H. A Mountain Slope Solar Chimney

Heat rises in a chimney. A solar updraft chimney typically has a way to generate solar heat and a wind turbine within the chimney. Solar-heated air rises up the chimney and turns the wind turbine.

My mountain slope solar updraft chimney (as opposed to a tower) is an odd bird. It has a number of diverse climate purposes that often it accomplishes simultaneously. It can protect the local ecology from the ravages of megadrought while generating fresh water, while restoring a mountain glacier, while producing dispatchable electricity and while removing greenhouse gases from the planet's atmosphere. I'm choosing to file this invention under "renewable electricity generation" as a matter of convenience.

H1. The Manzanares updraft tower prototype

My inspiration was the Manzanares solar chimney, which started producing electricity in 1982. In Manzanares, Spain, 1982-1987, a chimney (an updraft tower) ten meters (33 feet) in diameter and 195 meters (640 feet) tall was erected. 46 hectares (110 acres) of clear vinyl plastic generated heated air around the base of the updraft tower. Once started, the heated air rising up the updraft tower continually drew more heated air into the updraft tower's base. A 50 kilowatt wind turbine in the updraft tower would generate steady electricity during every sunny hour.

The air, as it rose up the chimney, created a draft. A wind turbine in the chimney generated 50 kilowatts every sunny day at a price of about 25 cents per kilowatt-hour. The picture below shows the 600 foot tall chimney and the many plastic sheets mounted ten feet above ground level . The wind turbine is inside the base of the chimney.

Klinkman Solar Design’s mountain solar chimney, U.S. patent #8,823,197, was granted on September 2, 2014. I'm letting my solar patents lapse.

The Manzanares prototype illustrates both the potential and the hard realities of renewable energy experimentation. Building the prototype proved the general concept of generating electricity with a draw of relatively hot air up a updraft tower. Moreover, the prototype worked faithfully for seven years with only one constantly moving part, the wind turbine's rotor, and the wind turbine would always see a constant wind from one direction. On the other hand the experiment never came within a mile of being profitable. Further, only 1/2 of 1 percent of the solar heat rising up the updraft tower's chimney was turned into electricity. The experiment's expensive land wasn't being used with any energy-efficiency.

To be competitive the system requires inexpensive solar heated air, a far better ratio of heat collection to electricity generation and low construction costs for a solar chimney to be cost-efficient. I want to focus on these issues one by one. In brief, heating the air should happen right at ground level to save money, a greater altitude change improves power conversion and laying a chimney diagonally up a mountain slope saves construction costs.

H2. Net change in elevation

The taller the chimney, the stronger the draft. The elevation change of a vertical updraft tower is linearly related or better to the percentage of solar heat converted to electricity within the updraft tower. Modern tower experimenters have been thinking in terms of extremely tall updraft towers with kilometers of elevation change. Unfortunately, building any structure to that height will be wildly expensive. Also, a vertical updraft tower is an aviation hazard.

Wood stove chimneys can be built with horizontal sections, so chimneys don't have to be always vertical. A chimney laid diagonally onto a mountain slope will be no more of an aviation hazard than was the original mountain. The costs of construction and maintenance drop by orders of magnitude. I could possibly set up a canvas and bamboo pole chimney by myself.

The Manzanares chimney has recently been renamed an "updraft tower". A mountain slope updraft tower without any tower part would properly be called an updraft chimney.

H3. Internal air drag

The Manzanares prototype used 110 acres of heavy vinyl plastic supported on ten foot poles with guy wire support to facilitate natural airflow underneath the plastic. Their design may have had important air friction losses at the chimney's base where a fast-moving 3 meter wall of air approaching from all sides made a 90 degree turn, but air friction within the slow-moving air at the outer edge of the solar heat array was negligible. Always remember a fundamental principle: air friction is related to wind speed at least to the second power, and perhaps higher when air streams have to negotiate multiple twists and turns. The slower the local air movement, the lower the total system air friction.

I may always have limiting surface drag problems with the inside skin of the main updraft chimney and with teardrop-shaped support poles and guy wires within the chimney, but the gathering and storing of solar heat can be widely dispersed such that when I measure wind velocity at laminar flow velocities, measured in centimeters per second, aggregate air friction becomes negligible.

