Sheringham Shoal wind farm

Here's a photograph of the Sheringham Shoal wind farm off the Norfolk coast. I took the photograph from the wonderfully named Beeston Bump. You can see the turbines on the horizon if you look carefully. Yes they are obvious, but sitting on the beach later I had to consciously search for them. Details are on https://en.wikipedia.org/wiki/Sheringham_Shoal_Offshore_Wind_Farm It suggests a sensible average output of 125MW. That's maybe one tenth of a big nuclear power station. One local critic suggested to me that a boat was sent out to the turbines every day which emiited more CO2 in fuel than the turbines save. I saw no ship working on the turbines in 3 days on the coast. Sadly I didn't have time to go to the visitor centre. Many things are said about turbines but I can never seem to get data to decide either way.

Einstein drinking tea in Sheringham

Einstein seems to get everywhere. Here he is at a tea shop in Sheringham, Norfolk.

Interesting wave-like pattern in the gill

We found this interesting pattern in a gill high above Hayeswater. It looked at first as if it would be due to stationary waves. But in the end it seemed more like a beach tide line pattern. It was very stable: we threw in a stone and the ripples on the water moved through the pattern (see below). The hole seemed to close up. Perhaps it is some kind of surface tension effect. It occured to me that there might be molecules with hydrophilic and hydrophobic ends lining up. I have no clear explanation.

Thunder storm over Wigton

There was a loud thunder storm over Wigton last night. We don't get many storms this far north. I filmed it but found that I didn't get any nice forks of lightning, just the lit up sky shown. The classic thing to do is to count. Light does have a finite speed - 300,000,000 metres per second. That's so fast that we can assume that we see the lightning as soon as it is produced. This is not true of more distant objects like the Sun. The light from the Sun takes 8 minutes to arrive. Thunder is made by the lightning heating the air so rapidly that there is a sonic shock wave as the air expands violently. The speed of sound in air is around 330 metres per second, though it depends slightly on temperature. That means it goes about 1km in 3 seconds, so 1 mile is roughly 5 seconds. I count slowly. I counted to 10 for this flash. The nearest was 5 seconds and later I got to 20 seconds!

Back to the circus: loop the loop calculation

I posted last week about the motorbikes at Zippos Circus. Upside down, the centripetal force must be equal to weight + normal reaction force. Centripetal force = mass x speed squared /radius of curvature so the faster the bike is going, the bigger the centripetal force. The weight will remain the same so the normal reaction force will increase. This is because the bike will try to go in a straight line due to its inertia. The metal cage will have to push back harder, hence the larger reaction force. Thus there is a speed at which normal reaction force = zero. The bike will no longer be in contact with the metal so the driver will be falling not driving. Centripetal force = weight mg. Simple cancelling means v squared = radius x g. Having seen a brave woman stand up between the bikes, I'd estimate the radius as 2 metres. So v squared = 20 and minimum speed to maintain contact is 4.5 metres per second. That's 16 km per hour - which is actually not very fast.

Caudale Quarry: Stone down a mine

We visited this quarry in Caudale above Brothers Water. We wanted to know how deep the shaft was so we timed a couple of stones down. The equations of uniformly accelerated motion give height h = 1/2*g*time squared. I got nearly 1.8 seconds which is 16 metres. We repeated the measurements. Second time it seemed to bounce down much deeper. I looked it up and was taken to one of my favourite blogs http://becausetheyrethere.com/2009/11/12/hartsop-hell-%E2%80%93-and-a-tribute-to-the-caudale-quarrymen/ You can read about the history of the quarry. He's even been down this hole and quotes it as 30 feet, which is about 10 metres.

Building Hayeswater Gill Hydroelectric power station at Hartsop

I've posted about hydroelectric power in the Lake District but I've never seen one being built.

The water is set to fall from the stream near Hayeswater at 400m to a level of 200m. The pipe will be buried under the road. The new power station will be on the site shown below.

That's right next to an old mine water wheel. It used the kinetic energy from the gill to power pumps to drain water from a nearby mine. http://www.mindat.org/loc-4753.html The new works therefore sit in an old industrial area with both mining and an old reservoir.

