Energy Efficiency of Power Production: How Supercritical Carbon Dioxide Turbines Operate

Duane M. Tilden, P.Eng.                                    Sept 1, 2018

Foreword:

This is another article in an ongoing series of reports on the technological development of supercritical carbon dioxide in the power production and energy efficiency sectors of industry, power plants and utilities.

dodge-sco23 supercritical CO2 turbine

Figure 1. Size comparison of Supercritical Power Turbine to Conventional Steam Turbine (1)

Abstract:

The ever increasing search for improving energy and power production efficiency is a natural quest as developments in technology seek to be utilized to improve operations and supply cost effectively. The technologies behind the utilization of supercritical carbon dioxide and other such fluids have long been established. We are furthering our exploration into this sector of power production developing new technologies along the way to a smarter economy and modernization of infrastructure.

The Principle of Operation

Supercritical fluids can play an important role in developing better electricity generators because of their liquid- and gas-like properties. A supercritical fluid is an optimal working fluid because it has a temperature and pressure above its critical point, meaning that it doesn’t have a definite liquid or gas phase. Consequently, the slightest changes in pressure or temperature cause huge changes in the material’s density.

With any supercritical fluid, the ease of compressibility goes up, explains Stapp, so it becomes something more like water. Because supercritical CO2 also compresses more easily than steam, the amount of work done during the compression phase—normally accounting for 25 percent of the work performed inside the system—is dramatically reduced; the energy saved there greatly contributes to the turbine’s overall efficiency.

“We expand it like a gas, and pressurize it like a liquid,” says James Pasch, principle investigator of the Supercritical Carbon Dioxide Brayton Cycle Research and Development Program. “You can do this with any fluid, but supercritical carbon dioxide matches really well with ambient temperatures.”

Carbon dioxide is optimal for this application because it doesn’t go through a phase change at any point during the cycle. Its critical temperature, 88 degrees Fahrenheit, is very close to ambient temperature, which means the heat emitted by the turbine is the same temperature as the surrounding environment. Supercritical carbon dioxide is also very dense; at its critical point, the fluid is about half the density of water. So, in addition to being easier to compress, less work is required to cycle it back to the heat source for re-expansion.

The Brayton Cycle also offers direct environmental benefits. For one, it’s carbon neutral. The system takes carbon dioxide out of the air and puts it in the recompression cycle loop. Just as important is the fact that the system limits water usage by minimizing discharge, evaporation, and withdraw.

“That’s a big deal for the southwest,” says Gary Rochau, manager of Sandia’s Advanced Nuclear Concepts Department. Sandia’s generator can work in places where water is in limited supply. This puts it on par with the Palo Verde Nuclear Power Generating Station, a nuclear power plant in Arizona that uses recycled waste water as cooling water, saving groundwater and municipal water supplies for other uses. (2)

Figure 1. Illustration of a Supercritical CO2 Turbine [Peregrine Turbine Technologies] (2)

Advances in Materials and Technology

GE Reports first wrote about Hofer last year when he 3D printed a plastic prototype of the turbine. His team, partnered with Southwest Research Institute and Gas Technology Institute, has since submitted the design to the U.S. Department of Energy and won an $80 million award to build the 10 MW turbine. The turbine features a rotor that is 4.5 feet long, 7 inches in diameter, and only weighs 150 pounds. The engineers are now completing a scaled-down, 1 MW version of the machine and will test it in July at the Southwest Research Institute.

The idea of using CO2 to power a steam turbine has been around for a while. It first appeared in the late 1960s, and an MIT doctoral student resurrected it in 2004. “The industry has been really interested in the potential benefits of using CO2 in place of steam in advanced supercritical power plants,” Hofer says.

By “supercritical” Hofer means efficient power stations using CO2 squeezed and heated so much that it becomes a supercritical fluid, which behaves like a gas and a liquid at the same time. The world’s most efficient thermal power plant, RDK 8 in Germany, uses an “ultrasupercritical” steam turbine operating at 600 degrees Celsius and pressure of 4,000 pounds per square inch, more than what’s exerted when a bullet strikes a solid object.

Hofer says that the steam power plant technology “has been on a continuous march” to increase efficiency and steam temperature, but once it tops 700 degrees Celsius, “the CO2 cycle becomes more efficient than the steam cycle.” Hofer’s turbine and casing are made from a nickel-based superalloy because it can handle temperatures as high as 715 degrees Celsius and pressures approaching 3,600 pounds per square inch. “You need a high-strength material for a design like this,” he says.

