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,
How much does pollution cost?
I don't know, an excellant question. A significant value, as is the need for scrubbers and capturing bottom and chimney ash. Reducing sulfur in chimney, making coal in carbon monoxide pre-burning is all the rage for that. That ash is heavy in heavy metals. Making it both toxic and valuable. Is is sustainable, no, but it's little things on such matters that wins us time for R&D. The best we can do is win time for the next generation to have better tools. We can not solve the problem you want to solve, and in trying you leave majy just as serious problems we can solve untackled. We can work towards decreasing the heat-sink effect of cities, with current tech; we can tackle malaria or balance the budget. Rather then sinking it into something in which the outcome would be modest at best. It would be 250B USD a year in the EU(kyoto).
fuck I wrote three or four paragraphs above that didn't take.
Polluters should pay the cost to clean exhaust regardless of the cost rather than externalize the cost to everyone including individuals who don't use the product creating the pollution. That's an unfair and expensive subsidy. Eliminating that subsidy and putting the real cost where it belongs (with the producer and user of dirty power) would balance the field making renewal energy more cost competitive.
Individuals should have to pay for the pollution they create too. Automobiles for example could pay a tax based on their smog emissions at the pump when gasoline is purchased by entering the license number.
A selfish asshole who lives in my suburban neighborhood burns wood as his primary heat source. His savings by using wood rather than natural gas or passive solar are paid throughout the neighborhood with the gray smokey haze that hangs in the air causing asthma and other health problems for some. He should be taxed for that pollution - doing so would make cleaner sources more competitive. The above picture is outside Philadelphia Penn before they enacted a smoke ban. The link discusses air pollution controls over the years including; 1273 –First air pollution regulations. After “Carbone marino”replaced wood in kilns and heating increasing air pollution in London, King Edward I banned coal burning . Edward II (1307-1327) tortured some violators of the ban. Richard II (1377-1399) used tax policy to limit coal. I'm working on a backup computer (which is giving me fits) so I don't have a link to a full story and set of photographs showing Phili before and after the smoke ban. After the ban the black buildings were washed surprising people to find that the stone buildings were white.
They started burning coal gas in London, which I believed was replaced by heating oil and natural gas.
Here's info about a new development to convert exhaust heat into energy.
To save energy: take dirt, add heat
MICHIGAN STATE (US) — Researchers have developed a new thermoelectric material by using common minerals found pretty much anywhere there’s dirt. View
That’s important, because the vast majority of heat generated from, for example, a car engine, is lost through the tail pipe. It’s the thermoelectric material’s job to take that heat and turn it into something useful, like electricity.
The researchers, led by Donald Morelli, a professor of chemical engineering and materials science at Michigan State University, developed the material based on natural minerals known as tetrahedrites.
“What we’ve managed to do is synthesize some compounds that have the same composition as natural minerals,” says Morelli, who also directs Michigan State’s Center for Revolutionary Materials for Solid State Energy Conversion. “The mineral family that they mimic is one of the most abundant minerals of this type on Earth—tetrahedrites.
“By modifying its composition in a very small way, we produced highly efficient thermoelectric materials.”
The search to develop new thermoelectric materials has been ongoing. While some new, more efficient materials have been discovered as of late, many of those are not suitable for large-scale applications because they are derived from rare or sometimes toxic elements, or the synthesis procedures are complex and costly.
“Typically you’d mine minerals, purify them into individual elements, and then recombine those elements into new compounds that you anticipate will have good thermoelectric properties,” he says. “But that process costs a lot of money and takes a lot of time. Our method bypasses much of that.”
As reported in the online journal Advanced Energy Materials, the new method involves the use of very common materials, grinding them to a powder, then using pressure and heat to compress into useable sizes. “It saves tremendously in terms of processing costs,” Morelli says.
Cheap Ceramic thermocouples to garner electrical power from the heat of the exhaust. Good idea and depending on their output amperage could mean that they could supply the power all the additional devices that people think that they need!
small improvements to the rankine system are always worth discussing, but to discuss a full scale revolution in power generation from the rankine cycle is a massive endeavor. As for additional devices people think they need, does it increase my productivity and make my life enjoyable. Why dont they need it, what is wrong about having additional devices.
When I wrote this discussion I overlooked an article on converting waste heat in to electricity using a doped up relative of Lead Telluride.
Scientists in the United States have developed a material that beats the record for converting waste heat into power - something they hope will be incorporated into clean energy investment.
Described by an independent commentator as "a giant leap", the material achieves the highest efficiency ever for scavenging heat from a source and transforming it into power, its inventors say.
According to the team, as much as 15 to 20 per cent of the heat that disappears out of car tailpipes and the chimneys of power stations and factories could be recovered as electricity.
This material could be used down stream of the Stirling engines to extract the remnants of the heat energy so that both the air and water return to the natural ambient temperatures of the two fluids.