Super-Soaker inventor may have solar-powered fuel cell breakthrough • Hacker News Board

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#61

Post by ramchip » Wed, Oct 13, 2010, 4:23 AM UTC

anthonyb wrote: post #42

kjuhygtfrde wrote: post #36

Earlier quoted context omitted.

On HN we obey the 2nd law of thermodynamics

That entropy always increases? How exactly does that apply in the case of focusing photons?

Disclaimer: not a physicist.

My intuitive understanding is that, as you heat the absorber, it becomes hotter and hotter, until it reaches the same temperature as the sun's surface. At this point, the absorber (also a blackbody) radiates just as much energy as it receives from the sun; thus there is no more heat exchange. Otherwise, you would be taking two objects at the same temperature and making one hotter and the other one colder with no work from outside the system, violating thermodynamics.

There is a more formal study in solar energy books like (http://books.google.com/books?id=81WI2LwrpkcC&lpg=PA25&#...) or (http://www.physics.drexel.edu/~jenks/Solar%20Energy.pdf) (PDF, page 21 onwards is quite relevant).

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#62

Post by Cushman » Wed, Oct 13, 2010, 4:27 AM UTC

brc wrote: post #49

brc wrote: post #8

The Lesson here is : if you do make a pile of cash, lock some of it away so that you and your family have an (almost) assured retirement plan.

I don't understand the downvoting, so I'll make my position clear. If you read the article, the guy is now in financial trouble because the super soaker profits have largely dried up, and he has had to put other plans on hold. What I'm saying is, if you find yourself in the situation where you have a big win, you need to lock away some of that to keep you in retirement. Then, you can go onto your next venture knowing…

The Super Soaker profits are now "only" enough to pay for a third of his dozen-employee business. Presumably if he wasn't so committed to his research, he could shut down and live comfortably off of that money.

Putting something away for the rainy day might be good advice, but it isn't really relevant here.

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#63

Post by cvg » Wed, Oct 13, 2010, 4:32 AM UTC

dusklight wrote: post #20

Vekz wrote: post #15

Could someone explain the differences in acquiring funding as an inventor vs an entrepreneur? Reason I ask is that I was recently laid off by a failed startup that had secured and wasted an investment in the amount of 2 million. After that experience I went on to do some contract work with another early stage startup. They had no solid idea or vision for a product and had funding in the amount of 1.5 million. It is c…

It is not clear that he has been looking for investors .. from the article it seems he has been looking for government grants, which would have given him money without asking for equity in return. Johnson may have initially wanted to fund his invention purely from his own money, keeping all the equity, but as the money started running out he has been looking for alternatives.

He has been funding the company with his money from Super Soakers, but because of knock-offs is now only able to cover one third of expenses.

Looks like he's trying to give up as little ownership as possible: govt grants, reinvest revenue, slow to get vc funding.

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#64

Post by anthonyb » Wed, Oct 13, 2010, 5:05 AM UTC

ramchip wrote: post #61

anthonyb wrote: post #42

Earlier quoted context omitted.

That entropy always increases? How exactly does that apply in the case of focusing photons?

Disclaimer: not a physicist. My intuitive understanding is that, as you heat the absorber, it becomes hotter and hotter, until it reaches the same temperature as the sun's surface. At this point, the absorber (also a blackbody) radiates just as much energy as it receives from the sun; thus there is no more heat exchange. Otherwise, you would be taking two objects at the same temperature and making one hotter and the…

Your intuition seems wrong to me. The two major problems are that thermodynamics refers to energy, not temperature. Thus, as long as total energy is conserved, there's no problem. The second issue is that solar heating is due to radiation, not conduction/convection, so there's no heat exchange as such.

Think of it in terms of photons - if you're collecting and concentrating photons, the upper limit is the total number of photons which the sun produces. I'm pretty sure that if you focused all of those into a square meter of the earth's surface, then it'd reach more than 5760K.

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#65

Post by ck2 » Wed, Oct 13, 2010, 5:39 AM UTC

hop wrote: post #25

He will change the world if he can get 50-60% efficiency. Photovoltaic cells would be out and parabolic mirrors aimed at a heating elements would take their place - even better, tubes running under asphalt streets all circulating water through JTEC heat exchangers. A huge unmet need is extraction of heat energy at lower temperature differentials - it could put to use tons of waste energy at industrial plants, your ca…

But what if it's double the efficiency at twice the cost to produce?

It does sound rather more complex than a solar cell.

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#66

Post by gbhn » Wed, Oct 13, 2010, 5:45 AM UTC

anthonyb wrote: post #64

ramchip wrote: post #61

Earlier quoted context omitted.

