U. Night fog

The optimum use of solar distillation of water, along with other water reclaimation methods, is a complex equation. I see four uses for distillation:

1. Steam can turn electric turbines, especially when the sun isn't shining and when the wind isn't blowing.
2. Distillation produces drinking-quality fresh water for people and for irrigation.
3. Adding humidity and/or night fog to the local air is good for plant growth and it suppresses wildfires.
4. Daytime clouds (fog at high altitudes) can reduce the amount of sunlight reaching the earth.

Each region of the world, some regions more than others, is about to face a positive feedback loop of fewer mature trees leading to periods of extreme high temperatures and extreme dryness, which leads back to the death of more natural vegetation. We can water individual acres of land but we can't afford the garden hoses to artificially water all of nature.

For further reading: Increased Flooding and Droughts Linked to Climate Change Have Sent Crop Insurance Payouts Skyrocketing. https://insideclimatenews.org/news/28012022/flood-drought-crop-insurance/

We can, however, enhance night fog. When any region's temperature drops late at night to the atmosphere's dewpoint, putting additional moisture in the air translates to more fog in the air, which translates to more water on the tallest plants downwind. Creating additional night fog for a region is generally a matter of solar-heating water during the day and then exposing that hot water to cold air late at night.

For further reading: Complex Models Now Gauge the Impact of Climate Change on Global Food Production. The Results Are ‘Alarming’. https://insideclimatenews.org/news/27032022/climate-change-food-production-famine/

U1. Fog ponds for desalinization in arid areas

A solar pond is a pond in an arid area covered with a certain grade of oil. The pond heats up because water evaporation is reduced to zero, and the undisturbed water acts as a crude form of insulation from the hottest bottom of the pond to the surface.

A simple fog pond is a solar pond with a swimming pool lip, where the oil is pumped off late at night. The open water releases billows of fog into the freezing night air. The fog drifts to the shore, where fog netting catches the fresh water and directs it into cisterns. The rest of the fog blows over the fog netting and onto the nearby crops.

An array of fog ponds substantially surrrounding a swath of arid land will water the land every night, no matter which way the wind blows that night. The array should transform that swath of desert into a CO2-sequestering and food-producing region of land.

Half of the earth's land mass is becoming aridified. Its soil is holding less soil moisture. The loss of vegetation builds on itself because vegetation adds humidity to the air, vegetation keeps the ground cooler which reduces evaporation from the soil and vegetation cuts local losses of soil moisture to wind. Finally, plant roots sequester carbon. Inhibiting this process has to be part of our climate research and development effort, because humanity needs to grow food.

My desert fog pond is a small, deep, high-volume pond of solar-heated hot water, a thin solar hot water heating array laid out on the ground and large late-night evaporation pans. Seawater, sewage, agricultural wastewater or warm geothermal water will work fine. Late at night the near-boiling seawater is sprayed above or pumped into the evaporation pans. Most of the water evaporates into the cold desert air. Billows of fog are created.

Over half of the fog is captured as distilled water in nearby fog netting. The rest of the fog rolls over or through the fog netting. Usually prevailing winds will take the moisture-soaked air up mountainsides where more of the moisture will be wrung from the air as fog. Plants will capture most of the fog droplets. Some of the fog will come down on mountain tops as snow.

Evaporation ponds can produce toxic dust. They probably need roofs or enclosures for windy days. Keeping the evaporation ponds small and low to the ground means that only tiny, low-cost enclosures need be built. Evaporation ponds should be designed so that ponds full of potentially toxic dust can be emptied or swapped out. The toxic dust can be buried, or pure sea salt can be sold. Replaceable evaporation tank liners or a thin layer of sand laid down on the bottom of each tank might help with removal.

The oil version of my fog pond is a solar pond with swimming pool lips around the edges, where the oil is pumped off late at night. Billows of fog drift to the shore, where fog netting catches the fresh water and directs it into cisterns. The rest of the fog blows over the fog netting and onto the nearby crops.

