The Tide is Turning on Energy

pojo

Sun Nov 05 10:12:47 -0800 2006

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I thought the reason why tidal power hadn't been pursued was because of the negative impact it had on sea-life and tides in the area. It's nice to see that they are still working on solutions for tidal power. I notice in the article they are devoting $2 million to monitor fish.

I just looked at a government site on tidal power which mentions that the tidal turbines mentioned in the article probably have the smallest environmental impact on sea life.

Tidal energy is difficult for environmental reasons

Martin Blank

Sun Nov 05 10:43:40 -0800 2006

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The main reason tidal power isn't around in quantity is that lakes by and large don't have enough motion to make it practical, placing it in rivers can disrupt erosion patterns, and ocean water is incredibly destructive to machinery.  What isn't eaten by saltwater can be coated in barnacles.  However, with some recent materials advances as well as the recent understanding of the adhesive compounds generated by barnacles (between those and gecko feet, we have a sticky future ahead), it may be that we'll be able to tap the resource longer than before.

The Tide is Turning on Energy

Simon

Sun Nov 05 12:38:04 -0800 2006

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The river Severn in the UK has been proposed many times as a site for tidal generation, due to the rivers extreme tidal ranges, and other natural geographic advantages of the site.

The most recent proposal (1989 Severn Tidal Power Group) was defeated predominantly on cost grounds, since the electricity whilst produced cheaply, is dependent on massive upfront infrastructure costs. Which has to be repaid.

Of course recent changes in the price of oil, and gas, may change the balance here.

There was extreme concern about the impact on the mud flats in the region when the proposal was last presented, which represent a major feeding ground for migrating birds, and would be pretty much devastated by the proposed scheme.

I suspect if the cost argument was stronger, it would prevail over the environmental issues, as even the environmentalist would struggle to argue against something producing so much electricity without substantial greenhouse gas emissions (after construction). One area of uncertainty was the effects of barrage construction on silting in the estuary, which could greatly increase the generating costs (and greenhouse gas emissions) depending on if, and how much, routine dredging is required. But I'm guessing that is probably calculable these days.

If the Severn tidal barrage was not cost effective, I doubt there are many locations where tidal barriers would be.

The Rance tidal barrier is reported still charging substantially more per Kilowatt Hour than an equivalent gas power generator would cost. As such tidal and nuclear are in a similar boat, both have huge upfront costs, but low running costs, difficult to assess environmental impacts, and struggle to be economic unless we pay a lot more for fossil fuels (for whatever reason), or figure out how to build them more cheaply.

One of the concerns for the Severn barrier was creating an industry producing tidal barrage components (as would be needed), would substantially reduce the cost of further schemes, and might lead to a domino effect, where every river with a decent tidal range ends up being barraged. I think this unlikely, due the the awkward timing of tidal generation, since the market for electricity at peak tidal generation times would be quite low once one big scheme is in place (except where those times happen to coincide with peak usage). Assuming peak tidal times are likely all to be within an hour, or so, of each other around a country like the UK.

Hatfield Marine Science Center

President4242

Mon Nov 06 10:52:32 -0800 2006

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Has a project going on right now in this arena- though theirs is *wave* power generation rather than tidal generation.  Basically it's a bouy that works like one of those shake flashlights- a magnet on a spring that moves through a coil as the bouy bobs up and down in the waves.  Word is that their one acre test site, which will go on line next spring, will generate around 1TW- with no more impact to marine life than a kelp forest.