from an ethanol plant to a New York City building
Successful CHP schemes serving buildings, district heating schemes and industrial sites across the US have won awards from the US Environmental Protection Agency. Both turbine and engine-based schemes were represented.
The US Environmental Protection Agency (EPA) has awarded ‘ENERGY STAR’ recognition to high quality CHP plants around the country as part of its CHP Partnership operations. The CHP Partnership is a voluntary programme seeking to reduce the environmental impact of power generation by promoting the use of CHP. It works with energy users, the CHP industry, state and local governments, and other clean energy stakeholders to facilitate the development of new projects and to promote their environmental and economic benefits.
The four most recent awards were given in October to:
- The Commonwealth of Massachusetts Department of Correction, for a 1.4 MW gas turbine-based CHP system serving the Bridgewater correctional complex
- Calpine Corporation for the company’s 449 MWe Carville Energy Center in Louisiana, which includes a CHP plant based on two large gas turbines
- Patterson Farms for a 200 kWe engine-based CHP plant fuelled with biogas produced at an upstate New York farm
- Equity Office Properties for a gas-fired 1.6 MW CHP system, again based on gas engines, which serves an office building in New York City.
Details of these four schemes are given below. Schemes that were also awarded ENERGY STAR status earlier last year were:
- Consolidated Edison Company of New York for a 360 MWe CHP plant that supplies steam to the huge district heating scheme in New York City
- Duquesne University in Pennsylvania for a 4.75 MWe gas-fired CHP scheme that serves university buildings
- Missouri Joint Municipal Electric Utility Commission for a 13 MWe CHP system that serves an ethanol production plant in Missouri.
BRIDGEWATER COGENERATION PLANT
The Bridgewater Correctional complex consists of around 7,000 m2 of living and working space on 38,000 Ha of land. In 2006, the Commonwealth of Massachusetts Department of Correction began operating a 1500 kW CHP system to support those facilities and an inmate population of over 2000 people.
The CHP system utilizes a Kawasaki natural gas-fired combustion turbine to generate nearly 80% of the complex’s annual electricity demand. Equipped with Kawasaki XONON combustors, the NOX emissions from the turbine are low enough to meet NOX emission requirements without the need for add-on pollution controls.
Otherwise wasted heat is recovered from the turbine exhaust and used to produce steam to support the daily heating, cooking, cleaning, and domestic hot water needs of the complex. Operation of the CHP system also allowed the Department of Correction to shut down an old diesel engine generator.
With an operating efficiency of approximately 67%, the CHP system requires approximately 17% less fuel than typical on-site thermal generation and purchased electricity. Based on this comparison, the CHP system effectively reduces carbon dioxide emissions by an estimated 3600 tonnes per year – approximately equivalent to the annual emissions from 600 passenger vehicles.
CARVILLE ENERGY CENTER
Calpine’s Carville Energy Center (CEC) in St Gabriel, Louisiana, has the capacity to generate up to 449 MW of electricity that is supplied to local wholesale power markets. That is enough power to meet the daily needs of approximately 205,000 residential households.
As a CHP system with two GE Energy natural gas-fired combustion turbines, the CEC recovers the waste heat and produces up to 190,000 kg/h of high-pressure steam that is used in the production of styrene and polystyrene at an adjacent plastics manufacturing plant.
With an operating efficiency of approximately 57%, the CHP system requires approximately 31% less fuel than typical onsite thermal generation and purchased electricity. Based on this comparison, the CHP system effectively reduces carbon dioxide emissions by an estimated 730,000 tonnes per year.
PATTERSON FARMS CHP SYSTEM
Patterson Farms, a sixth generation family-owned and operated business since 1830, has 1000 dairy cows and young stock on 1000 Ha in Auburn near Cayuga Lake in upstate New York. In 2005, a first CHP system was installed to generate electricity and heat for the farm while addressing an odour problem that had arisen from the use of an on-site manure lagoon.
This CHP system generates up to 200 kW of electricity from the combustion of biogas in a Caterpillar internal combustion engine. The biogas is produced from an anaerobic digester that processes nearly 50,000 gallons per day of manure waste from the dairy cows and 15,000 gallons per day of food waste from a cream cheese production facility. Hot water produced by capturing the otherwise wasted heat from the engine block is used to maintain the digester temperature. Excess power generated by the CHP system is sold to the local utility grid due to the state’s net metering provisions.
