Giant Aluminum Batteries to transport electricity
Date: Saturday, April 24, 2004 @ 11:49:02 GMT
Cheap electricity from Iceland.
A proposal project by Dr. Pieter van Pelt
Iceland has abundant renewable energy sources such as hydropower and geothermal power. According to a paper [ Address delivered by the Icelandic Minister of Energy and Commerce at “Hydroforum 2000” in München, September 12, 2000] published by the Icelandic Ministry of Energy and Commerce the useable potential for hydropower in Iceland is about 35-40 TWh per year and for geothermal power it is about 15 TWh per year. At present, 25% of potential hydropower is harnessed and about 8% of geothermal power.
This 8.5 TWh per year energy is used in Iceland in various ways. Domestically, 99% of the Icelandic population has connection to the public electrical network, most houses are heated by geothermal power, and a large part of electricity is used in heavy industry such as Aluminum processing, Ferro-silicon production and a large diatomite processing plant at Myvatn. Today, the Aluminum industry in Iceland produces some 270.000 tons of primary Aluminum from bauxite that is being transported from places as far away as New Zealand. New plants and plant expansions will in the near future bring the Aluminum production in Iceland to over one million tons per year. Even then, the potential renewable energy resources will no be completely used for this industry.
The reasons for the success and growth of this power-hungry industry in Iceland are simple: the costs of generating large amounts of electricity in Iceland are low and the end-user markets (where the Aluminum is used for end-products) are fairly near: the USA and Europe.
Transport of electricity from Iceland to Europe.
The transport of bauxite ore to Iceland from far away places such as South America, Australia, New Zealand and other places, the production of Aluminum ingots from this ore by way of an electrochemical process using large amounts of electricity and the transport of these Aluminum ingots to the end-user markets is obviously a profitable business, thanks to the low price of electricity in Iceland.
The transportation of electricity from Iceland to end-user markets such as the USA and Europe is quite another matter. Electricity, unlike Aluminum ingots, cannot be stored in large quantities and is not easily transported over large distances. The investment for electrical power-lines connecting Iceland with Europe are very large, and the power-losses would be huge, making direct transport of electricity from Iceland to Europe economically unfeasible.
Electricity can be transported in different ways, however. One way that is being investigated is by making Hydrogen from water by electrolysis, transporting the Hydrogen in some way (liquefied, under pressure as a gas or stored in metal hydrides) and converting the Hydrogen back to electricity by means of giant Fuel Cells. At present, there are large unsolved problems connected to this way of transporting electricity. The efficiency of electrolysis is about 70% (so 30% of electricity is being lost), the costs of liquefaction of Hydrogen are high and the safety of transporting large amounts of this type of fuel is not guaranteed, Fuel Cells are still very expensive and have efficiencies of 60% at best, so a large amount of electricity will be lost if we were to transport electricity in this way. And the investment costs would be huge.
There may be another way to transport electricity, using the Aluminum battery as a medium. Each kilogram of Aluminum produced represents about 14 KWh of electricity, used to produce the ingots. This means that if we ship 20,000 Tons of Aluminum to Europe, we would be transporting the equivalent of 20,000,000 * 14 KWh of electricity. This is 280 GWh of electricity, enough to power 500,000 households in Europe for a year. The question, of course, is how can we free this electricity from the Aluminum transported.
Here comes the Aluminum battery. Using Aluminum electrodes in a simple electrochemical cell, filled with seawater or Sodium Hydroxide solution and using a Nickel-Manganese counter electrode, the Aluminum will be oxidized to Aluminum Hydroxide and give off 3 electrons per Al atom used up in the reaction. A large part of the electricity stored in the above 20,000 tons of Aluminum can in this way be released, generating about 280 GWh of electricity and about 60,000 tons of Al(OH)3 sludge. This sludge could be recycled back to Iceland to generate again 20,000 tons of Aluminum to start the process of electricity generation anew.
Technically, this should all be very possible to do, but there is a snag. The average price for Aluminum is 1350 Euro/ton (March 2004), so the electricity generated in this way would be minimal 10 Eurocent/KWh. But probably twice as much as cost for Aluminum transport and costs for the batteries, upkeep, personnel etc. are not included. So, simply ‘’burning’’ Aluminum is an economically unfeasible option.