Enough fog ponds, to compensate for fickle wind directions, will transform a swath of desert into a CO2-sequestering and food-producing area of land.

U1a. Parallel fog trenches

I now think in terms of separating the three processes of heating water, storing hot water and creating humidity and/or fotg. Ponds for all three tasks are cost-inefficient. For deployment of night fog or for similar uses I'd rather build parallel trenches filled with hot salty water. Trenches aren't as costly as lakes, they're easier to maintain and the ground around the trenches will stay hot all night, enhancing evaporation, if covered with a layer of tar and/or a layer of inverted glass jars. Collection of solar heat can be done in water-filled rubber tubes or in oil-filled pipes. large, flat, shallow ponds aren't cost-efficient for storing the solar heat.

U2. Fog and nearby mountains

Mountain ranges such as the Rocky Mountains tend to wring all of the excess water vapor out of air. If fog ponds put extra water vapor into late night air and that air is blown up a mountain range, almost all of the newly created water vapor will deposit itself somewhere on the mountains.

This same process can possibly help with covering a dirty ice sheet with a layer of fresh, white high-albedo snow if night fog is released on the western side of Greenland whenever the weather at the top of the ice sheet is cold enough for snow, which is most of the time. The water vapor plume will wander northeast, due east or southeast over the ice sheet as the wind takes it, and the high altitude will wring precipitation out of the vapor plume. If the plume isn't blowing in exactly the right direction on a certain night, don't release the fog that night.

Creation of nightly snow fog can help to restore a mountain range's glaciers. There's probably no reason not to deposit fresh water at a higher elevation where the water won't evaporate as quickly because of colder temperatures, and where the water can turn hydroelectric turbines as it descends.

U3. Turning Greenland's snow white again

We need to release water vapor into wind currents that travel over ice sheets. As the prevailing air current rises 3000 meters in elevation from sea level to the top of the ice sheet, most of this water vapor will be wrung out of the atmosphere and will fall as snow. It will cover Greenland's climate-induced dark layer of soot.

Large-scale solar fog-creating ponds near sea level add humidity to the local air whenever Greenland ice sheet precipitation (almost always snow) can be enhanced from February up through about June. An onshore breeze will blow added sea level humidity up and on top of the ice sheet. The altitude rise will wring the extra humidity out of the air as snow, as the air rises 3,000 meters or so. This wind-blown moisture-moving technique might also be better than nothing and an affordable tool in helping to restore certain mountain range glaciers.

We can use solar heat to put moisture into the Antarctic/Greenland air when the prevailing winds are blowing onshore, and of course when the temperature is cold enough to snow and not rain. This would be designed to enhance snowfall. We may not have the ability to restore the entire Greenland ice sheet but we can at least change Greenland's albedo. Mountain altitudes wring the additional moisture out of the air.

U4. Heat-based water desalination

Given a source of mechanical energy or a source of fossil fuel, osmosis (the process of straining water through microscopic pores) is the most energy-efficient method for directly turning seawater into drinkable water. Given an inexpensive source of stored solar heat plus cold night air, multi-stage evaporation and condensation is likely to be a better method. This option might be usable with a natural geothermal source of water vapor. Distilled water might taste slightly better than osmosis water.

Storing the coolness of late night air in the ground, well away from any geothermal heat storage system, might turn out to be cost-effective for distillation's heating and cooling process.

U4a. A Saline Clothesline

As of 11/14/24 I'm still thinking about the best ways to evaporate quantities of water from saline water.

When wet wash is placed on an outdoor clothesline the wind blows through millions of tiny holes in the laundry, between adjacent cotton threads. The beauty of the clothesline method of evaporation is that an enormous total volume of blowing dry air per hour goes past the moist threads. A flat pond surface doesn't have anywhere near this same throughput.

Some of the side issues with this type of evaporation are as follows:

- If the salt water completely dries out of the cloth, we get sea salt buildup on the cloth.

This problem is fixed by putting enough salt water on the cloth so that the residual salt water at the bottom drips off the bottom of the cloth.

