List of contents
1. Power on Mars
2. Fire on ice?
3. Background of the concept
3.1. Thermodynamic principles of a steam turbine
3.2. Working of a Surface Condenser
4. The Martian energy conundrum
5. Water on Mars
6. The Mareekh Process; A method of Hybrid Power Generation for Mars
7. The Thermodynamics of Mareekh Process and the energy equation
7.1. The Feeder Systems
7.2. Thermodynamic calculations for the LPFS and HPFS
7.3. The Inlet Steam
7.4. Gross Power Output
7.5. Net Power Output
8. Mareekh Process and the apparent energy paradox
8.1. Does Mareekh Process follow the Rankine Cycle?
9. Conclusion
1. Power on Mars
One of the basic requirements for a long term or permanent human habitation on Mars is the ability to generate power. From running of equipment to construction and manufacture, mining, transportation, to even maintenance of liveable internal environment of human habitats on Mars will require power. In contrast to Earth, Mars lacks any substantial sources of energy. The only known natural source of harnessable energy on Mars is the sunlight, and yet, it is significantly less as compared to that on Earth.
Early human missions to Mars will need to carry photovoltaic arrays from Earth to harness the solar power. Solar arrays are light, thin and foldable, and have a good efficiency and durability, and the ease of maintenance. On Mars, the solar flux is 590w/m2 which is merely 43% of 1373w/m2 on Earth. While due to the thin atmosphere on Mars making solar flux relatively more efficient than on Earth, every once in a while, say nearly every couple of Earth years or so, the Sunlight on Mars can get completely blocked out by the global dust storms which may last many months at a time, leaving any prospective human settlers on Mars resort to the backup power. These back up power sources can be Radioisotope Thermoelectric Generators (RTGs) which have been powering space probes such as Voyager 1 and 2, Cassini, New Horizons, or the Martian robotic rovers such as Curiosity and Perseverance. Though very durable and long lasting, the power they provide is little, merely a few hundred watts. For the sustenance of a sizable human colony, even RTGs will be insufficient. The next option are the boiling water nuclear reactors. The miniature category of such nuclear reactors, such as the small modular reactors are too costly, and the logistics of transporting these from Earth to Mars is rife with huge costs and risks. Supply of nuclear fuel from Earth is itself a logistical nightmare, rendering this option less viable.
Other than the Sunlight, Mars lacks nearly all other energy resources that could be utilized for human use. This includes absence of any harnessable wind power owing to an extremely thin atmosphere, no known geothermal sources due to lack of any tectonic or volcanic activity, no tidal power due to the lack of any water bodies on the surface, no fossil fuel reserves, and no known reserves of radioactive minerals.
Solar arrays or RTGs can provide limited power for small human habitats on a very small scale. But most of the power usage for sustenance of a human colony will be in manufacture, mining, smelting and construction. Solar or limited nuclear energy such as RTGs are simply insufficient to serve the purpose.
Solar panel of the InSight Lander covered in dust.
Fine Martian dust poses unique challenges for the reliability of solar power due to the need for maintenance and frequent cleaning of solar panels. Prolonged dust storms completely blocking all sunlight is also a major challenge on Mars.
(Picture source: https://abcnews.go.com/Technology/mars-lander-losing-power-dust-solar-panels/story?id=84805112)
NASA's Kilopower concept.
These are small scale nuclear reactors providing 1-10kw of power. Though long lasting and would work regardless of the light conditions, these small nuclear reactors can barely supply enough power to run small habitation modules, and may be insufficient to power a large scale human habitation on Mars.
(Picture source: https://www.nasa.gov/directorates/spacetech/feature/Powering_Up_NASA_Human_Reach_for_the_Red_Planet)
2. Fire on ice?
Underneath its immediate surface, Mars has huge reserves of water ice known as permafrost and subsurface glaciers, in addition to the polar ice caps, from polar to subtropical or temperate latitudes, and can be several kilometers thick in places. Using the right combination of temperature and pressures from an auxiliary source of power, the ice can be turned into hot water and steam, and can be used to run steam turbines to generate vast amounts of electricity.
Hydrogen Map of Mars, showing the distribution of permafrost underneath the Martian surface. Mars locks huge swathes of permafrost several kilometers thick. This could provide a valuable reserve of precious water for a prospective human colony on Mars.
(Picture source: https://airandspace.si.edu/multimedia-gallery/6050hjpg)
Mars has an extremely thin atmosphere with an average pressure of 0.6% of that on Earth. This unique attribute of the Martian atmosphere may play a pivotal role in power generation on Mars.
Imagine suddenly exposing hot water, say, at 90 degrees Celsius on Earth. This temperature is lower than the boiling point of water on Earth at sea level which is 100 degrees Celsius. Nothing will happen and the hot water will continue to simply evaporate in the form of water vapour.
On Martian surface, the triple point of water does not exist as the atmospheric pressure is too low to sustain water in a liquid form. The ice exposed to the surface at the Martian atmospheric conditions will simply sublimate to form small quantities of water vapour.
Imagine exposing the earlier mentioned hot water at 90 degrees Celsius to the Martian atmospheric pressure, it will be an altogether different story. 90 degrees Celsius temperature is much higher than the boiling point of water at the Martian atmospheric pressure. The water at 90 degrees Celsius will simply explode into flash steam in a vapour or steam explosion. Water generated from melting of ice in permafrost using heat from an external energy source can be harnessed into running steam turbines on Mars to generate electricity.
At Mareekh Dynamics, we have conceived and designed a method of utilizing the permafrost ice converted into hot water using a source of energy to generate a large amount of power in an extremely efficient manner. We have named it the “Mareekh Process”.
3. Background of the concept
The utilization of steam from hot water extracted from permafrost to run steam turbines in the Mareekh Process is analogous to the working of a steam turbine for electricity generation on Earth, with some key modifications suited for Mars, taking advantage of the unique attributes of the Martian environment.
3.1. Thermodynamic principles of a steam turbine
Steam turbine utilizes the expansion of superheated steam at high pressure, using the flow of the expanding steam to run turbine blades attached to the generator for electricity production. The steam is produced by boiling the water using fossil fuel such as coal in a conventional power plant or a radioactive source in case of a nuclear power plant.
During the process of boiling the water, in addition to increasing the internal heat of the water, latent heat of vapourization is also required to convert the water into steam. So the steam thus generated is carrying the internal heat as well as the latent heat of vaporization which is 2257kJ/kg. This, added with a very high pressure, increases the enthalpy (E = H+PV; where E is the enthalpy, H is the internal energy, and PV is the product of the pressure and volume.).
