Atmospheric Vortex Engine

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7. Atmospheric Vortex Engine

7.1 What is an atmospheric vortex engine?

An atmospheric vortex engine is a device for producing energy using a controlled vortex.  An atmospheric vortex engine works by "spinning" low-grade waste heat into a vortex which extends up into the atmosphere.  Various design configurations for atmospheric vortex engines have been proposed.

The following conceptual images show what an atmospheric vortex would look like.

AVE the future

For an introductory presentation on the AVE go to: AVE Introductory Presentation

For a detailed technical description go to: AVE Technical Description

7.2 How is the vortex produced?

The vortex is produced by directing warm air tangentially into a circular arena so that it spins about the vertical axis as it rises.

7.3 What is the role of Coriolis force in an Atmospheric Vortex Engine?

Coriolis forces will have minimal or very little significance for an Atmospheric Vortex Engine. Although Coriolis forces play a role in formation of large natural vortices, in an Atmospheric Vortex Engine the tangential air inlet entries deflect the incoming air and provide the rotational motion. Depending on the geometry of the tangential air inlets, an atmospheric vortex engine could be configured to produce a vortex which spins in either the cyclonic or anti-cyclonic direction. For further discussion see FAQ 10.1.

7.4 How is the power produced?

Refer to the diagram below for a visual description of the AVE power cycle.

The power is produced in peripheral turbines. The turbines can exhaust either upstream of the tangential entries or in the center of the vortex. A 200 MW vortex engine could have 20 x 10 MW turbines each driving a 10 MW electrical generator.

ave power cycle Higher resolution version of the above figure - PNG (565 KB) 7.5 What is the minimum size of a vortex engine?

Physical models and dust devils show that it is possible to produce very small vortices. There is a minimum economical size for vortex power producers and vortex cooling tower because small vortices are more likely to be disturbed by the wind and because there must be an attended control system. The minimum practical size could be 50 MW(t) for vortex cooling towers and 50 MW(e) for vortex engines.

7.6 Are there different types of vortex engines?

The are many ways of using the atmospheric vortex engine concept. The heat source for a vortex engines can be waste heat or natural heat. Waste heat has the advantage that it is has a temperature slightly higher than natural heat. Getting rid of waste heat is a costly process which the vortex engine could convert to a profit center.

1. Vortex Cooling Tower. Vortex cooling towers without turbines could be used to replace conventional cooling towers thereby eliminating both the need for power to drive cooling fans or the need for the costly high hyperbolic natural draft stack. Vortex driven air flow could be greater than fan driven air flow thereby reducing cooled water temperature and increasing the output of the conventional part thermal power plant.

2. Vortex Engine. In a vortex engine the differential pressure at the base of the vortex is used to drive turbines and to produce additional electrical power. Adding a vortex engine to a thermal power plant could increase its electrical output by 40% by converting 20% of the plants waste heat to mechanical energy in turbines. In addition to the power produced in the vortex engine turbine, a vortex engine would further improve thermal power plant performance by reducing cooling water temperature as a result of higher air flow and of reduced pressure in wet cooling tower.

3. Vortex Producers. The vortex engine principle could be used to make artistic fountain-like vortex producers. The vortex could be made visible by injecting smoke, water droplets or flames. The vortex could be illuminated at night. While a vortex engine has a minimum size, there is no minimum size for vortex producers although larger vortices would be better at withstanding wind. The vortex would sway with the wind. The vortex could be modulated by varying heat input and inlet air flow.

4. Vortex Engines using warm sea water as the heat source. The heat source for a vortex engine can be any warm water source. The energy source for hurricanes can be sea water at temperatures as low as 26 °C. Sea surface temperatures (SST) in the tropics are commonly above 29 °C. Using warm sea water as the heat source would eliminate the need for fuel combustion and would completely eliminate carbon dioxide emissions.

5. Vortex Producers using warm humid air as the heat source. The heat content of warm humid air is often more than sufficient to sustain a vortex. Such vortices could be used to produce energy, to break inversions, to raise polluted air, or just to reduce surface temperatures.

7.7 What heat sources could be used for an AVE?

Since the AVE is able to transfer ground-level heat up and reject it to the much colder upper atmosphere (-60 °C), it becomes feasible to use existing low-temperature heat sources and extract additional energy from them. For example, the figure below from the US DOE visually illustrates the magnitude of waste heat sources from existing thermal power plants in the US.  All thermal power plants must reject this heat to the atmosphere via cooling towers or once-through cooling to rivers or lakes.  All of the waste heat could potentially become a fuel source for the AVE.

