FAQ Facts Questions and Answers
FAQ Facts Questions and Answers
Where will A2WH work best?
The A2WH system needs Sun to do it’s work. It can tolerate a wide range of humidity but generally as temperatures and relative humidity rise the cost per gallon produced goes down. The system can work in areas with daytime humidity as low as 10% but the system gets heavier and more expensive as humidity drops. We can substitute wind to replace some sun which can work even better in areas with very low daytime humidity. We can also substitute electricity for the sun but prefer not to do so.
A2WH systems are ideal in areas where no surface water is available and where drilling wells are either abnormally expensive or where there is a risk of non potable water or salt water coming out of the wells. It can also be particularly effective in areas where it is difficult or expensive to dispose of the waste brine streams produced by RO (Reverse Osmosis) desalination systems.
The best areas in the gulf states are those who in a rain shadow or are prone to extended droughts. Any location where the ground water is saline is great.
The air to water system is generally less expensive than trucking in water especially when long term labor and fuel costs are factored in. All indications are that it could compete with RO desalination when the long term energy and environmental costs are factored in especially in the 10,000 to 100,000 gallon systems which normally have high disposal costs for their brine streams.
How will A2WH work in Arizona where there is lots of sun, low humidity and little Rain?
In particular how much water can it produce near Tucson and Phoenix?
What really matters is the delta between the daytime and nighttime humidity and strong sustained sun during the day. In fact our system will work better in Arizona that it does here near Seattle. Our system absorbs moisture at night and reclaims it during the day. Even in Arizona the nighttime humidity swings much higher as the air nighttime air cools.
I looked Tucson up and spot checked a few days in August. The humidity ranged from 22%RH at midnight up through 48% at 7:55. This is more than enough humidity for our system to operate. I checked all of July and the conditions looked good with every night reaching humidity of at least 48% and some nights as high as 75.
Under these conditions you would generally plan for 12 pounds of system per pound of water produced per day. This limit on production is really a limit of space and cost. It may be feasible to plan this area with as little as 8 pounds of system per pound of water per day in these conditions but it would be safer to plan on 12.
What is the best time of year?
Our system produces best during the hottest part of the year when water is under most demand and hardest to obtain.
The best time of year for our system is the hottest part of the summer when there is the longest sustained sunlight. Higher humidity also helps but the design of our system is such that it can work in even the very dry locations like Phoenix AZ and Las Vegas NV.
What is the worst time of year
Luckily our bad part of the year Winter coincides with times when people generally consume less water and when other water supplies are more plentiful.
We depend on solar heat and the system simply will not work without sun. Here in the Pacific northwest during the winter there is insufficient sun and way too much cloud cover to allow the system to work optimally. There are days where it will work but only on days when it receives good sun. There are options that use grid power to augment solar heat but they add cost to the system and increase operating costs.
We have been in greenhouses in Utah in the dead of January when it was 2F outside and 105F inside the greenhouse so the system could work just fine in some winter locations especially those which receive good sun and regularly rise above 35F during the day.
Another issue with winter use is that winter air contains much less moisture. That means we must process more air to get a gallon of water. In some instances this can be over 40 times more air. This is a challenge because we receive less solar energy to drive the electrial blowers during the part of the year when we have to work harder to get the moisture. This means the photo voltaic array must be larger for locations with dry winter air. Other areas have very moist winter air and will work just fine.
The default system is not designed to be freeze proof. Water condenses in our system is a chamber which could eventually become fully clogged with ice when the air is below freezing. The plastic used is flexible so it is unlikely to be damaged by freezing but the system will not produce any further water until this chamber is melted. In addition the water leaving the condenser travels through drain lines which may freeze solid and prevent the system from working until the next thaw. There are product options to mitigate these risks but they add to the system cost.
What Quality of water does A2WH produce?
