Abstract
When it comes to water and energy, it is hard to obtain one without the other. Water is required to produce energy and energy is necessary in water production and management. As demands for water are escalating due to rapid population growth and urbanization, understanding and quantification of the interdependency between water and energy, along with analyzing nexus interactions, trade-offs and risks are a pre-requisite for effective and integrated planning and management of these two key sectors. This paper performs an assessment of the water-energy nexus in the municipal sector of the Eastern Province of Saudi Arabia, where the electric energy footprint in the water value chain (groundwater, desalination and wastewater treatment) and the water footprint in electric energy generation (thermal power plants) are quantified using data for the year 2013. The results confirmed the high and strong dependency on energy for the municipal water cycle in the Eastern Province and revealed that energy generation dependency on freshwater resources is also major and evident, especially at farther distances from the coastal areas. Thermal desalination is by far the most energy intensive stage among the entire Eastern Province water cycle. In 2013, it was estimated 13% of the Eastern Province energy generation capacity goes for desalination, that’s a 5% of the Kingdom capacity. Substantial energy input for desalination in the Eastern Province is attributed to the production and conveyance of water to the Capital Riyadh (48.9 kWh/m3 and 4.2 kWh/m3 respectively). As for groundwater pumping, it was estimated that 206.2 GWH was used for pumping 268 MCM in 2013 (0.764 kWh/m3). Energy requirement for primary, secondary and tertiary wastewater treatment was found to be the least (2 - 108 GWH) and was equivalent to an average of 0.4 kWh/m3. The water footprint in electricity generation was estimated to be about 739,308 m3 in 2013 (0.125 m3/kWh), a relatively higher value compared to the norm of gas combustion turbine cooling water requirement around the world, and is especially significant for water scarce Kingdom. Anthropogenic Greenhouse Gases (GHG) emission was computed to be around 17 Million Ton of carbon dioxide equivalent (CO2e) for the entire water supply chain, with desalination having the highest carbon footprint in the whole water cycle (16.9 MT of CO2e). Carbon emissions from electric energy generation through power plants had significantly exceeded the entire water supply chain’s carbon footprint. Alternative mitigation options of management and technology fixes are suggested to reduce energy consumption in the water cycle, minimize the water footprint in electric generation, and mitigate associated GHG emission.
Highlights
It worth mentioning that should the pump efficiency increase to 83%, the energy requirement for groundwater pumping will be in the dropped to 192 GWH. 2) Desalination Multistage flash distillation (MSF) is by far the most energy intensive process among other desalination technologies in the Eastern Province with energy consumption reaching 19,339 GWH in 2013 representing 74% of total energy input in seawater desalination
Substantial energy goes into water production, thermal MSF/Multiple effect distillation (MED) desalination, which was revealed to be the most energy-intensive process and represents the majority of energy input in the water value chain
The Eastern Province thermal power plants are dependent on groundwater for cooling especially in the inland plants
Summary
The issue became a strategic policy for future planning and management of the growing water and energy challenges. Even though renewable energy sources, or the so-called green energy alternatives, appear to have zero reliance on water as they do not require water for cooling, yet water is integrated during their life cycle [14] Both wind turbines and solar panels—photovoltaic consume negligible amounts of water during the cleaning process, concentrating solar technology known as solar thermal is thought to consume approximately five times more water than a conventional gas fired power plant, twice as much water as coal fire power plant, and 1/2 times as much as a nuclear plant [8] [14]
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