However, instead of ‘’burning’’ the Aluminum in simple electrochemical cells, a rechargeable Al-battery can be used. Such batteries are being developed by Europositron in Finland [www.europositron.com]. They claim the following specifications for their technology:
Energy density : 2100 W.h/litre or 1330 W.h/kgr
Cycle times : 3000+ cycles
Working temperatures : –40 C to +70 C
Lifetime battery : 10 to 30 years
Let’s assume, we equip a large ship with 200 giant batteries, each the size of a 40 foot shipping container. Each battery will weigh about 220 tons, so a 50,000 BRT ship can carry these. The batteries are charged fully in Iceland, making use of cheap electricity from hydropower or geothermal power. The 200 batteries will contain about 50 GW.h electricity when fully loaded. The ship – electrically powered of course – sails to the west coast of Denmark or England, or to the East coast of the USA. There it delivers its electrical charge into the national grid, but it keeps some batteries charged for the return trip to Iceland. It sails back and charges again. It can do so 3000 times before the batteries are worn out and must be replaced. A simple calculation shows that the electricity can be delivered at the end market for a very low price, roughly 20 to 25 Euro per MW.h (substantially below residential rates of 45 to 50 Euro per MW.h).
The trick is, of course, that large quantities of hydropower or geothermal power in Iceland are very cheap (roughly 12 to 15 Euro per MW.h), that transportation of bulk goods over sea is very cheap (hence the economy of processing bauxite ore from New Zealand in Iceland to make Aluminum ingots), and the large investment in Al-batteries has an extended lifetime (3000 or more cycles).
In the Appendix I add a simple cost calculation with reasonable estimates for the various cost factors.
1. Cost calculation Al-battery case:
Aluminium battery case data units formula comment
energy density 2000.0 W.h/ltr
energy density 1200.0 W.h/kg
life cycles 3000.0
battery size 3200.0 ft3
battery weight 217.5 tons assumption 1
battery capacity 260968058.2 W.h
Number of batteries on ship 200.0
ship load batteries 43494.7 tons
electrical capacity of batteries 52193.6 MW.h a
needed for transport @6 days with 20 MW electrical motor on ship 2880.0 MW.h b
net electricity transported 49313.6 MW.h a-b
cost of batteries 4.0 MEuro assumption 2
total costs batteries 800.0 MEuro
costs for vessel 80.0 MEuro assumption 3
total MW.h transported during lifetime 147940834.9 MW.h
battery cost per MW.h transported during lifetime 5.4 Eur/MW.h A 0 value > 3000 cycles
electricity cost per MW.h in Iceland 17.0 Eur/MW.h B assumption 4
operating days for 3000 trips @ 6 days 18000.0 days
operating costs for this time (ship, crew) 56666666.7 Eur assumption 5. Ship: 30 year, crew: Eur 3000/day
operating cost/trip 18888.9 C
total cost for one shipload electricity 1188420.7 Euro C+a*(A+B)
total cost per MW.h net transported electricity 24.1 Eur/MW.h
2. Some data on Aluminum:
See also : http://www.hydrogenappliances.com/Hydrogendata.html
1 gram of Al = 0.0370 moles
Each mole Al yields 3 moles of electrons.
0.0370 moles x 3 x 96500 C/mole = 10700 Coulombs
An Amp is a Coulomb per second, so one Amp flow would last 10700s.
10700 amp-s / 3600 s/hr =~ 3 Amp-Hours per gram of Aluminium.
A 20 lb. slab of Aluminium has enough energy to power an electric car for over 500 miles.
Aluminium is produced by corporations that buy electricity at well under a penny per
KW.h making Aluminium the largest untapped source of potential cheap power.
Aluminium is not expensive because it is rare. It is actually one of the most abundant metals on the earth.
Aluminium is expensive because of the great amounts of electrical power used to refine it.
The energy density of the aluminium/air battery is excellent, even better than the Lithium battery, yet it is not greatly used in practice. The main reason for this is the side reactions that take place between the electrolyte and the aluminium. These involve the corrosion of the aluminium and the production of small amounts of hydrogen gas. This begins as soon as the aluminium is in contact with the electrolyte. The reactions are very slow, but in the time a typical battery might spend in storage before use much harm will have been done. In other words, if the battery is stored with its electrolyte it has a very short shelf life. However, there are applications where the electrolyte can be stored separately, and added when the power is needed. This type of battery is usually called a reserve battery, and is the one market where the aluminium/air battery has had some success.
Large aluminium/air batteries are used as back-up power supplies in many telephone exchanges. When not is use the electrolyte is stored in a tank outside the battery. When there is a power cut it is automatically released into the battery, which starts up. Compared to lead/acid batteries they store about 5 times as much energy in a given volume, and can be recharged by replacing the aluminium electrodes, which in a well designed battery need not be too difficult.