Floating solar power in Brazil provides opportunity for hydroelectric power plants

From pv magazine Latam

The installation of floating solar plants in reservoirs may be an opportunity to increase the efficiency and use of hydroelectric power plant infrastructure already in operation as an alternative to the repowering of power plants, according to a report by consulting and energy analysis company PSR.

With the growing participation of solar and wind sources in the Brazilian electricity matrix, hydroelectric power — which continues to be the main source of generation in the country, with about 50% of installed capacity (103 GW of large hydroelectric plants and 5.8 GW of SHPs) — provides stability to the operation of the system.

Many of the hydroelectric plants installed in Brazil are more than 40 years old: 44 GW were in operation at the end of 1984, according to data from Aneel's Generation Information System, and 59 GW in 1994. There is therefore great potential to modernize or even replace existing turbines. A 2019 study by Empresa de Pesquisa Energética estimated the technical possibility of 11 GW of additional installed capacity without the need to expand hydroelectricity by repowering plants, taking into account eligible plants that have been in operation for more than 25 years.

In the May edition of its Monthly Energy Report, the consulting firm PSR suggests comparing these repowering opportunities with the installation of floating solar power plants on hydroelectric reservoirs, noting that both options face limitations and challenges.

Estimating floating solar potential on reservoirs

The Itaipu hydroelectric power plant alone, which began operation in 1984, could nearly double its generation capacity by installing a floating solar plant on 10% of the surface area of its reservoir, which is 1,350 square kilometers in area, according to the estimate released by PSR. The power output of the floating system in this proportion would be 13,500 MW; the hydroelectric plant has 14,000 MW of installed capacity.

The estimate considers 1.4 MWp of direct current power from the floating solar panels per hectare of occupied area, or 1 MW of alternating current per hectare, after transformation by inverters.

Another example cited in the Energy Report is the case of the Furnas hydroelectric power plant. The consultancy integrated public data from ONS into its Hydroelectric Performance Scorecard and identified that since 2006, when the scorecard was launched, the plant's average annual energy has never reached its physical energy guarantee, also known as firm energy (garantia física).

The plant's average production has been 488 average megawatts (aMW) since 1999, according to ONS data, about 16% less than its firm energy. For the plant to reach an average output 15% above its energy guarantee, an additional 180 aMW would be needed. PSR estimated that it would be necessary to install about 1 GW of floating solar to achieve this result, which would occupy an area of 10 square kilometers or 0.7% of Furnas Lake, considering a ratio of 5.5 between the power of the floating solar system (MWac) and its average output (aMW).

Challenges of solar-hydro hybridization

This estimate considers that floating solar power would compensate for low hydroelectric production due to low rainfall or other uses of water resources, such as irrigation. However, the challenges of water unavailability have been less frequent, while hydropower plants face a lack of demand caused, for example, by the prioritization of the dispatch of solar and wind sources over hydropower.

In other words, it would still be necessary to study the real time operation of the hybrid plant, considering the hourly operation to know how the transmission grid is used, the value of the energy that might not be generated (curtailment), the consequences for the operation of the plant, among other aspects.

In addition, PSR points out, the hybridization of hydroelectric plants collides with the restrictions imposed by the Brazilian Electricity Regulatory Agency's (ANEEL) Resolution 954/2021, which allows the installation of solar in reservoirs, but segments the production of the sources and limits possible gains in firm energy and incentives for the installation of floating technology in plants.

According to the consultancy, it does not make much sense to restrict the combination of energy between sources.

Hybridization with solar is also seen as an opportunity in the wind sector, with big players such as Casa dos Ventos and Statkraft betting on the combination.

Irrigation channels

Floating solar energy can also generate benefits for bodies of water other than hydroelectric reservoirs. Some countries are installing solar plants in irrigation canals to reduce losses in drier and hotter areas. Energy Report notes that although ground-mounted solar systems are cheaper than those installed on irrigation canals, a study by researchers at the University of California indicated that projects on canals would have a better financial result, taking into account the water conservation, increasing electricity production and reducing land costs.

PSR suggests that the recent drop in technology costs would justify a reassessment of the possibility of installing solar systems on irrigation canals in the Northeast or even on the large infrastructure of canals and reservoirs that make up the São Francisco River Integration Project ( PISF).

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