Long shutter setting

These two pictures were taken a few seconds apart. The one above is what I could see with my eye. The shutter was open for a fraction of a second. And this was with a digital camera where the quantum efficiency is much higher than that of a silver nitrate film. Below is a shutter time of 8 seconds. You'd think it was just a dull day. It was close to full moon, but the moon was behind the clouds. It shows how much light is out there and gives an insight into the world of nocturnal animals.

Wifi

This data on a wi-fi box had me looking up the frequencies. FM radio is 88 to 108MHz so these are much higher frequencies. Infrared can be as low as 300GHz. These are radio waves but much shorter wavelengths than the broadcasters. The frequency ranges of different types of radio wave are here. dBm is explained here.

Vega in the constellation Lyra

 

Vega is well known for being a bright star so I was wondering why. It turns out that it is very close at only 25 light years which explains a lot about the brightness. But it is twice as heavy as the sun so that means it burns though its fuel faster and is hotter, a class A star. These hotter stars have much shorter lives; I was amazed to discover that it was only "born" during our Cambrian period. Using data from here, it is have roughly twice the radius of the Sun, so it has 4x the surface area. The temperature is roughly 1.7x. By Stefan's Law, that would mean the luminosity is 4 x 1.7 = 33x more luminous. The data gives 40x but there are quite large ranges in the radius and temperature data.

Sunspots and luminosity

Here are a couple of sunspots from last week. I've been looking into how they form. They are colder patches formed because concentrations of magnetic flux get in the way of convection currents near the outer surface of the sun. The centre of a sunspot, the umbra, is quoted as being 3000 - 4500 Kelvin whilst the surface of the sun is usually 5780 Kelvin. Normally, anything at the temperature of a sunspot would be glowing very brightly and would be quite a red colour. The luminosity is proportional to the fourth power of the absolute temperature by Stefan's Law. This means the usual surface is say 5780^4/4000^4 = 4.4x brighter. The contrast makes it look dark rather than red.

Wind turbine carbon footprint

There was always a lot of talk round here about a rumour that the amount of carbon put into the foundations of a turbine released more carbon than it saved over its lifetime. I'm back with the book "How Bad are Bananas?" by Mike Berners-Lee. On page 153, he has a table which suggests that a 660kW turbine like this should have paid back the carbon released in its manufacture, transportation and installation in 145 days. That's less than half a year. This turbine has been in for more than 20 years. The rumour is not true. The source of the information is this paper. 

Arcturus

 

Last month the constellation Bootes was prominent in the western sky after sunset. I've coloured it in the photograph. The circled star at the bottom is Arcturus, which is the brightest star in our northern skies. It is a red giant so has expanded giving a much larger surface area and hence a high luminosity since Stefan's Law says that luminosity is directly proportional to luminosity. It is also very near, being only 37 light years away. It is a K class star. The classes are OBAFGKM (which I remember as Oh Be A Fine Guy, Kiss Me). K stars are much cooler.

BESS - Battery Energy Storage Systems

 I had thought that we stored excess electrical energy in this country by using pumped storage but it seems that we are now heading towards using fields of lithium ion battery banks. I got the hint from the BBC and from there found the interactive renewables map from this website.

Are wind turbines more powerful in the rain?

The other day, I had a claim repeated to me that says that wind turbines produce more power in rain. It's an appealing idea that I must imagine is based on rain being denser than air. There is a change in momentum when air hits the wind turbine. For the same change of speed, water would produce a bigger change in momentum and thus more force. If this is true, I can find no reference to it online. This paper only deals with Vertical Axis turbines whereas the common ones pictured are horizontal axis. It suggests that VAWTs perform worse in the rain.

Air-source heat pump

I had become aware that air-source heat pumps are not free energy. This came out when fossil fuel prices rocketed last year. In the end, air-source heat pump people also paid high bills because of the electrical energy that they use. I finally managed to get a look at some data. It looks like one heating unit is worth 12kW but uses about 3kW of electrical power. Now 3kW is my full convection heater and we would consider that expensive as the only heating option. But that would heat only one room whereas I suppose this heats a whole house.

Measuring in chains

I was interested to see that an old measurement of "chains" was still in use on the railways - mind, to some extent a mile is an old measurement if that means not metric. I looked up the origin of chains. It turns out that Edmund Gunter chose the length of 66 feet for his chain because it fitted well into area calculations. 10 square chains is one acre. It is almost 20 metres in length and in India, that is now how long a chain is. Railways fix location by distance measurement because they are linear features so as long as you know which end was the start, distance is the only coordinate needed to fix location. Best help was to realise that a cricket pitch is exactly 1 chain long. Now I can visualise it.

More sunspots

The sun is finally back out so it's been possible to see sunspots again. In the meantime, we found NASA's sunspots site. 

Superconductor?

This looks like a circuit with a current but no emf. Must have no resistance! 

Gate like an electric field pattern

This gate near Rosley reminded me of an electric field pattern. At least, the middle circle bit did. If the bottom bar was also positive, I'd be expecting a pattern like the one I've drawn in red on the right hand side.
 

Last coal-fired power station

 

Ratcliffe on Soar is a familiar sight and is now the last coal-fired power station in the country. It shuts next year. at 2000MW it is worth maybe 250 solar farms. Actually, that doesn't sound like too many. It is said to power 2 million homes. There are said to be 27 million homes (dwellings) in the UK. So this power station suppliesd 7% of the homes. One solar farm might then be worth 8000 homes on nameplate value or more likely 5000 homes average. We would need between 5000 and 6000 solar farms. At the moment there are about 500.

Learning things about electric cars

 

It started when someone said that you can't tow an electric car - a consideration in a muddy festival car park field. And it turns out that for the vast majority of electric cars, they are correct. There is no neutral gear. A flat bed truck is needed. Also, the vast majority of electric cars have only one gear anyway. There's a lot of interesting stuff I need to consider here about torques and transmission.

New pylons and power lines

 

We were up close to the new T pylons in the south-west. I think they have a lower profile so might be deemed to be less intrusive. I read an article in The Guardian that makes relevant comments about the new power lines that will have to be built to achieve Net Zero. The new centres of power generation are in Scotland or the North Sea whereas the old power lines connected to large power stations in the middle of England. 

Spinning on the swing

 We wound up the swing and then it span when released.

Hooking the chains over each other pulls them in and ensures that there is a horizontal component to the tension force in the chain. There is a horizontal component in each of the pair of chains pulling in opposite directions. The key is that the way the chains are wrapped side by side, so the horizontal components are not perfectly lined up. This produces a couple, a turning moment. The swing rotates.

Lift axle

I've been noticing for years that some lorries have a retractable axle that can be carried and isn't rolling on the road. A bit of research shows that this has many different names but that "lift axle" got the best results. There is some info here. It looks like the application is mostly manual rather than automatic. The axle isn't driven - it runs freely. The decision to deploy is a balance between the fuel and tyre-wear saved by reduction in rolling friction, and the need to spread the axle loads more to meet legal limits.