H4. Preheating air in stages

A smog inversion creates hotter surface air. The chimney can benefit from any amount of additional daytime heat. Sucking some of the solar-heated air inversion out of a valley lowers the aggregate cost of air-conditioning the valley, creating bonus negawatts. Also, unbreathable smog particles are subtracted from people's breathing air. A smog inversion exporting mountain slope solar chimney was patented in 1996.

Wikipedia lists gathering heat as the updraft tower's major cost. I spread an amazingly inexpensive solar air collection surface over the ground for my initial air warming task.

Warmer air can be generated under a laminar flow scheme. Outside air is gently pulled downward from the outside environment, transpired through a hexagonal lattice of inverted recycled glass jars. The top surface of 1” to 2” rocks directly below the surface of this array of glass jars can be painted solar black for better solar heat absorption. Even if some convective heat heats the air within 1 millimeter of this surface of glass jars, that warmed air will often get transpired back down into the collector. A tight racking of glass jars should stand up to hurricane-force winds. I expect that no weeds will grow on this bone-dry, soil-free and seriously warm solar collector surface. The jars' surface temperature should be half-bearable when, someday, kids step barefoot onto the racks of overturned glass jars. I can generate my own low-temperature solar heat at a surprisingly low cost per therm of heat.

This heated air will then percolate down through the rocks and eventually into larger air channels. In doing so, sunny day air will give up much of its newfound heat to the rocks. Cold night air percolating down through those rocks will be heated.

This heating process in turn can heat the subsoil directly under the solar heat-collecting area. The ground can hold heat to a great depth. Heat stored deep in arid ground tends to rise, and so some of this deeply stored heat may be available at night even after a cloudy day. The beauty of stored heat is the ability to run the chimney at times of peak electricity demand. Storage solves my society's most fundamental renewable electricity generating problem.

An uncommon rain event can drain away this deeply stored heat. However, it's possible to build a rock bed with heat-tolerant rubber or fabric that collects most of the water into specific channels designed to drain most of the water away from the solar heat collecting and storage field when a thundershower hits.

Heating air or heating anything is a progressive process. Heating something 10 degrees Celsius is ten percent of the job of heating something 100 degrees C, and it's always the easy part of the job because thermal heat losses are lower at first. Therefore, engineers should always think in terms of heating anything, air, water or rock beds, in stages. In this case the solar heating of a glass jar-covered rock bed on the ground captures and stores my initial 10 to 20 degrees Celsius of heat at a rock-bottom price.

The system can also profitably use passive heat collectors and heat storage banks such as parking lots. Pipes underneath parking lots can preheat air. I can use smokestack heat. I can gain from any low temperature input hot air.

For a second heating stage air collection tunnels can be insulated, with concentrated sunlight sent into them. Small subset streams of the air stream within a collection tunnel can be rotated through 1” to 2” rocks on the bottom of the tunnel to store higher heat inexpensively.

A team of European researchers reports, “Nitrous oxide could be removed from the atmosphere with simultaneous generation of renewable energy.” If a stream of air is passed over a catalyst in the presence of concentrated solar heat, the long-lived greenhouse gas and pollutant NO2 will be decomposed into common O2 and N2. A high temperature, high-sunlight spot within a solar updraft chimney would be a prime place for an NO2 catalytic converter. The decomposition of any atmospheric methane or other hydrocarbon gas molecules would also be welcomed.

[[https://ec.europa.eu/environment/integration/research/newsalert/pdf/nitrous_oxide_removed_atmosphere_generation_renewable_energy_476na3_en.pdf Ming, T., de Richter, R., Shen, S. & Caillol, pdf file: Nitrous oxide could be removed from the atmosphere with simultaneous generation of renewable energy]]

Final heating should probably take place as close to the vertical start of the chimney as possible, to minimize heat losses. Geothermal heat storage, already described, is an answer for the final heating of dry air. I can reflect a wall of concentrated solar heat into a geothermal storage area in the ground directly below the low end of the chimney. The hotter the air, the more electricity is generated within the same chimney.

All parts of the solar chimney have to be rated to handle a certain maximum temperature. Temperature-sensitive failsafe systems need to trigger in order to cost-efficiently run the chimney near its maximum rated temperature.

H5. Air tube construction axioms

The same construction axioms for J1. Huge buildings that only enclose air also apply to large-diameter air tubes, with the understanding that all support pillars and all guy wires need to be streamlined in the direction of air flow. A support pillar can look like an airplane wing, with a narrow bulbous front and a back end tapered to a point. A stronger box-shaped aerodynamic support pillar can have remarkably thin diagonal cross-braces connecting two remarkably thin posts, with the cross-braces tilted to exactly match the direction of airflow. The guy wires can be bands, but they must not vibrate back and forth in the steady wind flow inside the air tunnel.

