I propose a renewable energy scheme where a tidal lagoon is partitioned into a ‘high’ lagoon and a ‘low’ lagoon by a dividing wall, which houses turbines which continuously generate power as sea water flows from the high lagoon to the low lagoon.
At high tide, the sea-gates of the high lagoon are opened and the high lagoon is filled up to high tide level.
When the ebb tide begins, the sea-gates of the high lagoon are closed and remain closed until the next high tide.
At low tide, the sea-gates of the low lagoon are opened and the low lagoon is emptied to low tide level.
When the flood tide begins, the sea-gates of the low lagoon are closed and remain closed until the next low tide.
The sea-gates are functionally identical to one-way flap valves and may be engineered as such.
The Double Tidal Lagoon Baseload Scheme delivers a genuine baseload generation capability which can’t be delivered by inferior single tidal lagoon schemes as proposed by Tidal Lagoon PLC, as explained in the critical review in Energy Matters, “Swansea Bay Tidal Lagoon and Baseload Tidal Generation in the UK”.
A couple of days after posting this, a comment below was kind enough to provide a reference to David J C MacKay’s “Sustainable Energy – without the hot air”, pages 320/321 – “Getting “always-on” tidal power by using two basins”
“These toppings-up and emptyings could be done either passively through sluices, or …” – David J C MacKay
So MacKay’s “passively through sluices” “two basins” scheme is indeed absolutely equivalent to my double lagoon proposal here.
See also –
- Haishan Tidal Power Plant
- TIDAL BARRAGE POWER PLANTS:TWO-BASIN PROJECTS
- Derby Tidal Power Preliminary Design Report
The Solway Firth
The Solway Firth is the best location for Scottish tidal lagoon plans because that’s where Scotland’s highest tides are.
Almorness Tidal Energy Scheme
The Almorness Tidal Energy Scheme is my outline design concept intended to serve only as an example of possible Double Tidal Lagoon Baseload Schemes. Points to note are
- the River Urr empties into the high lagoon, adding to generation capacity.
- dredging the estuary mud out of the lagoons, especially the low lagoon and around the turbine house would likely be necessary for satisfactory performance
- there should be a drainage canal to redirect water flow to prevent drainage into the low lagoon
- the lagoon walls would obstruct sea-going navigation to the Urr estuary harbour unless a lock for boats was built into the high lagoon sea wall to enable (admittedly delayed) navigation.
Whilst the tides on Scotland’s north-west coast aren’t so high, there do seem to be quite a number of suitable sea-lochs there that could relatively easily be barraged to exploit tidal energy, somewhat in the style of a tidal lagoon but without having to build much in the way of lagoon walls, nature having done most of the work already.