Disclaimer: not a physicist. My intuitive understanding is that, as you heat the absorber, it becomes hotter and hotter, until it reaches the same temperature as the sun's surface. At this point, the absorber (also a blackbody) radiates just as much energy as it receives from the sun; thus there is no more heat exchange. Otherwise, you would be taking two objects at the same temperature and making one hotter and the…

Your intuition seems wrong to me. The two major problems are that thermodynamics refers to energy, not temperature. Thus, as long as total energy is conserved, there's no problem. The second issue is that solar heating is due to radiation, not conduction/convection, so there's no heat exchange as such. Think of it in terms of photons - if you're collecting and concentrating photons, the upper limit is the total numbe…

You can't do that (at least not with passive components). There's a famous optics result called the 'brightness theorem' that explains why not.

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#67

Post by ramchip » Wed, Oct 13, 2010, 5:49 AM UTC

anthonyb wrote: post #64

ramchip wrote: post #61

Earlier quoted context omitted.

Disclaimer: not a physicist. My intuitive understanding is that, as you heat the absorber, it becomes hotter and hotter, until it reaches the same temperature as the sun's surface. At this point, the absorber (also a blackbody) radiates just as much energy as it receives from the sun; thus there is no more heat exchange. Otherwise, you would be taking two objects at the same temperature and making one hotter and the…

Your intuition seems wrong to me. The two major problems are that thermodynamics refers to energy, not temperature. Thus, as long as total energy is conserved, there's no problem. The second issue is that solar heating is due to radiation, not conduction/convection, so there's no heat exchange as such. Think of it in terms of photons - if you're collecting and concentrating photons, the upper limit is the total numbe…

> Thus, as long as total energy is conserved, there's no problem.

Where did the other laws go?

> The second issue is that solar heating is due to radiation, not conduction/convection, so there's no heat exchange as such.

I don't understand how there could be "solar heating" but no "heat exchange".

Unless I misunderstood the papers I cited, the efficiency equations show that there is a limit (efficiency drops to 0% with Ts=Ta), but I'll still try to address the "intuition" part of your post.

Let's say we are in a black room with no windows, everything being at room temperature. I use lenses to concentrate the infrared light from the walls onto a black cube. Would the cube heat up from the concentration of photons?

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#68

Post by anthonyb » Wed, Oct 13, 2010, 5:59 AM UTC

gbhn wrote: post #66

anthonyb wrote: post #64

Earlier quoted context omitted.

Your intuition seems wrong to me. The two major problems are that thermodynamics refers to energy, not temperature. Thus, as long as total energy is conserved, there's no problem. The second issue is that solar heating is due to radiation, not conduction/convection, so there's no heat exchange as such. Think of it in terms of photons - if you're collecting and concentrating photons, the upper limit is the total numbe…

You can't do that (at least not with passive components). There's a famous optics result called the 'brightness theorem' that explains why not.

I think you mean "Conservation of radiance". It corresponds pretty much directly with "Power per unit area". Obviously, mirrors and lenses can reduce the unit area, while keeping power constant (at best).

http://en.wikipedia.org/wiki/Radiance#Intensity

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#69

Post by guynamedloren » Wed, Oct 13, 2010, 5:59 AM UTC

brc wrote: post #49

brc wrote: post #8

The Lesson here is : if you do make a pile of cash, lock some of it away so that you and your family have an (almost) assured retirement plan.

I don't understand the downvoting, so I'll make my position clear. If you read the article, the guy is now in financial trouble because the super soaker profits have largely dried up, and he has had to put other plans on hold. What I'm saying is, if you find yourself in the situation where you have a big win, you need to lock away some of that to keep you in retirement. Then, you can go onto your next venture knowing…

There is nothing in the article that states he has not put away enough money for retirement, nor that he could not retire right this moment if he wanted to. For all you know, he could have $100MM in bank, ensuring that his family is well-off for generations to come. The article doesn't delve into his personal finances at all - it merely states that the Super Soaker profits are not able to fund his research as much as they once did.

Re: Super-Soaker inventor may have solar-powered fuel cell breakthrough

#70

Post by anthonyb » Wed, Oct 13, 2010, 6:11 AM UTC

ramchip wrote: post #67

anthonyb wrote: post #64

Earlier quoted context omitted.

Your intuition seems wrong to me. The two major problems are that thermodynamics refers to energy, not temperature. Thus, as long as total energy is conserved, there's no problem. The second issue is that solar heating is due to radiation, not conduction/convection, so there's no heat exchange as such. Think of it in terms of photons - if you're collecting and concentrating photons, the upper limit is the total numbe…

> Thus, as long as total energy is conserved, there's no problem. Where did the other laws go? > The second issue is that solar heating is due to radiation, not conduction/convection, so there's no heat exchange as such. I don't understand how there could be "solar heating" but no "heat exchange". Unless I misunderstood the papers I cited, the efficiency equations show that there is a limit (efficiency drops to 0% wi…

> I don't understand how there could be "solar heating" but no "heat exchange".

Hmm, I thought that "heat exchange" referred to direct transfer of heat energy, perhaps I'm misremembering. http://en.wikipedia.org/wiki/Heat_transfer#Radiation doesn't seem to differentiate, but bear in mind that there's no way to focus molecular vibration with a mirror.

And if more photons hit the cube with your lens than without it, then yes, the cube will heat up.