Ireland day 0053. Saturday 20 November 2021- Megawatts

Ireland day 0053. Saturday 20 November 2021- Megawatts
Today’s summary Short walk to the estuary to watch the geese and calculate the power output of the tidal flow.  Then back up to Malahide to pick up free doughnuts followed by a quick trip on the no. 42 to Clare Hall Tesco in the evening and a major drain incident
Today’s weather Bright sun in the morning, cloudy and drizzly in the afternoon.  Light breeze, about 13C
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Today’s overview location
(the red cross in a circle shows where Val and I are at the moment)
Close-up location

Today’s post could be a bit technical I’m afraid.   So if power generation isn’t your thing, but you are intrigued by the photo of the doughnuts, you might want to skip the first bit and head straight to the dessert.   But I do need also to give you a heads up on major drain development.   Skip right to the end, then, if that’s all that really attracts your morbid attention.

It all started when Val and I were walking down the shores of the Broadmeadow estuary this morning, admiring the Brent Geese after their long migration.   Most were busy pecking away at the eelgrass in the shallows, but a couple were happily floating along as the ebbing tide poured rapidly out of the lagoon.   (By the way, Brent Geese and Eelgrass themselves have fascinating tales to tell, as you will learn if you read right to the end of this blog).

I watched the floating couple and idly noticed that they passed between two posts on the opposite bank, which were about 2 metres apart, in about a second.

Suddenly I realised that this observation, combined with the known width of the river at this point (about 100m) and the estimated depth (about 5m) would allow the power being dissipated into the ocean by the flowing tide to be calculated.

The cross sectional area of the river must be 100×5=500m² and as the speed, as measured from the geese, was 2m/s, the volume passing any point would be 500×2=1000m³/sec.  Since we know that kinetic energy = ½mv²,  (with the answer in Joules if the mass, m, is in kilograms and the velocity, v, is in metres per second), then the kinetic energy of a cubic metre (i.e. 1000kg) of the river flow at 2 m/s must be ½x1000x2x2=2000 joules.

Given that 1000m³ of water pass through the cross section of the river every second, this means that the total power of the river flow (because power in watts = joules per second) must be 2000×1000=2,000,000.

In other words, the power being dissipated by the flowing tide in this estuary is about two megawatts.   To put that in context, when the tide is flowing, that would be enough to provide all the power (i.e. gas and electrical) needs of about 400 average size houses.   Also by way of comparison, the new nuclear power station being built at Hinkley Point in the UK would generate about 1,600 times as much power as the Malahide estuary, and all day long not just when the tide is flowing.

PS I’m sure if I have got this wrong I am sure my engineering friends who are better at maths and physics than I am will be quick to correct me.

I’m not quite sure where this takes us but by way of a welcome distraction from all this cerebral activity, as we walked back through Malahide a van pulled out and a load of girls jumped out of the back and started doling out Krispy Kreme Doughnuts to passers by.   As we had two boxes practically thrust into our hands, and as I actually quite like them, we felt obliged to accept the gift.   I was disappointed to learn however that it this is not an everyday occurrence in Malahide, it just happened that we got lucky when the company decided to do a promotion for its new KKD store in nearby Swords.   Anyway they will make a welcome addition to our packed lunches for the next few days.  Or weeks, even.

After a late and rather delicious lunch of aubergine curry and doughnut, Val dashed off to work and I headed to the bus stop to catch the No. 42 to the Tesco Extra at Clare Hall for the week’s shopping.   I am getting quite adept at managing the buses, and whereas the last time I returned from Clare Hall by public transport it took an hour and a half, this time I was back in the flat in under 20 minutes.

So now the shopping is safely stowed, i just need to resist the temptation to finish off the doughnuts (though I might just need to try one to check that it’s OK) and get on with yet more Spanish homework.   At the moment I am trying to figure out when you use the verb “soy” and when to use “estar” and it’s doin’ me ‘ed in, as they say.

…And finally.

My last blog attracted a lot of attention from those who – with some justification – pointed out that the correct way to deal with a blocked drain in a rented flat was not to try and fix it yourself but to call the landlord and get them to sort it out.   Although I do have a great deal of sympathy with this approach, I realised that the plumber might not come until Monday, and then I would probably have to wait in all day until he or she showed up.

Then at Tesco this evening, an alternative suddenly presented itself in the form of Mr Muscle drain gel.   Ever keen to seek a quick fix, I bought a double dose and rushed home to try it out.   The first dose had no effect and the drain remained stubbornly solid.  It was with growing self-doubt that I chucked the whole of the second bottle in and waited half an hour (the instructions say 5 minutes is enough) to see what would happen.   Time being up, I sent down kettle full of boiling water as a chaser.   And suddenly it happened.   There were a few gurgles, a great burp, and suddenly the blockage could be heard sloshing its way through the pipework behind the fridge, presumably on its way to add a bit of kinetic energy to the Broadmeadow river.

So now we have a sparkling clear sink with a free flowing drain, which brought to a close an altogether most satisfactory day


Today’s photos (click to enlarge)

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I was pleased to notice that Val’s peanut butter and aubergine curry today looked exactly the same as my beef casserole (and it tasted equally as good) Brent Geese like these in the Broadmeadow estuary today over winter around many of the Irish coasts, grazing on eel-grass.   They fly 5000km / 3000mi from Canada via Iceland to get here and reverse the journey in the spring.   Quite an amazing feat of endurance and navigation.   And equally amazing is the life cycle of the eel-grass which they eat.   It is a flowering plant not a seaweed (which is an alga) which lives exclusively under water apart from the flowers which just reach the surface and are held there like saucers by surface tension
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I am still surprised by how flowery it is here – there still hasn’t been any frost down here by the coast, so maybe the shrubs like this just keep flowering all year? Slightly alarming woodcarving on the path back from the shore to Malahide.   Not sure I’d like to bump into her on a dark night.
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New stainless steel sieve proudly acquired tonight.   More husband-proof than the plastic variety Unfortunately I think I had indeed waited for clog chaos but fortunately all that has burped its way into the Malahide estuary now!
Well yes – 2 megawatts would generate an awful lot of current
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