 Figure 2. GE Global Research engineer Doug Hofer is building a compact and highly efficient turbine that fits on a conference table but can generate 10 megawatts (MW), enough to power 10,000 U.S. homes. The turbine, made from a nickel-based superalloy that can handle temperatures up to 715 degrees Celsius and pressures approaching 3,600 pounds per square inch, replaces steam with ultrahot and superpressurized carbon dioxide, allowing for a smaller design.

The hellish heat and pressure turn CO2 into a hot, dense liquid, allowing Hofer to shrink the turbine’s size and potentially increase its efficiency a few percentage points above where state-of-the-art steam systems operate today. “The pressure and fluid density at the exit of our turbine is two orders of magnitude higher than in a steam turbine,” Hofer says. “Therefore, to push the same mass through, you can have a much smaller turbine because the flow at the exit end is much denser.”

Hofer’s design uses a small amount of CO2 in a closed loop. “It’s important to remember that this is not a CO2 capture or sequestration technology,” he says. Hofer says that the technology, which is being developed as part of GE’s Ecomagination program, could one day start replacing steam turbines. “It’s on the multigenerational roadmap for steam-powered systems,” he says.

By virtue of becoming more efficient, the technology could help power-plant operators reduce greenhouse gas emissions. “The efficiency of converting coal into electricity matters: more efficient power plants use less fuel and emit less climate-damaging carbon dioxide,” wrote the authors of the International Energy Agency report on measuring coal plant performance. (3)

Previous Blog Posts on Supercritical Carbon Dioxide:

  1. https://duanetilden.com/2016/11/11/transitioning-oil-gas-wells-to-renewable-geothermal-energy/
  2. https://duanetilden.com/2016/03/13/supercritical-co2-used-for-solar-battery-power-system/
  3. https://duanetilden.com/2015/04/23/doe-invests-in-super-critical-carbon-dioxide-turbine-research-to-replace-steam-for-electric-power-generators/
  4. https://duanetilden.com/2013/10/29/supercritical-co2-refines-cogeneration-for-industry/
  5. https://duanetilden.com/2013/10/29/supercritical-co2-turbine-for-power-production-waste-heat-energy-recovery/
  6. https://duanetilden.com/2013/10/29/waste-heat-recovery-using-supercritical-co2-turbines-to-create-electrical-power/

 

References:

  1. supercritical-carbon-dioxide-power-cycles-starting-to-hit-the-market/
  2. supercritical-carbon-dioxide-can-make-electric-turbines-greener
  3. ecomagination-ge-building-co2-powered-turbine-generates-10-megawatts-fits-table/
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UBC Report Findings Show Better Options Than Site C Dam

Keywords: UBC, Site C, Hydro, Dams, Energy, Electricity, Renewable Energy, Employment, Jobs, Environment, Sustainable, Conservation, Water, Governance, British Columbia

In a November 23 report issued “by a team of researchers led by Dr. Karen Bakker ” finds “Site C creates fewer jobs and has larger environmental impact.” (1)

“[…New Research Report: Comparative Assessment of Site C Employment (17 November 2017)

A new UBC report compares employment numbers from Site C versus the alternatives, and concludes: stopping Site C will create a larger number of sustainable jobs in the province, including in the Peace Region.

UBC’s Program on Water Governance has conducted a detailed comparison of employment generated by Site C versus the alternative portfolios put forward by BC Hydro and the BCUC.

  • Our analysis indicates that terminating Site C and pursuing the alternatives results in modest job losses in the short term, and substantial job gains in the medium and long-term.
  • These jobs are generated by remediation, conservation, and alternative energy projects.
  • Terminating Site C and pursuing any alternative portfolio creates a higher number of sustainable jobs in the province, including in the Peace Region.
  • Site C provides the least jobs per dollar spent.

…]” (1)

References:

  1. SITE C DAM

High Efficiency Clothes Washers

Nowadays we are searching for more ways to be energy efficient at home, work and elsewhere.  Our resources are not infinite, even if they are renewable. And, as such, we should be seeking ways to reduce our energy and water consumption, not only to be a good citizen but also for the money it saves which can be utilized elsewhere.