- Cotton won't last that long. Bacteria will soon eat it up. We need a long-lasting cloth.

Perhaps we could weave a hydroscopic (water-holding) cloth out of glass fibers or out of aluminum wire? Smooth glass is non-hydroscopic, which means that water won't creep along the inside of a normal bundle of glass threads, as spilled water might creep into and through a cotton mop or through paper towels. Perhaps a glass thread can be coated with an outside layer of a hydroscopic substance. Two twined glass threads may create crevices along which water may creep. Would acid-etched glass threads be more hydroscopic?

Glass threads might break up into microscopic shards, but glass can over a longer term be pounded into sand by wave action. Glass is probably more biodegradable than any plastic thread, it's probably also longer lasting and it can be recycled into more glass cloth. Concentrated solar heat may help with the recycling of glass.

- If the holes between the threads are too small, a water droplet will plug that air hole and the wind won't flow through.

We need holes in the fabric netting of a sufficient width so that they never plutg up with water droplets. If needed, multiple evaporation nets can be lined up one behind the other. I would expect extremely low hurricane-force wind gust overpressures on one side of a net with overly large holes.

Optimally the netting would be woven to have hexagonally shaped holes of a certain minimum diameter. I suspect that knitters understand how to leave large sized holes in a fabric made of yarn.

- We need to refresh the moisture on our salt water laundry. We'll probably feed new moisture in from a drip irrigation pipe above the evaporation netting and let the residual salty water drip off the bottom. Dunking the cloth periodically in the water would also work.

I note that when water evaporates, the air and the remaining water becomes cooler. Evaporation is an endothermic reaction. When working with water of roughly air temperature, perhaps it's better to carry off some of the coolness remaining in the fabric's saline water.

In a chimney, warm moist air is easier to pipe long distances than hot dry air.We may want to moisten our solar-heated air at a long distance from the main pipe entrance, using far-flung saline drip cloth or saline mist at these far-flung places.

- Will anything grow on the evaporator? Not if it operates in complete darkness, not if all cellular life is filtered out of the salt water before the drip evaporator operation and especially not if the salt water is pre-heated to a boiling temperature..

The drip evaporator unit pictured above is 1 centimeter thick, to give the air passing through a bit more surface contact area. It needs a feeder pipe above the unit. The water slowly drips down the parallel ribbons and much of it evaporates. It needs a drip collector on the unit's bottom. Air will probably flow through the unit at a seriously slow velocity to minimize total energy use.

Because of biological growth on the evaporator, this might not equally work for general humidification of the atmosphere on and above land masses to reduce the local wildfire danger or to increase local night fog, for a chimney dedicated to producing pure, potable drinking water or for swamp cooling the surface of the local ocean to save a coral reef's ecology. A swamp cooler evaporates water, which is an endothermic operation that produces cooler air and cooler water droplets.

U4b. Saline mist in a chimney

A misting splash pad, seen more and more in chldren's playgrounds, sprays a fine mist of water that drifts with the breeze. Much of the water evaporates but some of the water accumulates on the concrete base of the splash pad and drains off. I note that the process of evaporation cools nearby air in the immediate vicinity of the splas pad.

Spraying saline fog within a chimney, often as not near sea level, will rather economically raise the humidity of the tunnel's air flow. Spray from pipes on top of the chimney and let the fog gradually drift down to the chimney's floor. Individual fog droplets will, in the aggregate, have an enormous collective surface area and will greatly raise the humidity of the tunnel's air.

The saline fog droplets should be calculated to be large enough at release so that a remnant of each droplet reaches the floor, taking the concentrated sea salt and residual seawater down to the floor, where it can run off back down pipes to the sea.

We can't control the humidity of the incoming air flow. However, we can have a pipe closest to the entrance to the chimney that on extra-dry days, sprays extra-large droplets that fall more quickly through the chimney's airflow to the chimney floor, Larger droplets fall faster through the airflow to the floor, and each larger droplet has a higher mass to droplet surface area ratio. This ensures that a remnant of each salty droplet reaches the floor after falling through extra-dry air. We want enough residual water in each salty droplet that we don't get any salt buildup.