DOE Higher resolution version of the above figure - PNG (707 KB) In addition to sources of waste from existing thermal power plants or other industrial sources, there are also numerous sources of natural waste heat which can be used to power an AVE.  For example, the warm humid air heated by the sun at the surface of the earth.  The heat content of tropical ocean waters is also another enormous reservoir of potential energy.  Warm tropical ocean water at 26 °C or greater would also be sufficient to act as fuel for an AVE.  The amount of energy stored in warm tropical ocean waters is illustrated in the figure below.
earth energy resources Higher resolution version of the above figure - PNG (409 KB)

The heat to sustain the vortex once established can be the natural heat content of the warm humid air or can be provided in heat exchangers located upstream of the deflectors. The heat exchangers can be wet cooling towers or dry finned heat exchanger tubes. The continuous heat source for the peripheral heat exchangers can be waste industrial heat or warm seawater. There are times and locations where the heat content of ambient air would be sufficient to sustain a vortex without the peripheral heat exchanger.

7.8 What are the byproducts of the AVE?

In addition to producing electrical energy, the AVE process has several other useful functions

  • Production of clouds
  • Production of precipitation
  • Production of fresh water
  • Enhancement of cooling tower performance
  • Elevation of polluted surface air
  • Environmental cooling

The quantity of precipitation produced by an AVE would be small compared to the precipitation produced in natural storms. The 20000 t/d of precipitation produced by a 200 MW vortex power station would produce a rainfall of 2 mm/d when spread over an area of 10 km2. The horizontal extent of the cloud cover in the downwind direction could be 20 kilometers or more. The area of active convection would be under one square kilometer. 

7.9 How can the AVE increase the electrical capacity of a thermal power plant without requiring more fuel?

An AVE can increase the power capacity of a thermal power plant by reducing the cold sink temperature from the temperature at the bottom of the atmosphere which is approximately 30°C to the temperature at the top of the troposphere which is -60°C. Decreasing the temperature of the cold sink of a Carnot engine from +30°C to -60°C can significantly increase the overall efficiency.

An atmospheric vortex engine could increase the electrical output of a 500 MW plant to approximately 700 MW by converting 20% of its 1000 MW of waste heat to work thereby increasing the overall output of the power plant by close to 40%.

Refer to the following diagram for an example using typical values from a coal-fired power plant:

carnot heat engine High resolution version of the above figure - PNG 323 KB 7.10 How much energy will the AVE process produce?

Depending on the size, an AVE could generate 50 to 500 MW of electrical power. The cylindrical wall could have a diameter of 200 m and a height of 100 m; the vortex could be 50 m in diameter at its base and extend up to the tropopause.

The energy production potential of the AVE far exceeds that of all other energy production processes. The major advantage over other solar energy technologies is that the solar heat collector can be the earth's surface in its unaltered natural state. Conventional solar thermal power plant require enormous solar collectors and their working fluid has to be heated to a temperature significantly higher than ambient temperature. All thermal power plants require heat source significantly higher than the temperature of the bottom of the atmosphere because they use the bottom of the atmosphere as their heat sink. The AVE can use heat sources close to the temperature at the bottom of the atmosphere because the cold sink is the much colder upper troposphere.

The total energy produced by humans is 15 TW of which 2 TW is electrical power. The total solar energy intercepted by the earth is 174,000 TW. The thermal energy carried upward by convection at the bottom of the atmosphere is 52,000 TW. Converting just 12% of this heat to work would produce 6,000 TW of electrical energy which is 3000 times more than all the electrical energy presently produced.  

energy production potential High resolution version of the above figure - PNG 336 KB

Supplying the energy needs of a city with conventional solar plants would require a solar energy collector area of 10 to 100 times the area of the city. Supplying the energy needs of Ontario from conventional solar energy could require all the farm land in Ontario. Conventional solar heat collectors make the land unavailable for farming. The solar collector in the vortex engine is the earth's surface in its unaltered state; there is no need to change the way the land is used. The Earth's surface in its natural state heats the boundary layer of air near the bottom of the atmosphere.

In the Tropical Cyclone FAQ, Christopher Landsea estimates that the heat carried upward by convection in an average hurricane is 600 TW which is equivalent to 200 times the total world electrical generating capacity of 3 TW. He estimates the wind energy produced in an average hurricane at 1.5 TW which is equivalent to about half of the world wide electrical generating capacity. Landsea estimates the upward heat flow from the latent heat released by the condensation of precipitation as well as the wind energy produced from the energy required to overcome friction. Landsea also estimates the heat to wind conversion efficiency to be 1 in 400 or 0.25%.

