FuelCell Energy, Inc. (NasdaqNM: FCEL), and Enbridge Inc. (NYSE: ENB) have announced initiating production of the first multi-megawatt hybrid product, generating ultra-clean electricity while recovering energy normally lost during natural gas pipeline operations.
The new product, the Direct FuelCell-Energy Recovery Generation(TM) (DFC-ERG(TM)) system, combines a 1.2 megawatt (MW) Direct FuelCell(R) (DFC(R)) power plant with a 1 MW unfired gas expansion turbine. Operating at natural gas pipeline letdown stations, the system generates 2.2 megawatts (MW) of ultra-clean electricity.
To transport natural gas across the continent, natural gas pipelines operate at high pressures and considerable energy must be injected to achieve the pressures required. This high pressure must be reduced when the gas enters lower pressure systems that deliver gas to homes and businesses. Currently, there is no commercial use made of the energy that is lost at that stage. Additionally, when pressure is reduced, the gas cools. To ensure reliable pipeline operations, the cooling must be offset -- by burning some gas in boilers, reheating the supply to an acceptable temperature.
With the new DFC-ERG system, high-pressure gas passes through a turbine, capturing some of the energy that was otherwise lost, and turns it into usable electricity. The integrated fuel cell also electrochemically converts some of the gas into low-impact, environmentally friendly electricity. Finally, heat normally generated by the fuel cell warms the gas to its proper distribution temperature -- thus eliminating the boiler (and its emissions). The combined system can achieve electrical efficiencies over 60 percent, with low noise and virtually zero smog emissions.
FuelCell Energy’s products are called Direct FuelCells because unlike other fuel cell technologies, Direct FuelCells can use hydrocarbon fuels without the need to first create hydrogen in an external fuel processor.
What distinguishes this hybrid concept from many other proposed hybrid systems is the novel approach of integrating the turbine with an atmospheric pressure fuel cell and recovery of the waste heat in a Brayton cycle. The fuel cell does not need to operate at the turbine pressure, instead it operates at the preferred ambient pressure and is independent of gas turbine cycle pressure ratio. The system works efficiently with a wide range of turbine compression ratios (3 to 15). This means that in principle the concept can be applied from the multi-MW scale (with industrial size turbines operating at 9 to 16 pressure ratios), to smaller systems using microturbines at a lower pressure ratio. Key features of the system include:
• Unmanned Remote Operation—The design approach preserves the ambient pressure operation of fuel cell, avoiding the need for a high-pressure boiler. The power plants can be sited almost anywhere, including unattended remote locations, without the need for an operator and without complications from local safety codes for high-pressure boiler operation.
• Simplicity in Design—The system retains much of the simplicity of our direct fuel cell technology which eliminates fuel processing equipment including external reformer and shift reactors. This results in the most efficient and reliable fuel cell power plant configuration.
• Low Pressure Fuel—The required fuel supply pressure is at the natural gas line pressure which is typically available at about 15 psig on most commercial sites. A fuel compressor is not required.
• Load Following and Reliability—The turbine section can be used to load follow utilizing stored kinetic energy, while the fuel cell is efficiently operated at constant power. This is only possible because of the decoupled nature of the fuel cell and turbine sections of the plant. This feature, not realizable in other pressurized fuel cell systems, imparts attractive load following characteristics in grid-independent applications.
• Environmental Benefits—The Brayton cycle in the hybrid system is an unfired system, indirectly heated with fuel cell waste heat, normally at about 650°F. This results in low NOx generation and yields the highest efficiency, since all primary fuel consumption is done in the fuel cell - which is the more efficient portion of the system. The hybrid system has lower emissions per kWh than simple cycle power plants, due to the higher efficiency.
Enbridge's research has identified 40-60 MW of opportunities for the DFC-ERG system in just one of its operating areas. The North American market represents another 200-300 MW, consisting of the half dozen U.S. states currently seeking to add fuel cells' environmental attributes to their Renewable Portfolio Standards (RPS). These jurisdictions recognize that a portfolio of low-impact energy supplies, renewables and near-zero emission fossil fuel technologies can provide immediate and long-term benefits.
