Category Archives: Process Heat

DCFC: An Ecologically Friendly Technology

Direct Carbon Fuel Cells are based on coal gasification technology. This technology has already been around for about a century and may yet prove to be a 21st century base-load energy source, and help free our grids from the emissions of traditional coal and natural gas.

Basically, after a high temperature conversion process gasified coal can be consumed by an electrical power station and generate nearly twice the energy of coal while halving the GHG waste! For those concerned with emissions or climate change, this means that modified coal could emit about 250 grams of CO² per KW/hr or 550 pounds of CO² per MW/hr – however you’d prefer to measure emissions. This is about the levels originally outlined in the EPA’s Clean Power Plan, but much closer to needed reductions. Also, gasifying the coal will eliminate solid fly ash and allow extraction of other impurities.

DCFC's will have a capacity factor of 65 percent - with ultra low emissions.

DCFC’s will have a capacity factor of 65 percent – with ultra low emissions. Graph based on NEI data.

 

The Energy Reality Project would like to re-post two pieces on this subject.
One from (Th)e Kral Spaces, a blog generally concerned with the nuclear biosphere. The other is a guest post by Robert Steinhaus at the Molten Salt Science International’s beta site.
Please, feel free to leave any constructive comments or questions below.

 

Coal energy cheaper than coal energy”
as originally posted at https://kralspaces.wordpress.com/

The only reason China is investing in everything possible for their energy mix is because they need more energy then they can generate. Once their energy catches up to their demand they will be able to take a serious look at what energy sources are the most efficient and narrow their scope to what can be considered clean energy. Once their focus on quantity is turned to quality, hopefully they will still include fossil fuels. Really?

There is a needed mix for energy and it includes fossil from my perspective. I struggle to understand why the Obama Administration wants to throw coal under the bus. If we change the way we look at coal, it too can be a cleaner energy source. If we convert coal to electricity via electrochemical oxidation without burning it, we can generate twice the electricity with half the coal and manage the waste without a variety of toxins ever getting release into the atmosphere. We have managed nuclear waste for 60 years so we already know how to do it safely.

The concept is called Direct Carbon Fuel Cells (DCFC) and Lawrence Livermore National Labs (LLNL) has demonstrated this technology as far back as 2005. Why no one is interested in this solution stuns me just like the Molten Salt Reactor (MSR) oversight for clean safe nuclear energy did fifty years ago. Natural gas and oil can also be used as a source for this DCFC process and the best part is that it already comes with an existing commercial electrical power generation infrastructure.

I’ve written a short paragraph about DCFC in a previous column but I strongly believe the Unites States Coal Industry needs to take a serious look at this potential technology. There are several reasons why I take this position and the first and most obvious is that the Coal Industry is on the chopping block with the latest EPA regulations. The new regulations have to do with clean air and water from the coal burning process to generate electricity. The EPA itself admits that the plan’s usefulness against the threat of climate change will be so small that it will be impossible to measure. If you eliminate the ‘burning of coal’, you eliminate the need for new regulations and many of the older regulations as well.

Coal is the cheapest source we have to generate electricity today. The fact that there is already a well established infrastructure for mining coal, it only makes business sense to leverage that infrastructure and only change that process which needs to be changed – the burn. At a fraction of the cost to build an equivalent nuclear power plant or renewable wind and solar farm, a new DCFC Converter can be built right next to the existing coal furnaces and the output fed directly into the electrical grid without having to go through a secondary steam turbine process. Wow! That would lower the cost of processing tremendously and make electricity generation from coal cheaper than coal. There is a little sarcasm in that last sentence because coal is the cost baseline for all other energy sources.

There is a book I read recently titled “The Moral Case for Fossil Fuels” and it addresses the abundance of what fossil fuel has contributed to our extraordinary life style. Even as an advocate of nuclear energy, I just don’t understand the reasoning behind those you want to shut down coal production when clean coal can be achieved if we wanted to commit the effort to it.

DCFC Ref. Link: http://www.pennenergy.com/articles/pennenergy/2015/02/direct-carbon-fuel-cells-an-ultra-low-emission-technology-for-power-generation.html


DCFCs can give twice the efficiency of a coal plant for about half the price
as originally posted at http://mssci.com/

Robert Steinhaus contributed this about Direct Carbon Fuel Cells that can run on coal granules.

