Changed wind conditions - A question to pilots in Sydney

[skippydiesel]

Back to the Camden weather question - a completely non scientific & subjective observation:

 

In my area, due west of Camden, the prevailing winds used to be from the west and south west, hence all the older farm buildings have their openings/doors on the north/east side.

 

It would seem to me that the prevailing winds are now from the east.

 

The BOM would probably confirm/dispel this yokals observation.

 

 

[facthunter]

There may be some confusion about reflection and the surface being warmed by absorbtion of the heat energy. The more it's reflected the less it will heat. the surface. Light and heat travel without heating the gas they travel in. (more or less). If the surface is heated that heat energy will cause some convection to occur ( hotter (and less dense) rising gas by contact and turbulence) Treed areas have another factor They add moisture from transpiration of the leaves. Nothing like as much as from lakes and oceans though where the major moisture input comes from that generated big cumulus clouds especially in the tropics where warmer air carries more moisture. ( Called "tropical Maritime" air mass).

 

IF you are on a yacht during a sunny day you will get much more burned than if you are in grassy paddocks that reflect less radiated heat back. Same with snow covered ground where you need good sunglasses because of all the light around you causing "glare". Nev

 

 

[old man emu]

The effects of colours on composite materials is well known in aviation. That's why Jabiru warns owners against using anything but white for large areas of their aircraft. I suppose that if you wanted a snazzy paint scheme you could do it in the undersides of the plane, a la warplane camouflage.

 

 

 

[GyPySusi]

My wife has said, "You can tell this kitchen was designed by a man", of every house my wife and I have lived in.Our current house has the hot water service 10 or more metres from the area closest to the kitchen, laundry and en suite. There is a perfect alcove outside each of these rooms where a water heater could be placed.The only bathroom close to it is the family bathroom which, being Darby and Joan, we don't use. We waste heaps of water waiting for hot water to reach the kitchen sink or en suite shower. (Wash in cold water).

And I guess they skimped on not lagging the pipework. ?

 

 

[old man emu]

And I guess they skimped on not lagging the pipework. ?

Naturally. Built to a price, not to a standard.

 

 

[Raytol]

Hi OME,

 

The sewage works at Camden was always good for a thermal in winter!

 

Ray

 

 

[Head in the clouds]

Black absorbs all colours of the spectrum and infra red as well. A black object like a car gets very hot in the sun, while a white or polished aluminium one will not absorb anything like as much heat.. The same applies to radiated heat from bushfires . Dark houses are not good for that situation.. Nev

Interesting thing that, about the polished aluminium and white paint ...

 

I had a large aluminium boat I used for my business in the Kimberley. Initially it had carpeted decks, the idea was to keep them cool, we even wet the carpet to help cooling by evaporation.

 

The sand and salt entrapped by the carpet quickly caused corrosion to get a hold so the carpets came off and I had the decks restored by polishing, I figured the polishing would keep them cool too. It didn't turn out to be the case, by 10am the decks would be so hot it would sear the skin off your feet if you didn't wear footwear, and even with thongs on your feet would get unbearably hot.

 

So - all traffic areas got painted white and non-traffic areas got mainly matt black paint to cut the glare. The white areas remained cool even on the hottest days, and the black areas only got warm. It was just basic two pack epoxy normally used for painting the inside of water tanks, so nothing fancy with insulating material in it or anything like that.

 

So - in my experience even black painted aly stays far cooler than polished aly for some strange reason.

 

I'd still have a white house roof rather than black.

 

 

[facthunter]

At Adelaide University when a friend of mine was employed there they assessed all these factors. some time ago. The paper should still be about.

 

Not only colour but the finish of the surface made a difference. Matt finish and dark gave out more heat (cooled quicker). Polished silver holds the heat longer. (Teapot).

 

Black appears black because it absorbs all colours, reflecting none. White is white because it reflects all colours. If you aim a colour onto a white surface it reflects THAT colour as that is all there is to reflect.. Red is red because it reflects only red.

