Once thought of in a niche sense, the solar-water nexus is a rapidly expanding network of applications. They include practical tools capable of solving persistent issues like water scarcity, as well as newly pressing issues like overcoming the water challenge of green hydrogen production.

From pv magazine 01/2022

In December 2021, The New York Times described it as “A Slow-Motion Climate Disaster: The Spread of Barren Land.” Across the world, from Brazil to northern China, and from the American Southwest to North Africa, desertification is a creeping catastrophe impacting more than half a billion people. However, with the search for scarce water – an increasingly harsh reality – the solar-water nexus is proving an especially practical relationship.

But perhaps what is most striking about the raft of off-grid solar-water solutions in remote areas is the distinct lack of battery energy storage systems (BESS). While the cost of BESS has decreased dramatically in recent years, remote communities, particularly in developing countries, can still find the costs prohibitive, the lifetimes short, the inconsistency debilitating, and the maintenance difficult. After all, water is a necessity for survival and systems which provide it must be robust and dependable for long periods of time.

Desalination station

In the western Sool region of Somaliland, the town of Ainabo/Caynabo has long been home to the Aynaba Well, one of the most famous wells in an arid country where wells are celebrated by poets. But severe drought has been putting heightened pressure on this storied water source, and in May 2021, the government of Somalia declared its drought situation a national emergency. The dependence of the Aynaba Well means that people’s source of drinking water is also the source for agricultural irrigation and local wildlife, and as a result it has become more brackish and less potable.

Enter Italian-headquartered company Genius Watter, a subsidiary of US-Canadian solar module manufacturer Silfab. Genius Watter’s “zero battery” solar water desalination solution won a United Nations Development Program (UNDP)tender last year for a minigrid and drinking water project in Caynabo set for commissioning this month. With the help of its partner, Uganda-based renewable energy company Aptech Africa, Genius Watter’s solution is a 41kWp minigrid and high-efficiency reverse osmosis plant capable of supplying 30,000L of desalinated drinking water each day from brackish wells.

The project needs to deliver fully automatic clean and affordable water to 15,000 people for at least 30 years, requiring only minor maintenance. Thanks to the plant’s 90% harvest rate on available PV net power the solution doesn’t require batteries. Genius Watter CEO Dario Traverso told pv magazine zero battery solutions were preferred because batteries remain expensive in this market and they also have a short lifespan compared to solar.

“Instead of storing energy we store water, either by gravity, as demonstrated in one of our projects in Kenya, in which we pump the water uphill when the sun is high, or in storage tanks,” Traverso said. “If unavoidable, small batteries for pumps can be used, but it’s far less expensive than incorporating a full energy storage system.”

The key to making these types of desalination solutions affordable is trying to get the least salty water possible. “It is much smarter to find ground-water than seawater, much less capex/opex and better ROI,” said Traverso. He noted that if you desalinate 100 liters of seawater, you’ll use more energy and end up with 40 liters of clean water and 60 liters of brine, while 100 liters of brackish water uses much less energy and returns 70 liters of clean water. In both circumstances, the brine can be dumped at sea without environmental damage, or used for applications like fish farming.

Not so boring

Genius Watter uses drones with electromagnetic signalling to find ground watersources, but on the archipelago of Zanzibar, Tanzania, the problem isn’t finding water (they have over 400 bore holes). The problem is generating the energy to pump the water, treat it and then distribute it.

Currently, the Zanzibar Water Authority (ZAWA) uses diesel generators to pump the often quite brackish water through rundown pipes at a cost of over $200,000 a month. The expense drove a delegation from ZAWA to the Off-Grid Expo and Conference in Augsburg, Germany, in December 2021, to announce its ambition to overhaul and extend its water service by making it 100% solar powered.

ZAWA Director General Salha Mohammed Kassim said that currently only 36% of Zanzibar’s households are water connected. Zanzibar is home to 1.7 million people and Kassim understands that “we have a long way to go to get to 100%, but for this reason we are looking to off-grid solar.”

The idea is to use off-grid solar systems to operate the water pumps used at bore holes, as well as the treatment reservoirs and the distribution network. Not only will off-grid solar be able to achieve this, but it will also allow ZAWA to save on the cost of the current system, savings which could be used to upgrade and expand the water network. “We need to cut those costs and make our islands more sustainable,” Kassim said. “We need to be a role model for water solutions.”

Tourist trap

Like many tropical settings, Zanzibar’s tourism sector brings a lot of money into the economy, but tourism is also a thirsty industry. One of the companies ZAWA invited to Zanzibar was Genius Watter, which has experience in solar solutions for the tourist industry in Cape Verde. Key to these projects, said Traverso, is providing an integrated solar and water solution, meaning not just electricity, but drinking water, hot and cold showers, water for air conditioning systems, freezers and kitchens.

To achieve this level of efficiency with just solar panels and thermal storage for hot water, requires smart management and an efficient use of space including canopy structures and bifacial modules. “A number of small things add up to make a big difference in the end,” Traverso said.