FuelCell Energy develops and markets ultra-clean power plants that generate electricity with higher efficiency than distributed generation plants of similar size and with virtually no air pollution. Molten carbonate fuel cells produce base load electricity giving commercial and industrial customers greater control over their power generation economics, reliability and emissions. Headquartered in Danbury, Conn., FuelCell Energy services over 50 power plant sites around the globe that have generated more than 128 million kilowatt hours.
Enbridge Inc., a Canadian company, is a leader in energy transportation and distribution in North America and internationally. As a transporter of energy, Enbridge operates, in Canada and the United States, the world's longest crude oil and liquids pipeline system. As a distributor of energy, Enbridge owns and operates Canada's largest natural gas distribution company, and provides distribution services in Ontario, Quebec, New Brunswick and New York State.
This looks like something Primary Energy would come up with.
Unfortunately, neither the press release nor the company web site have many details on how this works. Thermodynamically, it would be more efficient to pre-heat the natural gas before the expansion turbine; this would yield more turbine work than expansion of cold gas followed by re-heat.
Posted by: Engineer-Poet | November 07, 2006 at 11:30 PM
Using expensive and CO2 producing natural gas in boilers to reheat the natural gas after the cooling effect of reducing the pipeline pressure to local distribution pressure is a sorry waste.
Using the turbine to recover energy from the compressed gas is a step in the right direction, but then operating the fuel cell to provide heat to the cold gas is problematic.
A geothermal heat pump that runs directly off that turbine and uses free ground heat to reheat the natural gas is a much more efficient setup.
It is nice to see utility scale fuel cells get some investment and publicity, but this application is flawed.
Just like the wasteful oil industry practice of using oil byproducts to provide process heat for oil refining. That approach is burning up 20% of the oil we use.
And how did that natural gas in the pipeline get up to operating pressure? Natural gas powered internal combustion engines driving huge compressors. Burning more natural gas at very low efficiency.
All process and pipeline transportation energy possible for expensive, CO2 producing fossil fuels ought to come from renewables instead.
Posted by: amazingdrx | November 08, 2006 at 10:07 AM
I am no expert in thermodynamics, but from what I see, any energy savings in this system come only from being able to make effective use of the waste heat from the fuel cells. Since the turbine extracts energy from the process of lowering the pressure of the natural gas, the temperature of the gas exiting the turbine would be lower than the temperature of gas exiting a simple expansion valve. Thus MORE heat is needed to warm the gas up to distribution temperature. However, with this system there is a use for the rather low quality heat from the fuel cells.
IF one is going to use natural gas for generating electricity, this is probably a good way to do it, since the waste heat gets used to do something that needs to get done anyway (reheating the gas), rather than just getting thrown away.
If, on the other hand, one only wants to lower the gas pressure and reheat it, a geothermal source heat pump run by the turbine would be the most efficient (as Engineer-Poet has pointed out).
Posted by: donb | November 08, 2006 at 10:39 AM
Don I think renwable energy powered heat pumps operating from geothermal and waste heat applied to refining, processing, distillation and many other heat intensive industrial processes could save a large portion of energy now provided by combustion.
When the wind and sun are providing excess energy switch on the refining or distillation plant in effect storing that extra renewable energy in the refined or distilled product.
When demand and supply dictate it, shut the plants down for awhile to adjust demand.
Along with geothermal home and building heating, I think this industrial use of heat pumps would save one third of the power we now get from cO2 producing combustion of expensive fuels like fuel oil, natural gas, and propane.
Posted by: amazingdrx | November 08, 2006 at 11:04 AM
These systems have to run reliably for 24/7 365 days a year so no renewable source will do that without a week or more of expensive energy storage. You could supplement the grid with renewable power at a central location, but I don't think that is what drx is talking about.
They provide the reheating of the gas as well as producing the electricity, most of which they can sell, as the parasitic loads are likely to be small. They still need back up power, presumably from the grid to operated the valves. I don't know how they heat the gas in case of failure of the fuel cell, they say they have eliminated the boiler. Heating from the grid with electricity would seem to be almost expensive as having a boiler.
Posted by: Jim from The Energy Blog | November 08, 2006 at 12:22 PM
Jim, the likely market for this system is existing pressure management facilities which will already have the necessary heating rig. The existing heater can back up the fuel cell; when they say "eliminated" I believe they mean functionally eliminated when the fuel cell system is running.