Humidification of an airstream is best described as a multi-stage process. After the airstream has been humidified to, say, 80% humidity with cold seawater droplets, a fine spray of solar preheated saline water droplets can be sprayed from the chimney's ceiling. This spray will send the airstream's humidity toward 100%. We need heated saline water to approach 100% humidity in the airstream. Adding the heat to the mist never hurts, it only makes the airflow within the chimney a bit stronger and it improves the mist evaporation process.

I note a slight similarity between this saline fog process and someone else's proposal to add tiny sea salt particles to the outside atmosphere/ The salt microparticles serve as particles around which fog droplets can form in the upper atmosphere. This creates more clouds, which lowers incoming solar radiation, which cools the planet. I reserve judgment on whether this other proposal is viable or whether microscopic salt particles in the atmosphere might have costly or show-stopping side issues. I'll only say that it's easy in my chimney to spray ultrafine mist that creates microscopic airborne salt particles, which the upper end of a mountainside solar chimney would then dump into the earth's upper troposphere or stratosphere.

The airstream humidification process is typically separate from any efforts to solar-heat the airstream's air.

Seawater for air droplets is best filtered to keep plankton out of the plumbing. A typical filtering process, similar to a sewage treatment operation, might use a screen to keep out large objects such as fish, a gravity-based filtration that lets heavy objects slowly settle out of the water column and a final small-pore filter. Sewage probably should be sterilized to avoid aerosolizing any infectuous diseases that may lurk in the sewage. In certain geothermal areas I see no reason not to use geothermally warmed brine.

U4c. Adding humidity to a shoreline atmosphere

We're experiencing the loss of billions of trees right now. The Western United States is short perhaps 6 billion mature trees. We have every reason to expect a treemageddon. A vast loss of mature trees can ruin regional agriculture, and such ruin can have quite deadly planetary consequences if everyone's agriculture suffers chronic failures.

For this reason I will at least contemplate the mechanical replacement of moisture in a region's air. I recognize that the consequences of adding moisture to air haven't been fully thought through, but if nobody raises the idea, nobody will ever think it through. Breaking or at least inhibiting the regional positive feedback loops between loss of trees and drounghts is of paramount importance to humanity's survival over the next few decades.

The chief impediment to rehumidifying the entire atmosphere is the sheer size of the atmosphere versus the size of human constructions. Even a tiny, incremental rehumidification of a tiny region's air can take vast amounts of material and energy. It's preferable to use 99% renewable energy for humidification of course. Also, any rehumidification effort that uses seawater is likely to leave great amounts of heavily salted brine and/or sea salt dust particles that probably shouldn't be allowed to blow onto fertile land..

On a relatively tiny scale, humidification of the atmosphere in conjunction with a mountain slope chimney can restore a mountain glacier and/or provide potable water to a small region all summer. Or, movable offshore humidification of the atmosphere might reduce the spread of a nearby downwind megafire.

It's easiest to spray tiny salt water droplets into the air. The smaller the droplets, the more total surface area is created and the longer the droplet hangs in the air. Pipes with great numbers of tiny holes might work.

We want to pump seawater to as low a height as possible, to save (renewable) energy. If the tiny droplet spraying pipes are 5 meters (16 feet) above mean sea level, that should avoid most waves. For rare hurricanes we might pull all pipes up another 5 meters for safety. Given a hurricane, we wouldn't want or need more humidification on that day..

I'll assume an onshore trade wind of 20 kilometers per hour. If we spray directly over salt water 0.2 kilometers from mean high tide, the droplets need to be fine enough to hang in the air just long enough to fall 5 meters in about 1/100 of an hour, or 36 seconds. We want the depleted, partly dessicated salt water droplets to fall back into the sea, rarely fall onto the beach and especially not fall onto the land. We don't want salt poisoning of plants, even salt-hardy beach plants.