As elevation changes, the volume of the same amount of air rising within the same air tube changes. Also, air friction changes with air pressure and any precipitation within the tube reduces the total number of gas molecules rising within the tube.

H6. Exhausting smog from a valley

This image is of Charleston Peak as seen from Pahrump, Nevada near Las Vegas. This chimney rises from a 4,000 foot elevation to a 12,000 foot elevation.

Southern California's Inland Valley has a smog problem. People can die early of asthma. Southern California's extreme dependence on the gasoline-powered automobile leads to NO2 emissions, and the sun creates smog particles from NO2 and from evaporated hydrocarbon molecules. The smog tends to form within an inversion, a hot, brown smoggy layer close to the ground.

Mountain solar chimneys can feed on the latent heat found in hot, smoggy inland valleys. On a large scale, a chimney can displace a great quantity of such air out of the valley, lowering the valley's aggregate afternoon air conditioning costs.

If a percentage of the unnaturally hot smoggy air trapped on the surface of the Inland Valley can be encouraged to rise up the chimney, then the smoggy air can continue to pull itself thousands of feet up the chimney, not to be breathed again by asthmatic Southern Californians. Inland Valley air is particularly rich in NO2, and so catalyzing the NO2 out of the chimney's airstream would be particularly useful in Southern California.

Urban Southern California is starting to grow up the sides of its nearby mountains, so it might be hard to locate a spot for a smog updraft chimney. However, a chimney might rise from the edge of Riverside, California, elevation 2000 feet, up to a subsidiary peak near Cucamonga peak, elevation 8800 feet.

In the daytime, smoggy air gets pulled into the updraft tower's solar-heating area and then the hot air rises up the updraft tower. The town of Riverside gets just a bit cooler and less smoggy. After dark the outside air gets cold but the relative heat stored within the solar-heating area keeps the smog pumper going. Riverside gets a nicer reputation. What's not to like?

H7. Midday chimney updrafts versus sunset and nighttime updrafts

One notable benefit of storing heat in the desert is that temperatures can drop by 20 degrees Celsius from day to night. This means that I accrue 20 degrees Celsius of free power when I send heat collected in the daytime up the chimney at night, when the cold night air is relatively heavier than the daytime air.

A chimney's uplift, or a hot air balloon's uplift for that matter, is based on calculating the mass for a volume of hot air inside the hot air balloon versus the mass for a volume of outside-temperature air that the hot air has displaced. 29 grams (1 standard mole) of hot air at a normal air pressure occupies more cubic meters of volume than 29 grams of cold air occupies. Conversely, a cubic meter of hot air has less mass than a cubic meter of cold air. The hotter the air in the balloon, the less mass of air within the hot air balloon's volume and the more uplift the balloon has.

In a full-sized 30 meter diameter hot air balloon the subtracted grams start adding up to kilograms. When a balloon holds 200 kilograms less air mass than an equivalent amount of outside atmosphere and if two people in the balloon's basket plus the balloon's own mass equals a total of 190 kilograms, that balloon is heading upward as soon as somebody unties a tether rope.

Now, the point: given equal supplies of air of the same temperature, a chimney will generate notably more uplift late at night because the outside air temperature usually drops at night, especially in arid climates. Colder air takes up less volume per mole of air molecules, and so each cubic meter of outside colder air has more mass compared to the mass of each cubic meter of hot air within the chimney. So, saving heat in rocks for nighttime use can possibly earn us an updraft bonus. I can get extra usable power going up the updraft tower at night for the same solar heat input. Above is a sun to rocks to air insulated thermal transfer system with concentrated sunlight coming in the sides, a stream of cooler air coming in the bottom and a stream of hotter air going out the top.

It's worth remembering that direct photovoltaic power drops to nearly zero about an hour before sunset, but everyone still wants to run their air conditioners in the early evening. Perhaps heat storage has advantages in my quest for 100% coverage of electric demand.