What this water-solar solution was able to achieve for the King Fisher Village, which now advertises itself as the first eco-boutique hotel in Cape Verde, was a reduction in operating costs of 85% and a significant improvement in the quality of water. The 72kWp solar plant (with plans for an extension up to 130kWp) provides 100% of the energy for desalination and 80% of the resort’s other electricity needs.

Thirsty industry

Perhaps what is most encouraging about the solar-water nexus is its extraordinary potential at both ends of the economic spectrum. Solar-powered desalination can be affordable in drought-ridden Somalia, and also supply the water needed for large industry and green hydrogen production.

Recent analysis by McKinsey & Company shows that companies with water-intensive operations can reduce their risk by switching to renewables. From analysis of 1,500 companies in the chemicals and food-and-beverage processing industries, it found that a considerable amount of the energy purchases came in countries with low renewables uptake and high levels of water stress, resulting in disproportionate impacts for water and emissions. The analysis showed that a 50% increase in renewables purchasing, would provide a 60% reduction in water consumption in both sectors.

Not only is this significant for existing industries, but also for the emerging green hydrogen industry, as the best solar resources tend to be in regions of water scarcity. Therefore, being able to get the requisite water needed for electrolysis sustainably and without impacting local reserves makes sense. That’s what Spanish PV project developer Gransolar is planning to do at the port of Almería in Southern Spain. A company spokesperson told pv magazine that it is in the permitting stage of a project that will produce hydrogen from seawater through 30MW solar, 20MWh of energy storage, and a PEM electrolyzer with a 20MW capacity. But the project requires a boost from the European Commission’s Recover and Resilience Facility if it is to be operational by 2025. For coastal projects the “sea is an inexhaustible source of water that will require desalination plants to generate green H2,” the spokesperson said.

In Chile, US company Oceanus Power & Water (OPW) is planning a 200MW Integrated Pumped Hydro Reverse Osmosis Clean Energy System (IPHROCES) with a 100 MLD desalination plant powered by solar and wind energy to deliver energy storage and desalinated water services. OPW CEO Neal Aronson said the project is currently completing feasibility studies and will submit its environmental impact statement in 2022.

In a decade-long drought, Chile is facing the challenge of water scarcity. But Aronson said the IPHROCES project would be able to “deliver fresh water for human consumption and a HV transmission line to interconnect the project to the regional substation.” The dual function of the solution is becoming more attractive, Aronson continued, as the negative effects of climate change accelerate. “Our solution can help provide water and energy resilience, as long as we can find approximately 400m of elevation within a few kilometers of the coast.”

Aronson added that this type of project is ideal for green hydrogen production as well as numerous other industrial and farming applications if the cost and location stack up. But the best market case for the technology is long-term storage, Oceanus South American President Joan Leal said that is exactly what Chile needs.

Water from air

In Australia, the Northern Territory government has given “Major Project Status” to “water-from-air” technology company Aqua Aerem’s $10.7 billion 10GW Desert Bloom Hydrogen project which has commercial ambitions by 2023. According to CEO Gerard Reiter, the project uses solar energy to power a system which absorbs water from air in arid climates, water which can then be used for the production of green hydrogen below $2/kg.

Atmospheric water capture is not new technology, but Aqua Aerem’s patented system extracts water with solar energy. “Water is critical to generating hydrogen,” said Reiter. “We have managed to overcome the water supply and solar/electrolysis integration problems that have held back global renewable hydrogen production.”

The atmospheric water extraction system and hydrogen generation units are contained in multiple modular and portable solar-powered Hydrogen Production Units (HPUs) capable of generating “water, heat, electricity, and hydrogen, meaning each is a set of containerized solutions that can operate independently.” This independence garners versatility as well, and outside of green hydrogen Aqua Aerem sees potential applicability in mining and agriculture, as well as the alleviation of water scarcity.

Unlike desalination, Reiter says the advantages of generating water from air means no grid connection is required, there’s no brine to dispose of, it has fewer inefficiencies and fewer ongoing costs. Considering the water challenge is one of the biggest barriers to green hydrogen production in water-stressed regions with the best renewable resources, this technology could prove a breakthrough.

Water-energy-food nexus

The importance of the water-energy nexus is increasing thanks to applications in hydrogen production and industries like mining. But as shown by projects in some of the world’s most drought-stricken regions, perhaps the most prescient applications are found in the nexus of water, energy and food. The Water and Energy for Food Grand Challenge (WE4F) from the Southern and Central Africa Regional Innovation Hub (S/CA RIH) has opened its first call for innovations in the water-energy-food nexus space – innovations which can help smallholder farmers cultivate their crops sustainably. One such innovation would be Genius Watter’s featured solar desalination microgrid solution. CEO Dario Traverso told pv magazine that in just six to eight months on the island of Boa Vista in Cape Verde, it has brought farmers back to agricultural lands previously destroyed by the use of highly saline brackish water, “and more are coming back still, and female farmers, too.” The WE4F Challenge will support up to 30 organizations working on sustainable water or energy solutions for climate-resilient agriculture, with grants of up to $200,000 and winners to be announced in May 2022.

The Aynaba Well is one of the most famous in Somaliland, but severe drought has driven overdependence on this increasingly brackish water source by a growing number of people and animals.