NL1043369B1 - Carbon dioxide power generation - Google Patents

Abstract

Closed loop carbon dioxide power generator with temperature gradient Fig. 1, consisting of containers Cl and C2 filled with CO2 fluid, subject to gravity. C1 and C2 are connected by gate A above and B below, vertical distance A-B is H, called head. For C1 a top up cone effective head Hl = % H. For C2 a top down cone effective head H2 = 3A H. Turbine-generator 1 is installed at B with draft tube 2 in Cl. Heater 3 in 2 heats up the passing fluid getting lower density than the surrounding fluid, so it floats up. The effective head and density differences contribute significantly to the power production. The modules are suitable for massive aquatic refuges and for powering future Mars colonies.

Description

Carbon dioxide power generation Technical field The technical field is cyclic fluid power generation. The invention uses carbon dioxide in closed loop, under gravity. Priority is claimed of application NL 1043242 date April 26 2019 [1], modified with a temperature gradient. Background The differential gravity power generator is developed in [1] using water as cyclic work liquid. Cyclic implies water conservation, in contrast to traditional flow-through hydro lake power plants. As water becomes scarce and building new hydro lakes is restricted, water conserving methods are immensely important.

Other fluids, like carbon dioxide (CO) liquid [2] and supercritical fluid (sCO2) [3], can be utilized, instead of emitting this greenhouse gas in the atmosphere [4] at > 36 GT/yr. The method can also be applied on Mars, with 95% CO: gas in its atmosphere [5] and dry ice on the poles [6]. Abundant electricity helps to solve many problems for future colonies. With water (ice) [7] it facilitates LED-light farming and oxygen production, for breathing and rocket fuel. Developments with sCO: [3, 8] are discussed shortly in the final section. Description of the inventive steps The isothermal case at temperature T is first considered. The differential gravity power generator (DGPG) [1] is described with the help of Fig. 1, depicting a vertical cross section of a container with CO: fluid of density p at constant pressure p in two compartments Cz and Cz, which are connected by gate A above and gate B below. B is taken as the zero of the potential energy in a gravity field g attractive downward. Vertical distance of A-B is H, called head. A turbine-generator 1 is installed at B with its draft tube 2 in C:.

The potential energy depends on the CO distribution as a function of the height in C: and C2. For example, for C a top up cone the effective head Hi = % H and for C; a top down cone Hz = % H. H2 — Hi = % H, which is the same as for a rectangular or cylindrical hydro lake [9]. However, the capacity of a single lake for the cyclic DGPG can be 15x10* times that of the same lake for flow-through operation, as discussed in [1, 10].

A temperature gradient is introduced to make fluid density in C1 lower than the fluid density in C:. It is not necessary to do that for the whole fluid in Cy.

It is sufficient to lower only the density of the fluid discharged through the draft tube.

This is done by a heater 3 installed in the draft tube 2 of the turbine-generator 1, Fig. 1. The remainder in C: has the same density as in Cz, which will float up the lighter fluid.

Table 1 helps to make a choice for the application of DGPG in the CO; liquid state or supercritical state and where it is of advantage to use a temperature gradient.

The modification with a temperature gradient will be denoted as DGPG-TG.

With flow rate Q at B, the power P is: P=Qg(p2H2—p1Hi) Eq. 1 To show the large effect for relatively small temperature difference, C: and C; are taken to be cylinders, so Hi = H2 = % H (m); p = 7.5 MPa isobar.

Without a temperature difference, P = 0. With Ti = 320 K, pi = 203 kg/m? and T2 = 280 K, p2 = 919 kg/m3, P=%QgH (0.716) (kW). Q depends on H [1, 9]. Assuming H = 10 m, g = 9.8 m/s? such that Q=1m?/s, P= 35 kW.

So the temperature difference is crucial in this case.

With the same numbers, for conical C; and C2, P = 62.5 kW, while for Ti = T2 = 280 K, P = 45 kW.

Table 1: CO; density p as function of T forp = 7.5, 8, 10 MPa and g = 9.8 m/s? p=7.5MPa p= 8 MPa p = 10 MPa T{K) p (kg/m?) p (kg/m?) p (kg/m?) 220 1181 1182 1186 240 1107 1109 1115 260 1024 1027 1035 280 919 923 938 300 734 753 802 305 390 657 752 320 203 232 448 340 162 179 259 Data in Table 1 are rounded off from data of Span and Wagner [2]. Critical Te = 304.3 K (31.2°C), pc = 7.4 MPa [3]. Triple point: T= 216.6 K (-56.5° C}, pt = 0.5 MPa.

Short description of Fig. 1 Fig. 1 depicts a vertical cross section of the DGPG-TG with C: a top up cone and C; a top down cone, connected by gate A above and gate B below. The vertical distance A—-B is H, called head. Turbine-generator 1 is installed at B, with its draft tube 2 in Cy, including aheater3. Preferred applications In the quest for refuges against global catastrophic events that are threatening human existence on earth, two solutions have been proposed: 1) Move a million people to Mars, proposed by Elon Musk. 2) Aquatic refuges in nuclear submarines to live in the oceans for a while, reviewed in [11]. For both alternatives the energy provision is not yet properly solved, besides the limited scope of the rescues, compared to the world population. With regard to energy supply, in 1) NASA/SpaceX plan to use solar panels and nuclear power < 10 kW lasting for 1 year and in 2) there are not enough nuclear submarines.

DGPG and DGPG-TG fulfil the needs for long lasting abundant energy sources which can be installed everywhere, above ground, underground or submerged, even deep in the oceans. The work fluid can be water in open or closed containers, as already discussed in

[1], or CO: in closed containers. For both earth and Mars the technique with CO is to be developed first on earth. The embodiment of a CO, power generator for Mars can be prefabricated on earth and send to Mars. Simulation and training in handling and application of the DPGP-TG should be given to future Martians.

