The long read: PV in the water-energy-food nexus

From pv magazine 01/2021

The field of energy economics is the middle of a major transformation. Fatih Birol, general secretary of the International Energy Agency, has dubbed solar “the king of electricity,” and solar is now cheaper than fossil fuels in many regions. With the economics now seemingly addressed by solar technology and PV business development, attention is now drawn to the next hurdle. With only 10 years to shift the basis of the global economy toward 2050 climate targets, the question now is how to accelerate the deployment of renewable energy into the system at scale.

According to Harry Boyd-Carpenter, head of energy EMEA at the European Bank for Reconstruction and Development (EBRD), the best way to do this is through sector coupling. “By doing that we solve multiple problems at once – that is the future of solar,” says Boyd-Carpenter. But that requires an understanding of where solar PV can have the most impact.

One area where this can be seen most clearly is within the water-energy-food nexus (WEF). There are cross-sectoral impacts and necessary trade-offs to be considered, in terms of resource use and carbon footprints – especially between sectors that have not traditionally coordinated their approaches. While concerns about system interconnection, resilience, and flexibility have been in the background for a while, developments in 2020 – combined with the impact of the pandemic – have transformed the market’s understanding of their importance.

Water resources

IRENA’s joint analysis with the World Resource Institute and China Water Risk focused on India and China. It found that deploying solar PV and wind in line with climate commitments would contribute to drastically reducing the water-intensity of power generation and reduce pressures on freshwater sources. The integration of renewable energy in the agricultural supply chain would also have a positive impact, where land is used for farming and solar generation combined, or solar PV provides local power for maintenance and management.

“All in all, integrating renewable energy solutions in the agri-food and water supply chains can greatly bolster water and energy security, decrease cost volatility, reduce greenhouse gas emissions and contribute to long-term food sustainability,” says Gurbuz Gonul, the director of IRENA’s Country Engagement and Partnerships Division.

With many regions facing increasing uncertainty about rainfall patterns, water treatment is a growing focus for municipalities around the world, especially where the lower cost of renewable energy can significantly cut power-processing costs. Mike Bammel, national head of renewable energy at Jones Lang LaSalle’s valuation advisory business, says that there are a range of approaches being used in the United States that address this. Such water processing systems using solar include municipalities using PV farms to pump water and power equipment to cut or offset the electricity cost of wastewater processing. This lowers costs for municipalities and enables the reallocation of tax revenues while maintaining services.

Development PV

Solar has a vital development role to play as well. In Senegal, solar PV is being used to pump water for municipalities, and it can be used hyper-locally to pump for drinking or for irrigation. In Tunisia, under the Small Cities Sanitation program, wastewater is treated to create water for irrigation and waste sludge is used for fertiliser. In Morocco, Spanish utility Abengoa is building a desalination plant in Abudeja and is using renewable energy to power its processes.

“The vast improvements in affordability and reliability of solar PV makes it a highly viable solution for providing clean energy for a variety of uses within the Water–Energy–Food nexus … including water pumping for irrigation, desalination, heating and cooling for food processing and storage,” says Gonul.

MENA applications

Such PV applications are especially important in the MENA region, where there is heavy reliance on fossil fuels, even though 30 million people remain without access to electricity. The region is highly vulnerable to the impacts of climate change and water and food security are a challenge.

The EBRD has been looking at circular economy models to meet this challenge. Sue Barrett, EBRD’s head of infrastructure for the Middle East and Africa, points out that what drives interest in WEF approaches is a financial incentive, whether that is compensation for a grid connection, an obligation as part of a new business opportunity, or an opportunity to reduce input costs. And it’s the role of solar PV in reducing input costs that could be transformational, particularly in the water sector.

Powering desalination

Electricity demand and scale is always an issue in cost-effective PV deployment, and it is in looking at the role of solar in desalination where the greatest opportunity may lie. As Boyd-Carpenter points out, electricity is a key input cost for desalination and those countries with the greatest need for desalination are often those with the highest amounts of insolation. In the MENA region, for example, installed PV costs have sunk below $0.02/kWh in some very large tendered projects.

