Making Kilowatt-hours On A Seastead

(noboxes) #1

I am wonder about the feasability of a seastead making 10amps at 120vac, 24 hours per day, without  primary use of an internal combustion powered generator, and without  batteries making up the bulk of power at night. On 120vac, 10amps can run a small size of everything i can think of in a modern home, just not all of it at the same time. If you have a power bill from the electric company, this is the same as 864 kwh, or at $0.13/hwh it’s about a $120 bill’s worth.

I am not ruling out the use of a generator of some flavor, depending on how one uses the power, but lets restrict it to ~30 gallons per month, and do heat recovery on it too. Some things may need turning by an engine, not necessarily a generator. Going to land to get the fuel may cost you more than the price of the fuel itself.

Naturally, first choice in sunny weather would be the 1800 watts of solar panels on the porch roof.

In deep water, off continental shelves, i am thinking thermal-solar-boosted OTEC, with a 1000ft cold water line. It’s a 24-7 type of power supply, but hard to say how much power is affordable to build.

At night, 10amps at 120v for 10 hours is 16 hp-hours. I can’t say with any certainty what else can make this much power at night. Not that you would need it all at night, but if you did, for internet, computers, radar, radios, lights, refridge, and hvac, it’s a hefty constant load.

Your practical  ideas?

(bill mapezzi) #2

Why restrict to no battery use? weight or cost?

(noboxes) #3

Weight, cost, durability, maintenance. You can almost dismiss weight, except for the time spent carrying them around during replacements. If i am 80 yrs old and the battery is 80lbs, i figure the difficulty may be 80% too. Lead acids may be “cheap” if done right, but they last only 1/10 as long as lithiums, which cost 10x as much. For the less durable battery packs, you’ll wear out the mating terminals on the cabling before you are ready to move back to land in exasperation, and so need to replace all that too. I figured once that i’d need to set aside the cost of one battery per month for replacements, including the cost of getting to a recycler or battery seller, and getting the new one home, with the understanding i have no stockpile of batteries getting old before they are wired up.

To be sure, the various engines, and some actuators, will have 12v batteries which might be used in an emergency.

So i am saying if you are running on the current readily available technology of affordable batteries, something went wrong, your main power is down. Your main power may have a battery to keeps it’s brains alive between runtimes.

(noboxes) #4

So one nite your diagnostics says it’s tired of warning you about a particular battery, and it really really needs replacing. So you need to unwire and unbolt it, move it around your seastead (or boat) to get to the water taxi (your’s or someone else’s), transfer it without dropping it overboard, drive to land, transfer it (without dropping it overboard) to land, then into a land taxi (your’s or someone else’s), and then to the store, where you transfer it to a buggy, and push it into the store, where hopefully you can hand it off to an employee who won’t tell you they don’t carry that battery any more. But you get a new battery in the buggy, push it around the store til you have it paid for and out to be transfered to the land taxi (your’s or someone else’s), and then back to the water, and transfer to the water taxi (without dropping it overboard), then back to your seastead (or boat (looking at Octavian)), where it’s transfered (without dropping it overboard), and then you carry it around for a while until it’s where it will live, and you put it into place, and wire it up and bolt it down. And then tell the diagnostics to stop beeping at you, because you have picked up that battery at least 8 times since breakfast, and am in the mood to drop the beeping beeper overboard, or donate it to the skeet shoot team. Sometime in the next two months, it’s a sure thing you will need to repeat this procedure all over again.

(bill mapezzi) #5

Well, you mentioned Otec as practical … so dried seaweed? destructive distillation direct to a ICE?

Or forget the 1000 ft pipe (what will that get 8-10 degrees C differential?) and just heat the water more to maybe 55 degrees C. a 10 meter2 parabolic concentrator (fair game…you wanted me to track my panels last week) and an insulated water tank ought to do that. 3000watts X .6 =1800 /3 = 600X 24hrs = 7.2Kwh night or day.

(noboxes) #6

Yes, i believe otec is practical, but i don’t know how affordable it is for small scale. Or how mobile a seastead must be vs the 1000 ft pipe. Dried seaweed, meaning surface areas in the sun, and salt in the flames?

The 1000ft pipe is not a heat exchanger, it’s to suck up 40F or 50F water for one pass thru the otec cold side, and then (or alternating with) direct cooling of the habitat air. On a boat, sun tracking will be difficult with a parabolic, because it must be aimed far more accurately than a PV panel. But a flat panel is as accurate as a PV, and yet far cheaper too. If it warms the surface water to 100F and feeds it to the otec, that’s 50F or 60F difference, which is pretty good. Alternately, the 40F water vs the 100F water in an evaporative system as desalinator is a good deal too.

How much tank, and how much weight, and how much insulation, does your math give you?

(bill mapezzi) #7

Well, I haven’t read a description of yours for a seastead, so I was going with my interpretation of used tires stretched out all over the surface and under providing anchorage and safety to multiple simple pontoon boats… so surface area is a positive not negative (the more area the more tires you get paid to re-purpose…). The salt doesn’t go into the ICE because it is not even melted yet, might add flavor to the charcoal even, or collected from the ashes - positive by product.

I have no idea how economical Otec is other than the more heat differential the better, probably not 60% maybe 30-40% with 35-40C differential, I just looked stirling engine up - says 50% possible.

