japan

After the tsunami: how tidal energy could help Japan with its nuclear power problem

This article originally appeared in The Conversation. It is licensed CC-BY-ND. Click here for original.

Japan was the third-largest producer of nuclear power in the world in 2011. Then, on March 11 of that year, an earthquake of magnitude 9 was followed by a catastrophic tsunami, resulting in the first nuclear disaster of the 21st century – at the Fukushima Daiichi power station. The country’s nuclear plants were shut down, and within a year Japan had become the world’s second biggest importer of fossil fuels.

Before the tsunami, nuclear power provided 25% of Japan’s electricity, and a strategic plan was in place to expand this to 50%. Japan has few fossil-fuel resources of its own, so most of the resulting shortfall in electricity was made up by burning imported coal, oil and gas – an unsustainable solution from both environmental and economic perspectives.

But on a group of islands to the west, tidal power may offer part of the solution to the country’s energy needs.

A renewable future

By 2030, the Japanese government plans once more for nuclear power to provide around 21% of the nation’s electricity – which is highly controversial – but also stipulates (see page 8) that 22-24% should be delivered by renewable energy sources. At a local scale, two prefectural governments, Fukushima and Nagano, have pledged that all of their electricity will come from renewables by 2050.

Most of the new renewable energy available in 2030 is likely to be solar and wind, along with existing hydropower, but some contribution from the tides is possible. To this end, a zone in the Goto Islands of Nagasaki Prefecture has been designated for tidal energy development, and a cluster of companies plans to install the first turbine in 2019. This project will be of the tidal stream type, where underwater turbines are placed in the free flow without any dam or barrage, similar to the MeyGen project in Scotland.

Installing a tidal stream turbine base at the MeyGen project off the coast of Caithness in northeast Scotland.
MeyGen/Atlantis Resources

When tidal turbines are placed in a channel, they remove energy from the flow. This causes it to slow, and represents a partial blockage of that channel. In turn, that means that the behaviour of the tides in an area after turbines are installed can be different to how it was before. Understanding and predicting this change is important for estimating both how much energy is available and the impacts of removing it; if there are too many turbines, the flow could slow too much and much less power would be generated.

Going with the flow

My recent work, in collaboration with researchers in Scotland and Japan, involved using a computer simulation of tidal flow around the Goto Islands to investigate the effects of installing large numbers of turbines.

We estimated that between 24 and 79 MW of power could be generated from the designated area. The reason for this range is because the number of turbines that are used will ultimately depend on economic considerations. The first few will offer the most benefit, while later ones will suffer from diminishing returns. Tens of megawatts represents a very small contribution to Japan’s overall electricity needs, but a very large chunk of the local demand in these islands.

A number of parallel channels run through the Goto archipelago, of which two are within the tidal energy zone. In situations like this, it is common to find that adding turbines to one channel simply causes the water to flow by a different route. That means that to harvest energy efficiently we need to collect it from all the channels at once – an expensive proposition for a new technology.

In the Goto Islands, all the channels run parallel but separate to each other, never merging or meeting, so they can each be exploited without affecting the others.
Elsevier, Author provided

However, our modelling shows (see sections 4 and 7.2) that the parallel channels in Goto do not behave this way; instead, they are independent of each other. The reason for this unusual behaviour lies in the geometry of the islands.

Partially blocking a channel causes water levels to rise a little behind the blockage. The interactions that we see elsewhere in the world are a result of this extra water “spilling” into other channels. In Goto, because all of the channels run separately from one end to the other without meeting or merging, and because their mouths are spaced well apart, there is no way for this “overspill” to occur. Consequently, any or all of the channels can be exploited without affecting the others, which should make the area more attractive for commercial development.

If the relatively small-scale development in Goto is a success, it could act as a proving ground and a springboard, leading to the use of tidal energy in other locations all over Japan. And for a country ambivalent about its return to dependence on nuclear power, additional contributions from renewable energy will be welcome.

The Conversation

Posted by simon in Working in Japan, Written elsewhere

Two new publications

I’ve had two publications appear online in the last few weeks, in the opposite order to that in which I actually did the work. They have a lot in common, using similar methods in different locations, so I thought I’d write about them together.

The most recent is my second journal article as lead author, and one that I’m quite proud of. It covers the work that I did in Japan last year, and in the months after returning, on the tidal energy resource of the Goto Islands of Nagasaki Prefecture. We produced estimates of the amount of power that could be obtained – which is mostly of interest for the people planning tidal development in that archipelago – but of more general interest are the findings about inter-channel interactions. The Goto Islands have several parallel channels that could contain turbines.  When this arrangement has been studied in other places, it has usually been found that putting tidal turbines in one channel causes flow to divert into the others, and hence that to reach the full potential for power we would have to put turbines in every channel. Goto doesn’t behave like that – instead, the channels have very little effect on each other – and in the paper we looked a little into why that is. My thanks are due, of course, to my co-authors on this work, both in Scotland and Japan.

 

Plot showing the mean power produced by different numbers of turbines in the Goto Islands.

Plot showing the mean power available from various numbers of turbines in the channels of the Goto Islands, using simplified M2 tides.

