An object lesson in power consumption

Cariboocoot

One of the first things I disconnected at the new house here was the yard light: one of those 250 Watt mercury vapour wonders. Not only did I not like the glow through the bedroom window while trying to sleep, I also knew it was using a fair bit of power. Mostly I shut it down because the wiring was dangerous: two splices (wire nuts & tape) on single wires before it even got down the (metal) pole, where it joined to an extension cord which plugged into another extension cord, looped over to a shed and plugged into a non-exterior outlet that was outside. No GFCI breaker either.

But then I got complaints from the neighbours; it seems our yard light is the local street light, and without it no one can find their way home in the dark! Would I please turn it back on? No. And not just because I'm a mean old 'coot. I figure it runs an average of 11 hours a day, year-round. That's 2750 Watt hours per day. As inexpensive as BC Hydro is, I'm not paying for it.

Inevitably, someone (no names, please) asked if I couldn't run it off solar.
What part of "3 kW hours per day" don't you understand?
That's more power than we use at the cabin to run a refrigerator, office computer & satellite set-up, miscellaneous lights, water pump, digester pump, and the occasional zap in the microwave.

So what would it take to run this "little" light from solar? About this:
2750 Watt hours on a 12 V system (only 250 Watts - no big inverter needed) = roughly 230 Amp hours. That's a minimum 460 Amp hour battery bank, and at least 800 Watts of panel to recharge it.
But it gets worse: that's a year-round average. In Winter when our days shrink down to 6 hours and there's no "4 hours equivalent good sun" to re-charge with you'd either need 2X the panel capacity or a grid hook-up anyway! And remember, it would be burning more in Winter; possibly 18 hours a day - 4500 Watt hours! That would be 750 Amp hours of battery and possibly 2000 Watts to get it recharged in the tiny window of available sunlight.

All that for a "little" 250 Watt light.
I think BC Hydro should install a real street light, and run it at their expense not mine.
Or the neighbors should all buy solar-power driveway marker lights.:D

mike95490

Re: An object lesson in power consumption

Run the calcs, and mail a copy to each neighbor !

Or - do you really need 250W ? What about a 35W sodium vapor light ? or a CFL yard light ? so what if there is a 5 min warm up time.

solar_dave

Re: An object lesson in power consumption

mike90045 wrote: »

Run the calcs, and mail a copy to each neighbor !

Or - do you really need 250W ? What about a 35W sodium vapor light ? or a CFL yard light ? so what if there is a 5 min warm up time.

I run 2 100 watt equivalent CFL (23 watts each) on a programmable timer wall switch all night and they are super bright. I had problems with gas siphoning, from the neighbors kids teenage buddies I suspect. Not a lick of a problem since that addition.

drees

Re: An object lesson in power consumption

Cariboocoot wrote: »

Mostly I shut it down because the wiring was dangerous: two splices (wire nuts & tape) on single wires before it even got down the (metal) pole, where it joined to an extension cord which plugged into another extension cord, looped over to a shed and plugged into a non-exterior outlet that was outside. No GFCI breaker either.

But then I got complaints from the neighbors; it seems our yard light is the local street light, and without it no one can find their way home in the dark! Would I please turn it back on? No. And not just because I'm a mean old 'coot. I figure it runs an average of 11 hours a day, year-round. That's 2750 Watt hours per day. As inexpensive as BC Hydro is, I'm not paying for it.

Good on you. Personally, I am not a fan at all of night lights. Most of the time they sit there burning power and creating light pollution (remember when the starts were so much easier to see???) and it affected you directly when you were trying to sleep.

Much more effective to put security lights on motion sensors - then they only suck juice when when someone is around saving a TON of power and also minimize light pollution. The light turning on when it is pitch black is also more effective as a deterrent when it comes to scaring off intruders as well.

Not only that - but poorly thought "security" lighting is often ineffective:
http://www.schneier.com/blog/archives/2007/09/light_and_crime.html

Cariboocoot

Re: An object lesson in power consumption

I'm thinking "tea lights" now ... all along the roadside.

This is not so much a security issue as a safety one: the road is pitch black at night sometimes, and you can't see the driveways. You also can't see the curve 'til you're right on it, and too many people drive too fast. As I said, our yard light acted as a street lamp for the neighborhood. Unfortunately the community is unincorporated, so there's no Government to go to to request proper lighting. The town might listen, but will BC Hydro? I guess we have to wait 'til someone gets killed. Again.

I really posted this to show just how much power "small" loads are, especially if you intend to run them from solar. This is a "worst case scenario", since the light would only ever be on when there is no sun: 100% battery run. You only need a small inverter, but massive battery and panels to keep it going so long.

drees

Re: An object lesson in power consumption

Cariboocoot wrote: »

This is not so much a security issue as a safety one: the road is pitch black at night sometimes, and you can't see the driveways. You also can't see the curve 'til you're right on it, and too many people drive too fast. As I said, our yard light acted as a street lamp for the neighborhood. Unfortunately the community is unincorporated, so there's no Government to go to to request proper lighting. The town might listen, but will BC Hydro? I guess we have to wait 'til someone gets killed. Again.

Frankly - if they are driving so fast that their high beams do not sufficiently light up the road that they can safely and successfully navigate the road - they are driving way too fast anyway - whether or not the road is lit. Lighting the road will only encourage people to drive faster - they need to be slowing down, instead.

Cariboocoot

Re: An object lesson in power consumption

drees wrote: »

Frankly - if they are driving so fast that their high beams do not sufficiently light up the road that they can safely and successfully navigate the road - they are driving way too fast anyway - whether or not the road is lit. Lighting the road will only encourage people to drive faster - they need to be slowing down, instead.

I couldn't agree more!
It would be nice if they'd drop the speed limit on this stretch to 60 kph from 80 kph, but since people usually do 100 ... it wouldn't help much. Other similar communities do have lowered rates, btw.

I've been looking at the solar powered "garden" lights as driveway markers. Some have 200 mAh batteries, others up to 600. But the larger battery usually goes with more LED's, and they are decided lax on issuing any statements regarding how much "glow time" you can expect from a full charge. They probably would not last a full night.

icarus

Re: An object lesson in power consumption

It's amazing what you can see with no lights, if you just train your eyes, and you get used to the darkness!

Quite often, we have to return home down the lake ~10 kms either from visiting our one neighbour, or from a trip to town or away. We have no running lights on the the boat (there are no other boats on the lake to hit!) and have no spot lights on the boat. In better than 50 years I have only had trouble getting down the 10kms in the dark, and that was due to dense fog! (and that was on a Ski-do with a head light!) I can always make out some shoreline ~1/2 mile distant, and since I know where I am going it is never a problem.

The only other problem I have ever had is landing in a significant snow squall in rough weather. Turning my head light (flashlight) on did nothing but reveal the pounding snow, taking the shore away completely.

Enjoy the dark, learn the stars, and you will be amazed at what you can see!

That said, a lot of people are fundamentally scared of the dark, and think that light will give them security. I have my doubts.

T.

Cariboocoot

Re: An object lesson in power consumption

Tony;

That's true if all you have is dark. But when you introduce random house and headlights into the mixture - the dark becomes darker!

I've piloted the boat up the lake at night with no lights (they worked during the day!) and even then ... the shoreline was pitch black because the water picked up the star light. A nice sort of problem to have.

Down in the valley the sky glows all night as the city lights reflect off the permanent haze of pollution ...