SOLALGEN

Hybrid Algae Cultivation System Based on Conditioned Environment with Efficient Light Collection and Distribution System

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 Obiettivo del progetto (Objective)

'The strategic overall objective of the proposed project is to develop an optical light distribution system that will significantly increase the productivity of existing open pond algae cultivation plant designs while maintaining low capital and operating costs and consequently reducing the overall costs per unit mass of algae oil produced. Light intensity is a key parameter affecting algae growth. Depending on the algae species and cultivation environment maximum production rates are achieved with the light intensities between 30 W/m2 and 100 W/m2 - which is around 1/10 of the light intensity of direct sunlight. Furthermore algae are very efficient in absorbing the light that hits them and with fairly dense algae concentrations all light is absorbed in the thin top layer of the algae pond in the order of only few centimetres. These factors make open pond algae cultivation systems inefficient in their conversion of sunlight into algae oil mass. Photo bioreactors are closed systems with controlled light distribution and algae environment. Existing prototypes of photo bioreactors show significant increases in productivity, but are very complex and expensive to build. High capital and operating costs increase overall costs per unit mass of algae oil produced in photo bioreactors over open ponds, even with these significant increases in productivity. In order to achieve the objectives we are presenting innovative concept of hybrid open pond – photo bioreactor technology that will exploit advantages of both algae cultivation technologies, low capital and operation costs of open ponds with the light distribution system of photo bioreactors for higher productivity, in a new hybrid algae cultivation technology. Two technical approaches will be explored in the project: • open pond with light distribution system and • open pond / photo bioreactor hybrid system with light distribution and low cost closed algae environment system.'

Introduzione (Teaser)

Although the use of algae in the production of biofuels has enormous potential, the industry is struggling to grow consistent volumes at realistic prices. An EU-funded initiative made up of leading researchers investigated ways to utilise light energy to improve algae cultivation methods.

Descrizione progetto (Article)

Light intensity is a key factor in algal growth and conventional open pond algae cultivation is inefficient in converting sunlight into biomass. Open ponds are shallow artificial ponds typically built in a circular or raceway configuration that use paddle wheels or other mechanisms to continually agitate the water. Algal growth is encouraged through the addition of nutrients and carbon dioxide.

An alternative method is to use photobioreactors (PBRs), closed systems with controlled light distribution and environment. However, although existing PBRs show significantly increased productivity, they are highly complex and expensive to build. PBRs are artificial closed-system algal growing environments that provide a controlled and measurable process for consistent algal production.

The EU-funded http://www.solalgen.eu (SOLALGEN) project, aimed to build a low-cost light collection and distribution system for increasing algae production. Hybrid open pond-photo bioreactor technology was developed that exploits the advantages of both methods of algal cultivation. It combined the low capital and operating costs of open ponds with the distribution systems of PBRs to create a new hybrid technology.

SOLALGEN's prototype was based on improvements to an existing PBR unit, which included the addition of an open pond unit. Researchers focused on the light/optical system, which was installed on both the PBR and open pond units. In addition, a waste heat exchange system was developed that enables waste heat to be reused. The system was used to improve growing conditions during the cold season.

All sensors were tested and validated at the laboratory scale and a series of measurements conducted for the main factors affecting algal growth. Parallel experiments were conducted on the PBR and open pond unit, both with and without SOLALGEN improvements in order to determine the impact on production unit yield.

SOLALGEN will help to bring down the cost of algal cultivation, thereby reducing the cost of algae-derived biofuels to the point where they will be competitive with oil. Algae can also be used in the production of health food supplements, aquaculture feeds, cosmetics, pigments and antioxidants.