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The word “Hydro” is derived from the ancient Greek word meaning water and we know that humans have been using water as a source for energy for over 4,000 years. The Egyptians used water wheels to grind grain and 2,000 years later we can see that water power was being widely used in India, China and Greece as well as throughout the Roman Empire. But it was only in the 19th century, that it became possible to harness the power of water to convert it into electricity and therefore Hydroelectric became a reality.

As awareness of climate change became more widely recognised and accepted, the ways in which we generate electricity and power have come under much more scrutiny with regards to the level of pollutants they emit into the atmosphere. The replacement of fossil fuels has become a major issue across the developing world and alternative, renewable fuels are replacing fossil fuels, backed in many instances by government legislation. New diesel and petrol fuelled car sales will end in the UK in 2030 and coal fired power stations will be phased out in the UK by 2025.

When renewable energy sources are discussed, much of the attention has centred on wind or solar energy and replacing our internal combustion driven vehicles with electric ones. Rarely is hydroelectric one of the topics of conversation, despite the fact that both in terms of electricity and power generation, hydroelectric is the third most commonly used source of power. In rough percentage terms for overall energy generation the main fuels are;

Oil – 33%, Coal – 27%, Gas – 24%, Hydro – 6.5% and Nuclear – 4.5%.

In electricity generation only;

Coal – 36.5%, Gas – 23.5%, Hydro - 16%, Wind – 5.5% and Solar – 3%

China is the largest producer of hydroelectric generation, despite its heavy use of coal fired power stations. Other top users of hydropower generation around the world include the United States, Brazil, Canada, India, and Russia. Over 70% of all renewable electricity generated worldwide is from hydro power.

Gas is burned in a gas fired power station, this produces hot air that drives the turbine and produces electricity. The burning of gas emits carbon dioxide and other greenhouse gases into the atmosphere. When coal is burned in a coal fired power station, the steam that is created powers turbines that then create electricity. As with gas, burning the coal emits carbon dioxide and other greenhouse gases into the atmosphere. Hydropower plants create energy by using the force of water to turn the turbines, nothing is burned, no gases are produced and nothing is released into the atmosphere.

The amount of electricity a hydro station generates is governed by the use of sluice gates or valves which can be opened to increase the flow through the turbines and in doing so, increase the amount of electricity generated, or closed to cut down on power generation. This gives a great deal of flexibility allowing for the generation of electricity to be tailored to the demand at different times of day or during different seasons of the year when demand for electricity obviously change.

There are three main types of hydropower generation schemes;

Storage hydropower

This is a large scale system which requires a dam to be built across a river to form a large reservoir to store water. Electricity is produced by releasing water from the reservoir through a turbine or turbines, which will actuate a generator, thus producing electricity. Storage hydropower provides base load as well as the flexibility to cope with changes in demand at short notice. The storage capacity in the reservoir will allow the installation to operate independently of rainfall in the area for weeks or months.

As with any major disruptive infrastructure project, hydroelectric dams and attendant reservoirs have their problems. They are extremely expensive and disruptive to build, even by comparison to a nuclear power station.

It is not unknown for a reservoir formed by a hydroelectric dam to become a home for a selection of leisure facilities such as sailing, canoeing and water skiing to make use of the expanse of water. Other activities such as walking, running or cycling often crop up as paths and tracks are developed either around or close to the facility.

Because the flow of water can be adjusted, it is not unknown for the flow to be linked to the needs of the downstream farming community to ensure adequate irrigation at certain critical times of year for crop growth.

Run-of-river hydropower

This diverts flowing water from a river through a side channel. The water spins a turbine to generate electricity. A typical run-of-river installation is unlikely to have any storage facility, but provides a continuous base load supply of electricity, with a certain amount of flexibility of operation to cater for fluctuations in demand at certain times of day or as the seasons change. A run-of-river scheme does not need a large reservoir of water so has much less impact on the surrounding countryside

Pumped storage hydropower: provides peak-load supply by cycling water between a lower and upper reservoir using pumps powered by surplus energy from the system which has been generated at times of low demand. When electricity demand increases, water is released back to the lower reservoir through turbines which generate electricity.

The initial investment required in building a hydroelectric facility is high but once built and in operation, hydro is probably the least expensive way of generating electricity. There are relatively few moving parts involved making for minimal maintenance and the water used to “fuel” the facility is a natural resource with no real cost attached to it. Last but not least, hydroelectricity is generated in our own country. It is not generated elsewhere and imported, nor can it be used as a political lever against us by unfriendly regimes.

Although some will highlight the positive effect that a man-made lake would have on local wildlife, with the water being used to enhance the local fish population and offer homes to other aquatic species, other will take the opposite view, objecting to any planned development on the basis that it will decimate the local wildlife and prevent migrating fish such as salmon, from getting to and returning from their spawning areas. There is an argument for both points of view, although fish ladders can be designed into any development which would allow access to migrating fish.

A new man-made reservoir could also see a number of people being required to be relocated as rising water levels would destroy their homes. It is almost certain that the most difficult part of developing further hydroelectric schemes in the UK would be that of getting planning permission to build the facility. Environmentalists would condemn the project because of its effect on wildlife and local residents would also no doubt object to the development. These objections could see any proposed hydroelectric development, especially a large scale storage scheme, locked in red tape for years.

The problem is that we do need to replace fossil fuelled power stations and we need to start soon or we will not reach the targets set by governments across the world and hydroelectric offers an almost emission free alternative to coal and gas