Hydroelectric Power

Image: Unsplash. “Photo by Dan Meyers on Unsplash.” Unsplash.com, 11 June 2019, unsplash.com/photos/aerial-photography-of-body-of-water-w6X7XaolqA0. Accessed 21 Nov. 2023.

Power Considerations

Some of the most important considerations include flow rate, water depth, drainage area, and yearly precipitation. Flow rate measures the volume of water that flows through the river for a given duration of time (measured in cubic feet per second), and water depth measures how deep the water is (in feet). Drainage area is the area through which the water flows (in square miles) and yearly precipitation is how much it rains each year within a region (in inches).

When evaluating municipalities with hydroelectric potential, in-stream hydroelectric turbines were prioritized as a viable hydropower source. In-stream (run-of-the-river) turbines are generally a clean, efficient, and sustainable method to generate electricity; their utility is underscored by the fact that they can be installed in a variety of locations since they do not require the construction of additional edifices like dams1. Although they do not require large dams, smaller dams or weirs to guide the flow of water are beneficial, as the lack of a water reserve creates power variations between 40 to 80% of the plant’s potential to produce energy2.

Flow Rate & Water Depth

Flow rate is useful for estimating the energy potential of rivers by their kinetic energy, which can be converted to electrical energy, whereas water depth is important for evaluating the size of turbines that can be used. These can also be used together to find what the best hydroelectric power source for a given region is.

Drainage Area & Yearly Precipitation

Drainage area and yearly precipitation are important in union for gauging the consistency of the water source, such as how much water will fall into the river. Precipitation trends become an evermore important factor to consider as global warming renders certain regions, like Puerto Rico, more susceptible to extreme rain conditions3.

Application

While in-stream turbines are suitable for many locations, Puerto Rico’s variability of landscape means these turbines may not be the best for all cases. In areas with lower flow rates, turbines that utilize changes in elevation (impoundment, diversion, pumped-storage) may prove more effective than those that rely on quicker speeds like in-stream turbines4. Regular maintenance of all turbines, such as cleaning them and applying special coatings to the turbine blades will protect them from corrosion, but further steps and modifications may be required to protect them from harsher conditions5.

Energy Storage for Hydroelectric Power Plants

Unlike solar and wind, we’ve analyzed a different type of ESS that we find effective for hydroelectric power in Puerto Rico: hydro pumping. Pumped Hydropower is a very common ESS, accounting for around 93% of energy storage in use to date6.

The system requires two water reservoirs: one of lower elevation and another of higher elevation. In order to generate electricity, water flows from the upper reservoir to the lower reservoir, passing through turbines that rotate generators which produce electrical energy. The excess potential energy (the extra water) then flows into the lower reservoir, where it is kept until electricity demand decreases. When the demand lowers, the turbines rotate in the opposite direction to pump water up into the upper reservoir, which then can be used again to generate electricity. The ability to repeat the process makes pumped hydropower very desirable as a way of storing and generating hydroelectric power6.

Applying it to Puerto Rico

It is critical to note that very few areas in Puerto Rico can utilize pumped hydropower. Sufficient climate conditions for hydroelectric power systems are quite hard to find —particularly in the mountains. We’ve found that on the entire island, there are only seven potential locations for implementation (being locations with adequate amounts of water). In these areas, we’ve found that implementing this system may be a challenge as Puerto Rico has low elevation variation at reservoir locations, which will cause the cost of implementing pumped hydropower much more expensive than in other locations7.

References
  1.  “Run-of-River Hydropower.” Run-of-River Hydropower | Climate Technology Centre & Network |Tue, 11/08/2016, www.ctc-n.org/technologies/run-river-hydropower. Accessed 28 Nov. 2023. and   “Run-of-the-River Hydroelectricity.” Run-of-the-River Hydroelectricity – Energy Education, energyeducation.ca/encyclopedia/Run-of-the-river_hydroelectricity. Accessed 28 Nov. 2023. 
  2.  “Run of River Power – Energy BC.” Energybc.ca, 2017, energybc.ca/runofriver.html
  3. Masters, Jeff. “Warming Climate Makes Extreme Hurricane Rains More Likely for Puerto Rico» Yale Climate Connections.” Yale Climate Connections, 23 Sept. 2022, yaleclimateconnections.org/2022/09/warming-climate-makes-extreme-hurricane-rains-more-likely-for-puerto-rico/.
  4. Kamran, Muhammad. “Hydro Energy.” Renewable Energy Conversion Systems, Academic Press, 21 May 2021, www.sciencedirect.com/science/article/abs/pii/B9780128235386000075?via%3Dihub. 
  5. Gummer, John H. “Combating Silt Erosion in Hydraulic Turbines.” Renewable Energy World, 2023 Clarion Events North America, 1 Mar. 2009, www.renewableenergyworld.com/baseload/hydropower/combating-silt-erosion-in-hydraulic-turbines/#gref.
  6. “How Pumped Storage Hydropower Works.” Energy.gov, 2016, www.energy.gov/eere/water/how-pumped-storage-hydropower-works. Accessed 21 Nov. 2023.
  7. Closed-Loop Pumped Storage Hydropower Resource Assessment for the United States Final Report on HydroWIRES Project D1: Improving Hydropower and PSH Representations in Capacity Expansion Models. 2022.