Know what it takes to build your own High Pressure Aeroponics (HPA)
Gathering information on HPA is very important before building your own system. We can learn a lot from other people’s mistakes and just avoid heartaches. Why go through the school of hard knocks if someone else has done it already? The problem we have is knowing what information is good advice while others are poor. So let’s talk about some of my research here.
First let’s set this straight that true aeroponics is high pressure. It happens to be more complicated but the most rewarding when it comes to plant growth.
The design of HPA can be traced to 1970. However, NASA revolutionized in the 1990s by reporting it as the most efficient way to grow plants in outer space. Many studies have proven the benefits of growing plants in an aeroponic system, both on Earth and in space.
Here are some of the benefits – PROS:
- It uses up to 98% less water than conventional growing methods
- The nutrients used are 1/3 the amount needed for hydroponics and soil growing methods
- We can plant more plants in a closer spacing
- There is no cost for any soil
- Some crops can produce up to four harvests annually rather than just two.
Even though aeroponics sound great there are a few downfalls – CONS:
- There are more pieces or parts to purchase compare to other growing methods
- It uses an expensive high pressure pump
- HPA requires close monitoring and maybe frequent maintenance, mainly clogged spray head due to salt buildup.
- The system depends on electricity to keep it running
- Relative short failures of the system could lead to loss of your whole crop in minutes instead of hours.
Now, let’s talk about the specifics of building an HPA (High Pressure Aeroponics) system.
There are basically two types of aeroponics
One that NASA produced HPA (High Pressure Aeroponics), and the LPA (Low Pressure Aeroponics) lower cost system. LPA systems are the most common used and built by DIYers.
LPA systems use a standard magdrive pump couple to some PVC or tubing, and a few miniature sprinkler heads. The water spray from an LPA sprinkler head has large droplets that surround the plant roots. LPAs generally run the system 24 hours and 7 days a week, continually wetting the roots. The works well, and are cheap and easy to build. However they are not as efficient as HPA systems.
HPA systems must operate at a high pressure, normally above 80 PSI, ideal is 100 PSI. The high pressure is used to atomize the water through a small orifice to create water droplets of 50 microns or less in diameter. One micron is one-millionth of a meter. The average diameter of human hair is 80 microns. So we are talking about a really tiny water drop. HPA also must run on a much accurate time cycle. HPAs might run 1 to 5 seconds on, and then off 3 to 5 minutes. Specific components are required in controlling the timing interval and creating the proper size mist.
NASA research has shown that plants are more willing to absorb nutrient water in 5 to 50 microns droplets more effectively than any other sizes. Water droplet size is crucial for sustaining aeroponic growth. Too large of a water droplet means less oxygen is available to the root system. Too fine of a water droplet, such as those generated by the ultra-sonic mister, produce excessive root hair without developing a lateral root system for sustained growth in an aeroponic system.
In review, HPAs require high pressure to operate properly for producing the optimal 50 micron droplet size from the misters. Also, HPAs need precise timers that are adjustable down to seconds.
The components of our system:
As mentioned earlier, NASA as shown that plants ae more willing to absorb water in the 5 to 50 microns. Therefore, it is for this understanding that HPA (High Pressure Aeroponics) is more efficient than the most common Low Pressure Aeroponics system.
Again, to achieve the optimal conditions for plant development, it requires some primary components and tools.
The basic components of our HPA are as follows:
- High-Pressure water pump
- Pre-Pressurize Accumulator Tank
- Electrical-Solenoid hooked to an adjustable relay timer
- Pressure switch
- Mister nozzles
High-Pressure water pump
High Pressure Aeroponics require a PUMP that can produce enough to pressurize the water to produce the ideal droplet size of 20 to 50 microns. These pumps are generally diaphragm pumps or reverse osmosis booster pumps. The pump must produce a steady 80 P.S.I. at your required nutrient flow. So look for a pump that can generate 100 psi or more. Some are using the Aquatec 8800 RO Booster pump. It can produce a maximum of 150 psi, so it gives you some play room. Its relatively cheap compared to other pump costs and its quieter when runnig.. The Aquatec 6800 RO Booster pump is also a good option as it can create 100 psi. However, verify you purchase it with the right regulator, and it is set for 80 to 100 psi. It’s difficult to change it later.
With most moderate systems with an accumulator, this pump will work. For larger HPA systems or if you plan to expand your system down the road, buy the Shur-flow pumps. They are used in carpet cleaners and soda machines and is a dependable brand.
Pre-Pressurized Accumulator tank
These tanks are used in many homes on well water and in travel trailers (RVs) to help maintain water pressure in the pipes They. prevent the pump over working every time water is called for at a faucet.
These accumulator tanks have rubber bladder that can expand and contract with water and pressure. This bladder creates two spaces in the tank; one of liquid and one of pressurized air.
A liittle physics here. You can not compress water, but you can compress air. If the accumulator tanks were filled to the very top you will find you will have no water pressure to get the water out. So for these tanks to work, there always has to be some top space in the tank to hold just air to build pressure.
Once the pump fills it with water, the accumulator will be able to let out pre-pressurized water, using the air pressure as a driving force to move the water out when a faucet is turned on.
So you may be thinking why we need a tank if we have a pump that can create the water pressure for the HPA system? Why spend the time and money on an accumulator tank?
