Hybridization of Hydropower Plants With Floating PV: Design and Optimization

Solar power is by many seen as one of the great solutions to satisfy an increasing need for power while at the same time mitigating climate change. A booming international market with exponential growth underpins this promise, but the growth in some markets is starting to encounter barriers. Although solar power is cheap and fast to build, it cannot supply power between sunset and sunrise and must then be combined with other power sources or storage. One such power source is hydro power. Hydro power is very often combined with a reservoir which can provide storage but, in periods with little rain, even hydro power must reduce its output. Combining hydro power and solar power in a hybrid power plant can mitigate seasonal and daily constraints that both technologies face individually in order to provide a continuous power output throughout the day and year. Hybridization can further overcome two other barriers that the expansive solar power growth is facing, namely the need for land as well as access to grid. By utilizing floating solar power on an existing hydro power reservoir, one can avoid conflicts regarding land use, while utilizing the same grid connection, implying improved infrastructure utilization and reduced investment cost. However, solar power output can change within seconds as clouds pass. In order not to cause any challenge for the grid, this must be compensated for by the hydro power. There is hardly any knowledge nor experience about the combined regulation of hydro power and solar power in a hybrid systems. This Ph.D. project will investigate how this can be done in an optimum way. Furthermore, the project will seek to classify different types of hydro power plants according to their suitability for hybridization with solar power, as well as suggest design principles for green-field hybrid systems. Optimal operation and long term planning will also be investigated in order to remove perceived technical risks from potential investors.

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Modern societies are nowadays aiming to an increasing use of renewable energy sources. With more and more installed capacity of non-dispatchable power generation, like wind and solar PV, the future of power systems is likely to be built upon distributed hybrid solutions. Hydropower is generally considered as one of the cheapest and most reliable renewable energy sources, but its implementation often implies important environmental and social impacts, and water management is becoming a matter of increasing importance in some locations. Solar PV has become cheaper, more accessible, and easier to implement. Among other constraints, the significant land requirements hinder countries with limited suitable land to develop large-scale systems. Floating PV (FPV) is an emerging option for water points, ponds, lakes and reservoirs, with several advantages. In addition to unlocking new surfaces for PV power production, FPV generally allows: (i) the deployment of PV plants on existing reservoirs that saves land space as well as land acquisition costs; (ii) better performance of the PV modules due to the cooling effect of the water; (iii) limited evaporation of the water, and (iv) improved water quality for fresh water supply. FPV has also many advantages when combined with hydropower plants, including: (i) deployment of PV plants close to hydropower projects (often built on hilly/mountainous locations); (ii) electrical infrastructure and grid connection already existing; (iii) dry seasons with less water flow correspond to period of high solar irradiation; (iv) FPV can support day-time peak load so that more hydropower is reserved for evening peaks; (v) FPV can facilitate maintaining a higher head for the hydropower, and (vi) instantaneous irradiation variability can be largely compensated by the fast-responding hydro turbines. In turn, this can reduce the system spinning reserve in the grid, thus lowering overall operation cost.