The superheated steam is released inside a turbine housing where it is allowed to expand. The turbine housing inlet is narrower and at a smaller volume to accommodate high inlet steam pressure. The hot and pressurized steam expands and flows towards the low pressure turbine housing which is usually built in a continuum with the high pressure turbine housing and has a progressively larger volume to accommodate the expanding steam. The sizes of the blades in the turbine increase from high pressure turbine housing to low pressure turbine housing. The flow of the expanding steam causes the turbine blades to rotate on a shaft which is connected to a generator to produce electricity. As the steam moves through the rotating turbine blades, it continues to give up its energy which is transferred to the turbine blades as mechanical energy.
On Earth, the minimum pressure naturally achievable in the low pressure turbine housing is nearly 1 bar i.e. Earth’s atmospheric pressure. At this pressure, the final achievable temperature of the steam inside the low pressure turbine housing will be between 100 to 120 degrees C. This is a lot of steam energy that hasn’t been utilized to run the turbine. In order to increase the efficiency of the expanding steam, the pressure at the end of the turbine housing should be much lower than the atmospheric pressure. Creation of a very low pressure in the low pressure turbine housing is achieved through a device known as the Surface Condenser. This process of achieving low pressure at the low pressure housing is an active process utilising cool water running through several tubes. To facilitate maximum expansion of the superheated steam inside the turbine housing, the pressure inside the low pressure housing is maintained below the outside atmospheric pressure of 1 bar. This is to ensure that the expanding steam settles at a much lower energy state and condenses into water, leaving a partial vacuum behind, which in most power plants, is around 0.1 bar. This low pressure has three main advantages: Lower energy/enthalpy state of the final steam, conversion of the steam to condensate water which is re-routed to the boiler, and the creation of a partial vacuum to facilitate rapid and effective expansion of the steam.
3.2. Working of a Surface Condenser
Surface condenser is a core concept in understanding the thermodynamics of the Mareekh Process. The surface condenser is an enclosed chamber with a network of tubes running parallel to each other and connected to an outside water source. The main chamber of the surface condenser is in direct connection with the turbine housing which is otherwise completely sealed from the exterior. This water is sourced from local water bodies such as rivers. The steam in the last part of the turbine housing being very close to its condensation temperature and pressure, as it comes in contact with the tubes of the surface condenser, it rapidly cools and condenses into water leaving behind a partial vacuum. While condensing, the steam transfers its latent heat of vaporization to the water in the tubes causing it to warm up as it circulates through the tubes in the condenser and is channelled outside to a heat sink (for example a cooling tower). As the water in the tubes is pumped constantly in huge quantities, the heated water is quickly replaced by the inflowing cold water and the cycle of condensation continues. In order for the maintenance of very low pressure inside the low pressure turbine housing, the end steam needs to be continuously condensed into water inside the surface condenser which needs to maintain the flow of large quantities of cold water to absorb the heat of the steam and reject it outside. The water obtained from the condensing steam is then recirculated back to the boiler via a feedwater pump.
The surface condenser consumes a considerable amount of energy; firstly to run the pump motor to channel huge quantities of water through hundreds of narrow tubes for heat exchange, which can go to tens or even hundreds of kilowatts derived from the generator itself. Secondly, the surface condenser needs to absorb large quantities of heat in the form of heating of the flowing water and transfer this heat out in order to achieve low pressures in the turbine housing to ensure continuous working of turbine in an efficient manner. As per the calculations, nearly 60 percent of heat content of the steam is exchanged and rejected to the outside of the system in this manner, leaving roughly 40% for power generation by the generator attached to the turbine.
In the absence of a surface condenser, the minimum pressure achievable in the low pressure turbine housing will be 1 bar or above. The steam will end up at its saturation temperature of nearly 100 degrees C at that pressure, meaning it won't condense into water and will still carry a lot of enthalpy and unused energy.
The surface condenser requires a lot of power from the generator itself to circulate an enormous amount of water through its hundreds of narrow tubes. It also needs to transfer a lot of heat energy to the exterior in order to achieve the condensation of the steam in the low pressure turbine housing by creating the desired partial vacuum or low pressure.
4. The Martian energy conundrum
Mars is a seemingly dead world. Not only from the perspective of lacking any evidence of life but also near total absence of any energy sources that can be utilized by any prospective humans settlement on the planet, except for the limited solar flux. Mars hasn’t always been like that. It was a geologically living world and perhaps biologically alive at some stage of its life billions of years ago where rivers flowed, winds blew, and volcanoes brought the heat energy from its deep mantle to the surface. These are all relics of its ancient past now. With an absence of wind power, tidal energy, geothermal sources, radioactive reserves, or fossil fuel, setting up a permanent human colony with an average energy requirement many times more than that of the inhabitants of Earth, is a major challenge and requires a radical shift in our way of thinking of ways generating power massive enough to sustain a long-term human presence there. This may even require bold ideas defying common sense. Mars literally requires an “alien technology” for the aliens to survive on the red planet.
5. Water on Mars
Formed in the protoplanetary disc in the habitable zone alongside Earth, Mars had a similar beginning as Earth with adequate atmospheric pressure and temperature enabling liquid water to exist on the surface in huge water bodies. Formed in the outer fringes of the inner solar system, much of the matter in the Martian orbit was soaked up by Jupiter during its formation, leaving a much smaller Mars. Lower mass and gravity led to the cooling down of its interior much quicker than Earth, thereby losing the magma convection and subsequently losing its protective magnetic shield. With no protection against solar wind, the water in the Martian atmosphere disintegrated into hydrogen and oxygen atoms; the former being lighter was simply blown away into deep space and the later being consumed by the surface iron to oxidize into iron-oxide giving the characteristic red hue to the Martian surface. As the bombardment of the UV radiation and solar winds continued, Mars rapidly lost its atmosphere leaving behind a thin atmosphere of heavier CO2. As the Martian atmospheric pressure plummeted, so did the temperature. The surface water percolated underground and got locked away as permafrost, while the remaining water cycled through the seasonal variations to deposit over the polar ice caps and got locked there. At present times, there are no known liquid bodies of water on or near the Martian surface.
The Martian permafrost covers nearly the entire planet, buried very close to the surface and is several kilometers thick; roughly 3.5km near equator and over 8km thick at higher latitudes and near the poles.
Permafrost is perhaps the most important and easily extractable natural resource on Mars for any prospective Martian human colony. It can be used for human consumption, growing crops, manufacture of concrete and other industrial products, ore processing, and in the synthesis of rocket fuel, provided there is availability of surplus energy in addition to what is needed for the basic sustenance of a human colony.
Does the Martian permafrost hold more promise than just being a substrate for chemical, industrial and biological processes? What would be the implications of attempting to run steam turbines from the water extracted from the permafrost using auxiliary solar or nuclear power in the unique attributes of the Martian surface and atmospheric environment?
The Mareekh Dynamics team has explored the possibility of using hot water extracted from permafrost by transferring heat to it, and exposing this extracted hot water to the very low Martian atmospheric pressure to achieve explosive production of steam and using its rapid expansion to run the steam turbine at the surface for power generation.
