Algae cultivation systems and methods with reduced energy loss

1. An open raceway algae cultivation system comprising:

a channel configured to contain an algae cultivation fluid, the channel including a contraction zone having a width and a depth and an expansion zone having a width and a depth; and

a pump configured to circulate the algae cultivation fluid in the channel, the pump including an entrance and an exit,

wherein (i) the width of the contraction zone decreases leading into the entrance of the pump, and (ii) the depth of the contraction zone is greater than a depth of at least a portion of the channel located outside of the contraction zone,

wherein the depth of the contraction zone varies such that, when the algae cultivation fluid is circulated in the channel, a cross-sectional area of the algae cultivation fluid in the contraction zone is substantially the same as an average cross-sectional area of the algae cultivation fluid outside of the contraction zone, and

wherein a bottom of the channel at a beginning of the contraction zone is lower than a bottom of the channel at an outlet of the expansion zone.

2. The open raceway algae cultivation system of claim 1 , wherein (i) the width of the expansion zone increases going away from the exit of the pump, and (ii) wherein the depth of the expansion zone is greater than a depth of at least a portion of the channel located outside the expansion zone.

3. The open raceway algae cultivation system of claim 1 , wherein the depth of the contraction zone varies such that, when the algae cultivation fluid is circulated in the channel, energy loss is minimized as the algae cultivation fluid circulates from outside the contraction zone, through the contraction zone, to the pump.

4. The open raceway algae cultivation system of claim 1 , wherein the pump includes one of (i) a paddlewheel, (ii) a propeller pump, or (iii) an Archimedes screw pump.

5. The open raceway algae cultivation system of claim 1 , wherein the depth of the contraction zone varies such that, when the algae cultivation fluid is circulated in the channel, the depth of the algae cultivation fluid in the contraction zone varies such that velocity gradients for the algae cultivation fluid are minimized as the fluid circulates from outside the contraction zone, through the contraction zone, to the pump.

6. The open raceway algae cultivation system of claim 1 , wherein the depth of the contraction zone increases leading into the entrance of the pump.

7. The open raceway algae cultivation system of claim 1 , wherein the depth of the expansion zone decreases going away from the exit of the pump.

8. The open raceway algae cultivation system of claim 7 , a rate of change of at least one of the width or depth in the expansion zone is linear.

9. The open raceway algae cultivation system of claim 7 , wherein a rate of change of at least one of the width or depth in the expansion zone is non-linear.

10. The open raceway algae cultivation system of claim 1 , wherein a cross-sectional area of the algae cultivation fluid at a cross-section in the channel is defined by a depth of the algae fluid times a width of the channel at that cross-section.

11. The open raceway algae cultivation system of claim 1 , wherein a lower end of the contraction zone continuously decreases from a portion outside the contraction zone leading into the entrance of the pump.

12. An open raceway algae cultivation system comprising:

a channel configured to contain an algae cultivation fluid, the channel including an expansion zone having a width and a depth and a contraction zone having a width and a depth; and

a pump configured to circulate the algae cultivation fluid in the channel, the pump including an entrance and an exit,

wherein (i) the width of the expansion zone increases going away from the exit of the pump, and (ii) the depth of the expansion zone is greater than a depth of at least a portion of the channel located outside of the expansion zone, and

wherein the depth of the expansion zone varies such that, when the algae cultivation fluid is circulated in the channel, a depth of the algae cultivation fluid in the expansion zone varies so that a cross-sectional area of the algae cultivation fluid in the expansion zone is substantially the same as an average cross-sectional area of the algae cultivation fluid outside of the expansion zone, and

wherein a bottom of the channel at a beginning of the contraction zone is lower than a bottom of the channel at an outlet of the expansion zone.

13. The open raceway algae cultivation system of claim 12 , wherein the depth of the expansion zone varies such that when the algae cultivation fluid is circulated in the channel, the depth of the algae cultivation fluid in the expansion zone varies to minimize energy loss as the algae cultivation fluid circulates from the pump, through the expansion zone, to outside the expansion zone.

14. The open raceway algae cultivation system of claim 12 , wherein the depth of the expansion zone varies such that, when the algae cultivation fluid is circulated in the channel, the depth of the algae cultivation fluid in the expansion zone varies so that velocity gradients are minimized as the algae cultivation fluid flows from the pump, through the expansion zone, to outside the expansion zone.

15. The open raceway algae cultivation system of claim 12 , wherein the pump includes one of (i) a paddlewheel, (ii) a propeller pump, or (iii) an Archimedes screw pump.

16. The open raceway algae cultivation system of claim 12 , wherein a cross-sectional area of the algae cultivation fluid at a cross-section in the channel is a depth of the algae fluid times a width of the channel at that cross-section.