The coupling of renewable energy with desalination has understandably created a real global buzz. After all, it’s a match that’s meant to be (like a long engagement without the wedding). The desalination market is trying to shift its legacy image of providing pure water (potable drinkable water) associated with the high energy cost. Partnering with cleaner and sustainable energy sources is always a good way to do so.
Merging Renewable Energy and Desalination has been discussed at length from previous Caribbean Water and Wastewater Association (CWWA) conferences. Bringing together these two (renewable energy and desalination) without a major breakthrough of a large-scale, independently powered projects coming online can solve much of the water resources issues facing the Caribbean.
particularly suitable instrument in supporting Small Island Developing States (SIDS) in adapting to the consequences of climate change consists of investing in the development and establishment of efficient renewable energy-desalination infrastructure. These kinds of investments can not only increase water resilience but also promote a much-needed synergy between these inextricably linked resources (energy and water) whilst strengthening the cooperation between the public utilities.
Today, the majority of the Caribbean’s economy with the exception of T&T is entirely dependent on diesel fuel or natural gas. For decades, residents of Union Island (part of St Vincent and the Grenadines) had to endure excessive noise and air pollution that came with diesel power plants as well as coatings of black soot over homes.
The Caribbean region is ideal for exponential growth in the renewable energy sector. Unfortunately, renewable energy still plays only a minor role in the Caribbean’s energy generation, even thou the region’s conditions are ideal for leveraging green sustainable energy. Sun (solar energy) and wind are abundant, in addition to geothermal energy and hydropower systems with the ability to free all Caribbean islands entirely from fossil fuels. In the Caribbean region, solar power is advantageous not only because of abundant sunlight but also because solar energy systems have seen a tremendous drop in installation prices and ongoing maintenance costs. Mapping water needs with renewable energy sources will be a strategic tool for planning any Caribbean country’s new desalination systems. Renewable energy-powered desalination can be a key enabler for continued growth especially for countries that rely on water for industrial use, agriculture and/or irrigation.
As such, renewable energy generation should be seen by governments and public utilities across the Caribbean as a valuable economic investment that reduces external, social, environmental and operational costs. Government agencies and the private sectors may, therefore, wish to take the evolving market opportunities and long-term impacts of desalination technological options into consideration when planning their capacity, infrastructure, and sustainable water supply demands.
The dominant desalination processes used across the globe today are based on Reverse Osmosis (RO) and Multi-Stage Flash (MSF) which constitute 60.0 per cent and approximately 27 per cent of the worldwide capacity, respectively. The feasibility of each technology depends on specific conditions such as energy prices, water quality and the technical resources of the region. Thermal desalination processes such as Multi-Stage Flash (MSF) involves distillation whereby saline feed-water (typically seawater) is heated to vaporise, causing fresh water to evaporate and leave behind highly saline solutions (the brine). Freshwater is then obtained from vapour cooling and condensation.
Further, membrane desalination incorporates membranes to separate fresh water from saline feed-water. The feed-water is brought to the surface of the membranes, which selectively passes water molecules through and excludes the salts. During Reverse Osmosis (RO), the seawater pressure is increased above the osmotic pressure, thus allowing the desalinated water to pass through semi-permeable membranes, leaving salt particles behind.
Desalination processes such as Reverse Osmosis (RO) or Multi-Stage Flash (MSF) driven by the use of renewable energy (solar, wind, geothermal and hydropower systems) can provide a sustainable way to produce fresh water for some Caribbean regions. It is an economically attractive option as the costs of renewable energy technologies continues to decline and the prices of fossil fuels remain unstable.
Using locally available renewable energy resources for desalination (either Reverse osmosis or Multi-Stage Flash (MSF) processes are highly likely to be a cost-effective solution particularly in Caribbean regions with poor infrastructure for freshwater transmission and distribution. Assessing the technical feasibility and cost effectiveness of renewable desalination plants requires detailed analyses, including a variety of factors, such as location, quality (salinity) of feed-water input and fresh-water output, the available renewable energy source, plant capacity and size, and the availability of grid electricity.
The right combination of a renewable energy source with a specific desalination technology can be the key in matching both power and water demands across the Caribbean region economically, efficiently and in an environmentally friendly way.
Dr Kiran Tota-Maharaj
Head of Civil and Environmental Engineering
Centre for Water, Communities and Resilience(CWCR)
University of the West of England, Bristol (UWE Bristol)