GE FlexEfficiency 50 CCGT Facilities and Wind Turbine Facilities
- June 21, 2011
- 555 views
Historically, electric grids have experienced varying electric demands during a day and varied the output of their generating plants to serve that demand and, at the same time, regulate frequency. Increased wind energy penetration will present additional challenges to the management of the energy on the New England Electric Grid, NEEG.
Because wind energy is variable and intermittent, additional spinning and backup plants, such as a mix of open cycle gas turbines, OCGTs, and combined cycle gas turbines, CCGTs, must be kept in 24/7/365 operation to supply and withdraw energy as required. The plants must respond to changes of:
– demand of millions of users during a day.
– supply, such as from unscheduled plant outages.
– supply due to weather events, such as lightning, icing and winds knocking out power lines.
– supply from wind turbine facilities.
If these changes, especially those due to wind energy, are of high megawatt/minute, the CCGTs may have to temporarily operate as OCGTs, because their heat recovery steam generators, HRSGs, would be damaged by rapid cycling; HRSGs have lower ramp rates than OCGTs. This increased OCGT mode of operation increases fuel consumption, NOX and CO2 emissions per kWh.
New GE CCGT Plant
GE is marketing a new CCGT plant and has sold a few of them. The new “GE FlexEfficiency 50” plant has a capacity of 510 MW and a 61% efficiency at rated output. Its design is based on a unit that has performed utility-scale power generation for decades. The plant fits on about a 10-acre site.
It is quick-starting: from a cold start, it reaches its rated output in about one hour. Various options are available to reduce the start up times to as little as 30 minutes.
Its average efficiency is about 60% from rated output to 87% of rated output (444 MW) and about 58% from 87% to 40% of rated output (204 MW). It can be ramped at 50 MW/minute.
Without wind, the GE unit is designed to efficiently produce electric energy in base-loaded mode and daily-demand-following mode.
With wind, its high ramp rate enables it to also function as a cycling plant to accommodate the variable energy from wind turbine and solar facilities, albeit at reduced efficiency. Below 40% of rated output its efficiency decreases rapidly, as with all gas turbines. This means its economic ramping range is limited.
It would be a travesty to misuse and abuse such an advanced CCGT for wind and solar energy balancing.
Selected Levelized Energy Costs
The US Energy Information Administration projects levelized production costs (national averages, excluding subsidies) of NEW plants coming on line in 2016 as follows (2009$) :
Offshore wind $0.243/kWh, PV solar $0.211/kWh (higher in marginal solar areas, such as New England), Onshore wind $0.096/kWh (higher in marginal wind areas with greater capital and O&M costs, such as on ridge lines in New England), Conventional coal (base-loaded) $0.095/kWh, Advanced CCGT (base-loaded) $0.0631/kWh. http://www.energytransition.msu.edu/documents/ipu_eia_electricity_genera...
SUMMARY OF STUDY RESULTS
Various aspects of wind energy on the NEEG, including capital costs, fuel requirements and CO2 emissions reduction were studied. A comparison of the two alternatives was made. In this section are summarized the main results of the study.