The water is generally cleaner and has a lower TDS (Total dissolved Solids) than any common source of surface or ground water. As a result it can be used to dilute water from wells that have high loads which can reduce downstream treatment costs. It is cleaner and safer than any source of ground water.
The system produces water by extracting H2O from the air. Before this happens the air has been filtered multiple times. It is very close in quality to single distilled water. Due to the solar thermal design the air often reaches pasteurization temperatures before condensing which acts as a secondary sanitary mechanism.
What are the most popular uses for the A2WH technology?
- Remote cabins without a well. Most attractive where there is no grid power and where water must be hauled in.
- Industry and packaging where water shortages have caused work stoppage or lost revenue.
- Hotels in water scarce areas. Especially where they have lost room stay nights and/or reputation due to water shortages.
- Million $ homes which can be developed on land that could otherwise not be developed due to lack of water.
- Islands where overuse has eroded the freshwater lenses and destroyed wells. Especially islands with abnormally high cost of power.
- Municipalities where lack of water supply is preventing issuance of new building permits.
- Homes and business in the hurricane zone who are at risk of loosing power and or water supplies for extended periods of time.
- Well users in areas where dropping aquifer have degraded water quality and where drilling new wells has a low probability of success.
Is the system good for agriculture use?
The system can be viable for high value, high density crops such as citrus, tomatoes, grapes, herbs, etc. It can be particularly valuable where it allows greenhouses and aquaculture to be established on land with a good growing season where lack of water would otherwise prevent development.
Even when deployed at a scale of several million gallons per day the water produced is expected to cost over $800 per acre foot. This can be quite competitive with desalination especially when long term energy costs are factored in but it is sufficiently expensive that it would simply not be viable for use in many bulk crops such as rice and wheat.
Are systems available for home users?
Yes but it is generally most attractive for home users who have a fair amount of open yard space which receives direct sun. The system is generally too heavy to install on residential roofs unless they have been reinforced and certified by a local architect to take the additional weight. The system units can be used to provide a partially shaded patio roof but the supports must be locally engineered to meet code. The units do require periodic filter cleaning so it is best for them to be installed where they can be easily accessed.
The smallest system produces 3 gallons per day during the prime operating year. You must plan on the system weighing 13 to 18 pounds per pound of water produced per day. This means a 3 gallon per day system will weigh about 375 pounds. We generally plan on 15 square foot per gallon per day. This is generally rounded up to 20 sq foot per gallon per day to allow for service walk ways. This means a 3 gallon per day system will occupy about 60 square foot.
A 300 gallon per day system which is generally the minimum recommended by most counties to service a home will weigh 37,500 pounds and will occupy 6,000 square foot (0.14 acres). The system can generally produce about 2,178 gallons per acre per day or approximately 2.4 acre foot per year.
These numbers change based on location and time of year. We generally size the system to deliver the rated water in the region from June through Sept. Months with less sun or colder temperatures will either deliver less water or will require larger systems.
Is A2WH a Dew Catcher or Dew Condenser?
No dew condensers require a nighttime temperature that is either at or very close to the dew point. Our first generation night radiant condenser systems extended this so we could condense even when the dew point was 8F below the nighttime ambient. Even with these enhancements we found that we simply could not use that generation in a enough areas to deliver the desired impact. Another issue we found with the dew condenser systems is that they would work well during part of the year and then fail to deliver during the part of the year when they are needed the worst.
The new solar thermal A2WH system was specifically designed to overcome the deployment issues which limited success of the dew condensers. As a result we can install it in a wide range of locations with a high degree of confidence that it would deliver water when it is needed.
One of the benefits of this system is that it produces more water per square foot in many locations so even in locations where the dew condensers would work well the Solar thermal A2WH system will generally deliver even better.
How does A2WH technology work?
A2WH operate entirely from solar energy. This is mostly solar heat with a small amount of solar electricity used to operate valves, sensors and the electronic control system. This allows our system to operate much more efficiently which is especially important in areas where electricity is expensive such as islands where electricity is generated using imported fuels.
