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Comment: Obvious to Engineers (Score 5, Informative) 184

Any engineer who has studied thermodynamics knows that water has about four times the specific heat as air. The mass of the oceans is about 260 times that of the atmosphere. Combine these facts, and you find the oceans have about 1000 times the heat capacity of the atmosphere. Thus it should be obvious that in any scenario of temperature change, the oceans will play a big, if not dominant part.

In regards to Chipmunk100's summary, greenhouse gases affect the heat input to the planet. The oceans represent a vast amount of thermal storage capacity. One is the current rate of change, the other is the integrated total of the changes over a number of centuries. Different units with different dimensions. A change in greenhouse gases today will take a long time to show up as an overall change in ocean temperature.

Comment: Re:Solar Could be 50+% of production, but... (Score 1) 167

by DanielRavenNest (#48065521) Attached to: Solar Could Lead In Power Production By 2050

Areas of the country that are very cloudy tend to have more wind and hydro energy, cause clouds tend to be associated with storm fronts. You are correct that solar varies in usability by location, but typically other renewables compensate. Hydro in Seattle, solar in Phoenix. And grid operators know this. They aren't stupid.

Comment: Re:The problem isn't energy effiencey but cost. (Score 2) 110

by DanielRavenNest (#48052501) Attached to: MIT Study Outlines a 'Perfect' Solar Cell

Walmart already puts solar panels on many of their stores:

Besides generating electricity, the panels protect the underlying roof from sun exposure, thus extending their useful life. When they run out of rooftops, they can start on the parking lots. This not only generates more electricity, it provides covered parking. In sunny states this is very desirable. Once electric cars become more popular, charging stations powered by panels above the parking lot will be another desirable feature for customers - shop and recharge your battery at the same time.

Comment: Re:Carnot efficiency (Score 1) 110

by DanielRavenNest (#48052443) Attached to: MIT Study Outlines a 'Perfect' Solar Cell

> 1) Blackbody radiation is emitted from all sides of the emitter; it cannot be made directional.

Emitter is a cylinder heated from the center. Electricity making cells are a larger cylinder around it. Photons emitted from the inside of the hot cylinder will mostly hit another part of the cylinder.

>2)... This means the emitter has to be bitching hot.

Make the ratio of cylinder sizes large enough, and your electricity making cells won't melt. They will get pretty warm, and you can extract secondary heat by water cooling their back side. Make hot water or something.

Comment: Re:Uses blackbody emission (Score 1) 110

by DanielRavenNest (#48052397) Attached to: MIT Study Outlines a 'Perfect' Solar Cell

But then I have to ask why not just melt salts and store them so you get energy storage as well.

Because crushed stone is even cheaper than salts or oil for thermal storage. Not much is cheaper than that. You circulate air through a heat exchanger and the rock bed to store heat, and reverse the flow to extract heat. The heat exchanger in turn gets hot fluid from the focus of a solar concentrator. Melty stuff like oil or salts need liquid-tight tanks. A hot rock bed can be a concrete lined ditch filled with rock, but doesn't need to be perfectly air tight, just about as tight as most ventilation systems. A sheet metal lid covered with insulation should be good enough.

Comment: Re:perfect? (Score 1) 110

by DanielRavenNest (#48052327) Attached to: MIT Study Outlines a 'Perfect' Solar Cell

One producer expect $400/kW in a few years:

Panel prices are already well into very affordable ranges. As you say, the real work now is getting all the other parts of the cost down (wiring, mounting racks, inverters, labor, land, and paperwork - permits, planning, etc.)

Comment: Re:Least helpful summary ever? (Score 4, Informative) 110

by DanielRavenNest (#48052279) Attached to: MIT Study Outlines a 'Perfect' Solar Cell

Well, going to the abstract of the actual paper, What they have is silicon milled with dielectric cavities (waveguides) that are tuned to the frequency of your solar cell. Hot black bodies can emit any wavelength, but the tuned cavities can only efficiently emit one. Other wavelengths destructively interfere. In that respect they work just like antennas at radio wavelengths.

The tuned light is efficiently absorbed by the solar cell. Natural sunlight isn't because some of the photons are too high in energy, and the excess gets wasted as heat, and some are too low and don't kick out an electron at all. Thus you get around 25% efficiency in a good cell these days.

Comment: Re:Profitable, if self-contradictory (Score 1) 549

A billion years is of course an extremely long time in the context of human evolution, so who knows what we might be able to accomplish in that timespan.

The world's installed base of solar panels has grown at 55% per year recently. At that rate, we would have enough panels to absorb the entire output of the Sun in less than 80 years. I would revise your statement to read:

"A hundred years is of course an extremely long time in the context of human society, so who knows what we might be able to accomplish in that timespan."

Comment: Re:More Efficient (Score 4, Informative) 549

> I don't know what technology could get a ticket to Mars from the Earth down to say $100 USD,

I do, but then I wrote a textbook about space systems engineering [ ]. It's a combination of self-replicating automation, extracting local materials and energy everywhere, and a space elevator network.

