Biomass and Carbon Neutral in Langdale

I posted last week about why burning wood was carbon neutral. I found this on a camp site in Langdale. The National Trust have installed what must be a wood burning energy plant. Actually, reading the third picture, it's probably a fancy way of saying that they use wood to boil water. When they say 150kW, I wonder how many hours it runs for. But I particularly like the diagram of the Carbon Cycle. Not really sure about the left arrows at the bottom. They show energy when they should really show a molecule with carbon in. But it's good to see a scientific explanation.

 

Wir sind Helden and the earthquake experiment

My new favourite band are a German language band called Wir sind Helden. When they played the Rock am Ring festival in 2007 they were part of a seismic wave experiment. Part way through the concert, they had the crowd of 50,000 people jumping up and down in time. There were seismographs at different distances from the site. My German isn't yet that good but I get the impression that they didn't detect much. But they were trying to answer the question about what would happen if everyone on Earth jumped at the same time as part of a popular science programme on WDR. I've done that calculation before and the answer is - er, nothing! See the concert at https://www.youtube.com/watch?v=_rcU6elIIFg Read about it at erdbeben-experiment-50000-huepfer-liessen-die-eifel-beben-590408

Slackline and lack of balance

It's all about balance on a slack line. I didn't do very well. Balance involves keeping your centre of gravity within the base area. In this case that will mean keeping the centre of gravity above the slackline. The problem is that the line keeps moving from side to side so you need to wobble your centre of gravity with it. I stuck out my arms. This increased my moment of inertia which makes it harder for me to spin one way or the other. That means there is more time for me to make the adjustment of my centre of gravity before I fall. It didn't work for me!

Diffraction on St Bees beach

I took this picture on the beach at St Bees in January. The wind was blowing from the north, pushing the waves down towards me as shown by the two big arrows. At A and C there is some diffraction around the big stone but the water is much less disturbed at B than it is on the far side of the rock. If you look at the other rocks it is also true that the water is much less disturbed on this side than the far side. The situation is like FM radio waves trying to diffract around a mountain. The wavelength of these water ripples is much, much smaller than the size of the rock so there is not much bending (diffraction) around the rocks. That's why FM radio reception is poor inn the Lake District. The radio waves are much smaller than the mountains and don't bend round them very easily.

Colour theory

I'm quite flattered by this effigy so thanks to the person concerned. You know who you are! The colours that we see are governed by what reflects. White light was hitting this board. Blue ink absorbs red and green but reflects blue so that's what we see. The white board reflects all of red, green and blue. They are mixed together to let us see white. Red, green and blue are called primary colours in Science because they mix to make white. Art has different primary colours with a different explanation.

Approach Lighting System

 

The nature reserve at RSPB Valley Wetlands is littered with approach lights for the air base next door. There is a clear warning not to look into the lights because they can come on at any moment. They must be bright enough to be seen from a long distance away. I was interested in the design of the outer cover. It is not flat glass but divided into what are probably intended to be like small lenses. There will be a parabolic mirror behind the bulb to pull the light into a beam. Maybe the lenses keep it the beam together more. I have been unable to find out any more about it so I can only speculate. 

Paying for electricity #2

You can work out how much it costs to run a piece of equipment by looking at the label and finding its power in Watts.

 

For each of these pictures:

a. Find the power in Watts and turn it into kilowatts (kW)

b. Multiply the kilowatts x the hours it is on (kW x hours gives you kWh)

c. Let's say 1 Unit of electricity (1 kWh) costs 12p. Take your kWh from part b and multiply by 12 to give you the cost in PENCE (not pounds!)

 

Do a, b and c for all of these examples:

 

1. Electric heater left on for 3 hours.

 

 

2. Old fashioned "stereo" left on for 4 hours.

 

3. Hairdryer left on for 1 hour (not mine!!)

 

4. Kettle used for half an hour.

 

5. Microwave used for 1 hour.

 

6. Bread maker used for 5 hours.

 

7. Iron used for 2 hours.

Back to the log burner

A log burner is a metal box with a large surface area because infra-red heat radiation is emitter from the surface and into the room. The bigger the surface area the more heat radiation is sent out at once into the room. The box is painted matt black because this is the best surface colouration for emitting heat radiation. OK, I know matt black is also the best absorber of heat radiation but it would be a stupid heater that absorbed thermal energy from the room! You have to think about the context.
It is true that wood is a renewable resource, which can be given as an advantage. However, it DOES release carbon dioxide into the air when it is burned. We say that it is CARBON NEUTRAL because the trees use up carbon dioxide doing photosynthesis when they are alive. The carbon becomes part of molecules like starch that we then burn. The carbon in the molecules reacts with oxygen in the air to  make carbon dioxide as it burns. It is like a mini Carbon Cycle. We say "carbon neutral" because it takes carbon dioxide out of the air when growing and puts it back when burning. You end up with the same amount that you started with. Fossil fuels like coal, oil and gas have been keeping carbon safe underground for millions of years. When they burn they increase the amount of carbon dioxide in the air NOW so we cannot call them carbon neutral.