Most Air to water systems use refrigeration to chill air to the dew point that means that as the dew point drops the more the unit must do more work to sufficiently chill the air.
The A2WH system uses a desiccant to absorb moisture from the air. The higher the humidity the more water our desiccant can absorb per pass which increases production.
We use solar heat to drive both the airflow for the absorption process and to provide heat during the regeneration process which extracts the moisture from the desiccant and allows us to capture the water in liquid form. Unlike radiant condensation systems this system actually produces during the dry months even when there is no dew and it’s production can go up in windy locations which can prevent radiant chilling systems from working at all. Our technology can work in conditions where the dew point is far below the chilling level delivered by radiant chilling panels.
A sophisticated micro controller based sensor system determines when to switch between absorption and regeneration modes. We use different types and amounts of desiccants depending on the local conditions to optimize the performance of the system. A small Photo Voltaic solar panel provides power for the micro controller, sensors, various valves, etc.
We have an optional enhancement that uses wind energy (wind over 4.5 MPH) to drive circulation at night when the relative humidity is higher. To make this work best we increase the weight of the desiccant used in the system. In some areas with good nightly wind this allows the unit to work in areas with daytime humidity as low as 10% We have optional enhancements which allow electric fans and heaters to augment or replace the solar heat.
The input air is filtered before it enters the absorption chamber where the desiccant absorbs water out of it. The air is re-filtered when heated for regeneration. A final stage of filtering is used as the air enters the condensation phase where the H2O is turned into liquid water. As a result the output water is very pure. We still recommend treatment using a NSF 54 grade filter prior to consumption because we do not have any control over the cleanliness of the storage tank.
Why should Cities and Municipalities consider A2WH?
A2WH delivers an additional source of water that is reliable and less likely to be affected by contamination or drought than any other source. Increasing the diversity of water sources represents good planning and delivers increased resilience during unplanned crises. Our recommendation is for each municipal water source to look at their absolute minimum potable water needs during a stage 4+ water crisis. They should implement sufficient A2WH to meet their minimum potable water needs during the a crisis if two other major water sources became unavailable.
Any city or municipality which delivers more than 40% of it’s water from Desalination is at serious risk of not delivering adequate potable water if their desalination facility is off line. Shutting down a large scale desalination plant is easier than people realize. It can be caused by storm driven sediment, chemical, fuel, oil or sewage spills, electricity shortages, earthquakes, floods or Homeland security issues. A2WH represents an ideal auxiliary source which is unlikely to fail at the same time as the desalination plants.
Any city at risk of having their imported water sources compromised by earthquakes should consider A2WH. Those who import water through mountain especially those crossing fault lines are at even higher risk. Earthquakes can break delivery pipes in multiple locations which can take months to repair. Earthquakes can also make ground water sources unsafe or unreliable at the worst possible time when imported water is not available. A2WH represents an ideal auxiliary source of survival water and is unlikely to be significantly affected by earthquakes. A2WH can be installed in mountains above cities where gravity can be used to deliver the water during power outages common after earthquakes. As such it can pressurize the municipal water system even when the power is still out.
Is it necessary to treat the produced water
Even with high quality water it is wise to treat any water that will be stored for a long period of time. We can not guarantee the quality of the intervening pipes and storage tanks so even if it leaves our system clean it could be exposed to contaminates before it is delivered to the ultimate consumer.
For private consumers a NSF 54 grade filter is recommended for any water that has not been chlorinated. The cleanliness of our water can make this grade of filter last a very long time. RO membranes common in NSF 54 filters are most often clogged by minerals and other contaminants in the water. Since our water has incredibly low amounts of minerals or contaminants the RO membranes can deliver a very long life.
What about maintenance?
The input air must be filtered to remove dust. This is done using permanent electrostatic filters. These filters require periodic washing or the amount of air passed will diminish as they become clogged. Diminished airflow reduces production.The washing interval varies depending on the dust load in the area.
