Green power taking hold in South Carolina

Green power purchase programs continue to take hold in the United States for a variety of reasons, some of which include more economical and technically advanced methods for harnessing and generating renewable energy, as well as an increased willingness of utilities to address public demand for power produced from renewable energy sources. One of the more popular and cost-effective methods of generating green power is the use of gases produced as a result of natural decomposition of waste at landfill sites.

While capturing landfill gases for use in power generation is nothing new, the sophistication of the gas collection and cleaning systems has evolved over the years. Santee Cooper, South Carolina's state-owned electric and water utility, started its green power purchase program in 2001 with the opening of the 2.2 MW Horry County generating station near Conway, S.C. This was followed by the opening of the 5.4 MW Lee County generating station, dedicated in April 2005 in Bishopville.

And in March of this year, Santee Cooper commissioned a 5.5 MW gas turbine generating station in Richland County. All three projects are fueled by gas from adjacent landfill sites. As the largest power provider in South Carolina, Santee Cooper directly serves more than 150,000 residential and commercial customers in Berkeley, Horry and Georgetown counties and generates the electricity distributed to more than 665,000 customers in all 46 counties by the state's 20 electric cooperatives. Santee Cooper also supplies power to 31 large industries, the municipal utilities in Bamberg and Georgetown, and the Charleston Air Force Base. With a diverse fuel and energy supply that includes predominantly coal-based generating assets, the company also has a mix of nuclear power, hydro power and gas-fired combustion turbines, as well as its nascent green power initiatives.

Green power is offered to residential customers in blocks of 100 kWh each. Because it costs more to produce green power than by conventional means, a $3 premium is charged on a customer's electric bill. Commercial customers are offered green power in blocks of 200 kWh each for a $6 premium.

"We know that the landfill gas is the best option in South Carolina for what's called a renewable energy source," explained Elizabeth Kress, principal engineer of capital projects for Santee Cooper. "We have started with the landfill gas and we have a plan in place to go out to 11 different landfill sites across the state and develop those landfills into projects. We will now have four of the 11 after June."

The state is growing at a tremendous rate, which makes planning for future energy needs critical. South Carolina's population is increasing about 3 to 4% annually and the state is expected to have five million residents by 2025. Santee Cooper's growth rate in its direct serve area has averaged 3% over the past five years.

"We've taken our renewables program in the order of least cost first," Kress said. "We're looking at the other renewable resources out there to see what does make sense. So we're assessing all the resources out there, including other types of biogas, solar and wind, but we know the landfill gas is a good option so Santee Cooper has moved ahead strong with that.

"The premium paid for green power is being used to reinvest into other green power projects."

The Lee County generating facility was recently recognized by the U.S. Environmental Protection Agency's Landfill Methane Outreach Program (LMOP) as a 2005 LMOP Project of the Year. Other team members recognized include GE Jenbacher, the supplier of the generator sets, and Allied Waste, the operator of the landfill. The Lee County plant is expected to grow to 12 units, producing 21.6 MW by 2010. Santee Cooper expects to have a total of 54 MW of green power online by 2012.

The Lee County generating station, Santee Cooper's second green power generating facility, was dedicated in April 2005 and consists of three 1800 kW GE Jenbacher gas engines for a total output of 5400 kW. The LEANOx J616GS gas engines, manufactured at GE Jenbacher's facilities in Austria, drive 4160 V Kato Engineering generators at 1800 rpm through Eickhoff speed increasing gearboxes. The engines have N[O.sub.x] emissions of 0.5 g/bhp-hr under normal operating conditions.

Other major components at the Lee County site include Woodward SPMD synchronizing systems, Thompson Technology generator breakers, SEL generator protection relays, Eaton Cutler-Hammer motor control centers, Silex silencers, radiators from Sutton Stromart and vibration isolators from Getzner. The ExxonMobil Pegasus gas engine lube oil flows through Tranter plate frame heat exchangers.