Paying for electricity #1

Houses in the UK have an electricity meter. It measures the numbers of Units of electrical energy that are used. A Unit is also called a kilowatthour (kWh). Electricity meters are now mostly put on the outside of houses in boxes like this so that you don't need to be in if they want to read it.

 

 

This is what the meter said on 26 November 2013.

 

This is what it said a week later on 3 December 2013.

 

This is the reading 2 months later on 31 January 2014.

 

 

One kWh costs about 12p at the moment.

 

1. How many kWh of electrical energy were used between 26 November and 3 December 2013, and how much did it cost?

2. How many kWh of electrical energy were used between 3 December 2013 and 31 January 2014, and how much did it cost?

Transformer substations and the National Grid

It used to be the case that every town had its own power station that made electricity for that place only. Eventually it was thought more sensible to build huge power stations for the whole country and connect them up using power lines. The problem is that miles and miles of cable waste a lot of energy. Electric current heats the wires slightly so that they dissipate thermal energy to the surroundings. If you use transformers before the electricity goes into the cables, they use electromagnets to increase the voltage. This also reduces the current so there is less heating of the cables. Less energy is wasted so we say that the system is more efficient. However, you wouldn't want a huge voltage like 425000V in your home. More transformers are used to bring the voltage back down to normal. These transformer are called substations. There is a huge substation in the picture above. It is just above the railings. This substation is for the chemical factories on the outskirts of Runcorn in Cheshire, just south of the River Mersey. It also sorts out the voltage for the ring of cables that go round to Liverpool and back. The National Grid is said to be both the overhead power lines AND the transformer substations. Without both of these it would impossible to send electricity round the country.

Difraction around mountains

For years I have been teaching that FM reception is rubbish in mountain areas and Long Wave reception is good. I have never noticed this as clearly as in Killin in the Scottish Highlands. Like water waves, radio waves diffract around objects. You'd expect to find a calm sheltered spot behind an object (like sheltering from the rain) but if the waves are roughly the same size as the object then they will bend round the far side of the object.

All radio waves travel at the speed of light 300 000 000 metres per second.

Radio 4 FM is 94MHz. That means the wavelength is 300 000 000 000 divide 94 000 000. This means that a wave is roughly 3 metres long. Mountains are much bigger than this so the FM waves won't bend round the mountain.

Radio 4 Long Wave (LW) is 194 kHz. The wavelength is 300 000 000 divide 194 000. This means the waves are about 1500 metres long. That's much closer to the size of Ben Lawers, shown in the picture! The views from the top were magnificent. 60 miles all round. And I had good LW reception in the valley but nothing on FM. I like it when Physics does what it should.

 

Lenticular clouds over the Lake District

This is the view from the top of Sail looking back towards the Helvellyn range. I took the picture through my polarising sunglasses to enhance the effect. Lenticular clouds are the ones that look like flying saucers. They are the ones reported as UFOs. There was a strong wind blowing from the right of the picture. As that has to rise over the mountains, a stationary wave is formed on the other side of the mountains (the left of the picture). The peaks of the antinodes get cold enough for condensation into cloud. I suppose that the wave packet gives rise to the saucer shape.

It has just occurred to me that I can check one of these claims. If I find the photograph taken in the direction that the wind is coming from, there shouldn't be any lenticular cloud because this should form after it has been over the mountains. Here's the picture looking south over Robinson to the Scafells

 

Lo and behold! There are a few cumulus in the far distance. Thus far the theory holds up!

Cumulus cloud over the Welsh mountains

This was a remarkable sight from the beach on Anglesey looking back towards the Lleyn Peninsula and Snowdonia. What I think was likely to be happening was evaporation of the sea due to strong sunlight. The wind was blowing the air laden with vapour towards the coast line. On reaching the mountains, the air was forced upwards and cooled. This would make the water vapour condense into clouds. Cumulus clouds are formed by evaporation on days like this. The line of mountains probably explains the line of cumulus.

Voltage Optimisation at Conwy RSPB

 

Conwy RSPB had this mysterious notice on the back of their coffee shop. I have had a poke around the Internet to find out what it is about, although you can read what they say on their notice. I will look into it in more detail but opinion seems to be that the biggest advantage comes in terms of inductive load. That is the realisation that it isn't just resistance that causes problems in AC circuits. Equipment with electromagnetic coils in like motors will generate back emf by having a magnetic flux turning on and off repeatedly within the coils. If this effect can be reduced then energy can be saved.

