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.

U5. A rockbed water condensation option

One option runs moist air through a series of enclosed pre-cooled rockbeds for distilled drinking water.

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 steam.

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