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Comment: Re:The utilities have reason to be upset (Score 1) 506

by DaChesserCat (#49594121) Attached to: Tesla Announces Home Battery System

"Because the transformers which convert distributed power (typically lower frequency and higher voltage) to the household power (60 Hz / 240 VAC split-phase) are made to work efficiently, one-way. Going the other way, they are considerably less efficient."


Everything on a power grid operates at exactly the same frequency. DC interconnects and other exotic technology aside, it is one gigantic synchronous machine. If load increases faster than supply the frequency of the entire gird slows down a tiny amount, as supply increase and load drops, the frequency goes up a tiny amount. Supply is continuously adjusted to keep the frequency stable. It is like a train. Locomotives tend to speed it up, wagons tend to slow it down, but it is all going at the same speed.

The POWER required has to match, input to output. On that count, I will agree with you. In that regard, it's synchronous. And if I want to grid-tie an inverter, the inverter must be able to match voltage, frequency and phase to what is being supplied to the house. And yes, when you change the load applied to an AC generator, the frequency will vary slightly, but they have feedback mechanisms on those to keep frequency within a very narrow range. But the electricity reaching my home is coming from multiple power plants; if this one varied frequency significantly, it would throw it out-of-sync with that one, hence the feedback and regulation of same.

May I direct your attention to this article? I know for a fact that the rural electrical coop, to which I'm attached, is sending out well over 1 kV to the transformer outside my house. The transformer is converting it to 240VAC 60 Hz split-phase, and it's compensating for the fact that the 2, 120 VAC channels in my home are not perfectly balanced. So the transformer is fairly sophisticated, in that regard. But sending 240 VAC split-phase long distance is going to require some VERY thick lines to avoid resistance losses. They avoid this by transmitting very high voltages (some places, over 1 megaVolt) and keeping the current down. That minimizes transmission losses. The distances involved STILL get some significant losses, but they'd be FAR worse if they were transmitting 240 VAC, long-distance.

Comment: Re:Batteries (Score 1) 506

by DaChesserCat (#49593921) Attached to: Tesla Announces Home Battery System

It's about GBP30-40 for a 100Ah 12V car lead-acid battery on a random site. These are mass-produced, cheap and easily available. Granted that they are heavy and large, but... scaling up... that's 1.2KWh alone. We'd only need ten car batteries to match it. That's GBP300-400.

Why, then does it cost the equivalent of nearly $3,500 (GBP2200) for the same here?

Sure, we allow leeway for different voltages (necessary for high-current loads, etc.), different technologies, deep-cycle, etc. but... that's a five-to-seven-fold increase over what we're using now for quite basic solar, wind, etc. power storage and can be obtained from any garage. And 10 car batteries aren't prohibitively large, expensive, difficult to handle, etc.

With 10 year warranty and 2KW peaks? That's way within range of such a pack. Hell, stick a decent split charger / inverter on the end, one designed for home use, and it still comes nowhere near the price of this home battery.

Is my maths wrong? Have I missed something? Quite what are we trying to sell here apart from an overpriced battery and some electronics on either end of it?

It's one thing to sell a battery. Musk is selling the complete package:

  • battery
  • rectifier and inverter, such that the battery can interface to the AC power in the home
  • charge controller, such that rectified DC power can go into/out of the batteries without overdoing it

The lithium batteries he's using aren't exactly cheap; you're quite right that lead-acid batteries are cheaper. But the electronics needed to interface the batteries to the home add considerably to the price. And a good charge controller, with lithium batteries, will get a lot more charge/discharge cycles, meaning it will last a lot longer than lead-acid batteries.

IIUC, he's going for a system which will work, reliably, mostly invisibly, for over a decade. That takes some engineering. To make a battery last longer, you typically only discharge it part of the way. Let's say you go for 80% Depth of Discharge. That means you need 1.25 x as much battery capacity but you will get a lot more charge/discharge cycles out of it than 100% (that will kill a lithium battery, typically in < 100 cycles). Going to 66% DoD will require 1.5 x as many batteries but give you considerably more charge/discharge cycles. No word on what DoD level he's charging/discharging the batteries.

I have a Camry Hybrid. It has NIMH batteries. The system does about 25% DoD, meaning that the batteries really don't store much. But they last and last and last.

Comment: Re: The utilities have reason to be upset (Score 1) 506

by DaChesserCat (#49593171) Attached to: Tesla Announces Home Battery System
They don't care. But in the Court of Public Opinion, where they need a win if they're going to get what they want, that pushes a LOT of people's buttons. If I believe that Climate Change is a hoax, PV is regarded as a waste of money. The notion that I, who do NOT have PV on my home, may be subsidizing the grid for someone who does ... So they play that card.

