Novel Heat Harvesting for Low Energy Draw Solution Regeneration: Simulation Study

Abstract

In hot regions like the Middle East, the road asphalt pavement experience many fluctuations in their temperature profile that provides the large dark surface area with intensive heat absorption capacity, which warms the roads up to 75°C or more in summer. This phenomenon is negatively affecting the performance and urban heating. On the other hand, the most amount of water available (about 97%) is low-quality water or seawater, which needs to be treated in an efficient way to cope with the dramatic increase on demand of clean water due to population growth and agriculture requirements. Several techniques have been used for water desalination and most are thermally based techniques. Therefore, they are consuming high energy per water desalinating volume.The aim of this study is to design a novel heat harvesting system combined with a membrane based unit, to produce clean water from impure water. The heat will be harvested from the roads and buildings, by a low-grade system through Forward Osmosis (FO) unit. The diluted draw solution (SD) will be regenerated at low operating temperature, while the road and building's roofs surfaces are cooled and maintained at a lower temperature.The proposed technology will save energy and enhance microclimate conditions as well. The innovative DS regeneration system was simulated by HYSYS V8.8 and the results show a 1.17 m 3 /hr of treated water can be recovered for each one-m 2 . The quality of water depends on the amount of heat harvested and, consequently the surface temperature. Potable water is achievable only when the surface temperature is higher than 70°C and, therefore a trim heater is recommended for the winter season otherwise, the water will be used for non-drinking applications. Although the required Capex for this technology is around $13778/m 2 , but the payback is two years.

Energy Efficient Seawater Desalination: Strategies and Opportunities

“…Compared with other stimuli-responsive draw solution, the thermal energy required to induce the regeneration process can be harnessed from readily available low-grade heat sources. [173,174] Ju et al synthesized poly(4-vinylbenzyltributylammonium hexanesulfonate) (P[VBTBA][HS]), a poly(ionic liquid) exhibiting LCST property, through free radical polymerization. [175] When 20 wt% of aqueous P[VBTBA][HS] was used as draw solution, the FO operation in active layer facing the feed solution (AL-FS) mode achieved water flux and reverse solute flux of %5.85 L m À2 h À1 and 1.13 g m À2 h À1 , respectively.…”

Novel integrated acid gas removal and forward osmosis draw solution regeneration system for saving energy and water treatment

“…It's worth mentioning that, other novel methods have been proposed for low regeneration energy consumption. [30][31][32][33][34][35] Therefore, finding the optimum DS regeneration technique is one of the main challenges for the future of FO desalination. The driving force in FO system is the difference in osmotic energy potential generated by osmotic agent.…”