EEVblog #1284 - How Bad Product Design Kills The Environment

[EEVblog]

Let's save 30 cents/unit and stuff the environment!
How can bad and cheap product design kill the environment by requiring vastly more energy generation, delivery and PF correction infrastructure?
Dave looks at the shockingly energy wasteful design of mains powered smoke alarms.

[ogden]

Mains supply have to be designed for max power. You forgot to measure consumption while alarm is on.

[langwadt]

Let's save 30 cents/unit and stuff the environment!
How can bad and cheap product design kill the environment by requiring vastly more energy generation, delivery and PF correction infrastructure?
Dave looks at the shockingly energy wasteful design of mains powered smoke alarms.

isn't 90% of the led lights BigClive take a part the same capacitive dropper and lousy power factor?

[tszaboo]

I think you should review how reactive power works. The 100MW is not generated by the wind turbine. You generate 5MW by the wind, and place a compensation on the power grid, that will generate the reactive power. It is just a big capacitor. The grid already has a bunch of inductive load, because of motors.

Here is an example of 120MVAR capacitor bank.
https://trench-group.com/wp-content/uploads/2019/07/Air-Core-Shunt-Reactors.pdf

[berniwa]

You can acutally use a depletion mode MOSFET to modify any "normal" regulator to support mains voltage.



In the given configuration, the MOSFET will reduce the drain, source current to a point, where the regulator only sees VOUT - VGSoff.
Simple, easy and cost effective solution and hv depletion mode MOSFETs are readily available.

[EEVblog]

So this is an interesting discussion, and I expected it.
I think I'm right in that ultimately at some point there has to be no free lunch here, but happy to be proven wrong.
I did simplify it in the video to highlight to potential magnitude of the problem.
#NotAPowerGenerationEngineer

[EEVblog]

I think you should review how reactive power works. The 100MW is not generated by the wind turbine. You generate 5MW by the wind, and place a compensation on the power grid, that will generate the reactive power. It is just a big capacitor. The grid already has a bunch of inductive load, because of motors.

See my comment above.

[fki82]

I think NANDBlog is right. The generator doesn't need to generate all the reactive power but only the active power + losses.
The efficiency of this power supplies is still horrible.

Is it required to connect the smoke alarm to the grid in Australia?
Here in Germany we just put a smoke alarm with a 10 Year battery on the ceiling and that's it.

[EEVblog]

Is it required to connect the smoke alarm to the grid in Australia?

For all new home and renovations, yes, mandatory. (might vary by state, don't know)

[EEVblog]

I think NANDBlog is right. The generator doesn't need to generate all the reactive power but only the active power + losses.

There is reason why commercial companies are charged in kVA. They aren't charged kW+"copper losses"

[langwadt]

https://www.cashmanequipment.com/cashmancat/media/Cashman-Equipment/generator-power-factor.pdf

[Maloxyl]

Is it required to connect the smoke alarm to the grid in Australia?

For all new home and renovations, yes, mandatory. (might vary by state, don't know)

I don't understand that requirement at all. In addition to being hardwired you have a backup-battery that has to be changed every year or two (see manual / regs) that could power the whole thing alone anyways. In addition after 10 years you have to replace the whole alarm.

Here in Austria / Germany the standard is alarms with hardwired battery - lifetime 10 years. Less hassle and probably cheaper.


Regulations: http://mfb.vic.gov.au/Community/Home-Safety/SmokeAlarms.html
Manufacturer manual: https://www.quell.com.au/download/quell-q1300-240v-photoelectric-alarm-installer-manual/

[fki82]

With a bad power factor, the current in the wires is going to be higher, which requires thicker wires, bigger transformers, bigger generators and produces more loss.
That's why power factor correction is necessary, and companies get charged extra if they don’t do it properly. It’s about compensating for the additional cost on the grid for reactive power.
In this specific case, the smoke alarm is a capacitive load.
Most machines an appliances will be inductive loads.
They are usually not compensated completely, so in reality, the capacitive load of the smoke alarm won't cause additional current on the wires to the power plant.
Because of this, only the active power should be used for calculating the energy consumption (which is still horribly high).

[Dundarave]

Given that domestic power consumption is overwhelmingly inductive (fridge motors, fans, wall-warts of all descriptions), the capacitive load of these smoke detectors might actually be the only thing in the house serving to “even up” the reactive load in the household...  I.e. I’m thinking that they may be doing the power company a favour...