Wind Turbine Facility Plus Cycling Facility
Capital cost of CCGT + Wind = $637,500,000 + $500,000,000 = $1,137,500,000
Net NEEG CO2 emission reduction = 802,571 metric ton of CO2/yr
CO2 emission reduction cost = $1,417/metric ton of CO2/yr
Fuel cost = 92,374,140/yr
CCGT Facility Only
Capital cost of CCGT = $637,500,000
Net NEEG CO2 emission reduction = 701,363 metric ton of CO2/yr
CO2 emission reduction cost = $909/metric ton of CO2/yr
Fuel cost = $99,986,353/yr
Comparison of CCGT + Wind versus CCGT Only
Cost of CO2 emissions reduction: CCGT + Wind is 55.9% greater than CCGT Only
Cost of Owning (excluding subsidies): CCGT + Wind is about 78.4% greater than CCGT Only
Cost of O&M fuel component: CCGT + Wind is $7,612,213/yr, or 7.6% less than CCGT Only
Cost of Other O&M (as a % of capital cost): CCGT + Wind is 78.4% greater than CCGT Only
Useful service life of wind facility is about 25 years versus 35 – 40 years for the CCGT facility
Some of the advantages of gas-fired CCGT are:
– No grid modifications would be required
– No inefficient operation of gas-fired wind energy balancing facilities would be required
– Impacts on quality of life (noise, visual, psychological and health), property values and the environment would be minimal
– The facility would take up only a few acres
– The electrical energy would be low-cost, steady 24/7/365, reliable and dispatchable
– Low CO2 emissions/kWh; about 1/3 the CO2 emissions/kWh of coal plants
– No particulate emissions
– Domestic energy supply, good for energy independence, national security
Conclusions and Recommendations
Whereas the CCGT facility will improve the economics and reduce the operational difficulties of accommodating wind energy to the grid, the combination of this high-efficiency CCGT facility with a moderate-efficiency wind turbine facility will be less efficient than the CCGT facility in base-loaded mode and daily-demand-following mode.
The wind turbine facility contributes just 543,120/4,467,600 x 100% = 12.2% to the total electrical production, but adds 500,000,000/1,137,500,000 x 100% = 44% to the capital cost and adds 1,417/909 x 100% = 55.9% to the cost of reducing CO2 emissions.
The 2.5 MW and 3 MW units are about 390 to 415 ft tall to the tip of the blade, respectively, which would appear very large if the ridge line is at 2,000 ft elevation and a person’s house is at 1,000 ft elevation and within a mile of a row of wind turbines; at night there would be an unsteady beat of whoosh sounds. Wind turbines are often made to look small on distant ridge lines using Adobe’s Photoshop software. Quality of life (noise, visuals, sociatal unrest/opposition), property value and environment are negatively impacted over a large area.
CCGT facilities are significantly more effective than wind turbine facilities for reducing CO2 per invested dollar and for reducing the cost of electricity per kWh. The production of energy by the GE FlexEfficiency 50 CCGT facility has a levelized cost less than $0.0631/kWh, whereas energy by a wind turbine facility in New England has a levelized cost greater than $0.096/kWh, i.e., at least 52% greater.
Instead of subsidizing poorly performing wind turbine facilities, the subsidies should be for advanced CCGT facilities to accelerate their installation throughout the USA in large numbers and to replace aging, inflexible, polluting coal-fired plants that emit at least 2.15 lb of CO2/kWh versus 0.655 lb of CO2/kWh emitted by advanced CCGT facilities, i.e., 3.28 times less.
Those subsidies would be similarly effective if used for increasing energy efficiency that would use mostly US materials and US labor and create jobs all over New England, instead of in Denmark (wind turbines), Spain (wind turbines), Germany (PV inverters) and China (PV panels).
Global Warming and Wind Politics
The PR message for wind turbine facilities is for vendors, developers and financiers to get as much federal and state subsidies as possible and have that money, plus private investment, course through a state’s economy to create jobs, make the US energy independent and combat global warming. What is not to love?
The hitch is the money is invested in subsidized, uneconomic projects that will ultimately make a state’s economy less efficient for the production of goods and services and thereby lower standards of living; it is similar to shooting oneself in the foot when running to keep up with other nations.
Another hitch is we live in a world distorted by coalitions of legislators and special interests in which renewable energy is treated as an end in itself and given preferences, such as renewable portfolio standards, must-take provisions, accelerated depreciation, tax credits, cash grants, low-interest loans and, in some jurisdictions, generous feed-in tariffs.
Accordingly, the grids will likely have to continue the complicated and costly efforts of accommodating increasing quantities of expensive, variable, intermittent renewable energy, regardless of whether more capable technologies, such as advanced CCGT facilities, that require:
– no such complicated and costly efforts
– generate electricity at a significantly lower cost per kWh
– reduce CO2 emissions at a significantly lower cost per metric ton.
