The LA Times reports a water shortage on Catalina Island at reasonably the same time that the Jamaica Observer reports similar news. Wouldn’t it be nice if there were a way to generate clean drinking water from sea water? I’ve been thinking about this for half of my lifetime and I’m sure that there’s a way. Consider this idea then published to the public domain as a royalty-free attempt to create energy and fresh water from the ocean.
Faraday’s Law of Induction
“The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit.”
What this really means is that if you move a magnet in proximity to an electrical coil it will produce power.
Imagine wrapping some wire around a cylinder and then—using a donut-shaped magnet—move this up and down to create power. All you need is a plastic torus which holds the magnet and since it’s mostly filled with air, it floats with each incoming ocean wave.
So now imagine an electrical coil of wire which is wrapped around a smaller-diameter PVC pipe and this assembly is then inserted into a larger-diameter PVC pipe. Embed the end of this in a sand screw anchor and place it so that the average height of an ocean wave hits it halfway up. The rising and falling waves will lift and lower the external magnet, producing power of the alternating current (AC) variety in the coil.
AC to DC
From this point, we’ll probably want to gang several of these together so the easiest method is to first convert the power from alternating to direct current (DC). A simple piece of solid state electronics is available which is called a Rectifier and one of these would be necessary on the output side of the coil mentioned earlier.
Output So Far
The power output of a rectifier in this scenario is pulsating direct current. It will vary from zero to some number of volts. The upper range of that voltage will depend upon the strength of the magnet(s) being moved as well as the distance from the magnet to the coil and factors like the number of turns overall in the coil itself. Additionally, the speed and size of the incoming waves would determine how much power gets transformed into the output of the rectifier.
Power = Current * Voltage
The usable power is a combination of both the amount of current that flows times the voltage across the circuit. Think of the voltage as the difference of cars between Los Angeles and San Diego (assuming that everyone is going south for Spring Break) and the current is a measure of the number of cars per hour seen on Highway 5 going southbound.
Admittedly, the current for one rig like this probably isn’t much. In a case like this you would want to create many of these rigs in one area and gang them together. Now that the power has been converted to DC, you can run these “in series” to increase the voltage or “in parallel” to increase the current. Regardless, adding additional units increases the power overall.
What To Do With That Power
Here is where things get interesting. We only have one moving part in this contraption, a wave-driven plastic donut that moves up and down to generate power. We can go a number of different routes from here.
- Build a pier that is suspended by these as a base and use the power to charge batteries. Imagine a pier which incorporates these columns to hold it up, only each column now has a large-scale bead which moves up and down. Inside each column is the necessary wiring which is terminated at a charging station on the pier. The power could then be used to run services on the pier such as lighting, for example.
- Route the DC power to a proton exchange membrane (PEM) fuel cell to split off hydrogen and oxygen. Note that a typical input voltage is usually less than 1.5V.
- Route the DC power to a more simple electrolysis circuit to split off both hydrogen and oxygen. Again, the typical input voltage is usually less than 1.5V.
- Store and later recombine the hydrogen/oxygen again using a PEM cell but this time producing power.
Decomposition of Salt
Seawater contains a healthy amount of salt. It may be worth noting that when you add a voltage to a solution with salt you split salt (NaCl) into ions at this point. With respect to the recombination of hydrogen and oxygen to produce drinking water, the chlorine itself would be a useful component with respect to keeping that water clean until it can ultimately be filtered for use.
In fact, there are a number of saltwater swimming pool options now which do just this; they split the salt to form chlorine which is used to then kill waterborne pathogens in the filter stage.
If we recombine water near our pier we could then use the extra chlorine to prevent the accumulation of water-borne diseases during storage and transmission. But we need not recombine that hydrogen and oxygen locally. In some cases, we need that water further from our project.
How to Lift a Gallon of Water to the Top of a Mountain
It may be worth noting that the country of Peru has 90% of its water on the east side of the Andes and yet 90% of its people live to the west of this same mountain range. If there were an easy method of moving water a great distance, you could solve their water shortage problems almost overnight.
