Slashdot is powered by your submissions, so send in your scoop


Forgot your password?
For the out-of-band Slashdot experience (mostly headlines), follow us on Twitter, or Facebook. ×

Comment: He's totally wrong. (Score 1) 223 223

by Ungrounded Lightning (#50016313) Attached to: Bill Gates Investing $2 Billion In Renewables

When Bill Gates says:

"There's no battery technology that's even close to allowing us to take all of our energy from renewables and be able to use battery storage in order to deal not only with the 24-hour cycle but also with long periods of time where it's cloudy and you don't have sun or you don't have wind."

he's totally wrong.

For starters, there's Vanadium Redox. A flow battery (pumped electrolyte): Power limited by the size of the reaction device's electrode and membrane assembly. Energy storage limited by the size of the tanks. It's mainly used for utility-level energy storage down under (Oz or Nz, I think), because the patents are still fresh and the little startup doesn't want to license it to others. Vanadium is some substantial percentage of the Earth's crust so there's no shortage. Using the same element (in different sets of oxidation states - vanadium has (at least) 6 of 'em) for BOTH electrodes means leakage of small amounts of the element through the dilectric membrane doesn't poison the battery.

Lithum cells are already good enough to run laptops, cars, and houses, and are improving at a Moore's Law like rate. The elements are also not rare and the use of several nanotech techniques on the electrodes have drastically increased the lifetime and other useful properties. (We just had reports of yet another breakthrough within the last day or so, doubling the capacity and extending the life.) The fast-charge/discharge cells are also extremely efficient. (They have to be, because every horsepower is 3/4 kW, so even a few percent of loss would translate to enormous heat in an automotive application.) The main problem is to get companies to "pull the trigger" on deploying them - and risk their new production line being rendered obsolete before the product hits the market by NEXT month's breakthroughs.

Lead-acids need to be replaced once or twice per decade. But they have been the workhorses for off-grid since Edison's and Nikola Tesla's days, and still are today (though not for long, if Elon Musk and the five billion dollars of investments in his lithium battery plant have anything to say about it).

Nickel-Iron wet cells are a technology developed by Edison. They have more loss than lead-acids. But they literally last for centuries. If you have a moderately steady renewable source (like some combination of enough wind and a big enough windmill, enough sun and a big enough solar array, or a stream and a big enough hydro system) you'll have enough more power than you need to keep them topped off. They're just fine for covering days, or even a couple weeks, of bad generation weather, or down-for-maintenance situations. That IS what they were in at least one hydro plant I know of. (The problem is finding them: They last so long you only need to buy them ONCE, so there aren't many plants.)

That's just four FAMILIES of entirely adequate solutions. There ARE more.

So Bill is either uninformed, talking through his hat, or starting on the "embrace" stage of yet another:
  - Embrace
  - Extend
  - Extinguish

Comment: Second law of thermodynamics. (Score 2) 223 223

by Ungrounded Lightning (#50012745) Attached to: Bill Gates Investing $2 Billion In Renewables

we have a way to turn electricity directly into heat. But there is no direct way to turn heat into electricity. It has to go thru a second step of mechanical energy to spin a magnet to create electricity.

You can go from electricity directly to heat because that increases entropy. You can't go from heat to anything useful because that decreases entropy, and entropy of a closed system only increases. The best you can do is a heat engine, working off a temperature DIFFERENCE. (Some of them also work backward as heat pumps, to go from electricity to heat more effectively, by also grabbing some heat from elsewhere to include in the hot end output.)

There ARE at least two major forms of electronic heat engines - direct from temperature differences to electricity, with only charge carriers as the moving parts: Thermoelectrics (thermocouples, peltier junctions, and thermopiles of them) and thermionics (both heat-driven vacuum diode generators and a FET-like semiconductor analog of them). Both are discussed in other responses to the parent post.

Comment: Thermionics (Score 3, Interesting) 223 223

by Ungrounded Lightning (#50012607) Attached to: Bill Gates Investing $2 Billion In Renewables

TEs are ridiculously inefficient and aren't looking to be much better anytime soon

Because thermoelectric effect devices leak heat big time.

However there's also thermionics. The vacuum-tube version is currently inefficient - about as inefficient as slightly behind-the-curve solar cells - due to space charge accumulation discouraging current, but I've seen reports of a semiconductor close analog of it (as an FET is a semiconductor close analog of a vacuum triode) that IS efficient, encouraging the space charge to propagate through the drift region by doping tricks (that I don't recall offhand). The semiconductor version beats the problems that plague thermoelectrics because the only charge carriers crossing the temperature gradient are the ones doing so in an efficient manner, so the bulk of the thermal leakage is mechanical rather than electrical, and the drift region can be long enough to keep that fraction down.

Comment: Then again. (Score 1) 61 61

I got the impression from the (sketchy) article that repeater AMPLIFIERS were still needed but repeater REGENERATORS were not.