With an operating efficiency of approximately 58%, the CHP system requires approximately 6% less fuel than typical on-site thermal generation and purchased electricity. Based on this comparison, the CHP system effectively reduces carbon dioxide emissions by an estimated 340 tonnes per year.
717 5TH AVENUE COGENERATION PLANT
Located in the Plaza District of New York City, the 717 5th Avenue building contains 42,000 m2 of Class A office space owned and leased by Equity Office Properties. More than 60% of the building’s electrical and thermal demands are met using a 1.6 MW CHP system centred on a Caterpillar internal combustion engine. Supported by a grant from NYSERDA and operated by Endurant Energy, the natural gas-fired CHP system is the first of its kind to be synchronously interconnected to the midtown utility grid.
A GE-7FA gas turbine from GE – as used at the Carville Energy Center
The plant comprises two 800 kW G3516A generator sets, fuelled by natural gas.
With an operating efficiency of approximately 77%, the CHP system requires approximately 33% less fuel than typical on-site thermal generation and purchased electricity. Based on this comparison, the CHP system effectively reduces carbon dioxide emissions by an estimated 1200 tonnes per year.
How Kawasaki keeps emissions low
Mario DeRobertis, Regional Manager, Kawasaki Gas Turbines – Americas,
The gas turbine cogeneration system has increased the overall energy efficiency of the facility while simultaneously reducing gaseous emissions such as NOx, CO, and CO2. The nominally rated 1.4 MWe gas turbine generator system is a Kawasaki GPB15X, manufactured by Kawasaki Gas Turbines – Americas, a subsidiary of Kawasaki Heavy Industries.
The Commonwealth of Massachusetts Division of Capital Asset Management and Department of Correction opted for a cogeneration system, as the facility has a year-round need for both steam and electricity. The gas turbine was selected (despite a higher up-front cost), as it could deliver a near 80% net thermodynamic efficiency by supplying both electricity and high-energy steam (high-pressure superheated-steam). Although a natural gas reciprocating engine generator (lower up-front cost) was an option, the overall thermodynamic efficiency was much lower, as reciprocating engines produce very little high-energy steam.
|The Kawasaki gas turbine generator at the Bridgewater Correctional complex|
Before the cogeneration system was commissioned, the Bridgewater Correctional Center purchased all of its electricity, and produced all of its steam via on-site boilers. With the Kawasaki Energy solution, the BCC now generates approximately 1.4 MWe and 11 MMBTU/h, all from the same input fuel stream; natural gas. Given today’s very favourable natural gas prices, the Commonwealth of Massachusetts is realizing a handsome payback on the Kawasaki investment they made only a few years back.
The key to the Kawasaki GPB15X’s ability to keep air-pollutant emissions extremely low is a well-proven catalytic combustion system. Kawasaki purchased the technology rights to this technology several years back, and it is now known as ‘K-LEAN.’ The catalytic combustor is not selective catalytic reduction (SCR), nor is there a catalyst hidden inside of a standard flame-combustor. Catalytic combustion is exactly as stated, the air fuel charge catalyzes across the catalytic (proprietary) materials inside of the combustor, and heat is released. The catalytic reaction occurs at sub-NOx formation temperatures, thus there is nearly no NOx, and very little CO produced from this very efficient catalytic-combustion-reaction. The GPB15X may be permitted in all states in the US, without any further need for secondary (post-combustion) NOx emissions controls treatment.
Kawasaki not only supplies gas turbine generator systems, but also works with partnering technology providers to provide, heat recovery steam generators (HRSGs) and natural gas fuel compressors. The BCC Facility is equipped with both an HRSG, and a gas compressor. Kawasaki has a service contract currently in place to maintain its equipment.
The GPB15X cogeneration facility at the BCC quietly goes about its duties, year round, while abiding by Massachusetts’ strict emissions requirements, which are among the strictest in the US. The cogeneration system has logged over three years of continuous base-load operation.