GB2565811A - Sublimal sequential condensation carbon dioxide turbine (SSCCDT) - Google Patents

Abstract

Freezing and sublimation of carbon dioxide is achieved by the use of liquid nitrogen and geothermal heat by way of capillary tubes (3 and 4, fig 2), which may be located in preferably spherical chambers 7 that may have fluted entrances and exit pipes 8,9 , into which the capillaries may protrude. The heated and expanded CO2 is delivered to the turbine blades 2 at high pressure by way of helically corrugated pipes with fluted inlets and outlets that increase the flow rate. Additional solar energy may be applied to the gas as it passes through the turbine. The CO2 gas exiting the turbine is preferably directed back to a spherical chamber wherein capillaries filled with liquid helium or liquid nitrogen may be used to freeze the CO2 before the capillaries containing geothermal heat again warm the solid CO2 causing sublimation. Valves may be used to prevent the gas leaving this chamber until a certain pressure is achieved. After heating the CO2, the geothermal heat may be exchanged in a heat recovery system.

Description

DESCRIPTION

SSCCDT stands for Sublimal Sequential Condension Carbon Dioxide Turbine. Condension is an artificial conjunction of condensing and expanding.

Current electricity turbines use water (steam) to provide the kinetic force to turn the blades on an electric turbine. Water has been used as the medium of choice since the advent of the steam generator. Water is great for life due to its unique properties such as hydrogen bonding, but these very properties make it a poor and inefficient choice of a kinetic vector and transfer agent.

Water is a di-pole molecule. In essence, the hydrogen atoms on the water molecule are arranged at one end of the molecule. This leaves the exposed nucleus and protons therein on one side and the heavy negative charge on the other. Consequently, water molecules attract one another. A phenomenon called hydrogen bonding. This effect requires a huge amount of energy to overcome in order to get water to convert to steam. Even in the vapour state, water molecules still weakly attract each other, hence the specific heat capacity is still quite high even in the vapour state.

The process works by first heating water to 100 degrees Celsius and converting the water to steam.

Water has a molecular mass of 18. Energy required for boiling water to steam per kg is as follows.

100 x Specific Heat Capacity of water + Latent Heat of Vapourisation.

100 x 4.2 = 420KJ + 2260KJ = 2680KJ = 1kg of steam at 100 degrees Celsius.

In order to turn a typical steam turbine, the steam needs to be superheated to 192 degrees Celsius.

(192 - 100) x 2.1 (SHC of steam) = 92 x 2.1 = 193.2KJ.

192 degrees Celsius of steam is equivalent to 83 PSI

Total energy required for just 1kg of 192 degrees Celsius = 2680 + 193.2 = 2873.2KJ.

In order to get the maximum pressure differential across the turbine blades, the volume of steam is dramatically reduced by condensing the steam.

Hence the latent heat of vapourisation is given up for each 1kg to obtain 83psi of force. Therefore the amount of energy per PSI is 83/ (2260 + 93) = 28.34KJ/PSI.

Steam has an expansion ratio of 1600.

The inefficiency of steam arises from the lost energy in vapourisation which is not reclaimed in condensation. This is separate to the energy losses in the turbine.

Carbon Dioxide or any sublimate gas behaves as follows.

Sublimation is a physical change of state whereby a gas changes state to a solid without passing through the liquid state. This physical change is a reversible reaction and releases and absorbs a fixed quantum of energy. The key is the reversibility without energy loss making it ideal for batteries which is covered under another related but separate patent.

There are number of gases which sublimate. Ammonia and Carbon dioxide are two common examples. The former is toxic whilst the latter is currently in excess in the atmosphere but is fairly inert to health except in high concentrations. Given most systems are not hermetically sealed and have some leakage, the use of CO2 is ideal.

Carbon dioxide is a better choice of kinetic vector for turbines. It is a linear molecule with the oxygens arranged on either side of the carbon atom. Hence it is more electrically neutral than H2O.

