James Flaherty explains an oxygen system that lowers mortality risk
SEVERAL years ago, Adsorptech attended its first Aquaculture America trade show in Las Vegas, curious about fish farmer needs regarding oxygen supply. One night at a happy hour, sipping a cold beer, fate put a major RAS design engineer and a farm insurance agent at the same stand up table. As a curious engineer, the question was asked: ‘What is important to the fish farmer about oxygen supply?’
In addition to the obvious cost reply, both low power consumption and reliable supply surfaced as critical.
Conference papers were presented about the infancy stage of Low Head Oxygen (LHO) technology advances. Lowering water pressure would substantially improve the farm’s overall power operating cost.
Many presentations discussed how RAS might just be turning the corner from interesting to profitable if all equipment suppliers were to ‘row in the same direction’ to improve RAS economics.
After the show, the Adsorptech team put our heads together to see if we could come up with something innovative and cost effective in the oxygen capacity range that present and future fish farmers would need.
From many long and oftentimes boisterous brainstorming sessions and more than a year of prototype testing, the EcoGen Oxygen VPSA (vacuum pressure swing absorption) was born.
Polling several farm technologists, all targeted circulating water pressures below 3 barg (43 psig). Two standard EcoGen models were created, one each at 1 and 3 barg (15 and 43 psig) to satisfy all farm and LHO developers’ targets.
At either pressure, EcoGen represents the most power efficient source of oxygen in the world. A 1 barg system requires 0.24 kw/kg oxygen which is 10 per cent less power (and 20 per cent to 25 per cent lower capital), both major improvements for farm return on investment.
The farm designer noted that at 50 per cent of the oxygen availability, the fish would not grow; but they also would not die. One cannot make a profit with dead fish.
The EcoGen is the only oxygen production technology in the world to have built in 50 per cent redundancy.
When one of the front end components is out of service for any reason, such as annual oil change, the EcoGen can still operate at 50 per cent of its production capacity, thereby lowering mortality risk
and avoiding higher back-up liquid oxygen cost.
The insurance agent mentioned earlier claimed that the farm insurance premium could be lower as a result of lower mortality risk.
Another unique EcoGen feature is its packaging, with only two parts to install compared to multi-component systems requiring additional installation cost, time, and risks.
EcoGen packaging eliminates the need for a building to house the oxygen equipment, and the system is currently operating in environments ranging from nearly 120F to-40F.
As the average size of RAS farms increase, the importance of EcoGen rises proportionally. The model range is perfectly suited for farm sizes of about 300 tonnes per year requiring 1,800 kg/day oxygen and more.
When purchasing your own oxygen generating equipment, about 20 per cent to 30 per cent of your already lower total oxygen costs escalate – power and maintenance. Also, multi-year LOX contract obligations will impact the farm balance sheet which is something most people simply do not realise.
James Flaherty, president and CEO of Adsorptech, will be presenting a paper on the technical and economic impacts of alternative oxygen sources at RAS tech. Adsorptech will be available in booth 31 at the RAStech trade fair.
“Both low power consumption and reliable supply are critical to the fish farmer”
Above: EcoGen model
Below: An EcoGen en route to an Israeli farm in 2016