6. The Mareekh ProcessⓇ; A method of Hybrid Power Generation for Mars
Mareekh ProcessⓇ is our patented method of extraction of water from permafrost, heating it and releasing it into the turbine housing to run a generator to produce electricity.
We will explore the mechanisms and thermodynamics involved in the whole process and debate the implications of this concept.
The Mareekh ProcessⓇ is based upon the same principle as a steam turbine on Earth. We have introduced two key modifications to enable it to function in the unique Martian environment.
The most fundamental difference between Mareekh ProcessⓇ and the Earth based steam turbines is the lack of the need of a surface condenser on Mars. Mareekh ProcessⓇ is also designed to avoid converting water into steam in any of its energy consuming steps which will be explained below.
Surface condensers consume enormous amounts of energy, sometimes as much as 60% of the input energy from the fuel.
As discussed above, the surface condenser is needed to create a near-vacuum inside the turbine housing to ensure continuous working of the turbine. On Mars, due to very low atmospheric pressure, a surface condenser will not be needed for a steam turbine working on the surface of Mars.
Not needing a surface condenser, and using Martian atmosphere as surface condenser analogue or a heat sink has huge implications and will translate into a much greater net gain in the power output.
In Mareekh ProcessⓇ we have ruled out any conversion of water into steam inside the process itself and only utilizing low atmospheric pressure on Martian surface to generate the flash steam from hot water, thereby saving the energy spent in converting water into steam which is 2257 kJ per kilogram of water. This will also translate into a net gain in the output power.
We will now discuss every step of the Mareekh ProcessⓇ and the thermodynamics calculations to derive the energy input and output per unit mass of water extracted.
The boiling point of water at Earth’s atmospheric pressure at sea level of 1 bar is 100 degrees Celsius. The water boils at lower temperatures at higher altitudes as the air pressure drops. Water at room temperature if exposed to a total or near total vacuum spontaneously boils to turn into steam even in an absence of a heat source. This process of spontaneous boiling halts as the steam vapour fills the vacuum chamber and increases the chamber pressure raising the boiling point of water above the room temperature. If the water is exposed to the vacuum of space, the spontaneous boiling should continue 'indefinitely' until all the water is boiled off to steam. However this doesn’t happen.
Converting water into steam is an endothermic process, which means it needs energy. One litre of water will require 2257 kJ of energy to completely convert into steam. This energy must come from somewhere. And it comes from the boiling water itself. While the water is spontaneously boiling in vacuum, it continues to cool the residual water as it draws heat from itself to create the steam. At one point, the temperature of the residual water will reach its freezing point (nearly 0 degrees), when it freezes over and stops boiling. This spontaneous boiling will also occur in environments with pressures at near-vacuum such as the surface of Mars.
The fraction of water that spontaneously boils depends upon the initial temperature of the water exposed to the vacuum or near-vacuum, and the pressure it is exposed to. However, the process of spontaneous boiling of water at room temperature in vacuum is slow. Also the steam that is generated is saturated and is in a vapour form, which readily condenses back into water as it hits any surface and lose any fraction of the kinetic energy of its molecules. The hotter the water exposed to the vacuum, the quicker it boils off. Above a certain temperature limit, the water gets so hot that it flash boils into a steam explosion obliterating a significant fraction of it into steam and cools down the remaining fraction as a residual water at near saturation temperature. The flash steam produced as a result of flash boiling of water is at its saturation temperature. It does not carry the required 'kick' to run the turbine since if it expands any further, its temperature will drop and it will start condensing. The fraction of water flash boiling into steam depends upon its temperature and the pressure it is exposed to; the higher the temperature and the lower the pressure, the greater the fraction of water that flashes into saturated steam.
Mareekh ProcessⓇ describes the working of a steam turbine on Mars in a novel way, specifically designed to work in the very low atmospheric pressure environments such as Mars, or other planetary bodies like the icy moons of Jupiter and Saturn such as Europa, Ganymede, Callisto, Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus. Titan is excluded from the list due to its thick atmosphere and high atmospheric pressure.
On Mars, the steam is sourced from the permafrost or subsurface glacier. The permafrost is liquified by transferring heat deep below the surface using an injection well. Any medium can be used for this purpose that can be heated sufficiently and does not react with water, subsurface rocks, or the lining of the injection and recovery well or other equipment and parts. Hot air or water can be used as a heat transfer medium, however the surface of Mars lacks both of these substances. A heated coil can also be used. In Mareekh ProcessⓇ, we prefer the use of CO2 as the heat transfer medium. The CO2 is readily available on Mars as the thin Martian atmosphere is nearly completely composed of CO2 which settles as dry ice frost in chilly Martian nights especially at higher latitudes. In order to use it as a heat transfer medium, it has to be liquefied under high pressure to reduce its volume and increase its density. This can be done using high pressure tanks and pumps on the surface, powered by the auxiliary solar or nuclear power (RTG). The compressed and liquified CO2 is then channelled inside the tubes through an enclosed filament heater powered by the auxiliary power source. The isochoric heating of the liquid CO2 turns it into superheated-supercritical CO2 making it a perfect heat transfer medium. The Sh-Sc CO2 (around 700 degrees C and at 100bar) is now injected deep underground into an injection well. The Sh-Sc CO2 is then released into the ice or permafrost deposit the temperature of which may be around -70C. This hot medium melts the permafrost and creates a liquid water reservoir. As the water reservoir increases in size by the continuous injection of the Sh-Sc CO2, the larger size gravels in the permafrost settle at the bottom due to gravity. Using CO2 has an added advantage of purifying the water reservoir of the fine suspended particles. The depth to which the injection well reaches must be carefully chosen to maintain a sufficient pressure inside the reservoir. The pressure at 100m depth under Martian surface is nearly 30bar which is a sufficient pressure to maintain the integrity of the water reservoir and use it as a high pressure medium to facilitate the extraction of water through the recovery well.
The Sc-Sh CO2 injected under a high pressure runs a bidirectional turbine that also helps to pump the water up into the recovery well which is then collected inside a recovery buffer tank under a pressure that is significantly lower than the underground reservoir pressure (to facilitate the extraction) but higher than the Martian environmental pressure, for example 1 bar, to keep the stored water in liquid form. The recovered water may be tainted with suspended particles and dirt. The buffer tank is connected to a slurry removal system at the bottom. A fraction of the dirt is settled at the bottom of the recovery buffer tank which is removed by the powered slurry removal system. Other means for active removal of suspended particles (mechanical or chemical) can be employed to clear the water of contamination. The dissolved CO2 in the recovered water will degas and can be recovered from the recovery buffer tank and recirculated to the liquid CO2 tank located at the start of the process.