Then again - another part of the article makes it look like an additional result was that they could boost this less-subject-to-degradation-by-nonlinear-distortions signal at the start until the fibre itself was acting non-linearly, in order to get a signal strong enough to survive a much longer hop.

So it's not clear to me whether the distance was achieved by:
  - long hops enabled by strong signals, and NO amplifiers
  - longer propagation without regenaration using JUST amplifers
  - a combination of the two: Both getting long total length without regeneration AND being able to use stronger signals and thus use larger space between the amplifier-type repeaters.

Comment: but not amplifiers (Score 1) 61 61

Since the diameter of the earth is 7 926.3352 miles, this could conceivably remove any need for repeaters.

I got the impression from the (sketchy) article that repeater AMPLIFIERS were still needed but repeater REGENERATORS were not.

I.e. you still needed to boost the strength of the signal to make up for the losses. But the progressive degradation of the quality of the signal - with data from different frequency bands bleeding into other bands (especially in the amplifiers themselves) due to nonlinear "mixing" processes - had been headed off, by synchronizing the frequencies of all the carriers to exact multiples of a common basic difference-between-the-carriers frequency.

This apparently sets up a situation where the distortion products of each carrier's interaction with nonlinear processes cancel out with respect to trying to recover the signals on another carrier - much the way the modulation products do in OFDM modulation schemes. In OFDM it allows you to make essentially total use of the bandwidth. In this system it lets you use simple, cheap, amplifiers to get your signal boost, rather than ending the fibre before things get too intertwingled, demodulating all the signals back to data streams and recovered clocking, then generating a fresh set of modulated light streams for the next hop - MUCH more expensive and power hungry.

Comment: Re:Once all the data is in the cloud... (Score 1) 89 89

... government regulators couldn't possibly find financial irregularities by grabbing you documents from the cloud service provider, ...

The courts said you have no expectation of privacy one you put your data in the hands of a third party. Great! Let's convince all those "evil corporations" to store all their data in the cloud. Then the government can go after them any time they want. B-b

Comment: Romney could have won if his guys hadn't cheated. (Score 1) 292 292

IMHO Romney could have won it if his supporters hadn't cheated the Ron Paul supporters so blatantly, publicly, and sometimes violently, that they alienated, not just them, but many of the other factions of the Republican Party as well.

Many Paulites (and others) will never again vote for Romney, or any candidate supported by the Neocon machine (alias the "GOP Power Structure) or at least by a number of major figures who were involved in the corruption. The thinking is "If that's the way they treat their own party members in a primary/caucus, they can NOT be allowed to control the mechanisms of the Federal Government."

There are five states that Romney lost by substantially less than the number of people who actually voted for Paul in the primaries/caucuses, with an aggregate number of electoral votes to give him the win. If you assume that these Paul people would have voted for Romney if he'd won the nomination without massive cheating (as he probably would have) and instead sat it out (or enough other Republicans behaved that way to make up for Paulites who didn't) it would have been President Romney.

On the other hand, if Paul had managed to win the primary he'd likely have trounced Obama. He can pull support from much of the Democratic Party's base and enough of the typical Republican voters to make up for any that might have sat out HIS run.

Comment: And bacterial enzymes. (Score 1) 163 163

Because "High Fructose Corn Syrup" rolls off the tongue slightly better than "a 50%:50% ±10% homogeneous mixture of fructose and glucose with >0.5% residual corn proteins and cellulose."

Not to mention bacteria enzymes.

My personal problem with HFCS is that I'm allergic to corn, and food-grade purification processes don't clean out enough of what I'm allergic to for ANY corn-sourced food ingredient to be safe for me. (As I understand it, antibodies are THE most sensitive detectors of particular molecules / molecular sites known to man, and it only takes four molecules to trigger an allergic reaction.) Fry it (ALL!) brown and it's safe, else forget it.

But I hear that HFCS is an obesity issue because it doesn't trip the appetite regulation as strongly as sucrose, so people tend to eat more of it.

Comment: Nice but very pricey (Score 1) 1 1

by Ungrounded Lightning (#49966383) Attached to: Thieves beware: the lights are listening

$100+/bulb is VERY pricey. (Lots of LED bulbs already have TI radio/processor chips - usually the otherwise-identical ones with zigbee rather than BLE - for substantially less.

Adding a battery and related circuitry to do operate-over-power-failure is nice but not that much of a cost. Adding a speaker/microphone, a suitable processor to drive it, and some network and security software, may justify a substantial boost. But software amortizes to "almost free" over large numbers of units. So it seems to me the price point is too high. I expect this will die from competition.

User Journal

Journal: Number Five 2 2

Journal by mcgrew

I just sent off for the fifth and, I hope, last pre-publication copy of Yesterday's Tomorrows. I was sure it would be finished a month ago, but there were problems printing it due to some of the illustrations being too high of a resolution. It took a month to get the fourth printed.

"Even if you're on the right track, you'll get run over if you just sit there." -- Will Rogers