I've heard of researchers that want to reshape the ecology of Egypt's Sinai peninsula. As the Sinai has water on most sides, it might make sense to judiciously add moisture to the region's air.

Please be aware that as written, this proposal isn't at all connected with a geoengineering proposal to put small salt particles in the atmosphere in order to achieve cloud brightening. If my device described here were used with fine enough water droplet holes, on the lee coast of an island, with notably hot seawater, yes it would form copious numbers of microscopic salt particles at a low cost, and the moist air would create thermals to lift the salt particles well into the troposphere. However, for the device described here I happen to have completely different goals from that proposal.

It's easiest to do this moisturization on any coastline where typical trade winds or afternoon onshore breezes will carry the extra moisture deep above the nearby continent. I see a local solar or wind array providing the power. A pond or other onshore storage facility on the shore stores the salt water as stored hydropower for nighttime use. If the salt water happens to be solar-heated a bit from pond storage, this improves the evaporation rate as drops fall through the air stream.

An onshore facility pumps the seawater and screens out all plankton from the incoming salt water strean. We want nothing clogging the tiny holes in our sprayer pipes. It's possible to flush the system with relatively warm fresh water under pressure as needed to dissolve salt out of clogged pinholes.

A series of wave-proof bases set in the sand just a bit offshore support a sort of suspension bridge of cables, which supports the sprayer pipes. Extremely fine holes in the sprayer pipes create tiny droplets of salt water fog. Each droplet drifts down to the ocean's surface, where the droplets dessicate as they descend. Building this device just offshore will put nearly 100% of the salt back into the ocean. Pumping and filtering out particles from the water can be onshore in a less hostile environment. It's easier to build the suspension bridge towers on sand near the shore than in seriously deep water.

For a 1 kilometer wide sprayer, assuming that we're increasing the humidity in the air by 50% (about 1% more of the air will be water vapor) with 50% wastage, my calculations are that we need to pump roughly 12.5 cubic feet of seawater per second up 5 meters. This amount of pumping will deliver 720 metric tons of fresh water vapor per hour, 17,280 metric tons of fresh water vapor every 24 hours, into the lower atmosphere. I wouldn't be surprised to see much of that extra water vapor recovered regionally on land. Assuming constant trade winds blowing onshore, where else is the extra water vapor likely to go?

We need to account for two atmospheric effects of evaporation. First, evaporation cools the air. Second, moist air rises because a mole of water vapor molecules, 18 grams, has less mass than a mole of dry air molecules, 29 grams. So, my first guess would be that the moist air would drift ashore with trade winds, then solar heat on the land would heat the moist air, then thermal currents of moist, warm air would shoot up in the troposphere every few minutes, then small clouds would form.

It's possible to have multiple sprayers adding moisture to the same 1 kilometer wide layer of trade wind atmosphere. a set of 10 sprayers 100 km wide would put 17 million extra tons of water vapor per day into the atmosphere.

All of the moistened air blows inland, adding total incoming moisture to the region's air. This moisture creates fog and rain, typically as the air rises up mountain slopes, especially late at night. At some level this amount of moisture should replace the transpiration of billions of lost mature trees to restore that region's ecology. We want enough moisture to regrow billions of mature trees as soon as we can, so that we don't need these sprayers in the long run.

Obviously we don't want to add moisture on any day where we might be creating hurricanes.

Replacing the moisture from billions or trillions of trees is an enormous job. We don't intend to perform the entire job mechanically. However, adding to the total incoming moisture can potentially change nearby desert to scrub land to grassland to redwood forest. The rain or night fog descends, the moisture gets picked up and transpired by local trees and it eventually falls again. Every gallon of moisture over zero is a plus, so why not try it?

This solution is local or regional, so that every small arid nation or every state or province has an economic interest in stabilizing its own regional desertification problem.