 

If you get a disc with the three primary colours and spin it it will look white. A glass prism will produce all the visible rainbow colours from white light. (infra red, HEAT) Red orange yellow green blue indigo violet (ultra violet). Nev

 

 

[Yenn]

I don't know why painted aly stays cooler than polished, but I do know that black gets hotter than other colours in most places. You can tell black tiles from white tiles on the floor of a swimming pool by the greater heat in them, even though there is water in contact with them. They must heat up quicker than the water can take the heat away.

 

 

[DenisPC9]

Naturally. Built to a price, not to a standard.

In NSW all housing built since at least 2011 has had to meet BASIX standards. Mine in Tenterfield, owner built in 2012/13 had to have a light coloured roof.

 

I don't know what Zone the Sydney Basin is classified as.

 

 

[facthunter]

Disaster zone? Used to be God'zone country. Nev

 

 

[DenisPC9]

Disaster zone? Used to be God'zone country. Nev

True, during my north/south and south north treks, I avoid it like the plague.

 

 

[facthunter]

I used to live there in the early 60's. It had a certain charm about it. It's a great piece of real estate. A young student was robbed down here and He was living in his van in a street somewhere.. He said Sydney had become unfit for Human habitation and that was quite a few years ago, and I don't feel it has improved. myself. Sydneysiders are not keen to move though. They are very loyal to the place and take the Sydney-Melbourne thing very seriously. There has always been a lot of rivalry since the early days. I regard it as a bit of a joke especially if some football event is happening between the two tribes.. They drive OK because they have to. You wouldn't survive a day if you didn't.. Better road manners than down here. Nev

 

 

[coljones]

I used to live there in the early 60's. It had a certain charm about it. It's a great piece of real estate. A young student was robbed down here and He was living in his van in a street somewhere.. He said Sydney had become unfit for Human habitation and that was quite a few years ago, and I don't feel it has improved. myself. Sydneysiders are not keen to move though. They are very loyal to the place and take the Sydney-Melbourne thing very seriously. There has always been a lot of rivalry since the early days. I regard it as a bit of a joke especially if some football event is happening between the two tribes.. They drive OK because they have to. You wouldn't survive a day if you didn't.. Better road manners than down here. Nev

Ah Nev, you have to live here to truly appreciate Sydney. People from Melbourne and football supporters just don't get it. There might be a hundred thousand or so Sydneysiders who give a stuff about football or cricket, the rest of us don't give a damn (or about Victoria generally)

 

 

[Old Koreelah]

Interesting thing that, about the polished aluminium and white paint ...

When I studied solar design in the 70s I discovered that glossy white stays a couple degrees cooler than shiny al.

 

In NSW all housing built since at least 2011 has had to meet BASIX standards...

... And a better name for those standards you'd not find. The building requirements were watered down so much that passive solar design barely gets a mention. The result: thousands of monotonous dark coloured brick veneers crammed into little blocks.

 

 

[coljones]

When I studied solar design in the 70s I discovered that glossy white stays a couple degrees cooler than shiny al.

... And a better name for those standards you'd not find. The building requirements were watered down so much that passive solar design barely gets a mention. The result: thousands of monotonous dark coloured brick veneers crammed into little blocks.

There will be some incident heating from both radiation and ambient heat.

 

Highly polished aluminium has no insulating layer so when the surface heats up it conducts into the Al mass. Painted surfaces are, usually, highly non-conductive and surface heat just sits there and get re-radiated rather than being conducted through to the substrate.

 

 

[spacesailor]

My neighbor has redone his house. "bagged & painted" banana yellow!.

 

spacesailor

 

 

[facthunter]

Got the paint from where He works? Nev

 

 

[Head in the clouds]

When I studied solar design in the 70s I discovered that glossy white stays a couple degrees cooler than shiny al.

My experience with the boat was far more than a couple of degrees.

 

On a hot sunny, summer's day in the north I would estimate that the shiny aly used to reach 65C or more, it was literally too hot to touch for more than a second or two or you would get a burns blister. For example, it used to get way hotter than a black bitumen road at midday in the north. we used to walk around without footwear a lot up there and the soles of the feet became pretty tough, so you could cross a road without much discomfort but certainly not walk on the deck unless you threw buckets of water on it first.

