Editorial Comment

	Vol. 227 No. 11
PERRY A. FISCHER, EDITOR

A key enabler. The world seems preoccupied with future energy sources, rightfully so. But the ability to store and transport energy is easily as important, sometimes more so, than the energy itself.

Car engines are inefficient, because they must throttle up and down. If they operated under a constant load, their efficiency would soar. That's also true of electricity generation. The problem with electricity is the difference between peak and base demand. At peak demand, much less efficient means to generate power are used. If a way could be found to store electricity efficiently, the world energy picture would change. There are three or so main ways that electricity is stored.

Pumped-storage hydroelectric involves using electricity to pump water uphill to a reservoir, typically at night. During peak demand, the water is flowed downhill through a turbine to generate electricity. Usually, the pump and turbine are the same unit, only run in reverse. Depending on the evaporation rate and other factors, the system can recover about 70% or so of the electricity stored into it. Despite the loss, it is worthwhile, because of the difference in cost between peak and base electricity demand, and it is the most cost-effective means of storing large amounts of electricity. There are about 300 of these worldwide.

About 33 GWh (5.5%) of the total electrical capacity in the European Union is stored in this way. The US has 19.5 GWh of electricity in pumped storage, including Lundington, on the shore of Lake Michigan. There, the upper reservoir is only 330 ft above the lake, but can store 15,000 MWh of electricity and deliver at a 2,000 MW rate.

A new and interesting variation on this is pumped seawater storage. Wherever there is a shore with some elevated land where a reservoir could be built, pumped storage could be placed. There are many such places in the world. There is one of these on Okinawa, Japan. Another one is under proposal for Hawaii. The problems are corrosion and barnacles, both of which are extremely pesky, but not insurmountable.

Compressed air is another energy storage technique. Air is compressed in an underground cavern during off-peak times and is produced later to meet peak demand. The cavern can be created in salt by solution mining (dissolving with water). Compression is done with an electrically powered turbo-compressor, while expansion is done with a natural gas-powered heater/ expander, which drives a combustion turbine. The process uses only 30 to 50% of the gas normally used for generation. Installations exist in Huntorf, Germany, and McIntosh, Alabama. Another facility has been under development for five years in Norton, Ohio. A 200-MW proposed project in Iowa will use natural caverns and voids for air storage from a wind farm.

Other types of energy storage include flywheels and superconducting electromagnetic fields, but these have quite a way to go for anything but niche applications, so I won't even mention them.

Of course, when you think of electricity storage, you think of batteries. After many decades of development, batteries are finally beginning to achieve the energy density, power density, longevity and cost that are required to usher in an age of electric vehicles and more.

Work at MIT's Laboratory for Electromagnetic and Electronic Systems (LEES) may have made the first technologically significant and economically viable alternative to conventional batteries in more than 200 years. Although ultra-capacitors have been around since the 1960s, they are relatively expensive and only recently began being manufactured in sufficient quantities to become cost-competitive. Like their name implies, they store and discharge energy, but over a much shorter period of time than a battery.

They are ideal for regenerative braking systems in fuel-cell vehicles, due to the high-power transfers of short duration in braking and accelerating. They have some nice advantages over batteries – more than a 10-year lifespan, temperature tolerant, high charging and discharging efficiency – but until now, they held 25 times less energy than a similarly sized lithium-ion battery. The breakthrough in the LEES ultra-capacitor comes from using vertically aligned, single-wall carbon nanotubes, which overcome the energy density limitation.

Nanotube-enhanced ultra-capacitors have the potential to combine the long life and high power of a commercial ultra-capacitor with the higher energy storage density normally available only from a chemical battery.

Another potential step-change in battery development comes from a small company called Altair Nanotechnologies. The new battery uses nano-titanate material in place of graphite as the negative electrode in a conventional lithium ion battery. By doing this, the company says that no interaction takes place with the electrolyte, which is what causes the overheating that is common in lithium ion batteries. This results in an inherently safe battery capable of high-rate overcharge, a potential 20+ year life with a wide operating temperature range (60°F to 165°F).

The company says that it has, along with its partners, Phoenix Motorcars and Boshart Engineering, an electric SUV (as well as a truck version) powered entirely by new "environmentally friendly batteries." The vehicle has a standard range of 130 miles, a charge time of 10 minutes, and is capable of speeds up to 95 mph.

What's "driving" the electric car is energy independence for oil importers and environmental concerns, but for consumers, it's the cost of an equivalent "electric" gallon of gas, which is less than a $1.00. Of course, money is money, meaning, the cost of the vehicle, drive train, energy storage system and so on have to be figured in. But remember, plasma televisions cost about $25,000 in 1997. Today, you can buy one for less than $1,200. So there's reason for optimism.

The Northern Plains states are the US' equivalent of Saudi Arabia in terms of wind. North and South Dakota, alone, could supply, in theory, half of the US' electricity needs. Wind is now the cheapest source of new power. OK, so you'd have to put up thousands of giant windmills in western North and South Dakota – but so what? Only 12 people live there, and they're losing population! And yes, it would not be easy to move the energy to the East or West, but advances in HVDC and other technologies can get that energy transported at an acceptable loss.

The world is going to need double, and eventually triple, the energy we now use. Storage will play a key role. It is an enabler.

Land in western North Dakota is cheap. Start buying now.