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Comment: Solar Panel Voltage (Score 1) 582

by necro81 (#49791163) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage
Is it still the case that solar panels are wired to produce 12-V output? As I understand it, this was done historically for the convenience of interfacing with 12-V lead-acid batteries. This historical quirk has made almost everything else about solar more difficult and expensive, because it's a low-voltage, high-current architecture.

If, on the other hand, solar panels were wired to produce, say, 120 V DC output (i.e., the cells or panels wired more in series than parallel), then lots of things get easier and less expensive. All the wiring can be of much lighter gauge due to the lower current. The losses in the inverter would be lower because of lower resistive losses and more of 1:1 voltage ratio. Some components (capacitors, FETs and IGBTs) may be more expensive because of the higher voltage rating, but that is a relatively small incremental cost compared to the cost of copper.

It seems to me that a lot, if not the majority, of new residential solar installations are grid-tied with no battery attached. It seems that the system should be designed to make that easier and more efficient, rather than tie ourselves to historical off-the-grid designs. Plus, if Tesla and others are designing new style batteries for this market, they can design them for higher voltage.

Comment: Re:In other news... (Score 1) 256

by necro81 (#49734699) Attached to: Energy Dept. Wants Big Wind Energy Technology In All 50 US States
IEEE Spectrum recently ran a piece called "Lessons Learned on Along Europe's Road to Renewables". Wind, obviously, is a large component of that, and they discuss the successes in Denmark and elsewhere. However, it is tempered a bit by the technical, economic, and political challenges that are starting to become significant.

Comment: We've been infiltrated! (Score 1) 256

by necro81 (#49734649) Attached to: Energy Dept. Wants Big Wind Energy Technology In All 50 US States
The first link from energy.gov - a publication of the United States government - it providing turbine heights and blade lengths in meters?! Damn, we've been infiltrated by those metric commie bastards!

(please tune your sarcasm detectors to their optimal setting, in case you couldn't tell I was trying to make a joke)

Comment: Re:a data collection device in antarctica (Score 1) 403

so i think anything that's designed for long-term with those kinds of harsh remote and inaccessible conditions in mind, powered off of sustainable independent power, would be a good candidate for a device that would still be functioning even decades later.

It's design is probably robust for decades, but anything out on the ice that sits still for more than a few years is destined to get buried in snow, solar panels and all.

Comment: Re:High powered electric heaters (Score 1) 403

They are just a piece of wire, often embedded in some kind of ceramic. Without power and stored at a place well protected from the enviroment it would likely last for 100,000 years or more.

I think that the expected lifetime of Ohm's law is roughly the age of the universe.

Comment: Re:A nuclear power plant (and its control room)? (Score 1) 403

A nuclear power plant (and its control room)?

I would recommend reading The World Without Us, which examines what would happen to the relics of our civilization if we, humans, suddenly disappeared (i.e., not extinct via war or disease, but just hypothetically got raptured away). Nuclear power plants don't fare so well. In fact, without human attendants to control them, cleanly power them down, and then decommission the plant several decades later, there is every likelihood that some nuclear plants would experience catastrophic accidents within weeks to years that would spew radionuclides all over the countryside.

Comment: Re:That would be useless wiring weight (Score 4, Informative) 403

Before launch you have connector to which you connect a computer and you can do a self diagnose on the satellite using that connection to the on board system. There is no reason to dedicate leds and leds wiring for that especially that you will need to check for many fail conditions.

Having spun a number of boards in my career, I can tell you that it is trivial to add an 0402 LED indicator, just as an indication that the 3.3 V logic rail is powered. And because it was easiest (via inertia) to keep it in than to cut it out (even as a do-not-populate instruction to the board house) that little LED stayed in the design, even though in production no one would ever see it.

Given the complexity of most satellites, I would be deeply surprised if there wasn't at least one LED on one of those boards.

Comment: Re:1st: Who Owns the 25% least well-tuned autos? (Score 1) 395

by necro81 (#49647885) Attached to: 25 Percent of Cars Cause 90 Percent of Air Pollution

The poorest drivers probably own the lion's share of them. Individuals are likely even aware of their vehicle's condition.

You may be correct, but when I think of automotive air pollution, I think of the ass-hats in jacked up pickups that go down the highway coal-rolling Priuses. Those kinds of trucks may be shit-kickers, but many of them actually have thousands of dollars in after-market parts and modifications. They may, ironically, also be driven by very poor people who ought to prioritize their spending better, but there you go.

Comment: Re:The scale is backwards (Score 1) 53

by necro81 (#49628361) Attached to: As Hubble Breaks a Distance Record, We Learn Its True Limits

Note TFA has a redshift(z) scale that is backwards. They have z=1 at 6 billion years, and z>20 at 200 million years.

I puzzled over that for a moment, too. What the time scale shows is age of the universe, or (as the scale is labeled) years since the Big Bang. So z>20 = universe at 200 million years old, not years ago. It's confounding and, to my eyes, counterintuitive, but perhaps that's how cosmologists work.

Comment: Re:Water Resistance? (Score 1) 113

Most every GPS watch produced by Garmin, Suunto, Polar, etc. has exposed gold contacts on the back face or edge for charging and syncing (usually over USB). Such watches are used by active people doing sweaty activities in all kinds of conditions: triathletes, hikers, bikers, etc. Gold contacts embedded in plastic does not present a water ingress problem (nor, except for a few isolated cases, adverse skin reactions). Doing it properly requires good design and manufacturing control, but Apple has made a brand out of doing just that.

Comment: Re:Gamechanger (Score 1) 514

by necro81 (#49610899) Attached to: Tesla Announces Home Battery System

Contrary to some peoples belief: The sun still exists during winter. Panel efficiency falls by half during cloudy weather, but you will still get some power. Just means you pull more from the grid during winter.

Actually, panel efficiency (Watts of electrical output divided by Watts of insolation) tends to increase in winter, because photovoltaics are more efficient when cold (conversely, the efficiency falls when the solar cells are hot). The output of the panel will fall in cloudy weather, because the total insolation will be less, but the efficiency may well increase.

Comment: Re:Talk about creating a demand (Score 1) 334

by necro81 (#49567435) Attached to: Why Our Antiquated Power Grid Needs Battery Storage

We have to spend billions to upgrade the grid, to handle "Green" power sources that are more expensive than their competitors

Perhaps you haven't noticed, but the U.S. power grid has been having all manner of problems as it is: single-point failures that affect whole cities or entire regions, mismatches between supply and demand that allow Enron-style speculators to manipulate markets, deferred maintenance tallying tens or hundreds of billions of dollars, externalities associated with conventional generation sources that aren't properly taken into account (e.g., nuclear and fly ash disposal).

And those are the problems that we have today, with the grid as it presently exists. Even if no further renewables were added to the grid and Tesla closed up shop tomorrow (both of which are miniscule sources and sinks compared to the grid), we would still need to invest hundreds of billions just to keep things from getting worse. If we're going to gradually rebuild the grid, we should be rebuilding it sensibly: for increased robustness, efficiency, and flexibility. Yes, that means that it can also accommodate renewables and electric vehicles, but that's a secondary motivation.

The biggest difference between time and space is that you can't reuse time. -- Merrick Furst

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