The Kalina Cycle, invented back in the mid-1980s as an alternative to the conventional Rankine Cycle, and promoted as a potential replacement for large-scale steam boiler systems, may finally be finding its market entry point at the other end of the spectrum. Four small-scale power plants have installed commercial Kalina Cycles in recent years, generating more than 6 million kWh of electricity to date.
The Kalina Cycle uses a binary working fluid of an ammonia-water mixture to drive a turbine-generator. By varying the composition of the binary fluid, variable vaporization and condensation points are achieved with the result that thermal energy is captured more efficiently per unit of fuel input (see figure), creating a higher cycle efficiency. The plants currently in commercial operation have demonstrated efficiency gains of 15-50 percent relative to conventional thermal technologies, along with 15-20 percent lower emissions of NOx, SO2and particulate matter as a result of less fuel being consumed, according to Mark Mirolli, president of Exergy Inc., which owns the rights to the technology.
Various power plant design configurations can accommodate the Kalina Cycle. The four commercial applications include a combined-cycle facility, a waste-to-energy plant, a waste-heat power plant and a geothermal power plant. The range of heat source temperatures varies between 208 F and 1,652 F, with turbine throttle conditions of 435-1650 psig.
The first fully commercial Kalina Cycle plant is a waste heat application in Kashima, Japan. The Sumitomo Steel power plant produces 3.1 MW net electricity using 208 F hot water as its heat source. The project has been in operation since July 1998 and has demonstrated an availability of more than 98 percent.
In Husavik, Iceland, a distributed generation plant based on the Kalina Cycle came on-line in July 2000. The plant is designed to produce 2 MW net using a geothermal brine flow of 200 lb/s at 255 F. The brine temperature has only averaged about 248 F, however, so peak power production has only reached 1.8 MW.
Advanced Thermal Systems, which owns the U.S. licensing rights to the Kalina Cycle for geothermal applications, is developing a 40 MW geothermal facility at the Steamboat Geothermal Energy Park south of Reno, Nevada that will use Kalina technology. Scheduled for commercial operation in late 2003, the Steamboat IV facility is expected to produce power at less than 4 cents/kWh, competitive with all other baseload technology options. Geothermal project opportunities are particularly attractive because they currently enjoy favorable tax advantages and because long-term O&M costs should be relatively stable (since fuel cost fluctuations are minimal). With 23,000 MW of undeveloped geothermal power potential identified in the western United States, a clean, affordable, renewable energy program using low cost, zero-emission Kalina geothermal power plants is now possible and could significantly improve the region’s power situation.
Natural gas compressor stations represent another promising commercial opportunity. Exergy’s Mirolli identifies more than 4,000 MW of Kalina waste heat power plants that can be retrofit on existing gas turbine capacity at natural gas compressor stations. These plants will produce electricity from waste heat with zero-emissions. The electricity produced could be put back on the grid and/or used by nearby consumers.