Kerry Emanuel estimated the heat to work conversion efficiency of hurricanes to be up to 33% based on Carnot efficiency and on the temperature at which heat is received and given up. See: Emanuel, K. A., 2005: Divine Wind: The History and Science of Hurricanes. Oxford Univ. Press, New York, 304 pp. - Chapter 10 Nature's Steam Engine; and Hurricanes: Tempests in a Greenhouse

Emanuel (33%) calculates the mechanical produced for a reversible process. Landsea (0.25%) calculates the wind energy actually produced. The reason for the over 100 fold inconsistency is that the energy actually produced is much less than the reversible process work because the expansion process is not constrained. When an expansion process is unconstrained work reverts to heat. See: Van Ness - Understanding Thermodynamics

The mechanical energy production potential of a single large hurricane can exceed the total mechanical produced by humans in a whole year. The mechanical energy produced in a large tornado can exceed the electrical output of a large electrical power station.

7.11 What is the net impact of an AVE on global warming?

The vortex engine can help to alleviate global warming in several ways.

1. The vortex engine increases the quantity of electrical energy produced by thermal power plants without increasing fuel consumption thereby permitting a reduction in the quantity of fuel required to meet human power needs.

2. A vortex engine causes upward heat convection in the troposphere to take place slightly earlier than it would without vortex assistance thereby reducing the temperature at the bottom of the atmosphere. The vortex moves the heat higher up in the atmosphere permitting it to be radiated to space with less interference from greenhouse gases.

3. A vortex engine whose heat source is either warm sea water or warm humid air produces power without requiring the combustion of fuel except for startup.

7.12 Why will the base of vortex stay in the center of the vortex station?

The energy source is the buoyancy of the rising air. Solar radiation heats the earth's surface and the earth's surface in turn heats the air via sensible and latent heating. This heating gives air originally from near the surface of the earth the ability to become buoyant when it rises through ambient air. Convection is a one way street. Surface air has the potential of becoming positively buoyant and thereby to continue accelerating upward. Air from higher up in the troposphere does not usually have the potential of becoming negatively buoyant. Descending air tends to get warmer than the air through which it descends thereby becoming positively buoyant. Potential temperature normally increases in the upward direction which means that air descending from the upper of the troposphere becomes warmer than the ambient air. The descending air becomes positively buoyant which stops its downward motion.

An exception to the above stability relating to downward motion is when the parcel is cooled by evaporation. Spraying water in dry air can reduce its temperature by up to 5 °C. Evaporatively cooled downdrafts are often associated with thunderstorms. The production of strong downdrafts requires the presence of liquid water for which the source must be the condensation of water in updrafts. Downdrafts are therefore a secondary phenomenon; there must first be an updraft to produce the liquid water.

7.13 Tornadoes have been observed to descend from clouds. Is there is danger that the vortex will descend outside the vortex producing station? I have read that the energy produced in the clouds is concentrated and transmitted to the ground.

Tornadoes do not come down from above. The energy of tornadoes is the result of the buoyancy of air that originates at the bottom of the atmosphere. The descending funnel is the result of the condensation level coming down as the pressure within the vortex decreases. The flow in the cylindrical wall of a tornado is upward. There may be a minor downward flow on the axis, but this downward flow is small compared to the upward flow. It is the upward flow that produces the energy. Tornadoes do not descend; there is no danger of a tornado coming down from above. Tornadoes are caused by the rising of buoyant surface air. The pressure reduction in a tornado results from the buoyancy of the air that has risen previously in the tornado. Tornadoes do not concentrate the turbulent energy of turbulent clouds and channel it down. It is true that the mechanical energy is produced aloft, but only as a result of the buoyancy of the immediately preceding air which has originated near the surface.

7.14 Is there a chance that the vortex will jump out of the station and cause destruction in the surrounding area? Why would the base of a vortex 15 km high stay in the center of the vortex producer?

Producing the vortex requires both warm air and that this air rotate about the vertical axis. Sources of warm air are very common, but convective vortices are rare. Surface temperature under conditions favorable for dust devils can be up to 70°C. The air at the 10 cm level close to the ground can be 20°C warmer than the air at the 10 m level. Large energy parks reject over 5 GW of heat via cooling towers; there have been no incidents of energy parks triggering tornadoes or even large thunderstorms. Convective clouds similar to fair weather cumulus are occasionally observed above cooling towers. Large fires (city fires, forest fires, oil tank farm fires, agricultural stubble fires and volcanoes) have occasionally started fire whirls; some of these fire whirls traveled away from the heat source and turned into tornadoes.See:

The rarity of tornadoes is more due to the lack of rotation than to the lack of heat. It is very common for the air near the bottom of the atmosphere to have sufficient heat content to support a tornado, however, producing organized rotation is a rare occurrence. Getting a convective vortex going can be helped by providing a supplemental temporary starting heat source.