Molten Carbonate salt Direct Carbon Fuel Cells do not use a turbine-generator to convert heat to electricity. Each DCFC collects electrical charge internally on graphite electrodes inside the cell so a DCFC directly converts the chemical energy in coal into DC electricity. DCFC cells operate at high temperatures comparable to Molten Salt Nuclear Reactors (about 750 degrees C) and high temperature steels have to be used to make the fuel cells.

It is a feat to make a high temperature coal fired plant operate at more than 44% thermodynamic efficiency. DCFCs convert the chemical energy in coal to electricity at a repeatedly demonstrated efficiency of 80%. There is not Brayton turbine-generator on the planet that can approach the efficiency of DCFCs, and DCFCs do their job much more inexpensively than Brayton or Rankin turbines, have fewer moving parts, and require less maintenance.

Some downsides of DCFCs –
DCFCs have to operate at elevated temperatures between 700 – 750 degrees. To initially start a DCFC you have to heat the cell from an external source, although once started, internal exothermic heat of reaction will keep a cell at temperature.

DCFCs tend to be physically large cells for the power you can instantaneously draw from them (lower power density by weight). A DCFC might typically be 4X the volume of a natural gas or hydrogen PEM fuel cell which supplies the same amount of electrical power.

Since turbine generators are about half or more of the cost of most thermal fossil plants like coal fired power plants – not requiring a precision high temperature turbine-generator saves about half of the cost of a traditional coal power plant and make DCFCs very very high efficiency (80%) and very cheap (about half the cost of the nearest coal fired power plant competitor).

Small several hundred watt practical DCFC cells have been built at LLNL National Lab and operated for several months demonstrating 80% conversion efficiency. Commercial DCFC cells would be much larger and perhaps produce 10s of Megawatts of power each. Such large cells would turn high chemically energy dense coal into electricity directly without burning the coal. How often you have to replenish the DCFC cell would depend on how much power you draw out of the cell. You would get twice as much electricity from a given amount of coal using the fuel cell as you would get from burning the same amount of coal in a coal fired power plant.

The vast majority of the volume and weight of coal that you load into a DCFC fuel cell disappears into clear, colorless, and odorless CO2 gas that goes up a vent to the atmosphere or can be can be used in an industrial process or sequestered underground (no smoke, particulates, radiation, or other pollution into the environment to foul the local air quality). There is a ash or char produced by the cell which is around 5% by weight of the coal loaded into the DCFC. This ash/char has to be periodically removed from the fuel cell and disposed (when processed and the molten salts recycled – the char makes decent soil amendment for agricultural soils)

Answers to Frequently Asked Questions about Direct Carbon Conversion” by John Cooper
https://e-reports-ext.llnl.gov/pdf/317376.pdf

Editors Note: Here are some additional web-sites to learn about DCFC and the coal gasification process.  Start with an animation profiling the full process- https://vimeo.com/93110188

Atlanta based Southern Company is an energy provider with a DCFC program-
www.southerncompany.com/what-doing/energy-innovation/smart-energy/smart-power/kemper.cshtml
www.elp.com/articles/2014/04/southern-co-to-study-coal-power-with-chinese-state-firm.html

A more technical look at DCFCs, which will likely have capacity factors of 65%.
www.materialsviews.com/direct-carbon-fuel-cells-ultra-low-emission-technology-power-generation/

China has a strong program for alternate uses of coal as well-
http://instituteforenergyresearch.org/analysis/china-build-50-coal-gasification-facilities/
http://english.sxicc.cas.cn/st/rdds/200906/t20090601_19682.html

California’s Water Emergency – A Solution Worth Considering

by the TESV folks in California

When considering options for energy production in drought stricken geographies like California, nuclear energy plants such as The San Onofre Nuclear Generating Station (SONGS), should be highlighted for the role they can play in meeting our energy needs, while not consuming an abundance of freshwater resources. During its operation, SONGS conserved approximately 126,548 gallons of freshwater per hour and produced enough energy to desalinate 668 trillion gallons of water a year. (2 million acre-feet.)