H8. Chimney construction techniques

For the most part a small diameter chimney is a Quonset hut shape, a semicircle hugging the mountain. If the Quonset hut is slightly less than a 180 degree semicircle, lateral winds hitting the chimney are a bit more likely to spill over the top of the chimney. For this reason an outside wind-turning shell on both sides of the chimney, slanting from the roof of the chimney out to the ground, is designed to reduce lateral wind over-pressures on the sides of the chimney. The slanted wind shell turns the lateral wind over-pressure upward so that lateral wind gusts don't affect any of the inner layers.

If the chimney needs to leap a road, a ravine or a nature trail, the chimney can become a full circle.

Curves in the chimney can cause air turbulence. One friction-reducing tactic is to temporarily increase the width and/or the height of the chimney near the curve, so as to slow down the relative airflow near the curve.

A perfectly smooth floor reduces air friction. This will involve grading equipment.

Finding an optimal low air friction route up a mountain for a chimney is a compromise between building as straight a chimney as possible to the summit, building as short a chimney as possible by going up steep slopes and saving money by conforming to the slope of the mountain.

I picture one wind turbine inside the chimney for, say, every 100 meters of vertical elevation change. Each wind turbine in the chimney benefits from a cowling that focuses the chimney's total volume of rising air through a temporarily smaller pipe, increasing the local wind speed for the benefit of the wind turbine.

In-chimney wind turbines will be less expensive to construct than outside wind turbines. Wind velocities within the chimney should be well-controlled and strengthened by cowlings that focus the airflow through the turbine blades. Nothing remotely resembling a hurricane-force wind gust should ever stress the turbines inside the chimney. The turbine blades can be relatively optimized for one maximum wind velocity. The hazards of snow and ice will never be seen in the chimney. The updraft always blows through the cowling from the same direction.

My string of turbines will need a single power line. I don’t have a photovoltaic farm’s electrical spaghetti problem.

Twice the chimney width yields 4 times the cross-section, so that chimney cost savings at scale are possible,

The inside of the chimney can contain internal support posts. For now I'll assume that the chimney is 30 meters tall and 30 meters wide. I see two rows of teardrop-shaped 30 meter tall support posts running up the middle of the chimney. Internal guy wires linked to the vertical support posts at 10 meter intervals will help handle various wind loads against the outside of the chimney.

Two earth berms can define the left and right edges of the chimney's outer skin. They would slightly reduce the chimney's outer skin, the berm's weight would help to anchor the chimney's pressure-maintaining layer to the ground and the berm would absorb a bit of the lateral forces on the chimney caused by hurricane-force lateral wind gusts.

My chimney is a good neighbor. Traditional wind turbines can produce flicker, noise and bird strikes, but our air turbine is fully enclosed and can be soundproofed. I can partially hide our chimney under trellises of vines. I can also camouflage its outer layer to blend in with the terrain as seen from a great distance.

My chimney should be reasonably compatibile with local activities such as hiking and hunting on the mountain. My air chimney is able to traverse gullies and leap over highways, leaving migration channels for wildlife and paths for hikers.

I assume that I wouldn't have access to the mountain's peak itself, which has notable natural beauty, but that I would be allowed to use a lesser promontory for discreet solar energy generation.

If the chimney is shot up with several hunters' bullets, it should continue generating electricity with 99.9% of its original power output.

The solar chimney should create little or no additional fire danger to the area, except where fallen electric power lines might create sparks in tinder brush.

I can plan for far better durability and for far lower lifetime maintenance than most power companies are accustomed to seeing. Hydropower dams can eventually fail. Photovoltaic panels degrade in twenty years. I might just keep running.

H9. Chimney wall layers

The chimney's outside shell must shed precipitation and handle wind loads. The outer shell is painted so that the view from downtown Riverside, where people are most likely to see the chimney, closely resembles what someone would have seen before the chimney was erected.

Inside, a fairing layer improves airflow up the chimney. The chimney's walls should be straight in the direction of airflow in order to minimize turbulence. Reducing any drag against the walls will be helpful.

Between the fairing layer and the outside shell is an air pressure maintenance layer of rubber suspended between support cables. Even with turbines scattered up and down the chimney, differences in outside versus inside air pressure will occur. A rubber chimney section may be under considerable positive or negative air pressure, which creates regular outward or inward bulges in its pressure layer, but a fairing layer on the chimney's inside can still insure a smooth air flow.

Often a layer of insulation comes outside of the air pressure maintenance layer but inside the weather shell. Insulation isn't that important near the top of the chimney where outside air is just about to meet inside air.

