10 Sep 2017

How off-grid power and temporary heating and cooling supports the aquaculture industry

salmon hatchery
  • Written By

    Kenny Law, Aquaculture Specialist

  • Published in

How off-grid power and temporary heating and cooling supports the aquaculture industry

Scotland aims to become a world leader in the aquaculture industry and double the size of its sector by 2030. So we’ve produced a blog to remind the sector of the services and support we can offer to make production as efficient as possible.

Rising to the productivity challenge

Optimising power, heating and cooling is critical to achieve the huge increase in productivity required to meet the ambitious 15-year growth targets. It is anticipated that salmon production, which is the largest component of Scotland's aquaculture industry, will rise from 170,000 to 350,000 tonnes per year, while shellfish production is targeted to jump from 8,000 to 21,000 tonnes.

Stabilising tank water temperatures for optimum growth

Ensuring stable tank water temperatures during seasonal changes is key to the healthy development of salmon and shellfish. Responsive temperature control technologies can help alleviate ambient seasonal temperature changes that affect the water from rivers and lakes that feeds into a farm’s or hatchery’s tanks.

In the summer, rental chillers can temporarily cool down a tank’s water supply to ensure eggs do not hatch, or fish do not grow too quickly. In winter months, temporary boilers can warm up lower water temperatures to ensure the spawning and hatching process does not slow down.

Rental equipment can often provide the most cost effective, innovative response to seasonal demands.

Freshwater cooling with rental chillers

Aggreko has assisted leading Scottish salmon farming company, Cooke Aquaculture Scotland, to overcome warmer summer water temperatures at its hatchery in Argyll. Cooke uses a water recirculation unit supplied with freshwater to feed tanks where the fish are grown.

In the warm summer weather, when the temperature of the water within the large tanks rose, Aggreko provided an innovative and cost effective solution to quickly cool the water back to the exact temperature for the specific phase of the fish growth cycle.

This involved cooling the water from a slipstream of the recirculation water system by pumping the water through heat exchangers, where excess heat was absorbed. By reducing the temperature of the slipstream water a number of degrees lower than required, when the water was fed back into the tanks and mixed with the warmer tank water, the target temperature was achieved.

By cooling only the slipstream water and not the full tank capacity, the desired temperature could be reached speedily and effectively with minimum energy consumption, hence keeping costs lower.

Hot water boilers to warm up the growth cycle

Conversely, in harsh Scottish winters, colder temperatures can slow down the spawning and hatching process. This was the challenge at a freshwater hatchery for a leading independent salmon producer. Aggreko devised a diesel boiler and heat exchanger solution to warm up the river water prior to entering hatchery tanks.

This process was made highly energy efficient by integrating an additional heat exchanger at the point where the warm water left the tanks prior to returning to the river. The excess heat was recovered and channelled back into the primary system to maintain a continuous temperature. The heat recovery process meant that 25% less boiler capacity was required, which saved the customer £1200 per week in fuel costs. The system was monitored via a data logger to ensure optimum efficiency.

Providing critical site power

Electrical power is also essential for operating a fish farm or hatchery: important temperature control systems and recirculation water pumps etc depend on power to keep them operational. If the power fails then these processes fail, with a resulting loss in production and revenue. As many sites are located in remote areas where a reliable power supply is not a given, the need for back-up or standby power generators can be essential. Many sites find it most economical to hire a temporary generator, so they can scale their power requirements as needed and pass the associated routine maintenance, servicing and re-fuelling responsibility to the hire specialist.

Back-up power during grid outages

A Scottish highlands salmon hatchery chose to hire their back-up power when their incumbent 300 kVA generator became insufficient to support during regular power failures. Aggreko replaced it with a 500 kVA hired generator and an automatic changeover panel to ensure that the generator instantly activated if mains power failed. Using a hire solution also means they can swap out their 500 kVA for a larger or smaller model if load demand increases or decreases in future.

Supplementary off-grid power

Temporary generation can also meet top-up power requirements during peak levels of productivity, or when the existing electrical mains supply is already operating at its maximum capacity. Often network upgrades can take time, sometimes they’re not technically feasible or financially viable, and therefore there is a reliance on rental generators as standby power.

When a Scottish salmon company was experiencing unpredictable power failures at its remote highlands production site because the existing grid supply was too small, Aggreko implemented a cost-saving power scheme to provide off-grid continuous power.

Using a load-on-demand set-up, two 500 kVA generators were synchronised to operate together during peak periods of powerdemand, then, when the load dropped such as at night, one would switch off. This achieved a fuel saving of approximately £1,000 per week.

Specialist approach to rental power and temperature control

Aggreko has a qualified team of specialists and dedicated temperature control and rental power solutions: from specification and installation, through to commissioning, maintenance and removal.