Ninety percent of the electricity produced in the United States comes from fossil fuel and nuclear power plants, which require large quantities of water for cooling steam (that is used to spin turbines that generate electricity) back to water that can be reused in the electricity generation process. Each type of power plant requires different amounts of water for cooling. For example, once-through cooling systems (such as the one used at SONGS) for nuclear power plants consume 400 gallons/MWh, coal power plants consume 300 gallons/MWh, and natural gas power plants consume 100 gallons/MWh. Once-through systems most commonly use freshwater from rivers, lakes, or aquifers, thus consuming water that could be used for agriculture, industry, and residential consumption. However, some power plants built near the ocean, like the SONGS, incorporate seawater into their once-through cooling system and require very little freshwater, leaving valuable water resources available for other purposes.

During its operation, SONGS produced 19% of the power used by Southern California Edison customers, supplying power to large portions of Southern California. Operating at full capacity from 1984-2011, units 2 and 3 of SONGS had a gross capacity of 1,127 MW and supplied on average 7,592 GWh of electricity a year and required the use of very little freshwater resources. The negative impacts of SONGS closure on the environment is already being realized. Carbon dioxide emissions from California’s power generation facilities increased from 30.7 million tons in 2011 to 41.6 million tons in 2012 in part due to the early closure of SONGS. Furthermore, millions of gallons of water that could be used for a multitude of other purposes have been used in fossil fuel energy production processes to replace the electricity once produced by SONGS. During its operation, SONGS conserved approximately 126,548 gallons of freshwater per hour (see calculations and assumptions below) that would have been used to produce the same amount of energy from other sources.

Furthermore the energy produced by SONGS could have been used in other ways to address water scarcity issues in California. For example, the average energy supplied through SONGS could have desalinated 668 trillion gallons of water a year, (2 million acre-feet) assuming it takes 3kWh to desalinate one cubic meter of water. That is enough water produced each year to supply San Diego’s population of over 3 million people with 119 gallons of freshwater (San Diego County’s daily average per capita) every day for five years.

Producing water locally would have also saved a considerable amount of energy that is required to pump water from reservoirs to Southern California. It requires on average 2908 kWh of energy to supply Southern California with one acre-foot (326,700 gallons) of water. Therefore during an average year, SONGS could have desalinated enough water locally, saving 5948 GWh of energy a year that would otherwise be required to pump water to Southern California.

Freshwater Conservation Calculations and Assumptions

Assuming the majority of the energy produced at SONGS would be used by Southern California Edison (SCE) customers, SCE’s energy mix can be used to determine what proportion of energy sources would be needed to make up for the loss of 7592.9 GWh of electricity SONGS supplied on average each year.

 SCE Energy Mix for 2006 (the most recent energy mix data):

  • Natural Gas: 54%

  • Coal: 8%

  • Nuclear: 17%

  • Large Hydro: 5%

  • Renewables: 16%

If energy production was ramped up proportionally across the energy mix of the SCE, each energy source would need to produce the following additional energy:

  • Natural Gas: 4,100.166 GWh (54% of 7,592.9)

  • Coal: 607.432 GWh (8% of 7,592.9)

  • Nuclear: 1290.793.59 GWh (17% of 7,592.9)

  • Large Hydro: 379.645 GWh (5% of 7,592.9)

  • Renewables: 1214.864 GWh (16% of 7,592.9)

According to the Nuclear Energy Institute, natural gas, coal, and nuclear consume the following amount of freshwater to produce electricity:

  • Natural Gas: 100 gallons MWh

  • Coal: 300 gallons MWh

  • Nuclear: 400 gallons MWh

Which would result in the following freshwater consumption a year:

  • Natural Gas: 410,016,600 gallons (4,100,166 MWh * 100 gallons MWh)

  • Coal: 60,743,200 gallons (607,432 MWh  * 300 gallons MWh)

  • Nuclear: 129,079,300 gallons (1,290,794 MWh * 400 gallons MWh)

  • Total: 1,108,563,400 gallons

Therefore during its operation in 2006, SONGS conserved 1,108,563,400 gallons of freshwater a year or 126,548 gallons of water an hour, that would have otherwise been used by other power generation processes to produce the same amount of energy.

So if you’re thinking that San Onofre Nuclear Plant should not have been closed then you get it.