The water now needs to be heated to later expose it to the low atmospheric pressure which will convert a fraction of the hot water into flash steam. For this purpose, the water from the buffer tank is now channelled into a system of tubes inside the auxiliary powered enclosed heater in an isochoric process. Maintaining the volume (in the isochoric process) means achieving high pressure inside the tubings which will heat up the water to very high temperatures without it turning to steam. Though this system can achieve very high pressures such as 10-50 bar or higher, this is still called Low Pressure Feeder System (LPFS) as explained subsequently. This superheated water under high pressure is now discharged into a flash tank at a much lower pressure (though significantly higher than the end-atmospheric pressure of 0.006 bar).
The inlet temperature and pressure of the superheated water from LPFS and the flash tank pressure is so adjusted that nearly a quarter of the water is immediately flashed into saturated steam. This flash steam is now channelled to a common injector for the steam turbine. The residual hot water is recovered to be reheated again in the LPFS. As the flash steam is saturated in nature, it tends to turn into vapours quickly as it expands and cools. This makes it impractical to use it to run the turbines through expansion and cooling. The flash steam needs to be reheated. One of the ways to reheat the flash steam is to rechannel it to the enclosed heater to turn it into superheated steam. This superheated steam can then be released into the turbine housing where it can explosively expand and run the turbine in a similar manner to a conventional steam turbine. This approach has the advantage of being the straightforward way of heating the saturated steam. However there is another way of heating up the saturated steam, that is, mixing it with a small amount of supercritical water from a High Pressure Feeder System or HPFS (explained later) before injecting it into the turbine. The advantage of this approach is the increased mass of the superheated steam being injected into the turbine housing as the supercritical water mixes with the saturated steam inside the common injector to form a hot superheated mixture. This superheated mixture of supercritical water and superheated steam is injected into the turbine housing. This mixture, now in the form of completely superheated steam, explosively expands inside the turbine housing. The rapidly expanding steam will flow towards the low pressure turbine housing transferring its heat energy into the mechanical energy being produced.
For extracting the energy from superheated steam and converting it into mechanical energy of the turbine, the superheated steam needs to rapidly expand in a relatively low pressure environment as compared to the pressures inside the injecting system (HPFS and LPFS). In order to create a steady flow of the expanding steam along the length of the turbine housing, a very low pressure is maintained at the end of the turbine housing opposite to the injection system at high pressure turbine housing. To facilitate this expansion, the turbine housing is usually designed to have a gradually increasing diameter giving the turbine housing a conical shape. There are a series of turbines from high pressure turbine housing to the low pressure turbine housing. The turbine shaft is connected to a power generator.
The energy input to the steam in conventional steam turbines on Earth using fossil fuel or nuclear includes providing internal heat to heat up the water and the latent heat of vaporization to convert water into steam and further heating of steam to superheated steam before injecting it into the turbine housing for expansion and running the turbine. The energy required to heat the water to reach the boiling point is a function of specific heat of water which is 4.19kJ/kg.K at room temperature. The value of specific heat drops for hotter water. The latent heat of vaporization, the energy required to convert water into steam is 2257kJ/kg at 1 bar pressure which is a significant amount of energy. The value is slightly lower at higher pressures and temperatures too. The steam thus produced is further heated to higher temperatures to convert it into superheated steam which is a function of the specific heat of steam which is nearly 2kJ/kg.K. Latent heat of vaporization comprises a significant fraction of the input energy from the fuel to the steam.
On Earth, there are plenty of fuel resources including fossil or nuclear fuel as compared to Mars. If a steam turbine on Mars needs to be run on the same principle as Earth, it will require a lot of power from auxiliary sources such as solar or limited nuclear to heat up the water extracted from the permafrost to generate electricity. The net input of energy will exceed the power output as most of the energy will be utilized in the provision of latent heat of vapourization, and in the heat rejection and power consumption from the working of a surface condenser.
The unique attributes of the Martian environment including very low atmospheric pressure and low surface temperature hold many promises to improve the efficiency of a steam turbine running on the water extracted from the subsurface permafrost.
The main difference between the working of a steam turbine on Earth and the working of a steam turbine on Mars through the Mareekh ProcessⓇ is the lack of need for a surface condenser on Mars. The low atmospheric pressure on Mars ensures that the entire heat energy is transferred into mechanical energy of running of the turbine as the temperature of the end-steam in the low pressure turbine housing is down to near freezing point of water at 0.006 bar pressure. However, pressure slightly above the atmospheric pressure needs to be maintained to prevent the freezing of the steam into ice and condensing inside the turbine housing. This is achieved through the use of a pressure control valve which will allow small quantities of steam to escape to the exterior into the Martian atmosphere where it will convert into an ice cloud. In this way, a pressure of 0.01 to 0.02 bar pressure can be maintained in the low pressure turbine housing. At these pressures, the boiling point of water is between 7C to 17C. The steam would have lost so much of its energy already that when it hits the spinning blades of the last part of the turbine, it will condense into water droplets giving up the latent heat of vapourization as kinetic energy that will get transferred as mechanical energy to the turbine blades and the condensate will settle down as water. The pressure of 0.01 - 0.02 bar will ensure that the condensate won’t spontaneously flash-boil and freeze. The pressure can be automatically adjusted by controlling the amount of escaping steam via the pressure control valve. The condensate water can then be recovered for use or channelled back to the feeder systems to be heated again for reuse.
Another key feature of the Mareekh ProcessⓇ is the avoidance of converting water into steam at any point inside the apparatus that would require energy, thus saving significant amounts of energy that would otherwise be spent in converting water into steam as latent heat of vaporization. Rather, Mareekh ProcessⓇ utilizes the low atmospheric pressure to flash boil the hot water from the feeder system into a flash tank. The flash tank maintains a pressure higher than the Martian atmospheric pressure but still low enough to spontaneously flash boil water into saturated steam. Mareekh ProcessⓇ also utilizes the use of supercritical water by heating the water in HPFS through an isochoric process, attaining supercritical pressures and temperatures to produce supercritical water. Creating supercritical water bypasses the need to given latent heat of vapourization as no steam formation happens inside the apparatus.
The saturated steam from LPFS and supercritical water from HPFS are then combined into a common injector. The common injector is composed of the nozzle from the HPFS carrying supercritical water telescoping into the much wider nozzle from the LPFS carrying the saturated flash steam from the flash tank. The common injector serves two purposes; 1. To create a negative pressure in the nozzle of the LPFS through Venturi effect of the rapid flow of supercritical water under very high pressure through the narrow HPFS nozzle into the common injector. This negative pressure helps draw the flash steam from the flash tank towards the turbine housing. 2. Heating of the saturated flash steam from the LPFS by energy transfer while mixing, creating a superheated dry steam being injected into the turbine housing.
