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Comment: Re:even better (Score 5, Informative) 128

by MattskEE (#48639121) Attached to: Tesla About To Start Battery-Swap Pilot Program

Do you know how many solar panels it takes to charge an electric car? You're basically looking at a football field's worth, each.

Ah, to be young and full of made up numbers. Let's do the math.

The large Tesla battery is 85kWh. A solar cell typically has an efficiency of 10-20%, so with about 5kWh/m^2/day of typical solar radiation (check PVWatts for specifics in your town you can produce about 0.5-1kWh/m^2 per day.

If we assume 15% charging losses it will take 100kWh to charge a Tesla battery, which will require 100 to 200 square meters to produce in one day. A football field has about 5300 square meters, so we could expect one football field of tightly packed solar panels to charge around 26 to 53 Tesla's per day.

Comment: Re:wimpy talk (Score 5, Interesting) 187

by MattskEE (#48606605) Attached to: Graphene: Fast, Strong, Cheap, and Impossible To Use

Graphene in addition to the engineering challenges does have some very fundamental scientific challenges as well.

The most important challenge is its lack of a bandgap meaning that graphene transistors cannot be turned off. That drawback means that while it may have a ~500GHz cutoff frequency on par with silicon and below the InP records it will not modulate current in an energy-efficient way, and while it can create some forms of logic the lack of a bandgap limits its power amplifying frequency to a measly 50GHz, well below the competing technologies. Contrast that with Northrop Grumman's recent 1000GHz amplifier, which is admittedly not a great amplifier since it is run very near its cutoff frequency it has 1dB or less gain per stage, but it works which is still quite impressive.

So far the various methods that can give graphene a bandgap also take away the extremely fast electron transport properties that made graphene so interesting for electronics in the first place. Some of us working on competing technologies wonder why hundreds of millions of dollars have been spent on graphene transistor development without solving the fundamental bandgap problem - of course we just want that money directed to our own research, but some of us try to be realistic about the capabilities of what we are developing ;-)

I'm sure graphene will be useful for some things but so far there are still some fundamental problems that need to be solved before using it for high-speed electronics for wireless applications or digital logic. We'll see how it does.

Comment: Re:Usability Nightmare (Score 1) 63

by MattskEE (#48288897) Attached to: LG's 0.7mm Smartphone Bezel Is World's Narrowest

Cynical much? One phone does not need to be all things to all people in order to be successful. Not all of us need cases on our smartphones: in my 4.5 years of smartphone usage and two smartphones I have yet to damage my uncased phones in any way.

Since you need a case on your smartphone you should buy a different one, others of us enjoy the beautiful design of a tiny bezel. But I hope to keep my phone at least another 1-2 years so I'm not in the market currently.

Comment: Re:We use stuff like this (Score 1) 81

by MattskEE (#48287887) Attached to: Integrated Circuit Amplifier Breaches Terahertz Barrier

Why does the 3D printing matter? Some people do make ultra high frequency waveguide with 3D printing - in the case I'm familiar with they "printed" it on a stereolithgraphy machine out of a polymer, then gold plated all of the surfaces. It may have some applications for complex waveguide circuits which are not possible to make by other methods in a given size constraint. However, getting the plating thickness just right on such a small scale when you have to plate the inside of the long and super narrow waveguide tubes is difficult and conventional machining techniques are often faster and cheaper, and can have higher material quality than a printed or plated material.

The point of the Northrop Grumman work is that the circuit is integrated on a chip, so the waveguide interconnect will be relatively simple and simple objects can generally be made better, faster, and cheaper, by conventional techniques.

Comment: Re:For Starters (Score 1) 320

by MattskEE (#48247889) Attached to: What Will It Take To Make Automated Vehicles Legal In the US?

If that is the rationale, then the car needs to be 100% automated, under all circumstances, with all liability going to whoever made the damned thing.

I don't see why that would be necessary. Effectively you are saying that insurance over the lifetime of the vehicle should be factored into the purchase price instead of allowing people to buy insurance policies. That's not a bad idea but I don't think that it should be a requirement.