A parabolic dish ought to be as easy at sea to point directly at the sun as on land - just float it in a floating swimming pool. Those are way cheaper/hsp than PV panels as they are just reflective surfaces and capture more of the sun. The tank could be double walled concrete designed with thin plastic contained loose fill, also floating. Maybe one could build the whole unit together, that concrete disk/bowl design, floating the concentrator connected by three lines to computer controlled servos. The tank at the very bottom insulated also by the wamer water within the swimming pool.


Could use the seaweed in a biogas digester and use the methane in a fuel cell

(bill mapezzi) #9

It is so much easier to just heat it without oxygen, then burn the gasses, then burn the rest with oxygen, sell the ashes mail order as latest eel grass/kelp/mangrove leave concentrate for easier do doos or something. Probably better to add it to the diet of your (non commercial) fish farm underneath the growing miles2 of seastead.

(bill mapezzi) #10

I’m going to move to “wild ideas”


Sounds like yours is a lot more complicated and does unnecessary steps while taking minerals and nutrients out of the food-chain for extended periods, by oxidation (ash).

Mines about as simple as it gets, making the fuel, and clean. Can even use seawater and naturally existing methanogens from seabed sediments, instead of freshwater

(noboxes) #12

From “” :

I do not believe the energy required to dynamically force such accuracy vs water movement will be recovered from the plant’s total electrical output. Also, the amount of temperature (vs heat, which is a different animal) delivered by concentrated solar will break down the working fluids. There’s several working fluids which will easily generate over 100 psi between 50F and 130F, the range of deep ocean water temperature and solar flat plate collectors. And basically, you’d be putting up shade from the sun anyhow, make the shade be cheap heat trappers, and get electricity as payback. Still don’t know about thermal storage ponds or running on the unheated surface water at night. Or the effect of a cool rain at night.

(Craig G. Lewis) #13

Start with Micro Wind Belts.

Create the energy for electrolysis

Add this to a Kinetic power plant

The Electrolysis will split the water and create H and 02 gases. The gasses will be captured and run the Powerplant in direct drive. The gases can be captured and burned in a Gas turbine. and the Pressure in the tank could be use to drive an air generator.

So now we have one power input and 4 sources of power output or future energy storage.

Gas can be stored in underwater flexable tanks. The gases when needed can drive an air generator and burned in gas turbine.

Also energy storage with Graphene Supercapasitors. Small, Light, Fast Recharge and multi 1000’s of discarges before replacing.

(bill mapezzi) #14

Thats for a PV cell at 1000 suns or something focussed onto a square centimeter. I won 150 bucks in 10 minutes work at a town festival cooking a hot dog in 4 minutes with an aluminum foil lined direct tv dish. All the other contestants solar cookers barely had the hot dog warm in 10 minutes. A 21 foot diameter parabolic dish lined with reflective mylar will put 90 - 120 thousand BTU of heat onto the bottom of a glass insulated “copper pot” at the same 2 degrees in either axis from the a single axis tracker,at least 6-8 hours of 300-400 suns hitting the “element”. The “dish” itself is more like a bowl and has transparent “freeboard”. The same “boom” supporting the water filled element and plumbing extends through the bottom of the “bowl” and through a fixed gimball allowing 50 degrees or so of movement to track the sun. The water level in the “swimming pool” can be controlled a bit to keep the bowl more nuetrally balanced at higher “heeling degrees” by the same same program “running” the three servos that adjust the “boom” to “point” at the sun. The swimming pool temps will rise somewhat dependeing on the insulation of the “tanks” which are in the pool somewhere not interfering with gimbal braces, the boom, nor the concentrator itself. if the "swimming pool doesn’t remain calm enough for normal tracking systems…one utilizing this “free patent” design may have to build a pool inside of a lagoon floating on the ocean. Now you have more “substrate” for your shimps and a dimly lit lithosphere below the lagoon. Scaled up this is very practical and efficient use of space and materials not to mention solar energy. A 35 MW (continuous) CSP plant could be scaled up to the 100 acre size of the offshore “mussel farm” operating NOW in Huntington Beach, Ca. It would probably cost less also. Whats that $1,000,000.00 per week? still needs a “modified” Edison battery. think saltwater, buoyancy, high efficiency, extensive (save me a couple thousand words…:grin:

(noboxes) #15

FWIW, a reflective mylar sheet placed over a metal hoop, and a vacuum pulled, will make it be a nice lil dished reflector. I’ve used a vac to pull regular glass mirror to slight trough shape too. Anyhoo, reason for response: mylar film rots in a couple months and falls apart. I bought a roll of it.

(noboxes) #16

Aren’t those pricey buy and to maintain? What not a piston engine of some flavor?

(.) #17

Good idea, I might need more communication about it to fully understand.

Meanwhile, here is some information about practical land application of solar thermal energy.
I have been there, I have seen it, more than twice.

Congratulations of winning that price!

(bill mapezzi) #18

All you "engineers are free to “muse”. I’m going to read about biogas digesters,somehow ever since early 70’s Ive always thought of them as inferior somehow. Myabe just the whole controlled environment thing, where as heating and burning seaweed seems straight forward. As to mylar film… Ok cost just went up, aluminum foil not as cheap.

(noboxes) #19

Wait, what? The reflective mylar is mylar with an aluminum coating. You cannot stretch or smoothly shape non-plasticised aluminum foil, it tears and crinkles.


@chinaseapirate What do you want to know, w/respect to digesters?