I'm willing to consider a great number of variations of this system. In certain places there's no reason not to spray fresh water into the air where it's available. Spraying water droplets through a current of air captures smog particles from the local air. Running through the mist sounds like water-conserving fun in urban environments, without the expense and intricate plumbing of a splash pad.. The spraying process might lower the water surface temperature, protecting heat-sensitive corals below.

Note that moist air weighs far less than dry air. A mole of H2O molecules masses 18 grams, while a mole of dry N2 and O2 air masses 29 grams. Dry fronts along the U.S. Great Plains states are the spots where thunderstorms and tornadoes pop up, because heavier dry air sinks underneath lightweight moist air and allows the moist air to rise at an enormous velocity into the Earth's stratosphere. This general design could have major secondary side effects that need study.

U4d. Mister buoy for deeper water

The name of this device, the mister buoy, is nothing other than descriptive and also a rather memorable wordplay.

As of 9/19/24 my description of the mister buoy is changing. Here's the new description:

A cable attached to an anchor at the sea bottom is connected on its other end to the bouy at sea level. The wind's pull against the cable keeps the entire buoy always facing windward.

The buoy has several floats in a wide circle sticking up through the waves, or rarely through the still water. The wide circle of floats needs to keep the buoy from ever capsizing in rough winds.

I see the buoy sprouting three masts, in a triangle arrangement like a radio tower's mast. The mast arrangement is held in place by cross struts.

A wind turbine is attached to the top of the windward-most mast, in front of the mast.. It would be nice to have individual wind vanes that rotate into a high wind position so that a storm is unlikely to capsize the buoy. We may not need a particularly powerful wind turbine as the buoy will have limited power needs.

Solar panels are on the top of the three masts, hanging over all of the edges of the triangle. All solar panels are tipped edge-on to the windward direction but otherwise have one degree of motion by which they can track the sun, turning at an angle 90 degrees to windward.

Batteries are part of the ballast down below. At night and in light winds we may still want to add humidity to the air. Certain underwater floats may be partly filled or emptied with water as needed, in order to keep the structure vertical during high winds or during light airs.

Several elevations of horizontal mister pipes are supported by the two leeward masts, and they also extend well off of the left and right sides of the leeward masts. In very light winds, or well out to sea, the higher mister pipes may be used. With the high mister pipes in use a wide and tall cross-section of atmosphere gets misted and humidity gets added. In heavier winds only the lower mister pipes are used, or with an extreme onshore wind only the single lowest mister pipe is used, so that salt spray never reaches the shore. If the newly created atmospheric humidity might possibly feed into an offshore hurricane, all misting is halted.

- - - - - -

Older buoy description, matching the current sketch: An anchor keeps the buoy in position. The buoy can function several miles out to sea if needed.

A strong counterweight on or within the bottom of the buoy's hull keeps it upright. A solar array powers the buoy. The buoy has software and an actuator so that its solar array more or less tracks the sun from sunrise to sunset. This increases total energy available.

The buoy sprays salt water mist, which partially evaporates before drifting back down to the ocean. Trade winds bring the moister air generally toward the shore. As before, the mist pumping system can be shut off in case of a hurricane.

Here's a wave-powered humidifier. Water power from waves rolls the wheel. Air flows in between the many moisture-holding hudroscopic circular panels in the wheel's interior. Air blows into the wheel and humid air blows out. The system is simple to build and the salt buildup problem is solved by the wheel's regular rotation. Vast numbers of these wheels would humidify the air flowing onshore. re-terraforming the climate onshore.

U5. A rockbed water condensation option

One option runs moist air through a series of enclosed pre-cooled rockbeds for distilled drinking water. See also kchimney.htm on this website for the use of altitude to wring salable distilled water out of moist air.

Moisture-laden air flows through multiple rockbeds, cooling off the air, wringing precipitation out of the air. Hot moisture-laden air flows at laminar flow rates through a relatively warm rockbed, through a cooler rockbed and through a coldest rockbed before the air is either recirculated or released back into the sky. At least one of the rockbeds is usually being cooled off by blowing cold nighttime air through the rocks with fans, so that the rockbeds all operate in a cycle, with each rockbed progressively warming up while absorbing moisture from air, dripping off any extra moisture into a cistern, then finally cooling off with cold but often dry night air. Mold may grow on the rocks, but to my knowledge the mold won't affect the quality of the extracted drinking water.