Yesterday I did my laundry, packed all my smelly and soiled clothes in a plastic garbage and headed off to the laundromat in Canmore. I chose a double loader which cost $4 + another buck for the heavy soiled clothing option. Not sure how this thing worked, I bought two small boxes (it’s a double loader after all so two boxes should do, I thought) of Tide for a buck apiece.
Samsung WF210ANW High Efficiency Washer

Figure 1.  Image of a Samsung’s WF210 HE Washing Machine top loading washing machine. (1)

The instructions on the machine were not clear, so I opened the boxes and sprinkled them on my clothes, set the temp for warm and started the machine. It was a 30 min cycle, and after about 5 minutes I did not see any appreciable amount of water in the washer, also I noticed that there was a slot for the detergent. So, I decided to buy another box of detergent and put it into the pull out. The machine was on 10 minutes now, and still no water… wtf?

Image result for high efficiency washing machine

Figure 2.  Graphic comparing a HE washing machine to a traditional top loader. (2)

Okay, so I call the management which operated the local motel, informing them that the machine is broken, and a girl comes out to see what is going on. She assures me it’s fine and working, that the machine uses very little water. Okay, I am skeptical and concerned that with so much detergent and very little water my clothes would not get clean and be covered with a residue.

In the meantime a nice German lady comes over to me and says that she has never seen a top loader before and they only use front loading machines where she is from. I laughed and told her that in Canada we have a tendency to waste our resources as we have so much, whereas in Germany they have a larger population crammed in a small country. The government of Canada has a tendency to give lip service to energy and water efficiency.

The end result was that the clothes came out brilliantly clean with no residue. Most of the water was spun out and the clothes were only slightly damp, which meant that my dryer time was greatly reduced. The amount of heated water and energy used for drying is greatly reduced. Is it not time to get rid of the energy hogs?

 

References:

(1)  High Efficiency Washing Machines Save Money With Less Water, Energy

(2)  High Efficiency Washing Machine

Water Conservation and a Change in Climate Ends California Drought

Water scarcity is becoming a greater problem in our world as human demands for water increases due to population growth, industry, agriculture, and energy production. When the water supply is being pushed beyond its natural limits disaster may occur.  For California residents the end of the drought is good news.  Return of wet weather raises reservoir levels and effectively prevents wildfires.  However, another drought could be around the corner in years to come.  Thus government and water users need to remain vigilant and continue to seek ways to conserve and reduce water use.
ca-reservoirs 2017 End of drought.png
Figure 1. 2017 California Major Water Reservoir Levels
By Bark Gomez and Yasemin Saplakoglu, Bay Area News Group (1)
Friday, April 07, 2017 05:17PM

Gov. Jerry Brown declared an end to California’s historic drought Friday, lifting emergency orders that had forced residents to stop running sprinklers as often and encouraged them to rip out thirsty lawns during the state’s driest four-year period on record.

The drought strained native fish that migrate up rivers and forced farmers in the nation’s leading agricultural state to rely heavily on groundwater, with some tearing out orchards. It also dried up wells, forcing hundreds of families in rural areas to drink bottled water and bathe from buckets.

Brown declared the drought emergency in 2014, and officials later ordered mandatory conservation for the first time in state history. Regulators last year relaxed the rules after a rainfall was close to normal.

But monster storms this winter erased nearly all signs of drought, blanketing the Sierra Nevada with deep snow, California’s key water source, and boosting reservoirs.

“This drought emergency is over, but the next drought could be around the corner,” Brown said in a statement. “Conservation must remain a way of life.” (2)

References:

  1. https://wattsupwiththat.com/2017/04/08/what-permanent-drought-california-governor-officially-declares-end-to-drought-emergency/ 
  2. http://abc7news.com/weather/governor-ends-drought-state-of-emergency-in-most-of-ca/1846410/

Energy Efficiency Financing for Existing Buildings in California

Much of our efforts to reduce carbon emissions involves fairly complicated and advanced technologies. Whether it’s solar panels, batteries, flywheels, or fuel cells, these technologies have typically required public support to bring them to scale at a reasonable price, along with significant regulatory or legal reforms to accommodate these new ways of doing old things, […]

To recommend policies to boost this capital market financing for energy retrofits, UC Berkeley and UCLA Law are today releasing a new report “Powering the Savings:How California Can Tap the Energy Efficiency Potential in Existing Commercial Buildings.” The report is the 17th in the two law schools’ Climate Change and Business Research Initiative, generously supported by Bank of America since 2009.

The report describes ways that California could unlock more private investment in energy efficiency retrofits, particularly in commercial buildings.  This financing will flow if there’s a predictable, long-term, measured and verified amount of savings that can be directly traced to energy efficiency measures.  New software and methodologies can now more accurately perform this task.  They establish a building’s energy performance baseline, calibrating for a variety of factors, such as weather, building use, and occupancy changes.  That calibrated or “dynamic” baseline can then form the basis for calculating the energy savings that occur due specifically to efficiency improvements.