The United Arab Emirates, which recently increased its commitment to cutting emissions by a quarter by 2030, is working on combining action on food security, water and energy in harmony. In the UAE, only 5% of the land is arable and there is very little potable water. Groundwater provides just over 50% of the UAE’s water supply, and desalination provides 37%, with around 12% being reclaimed water used for irrigation. The trade-off here is that around one-third of Abu Dhabi’s carbon footprint now comes from the production of water and electricity.

Wastewater treatment of surface water is energy intensive, while it can be five times more energy intensive to manage non-surface water. According to Masdar, seawater desalination in the UAE requires 10 times more energy than surface freshwater production, and its cost is projected to increase by 300% as water demand increases by 30% to 2030.

Increased desalination increases energy demand, but if you can manage solar PV intermittency, the whole process will be cheaper, while insulating developers and investors from the global trend toward a carbon price. It also provides absolute stability on the power price (when the power is generated onsite or agreed through a power purchase agreement).

Given that during 2020, the oil price has fluctuated between minus $40 and $140, the hedge against price volatility would seem to be a sufficient driver for solar PV in itself. But there is another opportunity here, and that is to look at water as a storage vector.

Traditional approaches for solar PV generation are to store excess electricity in lithium-ion batteries, molten salts, or even electrolyze for hydrogen for use in unelectrified sectors. Combine with desalination, however, and there is two-fold result – desalination and the flexibility of water storage. This, as Boyd-Carpenter points out, provides a storage of value not just of electricity, as the resultant use can be dependent on market needs at any given time.

Dolf Gielen, the director for technology and innovation at IRENA, agrees. “Solar-water desalination projects are being developed and deployed in Saudi Arabia and the UAE,” he explains. “It is cheaper to store water than to store electricity, so the variability is less of an issue.”

The challenge with desalination is that it often needs to happen at a large scale, and historically it has been an energy hog with significant energy, carbon and pollution footprints. The pollution footprint is complex, consisting of a combination of processing chemicals and left-over brine which, if left untreated, can have a devastating effect on local ecosystems. A 2019 report found desalination plants produce an average 1.5 litres of brine for every liter of fresh water.

New tech

The majority of desalination plants today use reverse osmosis (RO), which bring problems of brine water disposal, high energy requirements, and high capital costs. In the MENA region, with more than 60% of the world’s desalinated water capacity, this has the potential to be highly problematic. The challenge has driven significant research, with the Ghantoot water desalination pilot program in Abu Dhabi assessing over 20 different water technologies from around the world.

One technology seeing increasing focus is solar thermal desalination, which is where solar PV has a significant role to play. According to a recent report from Frost & Sullivan, such solar thermal approaches “have a far lower carbon footprint, are potentially more cost-effective, and can be scaled relatively more effectively.” These technologies include both direct use (to produce distillate directly in the solar collector), or indirect use. Indirect use could see the combining of conventional desalination techniques, such as multistage flash desalination (MSF), vapor compression (VC), reverse osmosis (RO), membrane distillation (MD) and electrodialysis, with solar collectors for heat generation.

William Janssen, chief executive of Desolenator, agrees that recently there has been a shift in perspective. Desolenator focuses on energy harvesting and desalination at the same point using a thermal distillation process, with the company’s PVT harvesting both heat and light for electricity, increasing its efficiency. “What the sun provides us with is heat and light – the logical choice is to use a thermal process,” Janssen says.

The distillation process used by Desolenator means that it can treat a range of contaminants in water – not simply seawater treatment. That means application not only coastal communities with access to seawater, but communities with access to polluted waters or saline lakes, from miners in Chile to disenfranchised communities in India.

Currently, Desolenator is working on a couple of projects on the ground, including an installation in the Sundarbans delta near Calcutta and one in Dubai. The Indian project is sponsored by beer brewer Carlsberg, as part of its strategy to address its water consumption and conserve shared water.

The Desolenator model is modular, so it can be scaled up from today’s 250-cubic- meter-per-day plants, which can provide water for up to 10,000 people a day. While the current model works effectively off-grid, Janssen says that the company can also “instantly link to the microgrid – if we connect, we can absorb excess power” by integrating the plant in as an energy storage opportunity.

The real differentiator of the Desolenator process is the cost. “The key to the cost of water production is the levelized cost of water,” Janssen says, noting that this is a concept that is familiar to the PV industry. “The new LCOW is low because the plant comes with energy built in – that’s the solar opportunity.”

By Felicia Jackson

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