The source of the rotation of tornadoes is usually the random rotation of air mass within which the updraft forms. Convergence of air rotating at the speed of the earths' surface plays a major role in hurricane and a minor role in tornadoes. Hurricanes always have cyclonic rotation. Tornadoes occasionally have anti-cyclonic rotation. The direction of rotation in the vortex engine depends on the geometry of the tangential air entry ducts and can be either cyclonic or anti-cyclonic.

7.15 Will horizontal wind will blow away and destroy the vortex?

There is a possibility that horizontal wind will destroy the vortex or reduce its height. We will not know with certainty how much wind a large vortex can withstand without a full size demonstration. What is known is that it is possible to produce a small thermal vortex in a sheltered building.  During experiments it was possible to blow away the upper part of a small vortex but the base of the vortex always remained in the center of the vortex producer. Large vortices should withstand horizontal wind better than small ones. In many cases natural tornadoes rise virtually straight up in spite of the fact that there is wind shear. The base of a natural tornado tends to move with the prevailing wind. A vortex with an anchored base may be more adversely affected by horizontal wind than a natural tornado whose base is free to move with the prevailing wind.

A tornado is a rising column of air warmer than the surrounding ambient air or of air that has the potential of becoming of becoming warmer thatn the ambient air if raised. A tornado is like warm flue gas rising in a natural draft chimney; the buoyancy of the rising air produces draft at the base of the chimney. What would happen if a chimney were neatly cut in two and the upper haft moved horizontally to the side? In the lower haft, the draft would be reduced by about half because of reduced chimney height; upward flow would continue at a slightly lower velocity. In the upper haft of the chimeny the flow would continue for a short time until the chimney fills with cool air at which point the upward flow would stop. Air at high elevation is dryer and cooler than surface air and is unable to remain buoyant when raised.   

7.16 How will the vortex be prevented from getting too large, from getting away or from wrecking the station?

The primary devices for controlling vortex intensity will be adjustable flow restrictors. These adjustable restrictors would be similar to widely used air dampers. There would be remotely adjustable air dampers in the tangential air entries. For safety there could be redundant remotely adjustable air dampers upstream of the heat exchanger. The air dampers provide two means of completely shutting off the air inlet to the vortex producer thereby stopping the vortex.

The vortex could not jump out of the cylindrical wall and reform outside the station because the air outside the station is not heated, has no buoyancy and has no source of rotation. The probability of a vortex re-forming outside the station would be lower than the probability of a natural tornado forming in the some distance away because the AVE draws warm surface from its immediate area and would make the area next to the station less suitable for supporting a natural tornado than surface air far away.

7.17 The efficiency of the the solar chimney is low. The overall efficiency of the Manzanares solar was approximately 0.2%. How can such a low efficiency process be advantageous?

Using fuel to produce the low temperature heat required by the AVE would be wasteful but using natural heat sources whose temperature is too low a temperature for other use is not wasteful. There are many naturally available waste heat source that are at too low a temperature to be used in conventional engines. The reason why low temperature heat sources cannot be used in conventional engines is that the cold source is the the temperature at the bottom of the atmosphere. By using the using the much lower temperature cold source at the top of the troposphere, the AVE renders the use of low temperature heat sources possible.

7.18 What is the relationship between the height of the solar chimney and the height of the vortex in an AVE and the air temperature at their bases?

The heights of the Manzanares "Solar Chimeny" which operated in Spain for 7 years in the 1980's, of the proposed Australian "Solar Tower" and of the proposed Atmospheric Vortex Engine are compared in the figure below.

height comparison High resolution version of the above figure - PNG 548 KB

The Manzanares solar chimney produced 50 kW of electrical energy with a chimney 200 m high by raising air heated to 20°C above the surrounding ambient air. The same 50 kW of energy could be produced with a chimney 2 km high and air heated by 2°C, or with a chimney 10 km high and air heated by 0.4°C. Friction losses in the Manzanares solar chimney were less than 10%; increasing the chimney diameter from 10 m to 12 m would be sufficient to keep the friction losses from increasing. The draft or pressure differential at the base of the chimney is proportional to the horizontal temperature difference and to the height of the chimney. The higher the chimney the lower the temperature of the air has to be to produce the same presure differential and the same electrical energy. Increasing the height of the chimney can completely eliminate the need for the solar collector.