[EEVblog]

They are usually not compensated completely, so in reality, the capacitive load of the smoke alarm won't cause additional current on the wires to the power plant.

Not if you suddenly added a million of them to the grid.

Because of this, only the active power should be used for calculating the energy consumption (which is still horribly high).

Nope, you can't assume the PF is corrected close to the loads(s).

[Psi]

Here's an interesting idea to keep the capacitor dropped circuit but remove all the inefficiency, and make the product last longer too.

1) Swap the primary battery for a super capacitor.
2) Only enable the capacitor dropper circuit when the super capacitor is low and needs a recharge. (Maybe using an SSR/relay)

If you only enable the capacitive dropper when you can accept all the energy into the super cap then the wasted energy is practically zero.

A capacitive dropper circuit is only inefficiency because it's always burning off a constant amount of energy based on the cap size.
Since the cap size has to be selected for the products peak current requirements you're always wasting that current even if you're not using it.

[ogden]

Here's an interesting idea

Your idea is already implemented in the chip Dave mentions in the video.

[Psi]

Here's an interesting idea

Your idea is already implemented in the chip Dave mentions in the video.

Sorry, that will teach me for skipping through the video   

[floobydust]

I changed over to mains-powered smoke alarms strictly due to the cost of ownership.
9V alkaline batteries are ridiculously expensive at $6-$7 each, per year.
A new (AC) smoke alarm costs $14, can tie into a home alarm system, and the wasted watt of heat is recovered heating the house over winter for the $0.35/year electricity.
I break even in two years and earn $6 a year afterward (each) so I can buy a new multimeter 

[ogden]

9V alkaline batteries are ridiculously expensive at $6-$7 each, per year.

BS. For 22$ you get 12pieces of 9V batteries that will last at least 2 years in properly designed smoke detector.

https://www.amazon.com/Energizer-Industrial-Batteries-Alkaline-Battery/dp/B000099SKB

[langwadt]

Given that domestic power consumption is overwhelmingly inductive (fridge motors, fans, wall-warts of all descriptions), the capacitive load of these smoke detectors might actually be the only thing in the house serving to “even up” the reactive load in the household...  I.e. I’m thinking that they may be doing the power company a favour...

most wall warts are switching supplies now, is a bridge rectifier on mains an inductive load?

[langwadt]

I changed over to mains-powered smoke alarms strictly due to the cost of ownership.
9V alkaline batteries are ridiculously expensive at $6-$7 each, per year.

you use gold plated batteries? 

[Dundarave]

Given that domestic power consumption is overwhelmingly inductive (fridge motors, fans, wall-warts of all descriptions), the capacitive load of these smoke detectors might actually be the only thing in the house serving to “even up” the reactive load in the household...  I.e. I’m thinking that they may be doing the power company a favour...

most wall warts are switching supplies now, is a bridge rectifier on mains an inductive load?

Good question, which brings to mind the impact of bazillions of idle wall-warts, compared to merely millions of AC-powered smoke detectors.

[langwadt]

Given that domestic power consumption is overwhelmingly inductive (fridge motors, fans, wall-warts of all descriptions), the capacitive load of these smoke detectors might actually be the only thing in the house serving to “even up” the reactive load in the household...  I.e. I’m thinking that they may be doing the power company a favour...

most wall warts are switching supplies now, is a bridge rectifier on mains an inductive load?

Good question, which brings to mind the impact of bazillions of idle wall-warts, compared to merely millions of AC-powered smoke detectors.

wallwarts now have requirements on no-load power consumption and PFC above a certain size

[temperance]

@EEVblog

-Can you find the surge rating of the series resistor in the cap dropper?
-Can you find any information on the capacitor being used in the cap dropper and it's expected life time or it's construction? I can see it's an X2 capacitor which a bad sign.
-Can you measure how much droop in capacitance this thing can withstand?

Perhaps the thing can withstand a very large droop in capacitance before the thing fails. So it's power consumption goes down after a while...

An app note on the lifetime of those capacitors can be found here:
https://ec.kemet.com/wp-content/uploads/sites/4/2019/10/RFI-X2-Capacitors-for-High-Humidity-Enviornments-WP1022.pdf

Vishay also has an app note detailing the construction differences between long life and low cost X capacitors. But Somehow I can't find it.

I see MOV's but no fuses.

How much energy has been wasted in producing this garbage, putting it in stores...? But who cares about that if the thing survives the warranty period?