Krellite cells are the super battery that everyone has been dreaming about. One cell the size of three lead acid car batteries can power a car from one end of the country to the other without rehanging. A cell in a standard smart phone can power it for a month. They have the energy density to make directed energy weapons like the phaser possible.
The Krellite cell was a development out of the Galan Database with more than a few hints supplied by the robots that Helenanna brought with her. They had cells that could be studied and reverse engineered. The right clues from the database and the problem was cracked. Combined with the fusion reactor and the energy problem is over.
One result of the Krellite cell (A name suggested by the Galan database.) is that the internal combustion engine is dead. They finally have a battery that has the density to power a car with an improved range and no performance penalty. Within five years of their introduction only two companies are still making cars that burn gasoline. Both of them are fringe markets. Cross country trucks are now 24/7 mobile houses with all the comforts of home. Driver teams can keep a truck running around the clock. Maintenance on the all electrical systems are minimal. No one can afford to keep a diesel truck on the road and make money.
Phasers are also a result of the krellite cell. A standard phaser would drain any battery that would fit in it in one shot. With the much higher energy density it is possible to have phasers that can last a while.
Mobile computing has become the standard. Any computer can be powered for weeks of use on one battery.