Design for creating a extra low CO2 Emission coal fired power plant!
I see the following as an interim measure till more cleaner power generation station namely geothermal stations can be built to meet societies needs for energy. As time progresses the least efficient coal burning stations can be the first ones to be phased out as the geothermal power stations come on line.
With the establishment of a process to convert CO2 into petrol means that by coupling them with a coal fired power generation station will allow for nearly zero CO2 emissions.
The energy required for the conversion of the CO2 to petrol can be derived from not the main generation plant but by the use of Stirling engines using the waste heat created by the combustion of the coal.
It amazes me that in all the years that electrical power stations have been running, converting the energy in coal into electrical power that 52% to 64% of the energy released by the coal has been going up the chimney! ---That equates to Bad Economics!---
What this means to you the consumer for every hundred dollars you spend on electricity you are paying the electricity-generating companies $36 to $48 to pollute the atmosphere. Whilst the remainder is your actual electricity costs.
In any electrical or mechanical system the power available to do work is related to the losses in the system. Simply stated the “energy out equals the energy in minus the losses in the system.”
In formula format “Eout = Ein -Eloss” This is also the efficiency of the system.
For a coal power plant with a 40% efficiency, it takes an estimated 325kg (720lb) of coal to power a 100-W light bulb for one year. That means 195kg ( 430lb) of coal was converted in to waste in the form of heat and CO2 to light that 100-W light bulb for a year.
There is a mechanical device that could be used to harness this waste heat energy. It is called a “Stirling Engine”
Stirling engine – Is a closed-cycle regenerative heat engine with a permanently gaseous working fluid. Operates by the cyclic compression and expansion of air or other gases. The inclusion in the design of a regenerator is what differentiates the Stirling engine from other closed cycle hot air engines.
In a thermodynamics – “Closed-cycle” is defined as a thermodynamic system in which the working fluid is permanently contained within the system, whilst regenerative describes the use of a specific type of internal heat exchanger and thermal store, known as a regenerator.
Originally conceived in 1816 by Rev. Stirling as an industrial prime mover to rival the steam engine, but its practical use was largely confined to low-power domestic applications for over a century.
The Stirling engine is noted for its high efficiency compared to steam engines, quiet operation, and the ease with which it can use almost any heat source. This compatibility with alternative and renewable energy sources has become increasingly significant as the price of conventional fuels rises, and also in light of concerns such as Peak Oil and Climate Change. This engine is currently exciting interest as the core component of micro combined heat and power (CHP) units,and as sub-unit in the propulsion of conventional submarines.
Due to the reduced number of moving parts it is virtually maintenance free and can be designed so that there is no need to convert the reciprocating motion to rotary motion to generate electricity.
The best fluid to use in a Stirling engine is hydrogen due to its ability to uptake a lot of heat energy quickly and to give it up just as quickly. But this gas has drawback in that metals are porous to it and hydrogen also causes metals to become brittle. This is one of problems that face designers who want to build a car powered by hydrogen. The next best fluid is helium but its heat uptake is not as effective as hydrogen but it does not have the drawbacks that hydrogen has.
This is the Specific heat capacities of H & He
Hydrogen [H] (25 °C) (H2) 28.836 J·mol−1·K−1
Helium [He] (25 °C) 5R/2 = 20.786 J·mol−1·K−1
Though any gas can be used including air but when using air there is a possibility of an oxygen/oil explosion in the cylinders of the engine when it is run at high pressures and temperatures.
Having said all that I have noticed that there are three positions where the Stirling engines could be placed to extract the waste energy from a thermal power station other than a geothermal power station as a geothermal power station can be designed so that Stirling engined generators are run along side a conventional Steam turbine,or could also used without the conventional Steam turbine altogether depending on the available heat from the ground.
These three positions are :-
1) Near the last set of boiler tubes before the exhaust gases are piped to the precipitator that removes the fine solid materials from the exhaust gases.
2) The steam tube before it enters the condenser used to condense the steam back into water before being feed back into the boiler tubes.
3) The third position that the engines could be placed after the condenser and before it is piped to the cooling towers that are used to cool the cooling waters before going back to the cooling pond.
The outputs from the Stirling engined generators can be used to supply electricity to the grid and also to run the CO2 to liquid hydrocarbons plant. Or could be used solely to help power the station itself and the CO2 to liquid hydrocarbons plant.
The generators to supply the grid or the station itself can be placed so they receive the hottest gasses. While the generators supplying the CO2 conversion plant are situated in the cooler regions of the heat supply and supply DC voltages to the CO2 conversion plant as it requires DC electrical power for the electrolysis process which is part of the CO2 conversion to liquid hydrocarbons. It is more efficient to generate DC straight off than to generate AC then converting to DC.
Returning to the Stirling engines. One of the principles that they operate on is the difference in temperature between the hot and cold cylinders. So it may be possible to run cooling water over the cold cylinder. It may allow extra energy to be extracted from the gases and water that otherwise would be wasted! I am not sure of the specifics on that score!
As the flue gases cool the size of the Stirling engines can be decreased proportionally to extract as much of the energy that was produced in the burning of the coal Even if it is to extract 1Watt electrical power from the flue gases. Just as you can fill a dam with a small drop of water at a time. So you can with electrical power it just depends on how you connect the generators and the output wave form from them. DC generators can be connected in series to increase the output voltage in the circuit or you can connect them in parallel to increase the output current.
