Equatorial Chimneys invented by Denis BonnelleEquatorial Chimney working with latent heat of vaporization
Please read this page before reading the page dealing with the Polar Chimneys also invented by Denis Bonnelle
With the exception of the Spanish prototype of Manzanares built in the 80’s (chimney 195m high), as a matter of fact for the moment no solar updraft chimney has yet been constructed, in part because of the very large start-up building costs. Financial viability of solar chimney power plants depends on construction costs. For the projects currently going on in Spain (750m high), in Australia (1000m high) and in Namibia (1500m high), the main part of the total costs (40 to 60%) comes from the greenhouse collector (7km in diameter, i.e. area of 38km2).
In his book: “Vent Artificiel: ‘Tall is beautiful’” Denis Bonnelle proposes to get rid of the collector. He invented two new solar chimneys without giant greenhouse.
For his new, “collector free chimneys”, Denis Bonnelle proposed to find other sources of air buoyancy (the air becoming lighter than the ambient one), like the latent heat of water.
As a matter of fact, starting from the solar chimney concept, the ocean upper layers can be viewed as a natural solar heat collector, hence able to provide heat for free. But this comparison requires a heat transfer from these layers to the air inside the chimney.
So, Denis Bonnelle’s idea is to take advantage of the natural global climatic machinery using the heat of the oceans to produce the air buoyancy needed inside the chimneys.
Two possibilities have been explored by him: taking advantage of water icing latent heat (near the poles) and taking advantage of water condensation latent heat (over the ocean between the tropics and the equator).
If you don’t know what latent heat is, please have a look at the end of this page.
Oceanic updraft chimneys = Equatorial Chimneys and Tropical Chimneys
Tropical oceans meteorological reactors
From equatorial till tropical latitudes, Denis Bonnelle invention consists to use the condensation of water vapour produced over the warmest oceans.
The principle of operation is as follows : air saturated with water vapour is introduced into the bottom of the chimney. During the whole process no giant collector is used, only a chimney is needed.
Despite the fact that the moist air density is lower than the density of surrounding air, since the molar mass of water vapour (H2O, 18) is smaller than the molar mass of a 79/21 mixture of nitrogen (N2, 28) and oxygen (O2, 32), this moist air is at the same temperature than ambient air and it could seem that it has no reason to go upwards. As a matter of fact, the heat used by the device is "latent", which means that it has no temperature rise effect and thus quite no buoyancy effect. But when this steam is condensed back to water, which usually occurs in uprising air flows at an altitude of some km, it increases significantly the buoyancy of the air. So, at a higher altitude inside the chimney a lot of water vapour will condensate as the temperature falls down and the latent heat released to the air upside will warm it.
Then this buoyant air will draw up and aspirate the air at the bottom of the chimney. This air, saturated with water vapour, will at his turn reach the height were water vapour condensates, and the process will go on a continuous way.
In conclusion, the uprising steam of saturated air won't be immediately buoyant with respect to the ambient air, but it will be aspired by the air over it, at the raining level inside the chimney.
A technical solution as still to be found for the evacuation of this “rain”, but, as a by-product, this type of “oceanic updraft chimney” desalinates water, and this drinking water than can be collected and stored in floating bags, that can later be towed to land by boat, to be used in cities.
Indeed, the aim of these tropical chimneys, is renewable energy production!
But also, this equatorial chimneys can significantly fight the upper layer anthropogenic dilatation of oceans
, as they will cool their surface
, transferring heat from them to the atmosphere at the top of the chimneys.
This also means than they maybe able to do hurricane prevention!
As there is a depression inside them, these oceanic updraft chimneys have many analogies with a hurricane, and the pressure difference which will exist between both sides of the turbines, is the driving force (or the motor) of the system.
It is only with a very high (3 to 5 km) and large chimney (it would have 500m bottom inner diameter), that electricity can be produced. It is easy to understand that these chimneys can not be built in concrete: they have to be much lighter, their walls need to be made of textile or soft plastic and the turbines have to be located at the top of the chimney (as in the Sorensen’s ones) in order to keep inside the chimney a pressure superior to the outside. The soft chimney must be inflated enough to prevent the outer air from pinching the inner upwards flow and the walls should not flatten or crushed.
In his book : “Vent Artificiel: ‘Tall is beautiful’” Denis Bonnelle explains the way to do so and gives answers to questions like:
How will this energy be conveyed to the continental grids?
How and with what can the turbines be maintained at the top of the chimney ?
And, would it be any environmental drawbacks ?
A possible drawback is that, in the global atmospheric circulation, the polar regions mainly receive their air from the sky, as in subtropical deserts. So, it could be prudent to study the possible impact of the relatively warm air flows sent from the chimneys up to the high atmosphere, before they're cooled down by thermal infrared emission.
Denis Bonnelle has indeed designed devices which could at the same time counteract some effects of the existing man-made CO2 excess: prevent hurricanes, produce desalted drinkable water, and prevent new CO2 emissions
by providing a large part of mankind's energy needs with renewable energy production.
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What is latent heat?
You all know that when warming water in a pan, the temperature rises progressively, and when the liquid boils, many vapour is produced, but then the temperature stays constant at the boiling point (100°C = 212°F at sea level, less in altitude). All the extra warming given is used to convert water into vapour, at constant temperature.
When heat energy is added to a liquid or solid the temperature rises. However, at the transition point between liquid and gas (the boiling point) and between solid and liquid (the melting point), extra energy is required (respectively the heat of vaporization and the heat of fusion).
In thermochemistry, latent heat is the amount of energy released or absorbed by a chemical substance during a change of state (e.g. changing from solid to liquid, or from liquid to gas), or a phase transition.
Two latent heats are typically described: latent heat of fusion (melting), and latent heat of vaporization (boiling). The names describe the direction of energy flow when changing from one phase to the next: solid → liquid → gas. The change is endothermic, i.e. the system absorbs energy, when the change is from solid to liquid to gas. It is exothermic (the process releases energy) when it is in the opposite direction.
Energy is needed to overcome the molecular forces of attraction between water particles, the process of transition from a parcel of water to a parcel of vapour requires the input of energy causing a drop in temperature in its surroundings. If the water vapour condenses back to a liquid or solid phase onto a surface, the latent energy absorbed during evaporation is released as sensible heat onto the surface.
The Specific latent heat of fusion is the amount of energy required to convert 1 kg of a substance from solid to liquid (or vice-versa) without a change in temperature. Likewise, the amount of energy required to convert 1 kg of a substance from liquid to gas (or vice-versa) without a change in temperature is known as the specific latent heat of vaporization for that substance.
For water, the specific latent heat of fusion is 334 kJ/kg (at 0°C) and the specific latent heat of vaporization is 2260 kJ/kg (at 100°C).
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