Comment: Re:The good news is... (Score 1) 210

I don't necessarily think of it as being beyond your abilities as much as outside of the scope of your abilities; is managing inherently more difficult than developing? For some people sure, but I think perhaps looking at the career ladder hierarchically is part of what leads us into this. My boss is not a great coder (he started out coding) but he is a great negotiator, salesman and organizer. It takes all sorts, right?

I don't know that it's inherently more difficult. It IS, however, a very DIFFERENT skillset. And just because I'm good at communicating with a computer (programming) doesn't mean I'm good at communicating with management. Indeed, if the Programmers' Stone is to be believed, programmers and managers are very different in how they comprehend stuff, not to mention how they communicate.

The truly gifted can speak both languages. Most of us speak only one. And we don't even realize there IS another way to comprehend/communicate. If/when we do, though, it result can be wonderful.

IMHO, the things every programmer-promoted-to-management needs to know are found in that link and in The Mythical Man-Month. I, routinely, run into situations where management still hasn't learned the lessons from that book. And life for me, as a programmer with ZERO interest in going into management, would be so much better if they would learn from that tome.

Comment: Re:Why? (Score 1) 108

by DaChesserCat (#49592667) Attached to: Messenger's Mercury Trip Ends With a Bang, and Silence
Save it for what?

To try to bring it home to Earth? Where we have no means to recover it and bring back to the the surface? Even if we did, to put it in some museum, so elementary school kids on a field trip can look at it and go "whatever?" After it's been exposed to years of hard radiation in space, closer to the Sun?

Seriously. Save it for what? Better to let it finish it's job and become its own monument. Maybe, someday, another probe will get to see it. We sure as hell won't.

Comment: The utilities have reason to be upset (Score 5, Informative) 506

by DaChesserCat (#49592597) Attached to: Tesla Announces Home Battery System
Many of the utility companies, such as the ones in Arizona and Hawaii, are griping about people adding solar PV to their homes. These people have, typically, used Net Metering; any power they produce in excess of what they consume at any moment is fed back into the grid and, when their demand exceeds their supply, they draw from the grid. The utility company gets to "reimburse" them for the power they contribute. In some areas (California), 1 kWh contributed during peak hours = > 1 kWh they can withdraw during off-peak hours. But that's pretty generous; most power companies don't even like 1 : 1.

If you put enough PV on your home, you can eliminate your electric bill. At which point, many utilities argue, the costs of maintaining the grid (that's rolled into your electric bill, but not as a separate line item) are covered by the less-wealthy. The poor are subsidizing the grid for the wealthy, they argue. And they argue, further, that they should be able to charge people who are using Net Metering even if they ARE producing as much power as they're consuming.

Where I live, I pay a monthly connection charge ( < $20 / month) + $0.085 / kWh. In short, my electrical co-op breaks these out as separate line items on the bill. Even if I put in enough PV to go Net Zero, so long as I'm connected to the grid, I'm at least paying the monthly connection charge. The Arizona utility wanted a connection charge / kWh installed PV, to the point that the homeowners who installed the PV ended up paying the same, without or without the PV. In short, they wanted to eliminate any incentive to add PV and connect to the grid. They did get approval for a connection charge / kWh installed, but it was a fraction of what they wanted.

In Hawaii, where power is routinely $0.39 / kWh (it's made, largely, from imported petroleum), solar PV and Net Metering are so widespread that entire neighborhoods are producing excess power during the height of the day. It's to the point where HECO gets to veto whether or not you can add PV to your home; you have to get permits from them and they're getting harder to acquire. Because the transformers which convert distributed power (typically lower frequency and higher voltage) to the household power (60 Hz / 240 VAC split-phase) are made to work efficiently, one-way. Going the other way, they are considerably less efficient. If you are a net producer and your neighbor is a larger, net consumer, you're supplying your neighbor and the local transformer simply converts less power going into that neighborhood. When the entire neighborhood is a net producer, the transformer has a problem. So they limit how much power can be produced in each neighborhood.

I used to think this was all about the power/utility companies trying to defend their bottom line. That's still part of it, but I've come to realize there are technical reasons, too. Installing efficient, bi-directional transformers would require:
  1. installing a second, bi-directional transformer
  2. taking down the power to an entire neighborhood while they switch over
  3. decommissioning and moving the old transformer

at considerable expense. And that latter part, well, you KNOW they're not going to let their executives and/or shareholders eat that cost. And many utilities are regulated, such that they have to get approvals for rate increases. Which aren't easy to get. So there's technical reasons AND financial reasons for the utilities to grip.

Put a battery pack on your home, like one of these. Get an inverter which feeds excess to the battery and NEVER exports to the grid. The power company loses their only technical reason to gripe, because you are no longer doing Net Metering. At that point, it's all about the Benjamins.