A ravine is a natural construction site for the lower part of a chimney. However, ten to twenty times a year, especially in winter, a heavy precipitation event may flood the bottom of the ravine, washing much of the inherent ground heat away. The chimney needs tear-away sections to handle a gully washer. Also, a thunderstorm may flood the rock bed and geothermal storage systems.

H10. Strong chimney walls versus weak walls

One of my example designs is a chimney rising from Pahrump, Nevada at a 800 meter elevation to the top of Charleston Peak at a 3600 meter elevation. Charleston Peak is only a bit west of electricity-hungry, water-hungry and sewage-rich Las Vegas, and at the top of Charleston Peak is a snow-deprived Nevada ski area.

Using a 2800 meter mountain might give us a factor of 14 better solar heat to electric power conversion than using a 200 meter tall vertical chimney, possibly much better, and the mountain will most likely never fall down. It's theoretically possible to have one power generation station at a 2,200 meter elevation. Here I needed to calculate at least a ballpark estimate of the air pressure head at this single power generation point.

As an inventor I sometimes only need a ballpark pressure differential. That's one defining difference between an inventor and a typical engineer. As a thought exercise, think of the speed with which a small group of chess players analyzes a chess game. The players quickly discuss positive chess moves with the best theoretical outcomes, and then they look at the best negative countermoves that the opponent can do, and then they examine positive counters, and so on. Looking two moves ahead rarely guarantees a chess victory but it helps. Similarly, an inventor looks for ideal positive outcomes, then for negative side-issues related to these positive outcomes, then for ways to fix the side issues, and so on. A ballpark calculation delivers nothing more than a theoretical outcome, but in the early going a loose but fast and effective calculation is optimal. The inventor delivers a set of guideposts to success. In the end the engineers and the accountants have to do every calculation exactly right.

So, for calculation purposes I assume that zero air goes through the tops (or the bottoms) of two parallel square vertical tubes of a standard width, say, 1 meter by 1 meter, and that the other end 1400 meters up (or down) in elevation is wide open. One tube is the control tube. The inside air of the other tube is heated and the inside air contains as high a percentage of water vapor as that temperature allows. The outside desert air is cold at night, often near-freezing. By calculating the mass of the air inside the tube and then the air pressure inside the tube from the open end to the closed end in 100 meter increments, and by also calculating the air pressure in the control tube filled with cold desert air, I can find the air pressure differential between the two tubes at the closed ends of the tubes.

Air pressure levels within the hot air chimney just below the halfway power station might be a ballpark 50 millibars (2/3 pound per square inch of positive pressure), and just above the power station the pressure might be another 50 millibars below the outside air pressure. The total head of 100 millibars could turn an air turbine, or it could alternatively push and pull a set of low air velocity air pistons similar to the pistons used in a steam locomotive. I know that having a strong head, a strong choke point, increases the available power in a hydroelectric project.

Unfortunately, the cost of building chimney walls able to handle enormous pressures might make the strong chimney wall option rather expensive. Having a chimney wall pressure of 100 millibars at the top of the chimney or at the chimney's bottom would drive up the cost of the chimney's walls even more.

For this reason, the chimney will probably be optimally affordable if I build less fortified chimney walls and have one smaller air turbine for every 100 meters of chimney rise, with an aerodynamic cowling assisting each air turbine.

H11. Hang gliding: attractive nuisance or auxiliary income stream?

The presence of a steady thermal updraft raises the possibility that hang gliding enthusiasts will take advantage of the thermal, illegally or legally. On most days, especially on winter days, the mountaintop exhaust air probably will have been cooled enough for hang gliders to use the updraft. The best solution might be to string a safety net across the top of the chimney, build a hang glider launch platform, then get signed indemnity waivers and sell lift tickets.

H12. Catalyzing NO2

Huang et al recommend using a solar updraft chimney to catalyze nitrogen dioxide, a greenhouse gas, out of the atmosphere. In the presence of a metal catalyst and given high temperatures, NO2 decays into N2 and O2. For further reading link to: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8461309/

H13. Absorbing CO2

A regenerative calcium cycle can be set up at the base of the updraft chimney. I'll assume that modules full of CaCO3 are converted into CaO and a stream of CO2 gas in a nearby vacuum chamber at around 900 degrees C. Modules are then moved, hot, into the updraft chimney. As the modules cool down to normal temperatures, that module heat goes up the chimney.

