What Are The 3 Types Of Energy Using Water?

The 3 main types of energy that utilize water are hydroelectric power, tidal power, and wave power. Hydroelectric power harnesses the energy from moving water, usually in the form of rivers or waterfalls, in order to generate electricity. Tidal power captures the energy from the rise and fall of ocean tides and converts it into electricity. Wave power utilizes the kinetic energy from ocean surface waves and converts it into electrical power. In this article, we will explore each of these 3 types of renewable energy in more detail, examining how they work, their efficiency, environmental impacts, prominent projects, costs, and future outlook.

Hydroelectric Power

Hydroelectric power generates electricity by using flowing water to spin turbines connected to generators. There are two main types of hydroelectric systems: dam-based and run-of-river.

In dam-based systems, dams are built to store water in reservoirs. When the water is released from the reservoir, it flows through tunnels and channels into the turbines. As the water spins the turbine blades, a shaft connected to the turbine spins a generator to produce electricity. Some of the electricity generated is used to power the dam’s operations, while the rest is distributed on transmission lines to homes, businesses, and industries (1).

Run-of-river systems do not require dams or water storage reservoirs. Instead, some of the natural flow of a river is diverted through a canal or channel into turbines. Run-of-river systems generate electricity from the kinetic energy of the flowing water, while allowing the rest of the river to flow freely. This makes run-of-river systems less environmentally disruptive than dam-based hydro, but electricity output depends on seasonal water flows (2).

Hydroelectric power provides around 7% of total U.S. electricity generation. It is a renewable energy source that does not directly produce air pollution or carbon emissions. However, large dam-based hydro projects can significantly impact local ecosystems and communities (1).

(1) https://www.eia.gov/energyexplained/hydropower/

(2) https://www.usgs.gov/special-topics/water-science-school/science/hydroelectric-power-how-it-works

Tidal Power

Tidal power harnesses the energy from the natural rise and fall of tides to generate electricity. As tides ebb and flow, they create a massive amount of kinetic energy that can be captured and converted. There are two main types of tidal power technologies:

Tidal barrages utilize a dam-like structure called a barrage to trap water at high tide. When the tide goes out, the water flows through turbines in the barrage to generate electricity. Barrages essentially create an artificial tidal reservoir, where the energy difference between high and low tides is exploited (National Geographic, 2022).

Tidal stream generators are underwater turbines that harness the kinetic energy of tidal currents. They work similarly to wind turbines, with the push and pull of the tides causing the blades to spin. Tidal stream generators can be built into the seabed or floated on structures above (Wikipedia, 2022).

The Sihwa Lake Tidal Power Station in South Korea is currently the largest tidal power station in operation at 254 MW capacity. Tidal power stations only generate electricity for around 10 hours per day on average, during the peak tidal flows. Overall tidal energy has historically played a minor role in electricity generation globally compared to other renewables, but holds potential for further growth and development (EIA, 2019).

Sources:

National Geographic. (2022). Tidal energy. https://www.nationalgeographic.org/encyclopedia/tidal-energy/

Wikipedia. (2022). Tidal power. https://en.wikipedia.org/wiki/Tidal_power

EIA. (2019). Tidal power. https://www.eia.gov/energyexplained/hydropower/tidal-power.php

Wave Power

Wave power devices capture the kinetic energy of ocean surface waves and convert it into electricity. As waves travel and gain height, they store energy. Wave energy increases with the height of the wave and speed of the wind. The most common wave power technologies are point absorber buoys that float on the ocean surface. They absorb the energy of waves and use it to drive electromechanical or hydraulic converters that produce electricity.

Point absorber buoys consist of floating structures with components that move relative to each other due to wave motion. This motion drives electromechanical or hydraulic power take-off systems to produce electricity. One type uses the vertical motion of the buoy to drive an electromechanical generator. Another approach uses the up-and-down motion to pump high-pressure oil through a hydraulic motor, which drives an electrical generator. Point absorbers can operate individually or be connected to form an array.

There are also oscillating water column devices that use wave motion against an air chamber to force air through a turbine to generate power. Another approach is an oscillating wave surge converter, which extracts energy from the horizontal motion of waves. These technologies can be installed along shorelines, near the ocean surface, or completely submerged.

According to an analysis, wave power could potentially provide about 1,170 terawatt-hours per year in the United States, or the equivalent of 20% of America’s electricity generation. However, wave power is still an emerging technology and further development is needed to improve efficiency and withstand harsh ocean conditions.

Efficiency Comparison

When comparing the efficiency of hydroelectric, tidal and wave power, an important metric is the capacity factor. The capacity factor measures the average power generated divided by the rated peak power.

Hydroelectric power typically has a high capacity factor of around 40-60%, meaning plants generate around 40-60% of their maximum rated power on average over a year (Source). This is because the flow of river water used to generate electricity is relatively consistent.

Tidal power can have capacity factors from 20-40%. The capacity factor is lower than hydroelectric because tides are intermittent – power output varies over daily and monthly cycles. However, the predictability of tides means tidal plants can schedule generation to match peak demand periods (Source).

Wave power typically has the lowest capacity factor of around 20-30%. Wave energy can fluctuate a lot depending on weather conditions. Making wave power less predictable and reducing efficiency compared to tidal and hydro power (Source).