The solar panels decrease in efficiency as they become covered with dust and dirt. It is a good idea to wash or blow them off on a periodic basis. They can get pretty dirty and still work just like a window but ultimately cleaning them is a good idea.
The electronics are designed to last the life of the system but can be field replaced if needed. The same holds true for all the mechanical components.
The majority of the outer shell is made out of polycarbonate which is incredibly tough and highly UV resistant. It can be scratched but even if scratched it can be simply painted or buffed.
What about contamination?
The main point of contamination for other water sources is completely avoided because our water is extracted from the air. We filter the dust and the basic design is highly robust. If the unit is flooded with unclean water it must be sterilized and serviced before it can be safely used.
How will A2WH impact the environment
Compared to electiric grid powered units A2WH will reduce indirect carbon emissions by about 2 pounds per gallon of water produced by the system.
In general the system will have minimal impact on the environment. The air moving through the system is purified and dried before being exhausted. This air normally remixes with the ambient air with little impact.
Any area which receives significant off shore or in shore winds has such a large amount of air movement that it will be difficult to measure the impact. In most cases the water is consumed and re-evaporates mixing back into the air so it has a net zero effect.
For very large systems such as 1 million acre foot per year a research meteorologist should run the numbers because drawing this much water out of the air could have impacts on the local weather. For example it could reduce the humidity of downwind communities. Dry air is heavier than the cold air which means this volume of dry air could create dry wind rivers could do anything from flush smog out of city valleys or stealing energy from forming thunderstorms.
In some conditions dry stagnant air could eventually pool in the bottom of bowl shaped valley’s and eventually become sufficiently dry to prevent the units located in the same valley from working at all. A research meteorologist should be able to develop models which can be used to predict the impact for a given topography.
What is the difference between A2WH and other units available on market.
Most AWG systems are built around a refrigeration system which is very similar to that used in small electric air conditioners. The best units consume 600 to over 3,000 watt hours per gallon of water they produce. The industry average trends show consumption over 2,2000 watt hours per gallon which rise rapidly as humidity drops.
A2WH functions with no external electricity. This saves 3,000 watts per gallon. Our novel design and control system allows it to efficiently extract water in a wide range of conditions including conditions where electric AWG units become inefficient or do not work at all.
Our units can reduce carbon emissions by over 5 pounds of carbon per gallon produced as compared to grid powered electric systems. (2.2 pounds carbon per KWh saved * 3000 watts per gallon = 6.4 pounds of carbon per gallon of water). Even a small 6 gallon per day system this adds up to nearly 11,000 pounds reduced carbon emissions per year.
Our most important difference is the compatibility of the core design for scaling efficiently into millions of gallons per day at a reasonable cost. It’s other major benefit is compatibility with remote areas where grid power is either unavailable or expensive. In some areas our units can be installed in mountains outside of towns and provide both water pressure and electricity for the town. Rather than exaggerate summer power shortages our system can actually help reduce these shortages.
How does A2WH compare to Electric Refrigeration based AWG units
Grid or diesel powered AWG
Several companies offer electric and diesel powered AWG units of similar capacity in range of $3,000 to $8,000 with energy costs of $0.20 to $0.40 per gallon. Energy cost are higher with 50% humidity. Our unit will produce 21,900 gallons over a 10 year life so compared directly to a grid powered electric system the value of the water @ $0.35 is $7,665. If you add $5,000 unit price + $7,665 it yields a comparable of $12,665.
Off grid AWG
Our unit would be most appropriate in off grid scenarios where power is either diesel or photo voltaic generated so the power cost would be closer $11,497 which would yield an effective comparable of $19,162. This does not factor in fuel or electric price increases during the 10 year period which would raise our comparable value.