 

After painting, the white areas used to be not much warmer than blood temperature, perhaps around a max of 45C, you could certainly walk on them with bare feet for a while before your feet became uncomfortably hot. The black areas were a little hotter, perhaps 50C and you didn't want to wait around on that for too long without footwear.

 

This has made me curious now, I'll make up three samples of aly, polish one, paint one black and one white and see what temperatures they reach in the sun. I think ColJones probably has a point about the insulating effect of paint regardless of its colour.

 

 

[facthunter]

IF you want to take the guesswork out of this I suggest someone contact the Adelaide University where they have done all the work. Nev

 

 

[Old Koreelah]

IF you want to take the guesswork out of this I suggest someone contact the Adelaide University where they have done all the work. Nev

True Nev, but nothing stopping us conducting our own experiments.

This topic is of particular I interest to me because my house roof will soon be due for a repaint. When I built the place in the early 80s I made a compromise between most efficient (glossy white) and blending in with nearby trees, so I chose mist green. The bulk insulation available at the time has long since collapsed, meaning my solar house no longer performs as if I have aircon. As a result, I plan to replace roof and wall insulation and perhaps even repaint with gloss white.

 

 

[facthunter]

Life is to short to reinvent the wheel. Also there are nowhere near enough hours in the day for me to finish everything I have on my plate. I must be very disorganised.. I know they did a lot of work on this very subject, so why not reference it? It takes the guesswork out of being close.. I understand Jabiru won't put dark colours on their plane for temperature reasons. Strength of the fibreglass.. Nev

 

 

[old man emu]

This topic is of particular I interest to me because my house roof will soon be due for a repaint. When I built the place in the early 80s I made a compromise between most efficient (glossy white) and blending in with nearby trees, so I chose mist green.

An interesting choice you made there.

 

Why are trees green? Because

 

The colours of the visible light spectrum are: ROYGBIV, which puts green at the mid-range.

 

Pigments absorb light used in photosynthesis

 

In photosynthesis, the sun’s energy is converted to chemical energy by photosynthetic organisms. However, the various wavelengths in sunlight are not all used equally in photosynthesis. Instead, photosynthetic organisms contain light-absorbing molecules called pigments that absorb only specific wavelengths of visible light, while reflecting others.

 

The set of wavelengths absorbed by a pigment is its absorption spectrum. In the diagram below, you can see the absorption spectra of three key pigments in photosynthesis: chlorophyll a, chlorophyll b, and β-carotene. The set of wavelengths that a pigment doesn't absorb are reflected, and the reflected light is what we see as color. For instance, plants appear green to us because they contain many chlorophyll a and b molecules, which reflect green light.

 

 

Optimal absorption of light occurs at different wavelengths for different pigments. Image modified from "The light-dependent reactions of photosynthesis: Figure 4," by OpenStax College, Biology (CC BY 3.0)

 

Each photosynthetic pigment has a set of wavelength that it absorbs, called an absorption spectrum. Absorption spectra can be depicted by wavelength (nm) on the x-axis and the degree of light absorption on the y-axis. The absorption spectrum of chlorophylls includes wavelengths of blue and orange-red light, as is indicated by their peaks around 450-475 nm and around 650-675 nm. As a note, chlorophyll aabsorbs slightly different wavelengths than chlorophyll b. Chlorophylls do not absorb wavelengths of green and yellow, which is indicated by a very low degree of light absorption from about 500 to 600 nm. The absorption spectrum of β-carotene (a carotenoid pigment) includes violet and blue-green light, as is indicated by its peaks at around 450 and 475 nm.

 

So, the best choice for a cool roof colour could well be Misty Green.

 

 

[spacesailor]

Bugger:

 

Just had my roof repainted a brown colour, with-out micro-spheres.

 

Next door is done in slate-grey.

 

spacesailor

 

 

[coljones]

Bugger:Just had my roof repainted a brown colour, with-out micro-spheres.

Next door is done in slate-grey.

 

spacesailor

If you put PV or hot water collectors on all the illuminated space on your roof you don't need to agonise over colour - unless you are concerned about the opinions of the man on the moon.