Solar-driven direct contact membrane-based water desalination System

We are currently facing a global water crisis. Our population and economies are growing and demanding more water. But our supply is threatened by climate change, wastewater, and pollution. Water shortage has affected millions of people around the world and the predictions made by WHO term thi

Project Title

Solar-driven direct contact membrane-based water desalination System

Project Area of Specialization

Mechanical Engineering

Project Summary

We are currently facing a global water crisis. Our population and economies are growing and demanding more water. But our supply is threatened by climate change, wastewater, and pollution.

Water shortage has affected millions of people around the world and the predictions made by WHO term this situation as a warning for the future. Many desalination technologies have tried to combat the global issue, however, the proposed methods demand a considerable amount of energy and complexities which inconsequent results in Environmental problems and lesser access for poor people to fresh drinkable water. Countries like the USA, China, and even European Union had made the notion of completely relying on renewable energy in the coming years.

We aim to design and develop a desalination system that extracts solar energy or low-grade energy to desalinate water. This project aims to achieve a sustainable and substantial reduction in cost by developing a membrane-based unit with a flat plate spiral thermal collector. 

The proposed technology, Direct Contact Membrane desalination is one of those technologies that can be applied to desalinate seawater and have the potential to operate on solar energy. Currently, large-scale industries use Reverse osmosis, multi-stage-flash, and multi-effect-desalination techniques. Although, these methods are not economical for small-scale water desalination systems

According to studies, the current technology of converting solar energy into electricity has shown an efficiency of up to 20%, while 80% is already lost, and operating at high-pressure pumps to desalinate water wouldn’t be economical. Solar energy can be used.

A Direct contact membrane desalination (DCMD) system involves two channels. One channel of feed water-a concentrated water having higher TDS- is separated by a hydrophobic membrane that only allows the vapors generated from the feed side to another channel, a cold channel of permeate or desalinated water that continually circulates for condensation. For temperature ranges of 30-80 degree celsius, flat plate thermal collectors can be best utilized. Flat plate thermal collectors are cheap, require no maintenance, and are a single-time investment. An output of 60-100L/m2.h can be obtained using the DCMD system

Project Objectives

The prime objective of this project is to implement solar energy as clean and sustainable energy for water desalination processes. The energy crisis and environmental problems have forced almost every country to look for clean energy resources.  To do so, the following objectives have been designed

1. To design and fabricate a flat plate spiral thermal collector.

The flat plate thermal collectors have been found one of the best methods to heat the water from solar energy, currently, this technology is used in solar geysers. Integrating this flat plate thermal collector with a water desalination module as a source of heat is insightful. The flat plate thermal collectors include a solar water heater thermos valve, which operates and allows water inlet at a specific temperature which is to be set according to changing seasons and weather conditions.

2.  To design and fabricate a Direct Contact Membrane desalination module.

The direct contact membrane desalination module is the heart of a system. It includes a Polyvinylidene fluoride (PVDF) membrane locally purchased. The design and fabrication of a module from a PVC plastic are done. It is relatively cheap and reliable than high-cost operating pumps in RO plants.

3.  To integrate the spiral thermal collector and Direct contact membrane desalination module.

The integration of a system is to unite a solar thermal collector output water to the DCMD module inlet, the high vapor pressure will ensure the high amount of flux transfer to permeate side of the module. On the permeate side, freshwater is continually circulating for condensation.

4.  Performance evaluation of the integrated system.

The performance evaluation includes:

1. The effects of output temperature of flat plate thermal collectors on the production of freshwater. The irradiation of solar light is not the same throughout the day and its impacts on water production are also the aim of performance evaluation.
2. The flow rate of saline water and freshwater affects the output of a system and it also needed to be evaluated for a system.
3. The flow rate of saline water in the thermal collector
4. The effect of salinity on the water production
5. The effect of cold permeates temperature effect, with and without solar refrigeration.
6. Comparison of results of the system with the current existing one.

Project Implementation Method

The project implementation involves the following steps:

1. Literature review

The literature review is a most important step and continued over some months to acquire all the important knowledge and features of a system to design a most effective one.

2. Design of a system

The system design is the set of parameters that are needed to be decided to take into consideration of many things, such as the available temperature difference from the flat plate thermal collectors, suitable design of a DCMD module

3.  Material purchase

The system is aimed to be economical and all the material is locally purchased, for instance, a DCMD module is made of a union joint of PVC plastic, and the thermal collector is made of an easily available copper tube.

4. Development of DCMD module, thermal collector, and solar refrigerator.

The direct contact membrane desalination unit was designed and then developed, the unit is made of a PVC pipe containing a PVDF membrane between the joint and it is made seal proof to avoid any kind of leakage. The inlet and outlet nozzle have been drilled and joined properly.

The flat plate thermal collector is made of a spiral design, where a copper tube of 15m is turned into the spiral and fixed in a frame covered by 6mm thick glass to cause a greenhouse effect to trap the heat.

Solar refrigeration is used to reduce the temperature of a cold permeate to increase the temperature difference, a driving force for freshwater production. Peltier effect is used for refrigeration using the Peltier module which requires a 12-volt dc power and can be easily coupled with the Solar panel to run it along with other axillaries such as pumps.

5. Integration of system

The flat plate thermal collector is integrated with the desalination unit. The outlet of a flat plate thermal collector is connected to a storage tank from where hot saline water is pumped into the desalination unit and the output of a cold permeate side is connected to the solar refrigerator. The output of a solar refrigerator is again connected to the inlet of a desalination unit to continuously circulate the cold water.