Indeed, if you get to the point where your home is truly Net Zero, long-term, you can go completely off-grid. At which point they no longer have a say in the matter.

Comment: Re:WTF? It's Methanol (Score 1) 481

Methanol is part of the process. But it's not the end of the process.

Gasoline and diesel aren't good for you, if you get physical exposure to them. Methanol makes them look like water, by comparison. There's a reason why very, VERY few places use methanol as a fuel. It's a potent neurotoxin, very carcinogenic and exposure to the vapors from it can cause permanent blindness.

They create methanol, as an intermediate step in the process, but they process it further to make it into longer-hydrocarbon-chain fuels. The main component of diesel is one of them. Not as clean, but much safer.

I'm partial to DiMethyl Ether (DME). Chemically similar to propane/LPG, and equipment for storing/transporting LPG works fine for storing/transporting DME. Propane heaters, stoves, etc. run on DME without further modification. Cars which are converted to run on LPG run, with no further modification, on DME. It works well in diesel engines, too (better than propane/LPG; as with a spark-ignition engine, some conversion is necessary). And it's a good turbine fuel. Yes, you need propane-like tanks (DME needs about 5 bar pressure to liquify) but it burns really clean. Indeed, since it has no carbon chains (formula: CH3-O-CH3), diesel engines can burn this and have ZERO particulate emissions. Russia and Japan have been making it from Natural Gas for a couple decades, because both countries have significant "stranded" natural gas supplies and DME is easier to ship and store.

Comment: Re:So they've invented the plant? (Score 5, Interesting) 481

Not really. Plant metabolism is usually < 10% efficient at turning sunlight, CO2 and water into useful biomass. And the process for turning useful biomass into hydrocarbon fuels is < 100% efficient, so solar -> fuel is very low.

In their case, they're using intermittent power, from wind and solar, to do a modified Sabatier reaction and make methanol, which then goes into an integrated Fischer-Tropsch process to make longer-chain hydrocarbons.

The resulting solar -> fuel conversion efficiency is HIGHER than going through biomass production.

Comment: This is a problem with OO in general (Score 1) 411

by DaChesserCat (#49055805) Attached to: Your Java Code Is Mostly Fluff, New Research Finds
I write an application, be it in Java, C++, whatever. Insert Object-Oriented language of choice here.

I need to do I/O. So I use an existing class. Which is, more often than not, bundled into a large library of classes. And the classes in this library depend on classes in that other library. So I need my new class, and the classes it uses and the classes they use, all the way down.

If I'm writing an app which uses data persisted to/queried from a SQL database, there are libraries (for Java, usually .JAR files, frequently megabytes in size and that's WITH compression) which I can use. I may use a few classes from that library. And those classes may use a few more. But I can't extract the classes I need and create a new library. I have to bundle their ENTIRE library, with all of the associated classes, regardless of how many/few I actively use. And this library has dependencies in those libraries. And that library has dependencies in those libraries.

By the time you write something for a website which will use Hibernate to handle the ORM duties, Spring framework to handle the web duties, etc. you end up with an application that's > 10 MB in size. The code which I, actively, wrote is
Furthermore, if I choose to extend that other class, I may create a method which overrides a method in that class, and my method may not use theirs at all. As such, I still have to include their class, and its associated library, IN ITS ENTIRETY, but parts of it not only aren't being used but aren't even REACHABLE. Because calling, where foo is an object of my class, can't even reach the extended class's .bar() method.

Object Oriented programs are built in layers, by accretion. As the number of layers increases, the amount of unused and unreachable code grows. Until, voila! we're down to 5% of the code in the app actually getting used, even if you exercise ALL of the functionality in the app.

Java is merely one of the worse offenders in this. When you have a stacktrace with 30 layers in it, that's a LOT of code. A significant fraction of which is NOT getting used by your app.

Comment: Re:Levels (Score 2) 214

by DaChesserCat (#48924659) Attached to: Ask Slashdot: What Makes a Great Software Developer?
Agreed. The most enlightening experience I ever had as a developer was to go back and maintain something I hadn't seen or touched, and no one else had touched, in three years.

Who wrote this crap? Oh, I did. Was I ever that lame? Seriously? WTF does this code do? A one-line comment would've helped.

Eagleson's Law definitely applies.

Especially as you age. I'm pushing 50. I've become the king of docs, both in the code and on the wiki. Because I've learned that there's no guarantee that I'll remember how to do that obscure thing six months from now when I need it again. And if someone else benefits from my docs, that's just icing on the cake.

Comment: Re:Wireless bandwidth is limited (Score 1) 38

by DaChesserCat (#48172485) Attached to: Internet Companies Want Wireless Net Neutrality Too

Wireless bandwidth is limited by the allocated spectrum. With landlines, you can always drag more fiber or copper, hook it up, and expand your bandwidth. You can't do that with wireless.

