Keith Li, PE Controller NRG Energy Center Harrisburg LLC

Transcription

1 Modernizing a 100-Year Old Steam System Keith Li, PE Controller NRG Energy Center Harrisburg LLC

2 Executive Summary NRG Harrisburg s district energy system has served Pennsylvania s capital city, Harrisburg, PA, for more than 100 years. Over the past century, the operation has evolved from a coal-fueled steam plant to a multiple-facility, multi-fuel district energy system. Today s higher fuel cost and push for energy independence are driving factors for the following NRG investments included in this presentation. Efficiency - Economizer, deaerator, instrument air compressor, decarbonator, boiler feed pumps and variable frequency drives Water Conservation Condensate return and water softeners Alternative fuels Biodiesel and wood biomass

3 Harrisburg District Energy History Hydroelectric Plant Coal-fired boilers (electric) Coal-fired boilers (electric & steam) Oil-fired boilers retired coal boilers Dual fuel Cogeneration Natural Gas fired boilers Chilled water plant Wood biomass CHP??

4 NRG Harrisburg Historical Archive Item Picture of Horse Falling into Steam Line Trench (circa 1900)

5 NRG Harrisburg Steam Plant Four boilers - 400,000 lb/hr capacity Fuel - No. 6 oil & Natural Gas (two 1-million gallon tanks) Distribution - 7 miles of steam main Two 200-foot stacks Staffing - 28 people (operations, maintenance, and administration) for three facilities

6 NRG Harrisburg Steam Plant

7 NRG Harrisburg - Cogeneration Plant Two Diesel Engines - 16,000 Hp (12 MW) Fuel - No. 2 oil & Natural Gas Heat Recovery - 30,000 lb/hr capacity Grid Interconnection Staffing unmanned plant

8 NRG Harrisburg - Cogeneration Plant

9 NRG Harrisburg Cooling Plant Three Centrifugal Chillers ton capacity Leased property Distribution miles of CW main Staffing remote operation

10 NRG Harrisburg Cooling Plant

11 Efficiency and Sustainability Investments Steam Plant - Economizer/Deaerator Steam Plant - Variable frequency drives, Decarbonator, Water softeners, Instrument air compressor Cooling Plant - VFD Chiller Steam Plant - Condensate Return Cogen Plant - Biodiesel operation Future Plant - Biomass CHP

12 Economizer / Deaerator High fuel prices are an incentive for investment in boiler efficiency improvements. However, the regulated steam tariff includes a provision for fuel cost pass-through, which means that the company can only get a return on efficiency investments by filing a rate case. In 2008, two of the three 1972 package boilers were back-fitted with a wet economizer. Also, the pre-1940 deaerator was replaced with a smaller one that better fit operational parameters of the steam plant. Also in 2008, NRG filed a base rate case with the PUC to pay for improvements to the system and allow additional improvements.

13 New Boiler Economizers

14 New Deaerator

15 Other Steam Plant Investments Variable frequency drives for FD fans, boiler feed pumps, and instrument air compressor Decarbonator (saves on chemical costs) Smaller water softeners (more efficient) Instrument air compressor (less maintenance) Savings ~ over $50,000 electric costs per year

16 Decarbonator

17 Instrument Air Compressor

18 Annual kw-hrs Steam Plant Investment Savings Variable Frequency Drive (VFD) Electric Savings After VFD Original Fans Mtrs Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

19 Cooling Plant VFD Chiller Chiller plant built in 1997 with two 1200-ton centrifugal chillers. Since then, customer (Hospital and County buildings) demand grew to the entire installed capacity. Hospital approached NRG about a 200 ton expansion of their emergency room facility. NRG decided to add a third 1200-ton chiller, even though there would be excess capacity. This new chiller has VFD, which will save electric costs, particularly in cool weather operation. The chiller has been installed and testing completed. Expected full service operation will be this summer (2009)

20 New 1200 ton VFD Chiller

21 Steam Plant Condensate Return Harrisburg s 7-mile steam distribution system is open (no condensate return). This was not a problem 100 years ago when water was basically free. Today, condensate dumped down the drain costs the company and its customers many hundreds of thousands of dollars. A condensate collection and return project is currently underway to recover condensate from the Capitol Complex, which is about 40% of total steam sales volume About half of the collected condensate will be used as cooling tower makeup for the Capitol Complex chiller plant, and the balance will be returned to NRG.

22 Condensate Return Line

23 Cogeneration Plant B100 Operation February 2007: Pennsylvania Governor Rendell calls for energy independence. One aspect is use of Pennsylvania grown fuel. September 2007: NRG successfully runs pilot test of one 6MW diesel engine on B100 and B50 to test engine performance and emissions. Biodiesel is soy-based, obtained from local supplier. October 2007: Pennsylvania Energy Development Authority awards NRG $112,000 grant for further engine testing Summer 2009: Plan for extensive runtime on B50 to further test engine performance and emissions.

24 6 MW Diesel Engine B100 Test

25 Future Plant Biomass CHP The global push for efficiency and sustainability has a direct impact on district energy systems. As an industry, we have an obligation to make our product greener. Over the past twenty years, the Harrisburg district energy system has added a cogeneration plant and a cooling plant to the existing steam plant. Now is the time to add a fourth technology wood biomass CHP. Besides being a source of new revenue, a wood plant will also lower fuel cost to steam customers, comply with the Governor s mandate for green energy, reduce boiler run time to save maintenance costs, and help cover fixed administrative costs.

26 Future Plant Biomass CHP Challenges of developing a wood-fired CHP plant Securing a long term wood supply, Unlike oil and gas, wood is not a commodity that can be hedged. Instead, supply is secured with a local aggregator who develops multiple sources of wood that can be stored and transported to the plant site. Mitigating fuel risk. Project economic feasibility depends on maintaining a price differential between wood and natural gas which is being displaced. Selecting a reliable technology. Wood boilers are relatively new, and the best choice is one that can burn a variety of types and sizes of wood feedstock.

27 Summary and Conclusions Old power plants offer multiple opportunities to improve efficiency and eliminate losses. The most effective way to accomplish this is through investment in more efficient equipment. Variable frequency drives and heat recovery are two technologies that can accomplish this. The Harrisburg community energy system has evolved from a single steam plant to a multiple-facility district energy operation. Customers expect reliable, affordable energy, and NRG continues to seek new ways to deliver a quality product. IDEA serves a valuable role as a centralized resource for sharing ideas across the spectrum of participating member companies.

28 Contact Information Keith Li, PE Controller NRG Energy Center Harrisburg 100 N. Tenth Street Harrisburg, PA (717) Nrgenergy.com