Apart from dealing with catastrophic events, developing the DGPG was needed against the adverse effects of climate change, so using CO; fluid for power generation is even more crucial. It also follows from the data in the description that storage of CO: as fluid in reservoirs in the oceans is more convenient than usual carbon storage as gas [12]. The pressure needed can be provided by the hydrostatic pressure at a given depth.

Finally, the invention deals with CO. in the liquid state, for temperatures between T; =

216.6 K (- 56.5°C) and Tc = 304.3 K (31.1°C), and supercritical state below 340 K at p < 10 MPa. Developments on sCO: reviewed in [3, 8] operate at temperatures > 800 K and pressures > 20 MPa combined with heat from nuclear or coal burning plants, quite different categories of power plants, which have no overlap with the invention.

Note related to the written opinion of the search report No change needs to be made in the text of the application The claims are rewritten to elucidate the inventive steps.

The present application is denoted by DO.

D1: WO 2010/01707 A2, De Almeida Giovani Ferreira, 18 February 2010, D2: CN 104180694 A, Harbin Xiangkai Technology Dev Co Ltd, 3 December 2014. Comparison between DO and D1 In DO, see Fig. 1, the two containers C; and C; including the two gates A and B are al! under the same pressure of typically > 10 bar (1 MPa) in the normal liquid region, till 100 bar in the supercritical region.

There cannot be an empty tube between C; and C,. In D1 e.g. page 10 line 10 reservoir (1) and reservoir (7) are connected by an empty tube (3). So D1 cannot be used for the carbon dioxide power generator described in DO.

Moreover, the international search report for D1 states: “no meaningful international search can be carried out”. See WO 2010/01707 A3, De Almeida Giovani Ferreira, 18 February 2010 for the problems commented by the search authority.

Conclusion: D1 is not valid for DO and therefore the written opinion is not justified.

Comparison between DO and D2 D2: The invention discloses a gravity type heat pipe and belongs to the field of heat conduction technologies.

The heat pipe is a hollow tube 1, filled with supercritical carbon dioxide liquid 2, closed at both ends.

Internal pressure in the tube is between 7.3 MPa and 10 MPa, at temperatures of 60 to 100 °C.

Working principle: Pipe 1 is set vertical or tilted.

Heating the low end causes the fluid to flow up releasing heat at the upper end, becoming colder, heavier and flows back, forming convection repeatedly.

It follows from the description that “gravity type” in D2 means the effect of temperature on the mass density.

In DO, besides the effect on mass density, gravity effects also the potential energy in such a way that the potential energy density for a top up cone differs from that of the same cone with top down.

This important aspect of DO is not present in D2. DO works for constant temperature of the embodiment, whereas D2 does not.

D2 is not a gravity power generator in the sense of DO.

References

[1] Emid S., Differential gravity power generator, application NL 1043242 April 26 2019.

[2] Span R. and Wagner W., J. Phys. Chem. Ref. Data, Vol. 25, No. 6, 1996.

[3] https://en.wikipedia.org/wiki/Supercritical carbon dioxide 5 [4] https://en.wikipedia.org/wiki/List of countries by carbon dioxide emissions

[5] https://en.wikipedia.org/wiki/Atmosphere of Mars

[6] https://en.wikipedia.org/wiki/Martian polar ice caps

[7] https://en.wikipedia.org/wiki/Water on Mars

[8] energy.sandia.gov/energy/renewable-energy/supercritical-co2/

[9] Emid S., High capacity factor hydro power plant with variable intake, NL 1041539, application date October 20 2015, granted May 9 2017.

[10] Emid S., Hydropower with superconducting penstock, NL 1043285 application June 4 2019.

[11] Turchin A. and Green B. P., Aquatic refuges for surviving a global catastrophe, http://dx.doi.org/10.1016/j.futures.2017.03.010

[12] https://en.wikipedia.org/wiki/Carbon capture and storage

Claims (4)

Conclusions Gravitational power generator, characterized by two equally high reservoirs 1 and 2 of known geometry, such as a wedge, cone or pyramid, filled with incompressible liquid, under desired pressure, placed in a gravitational field that pulls downwards. The centers of gravity of the liquids in 1 and 2 are known from geometry. The orientation of 1 is top up; that of 2 is with the top down. As a result, the potential energy density of the liquid in 1 is less than that in 2, for a known amount. By connecting the reservoirs 1 and 2, top with opening A and bottom with opening B, liquid flows from 2 through B to 1. Due to mass retention, an equal amount of liquid flows from 1 through A to 2. That way there is a gravity-driven power generator, with cyclical use of the fluid, so without consumption thereof. Dissipative losses of the device are taken into account in the capacity factor. Method according to claim 1, characterized by a temperature gradient over a temperature range containing the critical temperature of the liquid, where the change in density as a function of temperature is large. The temperature gradient is arranged in such a way that the density of the liquid flowing out of 2 through port B in 1 becomes much smaller than the average density of the liquid in 1 and 2. As a result, the lighter liquid flowing into 1 is reduced by the greater buoyancy of the surrounding liquid floated up. Method according to claim 2, for generating electricity with liquid carbon dioxide as a liquid and a turbine generator in the bottom connection of the reservoirs, wherein the liquid in the discharge of the turbine generator is heated by a heating element to maintain the density of the reducing passing fluid relative to the surrounding fluid, so that the lighter fluid is propelled upward by the surrounding fluid. The method of claim 3, wherein the heating element forms an integral part of the cooling system of the turbine generator to utilize its operating heat.