- Need for lower-cost alternative to diesel fuel
- Difficulty finding technology capable of burning LPG efficiently
- Growing generating capacity needs
In 2012, diesel fueled more than 95% of the U.S. Virgin Islands Water and Power Authority’s (WAPA) generating capacity. After experiencing large fluctuations in spot prices during the previous decade, WAPA began to evaluate alternative fuels for power generation. In 2013, WAPA decided to shift much of its generating capacity to liquid petroleum gas (LPG), citing its lower cost and reduced emissions. The next step would to find a proven technology that could burn the fuel and be installed quickly but would not suffer the same de-rate in efficiency as reciprocating engines running on LPG.
In late 2016, WAPA awarded APR Energy – which has operated a 25MW diesel-powered turbine on the island of St. Thomas since 2012 – a contract to provide an additional 25MW of generation fueled by LPG. The project features a modified GE TM2500+ mobile gas turbine, which will become the first ever to be commercially operated on LPG (with the ability to switch to diesel in the event of propane supply disruptions). The project posed several challenges, including the need to squeeze the turbine and exhaust system into existing plant infrastructure that offered just 4-5 inches of space to maneuver the equipment. The prototype project required field testing and validation of the converted turbine and new operating software prior to commissioning, and APR Energy’s engineers modified the vaporizer system during installation for more efficient conversion of liquid fuel into gas. Finally, since LPG is a more volatile fuel than diesel, additional concrete footings were installed to better support the vaporizer and ensure the structure met seismic requirements.
In early 2017, APR Energy commissioned its second plant for WAPA, and it will become the world’s first mobile gas turbine to operate commercially on LPG. Since fuel accounts for approximately 70% of the cost of power generation, WAPA expects to save millions of dollars a year by converting to LPG, which should remain relatively stable in price while experts forecast a 15% cost increase for diesel through 2019. WAPA also is benefiting from significantly lower emissions – including a 94% reduction in NOx emissions compared with diesel reciprocating engines typically found in the temporary power market – which is important to its tourist-based economy. The viability and attractiveness of LPG-fired generation has been affirmed by WAPA, which in early 2017 extended the initial agreement from 12 months to 24 months and contracted APR Energy to install a second LPG turbine at the end of 2017.