Friday, January 29, 2010

Why wind?

Any discussion of sustainable energy for the islands has to include other options. There is a lot of non-fossil fuel energy in world. Which might make sense for Matinicus and Criehaven?

First a note about electricity. Most of the technologies below create electricity, which is not directly practicable for transportation, such as fishing boats. For example, 100 gallons of diesel weigh about 700 pounds. To store the same amount of energy in high tech lithium phosphate batteries would require a battery bank that weighs about 22,000 pounds. Using traditional lead acid batteries, the batteries would weigh over 380,000 pounds. So, even ignoring capital cost, life cycle costs (batteries wear out), recharge time, etc., it is pretty obvious most fishing vessels cannot bear the additional weight of batteries. “Plug-in” lobster boats are a very long way off. (So are plug-in cars, but that is another story.) We need to convert the electricity to an energy dense fuel. [see revision comments at end]

Why don't we just build a cable to the mainland? Construction costs would be about $25 million, about the same as the proposed wind turbine/NH3 facility. Assuming we get 20 year 5% mortgage, that will cost us about $2 million per year in interest. Then we still get to pay 15 cent/kwh (Maine average, October 2009) and whatever the amortization of the local grid on Matinicus is. It still would not provide power to the lobster fleet, nor would it provide for other energy needs, such as gas for cooking.

For routine transportation, there are just two basic fuel types available, carbon and hydrogen based. (I am going to ignore rocket ships, portable nuclear reactors, and other sci-fi). The carbon based fuels, such as gasoline, diesel, methane, ethanol, and propane, have most of their energy released by the combustion of carbon (and some hydrogen) in an internal combustion engine, turbine, or boiler. All carbon-based fuels need carbon to be created, obviously. On-island, we do not have significant quantities of carbon available. We do have trees, but they grow slowly. Theoretically we could gasify the trees (and certain other “waste streams”) to make a methane mixture, but we would run out of trees pretty quickly. Sugar cane produces the most fuel per acre today, but that won't work in Maine. Corn (for ethanol) by some reckonings actually uses more energy than it produces, and it doesn't grow well here, either. I'll do some specific calculations some other day.

Hydrogen fuels, such as H2, metal hydrides, and NH3, do not require any carbon to create. Since we do not have large carbon resources, we are essentially limited to hydrogen fuels to produce locally.

H2 (hydrogen gas) has serious problems as a transportation fuel. To have the same energy as 100 gallons of diesel, one needs a 2,700 gallon heavy tank of hydrogen, compressed to 6,000 lbs/in2. For comparison, a SCUBA tank is usually pressurized to 3,000 lbs/in2. Hydrogen has another big problem in that it is extremely susceptible to leaks. Hydrogen is the smallest atom and leaks through fittings that are tight against other gases. Pure hydrogen burns invisibly, so a fire from a leak cannot be seen. Safety manuals suggest using a broom to find a hydrogen fire: wave it over the suspected flame and see if the broom catches fire. Since the hydrogen atom is so small, it tends to penetrate metals, especially steel, and embrittle them, eventually leading to a catastrophic failure. So, pure hydrogen gas is very problematic.

Some people discuss storing hydrogen in metal halides, compounds that can chemically bind hydrogen. I do not know much about them yet, but I have heard they suffer from significant energy density issues. Several of the hydrides react explosively with water. Probably not a good idea for a boat.

NH3 is an effective hydrogen carrier. NH3 actually has more hydrogen per gallon than either compressed hydrogen or liquid hydrogen. Our 100 gallons of diesel would require 253 gallons of NH3. Not great, but still it would fit under the deck on most boats. Boats would not have to carry as much fuel as diesel, since the supply would be local. A fisherman does not have to go inshore or wait for the buyer to deliver fuel.

NH3 is a relatively large molecule, so there are not any special concerns regarding fittings and leaks. While it does not embrittle metals like H2, NH3 when reacted with water is corrosive to copper and zinc. Conversions of engines will require substitution of any copper or zinc in the fuel line. I am not aware of modern engines having any of these metals, however. There would be no change in the use of zincs as sacrificial corrosion inhibitors.

On to other energy options!