But the state currently lacks a uniform, state-sanctioned methodology and technology standard, so utilities are reluctant to base efficiency incentives or programs without regulatory approval to use these new methods.  The report therefore recommends that energy regulators encourage utilities to develop aggressive projects based on these emerging metering technologies that can ultimately inform a standard measurement process and catalyze “pay-for-performance” energy efficiency financing, with utilities able to procure energy efficiency savings just like they were a traditional generation resource. […]

via Solving The Energy Efficiency Puzzle — Legal Planet

96 Million ‘Shade Balls’ Installed to Cover L.A.’s Reservoirs

A California woman, for one, who wants to ease the drought, put disabled vets to work, and make some money

Sourced through Scoop.it from: www.bloomberg.com

>” […] The shade balls of Los Angeles are 4 inches in diameter, hollow, polyethylene orbs […] The Los Angeles Department of Water and Power has now dumped 96 million balls into local reservoirs to reduce evaporation and block sunlight from encouraging algae growth and toxic chemical reactions. The balls are coated with a chemical that blocks ultraviolet light and helps the spheres last as long as 25 years. Las Virgenes, north of L.A., now uses shade balls, too. […]

The U.S. Environmental Protection Agency has encouraged the nation’s water managers in recent years to find ways to cover or contain their resources, to prevent sunlight from reacting with chlorine and possibly creating carcinogens, says Ed Osann, a senior policy analyst at the Natural Resources Defense Council. The shade balls shouldn’t pose a pollution problem in themselves, he says, since “everything that comes in contact with drinking water has to be a certified material.” Chase says the balls are designed not to degrade.

The shade balls are a novel way to protect drinking water, and Californians’ latest attempt to adjust to their four-year drought. […]”<

See on Scoop.itGreen & Sustainable News

Water Waste, Leaking Pipes and Infrastructure Maintenance

Imagine Manhattan under 300 feet of water, not from a flood or rising sea level, but from the 2.1 trillion gallons of water lost from leaky pipes every year. That is nearly 6 billion gallons a day! The majority of leaks are a result of old infrastructure, pressure changes in the water mains, and small household leaks.

Source: theenergycollective.com

>”[…] Infrastructure leaks

About 14-18% of water treated in the United States is wasted through aging and damaged infrastructure, as well as faulty meters. The American Society of Civil Engineers recently gave the US a “D” grade for water infrastructure. Let’s take a look at a few cities around the US.

Chicago wastes about 22 billion gallons of treated water a year, enough to serve 700,000 individual needs for a whole year.The state of California loses about 228 billion gallons a year, which is more than the city of LA uses in a year. On average the state loses 49 gallons a day for every service connection, and Sacramento loses a whopping 135 gallons per connection.In 2013 San Francisco experienced over 100 water main breaks and New York averages over 400 a year.Houston lost 22 billion gallons of water in 2013, 15% of its total water supplyAccording to the EPA we lose about 34 billion gallons of drinking water a day in the United States, about 1/6 of public water systems supply.

Household water waste

Average household leaks can add up to over 10,000 gallons of water a year, enough water to wash 270 loads of laundry. Nationally, household water waste totals over a trillion gallons – or the equivalent of 11 million households’ yearly usage. The most common types of leaks at the household level are worn toilet flappers, dripping faucets, and leaky showerheads. 10% of US homes waste over 90 gallons a day just from these small fixtures. Here are some quick facts:

  • Faucets: 1 drip/second adds up to over 3,000 gallons a year (you can take 180 showers with that water!)
  • a showerhead leaking at 10 drips/minute wastes over 500 gallons a year (that’s 60 loads of dishes)
  • Old inefficient toilets can water up to 13,000 gallons a year
  • Irrigation leaks just the size of a dime will waste nearly 6,300 gallons a month

[…] Fixing easy leaks can save about 10% on your monthly water bill. Replacing that old toilet with a new efficient toilet could save you upwards of $2,400 over the toilet’s lifetime. […]”<

See on Scoop.itGreen & Sustainable News

Water Prices in 2015 Up 6 Percent in 30 Major U.S. Cities

Continuing a trend that reflects the disrepair and shows no sign of slowing, the price of residential water service in 30 major U.S. cities rose faster than the cost of nearly every other household staple last year …

Source: www.circleofblue.org

>” […] The economics of water — particularly the cost of treatment, pumping, and new infrastructure, as well as the retail price for consumers — gained renewed prominence as California and Texas, America’s two most populous states, face historic droughts and water managers seek to rein in water consumption, with price increases as one tool in their arsenal.