Environmental Impacts

While hydroelectric power and tidal power have the potential to provide clean renewable energy, they can also have negative environmental impacts if not properly managed. Some of the main environmental considerations include:

Hydroelectric power dams and reservoirs may disrupt ecosystems and wildlife habitats, as large areas of land are flooded. Fish migration routes can be blocked, and sediment flow downstream interrupted (National Geographic). However, impacts can be mitigated through fish ladders and sediment control.

Tidal power turbines pose collision risks for marine life, as the rotating blades could injure or kill fish, marine mammals, and seabirds. The turbines also generate noise that could disrupt animal behaviors (NSEnergyBusiness). Careful site selection and impact monitoring can help minimize risks.

On the positive side, tidal power is renewable and emits no greenhouse gases during operation. Large scale development could help reduce reliance on fossil fuels. Wave power has minimal aesthetic or land use impacts since installations are offshore (Tocardo).

Overall, while hydropower and tidal energy can have environmental tradeoffs, careful planning and mitigation strategies can help maximize sustainability and minimize ecosystem disruption.

Prominent Projects

Some of the largest and most advanced tidal power facilities in the world include:

• The Sihwa Lake Tidal Power Station in South Korea is currently the largest tidal power installation in the world, with a total power generation capacity of 254 MW. It operates using seawater turbines and began commercial operation in 2011 (https://www.nsenergybusiness.com/features/worlds-biggest-tidal-power-plants/).
• The La Rance Tidal Power Plant in France was the first major commercial tidal power station. Commissioned in 1966, it has a capacity of 240 MW and continues to generate clean energy by harnessing the tidal currents of the Rance River (https://www.power-technology.com/features/featuretidal-giants-the-worlds-five-biggest-tidal-power-plants-4211218/).
• The MeyGen Tidal Energy Project in Scotland is the world’s largest tidal stream array, with four 1.5 MW turbines installed. It has plans to expand to 398 MW and provide power to 175,000 homes (https://www.power-technology.com/features/featuretidal-giants-the-worlds-five-biggest-tidal-power-plants-4211218/).

Some major hydroelectric facilities include:

• The Three Gorges Dam in China is the world’s largest hydroelectric power station, with a massive capacity of 22,500 MW.
• The Itaipu Dam on the Brazil/Paraguay border is the second largest hydro plant, generating 14,000 MW.
• The Guri Dam in Venezuela produces 10,200 MW from its hydroelectric station.

Key wave energy projects include:

• The Agucadoura Wave Farm off the coast of Portugal was the world’s first commercial-scale wave energy farm, before it was decommissioned.
• The CETO 6 Unit near Garden Island in Australia is a unique wave energy system that uses submerged buoys tethered to seabed pumps.

Cost Comparison

When comparing the costs of hydroelectric, tidal and wave power, there are several factors that need to be considered.

Hydroelectric power is the most mature and established technology of the three. According to the U.S. Energy Information Administration, the average levelized cost of hydroelectric power in 2020 was $42 per megawatt-hour (MWh) [1]. This makes it one of the cheapest sources of renewable energy.

Tidal power is still an emerging technology, so costs are higher than traditional hydroelectric. One estimate puts the levelized cost of tidal power between $0.17 to $0.35 per kWh [2]. The large range accounts for differences in project size and location.

Wave power is the least mature renewable electricity technology. Cost estimates range from $0.20 to $0.35 per kWh [3]. The variability is due to technology uncertainty and project specifics.

In general, hydroelectric power is the cheapest of the three, followed by tidal and then wave power. However, there is significant overlap in the cost ranges. All three technologies have potential for cost reductions as they develop and scale up.

Future Outlook

The future potential for growth in hydroelectric, tidal, and wave power is significant. According to the U.S. Department of Energy, hydropower currently provides about 7% of total U.S. electricity generation and has the potential to grow by over 50 gigawatts in the next decade. Globally, wave and tidal energy could provide up to 10% of the world’s electricity needs by 2050.

However, all three technologies face challenges. New large-scale hydroelectric projects often face scrutiny over environmental impacts on rivers and wildlife habitats. There are also concerns that climate change could negatively impact precipitation patterns and water supplies needed for hydropower. Wave and tidal projects are still working to become cost-competitive with other renewable energy sources. New technologies and economies of scale could help reduce costs over time. Both wave and tidal energy are still working to prove their long-term viability and reliability before seeing major growth.

Overall, the renewable nature and large untapped potential of hydropower, tidal, and wave energy means they will likely play an increasing role in the global energy mix. But realizing their full growth potential will require addressing environmental concerns, policy support, technology improvements, and cost reductions.

Conclusion

There are three main types of energy that utilize water – hydroelectric power, tidal power, and wave power. Each has its own advantages and disadvantages in terms of efficiency, environmental impact, and cost.

Hydroelectric power is the most prevalent, accounting for over 16% of global electricity generation. It relies on the potential energy of elevated water, typically in a dam, that is allowed to fall through turbines to generate electricity. While efficient and reliable, hydroelectric dams can disrupt river ecosystems.

Tidal power harnesses the kinetic energy of tidal flows using turbines underwater. Despite high predictability, tidal power suffers from high upfront infrastructure costs. There are only a handful of major tidal power plants operating globally.

Wave power uses the motion of ocean surface waves to drive electric generators. While it has a huge potential capacity, the technology is still in its infancy and substantial research is underway. There are no commercial-scale wave power plants yet.

Overall, hydropower is the most mature water energy technology today, but tidal and wave power offer promising potential down the line as renewable energy solutions.