The superheated mixture of saturated steam from LPFS and supercritical water from HPFS has a temperature far above the boiling point of water at the pressure in the high pressure turbine housing (0.5 - 2 bar). The mixture is injected into the turbine housing from the combined injector, where it explosively expands into superheated steam (mixture at temperature well above the saturation temperature at the inlet pressure). The expanding steam now flows through the turbine housing, imparting mechanical energy to the turbine blades while it loses its temperature and enthalpy, until it reaches the end part of the turbine housing losing enthalpy enough to condense into water to percolate and recirculate.
The lack of need of a surface condenser on Mars, and utilizing the low Martian atmospheric pressure to create flash steam rather than imparting the heat of vaporization will save a lot of input energy which is vital for the success of a long term colony on Mars, since the energy resources on Mars are extremely limited.
7. The Thermodynamics of Mareekh Process and the energy equation
The permafrost under Martian surface is buried underground under high pressures due to gravity and very low temperatures, close to -70 C. The pressure under the Martian surface increases roughly 1 bar per 10 meters. At nearly 100m, it sits around 30bar.
The first step will be the melting of the permafrost or subsurface glaciers by injecting heat into the permafrost from the surface. Any medium, such as superheated water, air, or CO2 can be used. Other means such as a hot filament or a radioactive tip can be used. Water carries the advantage of greatest specific heat and ability to carry the heat. But water is a precious resource on Mars and sourcing pure water and using it for this purpose is costly. Air can also be used but it has a lot of volume and very little specific heat and heat carrying capacity. The hot filament imparts energy to a very small volume and carries the risk of underground steam formation consuming a lot of energy in the process. Using a radioactive tipped drill carries the risk of radiation contamination and may make water unsuitable for human usage. CO2 is useful for several reasons. Firstly there is plenty of it on Mars in the form of deposits on or near polar ice caps in the form of dry ice. At lower latitudes, atmospheric CO2 freezes out and condenses over the surface as dry ice frost at night and early hours of morning before sunrise and sublimates as the sun comes out. The second advantage of using CO2 is that it can be liquified at Martian surface temperatures inside pressurized tanks. The third advantage is that it wouldn’t react to the equipment and tubes through which it is channelled. The other advantages include its ability to desalinate the briny permafrost or subsurface water, its ability to help settle the dissolved impurities, and easy degassing out of the water when it reaches the recovery buffer tank.
In the first step, the CO2 is stored in the CO2 reservoir tank at an ambient surface temperature of -30 to -50 C with tank pressure at nearly 5 bar. This ensures the CO2 is in liquid form. This CO2 is then channelled in tubes through the enclosed heater power by the auxiliary solar or nuclear units on the surface. CO2 will reach the critical point at 73 bar pressure and 31 degrees C. In order to transfer heat down to the underground reservoir, the CO2 needs to be at much higher temperature and pressure, roughly above 100 bar and above 700C. This superheated-supercritical CO2 is now injected underground through pumps and released into the ice reservoir (permafrost or subsurface glacier). The CO2 will release its heat as it comes in contact with ice and liquify it into water, dissolving into it in the process.
The objective of the heat transfer from the surface into the underground ice reservoir is to melt it to a temperature where it can be hot enough to stay liquid and not freeze during the process of recovery, but also not too hot to release too much heat in the surroundings during the recovery process. The underground reservoir needs to be maintained at a temperature that it does not freeze over or expands to unnecessarily huge size. These temperature parameters can be worked out at the time of the application of the Mareekh Process as they are dependent upon many factors including the external and underground temperature, depth of the reservoir, and the composition and nature of the permafrost or subsurface glacier, and the amount of impurities and the salt content. A rough estimate here would be to extract the water at 30 degrees C and maintain the reservoir at that temperature.
Isochoric heat capacity of CO2 is 0.65kJ/kg.K. The amount of heat that needs to be transferred to the subsurface reservoir of ice to convert into water of desired temperature depends upon how much water needs to be recovered to the surface to replenish the water that is lost to the atmosphere through the pressure control valve in order to maintain the desired pressure in the low pressure turbine housing. Our thermodynamic calculations are based around 1.5kg of superheated steam injected into the steam turbine as a reference unit of measurement. The input and output energies of the system can then be calculated from the figures obtained from the input and output for the system working on 1.5 kg of injected steam per second. Our assumption is that 0.1kg of steam will be lost to the outside environment per second for every 1.5kg steam being injected into the turbine. Since rest of the 1.4kg steam will condense into water at the end of the process which will be recirculated back for heating, only 0.1kg of water needs to be added to the circulating water from the recovery buffer tank, which is in turn recovered from the subsurface water reservoir formed by melting of the ice using Sh-Sc CO2. The amount of Sh-Sc CO2 required to heat up the ice at -70C all the way to 30C can be calculated by the required amount of heat for converting ice to water over this temperature range using the formula:
Q=mcΔT
Where
Q = heat required
m = mass of water needed to be recovered from ice. Here it is 0.1kg
c = specific heat of substance (ice/water)
ΔT = Change in temperature
The change of ice from -70C to water at 30C happens in three main steps
Increasing the temperature of ice from -70C to 0C
Melting of ice
Heating of water from 0C to 30C
Q(Recovery) = mc1ΔT1 + mc2ΔT2 + heat of fusion of ice to water (334kJ/kg)
= (0.1 x 1.8 x 70) + (0.1 x 4.2 x 30) + (334x0.1)
= 12.6 + 12.6 + 33.4
= ~ 60kJ
An equivalent of 60kJ/s of energy needs to be injected into the ice deposit for continuous running of the Mareekh Process.
The amount of CO2 at 700C and 100 bar pressure can be calculated as follows.
Q=mcΔT
m=Q/cΔT
The isochoric specific heat capacity of liquid CO2 is 0.658 kJ/kg.k
To carry 60kJ of heat at 700C, the amount of Sh-Sc CO2 must be
m=Q/cΔT
= 60 / 0.658 x (-50C →700C)
= 60 / 0.658 x 750
= 0.12kg or 120g per second
The initial amount of Sh-Sc CO2 needs to be considerably large in order to melt the initial permafrost and create a water reservoir at 30C. Once a reservoir is formed, much less amount of CO2 will be required to maintain the reservoir. The amount of CO2 of 120g per second is more of an average for the entire process.
The Sh-Sc CO2 at high temperature and pressure runs a bidirectional turbine at the bottom of the injection well which is enlocated in a concentric recovery well to move and recover water to the recovery buffer tank at surface. This recovery buffer tank is an enclosed unit with no connection to the outside world except a degassing unit to degass the dissolved CO2 and a slurry removal unit. The tank in the recovery buffer tank is maintained at 1 bar; low enough to facilitate the recovery of water from the reservoir hundreds of meters deep, but high enough to keep the water in stable liquid form at 30C. The bidirectional turbine, powered by the injected Sh-Sc CO2, has opposite blades at the inlet of the recovery well that propels water up into the recovery well further facilitated by the 1 bar pressure in the recovery buffer tank.