The average monthly cost of water for a family of four using 100 gallons per person per day climbed 6 percent, according to data collected from the utilities. It is the smallest year-to-year change in the six-year history of the Circle of Blue survey but comparable to past years. The median increase this year was 4.5 percent. In comparison, the Consumer Price Index rose just 1.8 percent in the 12 months ending in March, not including the volatile food and energy sectors. Including food and energy, prices fell by 0.1 percent.

For families using 150 gallons and 50 gallons per person per day, average water prices rose 6 percent and 5.2 percent, respectively.

The survey results reflect broad trends in the municipal water industry that nearly every U.S. utility must grapple with, according to Andrew Ward, a director of U.S. public finance for Fitch Ratings, a credit agency.

Distribution pipes, which can branch for thousands of miles beneath a single city, have aged beyond their shelf life and crack open daily. Some assessments peg the national cost of repairing and replacing old pipes at more than $US 1 trillion over the next two decades. In addition, new treatment technologies are needed to meet Safe Drinking Water Act and Clean Water Act requirements, and cities must continue to pay down existing debts. At the same time, conservation measures have proven successful. Utilities are selling less water, but they still need big chunks of revenue to cover the substantial cost of building and maintaining a water system. All together, these and other factors amount to a persistent upward pressure on water rates. […]

See on Scoop.itGreen & Sustainable News

Closed Loop Cooling Saves Millions of Gallons of Water in Texas Combined Cycle Natural Gas Power Plant

Source: gereports.ca

>” […] Instead of water, each of the two plants will use two powerful air-cooled “Harriet” gas turbines and one air-cooled steam turbine developed by GE. “The technology uses the same cooling principle as the radiator in your car,” Harris says. “You blow in the air and it cools the medium flowing in closed loops around the turbines.”

The power plants, which are expected to open next year, will be using a so-called combined cycle design (see image below) and produce power in two steps. First, the two gas turbines (in the center with exhaust stacks) extract energy from burning natural gas and use it to spin electricity generators. But they also produce waste heat.

The system sends the waste heat to a boiler filled with water, which produces steam that drives a steam turbine to extract more energy and generate more power.

But that’s easier said than done. The steam inside the steamturbine moves in a closed loop and needs to be cooled down back to water so it could be heated up again in the boiler. “Normally, we cool this steam with water, which evaporates and cools down in huge mechanical cooling towers,” says GE engineer Thomas Dreisbach. “A lot of the cooling water escapes in those huge white clouds you sometimes see rising from towers next to power plants.” The Exelon design is using a row of powerful fans and air condensers (rear right) to do the trick and save water.

Similar to the steam turbines, GE’s Harriet gas turbines also use air to chill a closed loop filled with the coolant glycol and reduce the temperature inside the turbine. The combined efficiency of the plant will approach 61 percent, which in the power-generation industry is like running a sub 4-minute mile. […]”<

 

 

See on Scoop.itGreen Energy Technologies & Development

Industrial Plant to be Re-Developed into Mega-Indoor Vertical Farm Factory

AeroFarms, a leading commercial grower for vertical farming and controlled agriculture, together with property management firm RBH Group, a slew of investment partners along with the City of Newark and the New Jersey Economic Development Authority (NJEDA) announced the intent to redevelop a former industrial site in Newark’s Ironbound district into a state-of-the art 69,000 square foot indoor vertical farm.

Source: archinect.com

>” […] Currently under construction, the first phases will open in the second half of 2015, creating approximately 78 jobs in a local community with an unemployment rate that is twice the national average. Additionally, AeroFarms has partnered with the Ironbound Community Corporation to create a recruiting and job training program targeting local residents.

The building is located on a 3-acre industrial site in the center of the Ironbound community in Newark, NJ. It is adjacent to elevated truck Route 1 and 9, a freight rail right of way, and to other industrial businesses along Rome and Christie Streets.

When completed, AeroFarms will have the capacity to grow up to 2 million pounds per year of baby leafy greens and herbs in an environmentally controlled, safe, and sanitary facility. It will provide healthy foods to the local community as well as to other markets. AeroFarms is a model for successful, sustainable farming offering 75 times more productivity per square foot annually than a traditional field farm while using no pesticides and consuming over 95% less water. […]”<

See on Scoop.itGreen & Sustainable News