Solar Engine Turns heat into Power

Solar Engine Whips Waste Heat Into Power
Tracy Staedter, Discovery News

Every Photon Matters

Jan. 25, 2008 -- A new engine with no moving parts has been shown to convert waste heat and concentrated solar energy into electricity better than conventional solar panels.
The invention could lead to electricity generators ranging in size from the very large, such as those used by utility companies, to the very small -- such as those that tap body heat to generate power for personal electronics.
Because the conversion rate is so high, the technology could make solar energy cheap enough to compete with fossil fuels.
"It's not just the dependence on oil, it's the whole challenge of providing energy that is sustainable without destroying the environment," said nuclear engineer Lonnie Johnson, founder of Johnson Research and Development and Johnson Electro-mechanical Systems, both in Atlanta.
Johnson is funding his research with money he made by inventing the super soaker squirt gun. His new, somewhat less cavalier, invention is called the Johnson Thermo-Electrochemical Conversion System.
The original goal, in part, was to address a common problem with energy: When it's generated -- by gas, coal, battery, or other means -- much is wasted into thin air. In fact, in the United States alone, the amount of energy lost is more than the energy consumed by the entire country of Japan.
Johnson's engine captures that heat and turns it into useful power.
It's called an engine because it's based on thermodynamic principals that exist in mechanical engines, such as those that power automobiles. In a car engine, moving pistons and rods compress gas at low temperatures and expand it at high temperatures to convert heat energy to mechanical energy to drive the vehicle.

In Johnson's energy-converting system, electrodes on a thin membrane compress hydrogen gas at low temperatures and expand it at high temperatures. The pressure forces hydrogen ions through the membrane, stripping off electrons to generate power.
And although the system uses hydrogen, it does not burn it the way a hydrogen fuel cell would. It simply re-circulates the same quantity over and over.
"This is a whole new way of converting temperature differences to electricity that has never existed before," said Paul Werbos, program director for power, control and adaptive networks at the National Science Foundation in Arlington, VA..
If it works, it could be far more efficient than the best solar cells, which convert about 30 percent of sunlight into energy.
Johnson's system could reach 60 percent. But for that to happen, it needs to operate with very high temperatures, upwards of 1,400 degrees Fahrenheit (800 C).
Achieving that temperature will be a challenge, said Werbos.
"They will need new membranes and electrodes, and they will have to prove that they are handling the hydrogen correctly," said Werbos.
So far, the researchers have built a device that works at 392 degrees F. Johnson hopes to have demonstration model working at 1,400 degrees in a year to 18 months.