Legislators need to pay less attention to the PR of renewables vendors, developers and financiers and re-examine the people’s priorities before providing continued subsidies for wind facilities, which are such obviously poor investments and have such an everlasting, undesirable environmental impact on what are now mostly pristene ridge line areas. Wiser minds should prevail and stop this subsidy-driven, mad rush to New England’s ridge lines before it is too late.
STUDY PURPOSE AND APPROACH
The purpose and approach of this study is to:
– evaluate 2 alternatives: one consists of a 510 MW CCGT facility plus a 200 MW wind turbine facility, the other consists of only the CCGT facility. An average efficiency of 58% was assumed for the cycling range of 310 MW to 510 MW.
– determine the capital cost of the alternatives, the production, MWh/yr, and the emissions, metric tons of CO2/yr, and compare them.
If the wind turbine facility capacity were significantly increased beyond 200 MW, the CCGT facility would operate at lesser efficiencies, i.e., increased fuel/kWh and increased pollution/kWh, and the CO2 emissions reduction due to wind would become less and less, until it becomes zero and then becomes positive.
CCGT heat rate = 3,413 Btu/kWh/efficiency 0.58 = 5,884 Btu/kWh*
CCGT heat rate = 3,413 Btu/kWh/efficiency 0.61 = 5,595 Btu/kWh; base-loaded
CO2 emission = 117 lb of CO2/(million Btu x 1 kWh/5,884 Btu/kWh) = 0.688 lb of CO2/kWh
CO2 emission = 117 lb of CO2/(million Btu x 1 kWh/5,595 Btu/kWh) = 0.655 lb of CO2/kWh; base-loaded
Utility long-term contract fuel cost is assumed at $4/1,000,000 Btu
NEPOOL average marginal CO2 emissions about 1.0 lb/kWh
* The 58% stated by GE is for base-load/load-following mode. The CCGT ramps up and down at least 100 times a day to accommodate varying wind energy, whereas in base-load/load-following mode ramping up and down may occur only a few times a day.
The rapid ramping will increase the heat rate, Btu/kWh, and CO2 emissions, lb of CO2/kWh.
For example: a car driven on a level road at a steady speed of 40 mph has a mileage of, say 26 mpg. The same car driven on a level road at irregular and rapidly changing speeds that average 40 mph has a mileage of, say 22 mpg. The mileage degradation due to the speed changes would be (26-22)/26 x 100% = 15%. A car’s best mileage usually is at 55 mph, at a steady speed, on a smooth, level road; it is the oft-quoted EPA highway mileage.
A New England average CF = 0.31 was chosen because early installed wind turbine facilities would likely be on ridge lines with higher CFs, such as facilities in western Maine which have an average CF = 0.32, whereas later installed facilities would be on ridge lines with CFs of 0.30 or less. http://www.coalitionforenergysolutions.org/maine_wind_farms.pdf
The New England average CF = 0.31 may prove to be very optimistic, because large geographical areas rarely have capacity factors greater than 0.30. For comparison: Western Ireland (0.323 for the 2002-2009 period, the best in Europe), UK (0.282 for 1998-2004), Texas (0.258 for 2009), Denmark (0.242 for the 2005-2009 period), the Netherlands (0.186), Germany (0.167). It would not be credible to aver onshore wind speeds in New England are comparable to onshore wind speeds in western Ireland, one of the windiest areas of Europe.