Carbon Dioxide Sublimates at -78 degrees Celsius (194K approximately). It has an expansion ratio of 845.

One kg of Dry Ice (solid CO2) occupies 0.666 litres in volume.

The Specific Heat Capacity of CO2 is 0.82KJ/Kg. It molecular mass is 44. This is important as force is mass multiplied by acceleration, that is F=M x A.

The amount of energy required to produce a given increase in temperature and force is described by the Specific Heat Capacity of a substance. In a gas or a liquid, the movement of molecules or atoms is a measure of temperature. The forward kinetic motion of a substance is key to turbine efficiency.

Steam has a Specific Heat Capacity of 2.1KJ/Kg/K as opposed to CO2 which has a Specific Heat Capacity of 0.82KJ/Kg/K. Hence for a given amount of energy supplied (amount of increase in temperature), CO2 will have over double the kinetic energy of steam. The amount of force applied per given acceleration is higher in CO2 than water. It is noted that CO2 is heavier than water in terms of molecular weight and the SHC is therefore four times that of steam as one Kelvin results in a higher translational force of a heavier molecule.

Furthermore using the equation F=M x A, it follows that for a given acceleration CO2 has a greater mass and therefore will exert a greater force on the turbine blades.

In summary, CO2 takes less energy to accelerate and has a greater force on turbine blades than steam. As discussed above, one Kelvin equivalent of energy will result in a four-fold increase in force compared to steam.

Calculation for lKg of CO₂ at 55 °C that is 328 K at a volume of 10 L is shown below.

PV = nRT is the gas equation.

Pressure = 227 x 0.0821 x 328/10 = 611.28 atm = 8983.339 Psi per 10 kg of CO₂.

The efficiency of a turbine is limited by Carnot's Theorem. 60% is an excellent efficiency. The efficiency of a turbine is affected by the energy losses in converting heat energy to mechanical energy and from this into electricity.

The Siemens SST 060 turbine has a range of 2MW to 6MW with an operating pressure of up to 1900 Psi for a 6MW production. Allowing for the efficiency factor, we will need a constant volume of 120 kg of solid CO2 being vapourised (to include the volume of pipe work, the expansion chamber within the turbine and the exhaust pipes and storage cylinders).

The turbine as designed works on a cyclical cylinder rotation basis. 120 kg of CO2 would be solidified quickly using a cryo-cooler and while at the same time another 120 kg would be exposed to 55 - 60 degree Celsius water to expand the previously solidified CO₂. The final volumes and metric are dependent upon variable factors such as type of turbine blades, expansion chamber and exhaust sublimate cylinders.

The CO2 sublimate turbine and energy storage device moves away from using water as a kinetic vector. Solid CO2 is used in a sealed turbine unit. The amount of CO2 within the sealed unit is dependent upon the turbine and the heat source applied. In a geothermal application, outlet fluid from the deep geothermal borehole is passed to a heat exchanger which will raise the temperature of its exchange fluid to 55 - 60 degrees Celsius or 333 Kelvin. The heat exchange fluid will pass directly through the CO2 cylinders. The cylinders are 10 litres in volume each and will contain 10 kg of 6.66 litres of solid CO2. The exchange fluid will cause the CO2 in the cylinder to expand. A pressure valve on the cylinder will prevent release until say 1300 Psi is reached. The valve will then open and release all the CO2. The exchange fluid will then cease to flow into this cylinder and will move to the next cylinder in the sequence.

The CO2 cylinder 5 is specifically designed with special entrance nozzles 1 and exit nozzles 2 detailed in figure 2. Each nozzle is a conical funnel with moulded ridges in a helical design. This conical design with helical grooves, causes the exit expanded CO2 gas to accelerate on exit. The helical grooves increase the vortex effect which increases gas acceleration. The pipes leading to the turbine chamber all have helical grooves to continue the gas acceleration.

The number of cylinders heated and the volume, and therefore pressure of gas required is dependent upon the electrical output required from the turbine. The greater the demand, the larger the number of cylinders heated and larger is the kinetic force applied consistently to the turbines.