The water from the recovery buffer tank only helps to replenish the amount of water lost to the exterior as ice-vapour which in our calculation is 0.1kg per second. Rest of the water circulating in the system is the condensate from the end of the turbine housing.
7.1. The Feeder Systems
There are two feeder systems responsible for injecting the superheated steam into the turbine housing; the Low Pressure Feeder System (LPFS) and the High Pressure Feeder System (HPFS). These feeder systems constitute the core of the Mareekh Process.
The LPFS is responsible for circulating water through the enclosed heater inside tubes to achieve a temperature and pressure of 235C and 30bar. The purpose of these parameters is to ensure that the water is hot enough so a significant fraction of it flashes into steam when injected into the low pressure flash tank, yet the pressure in the tubes of the LPFS is high enough to prevent it from turning into steam inside the tubes before its injection into the flash tank. The water being circulated in the tubes of the LPFS is extracted from the recovery buffer tank at the beginning of the process and later the hot condensate from the flash tank and the cold condensate from turbine housing during the sustained process. Nearly 25% of the injected hot water from LPFS tubes into the flash tank instantaneously flashes into flash steam at saturation temperature leaving behind nearly 75% of water as condensate at saturation temperature. The saturation temperature of both the flash steam and the condensate water is lower than the temperature of water inside the tubes of LPFS maintained at high pressure, yet the flash steam maintains its gaseous form due to low pressure inside the flash tank. The latent heat of vaporization for the formation of flash steam (2257kJ/kg) does not come directly from the power input from the auxiliary power units but from the internal heat of injected water, thereby reducing its temperature from 235C to the saturation temperature at 0.6bar which is roughly 113C. For every kilogram of flash steam, 3 kg of condensate water is formed in the flash tank. So in order to create 1kg of flash steam, 4kg of water is circulated through the tubes of LPFS and released into the flash tank in 1 second. The condensate at saturation pressure of water is recirculated back to the tube system of LPFS inside the enclosed heater for reheating via pump.
The High Pressure Feeder System (HPFS) deals with formation of supercritical water under very high temperature and pressure. The critical point of water is 374C and 219bar pressure. Above this temperature and pressure, water behaves both as a liquid and gas, without boiling. The advantage of forming supercritical water is it behaves as steam but does not require the latent heat of vaporization. Supercritical water has been found effective in increasing the fuel efficiency of the coal powered or nuclear power plants on Earth since the energy of latent heat of vaporization does not need to be given to the water to heat it over the critical point.
In Mareekh Process, the supercritical water has two main uses; 1. Acting as a medium to increase the temperature of the saturated flash steam to convert it into a superheated steam by mixing thoroughly into it, and 2. Increasing the quantity of the superheated inlet steam being injected into the turbine, increasing the power production. The saturated flash steam from the flash tank of the LPFS can be reheated in a conventional manner by simply channelling it through tubes in the heater. But the advantage of adding mass to the superheated steam in the form of supercritical water is lost.
The HPFS sources its water from the condensate. For every 1.5kg of steam running through the turbine, roughly 1.4 kg of condensate is obtained (after losing 0.1kg of steam to the exterior to maintain the desired pressure and temperature in the last part of the turbine housing). For the sake of calculation we can consider 1.5kg of steam in the turbine with 1 kg of saturated flash steam from the flash tank of the LPFS, and 0.5kg is the supercritical water from the HPFS. This 0.5kg supercritical water is replenished from the condensate, leaving only 0.6kg to be recirculated through the LPFS and the remaining 0.1kg deficit is replenished from the recovery buffer tank. The purpose of reusing the condensate to resupply the entire water being converted into supercritical water is that condensate is formed from the condensing steam and is free from any contaminants or debris which is essential for the working of the HPFS. In LPFS, the particulate contamination will settle in the condensate in the flash tank and only the flashing steam is routed to the turbine. In HPFS, no boiling occurs and so any particles in the supercritical water will get injected into the turbine housing and deposit on the turbine blades and moving parts and risk clogging the system.
In the HPFS, supercritical water is produced by channelling the pure condensate water that is heating in an isochoric process through convoluted tubes inside the enclosed heater. Since the volume doesn’t increase in the isochoric heating of the water, the pressure rises along with the temperature preventing the water from boiling until it reaches beyond the critical point of 219 bar and 374 celsius. The temperature and pressure continue to climb as the water continues to flow through the tubes, reaching a whopping 350bar or above and temperatures in excess of 400C.
The supercritical water is then routed to an injector which telescopes inside the channel carrying the saturated flash steam from the LPFS flash tank. The supercritical water entering the injector at a very high pressure (250 bar) creates a strong venturi effect that draws out the flash steam from the flash tank and propels it in the injector. Since the flash steam is formed at 0.6 bar pressure, it cannot enter the turbine housing on its own which has a pressure higher than 0.6bar, say 2 bar inside the high pressure turbine housing. But thanks to the strong Venturi effect from the supercritical water being injected into the injector from HPFS, the mixture of supercritical water and the flash steam can be propelled towards the housing. As soon as this hot mixture with a temperature far above the saturation temperature for the pressure in the high pressure turbine housing enters the inlet of the housing, it completely disintegrates into superheated (dry) steam and expands violently. The rapidly expanding steam now flows through the turbine housing towards the low pressure turbine housing imparting mechanical energy to the turbines and rotating them. By the time steam reaches the low pressure turbine housing, where an extremely low pressure is maintained at 0.01 bar, the steam has lost nearly all of its enthalpy and internal energy. As it hits the rapidly rotating turbines, it nearly completely condenses into water at its saturation temperature for the pressure of 0.01bar. The pressure of the low pressure turbine housing cannot be maintained at the Martian atmospheric pressure of 0.006 bar as the saturation temperature for that pressure is below 4C which can cause formation of ice over the turbine and risk clogging the system. The pressure of 0.01bar is maintained through a pressure control valve which allows part of the steam in the low pressure turbine housing to escape to the exterior, say 0.1kg per second, while maintaining enough steam inside to impart the 0.01bar necessary for condensation of the steam into water at a saturation temperature of 7C, which stays in liquid form. The 1.4kg condensate water is now recirculated through the LPFS and HPFS as described above.