* It would be very expensive to haul all the equipment you need to Mars in order to live there. Instead, what you want to send is a starter kit of basic machines, and use those to build other machines, until you grow big enough to make the final equipment (habitat domes, etc.). You prefer to make this starter kit as automated as possible, since you won't have the facilities to support people until later. You start on Earth, and build a starter kit that grows to a full factory. That factory builds a second starter kit that gets launched to orbit, where it grows to a full factory. In turn that one sends a starter kit to Phobos, and then finally the Phobos one sends one down to Mars.

* All of the factories run off of local solar energy and process local materials to make most of the new products. A few percent will need to be imported parts, because they are too hard to make, or use rare elements. At each location you build up greenhouses, habitat modules, and processing plants. One of the locations is a "Cycling Mars Transfer Orbit", which goes back and forth from Earth to Mars. So instead of sending 10,000 Mars Colonial Transports carrying 100 people each, you build up a mining colony/transit hub that makes multiple trips, carrying people each time.

* A rotating elevator (Skyhook or Rotovator) can provide about as much velocity change as a rocket stage. A series of them in Low Earth Orbit, High Earth Orbit, and Mars Orbit can provide the velocity changes to hook up with the mobile mining colony, and then put you down on Mars.

Such a system would be low cost to build and run, but you need enough traffic (like 10,000 passengers a year) to justify building it.

Comment: Re:Really? (Score 3, Interesting) 517

by DanielRavenNest (#48009441) Attached to: Utilities Should Worry; Rooftop Solar Could Soon Cut Their Profit

The largest solar-thermal plant yet built, Ivanpah, at 400 MW capacity, is on the same transmission lines as Hoover Dam. Both are near Las Vegas. It doesn't need thermal storage because the dam effectively does the job. When Ivanpah is running, Hoover can save the water for other times of day.

When you look at a grid as a whole, instead of individual plants, you find synergies like this you can apply. Detractors of renewable energy tend to ignore that most plants are grid-connected, and power demands vary by time of day and season. Thus Ivanpah is well matched to Las Vegas. Peak demand happens when it is sunny and everyone is running air conditioning. Sunny is exactly when that plant is pumping out electricity.

Solar, however, is a poor match for the Pacific Northwest, because it is cloudy much of the time. Instead, hydroelectric and nuclear are the main sources up there. Lots of rain and mountains make hydro easier to build. Detractors will point to Germany and say solar sucks. Well, Germany is far north, and not very sunny. Italy and Spain are better suited climatically. Just because it doesn't work that well in one country or region does not mean it cannot work in better locations. The opposite example is Chile, which is rapidly installing solar. The high Andean plateau is not only exceedingly dry, it is cold and high altitude, both of which improve performance of solar panels.

Comment: Re: Recycling coins (Score 1) 56

by DanielRavenNest (#47986511) Attached to: PayPal Integrates Bitcoin Processors BitPay, Coinbase and GoCoin

Coinbase has 1.7 million user wallets ( ). I buy my bitcoins from them because I can pay via ACH transfer from my bank account. It's very convenient. My understanding is BitPay recycles their coins through exchanges.

> Why not just pay with regular money?

Most merchants who take bitcoin are online (76,000 total merchants, 5000 physical locations). Even in the US not everyone has access to a bank card, and outside developed countries the majority don't. Bitcoin doesn't arbitrarily seize or close your account because they don't like your business. If you need to send money right away (bank wires) or internationally at any speed, the fees are really high. Some merchants offer a discount for bitcoin purchases, because they get to avoid bank fees for debit/credit purchases, chargebacks, and fraud. Even cash has significant overhead - you have to monitor employees and customers, count it, take it to the bank, etc.

If all you do is buy stuff with your debit card at local stores, there isn't much reason to use bitcoin, but not everyone is in the same situation.

Comment: Re:Is this anything other than a press release? (Score 2) 91

> as there is nothing there

There is as much land area as the Earth. It just needs proper development. Las Vegas is in a fucking desert, and people live there anyway. The real problem is people who look at an empty piece of land and see nothing, rather than seeing the potential for what it could become.

Comment: Re:I thought this was long ago debunked (Score 1) 275

by DanielRavenNest (#47969677) Attached to: Nvidia Sinks Moon Landing Hoax Using Virtual Light

There are many rational lines of evidence that the Lunar missions happened. My own personal ones include that I went to work at Boeing's space systems division in 1981, and the people who worked on the Saturn V and Lunar Rover *were still there*, as well as the project data. I've also visited the NASA repository where the two million microfiche cards with all the drawings are stored.

The problem is the conspiracy nuts are not rational. No amount of evidence will convince them, any more than you can convince a young Earth creationist that their holy book is bunk. Fortunately, science and technology doesn't depend on their belief. If a few well reasoned arguments don't convince someone, their mind is too closed to bother with. Just get on with your life. The conspiracy nut will still be able to get their satellite TV based on the same fucking technology that got us to the Moon :-) (big rockets).

Information is the inverse of entropy.