The role of optical engineering for clean water problems

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Limited access to clean water has been the issue discussed in the world, no exception in some remote areas in Indonesia. The main problem is the source of clean water that has been polluted by industrial waste.

The scarcity of clean water sources caused by climate change and the human population and the increasing human population tends to lead to an unsustainable natural resource retrieval pattern, including clean water sources (e.g., groundwater, river water, etc.). The main example is an excessive exploration of the groundwater source, while the tree continues to be felled so that groundwater tends to deplete. In addition to the destruction of nature, the growing number of human populations also increased greenhouse gases that triggered the occurrence of climate change; Where climate change alone can exacerbate the problem of scarcity of clean water sources.

Limited clean water sources create a domino effect on other aspects such as reducing food production, changing ecosystems, and supplying city community needs that have occurred in several countries in the African continent (UNESCO, 2012) and may occur in some countries in Asia and the Americas in the next few decades.

One of the real solutions in this clean water problem is to replace the treated water source. Water that has been processed only 3% of the total water on earth, namely surface water, including river water, lake, glacier, etc. While 97% of the total water on earth is seawater has the potential for long-term solutions for the scarcity of clean water sources. But the development of water-based clean water resources is still very minimal developed because it tends to be expensive and requires a technological adaptation that is not easy in countries with a high level of poverty and developing countries.

The process of transforming seawater into drinking water is called the desalination process, which is the process of eliminating seawater contamination such as salinity and other ion ions that are not needed to produce clean water. Thermal and membrane technology dominates desalination technology, which both require costly maintenance and high technology support. Thermal and membrane technology requires less fossil fuel. These reasons are the main barrier to developing countries and disadvantaged countries to use desalination technology.

Solar energy can be a solution for desalination processes in developing and lagging countries. In addition to cheap, solar energy is also environmentally friendly and very abundant in number. Solar energy-based desalination is using solar heat as the primary energy to heat the seawater to produce moisture, which will be harvested as clean water.

This technological approach has a deficiency in its heat conversion efficiency. Often the heater is less able to deliver heat energy from the sun to heat the seawater. There have been many approaches used to maximize the application of this technology, for example, by using materials that can absorb heat and add dyes to the seawater for the water to evaporate quickly.

In research conducted by our research team (research team of Environment and biology Engineering of Unair), we use the optical engineering approach as a solar thermal energy concentrator to seawater. Besides, we also approach the use of copper-based materials that have high efficiency in delivering heat.

The optical engineering form that we use is the Fresnel lens, which is a lens that has a super high focus on focusing heat into the seawater. This research uses the seawater of Surabaya, which has been heavily polluted by household waste and perhaps also the industry. So it can be imagined very many ions that must be eliminated to produce clean water.

The results showed that the use of the Fresnel lens on the reactor that we designed could increase solar-based desalination efficiency. By 16% (3% in heat phase, and 20% in the cold phase). The results in our validation by calculating evaporation or evaporation using a modeling approach, which turns out its efficiency by 18%. Due to the distance of field studies and models less than 5%, it can be concluded the results of this study have statistically high validity. Furthermore, the use of Fresnel lenses can also heat more water proven evaporation that occurs during cold phase (no sun) reactors with Fresnel lenses have a 20% better efficiency than those using only conventional glass.

Author : Wahid Dianbudiyanto, S.T, M.Sc

UNAIR Environmental Engineering Lecturer

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