At 250kW, we were trying to work out how many houses it would power. Maximum consumption might be oven and shower at 8kW each. At full power, that would be only 15 houses. Glenridding Hydro is 500kW and claims to power 300 houses on average, so average power consumption for house would be 1.7kW. This seems reasonable but the National Grid is needed to cope with the fluctuations in usage. Suppose that the water falls without disipative losses and all mgh of gravitational potential energy turns into kinetic energy. The water would be going at square root of 2x9.81x200 = 63 metres per second. If average power = Fv and we assume that the generator stops the water dead so that F=rate of change of momentum = v x rate of mass, then average power = v squared x rate of mass. Mass flow rate for the water would be 250000/63 squared = 63 kg per second.

Inverse square law on Goats Water

This shows a stone thrown into Goats Water beneath Dow Crag. The ripples spread out. It reminded me of the inverse square law for light. As the radius of the circle doubles, the area quadruples. This would mean that the density of any energy inside the circle would quarter. It's normally done as an expanding sphere where the energy is on the surface of the sphere.

Loop the loop at Zippos Circus

We went to see Zippos Circus in Ayr. Loved it! This the Lucius Team doing their Globe of Terror motorcycle act. There were 4 of them in there at once. Analysis of the Wall Of Death type bits to come but in this picture, there is a rider upside down inside the top of the globe. Centripetal force is (massxspeed squared)/radius. Centripetal force is a resultant force. In this case, it must be the difference between the rider's weight and the reaction force. At the bottom, reaction force must be bigger than weight. At the top, I think that the bike will have lifted off a bit so that the weight is bigger than the reaction. As long as the speed is big enough, there will still be a reaction force so the bike will stay in contact. I thought this was going to be easy to explain but it's not quite the same as the normal problems so I'll have to think further.

11 degrees on Seat Sandal

 We climbed Seat Sandal from Dunmail Raise up its north western shoulder. The first section is really steep. The map showed the contours spreading out, meaning not as steep. But how much better? We consulted the map. 200 metres of climbing in 1000m of ascent - that would be along the hypotenuse. Sine of the angle would be 200/1000 or 0.3. But how do you work out an arcsine half way up a mountain? Thanks to Emily for the phone!

 I hung a plumb line as a reference for measuring the angle on the photograph. It's about 13 degrees. Go us!

Perseid meteor shower

I sat out last night looking for the Perseid meteor shower. My camera isn't good enough to photograph the meteors but you can see the Anthorn aerials in the distance. The media suggested 100 per hour. from Wigton, it was about 1 every 5 minutes from 11pm to midnight and maybe 2 or 3 in 5 minutes at 2.45am. The shooting stars are caused by debris from the Comet Swift-Tuttle being heated to high temperatures by friction as it enters the atmosphere. Incandescent hot material is shed, leaving a trail. It was wonderful. I also noticed how much of the Milky Way is visible from Wigton with a properly dark-adapted eye.

Nuclear view from RSPB Minsmere

Here's the view from the RSPB's nature reserve at Minsmere in Suffolk. The large building in the distance is the Sizewell B nuclear power station. It was the most recent to be built in the UK, being finished in the early 90s. I remember the political controversy about it. The upshot was that no more were built in the UK. It is a PWR pressurised water reactor. The fission reactions in the fuel rods cause thermal energy to be released. This energy has to be absorbed by a coolant and used to heat water elsewhere to make steam to drive a generator. It this reactor design, the coolant is ordinary water at very high pressure. This means that it is unable to boil even at temperatures of 300 degrees Celsius. The pressure stops particles from escaping the surface of the liquid. Radioactive gases are dangerous because they are hard to see and contain. Here the containment vessels need to be very strong to work at very high pressures. The water is also a moderator: it slows neutrons down. Slow moving neutrons are better at splitting Uranium-235 nuclei. The power station has an output of about 1200MW. That is roughly the same as the stated output of the wind farms at the end of Morecambe Bay, visible from Barrow. The wind farms will have a capacity factor of about 0.33 which means that actual output will be about a third of the stated value.

Tim Hunkin's water clock on Southwold Pier

I remember reading Tim Hunkin's cartoon strips many years ago. It was an excellent series about how things work. So I was very pleased to find this water clock. As ever with a clock, energy needs to be delivered to drive an escapement mechanism. This is a system that allows a cog wheel to slip round by one tooth in a regulated amount of time. Filling with water until a tipping point is reached and it emties could be one such way of measuring the time.

