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Comment by tonystubblebine | Hacker News Reader

Could somebody help with some background on the science?

What strikes me as odd is that you put fuel in the fuel cell. One of the examples they give is using these to charge your hyrbid car. So, by the transitive property, aren't you putting fuel into your car?

I guess I'm trained to think of alternative energy sources like sun and wind, so I'm thrown off here. What's the innovation?

I can see that you're generating electricity locally, which I guess means we could get energy to places without running power lines. But reading the article, that doesn't seem like the point of these.

The article does claim that the energy is more efficient than what you get on the grid. But if that's the case, why don't we just put a ton of these onto the grid and push down the cost of electricity for everyone?

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You put in a hydrogen source... in this case, likely natural gas. It combines with oxygen from the air in a process that yields electricity, water, and a small amount of CO2.

The key benefit is that the fuel isn't burned. It's converted chemically, so it is a very efficient process.

They have a good flash video explaining it here: http://bloomenergy.com/products/solid-oxide-fuel-cell-animat...

Any idea about the relative efficiencies between this chemical reaction versus a thermodynamic process (say, Sterling Engine)?

I don't think there's a clear winner yet. The devil is in the details, as they say. A good Stirling engine will beat a lousy fuel cell, and a good fuel cell will beat a lousy Stirling engine. Both are in the range of 20-50% when implemented well, but they both have lots of problems.

Fuel cells, for example, typically have a membrane at their core; that membrane tends to get clogged with crud. Stirling engines, on the other hand, are generally heavy (and thus expensive) and need to use exotic materials to handle high temperatures, which they need to operate efficiently.

Burning, oxidization of hydrocarbons, is very much a chemical process. It generates heat, if they have somehow found a way of making it generate electricity directly, that would be really interesting.

Isn't that exactly what a fuel cell is about?

I think the box has to get heated to (or is heated to as part of the process) about 1000C.

Here is another article about them: http://www.fastcompany.com/1557348/bloombox-bloom-box-fuel-c...

Combustion is a chemical process, but it is hardly a controllable one. In this case, a fuel cell doesn't combust the fuel, but instead converts it into water and CO2 while stripping the electrons directly from the hydrogen (I think).

> It combines with oxygen from the air [...] > the fuel isn't burned. It's converted chemically

My last chemistry class was a long time ago, so this might be a dumb question. What's the difference between combining with oxygen and burning?

In a chemical sense, no difference, but fire is complicated. Check out Wikipedia articles on Redox, Radicals, Combustion, etc.

Fuel cells are cool because they grab electricity straight from the freed electrons as the fuel is oxidized. More efficient than using the heat to make steam to power a turbine to spin electromagnets, your typical power plant.

I think they just announced a highly-efficient natural gas electric generator. The question is just how efficient, if it's as efficient as the large centralized power plants we now build then we don't have to waste money on building and maintaining power transmission lines.

If I remember my thermodynamics correctly, the efficiency of a heat engine is constrained by the internal temperature of the engine. The higher the internal temperature, the more efficient the engine can be. This is the basic reason why we build as large power plants as transmission loss allows. With a smaller plant, the engine temperature is much lower for practical reasons, hence the loss in efficiency. (Many other economies of scale reasons.)

So if this device can really beat the efficiency of our current centralized natural gas burning plants, then this is revolutionary. If not, too bad for Colin Powell.

Fuel cells are not heat engines.

That would be exactly why this new technology might be more efficient than centralized power plants.

They claim that it's twice as efficient as grid. But this might take into account losses during energy transfer from power plant to receiver.

From their data sheet it's about 50% efficient, on par with modern large scale natural gas powerplants.

If you also use the heat it generates to heat your home the Bloombox can be up to 85% efficient.

> then we don't have to waste money on building and maintaining power transmission lines.

Instead we'd just need to maintain a much larger natural gas infrastructure.

For your car example:

You would have to put some fuel like natural gas into your car. This would be converted to electricity.

The innovation is it would not be converted from fuel to mechanical energy (motor spinning) to electricity, but rather by a more efficient fuel cell. That is a big game changer.

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