Enhancing Energy and Water Use Efficiency in District Cooling Plants, An Innovative Approach for Sustainability in Hot Arid Regions
Authors: Hassabou Abdelhakim Mohamed 
Published: July 2019

With around 60–80% of electricity used for air conditioning, and around 99% of potable water production being supplied by desalination plants, sustaining life in Qatar, as well as GCC and hot arid countries around the world, is uniquely energy intensive.

As District Cooling Plants (DCPs) have a potential to reduce energy consumption and CO2 emissions, Qatar and GCC are continuously shifting paradigm towards adoption of DC plants to satisfy the rapidly growing demand in all sectors. However, DC plants usually rely on wet cooling towers for disposing the excess heat to the ambient. Thus the heat disposal is accompanied by considerable loss of fresh water, a common problem in hot arid countries with highest demand for air cooling and also relies on costly and energy intensive desalination processes for securing fresh water supply. In addition to this, evaporative cooling devices and wet cooling towers can spread humidifier fever, a serious health risk with similar symptoms as mild influenza, and Legionella, which can be deadly. Hence huge evaporation loss in densely populated urban centers in Qatar and GCC is an imperative environmental issue which necessitates effective and practical solutions.

This study presents an invention, which involves an innovative process called the “SELF-SUSTAINABLE DISTRICT COOLING AND DESALINATION (SSDD)”. The patented solution is directed to construct a totally new concept for maximization of water and energy use efficiency in district cooling plants in hot arid countries while preserving the environment. The system couples district cooling plants with polishing of treated sewage effluents (TSE) using hybrid reverse osmosis and thermal desalination technologies with the district cooling plant. The desalination process is equipped with a zero liquid discharge (ZLD) system to achieve full recovery of the TSE resource and eliminate the common environmental problem related to brine disposal. The invention closes the water and energy circuits in DC plants, which considerably enhances the overall water and energy efficiencies.

The techno-economic analysis of the SSDD technology has revealed a breakthrough in the technology in terms of reducing energy consumption by 20–30% and water consumption by more than 50%. Considering, for instance, a planned capacity of 1.6 million refrigeration ton DCPs to be added in Qatar by 2022, the SSDD can save up to 200,000 m3/day evaporation losses and 650 MW of electrical power together with elimination of water distribution power needed for pumping potable water from desalination plants to the DCPs. The total energy saving corresponds with 3.5 Million ton reduction of CO2 emissions and more than 1.5 Billion QAR/year excluding the environmental benefits. Considering the ambitious development plans of other GCC states, the SSDD technology may play a significant role in achieving sustainable development goals not only in the region but also worldwide. Thus it holds a great promise for energy and water securities as well as combating global climate change.

The new RO/ZLD concept can be used for applications other than DC, e.g. waste water treatment and reuse, aquifer recharge, football stadia, irrigation for the Qatar National Food Security Program (QNFSP). Moreover, this process can be applied around GCC, Middle East and North Africa (MENA) as well as other hot parts of the world.