In the last section, we saw that the wave generator's valves are opened by hydraulic pistons. As with most any hydraulic machine, these pistons are powered by a basic hydraulic pump. The pump keeps a steady stream of pressurized oil flowing into the system. Emerald Pointe actually uses vegetable oil, rather than regular machine oil, since there is some risk of the oil leaking into the wave pool.

The directional control valve that operates the release gates at Thunder Bay

In the wave generator, the oil flow is controlled by a directional control valve. The valve is connected to several hoses, leading to:

The hydraulic pump
A collection tank that feeds oil back into the pump
The cylinder pistons

If you were to cut open one of the piston cylinders, you would see something like this:

You can see that the piston rod that extends outside the cylinder is actually moved by a piston head inside the cylinder. There is fluid on both sides of this piston head, fed by two different hoses. If the force is greater on the blue side, the piston will move to the left, and if it is higher on the orange side, the piston will move to the right. To change the direction of force, you stop pumping oil to one side and start pumping it to the other. This sort of piston cylinder is commonly called a hydraulic ram.

The directional control valve directs the flow to these rams. It has a small spool that moves back and forth, blocking some inlet and outlet ports and opening others. In this animation, you can see the basic design of this sort of hydraulic system:

When the spool is to the left, the high-pressure oil goes to the left side of the cylinder, pushing the piston outward. When the spool is to the right, it pushes the piston back in. As the high-pressure oil pushes on one side, the low-pressure oil on the other side is forced back into the oil tank.

The spool is moved back and forth by a simple solenoid (an electromagnetic switch controlled by an electrical current). The solenoid is controlled by an electrical timer. Every two minutes, the timer activates the solenoid so it pushes the pistons out for a few seconds and then pulls them back in. This opens up all of the release valves, creating a wave.

One of the most amazing things about this control system, and the wave generator in general, is how durable it is. All summer long, the Emerald Pointe crew starts the waves at the crack of dawn and doesn't shut the system down until the park closes in the evening. That's one tough work week!