Mitigating Climate Change Impacts on the Existing Hydropower Dams in Iran
Iran’s water shortage is a well-known phenomenon, with a range of causes and effects, including climate change impacts and prolonged heat and droughts, with mismanagement of water resources at the top of the list. A prime example of this mismanagement is the extensive construction of dams, including hydropower. This piece will reflect on how an emerging concept in solar energy, known as floating solar farms, could mitigate the impacts of climate change on water resources by reducing evaporation from the dams’ reservoirs and significantly contribute to the generation of clean electricity. Deploying this technology not only conserves water but the additional clean electricity added to the country’s energy portfolio could compensate for the need for building new hydropower dams in Iran. The technology of floating solar farms is novel yet technically relatively simple to be deployed across different water reservoirs, particularly hydropower dams in Iran. However, any investment in this technology that could help Iran in addressing water shortage, generate electricity, and reduce its carbon emissions need to be financially viable for the investors through creating market-competitive conditions by the government and long-term consistency and reliability of policies. These are conditions that are highly unlikely to be met under the current economic uncertainty that the government faces.
Introduction
Iran’s scarce water resources has undergone major crises in recent decades, due to increasing population size, expansion of agriculture, and above all, mismanagement of resources. While climate change and reduced annual precipitations are not the main causes of the water shortage in Iran, they certainly play an important role in exacerbating this situation. One of the controversial topics within the context of water management in Iran is the extensive construction of dams, often deemed unnecessary with negative impacts on the surrounding ecosystem. This piece will reflect on how we can mitigate climate change on electricity generation and the overall performance of hydropower dams by deploying emerging technology in solar energy known as floating photovoltaics through producing clean electricity, benefiting from existing infrastructures and reducing water evaporation.
Why hydropower dams are important
According to the International Energy Agency (IEA), hydropower is expected to remain the world’s largest resource of renewable electricity, and it will continue to play a crucial role in the decarbonization of the energy system. It’s estimated that hydropower produced about 16% of the total global electricity in 2018. The hydropower potential is affected by the hydrological regime, a function of regional climate patterns that would vary as climate changes. Changes in precipitation, evaporation, and runoff as a result of climate change affect the variability and volume of stream flow. For arid and semi-arid climates, like Iran, the impact of climate change would be more severe, and the increased annual average temperature in addition to prolonged, more frequent, and severe heatwaves and droughts, would put more stress on the available water resources. These conditions accelerate evaporation from the dam reservoirs, leading to reduced hydropower potential. The water behind the dams could also decrease to a level that is below the minimum water at which turbines can produce hydroelectric power.
The total hydropower installed capacity in Iran is more than 12 GW, as of 2019, according to the International Hydropower Association (IHA). Hydropower provides 1% of the total primary energy source in Iran. Nevertheless, it’s the largest and only on-demand renewable resource by generation capacity. Hydropower plays a crucial role in the country’s water management by forming vast lakes behind the dams that, in some cases, are several kilometers long. While the same concept is valid for all types of dams, hydropower dams play a more significant role based on their scale and size.. As a result, hundreds of square kilometers of water surface are directly exposed to sunlight across the country, leading to evaporation and loss of millions of cubic meters of water accumulated behind the dams. Considering the climate of Iran and having more than 300 clean, sunny days every year, this water loss will only get worse in the coming years.
What are floating solar farms, and how can they mitigate the challenges that hydropower dams face in Iran?
Floating Photovoltaics (FPVs), or floating solar, is an array or combined arrays of photovoltaic (PV) panels placed on a floating structure that keep them above the water surface. This innovative application of PV technology can be deployed on the water surface from very small to large scales, and they can provide a clean, cost-effective, and reliable source of clean energy. They are flexible and adaptable with various bodies of water that allow deploying them on different types of water bodies, including drinking water reservoirs. A research by the US National Renewable Energy Lab (NREL) indicates that if the engineered reservoirs facing limited environmental problems in the US are covered by floating solar farms, they could generate up to 10% of the US annual electricity needs, showing the great potential of this technology even under conservative estimates.
Retrofitting hydroelectric dams with floating solar technology will increase the output of these systems and add clean solar energy, benefitting from existing grid connections and maintenance personnel. Placing PV panels on the water surface reduces the floating solar operating system, prevents overheating of the PV panels, and improves the energy yield. This integration will increase the capacity of the dams to meet the energy needs during the peak hours, particularly in dry seasons.
In Iran, the variability of water levels behind dams is significant during different seasons. This change will be accelerated because of climate change and prolonged droughts. It’s worth noting that water reservoirs provide a clean environment and reduce the presence of dust settled on the panels and therefore the maintenance costs. The world’s first combined FPV and hydroelectric system were grid-connected in 2016 as an installation of 220 kW FPV on Portugal’s Rabagão Dam in Portugal. A study by Sulaeman and colleagues in 2021 published in Renewable and Sustainable Energy Reviews evaluates integrating FPVs in hydropower dams in Brazil. The authors show that these systems could enhance the existing power sources and be considered as an alternative approach toward meeting the energy demand growth without building new dams.