Why don't nuclear power stations have cooling towers?

We ended up next to Wylfa nuclear power station on Anglesey, the island off North Wales. We had been looking at the data on nuclear power stations in class. Wylfa is given as having half the power of the other power stations. I have found out that it is because one of the two reactors has been shut down already and the other will shut next year. It is the oldest nuclear power station still operating in the UK. There are no cooling towers. The reason is that it is beside the sea, so the water needed to run the turbine system can be taken from the sea. It is thought that the sea is such a vast pool of cold water that the thermal energy in the water that is put back will give such a small share to each individual water molecule that you won't notice a rise in the temperature. This is not the case with rivers, so a nuclear power station inland by a river would have to have cooling towers.

Offshore wind farms in Liverpool Bay

We were driving along the North Wales coast and I spotted this enormous offshore wind farm. I looked it up and it seems to be three wind farms that merge into one. http://en.wikipedia.org/wiki/List_of_offshore_wind_farms_in_the_Irish_Sea I'd have said up to 200 turbines by inspection yesterday but the list doesn't back that up. The quoted capacity would be240MW which is about half of that of Wllfa nuclear power station. However I also found something called  a "capacity factor" which is roughly what fraction of the stated capacity they produce on average. If capacity factor is about 0.33, then 80MW would be a more realistic figure.

Incandescent in the Secret Cave

I lit a candle so that we could see what we were doing in the Secret Cave in Langstrath. So why is a candle flame yellow? It produces a lot of small soot particles which are heated to a couple of hundred degrees. Then they act as tiny black-bodies. A black-body is a technical term in Physics for a perfect emitter or absorber of electromagnetic radiation. They all emit across a continuous spectrum but the colour that you see comes from the wavelength that produces the peak in the spectrum. Wien's Law says that wavelength x temperature (in Kelvins) = 0.0029. So if temperature increases, wavelength decreases. At hot temperatures, that wavelength is enough to be visible. The hotter it gets the more it moves from red through to blue. So a yellow flame is not actually that hot.

Funicular railway on Cairngorm Mountain

We went up the funicular railway on Cairngorm Mountain for the first time in a decade. It was the last weekend of the ski season. The ski station is in the top left hand corner of the first picture. It is 453 metres higher than the bottom station. There are two carriages on the railway and they are tied together by a steel cable. When one goes up, the other goes down. In the bottom photograph you can see that there is a short section in the middle where they can pass each other. In an ideal, frictionless world, no energy would be needed to move two carriages of equal mass. The gravitational potential energy lost by the one going down would be transferred to the one going up. The maximum load is 120 passengers. Let's consider a situation where the carriage going up is full of passengers but the one going down is empty. The falling carriage cannot provide all of the energy needed to raise the other carriage with passengers so a motor is needed to pull on the cable that joins the carriages. 120 passengers at say 60kg each is 7200kg. By mgh, it needs 32,600,000J of energy to raise them to the top station. The fastest journey takes 4 minutes. 32,600,000 / 240 seconds = 134kW. This is much lower than the stated 1000kW operating power of the motor. Ah, but we assumed no friction ...

Polarised TV waves

 

Here are two photographs of television aerials. The top one was taken in Aviemore and the bottom one is my own TV aerial. Notice that the metal bars are at 90 degrees to each other. This is because TV signals are polarised when they are transmitted. Polarisation is when a transverse wave is made to vibrate in only one plane. If you polarise TV waves, you can send out twice as many from a transmitter without them interfering with each other. My aerial will only detect TV waves that oscillate in the horizontal plane. In Aviemore, the TV waves seem to be polarised to vibrate in the vertical plane. It is important to orientate your aerial appropriately.

Electric car in Berlin

I was amazed to see this electric car charging up just behind the main street in Berlin. I have never seen this happen in the UK. An advantage of using electric cars is that they do not emit any exhaust chemicals that would cause air pollution in the city. Hence there is no ozone at street level, no nitrogen oxides and no particulates. Particulates are very small soot particles that cause respiratory problems in humans. It is wrong to say that electric cars cause no air pollution though, because they use electricity that is often made in power stations that burn fossil fuels. Electric cars are quieter so there is less noise pollution.

Rydal Hall Hydro-electric scheme

 

Rydal Hall has had a water-powered generator for decades. The water uphill has gravitational potential energy. As it falls through pipes, the gravitational potential energy turns into kinetic energy. This energy is transferred from the water to a turbine. The turbine turns a generator. The generator transfers the kinetic energy into electrical energy. During every energy transfer, some energy is dissipated as thermal energy to the surroundings due to friction. It is friction between the water and the pipe walls at first. Then it is friction between the moving parts of the turbine and generator. It is always important to say where the friction acts. There is further important information about the turbine in the notice in the photograph.