Research on solar desalination system and water-saving farming methods for small-scale farmers

Abstract

In 2017, the United Nations designated 2019 as the “Decade of Family Farming” and requested the promotion of measures and sharing of knowledge related to family farming, which plays a significant role in eradicating poverty and hunger. We are proposing a water-saving farming method for small-scale farmers using a solar-powered desalination system and purified raw water. Desalination plants generally use reverse osmosis membranes, disinfection chemical materials, and consume large amounts of fossil fuels. The solar desalination system we have developed so far is a low-cost, repeatable system that uses the same vacuum heat-absorbing tubes used in solar water heaters. We consider that small-scale farmers are also less burdened by using solar heat, a renewable energy source. The result of calculating the energy conversion efficiency from the measurement of evaporation was 43.9%. Next, water-saving agriculture is so crucial for the efficient use of purified raw water for agriculture. And the water-saving farming method base on the stone mulch farming method, laying bricks on top of root-proof sheets and using localized tillage. The stone-mulch farming method reduces evaporation of water, and the root prevention sheeting relatively reduces competition from weeds. Fertilizer and soil can be added to a locally tilled area to provide intensive nutrition. It also allows for continuous cultivation without removing stones and prevents soil drying and deterioration caused by full tillage. Although in Japan, the experiment of cultivating onions in the open fields using this farming method resulted in nearly double the harvest compared to the conventional method using a tiller.

In the future, we will develop the technology so that small-scale farmers, such as family farmers, can engage in production by also combining it with drip irrigation. And we will also continue to develop a desalination system using a flat plate heat absorber, which is easier to handle.