Tuesday, December 5, 2023

Floating and canal top photovoltaic systems: A nexus between food, water and energy


Solar power can be a crucial source of renewable energy. However, large scale installation remains a problem for lack of land availability. How floating solar Photovoltaic system (FPV) or Canal Top Photovoltaic system (CTPV) can solve this problem?

Climate change has started assuming serious proportions from the last century exposing our world to the threats of devastation and destruction. It calls for a multi-dimensional approach to put control on the factors responsible for climate change. A major contributor to climate change is environmental pollution, and energy production and consumption constitute the biggest share of emissions of harmful gases in the environment that lead to global warming and associated climate effects.

The beginning of the current century has seen concerted efforts towards the production of renewable energy to bring down emissions from fossil fuel-based energy production. Solar and wind energy has gained importance in recent times with a fall in production costs. One major challenge for utility-scale solar production is the availability of land. A floating solar Photovoltaic system (FPV) or Canal Top Photovoltaic system (CTPV) can solve this problem and prove to be beneficial in a number of ways.

Wastewater canals, wetlands, lakes etc can be utilized for solar power production. Though construction of floating or canal-top solar panels may involve higher costs compared to the ground-mounted panels studies suggest that they are more efficient in energy production as the water provides a cooling effect on the panels. At the same time, it reduces the loss of water through evaporation and increases water availability in the dry season.

An FPV system utilizes a kind of pontoon with PV panels that float on the water body and are connected to underwater cables, electrical connections and inverter.

Floating solar Photovoltaic Systems (FPV)

An FPV system utilizes a kind of pontoon with PV panels that float on the water body and are connected to underwater cables, electrical connections and inverter. The first FPV began operation in 2007 in Japan. Later on, the FPV system was adopted in many countries like Australia, Brazil, the USA, some European countries like France, Italy and Spain and several Asian nations including China, South Korea, Singapore, Japan and India. India got its first FPV in New Town, Kolkata in West Bengal. The 10KW system that started functioning in 2015 was installed on a lake inside Eco Park in New Town.

Floating Photovoltaic System in New Town, Kolkata. Source: VikramSolar

Subsequently, FPV projects have come up in Kerala (Kayamkulam) and Gujarat (Kawas) and recent projects are also coming up in Telangana and the world’s largest FPV project (600MW) is coming up in Khandwa District of Madhya Pradesh over the Narmada river.

Currently, 8 Indian states have operational canal top solar power projects.

Canal-Top Photovoltaic Systems (CTPV)

Another option of using water bodies for solar power generation is the installation of canal top solar panels by using the canal-spanning infrastructure. Usually, the steel support structure is used on both sides of the canal so that solar panels can span the width of the canal. The world’s first canal top commercial solar PV project was installed in Chandrasan in Gujarat in 2014. This has an installed capacity of 1MW stretching a distance of 750m. Currently, 8 Indian states have operational canal top solar power projects.

photovoltaic system
Canal Top Power Project: Vadodara Branch Canal, Gujarat. Source: “Experimental validation of performance and degradation study of the canal-top photovoltaic system”, Manish Kumar and Arun Kumar, Applied Energy, Elsevier, 2019.

The co-benefits: Water-Energy-Food nexus

To attain the target of increasing renewable energy mix in the total energy usage around the world utility-scale solar installations are imperative. But large scale installations require large tracts of land which is difficult to come by especially in developing countries where land is scarce. Moreover, converting land for solar installations lead to deforestation, reduction of land area available for agriculture, erosion and degradation of land. In this scenario, FPV and CTPV provide a solution to the land availability problem. In addition to this, it has other benefits such as:

