A new type of natural-gas electric power plant proposed by MIT researchers could provide electricity with zero carbon dioxide emissions to the atmosphere, at costs comparable to or less than conventional natural-gas plants, and even to coal-burning plants. But that can only come about if and when a price is set on the emission of carbon dioxide and other greenhouse gases — a step the U.S. Congress and other governments are considering as a way to halt climate change.
Postdoctoral associate Thomas Adams and Paul I. Barton, the Lammot du Pont Professor of Chemical Engineering, propose a system that uses solid-oxide fuel cells, which produce power from fuel without burning it. The system would not require any new technology, but would rather combine existing components, or ones that are already well under development, in a novel configuration (for which they have applied for a patent). The system would also have the advantage of running on natural gas, a relatively plentiful fuel source — proven global reserves of natural gas are expected to last about 60 years at current consumption rates — that is considered more environmentally friendly than coal or oil. (Present natural-gas power plants produce an average of 1,135 pounds of carbon dioxide for every megawatt-hour of electricity produced — half to one-third the emissions from coal plants, depending on the type of coal.)
Absent any price for carbon emissions, Adams says, when it comes to generating electricity “the cheapest fuel will always be pulverized coal.” But as soon as there is some form of carbon pricing — which attempts to take into account the true price exacted on the environment by greenhouse gas emissions — “ours is the lowest price option,” he says, as long as the pricing is more than about $15 per metric ton of emitted carbon dioxide. Such a pricing mechanism would be put in place, for example, by the Waxman-Markey “American Clean Energy and Security Act” that was passed by the U.S. House of Representatives in July, through its “cap and trade” provisions. (A corresponding bill has not yet reached the floor of the U.S. Senate.) If the program becomes law, the actual price per ton of carbon would vary, being determined through the free market.
Reliable, affordable fuel cells have come not one but three steps closer to reality this week, with announcements from two research institutions regarding advances in the field.
If the reported developments make their way into production, we could be seeing fuel cells that use more abundant, less expensive fuels and building materials, that are more consistent in their electricity production, and that have a lower operating temperature.
Along with his colleagues from Harvard University’s School of Engineering and Applied Sciences, Shriram Ramanathan has created all-ceramic thin-film solid-oxide fuel cells (SOFCs) that don’t contain any platinum. Traditionally, SOFCs require platinum-coated electrodes, which can be both expensive and unreliable – “If you use porous metal electrodes, they tend to be inherently unstable over long periods of time,” he explained. “They start to agglomerate and create open circuits in the fuel cells.”
The Harvard group has also created a micro-SOFC that draws its power from methane, and that has an operating temperature of less than 500 C (932 F). Traditionally, hydrogen has been the fuel source of choice for SOFCs, but methane is more abundant, cheaper, and requires less processing. Additionally, conventional SOFCs operate at a temperature of around 800 C (1,472 F). This limits their portability, requires them to be constructed from very heat-tolerant materials, and lengthens their start-up time.
“Low temperature is a holy grail in this field,” said Ramanathan. “If you can realize high-performance solid-oxide fuel cells that operate in the 300 C (572 F) range, you can use them in transportation vehicles and portable electronics, and with different types of fuels.”
Biofuels are seen as a more environmentally friendly fuel source than petroleum-based fuels, but transporting the bulky biomass used to produce them is expensive because of their volume. It’s much more economical to transport the liquid fuel after it has been processed but this isn’t possible if the processing facilities are located far from the source of the biomass. A new method to process agricultural waste and other biomass could enable the creation of mobile processing plants that would rove the Midwest to produce fuels where the biomass is sourced.
“Material like corn stover and wood chips has low energy density,” says Rakesh Agrawal, the Winthrop E. Stone Distinguished Professor of Chemical Engineering at Purdue University. “It makes more sense to process biomass into liquid fuel with a mobile platform and then take this fuel to a central refinery for further processing before using it in internal combustion engines.”
The new method developed by chemical engineers at Purdue is called fast-hydropyrolysis-hydrodeoxygenation, which they have shortened to H2Bioil – pronounced H Two Bio Oil. It works by adding hydrogen into the biomass-processing reactor. The hydrogen for the mobile plants would be derived from natural gas or the biomass itself. However, its creators envision the future use of solar power to produce the hydrogen by splitting water, making the new technology entirely renewable.
MIT’s Angela Belcher, has engineered a virus so that it captures light energy and uses it to catalyze the splitting of water, a first step in a possible new way to generate hydrogen for fuel cells.
One main goal in the renewable energy field is to find an efficient, inexpensive way to split water into hydrogen and oxygen. The hydrogen could then be used as a fuel source for vehicles or fuel cells. Typically, an electric current breaks the water down. Now, there’s a new water-splitter: a virus. MIT’s Angela Belcher took her cue from plants, where special pigments capture solar energy in photosynthesis, involving the splitting of water.
Belcher and her team took a harmless virus called M13. They engineered it so that one end carries a catalyst—iridium oxide. Bound at the other end are light-sensitive pigments, zinc porphyrins. The porphyrins capture light energy, and transmit it along the virus, acting as a wire, to the other end, activating the catalyst. Which splits water into oxygen and the constituents of hydrogen, a proton and electron.
True to its word the formerly secretive Bloom Energy launched its Bloom “Box”
(hereafter known as the Bloom Energy Server), today with an event at eBay’s California HQ attended by Governor Schwarzenegger and Bloom Energy board member Colin Powell. Although the launch didn’t see any great revelations to add to the 60 Minutes coverage of the versatile fuel cell earlier in the week, the company did provide a few more concrete specifications for the Bloom “Box”, as well as some of the corporate household names that are already customers.
At the launch Bloom Energy founder, K.R. Sridhar, stressed some of the benefits of the technology.
It is cheap – in comparison to other types of fuel cells anyway. Instead of expensive precious metals the Bloom Box consists of thousands of flat, solid ceramic squares made from a common sand-like “powder.”
It offers fuel flexibility – Bloom Energy claims the Bloom Box can run on nearly any fuel source, be they renewable or fossil fuels. Natural gas and biogases look like being the most common fuel sources for the unit, but the unit is switchable, so you can buy the cheapest or cleanest fuel to suit your circumstances.
It’s reversible – instead of producing electricity from fuel (hydrogen) and air, it’s possible to reverse the process and produce hydrogen from electricity and air. In this way it could be used to create fuel for the next generation of hydrogen fuel cell powered vehicles – not a huge plus right now but could come in handy in the future.
It is reliable – unlike solar and wind power generation, which is at the mercy of the elements, the Bloom Box is always on.
Although the company has made a lot of noise about the technology being clean, there is a catch. It is substantially cleaner than the grid, but just how much cleaner will depend on which fuel source is being used.
Because the system uses an electro-chemical process and not combustion, owners can achieve a 40-100 percent reduction in their carbon footprint as compared with the U.S. grid depending on whether they are using a fossil or renewable fuel. On natural gas the specs state the Bloom Energy Server produces 773 lbs./MW-hr of CO2, while running on biogas the unit is carbon neutral.
The cheaper materials costs of the Bloom Box means that the company should be able to get the prices for the units down in the future. It is aiming to get them under US$3,000 to make them attainable for homeowners, but for the moment their $US700,000 to $800,000 each price tag means they’re likely just for corporations.
Even at that price the company says the units end up paying for themselves in three to five years.