HydroSphere — Efficiently Collecting Pure Water from the Air
The Problem — Water Scarcity
Water is the most fundamental need for humans to live and be healthy — yet 1 of every 3 people globally do not have access to safely managed drinking water. This is over 2.2 billion people who struggle to access water to drink, let alone cook, bathe, handwash, or grow food. With 71% of Earth’s surface being water, how is this possible?
Only 1% of Earth’s water is accessible freshwater, while the rest is salt water or stored in glaciers. Much of this water is polluted as well, leaving less for humans to use. This has resulted in 785 million people without any basic access to drinking water. Even those with access have to spend many grueling hours to bring the water home daily, missing out on education and other potentially valuable activities. Around the world, just women and girls spend about 200 million hours a day carrying water for their family.
Impacts of Water Scarcity
Water scarcity and polluted water may cause much more problems than you realize. In developing countries 80% of all illnesses are linked to poor water and sanitation conditions. Worldwide, 20% of deaths of children under 5 are due to water-related diseases, as the immune systems of young children are very susceptible to disease. Therefore, mothers boil water for their kids, using fuel so expensive that they cannot afford to cook food. Sicknesses and poor health caused by polluted water lead to poor productivity and struggles with education for kids, especially without adequate medical attention.
The impacts of clean and accessible water are tremendous. Kids, especially girls, who don’t have to spend hours a day carrying water, can instead get education. Parents don’t have to worry about dirty water and sicknesses, and can instead water crops and improve hygiene. Better nourishment allows kids to grow bigger, stronger, and smarter. Family’s can break cycles of poverty and spend income on school, funding small income-generating activities, and fees instead of spending much time and money on water.
The Status Quo
Currently, many people are trying to solve this problem of water scarcity through methods such as desalination, tapping into the huge supply of salty ocean water, or purifying polluted water. While these strategies can both help, they have drawbacks preventing them from impacting many people and being implemented around the globe.
Desalination is extremely energy intensive and environmentally harmful. Desalination plants spew 76 million tons of CO2 in the atmosphere each year, with that number expected to increase to 500 million tons by 2040 barring major change. This is 1.4% of all global carbon emissions. This is not only harmful to the environment, as such high energy needs are very expensive for a country and impractical for developing nations. Furthermore, for every gallon of clean water desalinated, a gallon of hypersaline brine is left behind. This salty waste product is difficult to treat and is usually released back into the ocean, where it damages ecosystems by spiking salt content and causing a large decline of oxygen levels.
Depollution methods are generally effective and somewhat cheap, but they can only be used in certain areas and situations. For many water-stressed, arid places without drinking water, they do not have a large supply of polluted water either. As the amount of unsafe water to be cleaned is much less than the already small 1% of freshwater, the impact of depollution has a hard limit.
A new, untapped source of water
A source of water without these issues is all around us — water vapor! This source of water is almost completely untapped and extremely abundant. There are 37.5 million billion gallons of water in the atmosphere at any one time, and through the constant hydrological cycle, this water is recycled 40 times a year. The result is about 15 million trillion gallons of water vapor recyled through the atmosphere each year — 4.6% of all the water on Earth! Additionally, water vapor is next to every home on Earth, and is still plentiful enough even in arid places with low humidity. The problem of water distribution can be completely eliminated by absorbing water vapor, and even arid regions and developing countries can get an abundant source of water.
How we can absorb this abundant water vapor
The reason this perfect water source is untapped is because of the difficulty in technology required to absorb water from the atmosphere and convert it to liquid water. Current strategies are inefficient, expensive, and use costly energy. However, 1 method takes no energy input, is self-sustaining and cheap — Metal-Organic Frameworks, or MOFs. MOFs are hybrid crystalline porous materials with extremely unique and varied properties.
MOFs, how they work, and their properties
They consist of a regular array of positively charged metal ions surrounded by organic ‘linker’ molecules. The metal ions form nodes that bind the arms of the linkers together to form a repeating, cage-like structure. Due to this hollow structure, MOFs have an extraordinarily large internal surface area. Researchers have synthesized MOFs that feature a surface area of more than 7800 square meters per gram. The available surface area in a teaspoon of this material would cover an entire soccer field!
Some of the unique properties of MOFs are uniform pore structures, atomic-level structural uniformity, tunable porosity (hollow space), and flexibility in network topology, geometry, dimension, and chemical functionality. This allows researchers the ability to control all properties of the MOF, like framework topology, porosity, and therefore functionality. Tens of thousands of MOFs with different properties, and therefore different uses, have been synthesized in labs. For example, MOFs have been functioned for gas sensors, atmospheric carbon capture, capturing radioactive nuclear waste, and even vaccines.
MOF-303 — Absorbing pure, drinkable water
The MOF we are using in our solution is called MOF-303, a relatively new MOF that is extremely good at absorbing H20 molecules from the air and is a natural filter, storing only water in it’s pores, resulting in pure, drinkable water. MOFs with this ability have been synthesized in the past, but MOF-303 is able to absorb water much more efficiently in lower humidities and can go through adsorption-desorption cycles extremely fast, in just minutes. This cycle is the process in which the MOF stores water vapor and released it as liquid. The water is released as liquid through heating of the MOF powder. Sunlight provides enough heat for this task.
On the larger, macro-level, MOF-303 looks just like a gray powder, and is made of aluminum. As a result, it is sturdy and suitable for rigorous climates around the world, as well as very cheap at just $3/kg. Furthermore, the MOF powder lasts a lifetime and can produce water for tens of thousands of cycles before losing efficiency. These properties make it excellent and sustainable for the job of water absorption.
