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Energy

Renewable energy has long been known as a greener alternative to fossil fuels, but that doesn’t mean that the former has no negative environmental impacts. Hydropower, for instance, has been known to reduce biodiversity in the land used for its systems.

Now, a team of Norwegian-based researchers have developed a methodology that quantifies the environmental effects of hydropower electricity production.

UllaFrre

Ulla-Førre – Norway’s largest hydropower station.

Martin Dorber, PhD candidate in Industrial Ecology at the Norwegian University of Science and Technology (NTNU), is part of the team that developed the analytic tool. ‘Some hydropower reservoirs may look natural at first. However, they are human-influenced and if land has been flooded for their creation, this may impact terrestrial ecosystems,’ he said,

The Life Cycle Assessment, or LCA, can be used by industry and policymakers to identify the trade-offs associated with current and future hydropower projects. Norway is one of the top hydropower producers in the world, with 95% of its domestic electricity production coming from hydropower.

 Hoover Dam station

Generations inside the Hoover Dam station. Image: Richard Martin/Flickr

Many hydropower facilities include a dam –  many purpose-built for hydropower generation – which stores fresh water from lakes or rivers in a reservoir.

Reducing biodiversity in the areas where hydropower development is being considered is one of the main disadvantages of the renewable source. Reduced freshwater habitats and water quality, and land flooding are among the damaging effects – all of which are difficult to assess, says the team.

‘Land use and land use change is a key issue, as it is one of the biggest drivers of biodiversity loss, because it leads to loss and degradation of habitat for many species,’ said Dorber.

 Hydropower development

Hydropower development can be damaging to freshwater habitats. Image: Pexels

Using reservoir surface area data from the Norwegian Water Resources and Water Resources Directorate and satellite images from the NASA-USGS Global Land Survey, the team were able to create a life cycle inventory that showed the amount of land needed to produce a kilowatt-hour of electricity.

‘By dividing the inundated land area with the annual electricity production of each hydropower reservoir, we calculated site-specific net land occupation values for the life cycle inventory,’ said Dorber.

‘While it’s beyond the scope of this work, our approach is a crucial step towards quantifying impacts of hydropower electricity production on biodiversity for life cycle analysis.’

While this study is exclusive to hydropower reservoirs in Norway, the team believe this analysis could be adopted by other nations looking to extend their hydropower development and assess the potential consequences.

Pumped-storage hydropower. Video: Statkraft

‘We have shown that remote sensing data can be used to quantify the land use change caused by hydropower reservoirs,’ said Dorber. ‘At the same time our results show that the land use change differs between hydropower reservoirs.’

‘More reservoir-specific land use change assessment is a key component that is needed to quantify the potential environmental impacts.’

Energy

Compared with other renewable energy resources – take solar or wind power as examples – tidal energy is still in the first stages of commercial development. But as the world moves towards a greener economy, tidal power is becoming more in demand in the competitive renewables market.

Currently, the very few tidal power plants in the world are based in Canada, China, France, Russia, South Korea, and the UK, although more are in development. Experts predict that tidal power has the potential to generate 700TWh annually, which is almost a third of the UK’s total energy consumption.


How does it work?

Tidal energy is produced by the natural movement of ocean waves during the rise and fall of tides throughout the day. Generally, generating tidal energy is easier in regions with a higher tidal range – the difference between high tide, when the water level has risen, and low tide, when levels have fallen. These levels are influenced by the moon’s gravitational pull.

 The moons gravitational pull

The moon’s gravitational pull is responsible for the rise and fall of tides. Image: Public Domain Pictures

We are able to produce energy from this process using tidal power generators. These generators work similarly to wind turbines by drawing energy from the currents of water, and are either completely or partially submerged in water.

One advantage of tidal power generators is that water is denser than air, meaning that an individual tidal turbine can generate more power than a wind turbine, even at low currents. Tides are also predictable, with researchers arguing that it is tidal power is potentially a more reliable renewable energy source.

What is tidal power and how does it work? Video: Student Energy

There are three types of tidal energy systems: barrages, tidal streams, and tidal lagoons. Tidal barrages are structured similar to dams and generate power from river or bay tides. They are the oldest form of tidal power generation, dating back to the 1960s.

However, there is a common concern that generators and barrages can damage the environment, despite producing green energy. By creating facilities to generate energy, tidal power centres can affect the surrounding areas, leading to problems with land use and natural habitats.

 Fleet tidal lagoon in Dorset

Fleet tidal lagoon in Dorset, UK. Image: Geograph

Since then, technologies in tidal streams and lagoons have appeared, which work in the same fashion as barrages but have the advantage of being able to be built into the natural coastline – reducing the environmental impact often caused by the construction of barrages and generators.

However, there are no current large-scale projects with these two systems, and output is expected to be low, presenting a challenge to compete with more cost-effective renewable technologies.