From what I'm reading, quicklime modules in the chimney seem to absorb CO2 more readily at a slightly higher air temperature. Absorbing CO2 is an exothermic reaction, which means that additional heat is released within the chimney.

A chimney with water vapor

H14. Water vapor can deliver extra updraft power

You might remember from Chemistry class that water vapor, H2O, has 18 grams per mole of molecules, 16 grams for the oxygen atom and one gram each for the two hydrogen atoms. Air is about 78% N2, 28 grams per mole, 21% O2, 32 grams per mole, and about 1% water vapor for an average of about 29 grams per mole for mixed air.

Assuming a chimney, a hot air balloon or perhaps a planet with a surface temperature of 212 degrees, each cubic meter of 100% water vapor, steam at 212 degrees F (100 degrees C), has only 18/29 as much mass as a cubic meter of air at 212 degrees F (100 degrees C). Pure water vapor happens to be quite a bit lighter than pure air. A mixture of air saturated with water vapor is in between – it has less mass than the same volume of dry air at the same temperature.

On the western Great Plains of the U.S., every other day a moist air mass from the Gulf of Mexico rubs up against a dry mass of air that just came over the Rocky Mountains. Meteorologists call this a dry front. The dry air weighs a bit more per cubic meter than the moist air. Given the extra relative mass of the dry air, gravity slides the edge of the dry front underneath the moist air and the moist air rises. As the nearly saturated moist air rises in altitude, it cools. This temperature drop causes condensation and then rain. Whenever water vapor condenses into liquid water it releases more heat, which often as not powers the rising current of moist air all the way into the stratosphere. Dry fronts have been found to be a major cause of initial thunderstorm formation on the Great Plains.

Any source of somewhat moist or humid air will be marginally useful in any chimney. Marginal geothermal warm water will work. Conventional chimney exhaust fumes contain both heat and some water vapor from combustion. Intake air pulled from local sewer systems will have some marginal water vapor. On summer days, local swamp coolers might dump water vapor into local air. As with heat, moisture can progressively be added to air.

H15. Generating electricity twice with steam

Many electricity generation stations, including plants powered by geothermally stored solar heat, run steam through electric turbines. Live steam can be a waste product, where enormous cooling towers are sometimes built to get rid of the waste heat in cooling water. What if steam was no longer a waste product? Given a mountain updraft chimney of considerable elevation change, waste steam and waste gases could be sent up the mountain chimney. As the steam cooled with elevation it would start to precipitate and that precipitation would release serious amounts of additional uplift power. I call water vapor “hurricane fuel.”

Above is an appropriate technology method of generating electricity from a chimney full of rising air uses one or more two-way piston chambers. The overpressurized air slowly pushes the piston out, and then the underpressurized air pulls the piston back, turning the crank. Below is a double action version of the same piston system. Airflow turbines and pistons will both work.

Finally, this is a 6-cylinder version, a V-6 piston arrangement.

For more details on the construction of hot water ponds: U1. Fog ponds for desalinization in arid areas

A solar pond has traditionally been a pond with a layer of oil floating on top. The sun penetrates the oil and heats the water. The oil prevents any evaporation. The pond gets hot.

One sustainable alternative to oil or a supplement to a layer of oil would be an array of hexagonal clear insulating glass floats. The floats would naturally form into a hexagonal array with almost no space between the floats. Because the floats hold air, they insulate the pond from the air. If the six hexagonal sides of each float are high enough, almost no wind can disturb the pond's surface of floats.

If the floats have alternating indentations and protrusions on their hexagonal sides, once adjacent floats are bumped together they tend to stay locked together. In time, wind pressures will force almost 100% coverage of a pond. The floats need a heavy bottom side because a flipped over float won't have the alternating indentations and protrusions in the right place.

My floats have a pyramid-like hexagonal diamond shape on top with a fresnel surface to better absorb sunlight when it comes in close to the horizon.

When a person or animal falls into the pond the hexagonal floats scatter. They won't impede the person from clambering out of the hot pond rather quickly, but they should return the pond to nearly normal coverage in reasonable time.

I recommend that a central small, rather deep solar pond be surrounded by solar hot water heating pipes.

H16. Distilled water

Especially in an aridified world, the distillation of steam into water will be a valuable by-product.

As the steam or moist heated air rises with altitude, fog droplets will form in the airstream.