Instead this can be treated like any product: you buy an insurance policy to cover damages and go after the manufacturer in cases of negligent manufacturing or design flaws.

Comment: Re:Sounds wasteful and stupid ... (Score 1) 61

by MattskEE (#48247821) Attached to: Haier Plans To Embed Area Wireless Chargers In Home Appliances

They claim to use far-field power transmission (i.e. radiated power) rather than near field inductive coupling. The transformer analogy only works for near-field transmission but it tends to be difficult to get range. Far-field will be radiating power all over the place.

Comment: Re:Sounds wasteful and stupid ... (Score 1) 61

by MattskEE (#48247349) Attached to: Haier Plans To Embed Area Wireless Chargers In Home Appliances

If power is transmitted using near-field methods such as the direct inductive coupling used in RFID, most cell phone wireless chargers, and electric toothbrush chargers then the power transmission is coupled directly to the recipient device, and if the device is removed and the transmitter is still running then very little power is radiated away. This is potentially quite efficient. If you use far-field transmission then power is being radiated away whether a device is there to receive it or not. In order for it to be efficient you need high antenna gains to focus the power into a narrow beam the size of your receiver antenna aperture and beamforming to actively steer it. Otherwise the antenna is just spraying a broad beam of power in the general direction of the receiver like your sprinkler analogy.

They say it's using far-field transmission of power:

WattUp's RF transmission, which operates at 5.7MHz and 5.8MHz, is referred to in the industry as "far-field" wireless charging. Energous is not the first company to come up with the idea.

At such low frequencies it would be very hard for them to implement high gain antennas and beam forming. Also at such low frequencies I wonder how it can really be far field since the receiver will be well within a quarter wavelength of the transmitter.

More information is needed to fully answer the question, but this sounds like a convenience feature rather than an efficient one.

Comment: Re:The Nobel Prize Committee blew it (Score 4, Informative) 276

by MattskEE (#48105143) Attached to: No Nobel For Nick Holonyak Jr, Father of the LED

The blue LED may have been harder than the red LED for the reasons that you give, but Holonyak did make some key accomplishments including the demonstration of a ternary alloy semiconductor and tuning the bandgap and thus color by varying alloy composition which has paved the way for achieving all of the different colors for LEDs in use today and is also used for the InGaN emission layer in the blue LEDs.

An alloy semiconductor instead of having, for example, one group III and one group V element in perfect 50% ratio in a uniform crystal structure mixes it up and uses two or more group III elements and two or more group V elements. In the case of Holonyak he used two group V elements: Arsenic and Phosphorous. At the time at least some people did not think that an alloy semiconductor would even work, and it is a little weird because the crystal structure is now non-uniform where a given group V crystal site contains one element or the other at random. In fact this randomness does slow down the electrons. Holonyak also showed that the bandgap could be tuned by varying the relative concentrations of the group V elements. You can read more about him in a nice IEEE profile.

I don't know enough about the history to say who should have gotten the Nobel, but certainly no matter who they selected somebody would have been snubbed.

Comment: Re:It's a boring choice (Score 1) 243

by MattskEE (#48086001) Attached to: 2014 Nobel Prize In Physics Awarded To the Inventors of the Blue LED

There isn't a limit of one prize per invention or discovery. The Physics and Chemistry Nobel prizes are frequently awarded decades after the original work was done.

The Nobel prize announcement did state that the significant impact of this invention was a factor in the selection. In addition to the huge commercial and societal impact of the work these researchers' work had a major scientific impact on the entire field of growth and properties of nitride semiconductors. LEDs are certainly the biggest application of nitride semiconductors but their work has also paved the way for nitride transistors in wireless and power electronics applications.

Comment: Re:12kW/day? (Score 2) 268

by MattskEE (#47989443) Attached to: IBM Solar Concentrator Can Produce12kW/day, Clean Water, and AC

Yes, it's a very crude estimate, and more of a summertime number too here in the US.

In the US I would refer them to PV Watts which will take examine a database of historical solar data and tell you how much daily energy to expect through the year for different types of setups, even including solar panel fixed angle or angle tracking systems. But it will not take into account your point on the effect of diffuse light on concentrated systems.

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