6. Performance and results.

The system will be subjected to performance evaluation to observe the freshwater production and its characteristics, such as; the output flow rate, TDS, and PH of the water.

7. Findings and conclusion

The findings will be obtained from performance evaluations and conclusions are to be written

Benefits of the Project

Following are the benefits of the project.

1. Safe drinkable water at a low cost.

Clean water is one of the basic needs of life and when people struggle to achieve even these basic needs, how can our society evolve to achieve the global standard of healthy life. And its importance makes it stand in 6th position in sustainable development goals.

Access to clean water and a portable desalination system than could be implanted where sun photons can reach. It is something that we demand from an inevitable technology and we aspire to achieve it. The access to clean water in deserted areas and energy crisis, like Thar in Pakistan. Thar has water springs and underground water resources but that water is unlikely to be drunk because of higher salinity and desalination techniques which can desalinate water at a low price and is highly intended to benefit the community living there.

Economic benefits.

The direct contact desalination system is an economical approach to water desalination as it is solely based on solar energy so no further electricity consumption bills. This project is primarily suitable for the underprivileged community which cannot afford heavy bills on even basics needs. This technology requires the least components and hence ease in maintenance and ease to comprehend its mechanism. All the parts are locally available and cheap.

Energy crisis

Solar water desalination system extracts solar energy to operate its function and electricity for other auxiliaries such as pumps contributes only a single unit a day that also can be operated using PV panel.

There is an abandoned and never-ending energy to extract and the highest fraction of energy is high as 92.42%

Having a system that doesn’t require electricity to operate makes it economical and suitable for sustainable development as the energy crisis is the largest single drain on Pakistan’s economy. This crisis stems from a fuel mix transformation as we rely more on imported furnace oil than renewable energy.

Environmental benefits

The world is more intended to rely on renewable energy because of the climate impact of greenhouse gases and other emissions from conventional power producing industries.

Water desalination systems currently operating; For example, Reverse Osmosis requires enormous electrical energy to operate high-pressure pumps for reverse osmosis, while the DCMD system being both economic and social benefits doesn’t rely on such equipment and hence no great amount of electrical energy consumption. The salt rejection ratio of the DCMD system is high up to 99%, which can be used in chemical industries to make other valuable products such as sodium hydroxide, hence no waste disposal on land and ocean. The auxiliaries such as the pump only consume 1 unit per day which can be supplied through the PV panel. 

Technical Details of Final Deliverable

Direct contact desalination is based on heated saline water, the heating can be accomplished in many ways, this project employs solar heat to heat saline water, and for that flat-plate thermal collector is used.

In [1] Kumar et al show that for temperature ranges of 30-80 degrees, flat plate thermal collectors can be best utilized. For this technology, the temperature range of 60-80 degrees is best suited. In a flat-plate thermal collector, the spiral thermal collector shows maximum efficiency which was reported as 75.31% with a temperature difference of 19 ? , [2] Moravej, Mojtaba, et al .In[4] Hashim et al study on the thermal collectors shows that lower flow rates achieve greater efficiency

In [3] Kumar et al studied the minimum and optimal flow rate in the thermal collectors for a region like Pakistan is 0.5 liter per minute (LPM). For that, a separate storage tank for heated saline water is used so that the effect of low LPM can be mitigated.

the specifications of a thermal collector.

1. Flat plate spiral thermal collector
2. 0.5 M2 surface area
3. 15-meter-long copper tube.
4. 6mm thick glass cover.

In the direct contact membrane desalination technique, saline and freshwater are separated by a hydrophobic membrane and metallic net to support the membrane, hence termed direct contact. The module is made of a PVC pipe and each membrane of 90mm diameter and module of 1 litter capacity of each channel are used. The prototype results without cooling systems show more than 1L/m^2.h of freshwater production.

For solar refrigeration, Peltier modules are used and prototype testing results showed that the system can create a temperature difference of water by 15? . The Peltier modules operate on a 12-volt dc supply and 10 Amp, which can be operated by a photovoltaic panel.

The model of system is shown below.

[1 ] Kumar, Laveet, M. Hasanuzzaman, and N. A. Rahim. "Global advancement of solar thermal energy technologies for industrial process heat and its future prospects: A review." Energy Conversion and Management 195 (2019): 885-908.

[2] Moravej, Mojtaba, et al. "Experimental investigation of circular flat-panel collector performance with spiral pipes." Journal of Thermal Analysis and Calorimetry 140.3 (2020): 1229-1236.

 [3] Kumar, Laveet, et al. "Modeling, simulation and outdoor experimental performance analysis of a solar-assisted process heating system for industrial process heat." Renewable Energy 164 (2021): 656-673

[4] Hashim, W. M., Shomran, A. T., Jurmut, H. A., Gaaz, T. S., Kadhum, A. A. H., & Al-Amiery, A. A. (2018). Case study on solar water heating for flat plate collector. Case studies in thermal engineering, 12, 666-671

Final Deliverable of the Project

Hardware System

Core Industry

Energy

Other Industries

Education , Energy , Manufacturing

Core Technology

Clean Tech

Other Technologies

Clean Tech

Sustainable Development Goals

Clean Water and Sanitation, Affordable and Clean Energy, Decent Work and Economic Growth, Industry, Innovation and Infrastructure, Responsible Consumption and Production, Climate Action, Life Below Water, Life on Land

Required Resources

If you need this project, please contact me on contact@adikhanofficial.com