Just a few weeks ago I attended the EWTEC conference in Cork and presented this paper on Lashy Sound, which is a channel with strong tides in the Northern part of Orkney. In this work, I used very similar methods to those that were developed in Japan to look at the tidal resource – in this case, not for realistic turbine developments but in terms of the theoretical maximum available power if we didn’t care about things like environmental impact, or allowing ships through. Unsurprisingly, it looks like achieving this maximum yield would have some significant impacts. I also considered the more plausible scenario of a smaller tidal farm, similar to the 30MW one that has been planned for the area, and was able to show that its effects would be small and confined to Lashy Sound itself – something that’s important when other potential tidal energy sites are just a few km away in neighbouring channels.

Both of these papers are available for free at the links above, or at the publications page on this site.

Posted by simon in Explaining my work, Publications, Working in Japan

Timber structures and notions of permanence

There was a sign that amused me, on the summit of a sacred mountain, which read,

“The Konpon Daitō is the tallest building in Kōyasan… In later centuries the Konpon Daitō was destroyed in fires caused by lightning striking five times, and rebuilt each time. After the great fire of 1843, only the foundation stones remained. The existing building was rebuilt in 1937.”

Some people just don’t seem to get the message!

But it illustrates a wider observation, which is that in Japan an ancient wooden temple or other structure can still be ancient even if it has been rebuilt many times, the latest sometimes being quite recent. Indeed, it is tradition that some of the most important temples are deliberately torn down and rebuilt every few decades. Other places are “renovated” every 50 years in a way that pretty much entails dismantling them and putting them back together again, replacing timber wherever it is no longer sound. These processes don’t cause anybody to think of them as modern structures.

A white, traditional castle. Although it's hard to tell, it's constructed from concrete.

Kokura-jō: Four hundred years old, or sixty?

A similar concept applies to castles. Castles in Japan were made of wood, and thus prone to being burnt down – sometimes by accident, sometimes by the enemies of the occupants, and sometimes by the occupants themselves on the occasion of their departure. When one visits a castle one tends to find a litany of all the times they were destroyed and rebuilt. It’s not unusual for the last rebuilding to have been in the 1950s or 60s, out of reinforced concrete, but they’re not really thought of as replicas.

There’s a strong element of My Grandfather’s Axe here. It’s echoed to some degree in descriptions of British churches (and occasionally pubs), which tend to go “There has been a church here since 1273…”, but the British think in terms of the site: there was a church here, but it was not this church. The Japanese view of it, at least as I perceived it through the flaws of translations, is that it’s the same building. It’s as though it’s the notion of the building that’s important, rather than its physical or material structure.

A new-looking timber building behind a fence in woodland, built in the style of a pre-buddhist Shinto shrine

Ise Grand Shrine: Two thousand years old, but rebuilt every twenty. Photo: Flickr user Kzaral, licensed CC-BY 2.0

Posted by simon in Working in Japan

Japan is not afraid of infrastructure

I’m writing this as a lay visitor; I have no insight into the Japanese planning processes.

A mess of overhead power cables meeting at a street junctionBut travelling around the country, it struck me that infrastructure in Japan is visible, and they don’t seem to be ashamed of it. Streets have their power lines overhead, rather than buried – like much of America, but strange and messy-looking to a European eye. In areas suitable for heavy industry, there is heavy industry. One sees large power plants, chemical plants, gas storage tanks, etc., close to populated areas, with no attempt to disguise them. Plans for any of these facilities would cause uproar in the UK.
Most towns, even agricultural ones in pristine valleys, have one or two large radio masts, painted red and white, rising out of a municipal building (often one belonging to the former state telecoms company, or sometimes a post office). Some of these are festooned with microwave dishes, but most just have cellphone antennae now; I suspect that they are the relic of an extensive microwave network that has since been replaced, but they haven’t been torn down. Contrast to the arguments in the UK that led to some cellphone masts being disguised as metallic trees.

Communications tower rising from a municipal telecoms building in Japan

Photo: Wikimedia commons, user Prosperosity. Licensed CC BY-SA 3.0.

There isn’t much onshore wind power, and I don’t know why that is – but I don’t think it’s likely to be about visual impact, since everywhere one sees electricity transmission lines “marching across the landscape”, with the towers once again painted bright red and white. It’s notable that – in a way that will be familiar to everybody who has lived near such things – after a few days they stop being obtrusive, and become a part of the landscape that is largely filtered out of conscious perception.
The shinkansen, built from the 1960s to the 2000s, zooms across the whole country on elevated tracks, visible for miles in every direction. Recently there have been complaints about noise from high speed trains, and as a result the latest line has noise barriers – which help with the noise but make the tracks themselves more visually obtrusive. Contrast with the “debate” about HS2.

I’m not praising or criticising the British or Japanese attitude here, and I don’t feel that I understand enough to hazard any guesses in public as to the reasons behind the differences, but I found them very striking.

 

Posted by simon in The wider world, Working in Japan

I aten’t dead.

I’ve been rather quiet on here. Sorry. I have a couple of draft posts awaiting photos, but I probably won’t have the photos sorted until I get home and catch up with life. In the mean time, here’s a really bad photo of Tokyo Haneda airport just after midnight:

View through a window - Cartier store reflected in the glass, and planes behind.

I’m on my way home, and I have very mixed feelings. After two months I’m ready to resume “normal” life, to see friends and family, to speak English without always gauging how much I should slow and simplify my language according to the listener, and to sleep in my own bed. Probably for about a week. On the other hand, I will miss Japan. It’s a fascinating place, and while I understand it a lot better than I did eight weeks ago, there’s a long way to go on that front.

I hope I have the opportunity to return one day.

Posted by simon in Working in Japan