Irrigation using photovoltaics in horticulture
Where irrigation in horticulture is needed, electric energy often is not available. So the problem of energy supply in areas far away from the electricity grid is one of the factors limiting farming activities and rural development. Photovoltaic units have been developed to a real supply possibility. Solar radiation is available anywhere in the world. Even in northern Germany a potential of solar irradiance is given satisfactory to a lot of different agricultural utilizations in the average of about 1000 kWh (square metre . a). The favourite application of photovoltaics in direct or alternating current in agriculture and horticulture are consumers far from the farm and mains network, such as: outdoor animal housings and stores, cattle watering tanks, electric fences, outdoor milking parlours, dryers, greenhouses, pond filling and ventilation, slurry oligolytic, wood irrigation, weather stations and several irrigation plants for horticulture. Irrigation is needed in many different regions for several cultures. Especially suitable systems using PV plants have to be selected on the basis of their energy demand and efficiency. Comparing the given systems the micro irrigation is especially recommended, connected with drip irrigation or micro jet. As energy for the water pressure and throughput mostly is short, that dripper equipment is privileged, which causes the less drop in pressure corresponding to the length of the pipe. The flow of three different dripper systems are compared relating to their flow per outlet along the pipe. It was found out, that in the investigated drip pipe system 1.0 bar pressure differnce results in about 1 l/h flow difference. Micro sprinkler need the same working pressure as drip irrigation; but it is cheaper and especially suited for permanent crops.