Fuel Cells

Since there has been a lot of talk about wind turbines at the CNE....I thought i'd stick in a thread about fuel cells. Hydrogenics will be showcasing their 50 kW fuel cell system at the Ex on Aug 27 ( http://www.hydrogenics.com/ir/NewsReleaseDetail-1.asp?RELEASEID=115925 ).

Fuel cells have been an attractive alternative due to its high efficiencies and low emissions. There are many different types of fuel cells but PEM (polymer electrolyte membrane) fuel cells appear to be the front runner for vehicular, back up and micro applications.

How Do Fuel Cells Work??

A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into water, producing electricity and heat in the process. It is very much like a battery that can be recharged while you are drawing power from it. Instead of recharging using electricity, however, a fuel cell uses hydrogen and oxygen.



At the Anode, hydrogen dissociates into protons and electrons by the following chemical reaction:

2H2 => 4H+ + 4e-

The protons, solvated in water, travels from the anode to the cathode through the membrane while the electrons travel through an external circuit, creating electricity, to the cathode.

At the cathode the returning protons and electrons combine with oxygen to form water and heat.

O2 + 4H+ + 4e- => 2H2O


Barriers to Commercialization

Cost: Currently fuel cells are not cost effective when compared to conventional forms of power generation. However, millions of dollars are invested into r&d to drive down the cost of materials.

Hydrogen Production: Although hydrogen is the most abundant element on earth, it is often combined with other elements and must be separated. (eg H20, natural gas, methanol, etc). The fuel processing system accounts for the majority of the total cost of a fuel cell system. Use of direct fuels, eg direct methanol fuel cells is a potential solution to this problem.

Infrastructure: Currently there isn't a hydrogen refueling infrastructure. However in Canada, a "Hydrogen Highway" is in the works in BC. Fuel stations are planned for roads stretching from the US/Canadian border to whistler. This is also in the works for eastern Canada from Windsor to Montreal (http://www.thestar.com/NASApp/cs/Co...geid=971358637177&c=Article&cid=1061244610519)

 

Ballard Secures Contract for Three Fuel Cell Bus Engines for Australia
Vancouver, Canada - Ballard Power Systems (TSX: BLD; NASDAQ: BLDP) will provide three of its latest generation heavy-duty fuel cell engines to EvoBus for integration into Mercedes-Benz Citaro buses for the public transport system in Perth, Western Australia.


^^^any feedback on how the fuel cell buses are performing in the field?

 

Fuel cells in automotives are 10 yrs away at best.....you will probably see the first fuel cells in small portable applications (laptops, pda's etc) first.

 

but what about the current bus fleets in van, chicago, aus, london? any reports about how the technology is performing? maintenance issues etc?

if PEM and other fuel cell variants grow into a major energy source, how will this affect the h2 and o2 equilibria in the earth's atmosphere?

 

The buses in the field are not performing spectacularly. They only spend 1/3 of the time on the road and the rest of the time they are in for repair. (Which is to be expected to some extent as they are an experimental machine.)

Fuel cell cars are not 10 years off however. The high scale commercialization of them will be at least 10 years (more likely 15), but within 5 years it will be an option to buy. (Most likely the first generation wont fill up with pure H2, they will run on methanol either as a direct fuel or through an onboard reformer).

a.ron

 

What is the power to performance ratios compared to excisting technologies is what I wonder?

 

The use of direct fuels (methanol) is not practical for automotive applications. It has no where near the performance H2 PEM fuel cells have. The major problems are slow anode kinetics and fuel crossover. The use of direct fuels are practical for portable power.

If methanol is used for H2 PEM fuel cells it would require additional fuel processing steps either on board the vehicle or at the fueling station.


Good websites with good info are:

www.h2fc.com
www.fuelcellstoday.com

 

thanks, fuelcellstoday.com was a pretty good read. it's good that florida's pushing the necessary infrastructure, but i'm thinking jeb bush's $15mil will fund 5 refueling stations at most? The Governator's suggestion of $100mil sounds more on par with making a decent start. It is mostly politicking at this point, but good to see the ball is rolling.

The student contest for a refueling station conceptual design looks pretty neat. Prize is a trip to this year's conference in LA!

 

wow, haven't heard that figure before....
that's like only being able to drive your car on mon and tues each week, with a booze run on weds!

 

Actually Methanol fuel cells do have excellent possibility for automotive use. The slower anode kinetics and cross over are very controllable by running at higher anode voltages, in the upper range of polarization curves. Although the ideal voltage output is lower than H2, but can be coutnered by larger stacks if necessary. And the performances are not that far off. In fact the newest concept car from Daimler Chrysler runs on direct methanol.

The major advantage of direct methanol fuel cells is a methanol infrastructure. The cost of transfering to a methanol infrastructure is about a tenth of that to a hydrogen infrastructre which makes it an excellent stepping stone while finding a low cost, low polluting means of hydrogen production.


(I did do my Master's on direct methanol fuel cells so I may be a little bias)


a.ron

 

How would you control the anode voltages?

 

Well essentially there are two ways to control a fuel cell. You either demand a specific current density and the fuel cell outputs a voltage, or you demand a voltage and you get an outputted current density. Either way, essentially to get higher voltages you want to run at higher current densities. This can be done buy controlling the resistance or capacitance in the device you are running.

The other method is by controlling the concentration or flow rates of your fuel and oxidants.

a.ron

 

I always thought higher current densities result in lower cell voltages due to ohmic and concentration overpotentials.

I agree that controlling the resistance and concentration does increase voltage performance but with respect to DMFC, if you increase fuel concentration and run at high current densities, cross-over increases resulting in decreased cell potential.

 

And how long did it take you to do said Masters?

Sorry Aron... could resist...

And before you say it... I am an ass...

 

Sorry I should have specified. I was talking anode current density and anode current. You do recieve lower cell current at higher voltages, but you can compensate by larger stacks.

As for crossover, it is essentially based on two factors. The concetration of protons crossing the membrane from anode to cathode and the amount of methanol present at the anode membrane interface. At higher current densities, more methanol must be reduced to produce the necessary electron/proton flow, there is therefore less methanol present at the interface. So at a certain threshold current the crossover will actually begin to reduce due to lower methanol present.

There has also been quite a bit of research lately into new membrane material which can help reduce crossover at any voltage)

(Wow did I ever just nerd out there )

a.ron

 

This is how you act all the time...



Its just too easy...

 

Search for a thread about the end of the age of oil, you'll begin to understand that hydrogen fuel cells need a fossil fuel source to be in any way functional, and when oil sources begin to dwindle, they will be essentially useless.

 

I've just finished a book with some chapters written by Jeremy Rifkin ('the hydrogen economy') and Ballard.

It's such a chicken and egg problem; you can't fund infrastructure without consumers, consumers wont buy in without infrastructure.
Both of them indicated they thought industrial applications would be first. Forklifts, factory/warehouse applications, etc.

Once it proves economical there, it can expand and expand. It's not an application that will hit consumers for decades and decades to come. Most of them didn't predict any consumer applications until 2050 at least.

"The stone age didn't end because they ran out of stones"