7.2. Thermodynamic calculations for the LPFS and HPFS
LPFS:
During the running of the turbine for power generation, the LPFS is replenished by the condensate from the flash tank and the turbine. If calculated for 1.5kg of steam injected into the turbine, the mass of condensate recovered from the flash tank is 3kg. The condensate from the flash tank is at the saturation temperature for 0.6 bar flash tank pressure which is nearly 85C. The remaining 1kg water for circulation through the LPFS to make 4 kg water comes from the condensate from the turbine (0.9kg at 7C) and the water from the recovery buffer tank (0.1kg at 30C) which in turn is constantly replenished from the subsurface water reserve. The heat given to the water at the LPFS (Q(LPFS)) can be calculated as follows:
Heat needed to increase the temperature of recovered condensate from flash tank from 133C to 235C (Q1)
Q1 = cmΔT Where c is the average specific heat of water from 86C to 235C = 3.5kJ/kg.K m = 3kg ΔT = 235- 85 = 150 Q1 = cmΔT = 3.5 x 3 x150 =1575kJ
Heat needed to increase the temperature of recovered condensate from turbine from 7C to 235C (Q2)
Q2 = cmΔT Where c is the average specific heat of water from 7C to 235C = 3.5kJ/kg.K m = 1kg ΔT = 235-7 = 228
Q2 = cmΔT = 3.5 x 1 x 228 = 798kJ
Heat needed to increase the temperature of recovered water from recovery buffer tank from 30C to 235C (Q3)
Q3 = cmΔT Where c is the average specific heat of water from 30C to 235C = 3.5kJ/kg.K m = 0.1kg ΔT = 235-30 = 205 Q3 = cmΔT = 3.5 x 0.1 x 205 = 72kJ
Total energy input into the LPFS to form 1kg flash steam is Q1 + Q2 + Q3 = Q(LPFS)
Q(LPFS) = 2445kJ
HPFS
The High Pressure Feeder System or HPFS deals with the formation of supercritical water to heat up and add mass to the flash steam. During the running of the turbine for power generation, the HPFS is replenished with water from the condensate recovered from the turbine. To generate 1.5kg of superheated steam to be injected into the high pressure turbine housing, the HPFS must convert 0.5kg of water into supercritical water by channelling it through the HPFS convoluted tube system inside the enclosed heater chamber in an isochoric process where the volume of the water is not allowed to increase as it heats up so its pressure increases tremendously taking the water into the supercritical range. As the temperature of water in the tubes increases, the heat requirement to increase its temperature sharply increases near the state-transition or pseudo-boiling. This is roughly the point where heated water’s properties transition from liquid to gas phase but water doesn’t turn into steam. The specific heat capacity at this point is very high at relatively lower pressures but at very high pressures such as those exceeding 300 bar, the heat capacity at state-transition doesn’t rise much. The increase in the heat capacity is only spread over a relatively short temperature range around the critical temperature point of water i.e roughly around 350C to 400C, which can be as high as 10kJ/kg.K. But for the other temperature ranges, the specific heat capacity of water remains around 3kJ/kg.K. We can average it out at 3 to 4 for a temperature range from 7C for the temperature of condensate water from the turbine to 550C for the superheated water produced inside the tubes of the HPFS. Please note that no latent heat of vapourization needs to be added as no boiling occurs during the formation of the supercritical water.
Heat required to produce 0.38kg of supercritical water from 7C water from condensate router pump from turbine to supercritical water at 550C at 350bar can be calculated as:
Q(HPFS) = cmΔT
Where
c is the average isochoric specific heat of water being turned into supercritical water. Here the value used is 3.5 but it may vary between 3.0 to 4.0
m is the mass of the water
ΔT is the temperature difference between the condensate and the supercritical water.
Q(HPFS) = 3.5 x 0.5 x (550-7)
= 950kJ
Total energy input (per second) = Q(Recovery) + Q(LPFS) + Q(HPFS) = 60kJ + 2445kJ + 950kJ = 3455kJ
7.3. The Inlet Steam
The supercritical water is responsible for heating up the flash steam to superheated temperatures
The temperature of the 1.5kg superheated steam can be calculated by looking at the dynamics of mixing of the 0.5kg supercritical water at 550C and 1 kg saturated flash steam at 86C.
The final temperature of the inlet superheated steam would be the function of the specific heat capacities of the supercritical water and the heat capacity of the saturated flash steam.
Supercritical water being hotter will give its energy to impart a temperature to the steam which is equal to the temperature of the supercritical water drops to, until it reaches a balance point with the steam being heated. As the supercritical water moves out of the isochoric very-high pressure environment of the tube system of the UPFS into the common injector where the pressure is much lower (0.6 bar at flash-tank end and 2 bar at the turbine end), it will form flash steam itself as it expands, except its temperature will still be in superheated tange ~ 400C and there will be no condensate.
The supercritical water under very high pressure, when released into the combined injector, will exert a strong venturi effect thus drawing in the flash steam from the flash tank and direct it towards the turbine.
The temperature of the superheated steam (y) formed by mixing supercritical water and the flash steam in the above scenario can be calculated as:
Heat transferred from the supercritical water to the flash steam is Q1
Heat acquired by the flash steam is Q2
Q1= c1m1ΔT1 Where c1 is the isochoric specific heat of the supercritical water = 3.5 m1 = mass of supercritical water ΔT1 is the difference between the temperature of supercritical water flashing at 2 bar and the temperature of the mixture
Q2= c2m2ΔT2 Where c2 is the specific heat of the flash steam = 2 m2 = mass of the flash steam ΔT2 is the difference between the temperature of the flash steam and supercritical water and the temperature of the mixture.
c1m1ΔT1 = c2m2ΔT2 3.5 x 0.5 x (673 - y) = 2 x 1 x (y - 359) 1.75(673-y) = 2(y-359) 0.875(673-y) = (y-359) 589 - 0.875y = y-359 589+359 = y+0.875y 1.875y=948 y=948/1.875 = 505K or 232C
0.5kg supercritical water at 300bar and 550C will combine with 1kg of flash steam at 0.6bar and 86C will create a mixture of 1.5kg of superheated steam at 232C.
7.4. Gross Power Output
The power output of the steam turbine is equal to the difference in enthalpies of the inlet steam into the turbine housing and combined enthalpies of the exhaust steam and the condensate at the end of the turbine.
The enthalpy of inlet steam of 232C temperature and at 2 bar pressure can be calculated from steam calculators.
TLV steam calculator (www.tlv.com)
Specific enthalpy of the inlet steam for the above parameters is 2931kJ/kg. For 1.5kg, it will be 2935 x 1.5 = 4402
The specific enthalpies of the end exhaust steam and condensate can also be calculated.
Mass of exhaust steam: 0.1kg
Temperature of exhaust steam:7C
Pressure of exhaust steam: 0.01bar
Form: Gas
Nature: Saturated
The enthalpy of the saturated steam at 7C is 2513kJ/kg which also takes into account the latent heat of vaporization it is still carrying.
The enthalpy for 0.1kg steam will be:
2513 x 0.1 = 251kJ
The same table also gives the specific enthalpy of saturated water at that temperature which is 29.4kJ/kg.