No, but you can:

  • install more towers
  • reduce the power output/coverage on the existing towers, creating smaller cells
  • re-use the bandwidth you've already been allocated, in smaller cells

This is how wireless carriers increase bandwidth. There's considerably more bandwidth available, per square mile, in a city than in a rural area. Not because they have more spectrum in the city. But because each tower services a smaller cell.

It's slightly more complicated than that; adjacent towers need to use non-overlapping spectrum, permits, backhaul connectivity, power. Yeah, it's expensive. Of course, it's expensive to drag more fiber or copper, too.

User Journal

Journal: Hydraulic Hybrid Notes

Journal by DaChesserCat

I've commented multiple times about hydraulic hybrids. I like them, relative to electric hybrids, because they have a very high power density. I like the acceleration that power brings. And 1,000 charge/discharge cycles is hard on batteries but pretty much a normal day for hydraulics.

Comment: I gotta call BS on this (Score 1) 546

by DaChesserCat (#47820505) Attached to: Does Learning To Code Outweigh a Degree In Computer Science?
In 1990, with a couple semesters of college behind me (including formal courses in C and Fortran) and a LOT of self-directed learning behind me in high school (including AppleSoft Basic, 6502 Assembly and Machine Language, 8080 Assembly Language and Pascal), I took an entry-level development job. I was working with C (on which I had formal training), an assembly language (different from the others I'd already learned) and a language called Occam II.

It did not go well.

While I had a good understanding of the basics, and I could do bitwise logic and such (courtesy of my assembly language and machine language experience), I found myself struggling. Hard. It took me a while to get stuff working, because I had to "feel my way through" on most everything and I was severely handicapped in how complex the code could get before I was lost.

I eventually went back to college and got the Computer Science degree.

Being able to program is a useful skill. But if you don't know enough theory to handle relational databases, trees and other fairly complex data structures, you're hampered right out of the gate. Yeah, that's theory. Being able to code a balanced tree is useful; understanding when you do and DON'T need that data structure is more so.

Additionally, I don't get where they're saying these degrees are all theory. I had to write a pile of assignments in C++ during my college studies, as well as learning enough Scheme, Java and MIPS and x86 Assembly Languages to write assignments in those languages. That's practical, hands-on development, gaining experience with the language and its associated APIs. Additionally, if you do an internship somewhere while you're in college (I didn't, but I've managed/mentored an intern or two, now that I'm an experienced dev), you have hands-on experience with more than just a programming language.

Every company does things a little differently. Different standards, different conventions, different infrastructure. Ergo, it is PHYSICALLY IMPOSSIBLE for someone to walk in, with no existing experience with that company, and go right to work, being productive for the employer on day one. Yes, Human Resources and management keep indulging in that pipe dream. If only the schools would teach THIS, not that. If only they'd spend less time on math and more time on the finer points of this framework. Failing to realize that they'd be chopping out useful theory which could (and quite frequently, will) be useful down the line.

Besides, if you were trained in EXACTLY what this company needed, you would never be able to jump ship to another employer. Too many employers keep finding excuses not to provide raises that keep up with the cost of living. The only way to keep up, these days, is to jump ship every few years. And your next employer will need stuff the last employer didn't need. So, getting trapped in a pipeline which is heavily customized for one employer is bad for your long-term prospects.

Comment: Re:Lithium shortage (Score 1) 143

by DaChesserCat (#47723681) Attached to: How Argonne National Lab Will Make Electric Cars Cheaper
For your first question, unlikely. People like to compare supply/demand for lithium to petroleum. Unlike petroleum, you aren't "consuming" lithium. You're making it into stuff. Stuff which can be recycled. So, if you're seeing articles about "Peak Lithium" (a reference to "Peak Oil"), you can safely bet they're full of it.

Your second question suggests a basic understanding of supply-demand. Good.

As the demand for lithium increases, the price WILL go up in the short-term, which will stimulate investments in creating supply. We're already seeing the ramp-up in supply coincident with the ramp-up in demand. A few years ago, Electrovaya was advertising Lithium Ion batteries, large-format, for $300 / kWh in volume. That's what Elon Musk claims to be paying for his batteries, today. But the demand is at least an order of magnitude higher. We've already passed the "hump." And Elon Musk's investment, with Panasonic, in the "Gigafactory" is intended to push the supply higher, pushing the price lower, on the cheaper side of that hump.

A sudden, HUGE spike in demand could create another hump, but most manufacturers are sensitive enough on price that they will probably avoid it.

The fancy is indeed no other than a mode of memory emancipated from the order of space and time. -- Samuel Taylor Coleridge