Raceway ponds are affordable and effective algaculture systems that are usually built to take advantage of natural sunlight. While they make look like simple oblong ponds with a few internal divisions, they’re actually far more complex and require a lot of engineering skill to build. Following pre-made plans can help, but they won’t account for differences in the application of the system. For the best results, hire engineers to model the raceway design based on your target viscosity and changes in water volume over time. Adapting these basic features of all algae raceway ponds to the specifics of your plans will help you build a system that works well for years to come.
Smooth Curves for Fluid Dynamics
Raceways are different than ponds in that they’re designed to keep water flowing rather than standing still. The race part of the name comes from the fact they’re generally designed as either a single straight passage or a series of looped circuits that resemble a racetrack. The raceway shape relies on smooth and even curves at both ends of the track to create the turbulence and water mixing necessary for rapid algae growth. The exact dimensions and shape of the raceway’s curves have a huge effect on the efficiency of the raceway, so bringing in a fluid engineer is a good idea for any new algaculture project.
Careful Attention to Depth
Raceways are deeper than bioreactors or closed tube systems due to their constant agitation, but they still need to stay shallow to maximize light exposure. Yet, making a raceway as shallow as possible will backfire by speeding up evaporation to the point where the algae struggle to stay alive. You can’t compensate for light exposure by having to constantly refresh the raceway with a steady flow of water due to evaporation. Each species varies in its preference for depth and light exposure, and the total surface area of the raceway must be taken into account as well.
Permanent and Impermeable Lining
No amount of fresh influx of water can make up for a steady loss through an unlined pond or raceway. A permanent and truly impermeable lining, such as AquaArmor from BTL Liners, is the only solution. Materials like concrete and bentonite clay are far from as waterproof as they seem. These materials will still allow water to slowly seep out over time, weakening the soil below the raceway so it has the potential to give way and damage it. Flexible polymer materials like RPE are the only reliable method for sealing in water, whether it’s in an algae raceway or any other type of in-ground pond. These liners are also ideal for secondary containment around any bioreactors and tanks that are built for above-ground use.
Circulation and Mixing Equipment
No raceway for algaculture is complete without some kind of powered equipment to mix the solution and keep the algae well circulated. Circulation must continue every hour light is applied, whether naturally or artificially, to ensure both even and steady growth rates. Algae that stall from a lack of light can easily die off or fail to grow even when light levels resume. Backup equipment for emergency circulation is recommended to prevent malfunctions from risking a die-off event in the raceways.
Harvesting Areas
Finally, the raceway should feature settling tanks or other harvesting features built into the design from the start. Having to pump the raceway empty, just to settle the particulate into a different tank, is a waste of time and energy. Proper linings go a long way in making it easier and more efficient to harvest the algae directly out of the raceway it grows in. Make sure all harvesting kettles and settling areas built into the design are lined to prevent water loss during the process. Even though you need to concentrate the algae density by removing water, you want to direct where it goes rather than letting it seep out into the surrounding soil.
There are thousands of specific designs for raceways out there, each with its own benefits and drawbacks for each cultivation method. Try to find reports on how each species of algae you want to cultivate performs in certain raceway designs before choosing them. Since the industry of algaculture is still developing, it’s likely you’ll have to design new raceways from scratch, or at least modify existing designs to fit your needs. Reach out to us here at BTL Liners if you need practical advice on solving lining issues for algae raceways.