Siphoning

I needed to separate my fermented wine mix from the yeast. The yeast had been poisoned once the alcohol content was high enough and sank to the bottom. The method of extraction is siphoning. A large tube goes from the wine down to an empty demijohn on the floor. You get it started like a big straw by sucking on the lower end. This reduces the pressure at the lower end so that atmospheric pressure on the surface of the wine pushes it up the tube and out of the upper demijohn. The theory then says that the pressure difference is maintained by the falling liquid. I started thinking about whether it could happen with gases. I concluded that it might only work in liquids because of the cohesion of particles because they are touching in a liquid. This doesn't work in a gas. It turns out that cohesion is the rival theory to pressure for explaining siphoning. Both theories have counter examples. Siphoning works if you have a vacuum above the wine, apparently, so there is no pressure pushing the wine. And apparently it works with carbon dioxide gas. https://en.wikipedia.org/wiki/Siphon

Preparing for L6 Physics #10: Newton's Third Law

A good knowledge of Newton's Laws of Motion is very important as a basis for Physics. This is the canon at the citadel that Cromwell had built at Ayr on the Scottish coast. As Newton was born in the year that the English Civil War started, it seemed appropriate! I was taught that Newton's Third Law of motion says "to every action, there is an equal and opposite reaction". Applied here, the canon ball is shot forwards but the canon recoils backwards. The law has been rewritten as "if object A exerts a force on object B, then object B exerts an equal force of the same type on object A, but in the opposite direction". This new wording stresses that there are TWO objects involved and each experiences a force.

Quantum tunnelling telescope on Southwold Pier

I really loved this cheeky art installation at the end of Southwold Pier. In reality, it's an ordinary telescope with a sound commentary and film clips overlaid onto the view. But quantum tunnelling - that's one of the weirdest things there is. It uses Heisenberg's Uncertainty Principle. This says that you cannot know accurately the position and the speed (momentum, really) of a particle. The more accurately you know one, the less accurate the other becomes. Imagine an electron is going round a circuit and reaches a barrier - a gap in the circuit. This is often told as you walking along and reaching a really tall wall. You don't have the energy to climb the wall. The more accurately we measure your speed, the accurately we know your position. If that blurring of position includes places on the other side of the wall, there is then a finite probability that you are actually on the other side of the wall. Oh, there you are! You have used quantum phenomena to appear on the other side of the wall as if you tunnelled through. Electrons can really do this. This barrier has to be really, really thin if it is to work. Proper explanations talk about the attenuation of the probability function going through the wall.

Thinking about the jetstream

These clouds at Dunwich Heath got me thinking. The lower level cumulus were visibly moving from left to right (that's south to north) but the higher level cirrus looked to be streaming towards me in the photograph - that's west to east. Could the cirrus be high enough to be in the jetstream? A plane flew over just above the level of the cirrus. I've looked up flights along that route which seems to be London to Scandinavia. One I found at this point was at 33000 ft. That's about 10000m. The jetstream does occur at that height.

Dunwich: for whom the bell tolls?

In the Middle Ages there used to be an important port on the Suffolk coast called Dunwich. Coastal erosion and silting caused it to be abandoned and great storms destroyed it. They say a lot of the story is urban myth but there is a great legend that you can hear the bells of the 12 churches out from under the sea. Bells would be a problem in water. It is much more viscous than air so the clapper would find it hard to move. Supposing you could make a bell strike, the sound would travel faster in water than in air. Particles are closer in a liquid than in a gas so they pass on oscillations more easily. Sound goes about 4 times faster in water, although the precise speed depends on temperature. On reaching the surface, the sound would slow down. There would be refraction with the wave bending towards the normal line. That would make it hard to be in a position to hear the sound - but perhaps the top of the cliff would be the best place.

How loud is a wind turbine?

A lot is made about the noise of wind turbines. Camping right underneath one at Kessingland in Suffolk gave me the chance to experience it for myself. It is a constant background when the wind is blowing and as such I was able to zone out in the night. The traffic on the main road 2 fields away was more intrusive. I would say that it wasn't as loud as the sea at Rhossili campsite. The traffic noise in the middle of a city is definitely worse but then they don't put turbines in those sorts of places. It has made me resolve to see if I can find a sound meter to bring away with me to put a number to these noises!

Preparing for L6 Physics #9: Components of force - sailing at Blakeney

I spotted this boat at Blakeney in Norfolk! What happens if you want to go north but the wind is blowing north west? You use the idea that the wind is made up of one part north and one part west. You angle the sail to catch the north part. We use this idea a lot in Physics. It isd called RESOLVING FORCES and two parts (north and west here) are called COMPONENTS. Notice that they have to be at 90 degrees to each other.