In bottled water where the kiosk is cheap but you pay more for the bottled water. The last time I had water delivered in Utah it was $6.70 per 5 gallon container after we paid the delivery fees. This works out to $1.34 per gallon. Over our 10 year life we would replace 21,900 gallons which at this rate would be worth $29,346. The bottled watter was a hassle with lifting the jugs, storing the empties, etc so ours should get a bump in value for convenience. In addition bottled water prices have been going up so it is reasonable to expect a price over $10 per 5 gallon barrel before our unit is end of life.
Where did you get 600 watt hours for the electric refrigerant AWG units?
We quote 600 watt hours at the low end for electric powered units because we have seen claims from other companies that they can deliver a gallon for 600 watts under ideal locations. Those ideal conditions where not fully documented but it seemed to be 85% humidity at 90F. In reality we have not found any customer in the USA who claims to do better than 1,800 watt hours per gallon. In most cases we have been hearing numbers that range from 2,800 to 4,500 watt hours per gallon. We have also hear that many of these units fail to work at all when the humidity drops below 48%.
What is comparable sizing for powering an electric refrigeration AWG unit using PV (Photo Voltaic solar panels)?
These numbers are only for comparison purposes. Our nearest competitor is a electric refrigeration AWG powered by a Photo Voltaic system or a diesel generator.
These are quick calculations based on statistics published for a Electric Refrigeration AWG unit sold out of Europe. Please confirm these with your solar design engineer. We used this particular electric refrigeration AWG unit because one of our customer prospects contacted us after they purchased the electric unit and still needed a better solution.
The electric refrigeration AWG unit is rated at 24 liters (6.3) gallons per day with a maximum power usage of 650 watts. Most of the electric units are rated for 24 hour production so I used an assumption of 1 liter per hour. Using their max power rating this came to a total of 15,600 Watt hours. Assuming the batteries charge at 75% efficiency and the inverter used is 90% efficient this would require (15,600 / 0.75) / 0.90) = 23,111 Watt hours. Assuming a 9 hour productive solar day this equals 2567 continuous watts which if divided by 200 watts per panel equals 13 panels. These are conservative minimum sizing numbers. Best practice is generally to scale the system to160% of the minimum numbers to allow for system operation during changing solar conditions. If you want year round operation then you must adjust these numbers to reflect the shorter effective winter solar day and the lower winter insolation.
I found 200 watt panels on the Internet for $1135 which brings the panel cost to $14,755. Assuming a factor of 1.5 for labor, wires, mounting brackets, etc this would equal a total before batteries of $22,132
Using the assertion that you need to operate electric refrigeration AWG unit 24 hours per day to produce 6.3 gallons then you need 24 hours – (9 hours of daylight) worth of storage = 15 hours at 650 watts = 9750 Watt hours. Assuming you can drain your batteries to the 20% level (use 80% without damage) and a 90% efficient inverter then you need a total of (9750 / 0.80) / 0.90) = 13,541 watt hours of storage. Assuming a 12 volt battery system this would equal 1,128 amp hours. I found PVX-1040T which is capable of about 80 amp hours depending on discharge rate and costs $285. Using this estimate it would require14 batteries at a cost $4,018 at a weight of about 910 pounds.
With batteries this would bring the power system cost to run the Electric refrigeration AWG unit 24 hours per day to $26,150 and it still would not work at under 45% RH. This estimate was based on published numbers from an external web site. They did not specify production under different conditions but other Electric refrigeration AWG units do show these numbers and a rule when relative humidity or temperature drop the energy cost per gallon goes up. I have to assume that this was based on their best case rating so most consumers should plan on system sizes 150% to 250% of these sizes depending on their local environmental conditions.
