Follow Slashdot stories on Twitter

 



Forgot your password?
typodupeerror

Comment: Re:Will This Fight Ever End? (Score 1) 500

by dwywit (#49796505) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

240 watts will run a LOT of LED lights. I'm typing this by the light of a 14 watt drop-in LED - so I could run 17 of those off a single cable run and not exceed the cable's load rating.

It's not about replacing every AC item with a DC equivalent, it's more to do with replacing low-load AC items such as lights, phone and laptop chargers, etc with DC, where there's less conversion losses.

Comment: Re:We're planning a 24V DC hybrid system (Score 1) 500

by dwywit (#49795667) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

Sounds good. I thought our system would be compromised by high trees in the west, but an audit showed otherwise. The auditor used a special data logger - place it face up on the center of the panel array, it logs lat and long, then uses a small fisheye lens to take a picture of the sky from the panels' perspective. It then processes the data in the picture to calculate an efficiency rating. I think it considers blue sky and cloud as a plus, and anything dark, such as a tree, to be a minus. It also takes into account that daily insolation forms a bell-curve or sine-wave shape due to the changing angle of the sun's rays across the flat plane of the panels, so that an obstruction near the eastern or western horizons isn't nearly as important as an obstruction in the northern horizon (that's for the southern hemisphere - if you live in the northern hemisphere you'd be wanting to remove obstructions in the southern skyline). Our situation was given a 94% efficiency rating.

BTW, what sort of compressors are in your fridges/freezers? The Danfoss 24VDC compressors are great.

Comment: Re:Copper wiring. (Score 1) 500

by dwywit (#49795613) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

Nobody's really suggesting that DC could replace AC completely, but you can run lighting,laptops, and even refrigeration off DC, and it doesn't have to be expensive. You have to run more copper, but with your example, you could install an additional run of #14, or even two or three additional runs per room, to supply 24 VDC lights. Standard domestic AC cable is so cheap, you wouldn't even consider special DC cable. Just make sure that no DC circuit carries more load than the cable is rated for. That shouldn't be a problem if you're only using it for lighting and other small loads like phone and laptop chargers. And if you've got lighting and refrigeration on a supply that can be isolated from the grid, i.e. supplied by a battery, won't it be nice to have that lighting and refrigeration when the grid goes down?

Comment: Re:Too low: don't forget the power requirements! (Score 1) 500

by dwywit (#49795479) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

Retro-fitting a house would be expensive, but new houses wouldn't cost a great deal extra. My place was dual-wired with the same cabling (see post above). It's the design that's important - don't let any DC circuit carry more current than the cable is rated for, i.e. 10 amps. Sure, you've got to run more circuits, perhaps a single circuit can't service more than 3 lights, but standard AC cabling is CHEAP, vs. dedicated low voltage cable.

The low voltage circuit isn't regulated, so it varies throughout the day from 24 - 30 volts, but halogen and LED lights are pretty tolerant, and the fridge doesn't seem to care - it's been running on variable voltage for >20 years. I *could* install some gear to regulate the circuit to ~25 volts, but I don't think it's necessary.

Comment: Re:Will This Fight Ever End? (Score 1) 500

by dwywit (#49795427) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

It's not hooey. I've got 2 circuits - one for 240VAC, and another for 24VDC. The cabling is identical, i.e. normal 240VAC live + neutral + earth, 10-amp. The low voltage circuit uses the same cable, but doesn't use the earth wire, and the individual circuits were designed to make sure no more than 10 amps were possible on any outlet. The low voltage system is used for lighting (although 24 volt light bulbs are rare and expensive), and a couple of 24 volt power outlets, one of which is used for refrigeration - a normal fridge converted to use a Danfoss 24 volt compressor.

There are more drop-in DC LED lights these days, and they can take 8-30 volt input, so I'm gradually replacing the halogens with LEDs.

There's a good reason to use 240VAC cabling on a 24VDC circuit - even though you have to install 3-4 x runs, 240 cabling is cheap, and 24 volt cabling is not cheap.

Conversion losses are an issue - the inverter runs about 85 - 95% (better at higher loads), and the batteries (lead-acid) are also about 90% efficient, i.e. you need to put about 10% more back in than you take out - so you just up the PV numbers to account for that.

Comment: Re:Republican Hypocrits (Score 2) 98

by dwywit (#49760473) Attached to: TPP Fast Track Passes Key Vote In the Senate, Moves On To the House

Yeah, then there's all that BSE nonsense that we in Oz are mercifully free of. We don't want anyone else's beef, we have enough. Trade should NEVER override biosecurity concerns.

A report on the ABC news (www.abc.net.au) yesterday tells of the carrot and stick approach taken by the US - "let us export our beef to you or you won't get access to our domestic sugar market".

Our situation requires very careful consideration - we have a reputation for disease-free agricultural produce. Just about every country that wants access to our markets promises that none of the diseases affecting their own products will ever make it into the wild in Australia because reasons. We don't want NZ apples, we don't want asian seafood or bananas, and we don't want US beef - although some of those things are already here.

It's true that protectionism isn't healthy long-term, but there are valid reasons to ban the import of some items. We don't want to face the consequences of the (for example) banana industry being devastated by imported disease.

Comment: Re:This isn't a question (Score 3, Informative) 620

by dwywit (#49760393) Attached to: Ireland Votes Yes To Same-Sex Marriage

Milestone might be the wrong word, but this result stands out. The citizens stood up to the catholic church, and reminded the clergy about the principle of separation of church and state.

The church's arrogance has come back to bite it, as people now see through the hypocrisy.

Well done, my (distant) Irish relatives.

Comment: Re:It may not last. (Score 1) 66

by dwywit (#49749081) Attached to: Australian ISP Offers Pro-bono Legal Advice To Accused Pirates

I used to think that about Westnet, at least. A few years ago, you'd call tech support, tell them what sort of internet connection you had (ADSL, Cable, satellite, etc), and you'd get switched to a call centre located in Australia staffed by people who didn't have difficult-to-understand accents.

Westnet was very popular with remote/rural users because their satellite was good, and the satellite tech support was good - outstanding, actually.

My most recent tech support call to westnet gave the usual "we are experiencing a high volume of calls, we'll get to you in approximately" .....wait for it... "forty-six minutes"

Get fucked, westnet. I know Telstra/bigpond are the big bad guys, but I've never waited longer than 20 minutes on the queue, and it's usually about 5 minutes or less.

P.S. I agree about dodo.

Comment: Re:Speaking as a former yearbook adviser (Score 2) 379

by dwywit (#49746557) Attached to: Student Photographer Threatened With Suspension For Sports Photos

It makes you wonder if they've had that opinion from their own advisor, and realised they might have to pay the student to be able to use the photos in their yearbook - so they try to bully him into a deal to use the photos for free. Threaten first, to frighten him, then back off with a new deal - "You sign the yearbook publication rights over to us, and we'll forget about the lawsuit"

Comment: Re:Camer was owned by the school (Score 1) 379

by dwywit (#49746523) Attached to: Student Photographer Threatened With Suspension For Sports Photos

"The school owned the camera he used. Therefore all work from that camera belongs to the school. If he had used is own camera, then they are his to keep.
Just like in the work place, any personal data on company computers used on company time belong to The Company and not you."

You're new here, aren't you?

My computer can beat up your computer. - Karl Lehenbauer

Working...