Ionizing the chimney's air is recommended, as it causes small fog droplets to be attracted to each other and to the sides of the chimney. When two equal droplets are attracted to each other, the new droplet's mass is doubled and it drifts downward more quickly toward the floor of the chimney. Getting droplets of water out of the airstream as soon as possible is important for maximizing the updraft's power.

The chimney needs a gutter in its bottom to properly collect the precipitated hot water while minimizing friction with the rising air. Then the chimney needs air pressure-maintaining U-traps, similar to a bathroom sink's U-trap, in order to let streams of hot but drinkable water flow out of the chimney at various altitudes. This distilled water can be cooled and eventually sold as pure drinking water, a worthwhile commodity in many arid regions.

Fog droplets are likely to form around smog microparticles. A filter should take them out of the extracted distilled water. I prefer to filter out and then dispose of relatively small amounts of greenhouse gases and smog chemicals in the planet's air.

H17. Creating new snowpack and glaciers

At the top of the mountain the airstream exits the chimney, and with any luck the airstream maintains its integrity and continues in a stream perhaps an extra thousand meters above the mountaintop. If I send steam or water vapor up only after dark, the cloud above the mountaintop won't be seen by people living in the valleys below.

The cold night air will extract further precipitation from the rising air stream. In the cold of the night, particularly on winter nights, the precipitation will fall on the upper mountain slopes as snow.

Climate activists grieve for the loss of mountaintop glaciers with the coming of the climate emergency. The end of the glaciers means the failure of streams and rivers in summer, and the failure of agriculture downstream. Perhaps I should want to restore these same mountaintop glaciers with new, artificially enhanced mountain precipitation at night. I would at the same time be changing the albedo of the upper mountain slopes back to its traditional snow white, as things were before the climate crisis.

I see a logic as to why an updraft chimney should run on heated air during the daytime and on water vapor late at night. The heat in a lake or a tank of solar-heated near-boiling water can easily be stored for 12 hours or so. The chimney generates more snow or rain late at night than at other times. The cloud coming out of a mountaintop has an unnatural look to it, but people won't mind if they can't see the cloud at night.

Assuming prevailing westerly winds, an exit stream of warm, moist air can be split into substreams and these substreams can be released just to the west of portions of a ski run, in order to spread snow evenly onto the entire ski run.

For further reading: https://insideclimatenews.org/news/22012022/warming-trends-winterless-olympics-a-disaster-novel-shows-the-importance-of-storytelling-in-climate-conversations-and-a-new-lab-studies-parks-and-warming/

For further reading: http://www.greensocialthought.org/content/world-drought-gets-worse-cities-ration

H18. A vortex-shaped cloud

Just below the chimney's mountaintop exit a series of wind vanes should impart a spin to the rising air current. The outside edge of the exiting air current should get a light spin and the innermost part of the air current should get a somewhat more forceful spin. The National Renewable Energy Laboratory has performed experiments on creating a vortex at the top of a solar chimney. A vortex slightly decreases the air pressure within the center of an exiting airstream, but more to the point it should help to keep the rising airstream from immediately turning into turbulent eddies as it exits the chimney, so that the moist air continues to rise further into the mountain air before mixing, precipitating and dispersing. The higher the air current stays together and rises, the more additional precipitation is wrung out of the rising air.

The chimney's exit should be angled with the direction of the current prevailing wind to minimize immediate eddying.

H19. Slow piston turbines and air chimneys

Geothermally stored high heat can heat a stored pool of near-boiling water into steam at times when photovoltaic electricity isn't available, especially at night.

The steam can drive a turbine to generate electricity. Then the waste steam can be sent up a mountain slope chimney, where it will generate further electricity. Then the steam will create some distilled water on the way up the chimney, and perhaps will create snow or rain above the top of the mountain, storing fresh water as snow and changing the mountaintop's albedo.

To optimize distilled water creation I would devise some type of steam boiler that allowed salt brine to settle at the boiler's bottom. The brine would be drained out. A continuous flow seawater steam boiler is possible. In this way I could use superheated seawater or other wastewater to drive the boiler. Hot seawater can be corrosive, and so I'd need to minimize this side issue. However, the world's current multi-stage flash distillation units already deal with boiling seawater.

4,000 meter tall Charleston Peak, one possible chimney site, is only a bit west of electricity-hungry, water-hungry and sewage-rich Las Vegas, and at the top of Charleston Peak is a snow-deprived Nevada ski area.

H20. Distilling steam from brackish water versus using fresh water

I've consolidated the distilation process on the night fog page.