The figure shown here illustrates how floating solar farms could be placed on a dam reservoir. In this image, Amir Kabir Dam near Tehran has been used for the purpose of this illustration.
FPVs also play a significant role in reducing water evaporation from the water bodies that they cover, which is crucial for increasing the resilience of cities in such climates, particularly during droughts. This feature allows Iran to incorporate more renewables into its energy mix, reduce greenhouse gas emissions, and decrease water evaporation. The air temperature, heat flux, mass transfer in the water surface, and wind speed are the most critical factors determining the reservoir’s evaporation rate. The extent of the evaporation reduction is directly affected by the FPV design (e.g., the shape and size of the floatssupporting the PV modules and island, the ratio of the covered surface to the reservoir surface area, etc.)
Any approach that mitigate water evaporation contributes to saving Iran’s scarce water resource; overing above water canals is among them. A study by McKuin and colleagues published in 2021, discusses the canal-top PV installations in California. The article shows that such a system could reduce annual evaporation by an average of 39 ± 12 thousand cubic meter per km of canal.
In a recent study published by Freshetehpour and colleagues in 2021 studied the potential of deploying floating solar farms on five important reservoirs dams in Iran; the selected dams wereDoosti, Aras, Karkheh, Doroudzan and Shahid Kazemi. The study aimed to calculate potential clean energy generation through deploying FPVs’ systems on these dams’ reservoirs and also saving water through mitigating evaporation. Among the selected reservoirs, the maximum annual water evaporation yearly is estimated to be about 2700 mm that belongs to Karkheh and minimum of about 1700 mm, which belongs to Aras dam reservoir. Of course, these numbers have seasonal variability, nevertheless reflect the significance of water loss due to the evaporation in Iran. The above mentioned study by Freshetehpour et al., 2021, also suggests that covering one square km of the reservoirs’ surface for the selected dams could generate between 194-257 GWh of clean electricity every year, which corresponds to the electricity needs of approximately 90,000 Iranians annually. With respect to the saving water and reducing evaporation if 10% of the selected lakes are covered, they could collectively save close to 71 MCM of water per year. Of course, these numbers are mostly theoretical calculations, nevertheless, they clearly reflect the potential of floating solar farms in mitigating the climate change impacts on hydropower dams in Iran.
Apart from saving water, producing clean energy by FPVs is a key factor in water management in Iran as it compensates for the need of building new hydropower dams, which is a costly and lengthy process, with potentially significant negative environmental impacts. Apart from the hydropower dams’ reservoirs this approach could be deployed on all types of reservoirs even small-scale agricultural pools to save water and produce clean energy. It’s worth noting that because of the emerging nature of floating solar farms there are some uncertainties and unknowns on the impacts of covering the water surface on marine ecosystem, nevertheless considering the scale of the dam reservoir surface and the climate of Iran, such impacts will be negligible.
Challenges of deploying floating photovoltaics solar farms in Iran
In terms of technology and engineering aspects, deploying FPVs on inland waters is not a major challenge. Also, various types of FPVs are now available globally provided by different manufacturers that could contribute to generating electricity and saving water in Iran. However, the main challenge is the investment in this emerging solar energy concept. If the private investors decide to invest in FPVs they need to make sure that the government provided feed in tariff is market competitive. In other words, the guarantee of payment associated with the energy produced over a guaranteed period of time is financially attractive enough for the investors. In addition to that, consistency of the policies and regulations is crucial for investors in floating solar farms. The investors need to be assured that during the lifetime of the project, often considered 25 years, they have access to their assets and investments and are in full control of the project e.g., maintenance. Ambiguities on who owns the water rights and lack of regulations that partly stem from the novelty of this technology adds to the problem. In the current economic situation of Iran, the government is the most viable option for investing in floating solar farms to mitigate some of water management challenges that the country faces, nevertheless, the overwhelming extent of issues that it faces makes it highly unlikely to consider water management a priority. __________________________________
Hamid Pouran is an interdisciplinary scientist and engineer. He is a chartered scientist, chartered environmentalist and a Member of the Royal Society of Chemistry. He is also a senior member of IEEE and chair of IEEE UK & Ireland Climate Change and Environmental Technology group. He is the principal editor of the 2019 book: Environmental Challenges in the MENA Region: The Long Road from Conflict to Cooperation and the proposal writer and scientific consultant for a BBC World TV science documentary, called Dust Storm that had significant contributions from NASA, USGS and Barcelona Supercomputing Center. The documentary was aired by BBC World, BBC Four and Deutsche Welle in different languages. He is currently the program director of MSc Sustainability and Climate Change at the University of Wolverhampton in the UK.
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