By redesigning the exit of the flue gases after the initial heating stage of the water, the preheating of the incoming cold air and the preheating incoming water from the condenser plus treated water it may possible to extract 80% of the energy released from the burning of the coal. Though I may venture to say that with a real radical redesign of those areas it may be possible to extract 90% of the energy released by the coal, that would be the maximum amount of energy that is possible to extract as with any system there are unrecoverable energy losses.
This is the pilot petrol producing set-up:
The AFS plant comprises a CO2 capture unit in one shipping container, with a methanol reactor and miniature gasoline refining system in another. Air is blown into a sodium hydroxide mist, snagging CO2 as sodium carbonate. A condenser collects water from the same air. To make methanol – formula CH3OH – hydrogen is generated by electrolysing the water while the carbon and oxygen come from electrolysing the sodium carbonate. The methanol is then converted to gasoline.
The petrol producing plant though up-scaled would work in the same way. Though it would not be air that is blown into the sodium hydroxide mist but the cooled exhaust from the boiler unit of the thermal power generation plant.
The petrol could be sold to power vehicles such as trucks, buses, etc!
Or it could be used to drive Stirling engines to supply all the electrical energy for the thermal power generation plant. The exhaust gases from these can be feed back into the petrol production plant!
The energy supplied by the Stirling engines could also used to drive a large compressor to preheat the air and water! Just a thought!!
Wikipedia- Thermal power Station,
Stirling engines are going into space!
A team of researchers, including engineers from Los Alamos National Laboratory, has demonstrated a new concept for a reliable nuclear reactor that could be used on space flights.
The research team recently demonstrated the first use of a heat pipe to cool a small nuclear reactor and power a Stirling engine at the Nevada National Security Site's Device Assembly Facility near Las Vegas. The Demonstration Using Flattop Fissions (DUFF) experiment produced 24 watts of electricity. A team of engineers from Los Alamos, the NASA Glenn Research Center and National Security Technologies LLC (NSTec) conducted the experiment.
Read more at: http://phys.org/news/2012-11-scientists-power-space-video.html#jCp
Thanks Michel appreciated it helps me when I'm thinking electro-mechanical devices!
Considering a global implementation of Kyoto would only decrease global warming by less then half a degree in 2100, I expect more modest carbon cuts would do less. I would not judge this purely on carbon emission. The main issue with the stirling engine is it traditionally has low power output(be it may with with high efficiency). Coupling it with traditional steam as a power-lifter would be a great way to increase output per fuel input. As for having it operate alone, well if the folks of R&D had a Eureka moment(they tend to do that) I may have to reform my thinking. We tend to need high power output from plants built to burn fuel, as the infrastructure to break coal down and ensure the worst toxicities(which actually have resale value now) are not permitted to freely enter the biosphere require significant volumes to be cost effective. There is also direct heat transfers, in which you can directly transfer heat to electric current(it's cost effective for a secondary design). As for Michel's drawing, wouldn't the heat exchanger take all the heat transfered. All that is is something to allow ease of energy transport. What is the Stirling machine powered by. Flue gas, steam geneated, if the latter then it may be more cost effective to use a traditional boiler. Also, regarding solar energy...... how do you suggest that is captured, getting energy to flow from a low to a high environment requires work, it is far more likely any system collecting heat via the sun would allow heat from an system powered by carbon burning escape. Same with waste heat, unfortunately. Unless you mean it is hooked to another smaller engine.
No you use the heat that normally goes into heating water by the condenser and the cooling tower that then goes into the cooling pond. Plus the exhaust gasses once they are past the boiler water preheater.
How a Stirling engine works-1 This is an animated explanation with a good written explanation.
Colorado State University report. They study nineteen companies working on Stirling engines!
Watch a model Stirling engine running on YouTube.
The Stirling engine doesnt provide lots of power, unless you build lots of them, and that would be very cost-ineffective. It's not enough to be energy-effective mind you.
They supply enough power to push submarines.
They are more or less silent, and for low power-applications turn most chemical energy put in into energy out. As space for storage and not making noise are very serious applications for military submarines.... maybe militaries find paying a little extra for strategic advantage a worthy goal.
Chris, the switch to digital thermometes also allow more accuracy and control.
When the additional losses of electrical transfer are included even more loss is encored and why electricity shouldn't be used to heat houses. According to the DOE as much as 1/2 of the energy consumed by houses is used for heating. Carbon sequestering should capture the spent CO2 but it isn't being done.
I sarcastic laugh when municipalities offer digital thermometers free to replace mercury thermometers - as though that's why all our waterways (and fish) are polluted with mercury.
Give a cost-benifit analysis to carbon sequestering. How big a difference would taking 10-50ppm of sequestering out of the atmosphere. It would help, probably, now consider the cost. If we can lower the cost of find away to use that carbon in greenhouses, all the power to you. If you want to store is somewhere underground you are getting prohibitvely expensive. It's not about lining pockets. A dollar spent here is a dollar not spent elsewhere. As for taking measures to reduce mercury in the environment, that is only one reason, and for reducing heavy metal toxicity it's a start. Usually heating oil and natural gas are used in home heating.