grind grains and irrigate farms. In North America windmills were again small and were in operation by 1820s. They were called “windpumps” because of their utility in supply of water to crops. By the 1940s wind power was utilized to light rural homes in USA. Most ground surface windmills generate only small amounts of power enough to irrigate, supply power to farmhouse-holds, grinding, etc. High altitude wind power generation using tethered aerostats may offer greater amount of farm power. Wind speed is crucial factor that determines electricity generation. Wind speed of 9 km h-1 generates only 0.01 kwh-1 electricity. At 54 km h-1 wind speed about 2.2 kw h-1 power can be generated. Ground surface windmills utilize wind that blows at 100–200 ft altitude. 362Wind resources and speed varies with geographical location, topography and features of agricultural sky. Accordingly, potential to generate wind power too varies. On a Beaufort scale, at force below 3, power does not get generated. At force 7 windmills may get damaged. At high altitudes of 300–2000 m above felds, wind is uniform without intermittency. It blows at relatively higher speed. Hence, wind power from high-altitude turbine is a consistent source. Usually, a high-altitude aerostat-supported turbine generates power good enough for 7–8 farmhouse-holds and supply a small share to electricity grid. There are kite models that help in wind power generation.
Solar photovoltaic cell technology was frst standardized in 1950s. At present, United States of America and China are major solar power-producing nations. Together, they generate 30% of total solar energy produced worldwide. During recent years, several countries have developed “Solar Parks.” Solar energy is gaining in acceptance in the farming regions. The agrarian sky mediates the reception of solar radiation. Solar power conversion to electric power is achieved through photovoltaic cells. Solar panels of many sizes and specifcations to suit each location are available. Solar energy generation may involve small or large area. Individual farms with small holdings may utilize solar panels and generate power. Often large-scale electric power generation is conducted by adopting solar panels installed in vast areas (say, few km2). There are several countries that generate solar power using such “solar park.” Farmers may install solar PV cells (panels) simultaneously in the feld and reap crop as well as electric power. In Germany, such farms with both crops and solar PV panels are common. The system is called “Agro-Photovoltaics.” Sometimes solar power and crops are alternated. There are several applications for the solar-PV power generated in the sky above farms. It ranges from energizing water pumps, grain grinding machines, recharging electric farm vehicles, farmhouse lighting, etc.
