Bell Labs was perhaps the most important centre of technical innovation of the twentieth century. From transistors to solar panels, the list of world changing innovations that came out of the labs is incredible.
For years, Mervyn Kelly was the President of Bell Labs, and he had a simple criteria for judging the merit of a new innovation or invention, it had to be “better, or cheaper, or both”.
And when it comes to low carbon energy, we can probably rephrase it as follows:
BETTER, CHEAPER, SCALABLE, OR ALL THREE
These three criteria are critical for evaluating any low carbon source of energy.
Offshore wind is better than onshore wind in many key respects. Higher load factors and less visual impact may make it preferable despite being more expensive. At high latitudes, solar power is not scalable unless there are miraculous improvements in energy storage, something many solar advocates simply gloss over. Nuclear power plants provide reliable round the clock electricity irrespective of whether the sun has gone down or whether the wind is blowing. Biomass for heating is much less convenient than a gas furnace. And so on.
Which brings me to the announcement today that Britain might build the world’s first tidal lagoon.
So, let’s go through my three criteria, and see how tidal power in Britain stacks up.
Is it better?
This is a complex question. First, tidal lagoons provide reliable – depending on how you define reliable – electricity. Tides can be predicted with high accuracy years in advance. However, the power output will inevitably go close to zero on a regular basis. This can be predicted with much higher accuracy than either wind or solar.
The capacity factor of the first proposed lagoon in Swansea however is relatively low. A total capacity of 320 MW is to expected to have an annual output of 495,000 MWh. This equates to a capacity factor of only 18%, much lower than existing onshore wind (27% on average in Britain) and offshore wind (~35% in Britain).
How about power density? Wind farms take up a lot of space. How much does this tidal lagoon take up?
The tidal lagoon covers approximately 11 square kilometres. This gives us a power density of approximately 5 W/m2. Wind farms in Britain have power density of approximately 2.5 W/m2. In other words if you covered the lagoon in wind turbines you would generate half as much energy, assuming the area is typical of the rest of Britain.
So, the lagoon will take up less space than a wind farm. But it still takes up a lot of space. Power density of energy consumption in Britain is just over 1 W/m2. This lagoon is clearly not going to be a source of high concentration energy.
Unless you hate wind farms or nuclear power plants, it’s hard to see how this lagoon is better from a technical view point.
Is it cheaper?
The BBC reports that the first lagoon “wants £168 per MWh hour for electricity in Swansea, reducing to £90-£95 per MWh for power from a second, more efficient lagoon in Cardiff”.
In other words, the first lagoon will be more expensive than any existing source of low carbon electricity. The second one might offer up prices comparable to nuclear and onshore wind, but will be cheaper than offshore wind. So, it looks as if we will have to build a bunch of them, and with luck the last couple will be cheaper than nuclear or onshore win.
It doesn’t sound like it ticks the cheaper box.
Is it scalable?
The answer here seems to be a clear no. On a global level, tidal potential is less than 1 TW. This compares with global energy energy consumption which is the equivalent of 15 TW, a figure that is certain to keep rising.
However, this 1 TW figure more or less assumes all available tidal energy is extracted. This clearly won’t happen. A more realistic estimate is less than 100 GW, a figure given in a PR leaflet by Alstom – you can rely on PR leaflets to give you credible upper estimates. And that’s 100 GW of capacity, which would equate to less than 50 GW of average output. This would further equate to a mere 0.5% of global primary energy demand.
This is nothing more than a rounding error in global energy consumption.
So it’s very difficult to see what merits there are in Britain investing in tidal power. If it was demonstrably cheaper than alternatives then things would be different. If it pays for itself then we don’t need to worry about it scaling up. But clearly tidal doesn’t pay for itself and it doesn’t scale up on a global level, and the global level is where it really matters.
Money that could be spent on tidal could be spent on offshore wind, next generation nuclear, or other low carbon technologies. The innovation that results from this could have further knock on effects by making the technologies cheaper for other countries, who will undoubtedly be interested in pursuing them. This cannot be said about tidal lagoons.
So why should we bother with them?