Posted on 02/23/2015 3:18:00 PM PST by NormsRevenge
Tokyo (AFP) - Energy-saving LED traffic lights seemed like a cool way to cut back on electricity costs, but Japanese police said Monday they might just be too cool -- because they don't melt snow.
Light-emitting diodes (LEDs) account for around 45 percent of all of Japan's stop-and-go signals ..
But in wintery northern Japan the lights have encountered a problem -- drivers can't see them because they don't get warm enough to melt accumulated snow.
Akira Kudo of Aomori Prefectural Police said snow has to be removed manually between December and mid-February during blizzards.
"We don't have enough staff members to remove snow as more and more LED lights are being introduced," he said.
(Excerpt) Read more at news.yahoo.com ...
“We have LED traffic lights and I’ve never noticed any snow buildup and we have no shortage of snow”
That’s because we use thermostatically controlled heaters to keep the temperatures high enough to melt snow.
“IIRC Back in the 90’s there was some experimentation with High voltage DC transmission lines. One of the problems was that they did not get hot enough to keep ice off them.”
The same amount of heat is generated in a wire with dc as with ac.
It’s interesting how different colors affect people differently. Blue LED’s do not bother me. Some of the red LED tail lights are outright offensive. Cadillac comes to mind, or at least the older models among the first to use LED’s.
It’s the new bulbs in existing equipment, as Northern munis in the US found out some years back, and heating units were retrofitted.
It's what happens when you have non-engineers making engineering decisions.
Murphy’s Law and The Law of Unintended consequences.
We have LED traffic signals which cannot be seen at low sun angles. The bright morning or evening sun outshines the output of the lamps and makes the signal nearly indistinguishable for east and west facing lights.
Are you by any chance epileptic? People with epilepsy havr been shown to be susceptible to certain types of strobe lghts. Under certain conditions strobes will send epileptics into seizures.
CC
Been a while since I studied any of this but as I recall the capacitive correction for AC lines increases line current. I also think that given equal size wires AC will see greater impedance due to skin effect. Finally I believe the DC transmission is done at higher voltages than AC which decreases the line current and thus the heat losses.
My original statement comes from something I read in college and I think that engineers used to sizing cable for AC oversized the cable in DC experiments and thus had icing problems.
Ditto.
Actually, the heat would be different in a pure DC system -— no loss to reactivity. However, it appears there is a direct relationship between DC current and ice formation, Google is your friend. But I did find this at the top of the search results which looked interesting:
http://www.sciencedirect.com/science/article/pii/0165232X81900276
“Finally I believe the DC transmission is done at higher voltages”
Where you could use higher voltages if you chose to, it’s very difficult and expensive and inefficient to convert high DC voltages back to AC. With AC it’s easy...
I don’t know much about LED traffic lights, but I guarantee these don’t have any problem melting snow. The two pics that show the cast aluminum heat sinks are the size of a manhole cover and about three inches deep.They have no shortage of heat.
http://www.optilume.net/
What, can’t hook the boiler up to a radiator or something?
1.3 seconds how did you determine that
Very true. Did some googling and the only places DC transmission is implemented commercially is for undersea transmission. It also appears that the greens are trying to push it for wind farms since they generally are in the middle of nowhere and produce DC that has to be converted at some point anyway.
No... not epileptic. I have known 2 women that were photosensitive... one would run away (literally) from the light fron CFLs because she would start reacting to the light negatively... CFL light bothers me only slightly... it’s just an odd spectrum, I guess.
With the LEDs, what I am talking about is a specificly disorientating light... just like a “puke light”...
Just like on all government induced energy abortion schemes... the cost benefit chickens are coming home to roost. O d’oh
I recall my Great Uncle, who had spent time with a large engineering firm on a project in Africa, talking about a DC transmission line from a hydroelectric plant to a smelting operation or some such thing... it was a process that utilized DC... perhaps electrolysis depositing copper or some metal trough galvanic action or what have you.
Gyro Gearloose was a character in some of the old Donald Duck comics. He is famous for inventing the Gloom Light. It made light places dark.
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