Note: It is possible modify this configuration to eliminate the batteries by running 3 of the electric refrigeration AWG units during the day. This would increase the power production to 3 liters per hour for the 8 to 9 hour solar day. The 3 units at 650 watts each and a 90% efficient inverter the would require a minimum of 2166 watts of PV or 11 of the 200 watt panels. You would also need 2 of the PVX-1040T batteries to handle startup surges. The higher grade 2.5KW inverter with surge to 6,000 watts for motor starts would cost between $1500-$2600 (islandearthsolar.com Part #08-53-010). You would also need 2 additinoal AWG units at a cost of about $2,000 to $3,500 each. The most interesting thing is that this system could operate only during the day when the Relative humidity is lower which is when the electric refrigeration units consume the most power. In short it would generally be more cost effective to add more battery capacity to allow the electric AWG units to operate between the hours of midnight and 8:00 am when the relative humidity is highest. You also need some more sophisticated switching logic to only turn on the number of AWG units that you have the energy to run or to switch off AWG units as the battery voltage drops. It would probably be best to oversize the power system for daytime use to at least 160% of the minimum to ensure the system can operate for the first 2 and last 2 hours of the solar day when the solar production drops off due to changing solar angles.
Please let me know how your real world install compared to my calculations.
In comparison our worst case price with all the optimizations to allow our unit to operate in climates with daytime humidity as low as 10% would cost less than just the power system for the electric refrigeration AWG units. In addition even our worst case unit would weigh less than just the batteries for the PV powered system.
How is A2WH different from desalination?
Desalination accepts a salty input water such as Ocean water or Brackish salt water. The salt is removed from the water using either a Reverse Osmosis (RO) membrane or a Distillation approach. The salt which is left is concentrated into a highly concentrated brine stream which must be disposed of. A2WH produces no waste brine so it has nothing to dispose of which can make obtaining necessary permits easier and less expensive. In general A2WH will compete favorably on a cost per liter basis when compared to the capital + energy + membrane costs for operating a RO system over it’s 20 year life.
We at A2WH feel that Desalination and A2WH are ideally used together. By leveraging both technologies an ideal mix of reliability and cost can be obtained. Spreading the investment for water infrastructure across multiple unrelated technologies it can improve the municipalities ability to withstand unanticipated problems and natural disasters.
Here are the main differences.
The A2WH system starts with standard air and extracts the water from it. It does not require a source water stream. This allows it be used hundreds of miles from the coast where land is much cheaper. It can be close to the point of consumption which reduces distribution costs.
Most RO systems leave a residue of salt behind. This generally runs under 400PPM to 900PPM. It is rated as safe for human consumption but may be undesirable. This level of salinity can result in soil salt toxicity as the water is applied many times and allowed to evaporate. The A2WH system starts from air which is filtered and then the moisture extracted in a separate phase. As a result the produced water has very low solids essentially equal to single distilled water.
The A2WH system is immune to damage from local oil or chemical spills which can destroy coastal desalination plants. The same holds true to storm and stilt based clogging of the input manifolds. As a result the A2W system can continue producing when the RO system must shut down. This makes the A2WH system an ideal pair with RO systems and increased the power supply.
The A2WH system does not produce any brine stream which must be disposed of. Brine disposal is becoming increasingly expensive and controversial. The difficulty in permitting and handling of the brine can prevent large scale desalination by non governmental agencies. .
State of the art desalination facilities generally use grid power to operate high pressure pumps and heating elements. State of the art RO systems can consume as little as 15 watts per gallon but this still results in the 10 million gallon per day RO plant consuming 150,000 KWh per day. Consuming this amount of power in regions already under heavy demand can increase electricity costs for all consumers. At 150,000 KWh per day even the best RO plants end up emitting over 300,000 pounds of greenhouse gas.
The desalination facility by nature tend to be located close to the coast or close to their source water. This can require pumping the water inland to the location where it is needed. Pumping the water uphill requires additional energy. The A2WH system can be located in mountains above the towns where the water is consumed. This allows the A2WH system to pressurize the city water system which saves power and maintenance costs. In some instances the A2WH water can generate electricity as it flows down from the point of generation to the storage reservoirs.
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