Powering up and cooling down in Florida

A network of steel pipes and tanks tucked behind a small building at the University of Florida could lead to a new method of creating electricity and refrigeration.

The pipes and tanks are the guts of a recently launched experiment to test what Yogi Goswami; a UF professor of mechanical engineering describes as a novel solar – or geothermal -powered thermodynamic cycle.

‘We’ve seen that it works in theory, and we’ve set up this experimental system to prove that it works in practice,’ said Goswami, a specialist in solar energy who is also a director of UF’s Solar Energy & Energy Conversion Laboratory.

The system will attempt to verify what Goswami describes as a new combination of two thermodynamic cycles: the Rankine, or steam cycle, and the absorption-refrigeration cycle.

In Goswami’s experimental set-up, hot water is used to heat pressurised ammonia past its boiling point, generating ammonia steam.

This is said to be possible because ammonia maintained at the pressure required to spin a turbine boils at around 212 degrees Fahrenheit.

The next step is for the pressurised ammonia vapour to spin a turbine and produce electricity (a process simulated in the experiment through using a heat exchanger and expansion valve). As the ammonia spins the turbine, it falls below room temperature, reaching lows of 32 degrees or lower, which is cold enough to make ice. The result could be used for refrigeration or air conditioning.

Theoretically, the hot water would come from deep underground or solar collectors, although for the purposes of Goswami’s experiment a household hot-water heater has been used.

‘The unique thing we’re doing is that we can remove so much of the energy from the ammonia in the turbine that it actually becomes very cold,’ Goswami said. ‘We can then use that cold gas to our advantage for air conditioning or to create ice.’

Goswami said his system is more economical than systems that have gone before it because it can use off-the-shelf collectors.

Although it could be used on a large scale, the system would be ideal for homes that could easily take advantage of both the electricity and the refrigeration, he said.

Another application for the technology could be to extract additional energy from the hot wastewater produced by conventional power plants.

Even the most efficient power plants are said to capture 30 to 40 percent of the energy in the fuel, releasing the bulk of the remainder in the form of heat.

Goswami said his system, installed on the outlet pipes for the hot water, could leach 20 to 30 percent more energy from the system while also cooling down the water. As a result, the plant could generate extra electricity while gaining cooling capability for on-site refrigeration or air conditioning needs, concluded Goswami.