An installed capital cost of $2,500,000/MW was chosen for this study. It is the same as the average of the capital costs of the recently installed operating and planned wind turbine facilities in Maine and less than the $2,778,000/MW of the Granite Reliable Power Windpark, Coos County, NH, consisting of 33 Vestas units @ 3 MW each. http://www.coalitionforenergysolutions.org/maine_wind_farms.pdf
CCGT facility about 510 MW x $1,250,000/MW = $637,500,000
Wind turbine facility, on New England ridge lines, about 200 MW x $2,500,000/MW = $500,000,000
PRODUCTION, FUEL COSTS, CO2 EMISSIONS
CCGT + Wind
Capital cost CCGT + Wind: $637,500,000 + $500,000,000 = $1,137,500,000
Wind turbine facility production: 200 MW x 8,760 hr/yr x capacity factor 0.31 = 543,120 MWh/yr
CCGT facility production: (510 – 0.31 x 200) MW x 8,760 hr/yr = 3,924,480 MWh/yr
Total production: 543,120 + 3,924,480 = 4,467,600 MWh/yr
Net NEEG CO2 emission reduction = 1.0 x 543,120 x 1,000 x 1/2,200 + (1.0 – 0.688) x 3,924,480 x 1,000 x 1/2,200 = 802,571 metric ton of CO2/yr
Fuel cost: 3,924,480 x 1,000 x 5,884 x $4/1,000,000 = $92,374,140/yr, or $0.0207/kWh
Capital cost/Net NEEG CO2 emission reduction = 1,137,500,000/802,571 = $1,417/metric ton of CO2
Capital cost of CCGT Only: 200 MW x $2,500,000/MW = $500,000,000
CCGT facility production: 510 MW x 8,760 hr/yr = 4,467,600/yr
Net NEEG CO2 emission reduction = (1.0 – 0.655) x 4,467,600 x 1,000 x 1/2,200 = 701,363 metric ton of CO2/yr
Fuel cost: 4,467,600 x 1,000 x 5,595 x $4/1,000,000 Btu = $99,986,353/yr, or $0.0224/kWh
Capital cost/Net NEEG CO2 emission reduction = 637,500,000/632,603 = $909/metric ton of CO2
INCREASED ENERGY EFFICIENCY
The real issue regarding CO2 reduction is energy intensity, Btu/$ of GDP; it must be DECLINING to offset GDP and population growth. To accomplish this energy efficiency needs to be at the top of the list, followed by the most efficient renewables of which hydro power is the best and residential small wind is the worst, in fact, it is atrocious. EE is so good that it should be subsidized before any and all renewables, because it is much more effective per invested dollar.
Effective CO2 emission reduction policy requires that all households eagerly participate. Current subsidies for electric vehicles, residential wind, PV solar and geothermal systems benefit mostly the top 5% of households that pay enough taxes to take advantage of the renewables tax credits, while all other households are required to pay for them by means of fees and taxes or higher electric rates; the net effect is much cynicism and little CO2 reduction. Improved energy efficiency policy will provide much greater opportunities to many more households to significantly reduce their CO2 emissions.
Energy efficiency will have a much bigger role in the near future, as energy system analysts come to realize that tens of trillions of dollars will be required to reduce CO2 from all sources and that energy efficiency will reduce CO2 at a lesser cost and more effectively. Every household can participate.
Energy efficiency projects:
– will make the US more competitive, increase exports and reduce the trade balance.
– usually have simple payback periods of 6 months to 5 years.
– reduce the need for expensive and highly visible transmission and distribution systems.
– reduce two to five times the energy consumption and greenhouse gas emissions and create two to three times more jobs than renewables per dollar invested; no studies, research, demonstration and pilot plants will be required.
– have minimal or no pollution, are invisible and quiet, something people really like.
– are by far the cleanest energy development anyone can engage in; they often are quick, cheap and easy.
– have a capacity factor = 1.0 and are available 24/7/365.
– use materials, such as for taping, sealing, caulking, insulation, windows, doors, refrigerators, water heaters, furnaces, fans, air conditioners, etc., that are almost entirely made in the US. They represent about 30% of a project cost, the rest is mostly labor. About 70% of the materials cost of expensive renewables, such as PV solar, is imported (panels from China, inverters from Germany), the rest of the materials cost is miscellaneous electrical items and brackets.
– will quickly reduce CO2 at the lowest cost per dollar invested AND make the economy more efficient in many areas which will raise living standards, or prevent them from falling further.
– if done before renewables, will reduce the future capacities and capital costs of renewables.