Various designs and models of solar farming have been conceived abroad to suit local conditions, particularly the availability of sunlight. Some countries like Japan (where such a system is commonly called solar sharing) prefer to put up photovoltaic panels high enough to permit adequate solar radiation on the ground below them to grow low sunlight-requiring plants. Germany, on the other hand, has designed photovoltaic modules that can rotate to face the sun all the time.
In India, the most suitable and scientifically tried and tested model of agri-photovoltaic system has been evolved by the Jodhpur-based Central Arid Zone Research Institute (Cazri). This system, according to Cazri director O P Yadav, is ideally suited to the country’s vast western arid zone spanning west Rajasthan, northwest Gujarat and parts of Haryana and Punjab, covering an area of around 32 million hectares. This zone receives copious solar radiation in most part of the year.
A 105-kilowatt (Kw) agri-photovoltaic farm has been established by Cazri at Jodhpur on a one-acre (0.4 hectare) plot. In this farm, about 49 per cent of the total land that lies between the arrays of photovoltaic panels and 24 per cent falling beneath these panels remain free for crop cultivation. The crops which do not grow too tall or require too much water are advised to be planted in such a farm. Cazri grew pulses like moong, moth and cluster bean, and medicinal plants like aloe vera, sonamukhi (Cassia angustifolia
) and shankpuspi (Convolvulus pluricaulis
) in kharif this year. The rainwater collected from the panel tops is channelled into an underground tank of one-lakh litre capacity. The electricity generated at the farm is metered and fed into the power grid at the prevailing rates.
Cazri suggests vegetable crops like chilli, cabbage, onion and garlic for growing below the panels. This helps reduce temperature around the solar panels and improves power generation. The crop cover in between the rows of the solar panels, on the other hand, helps check soil erosion to reduce the dust load on the panels, thus improving the efficiency of solar cells. Since effective solar radiation is generally available for four to five hours a day under Jodhpur conditions, a 105-Kw solar voltaic unit can produce about 420 Kw hours of power on a sunny day.
That said, an important point that cannot be disregarded is that setting up of such integrated agri-photovoltaic farms is typically a cost-intensive proposition. The Jodhpur-based facility is estimated to have cost over Rs 5,233,000 with an additional expenditure of Rs 700,000 on the water harvesting system. Such heavy investments may be unaffordable for most Indian farmers. It may, therefore, be advisable to encourage the solar energy entrepreneurs to consider joining hands with the farmers, on mutually agreed terms, to establish integrated agri-solar units, instead of going in for solo photovoltaic units. This will be mutually beneficial for both of them. Otherwise, agri-solar farms may not proliferate.