The efficiency of the turbine is dependent heavily on the pressure differential across the entrance and exit of the turbine blades. To assist in this, the turbine has only one entrance pipe to maximise the inlet force but multiple exhaust pipes flowing into multiple cylinders. The greater the exhaust area, the lower the pressure at exit. To assist in this and to provide the greatest differential, the exhaust pipes lead to cylinders that are being cooled using a nitrogen cryocooler. In figure 1, the cryocooler 6 is freezing the exhaust CO2 gas causing the CO2 to solidify and contract by 845 times its volume. The faster the contraction, the greater the negative pressure or pressure differential across the turbine. The cryocooler pipes and the heating pipes are designed using organic biological ideas such as seen in capillaries in the skin. The small thin pipes 3 carrying geothermal heat and the pipes 4 carrying liquid nitrogen from cryocooler rise into the chamber in a capillary design as shown in figure 2. This provides the greatest surface area for the CO₂ to be exposed to heat or the cryocooler liquid nitrogen.

As soon as seven litres of gas has passed per cylinder, the cylinder's valve will close and the exhaust CO2 will be passed into the next cylinder to cool.

This system will provide the greatest pressure differential across the turbine and provide an efficiency above those in steam or diesel turbines.

The geothermal and storage applications are described below.

In figure 1, the CO2 closed turbine 4 with additional solar heat gain 1 can therefore convert low grade heat into electricity. The biggest failing in geothermal heat uptake has been the transmission of the energy obtained from the ground. Currently geothermal heat is used in district heating systems. Heat losses over distance makes transmission of heat over large distances expensive and impractical and would require major investment in thermally insulated pipping networks. However, the CO2 turbine allows the geothermal heat to be converted to electricity and transmitted using existing infrastructure.

Typically 12 x 600m boreholes would provide sufficient energy to power a 6MW turbine. The deeper the borehole, the greater the heat.

Storage Applications for CO2 Turbine as a Gas Battery is described below.

It follows that the sublimation of CO2 is a reversible physical reaction and that frozen CO2 provides potential energy. The more CO2 that is frozen using electricity to provide the energy to the cryocooler, the more energy is stored for release later. The amount of potential energy stored and available for release is directly dependent upon the volume of CO2 available, the size of the cryocooler and the turbine size to release the energy. Using the same system for a different application. In effect, the process is like creating a battery.

Turbine design specifics are as follows.

All electricity turbines work on the principle of using a medium to create a kinetic force which turns a fixed magnet inside an electromagnetic coil creating electricity. There are AC and DC turbines but in the main, a pressurised gas is forced across fixed blades which cause lift and rotational forces. The efficiency of the turbine is affected by the differential of pressure across the blades. The higher the inlet pressure and lower the outlet pressure, the greater the flow rate of gas across the blades. This increase in flow rate results in greater lift and rotational force.

The key differential in the CO2 turbine design is in the condensing cycle and the reduction of pressure across the turbine fan.

In the Sublimal Sequential Condension Carbon Dioxide Turbine (SSCCDT), as in figure 1, the entire system is a self-contained 10 closed loop turbine. The in-let pressure is directly proportional to the volume of CO2 in the closed system and the heat energy applied to the CO2 contained in the system.

The design consists of several novel elements and some standard elements.

The turbine or blades of the design are fairly generic and can be the same as that used in a conventional steam turbine.

The proprietary elements are as follows.