The AVE replaces the physical chimney with centrifugal force in a vortex. The AVE eliminates the need for solar heat collector by using natural heat sources such as solar energy or waste heat. The greater height of the AVE allows the use of lower temperature heat sources. With sufficient vortex height, warm and humid surface air can become an adequate heat source. There is no need for solar heat collector; the heat source can be warm sea water. The heat can be transfered to the air in dry or wet heat exchangers.

Link to Solar Chimney Operating Condition Table

There is an abundance of air 2°C warmer than the ambient temperature. The temperature of dry sand or asphalt during periods of insolation can be higher than 70°C; the temperature of the air in the bottom 30 cm of the atmosphere is often 5 to 10°C warmer than the air at the 10 m level. The temperature of the air immediately above sandy or rocky soil can be 5°C warmer than the temperature of the air above adjacent damp soil or water.

The 4000-fold power increase in power output between the Manzanares solar chimney and the proposed Australian solar tower results from increasing chimney height by a factor of 5, from increasing the collector and chimney area by a factor of 700, and from the fact that kinetic energy losses are a smaller fraction of the total energy production. Energy calculations for the two solar chimneys are shown in the above table.

The following table shows AVE energy calculations for air with a range of approaches to Sea Surface Temperature (SST). The effect of increasing the moisture content of the air on work production is similar to the effect of increasing the air temperature. Increasing the relative humidity of the air by 3% is equivalent to of increasing the air temperature by 2°C. The humidity of air can easily be increased by spraying water in the air in a cooling tower.

Link to AVE Energy Calculation Table for 30.4 SST

The fact that air can hold more water at reduced pressure further increases the effect of heating with water. In Case 4 of the Table the work is increased to 25770 kJ/kg by saturating the air with water at 30.4°C. Producing the same 25770 kJ/kg by heating the air upstream of the turbine in state 1 would require that the air be heated to 38°C. Water at 30.4°C can be as effective as sensible heat at 38°C!

The heat content of the tropical surface water is enormous. An hurricane can reduce sea surface temperature by 3 to 5°C to a depth of 100 m along a path 100 km wide. Both hurricanes and waterspouts increase the heat content of surface air by spraying water droplets in the air. The heat drawn from the ocean to sustain a waterspout size vortex would be negligible; there is essentially an inexhaustible supply of heat in the upper tropical ocean layers.

Both of the above tables are based on the following manuscript wherein the calculation basis is explained.

Link to the technical description of the AVE

7.19 Could a vortex engine operate using ambient air without a heat exchanger or a heat source?

YES. The air in the boundary layer close to the earth's surface often has enough heat content (temperature) or moisture content (mixing ratio) to become buoyant when raised. The ability to produce work is called Convective Available Potential Energy (CAPE). CAPE is routinely calculated for every atmospheric sounding. CAPE is measured in Joules per kilogram (J/kg).

The CAPE of maritime tropical air is typically between 800 and 1800 J/kg. The CAPE of continental air during periods of heavy insolation can be as high as 5000 J/kg. The CAPE of continental air that has been cooled by radiation early in the morning is usually negative. A CAPE of 1000 J/kg coresponds to a velocity of 45 m/s; a CAPE of 5000 J/kg corresponds to a velocity of 100 m/s.

Increasing the heat content of surface air by increasing either its temperature or its mixing ratio increases CAPE. The heating of the atmosphere from the bottom by solar radiation tends to increase CAPE. Upward heat convection tends to reduce CAPE and restore stability. Sensible and latent heating both increase CAPE by approximately 30% of the heat addition. Increasing the temperature of surface air by 20°C increases CAPE by approximately 6000 J/kg; increasing the realtive humidity of surface air at 30°C from 70% to 100% increases CAPE by 6000 J/kg. Spraying warm sea water in air would increase its CAPE by increasing its relative humidity.

Surface air can become buoyant as soon as it is lifted (unconditional instability). Sometimes the surface air has to be lifted several kilometers before becoming buoyant (conditional instability).

Fair weather cumulus are evidence that there is enough CAPE to produce convection. Fair weather cumulus quickly lose their buoyancy once the condensation level is reached because evaportive cooling occurs when condensed water mixes with the overlying dry air causing loss of buoyancy. The mixing of dry ambient air with buoyant rising air containing condensed water is the reason why fair weather cumulus remain shallow.

Standard CAPE calculations tend to underestimate available energy because the calculations are based on the average property of the bottom 500 m of the atmosphere rather than on surface air. Atmospheric soundings for Eastern America tend to underestimate CAPE because the soundings are taken at 0600 and 1800 local time.

The heat content of surface air during periods of high insolation and high air conditioning loads should be sufficient to operate atmospheric vortex engines.


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