A mountain slope water vapor chimney is a potent addition to any water vapor cooling process for many reasons. The water vapor-laden air can turn wind turbines as it rises within the chimney. As the air gains elevation, air pressure falls and so fog droplets can inherently condense out of the airstream. The top of a mountain is cooler in the daytime, which makes water vapor condensation more effective. The water can be stored as snow on a tall mountain for summer needs, and snow can restore a cold mountain's normal white albedo. Water running back down a mountain can generate hydroelectric power.

U6. Fog ponds

A solar pond is a pond of saline water that typically has several layers of salty to extremely salty water. Solar ponds can reach perhaps 180 degrees F. on their bottoms. Further improvements such as a layer of non-evaporating oil floating on the pond's surface or floating glass bricks on the surface will reduce daytime evaporation rates.

I believe in pumping water out of a solar pond and through specific areas near the pond where water is heated. Ponds are expensive to build and are cost-inefficient at heating water. In my opinion a pond's sole purpose should be to impound solar-heated water for nighttime applications, not to heat the water.

Other heat-holding fluids such as a mixture of eutropic salts, water laced with propylene glycol, stable oils similar to, say, factions of coconut oil and even ordinary air will work to hold heat at temperatures exceeding the boiling point of water. Air never boils, which is useful, although it doesn't hold that much heat per liter of air so the pipes must be bigger.

A solar and/or geothermal fog creation pond stores hot water and sometimes stores heat in other ways. Late at night in arid regions when outside air temperatures can plummet toward freezing, air comes into contact with the hot water. Billows of fog are created. Much of this fog can be captured in fog netting, and the rest naturally blows onto both crops and the natural vegetation near the fog pond. Fog ponds won't work on hot, dry afternoons.

An extensive network of large-scale solar fog-creating ponds that surround fields can put fog droplets on local crops almost every single night. Sequoia and coast redwood trees, among other plants, can live on nothing but fog droplets all summer. Fog deposition is an alternative way of watering crops and wildlands without extensive drip irrigation systems.

A breeze blowing directly up a nearby mountain range can blow added humidity up to the top of the mountain range. Especally late at night on a colder night, the altitude rise will wring almost all of the extra humidity out of the air as rain or snow. This wind-blown moisture-moving technique should be better than nothing and an affordable tool in helping to deliver more precipitation onto a mountain.

I suspect that some kind of cap on the top of a solar pond, say, an array of floating glass bricks, will prevent evaporation from the solar pond, which will help preserve the heat. My brick design nearly eliminates hot water evaporation and promotes solar heat absorption at low sun angles. I entertain safety concerns. If a person or a pet falls into the hot water, can they get out quickly? Bricks have to move out of the way of escaping people. An array of floating bricks needs a design that handles strong winds that can try to stack the floating bricks into one side of the pond, allowing evaporation on the other side.

I believe that existing solar ponds are grossly cost-inefficient. From an engineering standpoint it's fundamentally more elegant (less expensive) to keep near-boiling hot water within a deep central pond and pump cooler water out to lightweight heat-collecting arrays where the water can be solar-heated to something near water's boiling point. The pond should merely be a great way of inexpensively storing massive amounts of heat for later use.

If a water processing plant is situated at a distance from its saline water source, preheating the water within an air-sealed canal might work. The bottom of such a canal can act as a multiday heat sink.

Relative coolness is an important part of the multi-stage flash distillation process. Arid, low-humidity climates tend to get cold at night, often down to freezing. This coldness can be stored nightly and seasonally in the ground.