Our Product — the Hydrosphere Box
Our solution is the Hydrosphere box — a box-like device with multiple sections, each containing MOF powder. Our first box will have 3kg of MOF powder total, but the amount of powder is proportional to the amount of water produced, so larger designs can be created in the future with more capacity for both powder and water. This segmented box design will allow for maximum air flow through the box, as well as better heating, and quicker release of liquid water.
To make this box work well, an extremely impactful variable influencing the production of water is air flow. The exposure to air of a stationary box is limited, and with a stationary box, usually only 1 adsorption-desorption cycle can be performed a day, with 2–4 cycles possible in ideal climate conditions. This produced an average of 0.4 L water/kg MOF per day. However, experiments have shown with a fan powered through an external power source, cycles can be completed in just 10 minutes, resulting in 57 L water/kg MOF per day. This increase in production is extraordinary, but using an external power source for the fan would take away an important feature of MOFs which make it feasible for developing countries to implement.
Improving efficiency and quantifying production
To solve this, we will implement a battery powered fan with a solar battery charged by sunlight. Generally, the places with the most crucial water scarcity are arid, warm places, often near the equator, with enough sunlight to sustainably power the battery. Depending on many climate and environmental factors, most important being relative humidity and temperature, the box can produce anywhere from 10–100 L water/kg MOF. For comparison, the average person needs 3.2L water to drink per day.
Logistics of Costs
The funding needed to implement such a product is not unreasonable and is feasible even in poorer countries, but the price can still be reduced and is slightly expensive to be widely commercially implemented. MOF-303 only costs $3 per kg. However, the cheapest small solar batteries currently cost about $30 and more efficient solar charged batteries can cost up to $70. The box will also have to be very sturdy, being outside 24/7 in possibly rigorous conditions. It will be made of thin, strong plexiglass with openings for air and collecting water. A 1x1x1ft box will be large enough to hold 3kg of MOF powder and cost about $25. The total cost of the product is currently about $70 with low-end batteries, which is not much in comparison to it’s lifetime of producing on average 171L water every day.
In the future, the price of this product will only decrease along with improvements in efficiency. Solar batteries are being developed to be smaller, more efficient, and cheaper, and advancements in the technology will allow for cheaper batteries with more efficient and larger energy storage. This additional energy will in turn increase the fan movement and airflow, thus increasing water production.
The Impact
The impact of these boxes will be remarkable when implemented. Even people in the most arid regions and deserts can have access to daily, recycled water which is more than enough needed to drink a healthy amount of water. With Hydrosphere boxes scaled up to contain many kilograms of MOF powder, a 10kg box can produce 100–1000 L water. With the average amount of water produce being about 570L, that is enough to quench the thirsts of over 175 people, and multiple of these boxes could help entire communities. Our current model of 3kg produces 171L water on average, enough for 57 people to drink.
Pure, clean water on a consistent basis — right outside your home
In addition, the Hydrosphere water source is uncontaminated and completely healthy to drink. This purity will help counter many water-caused illnesses and death’s. In a perfect world, this water will also be plentiful enough to be used for sanitation, cooking, and bathing. However, this is realistically only possible with drastic improvements to the MOF technology or in places with ideal climates. So, with current water sources not being used for drinking, they can be used to improve basic sanitation, although bathing in possibly contaminated water is unhealthy.
Our vision is that around the world, Hydrosphere boxes can be implemented in local, water-stressed communities and support millions of people with clean, pure water on a consistent basis. Although the output of water slightly varies based on the overall weather throughout the year, the amount of water vapor in the air does not greatly fluctuate. However, significant disasters and events like droughts can suddenly remove a community’s water supply and are devastating for large parts of the world.
Furthermore, these boxes will be placed locally in places where people can easily access water. This will almost eliminate the enormous problem of water distribution, removing the need to travel for water. Young children will not need to bear the burden of spending many hours a day collecting water and can focus on education, as well as other ways of helping their family. Instead of being a constant obstacle, getting water will be a quick and simple task.
Future Improvements and New Prototypes
MOFs are also being researched in many labs and can be improved. With their almost infinite unique combinations of functions through manipulation of material, shape, and properties, it is almost certain better MOFs will be synthesized for adsorption of water. This will be a significant step towards the goal of completely eradicating the problem of drinking water scarcity, and even allow extra water to be used for important sanitation uses, improving global health and preventing diseases.
Additionally, the way we tackled the problem of limited airflow in a stationary box was by using a fan to push surrounding air through the box. This is because it can be done using only a solar battery and no additional energy input, in addition to having a low cost and being tested and proven to work. However, this problem can be tackled another way: moving the box itself. By using a drone, or basic rotors, in order to move the box through the atmosphere, airflow would increase immensely, even compared to using a fan. This would allow for extremely rapid cycling and production of water.
The problem with doing this is cost and energy requirements. With current technology and even technology being developed in the coming few years, small, cheap, solar batteries are unable to power a drone carrying a heavy plexiglass box for very long. This obstacle is too significant to foreseeably overcame in the coming 5 years.
Another possible improvement is wheels. Much cheaper than a drone and less energy intensive, using wheels on the box can still increase airflow and therefore water production of the box. This solution can be powered by solar batteries as well, although much more expensive and efficient batteries would be needed. This idea has also not been tested and proven to work. However, it is a feasible solution that could take MOF boxes to the next level.