For 1.4kg of condensate water, it comes as:
29.4 x 1.4 = 41kJ
So the total enthalpy of the end exhaust steam and the condensate water will be:
251 + 41 = 292kJ
The gross energy output of from the turbine as a difference between the enthalpies of inlet steam and that of the exhaust steam and condensate is:
4402kJ - 292kJ = 4110kJ
The conversion efficiency of a typical steam turbine is around 95%
So the gross output will be 4104 x 0.95 = 3905kJ
Assuming the entire cycle is calculated for one second, the gross power output can be calculated as 3905kJ/s or 3905 kilowatts
This can also be calculated directly with the help of US Department of Energy’s online steam turbine calculator (www4.eere.energy.gov)
In the above mentioned department of energy calculator, the gross energy output is nearly the same as our calculations if the enthalpies of the exhaust steam and the condensate are factored in.
7.5. Net Power Output
Net power output (per second) is the difference between the energy input from the recovery, LPFS and HPFS, and the gross power output at the turbine.
3905kw - 3455kw = 450kw
This is a good amount of net power in ideal circumstances. However, we can factor in the heat loss in the subsurface reservoir which can be substantial. Other points of heat loss will be the Sh-Sc pump, the slurry removal unit, the pumps for the LPFS and HPFS, and the condensate router pump. In a typical steam power plant though at a much larger scale handling many times more mass of steam and water, the feedwater and condenser pumps consume up to 240kw of power. So we can roughly speculate a power consumption of upto 150kw by the pumps of Mareekh Process and the subsurface heat (power) loss. This still leaves us with over 300kW of power per 1.5kg of steam generated.
This is a decent amount of power that can power a small base. In real life, the power plants may be 10 times bigger, generating 6-10 MW of power. 3-4 of such power plants may be able to sustain a large human base on Mars and sustain the need of mining, construction and manufacturing operations on Mars.
The main purpose of supercritical water is to increase the temperature of the flash steam to superheated steam while increasing the bulk and energy content of the injected steam.
For 1.5kg steam, one third of the mass is the supercritical water. Producing and handling of the supercritical water takes extreme care as extremely high temperatures and pressures are involved. The fraction of the supercritical water needs to be carefully calculated to ensure safety while achieving optimal power output.
For example, if for 1.5kg injected steam, 1.25kg is the flash steam at 86C and the amount of supercritical water is only 0.25kg at 300 bar and 550C, the energy input into the system will 3316kJ and the output will be 3944kJ at 95% conversion efficiency of the turbine. Factoring in heat losses of the final steam (~292kJ) and the condensate and the power consumption of the pumps (140kW), the net power output is nearly 200kW per 1.5kg of inlet steam produced.
8. Mareekh Process and the apparent energy paradox
The fundamental question is, where is this extra power coming from. Ice is not a source of energy. In fact the subsurface water gave up the heat of fusion to convert into ice as Mars cooled down while losing its atmosphere. Further, the subsurface ice further lost its internal energy while cooling down to reach its current frozen state of -70C deep underground.
The answer perhaps lies in the very deep heat sink in the form of very low atmospheric pressures and temperatures. The main energy consuming part of the Mareekh Process is an isolated system under high pressure only open to the deep underground water reservoir at very high pressure while the rest of it is enclosed and sealed from the external low pressure environment, except for the steam turbine housing which is open to the exterior. Inside the Mareekh Process, we are giving energy to recovered water and increasing its internal heat and enthalpy and then exposing it to a very deep heat sink to extract the input energy plus a bit extra attributed to the deep heat sink leading the output steam to very low energy state in the form of ice vapour at near vacuum pressure.
Enthalpy is a state function. It does not matter which pathway it took to reach that enthalpy state. In the Mareekh Process, we gave energy to the extracted subsurface water in a highly specific configuration thus giving it a high amount of enthalpy with minimal energy input, both of which can be calculated using a variety of methods and calculations. The change in enthalpy of the steam at the inlet of the turbine to the escaping vapour in the atmosphere and the condensate water is huge, due to a very deep heat sink i.e Martian atmosphere, which translates into mechanical work.
8.1. Does Mareekh Process follow the Rankine Cycle?
Rankine Cycle is a graphical representation of the energy cycle of a steam turbine in a closed loop, rejecting heat externally and extracting mechanical work.
Rankine Cycle (Picture source: http://www.scientificlib.com/en/Physics/Thermodynamics/RankineCycle.html)
Perhaps the most important part of the Rankine Cycle is the drop in temperature of the steam on the right due to expansion as the high pressure steam moves towards the low pressure inside turbine housing and does mechanical work, with little change in the entropy. Another important part of the thermodynamic cycle is where the system drops the internal entropy of the system while condensing the steam to the condensate by rejecting heat to the outside of the system (thus increasing the entropy of the outside environment, as the second law of thermodynamics cannot be violated).
On Mars, there is a very deep heat sink naturally in the form of very low atmospheric pressure and temperature; thus obviating the need of the surface condenser to achieve these parameters. Any enthalpy over and above the extremely low enthalpy of the heat sink can be translated into mechanical work. This notion does not tend to violate the second law of thermodynamics as the mechanical work done in any form outside the Mareekh Process from the generated electricity will eventually convert into heat; whether from friction of mechanical parts of the machinery, smelting of ore, heating the internal environments or lighting etc., which will increase the entropy of the environment directly as a result of the working of the Mareekh Process.
9. Conclusion
One of the biggest challenges in establishing a long-term or permanent human settlement on Mars is finding a reliable, sustained and substantial source of power. Mars lacks conventional resources for power generation. This includes low solar flux which can also become unavailable for many months at a time during global dust storms, no harnessable wind power due to extremely thin atmosphere, absence of fossil fuel, no known geothermal or radioactive mineral reserves, and no prospect of any hydro or tidal sources of power. Solar power and limited nuclear power in the form of Radioisotope Thermoelectric Generators carried from Earth may not be able to sustain human settlements any bigger or longer-term than small, short-term research bases.
Mareekh Dynamics proposes a novel method of power generation on Mars which may be able to sustain a long-term and large-scale human settlement on the red planet.
The surface of Mars locks relics of its ancient wet past in the form of huge deposits of permafrost or subsurface glaciers. The extremely low atmospheric pressure and temperature on Mars can potentially create a very deep heat sink for the extracted heated water from the permafrost using auxiliary power which when exposed to the surface, will be able to run steam turbines through explosive expansion in an extremely efficient manner. Our patented hybrid power generation technology, “The Mareekh Process” utilizes the low pressure and temperature of the Martian atmosphere to obviate the need of surface condensers, thus vastly improving the efficiency of the Rankine Cycle. It further improves the efficiency of the input energy by utilizing supercritical water, and also by avoiding steam generation in any of the energy input steps of the process, reducing the energy consumption.
(P.S. This blog article is currently being edited)