FISH FARM WATER LEVEL MONITORING
Environmental power generation is on everyone’s minds today. Hydropower plays a major role here along with wind and solar power. In the Central European Highland and the Alps especially, hydropower has been used to generate energy in countless small plants since the dawn of the industrial age. This tradition is making a comeback within the framework of the current energy transition. A large number of small hydroelectric power plants have been built that enable direct consumers to generate their own green electricity or allow energy companies or local governments to supply green electricity in remote areas. Most of the modern plants are run-of-river facilities located in the middle of rivers, which means fish cannot avoid them. Such a setup disrupts the normal development of populations of certain types of fish, in particular salmon, which are obstructed by the plants as they swim upstream to their spawning grounds. Turbines can also literally suck in fish and chop them up. Solutions such as fish ladders require extensive investments that only really pay off for large hydroelectric power plants.
Diagram of water flow management from the river to the farm and vice versa
Breeding and replacing the affected fish species offers an alternative to expensive fish ladders. However, freshwater fish need a constant water exchange to thrive. Breeding trout, grayling and char requires exchanging the entire volume of water they grow in at least three times a day if their healthy development is to be ensured.
The Villitaimen Osuuskunta fish farm in Kemijärvi (Lapland, Finland) has four employees and grows several kinds of white fish from the roe their mother fish provide. The fish live on the farm for two to four years and are then sold to hydroelectric power plants.
The entire water supply for the fish farm comes from a river. A manually operated dam regulates the flow of water to the temporary storage units – screen wells, from which the water then flows to the fish basins solely on the basis of hydrostatic pressure, i.e. without the use of pumps.
The screen wells are each equipped with a water filter and a 36XW level sensor from KELLER Pressure that is used to monitor water levels and water temperature. Each screen well also has a GSM2* remote transmitter that sends the data recorded by the level sensor to employees’ mobile phones as an SMS.
Fish tanks for grown fish
Level sensors guarantee the farm’s survival
The engine that powers the entire water supply system is the hydrostatic pressure in the screen wells, which means the system doesn’t need any water pumps and is also independent of the power grid. That means there’s always enough fresh water for the fish even if there’s a power outage. After flowing freely through several fish tanks, the water goes through a biological refinery and then back to the river. The fish farm is only allowed to extract the legally permitted volume of water from the river. The warmer the water in the river, the less oxygen can be dissolved and more water must then be tapped from the river in order to ensure the fish remain healthy.
The well screens are equipped with 36XW level sensors that operate in combination with a GSM2* unit. The latter sends out data on filling levels to a computer in the farm’s main building once a day. Information on the water flow and the amount of dissolved oxygen is used as the basis for the manual regulation of the dam.
In the event that floating objects block the flow to the screen wells and cause the water level to decline, the GSM2* will send an alert to an employee’s mobile phone, after which the problem can immediately be eliminated. The reliable and highly accurate level transmitters from KELLER Pressure thus ensure that the fish remain healthy and the farm remains successful.
Digital output of the transmitter
The level sensor used is based on a stable, oil-filled, piezoresistive transducer and a micro-processor with an integrated 16-bit A/D converter. The non-linearity and temperature dependencies of the sensor are mathematically compensated. The free CCS30 software (ControlCenterSeries30) and the KELLER Pressure K114 converter enable the calculated pressure to be displayed directly on a computer as well. The CCS30 software also allows the recording and graphic display of pressure signals.
*The GSM2 remote data transmission unit was refined and then replaced by the new ARC1 unit.