Posted by: pbean | November 08, 2006 at 01:53 PM
FWIW, most gas pipelines appear to use electric compressors. This would effectively make them coal-fired in much of the USA. Low efficiency makes little sense; why would a gas company waste energy, especially if it meant losing product? But on to the thermodynamics of this scheme (which I am qualified to comment on).
The ratio of specific heats of methane is 1.27; starting at 293 K and expanding by an 8:1 pressure ratio with 80% efficiency, the outlet temperature would be 209 K - about -64° C. To get gas through the same expander at 293 K outlet temp, you'd need to pre-heat to ~410 K - about 137 C. The expansion work from the turbine would be about 40% greater in the second case (and so would the heat input required to bring the gas back up to 293 K).
A heat pump wouldn't do so well at such high temperatures. On the other hand, an SOFC or microturbine's exhaust would be more than warm enough to preheat the gas.
Posted by: Engineer-Poet | November 08, 2006 at 06:36 PM
pbean-
No doubt I'm missing something, but instead of preheating and then expanding, why not expand and then apply heat? While the turbine would be extract less energy this way, there might be enough to still run a heat pump. All I can think of is that there might be some formation of liquids (or solids - think water vapor) on the cold temperature side before reheat.
If using a heat pump for the heat source, a mitigation strategy would be to de-superheat the compressor output at the turbine inlet (warming the turbine input gas), and then heating the turbine outlet gas by condensing the refrigerant of the heat pump system. If the temperature drop in the turbine is still too large before reheat, a heat exchanger could be inserted at the mid point of the turbine.
Posted by: donb | November 09, 2006 at 09:57 AM
Expanding before heating allows ice to form inside the expander. As the Russians will tell you, this is a bad thing.
The reason not to use a heat pump and a re-heat is quite simple: the electricity from the fuel cell and turbine is quite valuable, and a pre-heat gets more energy out of the same equipment than a re-heat. Last, using the waste heat from the fuel cell can raise its effective efficiency from 60% to almost 90%; that's mighty hard to beat.
Posted by: Engineer-Poet | November 09, 2006 at 07:43 PM
what is the cost of power it can generate USDper kwhr and return of investment
Posted by: ariel d. catignas | November 28, 2006 at 03:21 AM
Global warming and pollution control is the most neglected topic in the academe and profit oriented business association around the world ,due to greediness for profit, As a concern engineers we need to review our orientation regarding the technology of harnessing energy which is the major source of pollution and global warming, instead of using the technology for our benefits as a life support system, this technology is now destroying our morality, our planet and our life support system. God gave us natural source of energy from sun, moon, sea, lakes river, gravity, wind ,hot and cold weather, which are already at the surface of the planet. Next, we need to learn on how to balance everything in this planet, God created this planet and the whole universe in balance, any unbalance will created disaster and death , but if we maintain the balance it will maintain and reproduce life support system. God put under the surface of the earth all harmful materials ,if it is under the surface earth,it not for the consumption of mankind, if you get something under the earth,you need also to put something equivalent to replace it and if you take out material from under ground into earth surface and atmosphere see to it that you should put something in surface and atmosphere to absorb all those materials and return it under the earth. We need to focus on technology that will not cause the unbalance on earth's life support system by harnessing renewable source of energy and developing nano technology that will produce super energy efficient machines and using biodegradable materials.
Posted by: Ariel D. Catignas | January 16, 2008 at 05:04 AM
Ariel, you may want to stop by the Environmental Engineering Department of your local major university if you think AGW and pollution control are neglected topics. All major energy projects in the US require an EIS to consider the environmental impact.
Posted by: Kit P | January 16, 2008 at 08:44 AM
Re engineering our technology to keep our environment safe from Pollution should be the urgent priority of every individual and every nation.
We are in the Dark age of Energy that most engineers have no idea on other source of energy , that only the petrolium and radioactive materials were the efficient and ultimate source of energy with out considering the danger to living things on this planet.
Rich Nations were spending trillions of dollars to find another planet instead of giving funds for the researchers on how to harness energy that keep the clouds afloat in the air , energy source of lighting and thanderbolt. To harness earths gravity without using water and keep our forest intact.
If we didnot take a drastic change on our present technology , we will continue to experience a environmental desaster
Posted by: Mac Sakay | May 31, 2010 at 11:24 AM