Automation of fish farming systems

The topic of auto­ma­ti­on is beco­m­ing more and more important, espe­cial­ly in today’s world. Espe­cial­ly in indus­try, whe­re high pro­duc­ti­vi­ty is always the goal and pro­ces­ses are incre­a­singly digi­ta­li­zed (Indus­try 4.0), many dif­fe­rent app­li­ca­ti­ons of auto­ma­ti­on can be found. Howe­ver, the begin­nings of elec­tro­tech­ni­cal auto­ma­ti­on date back several deca­des. A major step was the deve­lo­p­ment of the so-cal­led pro­gramm­a­ble logic con­trol­ler, or PLC, in the 1970s. Sin­ce then, this tech­no­lo­gy has been con­ti­nuous­ly deve­lo­ped to take over more and more tasks. Nowa­days, the plan­ning and imple­men­ta­ti­on of elec­tro­tech­ni­cal plants is vir­tual­ly impos­si­ble without such a PLC.

The programmable logic controller (PLC)

A pro­gramm­a­ble logic con­trol­ler is basi­cal­ly the brain of a tech­ni­cal sys­tem. Its task is to ensu­re the opti­mal func­tion of the respec­ti­ve plant. Decisi­ve for its use are dura­bi­li­ty and relia­bi­li­ty under dif­fi­cult con­di­ti­ons. This means that the PLC is not affec­ted by dust, cor­ro­si­on or heat and the plant can the­re­fo­re ope­ra­te without con­stant supervision.

The app­li­ca­ti­on pos­si­bi­li­ties of a PLC are very wide. The desi­red func­tions, which the PLC is to imple­ment, are pro­gram­med accord­in­gly and loa­ded into the memo­ry. During ope­ra­ti­on, input signals are acqui­red and pro­ces­sed accord­ing to the pro­gramming, and then out­put signals are issued to con­trol other com­pon­ents. In addi­ti­on to simp­le app­li­ca­ti­ons, high­ly com­plex tasks can also be imple­men­ted, making it high­ly ver­sa­ti­le. Des­pi­te this, pro­ces­sing times are only in the mil­li­se­cond ran­ge, which allows a fast reac­tion to occur­ring events.

In addi­ti­on to con­trol­ling nor­mal ope­ra­ti­on, the PLC is also used for gene­ral moni­to­ring and detec­ting errors. If a fault should occur, it is detec­ted direct­ly and repor­ted to the user via various warning sys­tems and with detail­ed infor­ma­ti­on, so that quick action or coun­ter­mea­su­res can be taken. Such messages are out­put in the so-cal­led HMI, the „Human Machi­ne Inter­face“. This is a dis­play that is con­nec­ted to the PLC. In addi­ti­on to the dis­play of messages, it can also be used to con­trol indi­vi­du­al parts of the plant and to moni­tor various parameters.

Automation of recirculation systems

Pro­gramm­a­ble logic con­trol­lers are also incre­a­singly being used in recir­cu­la­ti­on sys­tems. In clo­sed recir­cu­la­ti­on sys­tems, many dif­fe­rent para­me­ters have to be con­trol­led to ensu­re good water qua­li­ty. This is essen­ti­al for the well-being and health of the ani­mals and thus for suc­cess­ful pro­duc­tion. The fol­lowing sen­sors are used to mea­su­re para­me­ters in aquacultures:

The sen­sors regu­lar­ly record mea­su­red values and for­ward them to the PLC. The sys­tem then reacts auto­ma­ti­cal­ly to fluc­tua­tions and crea­tes pro­gres­si­on cur­ves that can be view­ed by the sys­tem ope­ra­tor. The fol­lowing sen­sors are instal­led to mea­su­re para­me­ters in aquaculture:

    • tem­pe­ra­tu­re
    • fil­ling level
    • ORP / redox
    • PSU / salinity
    • pH
    • oxy­gen satu­ra­ti­on (O2)
    • flow rate
    • car­bon dioxi­de (CO2)

In addi­ti­on to set­ting the para­me­ters, the PLC is also respon­si­ble for con­trol­ling all actua­tors and sub­sys­tems. The fol­lowing com­pon­ents can be con­nec­ted to the automation:

    • pumps
    • com­pres­sor
    • val­ves
    • drum fil­ter
    • deni­tri­fi­ca­ti­on
    • ozone gene­ra­tor
    • sedi­men­ta­ti­on
    • auto­ma­tic feeder
    • oxy­gen production
    • light
    • ven­ti­la­ti­on

Sta­te of the art aquacul­tu­re faci­li­ties are often equip­ped with soft­ware solu­ti­ons for sub­sec­tions or indi­vi­du­al units (e.g. only for the drum fil­ter), but do not have auto­ma­ti­on of the com­ple­te pro­cess. The­re­fo­re, the data con­sis­ten­cy of cou­pled pro­ces­ses is not given, and the workload is dif­fi­cult to generalize.

 
The fully automated SEAWATER Cube

For the SEAWATER Cube we have deve­lo­ped our own auto­ma­ti­on solu­ti­on accord­ing to modern stan­dards. This is based on Sie­mens tech­no­lo­gy and has more than 30 func­tions (e.g. fee­ding, rinsing, aera­ti­on) and thus con­trols about 20 sub­sys­tems, resul­ting in full auto­ma­ti­on of the ent­i­re pro­cess. The fish know­ledge that is necessa­ry for a smooth plant ope­ra­ti­on is stored in our con­trol sys­tem. Thus, the ope­ra­tor does not necessa­ri­ly have to be a bio­lo­gist or fish far­mer to con­trol the rea­ring pro­cess. The plant knows all important direc­tio­n­al limits and warning values and is able to react inde­pendent­ly to chan­ging con­di­ti­ons. In case of pro­blems, the sys­tem calls the ope­ra­tor and the con­trol sys­tem can also be acces­sed from out­side via remo­te main­ten­an­ce. The full auto­ma­ti­on also results in a plan­n­ab­le workload in plant ope­ra­ti­on of 1h per day on average. A cloud con­nec­tion enab­les exter­nal access to all data of rele­vant pro­cess variables.

The panel as it is dis­play­ed in the SEAWATER Cube. Here you can see the over­view page on which all rele­vant com­pon­ents are lis­ted. The­re are dif­fe­rent ways to get to sub­me­nus and to see and con­trol more details.

A con­trol menu can be seen in this view, here on the drum fil­ter as an examp­le. The „Ope­ra­ting mode“ fiel­ds can be used to switch par­ti­al func­tions from auto­ma­tic to manu­al mode.

In sum­ma­ry, the SEAWATER Cube uses modern auto­ma­ti­on tech­no­lo­gy through the use of a pro­gramm­a­ble logic con­trol­ler to ensu­re opti­mal plant ope­ra­ti­on with a mana­ge­ab­le workload. The sta­te of the art in fish far­ming is thus rai­sed to a new level.