In response to Lee Hamilton’s opinion piece, “Moving away from oil dependency will help Hoosiers” (July 20), I wholeheartedly agree about the need for alternate energy sources. However, those in positions that can help bring about new sources that would be useful in this regard seem to have their minds made up as to what methods are worthy of consideration and which are not. Those who might be willing to chance a relatively small amount of money are carefully shielded from all requests that might be worthy of consideration.

A prime example is cryogenic energy storage. Although proven viable a century ago, those in charge of grants, donations and government programs simply reply, “We have nothing available in that category,” if they bother to reply at all.

Energy can be either stored or created at the point of use. Other than nuclear energy, we are concerned with storing and retrieving energy or retrieving energy already stored in something when we found it. Burning something is merely releasing energy previously stored. In the case of oil, this was a very, very long time ago, in the case of a fuel cell very, very recently.

There is energy storage and retrieval through batteries, which has presently taken on a considerable political significance. There are disadvantages to batteries, including the fact that lithium is fairly rare and the U.S. has almost no proven reserves, leaving us still dependent on importation of something vital to our energy needs.

Batteries weigh as much full as empty, require considerable time to recharge, are quite expensive, have a relatively short useful life and in some cases present a recycling problem.

An excellent case can be made that if we decide to decrease our need for oil, one very promising source of portable energy is the cryogenic storage of the energy in solar, hydraulic, geothermal, wind or even off-peak electricity from the grid for liquefying ordinary air. This seems to come out somewhat ahead of batteries for similar purposes, in spite of the fact that a battery and electric motor system can be more easily used for recharging when braking when adapted for vehicular use.

Advantages of such a system are: There is no shortage of air; exhaust is breathable, ordinary (although cold) air; little or no environmentally objectionable materials are needed to build and operate the system; almost instant recharge through simply pumping or pouring liquid air into a well-insulated tank.

The simplest form of cryogenic energy storage involves simply cooling ordinary air until it becomes a liquid and storing it. Once it is allowed to absorb heat from the atmosphere, it evaporates from a liquid state back into ordinary air at a tremendous increase in volume and pressure. This highly compressed air can run an air motor or steam engine, making it suitable for vehicles that don’t have to be too concerned with weight of fuel. Aircraft and very small motors such as chain saws would not be practical because using them takes very roughly five times the weight in liquid air to produce the power as is available from gasoline

BILL MICHAELS Decatur