Deep geothermal

Extracting heat from deep below the earth's surface has several advantages. The heat is constant, with equal amounts of heat in winter and summer, day and night. The heat is used to make steam which then runs turbines to make electricity. There is enough deep geothermal energy to provide over 100% of the US energy needs. The electricity then needs to be converted into a usable engine fuel, such as NH3.

Unfortunately, the deep geothermal resources in the US are all west of the Mississippi. We are out of luck.

High altitude wind

There are several research projects for putting wind collectors up in the jet stream, over 20,000 feet high. The wind is constantly blowing, often over 200 mph. One design is held aloft like a paddlewheel on a balloon, another is an autogyro, which looks a little like a helicopter. A cable brings the power down. Because the wind is stable up so high, the kite stays aloft and stays in the same position.

The wind blows west to east, so a kite launched from the islands would be flying way out to sea, and not over any other populated places. This technology is said to be 10 to 20 years away. It has been estimated that capturing one percent of the jet stream wind could supply 100% of the global energy needs. We are located in a good jet stream area, so maybe this will be effective for us one day in the future.


Thermal solar, converting solar radiation to steam that goes through electric turbines, has great possibilities. A plot 100 mile by 100 miles in the Arizona desert could produce enough electricity for the whole US, assuming you could get it built with all the little bugs, “environmentalists”, and lawyers in the way. However, last time I checked, we don't have quite as much sun as Arizona, so we are out of luck.


OTEC stands for Ocean Thermal Energy Conversion, which is a technology that takes advantage of the difference in temperature between the bottom of the sea and the surface. In the tropics, surface waters can be as high as 90 degrees, while a mile down the temperature is below 40 degrees. That difference can be used to power a turbine. The potential is huge; tapping one percent of the heat could meet 100% of the world's energy needs. It is highly capital intensive and still in development. Unfortunately, our surface waters are lot closer to 40 degrees than 90 degrees, so it won't work for us.

Waves, Tides, and Currents

This always seems like the obvious stuff to research in the Gulf of Maine. Seeing the surf smash up on Sou'west Point, I always thought waves should be a no-brainer. I discussed this with several researchers, who almost laughed. We actually have very little wave power because a) we are sheltered by Nova Scotia, and b) we are on the East Coast. All the big wave energy is on the west coasts, as the waves build with the wind across the ocean. This is a non-starter.

Harvesting current and tidal power usually requires rather specific geography in order to have high speeds. The Minas Channel in Canada and Passamaquoddy Bay have some interesting opportunities which are being developed. The total energy from these projects is not as large as you might expect. Neither project, at full development, will produce enough power to satisfy all the state (or province) electrical needs. One of the biggest challenges for any of these tidal current projects is survivability. The devices need to be light enough to produce power on normal summer days yet need to survive winter storms.

Our geography does not lend itself to ocean water-produced electricity, and I doubt we will ever have effective technology to harness our tides.

And that leaves...

Ground-mounted in-water wind turbines to make NH3, unless someone has a better idea. NH3 will probably be the fuel of choice even if other means of capturing energy is used, such as high altitude kites. Suggestions and discussion welcome.

1 comment:

  1. I have been researching energy densities of batteries, and found there is quite a range of published numbers. The 22,000 pound weight for advanced Li batteries is optimistic; more realistic weights would be in the 50,000 to 70,000 pound range. Likewise, the best of the lead batteries may weigh as little as 230,000 pounds. For completeness, since batteries are typically 90% efficient vs. internal combustion engines at 40%, one might divide theses estimated weights in half if the cycle life is not intense.

    Regardless, batteries ("plug-in lobster boats") do not, and will not, be effective. I am not aware of any, even early laboratory theoretical "maybe" nano- ultra-, chemistries (looking out for decades) that come remotely close to being effective for typical commercial fishing.

    Hybrid lobster boats may make sense. Lobster fishing is stop and go with significant secondary power needs for hauling. A hybrid system may allow quick acceleration between pots and provide power for the hauler. It would not help on long, fast runs, such as back to the mainland. The engine powering the hybrid could be fueled with NH3, of course.

    I had heard some one is researching this, but cannot find the link. If anyone knows anything about lobster boat hybrids, let me know.