We are getting more and more interested in tide mills. There are a number – but not that many – around the UK coast. They seem to be a way of harvesting tidal power at the local level which is relatively non-intrusive to the environment in comparison with modern (much larger) plans for lagoons and barrages. The ones that do exist are often rather lovely buildings – in lovely locations. There are a number of ‘lost’ tide mills, as far as we can see.

We are tracking down a copy of this 1994 publication.

We have visted a few in the UK.

Tide Mill at Carew, Pembrokeshire. This is an amazing place, a lagoon, mill and house  linked to the spectacular Carew Castle ruins.

A short stretch of the tidal river Carew was engineered to make a lagoon that fills at high tide so the water could be used to drive the mill after. Much more info here. Here are some pictures.

Three Mills / House Mill, River Lea, East London. 

This is an ancient mill site, located near the mouth of the tidal river Lea where it joins the river Thames in East London. House Mill is reported to be the ‘largest tidal mill in the world’. It is not working, but is open to the public. Info here 

Our interest in Tide Mills was spurred greatly by this passage form the book The Moon: considered as a planet, a world, and a satellite, by James Nasmyth and  James Carpenter (1874)

This seems to be a remarkable, early plea to consider tidal power as a source of renewable energy as compared with coal power – which – although abundant and convenient in the late 19th century –  was regarded as not renewable.

The whole book is online here Guttenberg Project

“In the existing state of civilization and prosperity, we do not, however, utilize the power of the tides nearly to the extent of their capabilities. Our coal mines, rich with “the light of other days”—for coal was long ago declared by Stevenson to be “bottled sunshine”—at present furnish us with so abundant a supply of power-generating material that in our eagerness to use it upon all possible occasions we are losing sight, or putting out of mind, many other valuable prime movers, and amongst them that of the rise and fall of the waters, which can be immediately converted into any form of mechanical power by the aid of tide-mills. Such mills may be found in existence here and there, but for the present they are generally out-rivalled by the steam-engine with all its conveniences and adaptabilities; and hence they have not shared the benefits of that inventive ingenuity which has achieved such wonders of mechanical appliance while steam has been in the ascendant. But it must be remembered that in our extravagant use of coal we are drawing from a bank into which nothing is being paid. We are consuming an exhaustive store, and the time must come when it will be needful to look around in quest of “powers that may be.” Then an impetus may be given to the application of the tides to mechanical purposes as a prime mover. [19] For the people of the British Islands the problem would have an especial importance, viewing the extent of our seaboard and the number of our tidal rivers. The source of motion that offers itself is of almost incalculable extent. There is not merely the onward flowing motion of streams to be utilized, but also the lift of water, which, if small in extent, is stupendous in amount; and within certain limits it matters little to the mechanician whether the “foot-pounds” of work placed at his disposal are in the form of a great mass lifted to a small height or a small mass lifted to a great height. There is no reason either why the utilization of the tides should be confined to rivers. The sea-side might well become the circle of manufacturing industry, and the millions of tons of water lifted several feet twice daily on our shores might be converted, even by schemes already proposed, to furnish the prime movement of thousands of factories. And we must not forget how completely modern science has demonstrated the inter-convertibility of all kinds of force, and thus opened the way for the introduction of systems of transporting power that, in such a state of things as we are for the moment considering, might be of immense benefit. Gravity, for instance, can be converted into electricity; and electricity gives us that wonderful power of transmitting force without transmitting (or even moving) matter, which power we use in the telegraph, where we generate a force at one end of a wire and use it to ring bells or deflect needles at the other end, which may be thousands of miles away. What we do with the slight amount of force needful for telegraphy is capable of being done with any greater amount. A tide-mill might convert its mechanical energy by an electro-magnetic engine, and in the form of electricity its force could be conveyed inland by proper wires and there reconverted back to mechanical or moving power. True, there would be a considerable loss of power, but that power would cost nothing for its first production. Another means ready to hand for transporting power is by compressed air, which has already done good service; another is the system so admirably worked out by Sir W. Armstrong, of transmitting water-power through the agency of an “accumulator,” now so generally used at our Docks and elsewhere, for working cranes and such other uses. And as the whole duty of the engineer is to convert the forces of nature, there is a rich field open for his invention, and upon which he may one day have to enter, in adapting the pulling force of the moon to his fellow man’s mechanical wants through the intermediation of the tides.”

[19] About 100 years ago London was supplied with water chiefly by pumps worked by tidal mills at London Bridge.