Hydropower
Hydroelectric power (also known as hydropower or hydro energy) makes up the smallest proportion of the Australian renewable energy sector. However, hydro power provides important stability to electricity networks. Hydroelectric power generates electricity by capturing the energy generated by the natural flow of water. It is easy to ramp up to full power, can be used to store energy for long periods and is readily scalable. Hydropower has extremely low carbon emissions and low water usage when compared with other energy generation technologies. When considering if a location is suitable for hydropowered water treatment, the local geopgraphy and water sources need to be carefully considered.
According to the International Hydropower Association, there are four main types of hydropower: run-of-the-river, storage, pumped storage and offshore.
Run-of-the-river
Run-of-the-river hydro systems (also known as dam-less hydro) capture the energy of natural currents in rivers and streams. The water is removed from the stream to turn a wheel or turbine and then returned to the river. These are the oldest types of hydropower systems with water wheels being used in Ancient Greece to mill grain. Run-of-the-river systems are best in fast flowing rivers with little seasonal variation in streamflow. These systems generally do not include storage but don’t require the same amount of land area as storage based hydro systems.
Microturbines can be use in run-of-the-river systems to generate electricity to run water treatment systems. However, the power generation capability of run-of-the-river systems is generally not sufficient to power extensive treatment systems. The seasonal variability of many run-of-the-river hydro systems means they are unable to provide the consistent power required for water treatment.
Storage and Pumped Storage
Dams are built to store water for a variety of reasons: flood mitigation, rainwater storage, recreational activities and irrigation. Large volumes of water hold significant potential energy and can be released through turbines to generate electrical power. Storage hydro reservoirs make use of local height gradients, the higher the water is stored, the more energy is available. Power can be made from storage hydro on demand so it can be used to smooth electrical supplies. This differs from run-of-the-river systems which vary their power generation seasonally due to changes in rainfall.
Pumped hydro is a variation of storage hydro where excess generated power (e.g. from solar and wind) is used to pump water uphill into a reservoir. This reservoir then acts like a battery and allows for energy to be generated as required. Each 10 m of elevation will provide 1 bar of pressure when released. For low pressure water treatment methods, water can be pumped uphill and then gravitational energy can be used to produce treated water in pressure driven systems. For higher pressures or if local geography does not provide sufficient elevation, electricity can be generated to create hydropowered water treatment systems.
Offshore
There are two types of hydropower that are termed offshore hydro: tidal power and wave power. Tides ultimately come from the gravitational action of the sun and the moon on the Earth’s water. At some locations in the world, the tidal range (the difference between high and low tide) can vary by up to 15 metres. Tidal barrages, which have an efficiency of between 20% to 40%, site turbines at choke points in seawalls through which the water flows as the tides change. The largest tidal power system in the world is Korea’s Sihwa lake tidal power station which produces 254 MW. The mean operating tidal range through the Sihwa seawall is 5.6 m.
Waves are caused either by the action of the wind on the surface of the ocean or generated through seismic activity. Wave energy converters capture the energy of waves using either the oscillating motion or height difference of waves. Wave energy converters can generate sufficient electricity to drive water treatment processes. 200 kW wave energy systems using blowhole designs are currently being tested in Bass Strait. There are also water treatment systems which use seawater pressurised by wave energy to produce drinking water. Of the four types of hydro energy, tidal and wave offer the most flexible solutions for hydropowered water treatment systems. However, each location will have its own optimal renewable energy mix which will include hydro assets.
Moerk Water are experts in determining if local renewable energy assets can be used to produce hydropowered water treatment systems. Contact Moerk Water today to find out more about renewable energy powered water treatment.
