Our upcoming energy report will identify the options for increasing renewable energy generation within the Exeter region. In this Energy Explainers blog we will be breaking down the technology that generates hydroelectric power, and considering how it can help us to achieve the goal of energy independence.

Like sunlight and wind, water is something that is all around us which can be used to generate power. Power generated from water is called hydroelectric power, but how do we turn flowing water into flowing electricity?


Exeter City Futures Hydroelectricity Cricklepit Mill


Water was important for generating power in Exeter in the past, turning the waterwheels of its mills, and can be used to generate electric power in its future. Join us for a dip in the mechanics of how hydroelectric power works.


Flowing Energy

Hydroelectricity works in a similar way to wind power. Water flows through a system and turns a turbine which drives a generator and creates electricity. This is just like wind power where wind spins a blade, which also drives a generator.

Any body of water that flows with enough force to turn a turbine can generate hydroelectric power. The necessary amount of force is created by building up a ‘head’ of water, this means constructing something like a dam or reservoir where water can collect before being fed through a narrow pipe.

Inside the pipe there’s a generator connected to a shaft with rotating blades at the end. Water flowing past the blades, turns the generator and creates electricity.


Energy Explainers what is hydroelectricity


Hydroelectric generators can vary in size ranging from enormous structures like the Hoover Dam, to small turbines placed in rivers. Hydroelectric generation is on the increase. Not only is it the source of 99% of Norway’s electricity, but the world’s largest power stations are hydroelectric. The Three Gorges complex in China produces 22,000MW and is five times larger than the Hoover Dam.


Back to the Future at Cricklepit Mill

Cricklepit is Exeter’s last remaining mill and the headquarters of Devon Wildlife Trust. It’s also a great example of hydroelectricity in action within the Exeter region.




In 2010 Devon Wildlife Trust undertook the installation of a hydro turbine on its historic mill leat, an artificial stream used to power waterwheels. It was built using funding and support from the EDF Energy Green Fund, Big Lottery Fund and Renewable Energy for Devon.

The leat was fitted with state of the art automatic sluice gates that control the flow of water. The gates detect and maintain the changing water levels, and build up an artificial head of water to power the system. When the water is fed through to the turbine it passes through what is called a “penstock” tube. The tube narrows as it reaches the turbine increasing the force of the water.

The Hydro turbine is capable of providing between 15 – 25% of all the electricity we require to run our Headquarters. This means that in what we regard “good conditions” – plenty of consistent rain – up to a quarter of all our electricity is clean and not reliant on fossil fuels. We do however accept that our definition of good weather is not shared by most! On a number of occasions we go one better and can export up to 30kwh per day to the grid meaning that we have generated more than we use, further reducing the need for energy from power stations.

Stuart Hodgkiss, Facilities Team Leader, Devon Wildlife Trust


Devon Wildlife Trust is a charity which cares for Devon’s wildlife and wild places so keeping fish safe is a top priority. Any fish in the leat are diverted from the penstock tube through a fish bypass tube. The generator isn’t just good for fish either with the foaming pool of water that has passed through the generator proving to be something of an “otter Jacuzzi”.

Anyone who wants to see the generator in action can visit Cricklepit Mill for free Monday to Friday from 9am to 5pm.


You can find out more about the Exeter Region’s hydroelectric potential in the upcoming energy report which will be available through our Insights page. It will provide a detailed analysis of how wind power can be generated in the region, in addition to other forms of renewable energy, and offer key recommendations for becoming energy independent.