I sometimes picture a simple tack to the desalination process. If hot water is exposed to cold late-night desert air, fog forms. The fog can be captured in fog nets. This system will work in resource-poor nations. The remaining fog will drift over or through the fog nets to inexpensively water nearby crops or nearby natural vegetation at a great distance from the evaporation facility, without pipes. We may want to water coast redwoods and sequoia trees with extra fog in California if the region's megadrought gets extreme.

Late at night, during non-sunny or during peak demand hours, especially in winter, water from the solar pond is heated to steam in boilers with high temperature oil pipes or eutectic salt pipes. This steam runs through turbines to generate electricity. After grabbing easily available distilled water, the waste product is vented as night fog.

U7. Solar heating of water while generating photovoltaic power

Bill McKibben has this idea that somewhere, one engineer should invent a more efficient solar panel. I don't want to let him down. I'm not sure if this next innovation is needed but let's run some experiments on it and examine the financials.

Two or three times as much sunlight can be focused on a solar panel if its back is water-cooled. At the same time we need hot water for generating night fog. We might lay a PV panel flat on the ground so that we can have a gentle, steady, slow flow of water underneath the PV panel, and then we can use heliostats, tracking mirrors, to put a steady two or three times normal sunlight on the front of the PV panel. The same light that pushes electricity through the PV panel also heats the water. Most silicon-based PV panels can take up to 160 degrees F of heat before they melt.

At the same time, if we bounce light to the PV panel we may not need to encapsulate individual PV panels in plastic. So, we get a lower cost and a more recyclable PV panel, we might get several times more power out of it and we get useful residual heat out of it too.

It's possible to generate live steam from brackish water, from agricultural wastewater, from partially treated sewage or from seawater. I would need an evaporator that accepted brackish water heated slightly above the boiling point. Part of the water wouldn't evaporate, and that waste brine would have to flow out of the bottom of the evaporator. Boilers for steam turbines will at this time prefer fresh water and high heat, but a district steam heating system can use any source of steam. A steam boiler able to use seawater might accumulate a rime of sea salt on an extremely deep and relatively cool bottom, which could be mined for salable sea salt at the end of each month.

Given humanity's need to use inexpensive solar heat to distill vast amounts of water, solving the side issues of brine and rime buildup, especially while generating power, should be considered a mission-critical research goal.

U8. Preheating any variety of water in stages

Water such as seawater often has to be brought into a solar heating facility by a canal. A solar canal can be covered with an array of long glass floats optimized with tiny ridges on top for low-angle east and west solar heat absorption. The floats are tethered to the shores of the canal by ropes. The floats fit close together for low evaporation losses and are designed for easy canal exits if an animal or person accidentally falls into the canal. The canal could otherwise be covered by a superstructure, but that sounds more expensive.

A solar pond is possible, but heating water from 20 degrees C above the outside temperature to as high as 80 degrees C above the outside temperature is probably done most cost-efficiently by pumping the water through inexpensive solar heat collectors. I want to regulate the flow through heat collecting tubes so that the water never quite reaches the boiling point. A solar cricket system, a system whereby a pocket of freshwater steam forms in a hot part of a heat collection tube, emptying the tube, and then more brine water flows in when the steam pressure is gone, could be a self-regulating system and might work here.

Heating a well-insulated tank of 80 degree C water to perhaps just above the boiling point and under slight steam pressure, to perhaps 110 degrees C. or even to 130 degrees C in a higher pressured underground tank with a steam relief valve, is best done with a wall of concentrated sunlight from a field of heliostats. A huge, deep tank of heated and slightly pressured water should keep its heat well over a period of a few days until the operator needs to generate distilled water and/or electricity.

Stored geothermal heat transferred with a number of fluids including eutectic salts, certain oils and propylene glycol can be used to further heat water or steam at night. Various forms of geothermal heat storage may be inexpensive and effective as an aid for progressively heating and evaporating water. See also on this website, kdistricts.htm.

For further reading: https://theconversation.com/desalinating-seawater-sounds-easy-but-there-are-cheaper-and-more-sustainable-ways-to-meet-peoples-water-needs-184919