Wind energy is currently the fastest growing renewable energy resource in the United States. There are, however, only limited locations that have strong enough wind speeds to be suitable as wind farm sites. Throughout the state of Florida there are mostly only Class 1 winds (less than 5.6 m/s), with some Class 2 (5.6 to 6.4 m/s) winds close to the coast. Current wind technology requires a minimum of Class 3 (6.4 to 7.0 m/s) for wind farms to be feasible. Transmission of the electricity produced is a significant contributing factor to the cost of wind power, so minimizing distance is important for economic optimization. Offshore wind offers the advantage of higher wind speeds that are strong enough to be feasible for wind farms, enabling states for which onshore applications are not possible to harness wind power without having to transmit it from neighboring states.
This research analyzed how the implementation of an offshore wind farm for Jacksonville, Florida would compare to that of a natural gas combined-cycle unit and a coal-fired steam turbine power unit with regard to sustainability, global warming impact, and acid rain impact. An emergy analysis was conducted to compare the potential offshore wind farm to a purely coalfired steam turbine power unit, a steam turbine power unit fueled by a mix of coal and petroleum coke, and a natural gas combined-cycle power generating unit. Parameters for comparison 13 included emergy yield ratio, environmental loading ratio, and emergy index of sustainability. A life cycle assessment was also conducted to quantify the respective contributions to the environmental impacts of global warming and acid rain of each power system. The environmental stressors inventoried for quantifying the impacts were carbon dioxide, methane, nitrous oxide, sulfur dioxide, and nitrogen oxides.
The emergy analysis determined that the wind farm had an emergy yield ratio of 11.6, compared to 18.2 for the coal system based on Scherer, 18.8 for the coal system based on St. Johns River Power Park, and 12.4 for the natural gas system. The wind farm’s environmental loading ratio was orders of magnitude lower, i.e. 0.1, while the coal systems range from 13.1 to 15.1 and the natural gas system was found to be 22.4. Similarly, the emergy index of sustainability for the wind farm was found to have an advantageously higher value 121.9, while the coal systems ranged from 1.2 to 1.4, and the natural gas system was found to have a value of 0.6.
Results of the life cycle assessment included that the global warming and acid rain impacts of the wind farm were far lower than those of the fossil fuel-fired systems. The wind farm was found to have a global warming impact of 24 kg CO2 equivalents/MWh, and an acid rain impact of 0.2 kg SO2 equivalents/MWh. The fossil fuel fired systems were found to range from 682 to 1452 kg CO2 equivalents/MWh, and 5.0 to 6.4 kg SO2 equivalents/MWh.