The government is on the verge of giving the infant solar electric industry the same kind of calculated boost into the major leagues that it once gave nuclear power.

Since their invention in 1955, solar power cells have moved steadily downward in price and upward in efficiency to the point where industry leaders say they must automate production in order to produce them cheaper. Legislation now pending would provide the large, guaranteed market - in the form of government purchases - that the solar power people say they must have to justify assembly line investments.

A floor fight in expected in Congress this week over an amendment by Rep. Paul Tsongas (D-Mass.) that would authorize $28 million for government purchase of solar cell equipmnt in fiscal 1980. That means about 4,000 kilowatts worth at prevailing prices, or more than four times the current national solar cell production.

If that amendment fails - and it faces strong administration opposition - another House bill provides $39 million in Senate yersion would spend $98 billion in contracts for fiscal 1978-81 while a Senate yersion would spend $98 million.cleary solar electricty's time a nigh.

"We need this to push us to another level," said Dr. Joseph Lindmayer, a pioneer in solar cell research and president of Solarex, a Rockville firm that claims 40 per cent of the silicon cell market.

Like virtually anyone close to solar cell technology he and other industry figures claim the future is theirs no matter what Congress does or does not do. It will only get here sooner if the government plalces some orders big enough to get things automated now, they argue, rather than later on.

"There is so much energy in the sunlight falling on one square yard of earth that one-tenth of it can light up a 100-watt bulb. When the power is not caught for bulb-lighting or other purposes, it turns into heat, and that is why things get warm in the sun.

The thought of all that electricity goes to waste out there every day has lit up the eyes of the solar power advocates a stubborn handful of vision-aries, for years. Soundlkess, pollution-free maintenance, free with no moving parts and using the endless free fuel of sunlgiht solar power has only two problems: darkness and cost.

The first is statistically predictable and so is merely "a number game," according to Lindmayer. Cloudy days and nightime can be easily bridged, he said, with the correctly figured size of solar cell panel and battery storage units. A $5 million to $8 million experimental solar-powered junior college to be built at Blytheville, Ark., is expected to use a new kind of reduction-oxidation (redox) battery system that claims to cost one-fifth as much as conventional batteries.

The second problem has been harder to solve. Converting sunlight to electricity is a more complex process than merely using it to heat water and homes. Which is complex and expensive enough.

The most common method but by no means the only one, uses wired-together ultra-thin wafers of silicon, which is the second most abundant element in nature and makes up one-quarter of the earth's crust. Silicon is the shiny part of sand, but even so it is not cheap.

It has to be purified and repurified as it is artificially grown into a cylinder-shaped cystal. The cylinder is then sliced, much like a sausage, into wafers that - if the silicon is pure enough - are free of impurities that would stop the flow of electricity across the surface.

Each water of silicon is then baked with chemicals so that a top layer is negatively charged and that a bottom layer is positively charged. When light hits the top layer, the bombardment "loosens" the molecular structure so that free electrons (electricity) flow from the positive side through the wires to the negative side.

Most of this is done step-by-step by hand, and rows of workers solder the completed discs together into the arrays of rows that make a solar cell display. Other techniques use cadmium sulfide or gallium arsenide or materials, and still others use lenses and motors and mirrors to focus the sun more brilliantly and to track its rays.

When all this started, at Bell Labs in 1955, the devices cost about $600 for every watt of electricity produced, or $6,000 to light a 100-watt bulb. For years their only use was in the space program, to power satellites.

As the price came down, the cells began turning up in remote earthly locations where stringing wires or running gasoline generators would be all but impossible: ship's buoys, desert or mountain radio relay sites, Arctic signal beams, jungle airstrip lights. Government demonstration projects have included power for a massive irrigation pump operation in Meade. Neb., as well as for the emergency call boxes along the Capitol Beltway's Marryland portion.

Now the price is down to about $15 a peak watt (power produced in full sun), which translates to about $1.50 a kilowatt hour. Pepco charges 4 cents a kilowatt hour. The Energy Research and Development Administration (ERDA) sees 50 cents per peak watt as a reasonable solar power goal for 1986, and 20 to 30 cents as competitive with Pepco and other existing generating systems. Given savings in air pollution, fuel, transport and other conventional power costs.

That is why many energy experts have relegated solar power to the long-term solution category. In addition, there still is little agreement on the best kind of solar cell technology, with new materials and techniques being developed and tested constantly. Opposition to committing government funds now has focused on that.

"There's no way to legislate a technology into being," said Rep. Mike McCormack (d-Wash.), chairman of the advanced energy techologies subcommittees that will oppose any major buys this year. "The industry is still in its infancy . . . and doesn't have the fabricating capacity it would need."

ERDA solar cell division director Dr. Morton Prince, who developed the devices in the 1950s, said a big purchase in fiscal 1978 "would be too fast to allow the automation to take place. Only if the industry sees long-term, stable demand will that happen."

The government deliberately created such a demand for nuclear power equipment in the 1950s in order to stimulate that industry, several scientists said.

Lindmayer rejected as "nonsense" the possibility of inadequate production capacity. "We're already doubling capacity every year,"he said. "This would be a challenge."

A Federal Energy Administration study, still in draft form, estimated a government investment of $500,000 in solar cells could result in a gross savings of $2 billion over 25 years to the Defense Department alone, which has some 214,000 small generators now pumping away in remote sites. "This would not be a charity case," a Senate staff enthusiast said.

Asked whether a big government buy might freeze things at the current technology, the U.S. Office of Technology Assessment said experience gained and private market expansion would lead to new technology anyway. "The potential market is so enormous," said Lindmayer, "that there will be room in it for everybody."