  1. Construction of FPV/CTPV system on waste water canals/basins can lead to various remunerative utilization of the canals and reduce costs borne by municipal bodies in removing phytoplankton and water plants.
  2. FPV/CTPV tends to reduce surface evaporation from water bodies due to the shading effect, reducing hardships and costs associated with water scarcity during the dry season in arid and semi-arid areas. This also has a gender dimension as it reduces the time devoted by womenfolk in arid areas in fetching water from distant places as the source of water in their locality dries up. So the government can provide incentives for setting up of FPV/CTPVs in semi-arid regions.
  3. Construction of FPV on wetlands can ensure their preservation as maintaining wetlands become remunerative. Where wetlands are used for pisciculture, FPV installation can be helpful not only in maintaining the water level by preventing evaporation it can also provide electricity for running oxygen recharge pumps to control oxygen level in water required for growth of fish population.
  4. Lack of sunlight on that part of the water body where PV system is installed prevents algal bloom. This in turn reduces the chances of clogging of water pumps and toxicity of water.
  5. The installation of CTPV on irrigation canals reduces the energy demand of grid connected pumpsets.
  6. When waste water/water from wetlands or fisheries is used for irrigating agricultural land, water availability may increase leading to higher productivity, in dry season as well. So CTPV installations will be beneficial especially for the states which primarily depend on canal irrigation.
  7. It also has potential for creating investment and employment opportunities in production and installation of panels as well as for their regular maintenance and cleaning.

Possible limitations of the PV systems

There are some drawbacks of these two PV systems in terms of the higher cost of installation, lower efficiency and faster degradation. As revealed in a study by Manish Kumar, S S Chandel and Arun Kumar titled “Performance analysis of a 10 MWp utility-scale grid-connected canal top photovoltaic power plant under Indian climatic conditions” published in the journal Energy, in 2020, the performance of CTPV is lower than the land mounted PV systems due to high humidity created by evaporation of water from the canal and absorption of solar radiation by the water molecules.

In addition to that, the modules tend to degrade faster due to moisture ingression into the modules. Performance can be improved by cooling and cleaning the modules with canal water but this, in turn, damages the semiconductor material. This calls for technological modifications in the modules to make them suitable for installation on water bodies without loss of efficiency. Their study has confirmed that the installation of solar PV on water bodies can reduce the loss of water through evaporation to a significant extent.

On the other hand, a study by M. N. Sairam and A. Aravindhan in their paper titled “Canal top solar panels: A unique nexus of energy, water, and land”, published in the Materials Today: Proceedings, 2020 reveals that CTPV systems with reflectors and inter-array spacing between modules have lower cost and higher efficiency than a land-based PV system.

Implications for future policy

With near about 10,000 kilometres of canal length in India, even if half of that is utilized for solar power generation it can save thousands of acres of land providing roundabout 10GW of power. Even if some studies may suggest that FPV or CTPV have lower performance, faster degradation rate and higher costs compared to the land-based system its wide range of co-benefits seems to have impacts on various strata of society like the farmers and fishermen as well as for people who may find employment in this sector if wide-scale dissemination is adopted.

Whether this is a desirable policy still needs to be explored. There is a dearth of a comprehensive study that includes the socio-economic-environmental costs and benefits of the FPV and CTPV systems.

Given the multidimensional aspect of PV systems installed on water bodies that include their effect on the ecosystem, water conservation, agri-irrigation, pisciculture, employment generation and also the environmental impacts of both clean energy and future disposal of the panels (with an approximate lifespan of 25 years) a multicriteria and multiobjective optimization analysis that includes life cycle analysis of the PV systems can reveal the true costs and benefits to the society, economy and environment and whether the benefits exceed the costs making it an acceptable strategy or the other way round suggesting modifications before wide-scale adoption of the FPV/CTPV systems.

Also Read: Solar energy: Your rooftop can be the first step to a clean environment

(Debalina Saha is faculty of Economics, Centre for Excellence in Public Management (Civil Services Study Centre), Administrative Training Institute, Kolkata.)

(Disclaimer: The views expressed in the article above are those of the authors’ and do not necessarily represent or reflect the views of Autofintechs.com. Unless otherwise noted, the author is writing in his/her personal capacity. They are not intended and should not be thought to represent official ideas, attitudes, or policies of any agency or institution.)


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