Well, let see why?
The pump is easily the most expensive part of HPAs so extending the life of the pump is going to cut down on long term costs. So the first benefit of the tank is too reduce the fatigue and demands of the pump, less use, more pump life, it’s that simple.
But more importantly, the accumulator tank serves another purpose in creating an instant and constant pressure once the solenoid opens so that the spray heads can operate for short intervals with the exact pressure, they need to produce 30 to 50 micron droplets. If the pump was directly connected to your misters instead of going through the accumulator tank, there would be a brief period of time where the pressure would be lower than 100 psi, and this slow sstart pressure would create droplet sizes greater than our 50 micron range.
Examples of some accumulator tanks are Well-x-trol tanks. They are specifically designed to do exactly what we want in HPAs. Some common ones are about 2 gallons in size, however you can use different sizes. The smaller ones save space, or larger tank to make sure the pump has less of a running cycle.
Somethings to consider choosing a tank size
Keep in mind for larger tanks is that the larger the tank, the more “stagnant” the solution may become if you oversized it to system demands because the same solution will sit in the tank for long periods of time.
Larger tanks take more solution. So if you need to change your nutrients before the tank empties out, it will go to waste, if it can’t be recycled. Once you add water to your nutrients, it becomes volatile and starts to break down. So check with the supplier and ask what’s the usable life of a mixed solution.
Smaller tanks hold less per a given pressure and tend to drop fast if your system has heavy demands. This will force your pump to run more frequent.
***CAUTION: Always install a pressure release valve on your accumulator tank. If the pump or pressure-switch malfunctions and doesn’t shut-off properly, the tank could become a bomb and explode. The pressure release valve will prevent increases in pressure beyond a certain point. This is a very important safety feature!
An Electrical SOLENOID
An Electrical SOLENOID is simply the item in HPAs that will start and stop the water flow to the system when the timer turns off and on. It is an electronically operated shut-off valve. You plug in the solenoid into a relay timer circuit. The timer will control when the solenoid opens and closes, and when the plants receive their nutrients.
This system is not much different than an automatic lawn sprinkler system. So if you understand your lawn system, you know what this is all about.
Timers for running the solenoid are best when accurate down to 1 second “on” times, and “off” times in the minutes range. One timer to use is the ART DNe Recycle Timer, but there are many other brands that can be used. I plan to build my timer based on the Aurdiono.
The PRESSURE SWITCH.
This component if what controls the pressure to the whole system. It is either purchased separately, or is built into the pump as an unit. The Aquatec 8800 doesn’t have a pressure switch so be sure to purchase it separately.
The pressure switch tells the pump at what pressure to turn on and at what pressure to turn off. It’s that simple. What does is sense the water pressure in the line and when the pressure is low, it turns on the electricity to the pump, as the pump is running the pressure climbs. Once the pressure reaches the set point the pressure switch turns the electricity off. The pump stops running.
If you want your accumulator to be maximally pressured at 100 psi, but to be no lower than say 80 psi, then you set the pressure switch to activate the pump at 80 psi and turn off at 100 psi. Again, pretty simple.
The Aquatec company manufactures pressure switches made specifically for its Reverse-Osmosis pumps, and they can come pre-set to 80 psi cut-off, which is what you want to use.
The Spray Misters
Atomization is achieved by pumping water through nozzles at high pressure. Nozzles come in different spray patterns and orifices. Larger nozzles and orifices reduce the chance of clogging but need pressure to operate and have high-flow rates. This is not good if we are trying to save on our nutrients and cost of operation.
Selecting nozzles that produce the droplet size needed will provide adequate coverage at the intended rate and pressure. For most HPA applications choose a full-cone nozzle pattern.
Droplet size in a given spray may vary from sub-microns to thousands of microns. These droplets are categorized in different classifications. For HPA the classification is fine-atomization a fine mist of 10 to 100 um.
Fixed nozzles have certain velocity or pressure ranges of effectiveness. It makes since that higher pressure nozzles have high velocities. Caution is needed here. Such velocities have the power to cut off fine root hairs in an HPA system. So stay away from these types of nozzles.
Use a fine-mesh filter prior to your misting nozzles to prevent clogging.
Hydro-atomize water and nutrient solutions to 5-50 micron droplet range Spray. Jet nozzles with 0.025″ orifice operating at 80 to 100 psi should deliver droplets of 5 – 50 microns at a rate of 0.08 fl. oz. per second.
Hydro-atomize water and nutrient solutions to 5-25 micron droplets.
Spray Jet with 0.016″ Orifice operating at 80 to 100 psi should deliver droplets of 5 – 25 microns at a rate of 0.04 fl. oz. per second.
You bet, there’s a lot to grasp
Now, this system may seem overwhelming to you at first. I cannot tell you how many hours it took me to find enough resources to verify the items needed to make a HPAs, but it took a good deal of time over the past few months. Keep in mind that once you understand the above components though, the rest is just connecting tubing to the parts.
However, since I love computers and electronics, the system I build will be much more complicated than what’s needed or called for. My system will not just run as an HPA but will also be self monitoring. Meaning my system will know the temperatures, humidity, light, and spray intervals. All of this information will get logged and store automatically and be used to tweek the system.