Abstract: A method of operating a closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor comprises a culture liquid and is partially or completely surrounded by water of a water body. A density difference between the culture liquid and the surrounding water is provided so that the position of the photobioreactor in the water body is controlled. A closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor is adapted to comprise a culture liquid and to be partially or completely surrounded by water of a water body. The photobioreactor comprises means for determining the density difference between the culture liquid and the surrounding water.

Abstract: A method of operating a closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor comprises a culture liquid and is partially or completely surrounded by water of a water body. A density difference between the culture liquid and the surrounding water is provided so that the position of the photobioreactor in the water body is controlled. A closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor is adapted to comprise a culture liquid and to be partially or completely surrounded by water of a water body. The photobioreactor comprises means for determining the density difference between the culture liquid and the surrounding water.

Abstract: A method of operating a closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor comprises a culture liquid and is partially or completely surrounded by water of a water body. A density difference between the culture liquid and the surrounding water is provided so that the position of the photobioreactor in the water body is controlled. A closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor is adapted to comprise a culture liquid and to be partially or completely surrounded by water of a water body. The photobioreactor comprises means for determining the density difference between the culture liquid and the surrounding water.

Abstract: A method of operating a closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor comprises a culture liquid and is partially or completely surrounded by water of a water body. A density difference between the culture liquid and the surrounding water is provided so that the position of the photobioreactor in the water body is controlled. A closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor is adapted to comprise a culture liquid and to be partially or completely surrounded by water of a water body. The photobioreactor comprises means for determining the density difference between the culture liquid and the surrounding water.

Abstract: The present invention provides a fuel heating system for preheating a vegetable oil based fuel for use in a diesel engine, said fuel heating system comprising a fuel tank (1), a heating device (3), a heat carrier arrangement (4,6) comprising a liquid heat carrier, and a heat exchanger (6) arranged inside said fuel tank, wherein said heating device is arranged to use vegetable oil based fuel from said fuel tank for heating the heat carrier, said heat carrier arrangement allows transport of hot heat carrier from said heating device to said heat exchanger and transport of cold heat carrier from said heat exchanger back to said heating device, and said heat exchanger is arranged to allow heat transfer from said heat carrier to said vegetable oil based fuel in said fuel tank.

Abstract: The present invention provides a fuel heating system for preheating a vegetable oil based fuel for use in a diesel engine, said fuel heating system comprising a fuel tank (1), a heating device (3), a heat carrier arrangement (4,6) comprising a liquid heat carrier, and a heat exchanger (6) arranged inside said fuel tank, wherein said heating device is arranged to use vegetable oil based fuel from said fuel tank for heating the heat carrier, said heat carrier arrangement allows transport of hot heat carrier from said heating device to said heat exchanger and transport of cold heat carrier from said heat exchanger back to said heating device, and said heat exchanger is arranged to allow heat transfer from said heat carrier to said vegetable oil based fuel in said fuel tank.

Abstract: A method of operating a closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor comprises a culture liquid and is partially or completely surrounded by water of a water body. A density difference between the culture liquid and the surrounding water is provided so that the position of the photobioreactor in the water body is controlled. A closed photobioreactor for cultivation of phototrophic microorganisms. The photobioreactor is adapted to comprise a culture liquid and to be partially or completely surrounded by water of a water body. The photobioreactor comprises means for determining the density difference between the culture liquid and the surrounding water.

Abstract: The present invention provides a fuel heating system for preheating a vegetable oil based fuel for use in a diesel engine, said fuel heating system comprising a fuel tank (1), a heating device (3), a heat carrier arrangement (4,6) comprising a liquid heat carrier, and a heat exchanger (6) arranged inside said fuel tank, wherein said heating device is arranged to use vegetable oil based fuel from said fuel tank for heating the heat carrier, said heat carrier arrangement allows transport of hot heat carrier from said heating device to said heat exchanger and transport of cold heat carrier from said heat exchanger back to said heating device, and said heat exchanger is arranged to allow heat transfer from said heat carrier to said vegetable oil based fuel in said fuel tank.