1) In-Let and Outlet Pipe Factoring and Design is explained here. The pressure across the turbine is reduced by having a greater factor of outlet pipes to inlet pipes. In figure 1, the in-let pipes 3 are arranged to create a laminar flow across the blades 2. Most modern turbines have a few in-let pipes but a static blade to force air flow across the rotational blades behind the fixed blades. This system works well but does increase air resistance which in turn reduces mechanical force. As shown in figure 1 to reduce the pressure of gas at the opposite end of the turbine, the outlet pipes have to be fluted like a trumpet 9 and have to exceed the inlet pipes by a factor of at least four preferably eight. The opposite is true of the inlet design which graduates to a smaller diameter to increase the exit velocity. The outlet and in-let pipes are moulded with a helical interior which causes forward linear vortexing. The speed of the gas is increased by forcing the gas to swirl at the edges. This increases the velocity of the gas on the outside and decreases the turbulence of the gas in the centre of the pipe. The purpose of the helical internal pipe mould is to force vortexing and this increases the flow rates. The in-let flow rate is higher and the exit flow rate is lower resulting in a greater differential.

2) In figure 1, the outlet pipes are large in diameter and gradually increasing in diameter 8 until they reach the CO2 expansion-sublimation chamber 7. The chambers entrance from the turbine is also fluted allowing the gas to expand across the chamber rapidly. The expansionsublimation chamber has two series of pipes extending into the 'bulb like chamber'. The pipes are representative of capillary vessels in the skin. The two sets of alternating pipes figure 2 represents are the cryocooling pipes 4 and the heat pipes 3. The cryocooler pipes will carry liquid nitrogen or liquid helium into the chambers. This will cause the CO2 to freeze as liquid nitrogen has a boiling point of 77K or -197 °C. The liquid will be pumped through the pipes in the expansion-sublimation chamber. This will result in the rapid contraction of the CO2 in the chamber and create a negative pressure gradient sucking in more CO2 from the turbine chamber. As it can be seen in figure 2, the capillary tubes of the chamber are arranged uniformly around the chamber but the cryo-capillary tubes are absent at the exit of the chamber and the heating capillary tubes are absent at the entrance of the chamber. The capillary tubes extend into the chamber creating a greater surface area for heat absorption or transfer of the CO2.

Liquid Helium can and will also be used, however the commercial availability of liquid Nitrogen makes Nitrogen the initial choice. However, Helium has a higher specific heat capacity, which means it can cool on a smaller volume of liquid Helium. It would take 5 times the mass of liquid Nitrogen to produce a 1 Kelvin reduction in temperature.

3) The condensing-expansion (conjunctive description condension) chamber is shaped spherically as this creates the maximum exit force when the CO2 is heated from the gas state. The spherical double walled vacuum chamber has a fluted entrance and a conical exit. The fluted entrance provides a large exit area for the CO2 leaving the turbine. The gas will rapidly fill the chamber and come into contact with the capillary tubes covering the cryocooler, freezing itself into a solid. The lower the exit pressure, the less is the CO2 exit temperature and less is the energy that will be expended by the cryocooler on causing solidification. This completes the cycle.

Claims (8)

1. The Sublimal Sequential Condension Carbon Dioxide Turbine uses geothermal heat and liquid nitrogen via capillary tubes to freeze and sublimate carbon dioxide respectively and deliver it at high pressure using helically corrugated pipes with fluted inlets and exits to increase flow rates on to the turbine blades for generating electric power.

2. The invention according to the preceding claim, introduces a new way of utilizing CO2 by solidifying it to dry ice in specially designed cylinders and expanding it to form high pressure gas in the same cylinders.

3. The invention according to the previous claims uses fluted or trumpeted inlets and exits on the pipes to increase fluid flow rates.

4. The invention according to the preceding claims uses the higher surface area of the capillary tubes to expose maximum amount of CO2 to liquid nitrogen for freezing, and geothermal heat for sublimating, after which the heat is then exchanged in a heat recovery system so no energy is wasted.

5. The invention according to the preceding claims makes use of CO2 which in comparison with water has higher molecular thrust force and requires less energy to convert to gaseous form.

6. The invention according to the preceding claims, can generate power at higher efficiencies than a steam turbine.

7. The invention according to the preceding claims, can be made more compact and lighter than a conventional turbine which uses steam as working fluid.

8. The invention according to the preceding claims, adheres to EnGen principles and generates zero emissions.