Likewise, there are many cities which need water and the shoreline is some distance below the city in altitude. If you could generate drinking water from the ocean wouldn’t it be great if you could then transport it without needing more power to do so?
Imagine a water ladder, if you will. One of the two components of water is hydrogen and is decidedly lighter than air. This water ladder would be a tube which extends from our pier on the shore and the tube then runs diagonally (or even vertically) up the cliff to where that water is needed, say, to the top of a water tower.
In this case, we only trap the hydrogen output from the PEM cells and we allow this to bubble up through the pipe, arriving eventually to accumulate in a reservoir above a water tower. Here, a collection of PEM cells will recombine that hydrogen with air in the vicinity to create fresh water and to store it in the water tower. These towers are built to be high so that they will naturally create the water pressure that’s used to distribute it throughout a community. But fortunately, the nature of hydrogen is that it wants to rise all on its own. We use this aspect of hydrogen to lift half the component of water to the top of the tower and the oxygen freely available in air itself is the other half—we’ve solved a part of the transportation problem of moving water vertically up some distance and with a power gain instead of a loss.
A Sawtooth Water Delivery System
If you visualized that last suggestion as a diagonal (or vertical) water ladder which lifts hydrogen to the top of a tower, now imagine a diagonal water pipe which transports water to the next tower some distance away. A reasonable decline might be a 5-10% downgrade to easily transport water like this. Once the water arrives at the bottom of the next tower, split it again using PEM cells and have the hydrogen portion raise itself again to to the top where you repeat the process.
The following diagram is that of a sawtooth wave in electronics which has the shape of the path I’m suggesting. Hydrogen is lifted vertically from the base of each tower and then, using gravity, we’re allowing water to flow diagonally to the base of the next tower in the series. Of course, the slope would be much more gradual than this rendering.
Remember, each recombination of hydrogen and oxygen creates power and each splitting consumes power. Think of each tower as both creating and consuming power. The set of PEM cells at the top produce most of the power necessary for the set of PEM cells at the bottom. This may of course be augmented by solar cells which can make up the deficit power required, which shouldn’t be much. Electrically, each tower is a closed system and self-sufficient.
Using traditional methods of moving water over distances, raising water usually consumes great amounts of energy in the form of pumping stations as powered by electricity. Here, though, the weight of air or water itself is the pump which pushes hydrogen ever higher up a water ladder and doing the work for us. And once it’s arrived it produces water and power at its destination (as long as there is a source of air). In the traditional model, each HP of power used to pump water costs about $500/year. If you could see the average motor in a pumping station you would understand that this is an expensive task.
Given a typical water tower height of 130 feet and a decline rate of 10% to the next tower a conservative estimate might be to stage these towers at a 1,300 feet distance from each other. Lowering the decline rate to 5% would push the distances to about half a mile.
Storing hydrogen is difficult and costly. For it to be usable as a fuel it usually needs to be dried to remove any water vapor. Hydrogen itself is the active part of acids so it has the potential of being quite corrosive. Any untrapped hydrogen could create a hazard.
Batteries by their nature have metal connectors and in a marine setting will corrode more quickly than in drier locales. Most charging batteries of the lead-acid variety will produce untrapped hydrogen gas which itself could create a hazard.
Barnacles like to attach to most marine structures and could eventually prevent the free moment of our magnetic floatation bead. There are some coatings which might hinder the growth of these types of creatures from the surface of the PVC or similar materials.
Marine conditions could lower the lifespan of an average PEM cell’s internal surface. A specialized coating might be necessary for seawater.
The underlying source of this power is the combined masses of the sun, the moon and the Earth as they contribute to ocean wave height in an intricate dance. There is no foreseeable end to this energy source.
The device produces hydrogen & oxygen and produces energy which may or not be local to the device itself. The included transportation model allows the water to be moved along with minimal cost other than the tower system itself and its maintenance. In some communities shorter distances would minimize this cost and could be implemented with a single storage tower. The steeper the grade, the more efficient the movement of water within this system which is quite the reverse for conventional methods of pumping water.
The cost of a PEM cell is around US$60 these days. They are readily available commercially.