In Bideford, we are conscious every day of the movement of the tide. Here on the edge of the Bristol Channel, the river Torridge enjoys one of the largest tidal ranges in the world. Tidal range is the difference in height between low and high tide. The only place with a larger tidal range is the Bay of Fundy, Canada. 

It can be frustrating for harbour users only to have sufficient depth of water for vessels at high tide but it’s not surprising that from early times there’s been a great interest into how to harness this water movement. Early maps and records show that there was a tidal mill at Instow. In Bideford, Mill Street is said to be named after a mill but unfortunately, the precise location is lost to history and so is the source of energy used to power it. 

Some readers may remember a scheme, proposed in the late 1970s, to create a barrage across the Bristol Channel. It would have powered generators for electricity production as the tide came in. The water retained behind the barrage would then have turned the turbines on the way out. More recently, there have been many other technologies developed for floating and fixed tidal generators. Much of the experimental work, especially that exploiting fast tidal flows off the Scottish coast, has taken place far from centres of population where electricity is needed.

This week, near the steps on the south end of Bideford Quay, a white cylinder has been set in place just above low water. LPD, a Barnstaple based company, (lpdcleanenergy.com) is developing a novel engineering method to harness tidal energy. When the tide rises it compresses the air in the cylinder and this trapped, compressed air can be used to turn a generator. When the tide falls, a vacuum is created in the cylinder and, as a consequence, air is pulled into the cylinder, once again powering a generator. 

The test rig in the harbour won’t be producing electricity. This is part of the product development programme testing the pressures achieved in real life tidal cycles. The rig will stay in place for a couple of weeks to complete the test programme. Is this a modern tidal mill capable of producing clean energy and making the most of our natural tidal range advantage? We will follow the experiment with interest. 

MT