Perhaps USB-C PD might help? USB power adapters are compact and PD offers standard, useful high power DC. If the adapters become ubiquitous, you could see "USB-C lightbulbs".
You can buy PoE LED light fixtures now, which are both powered and controlled over ethernet. You buy a single PoE switch, run some low voltage Cat6, and you can power an entire floor's worth of lighting.
EEPoE (Energy Efficient PoE) offers more efficient PoE too which claims up to 94% efficiency.
Definitely a space to watch. Particularly as the cost savings of running low voltage Ethernet cable compared to high voltage electrical cable (110v) are substantial.
They tried every random thing, including putting a small real ARM server on the bloody thing to do remote control. It was back then when I first stumbled on Espressif people and Teo. They got lightyears ahead of us with all-in-one SoC.
Microsemi's exclusive EEPoE technology cuts the power losses on Ethernet cables by 50%, through the utilization of all the copper available on cable when a Microsemi EEPoE PSE IC or Midspan is used. It is 100% compatible with IEEE802.3at, and the savings work with ANY IEEE 802.3at Type 2, Type 1 or IEEE 802.3af compliant PD. In practice, devices that consume 25.5W would consume less than 27.75W, instead of the worst case 30W when a non-EEPoE PSE is employed.
So they use all 8 wires for power instead of just 4 to halve the power loss on the wire. For the worst case device that makes the 20% loss be a 10% loss.
? Must be either very low current lighting or that's some pretty beefy Cat6. I think the average Cat6 cable is only 24 gauge and that won't carry a lot of current very far.
Biggest problem tends to be accommodating the central power delivery device. Those big PoE switches run hot and loud.
I always imagined homes would migrate to 12VDC and converge electronics with RVs.
If you had AC to your house, then a rectifier for a 100V/200V DC circuit through your house, the losses wouldn't be any worse.
DC losses are less than AC losses at the equivalent voltage, because the resistance seen by DC is less than the AC impedance.
In a perfect world we'd have both AC & DC, and could use whichever was most appropriate. We could feed DC straight from the solar panels to the cell phone. But in terms of what consumes most of the power, in the typical home it's AC loads.
This isn't an appropriate comparison. Those appliances actually do useful things that need to get done so the energy isn't just wasted like it is with power supply inefficiency.
Sure a 12vdc circuit would be nice. It wouldn't be nice enough or efficient enough to be worth paying for.
I hate waste; my mains-connected smoke detectors (1% efficient) and garage door opener (15W standby) gnaw at my soul. But that's scope for improvement, not an efficiency crisis.
Those aren’t a waste, they are critical life safety equipment. If their 1% efficient power supply lasts the full 10 year lifespan of a smoke detector rather than 6-18 months like a typical LED lightbulb, I’d say that’s the appropriate level of reliability.
If every home in Australia had two smoke alarms, that means 5,600 kW of continuous and largely wasted energy consumption. I don't mean wasted in purpose: smoke alarms are essential. The wasteful part is the fact that 99% of the power going into smoke alarms goes to converting AC power to DC power.
As far as I'm concerned, that's 99% scope for improvement.
https://reductionrevolution.com.au/blogs/news-reviews/584256...
Although 15W standby for a garage opener seems excessive.
Just because generator/machine set transformers and 380/220 kV step transformers require semi-active cooling doesn't mean they're inefficient... just means that they handle a huge amount of power (MWs), so even at very high efficiencies that translates to a lot of heat in absolute terms.
Sorry, I was being a little too loose for HN. Also, I'm not an EE but I play one on the Internet :).
- A shock from a DC supply will cause heart fibrillations at lower voltage than AC, because of the way muscles receive signals from nerves
- An electrical arc from a DC line will burn continuously, while an AC arc tends to self-extinguish at each zero-crossing.
So in practice, 120 VAC or 48 VDC are the limits for household wiring.
About 20% of the world uses 110-120 V and 60Hz. The rest uses mostly 240V at 50Hz.
Although 110V is safer, the US seems to ignore many of the safety features I see used elsewhere in the world.
How that translates to deaths per million people per year comparing to similarly rich countries, I don't know.
That is opposite to my understanding. The extra shock hazard of AC vs DC was an argument used against AC power distribution back in the day. The 50V limit is to prevent shock altogether.