Packaged CHP systems
Changing Sizing Philosophy
Furse notes that in the past the practice was to size systems purely on the thermal requirements of the site, producing only as much electricity as the thermal load would allow. “The latest trend seems to be that facilities are choosing advanced CHP systems with additional capacity, giving greater power flexibility. During peak hours they can run the system harder to offset power from the grid. The additional capacity also allows many sites to produce 100% of their needs in case of a blackout.”
She stresses, “Building owners want energy independence. They understand intrinsically the value of making your own electricity while capturing and repurposing the heat, and offsetting boilers. Offering turnkey solutions makes this technology more accessible and easier for a site to implement.”
A recent graphic example of the value of onsite generation was at a co-op residential facility in Greenwich Village, the Brevoort. It was able to maintain power, hot water and electric service during the recent outages in Manhattan following Superstorm Sandy. The 20-story facility is equipped with four InVerde 100 kW units that had replaced an oil-heat system two years earlier. According to Diane Nardone, the president of the co-op, theirs was the only building on lower Fifth Avenue to continue to offer energy and full service to residents.
Tecogen indicates that the low and stable prices for natural gas in recent years have influenced decisions on CHP. Furse says, “Sites that have been calculated as having a four or five year payback might now be only two to three years. Obviously, the shorter the payback, the more compelling the project.”
Larger Units for Larger Loads
Another recent presenter was Bill Pearson from Western Branch Diesel, representing MTU Onsite Energy, a wholly owned subsidiary of the Tognum group, a German company with a worldwide presence in onsite energy generation. This company offers systems manufactured and assembled in North America with full CHP potential. They have two product lines, the Series 400 ranging from 128 to 354 kW, and the Series 4000 ranging from 764 to 1930 kW.
The MTU Onsite Energy systems are designed to operate over a wide range of gas fuels, including natural gas, biogas, landfill gas and coalbed methane. This makes these units particularly attractive for applications where multiple fuels are used. Units are available with or without heat recovery options for various industrial uses.
The claimed efficiency of the MTU electrical generation ranges from 33% to 35%, and with full heat recovery, overall efficiency ranges from 90% to 92%, depending on the engine selected. Pearson explained that financial analysis indicates that a full heat recovery installation could have an investment payback of three years.
In another TMAF presentation, Stephen Zilonis from Dresser-Rand discussed his firm’s offerings in packaged CHP. The company offers an array of packaged or engineered systems well suited to industrial and institutional applications, including systems powered by Guascor or Caterpillar.
One intriguing possibility is the Dresser-Rand Caterpillar Trigen Package, which includes a 555 kW electrical output, hot water delivered at 180° F in quantities of 3,617,000 Btu/hr, and absorption cooling totaling 130 ton capacity. The entire unit is skid mounted and suitable for indoor or outdoor installation. The package includes all utility-required controls and customer monitoring capabilities.
Wide Range of Sizes
For any package CHP installation, it is important to accurately characterize the load to be served and to evaluate the physical space available for the CHP plant. 2G-Cenergy is a firm with long experience in gas-fueled CNG plants in Europe and now offering this technology in North America. The company offers units with capacities ranging from 80 kWe to 3 MWe, and designed for various fuels, including natural gas and many biofuels. In particular they emphasize that their units can be sited either indoors or outdoors, and they make special accommodation for use with absorption chiller packages.
As you consider the feasibility of CHP for your plant or institution, it is important to gather full-year energy usage information for electrical and boiler operations so that total energy requirements can be accurately forecast. Your natural gas utility can be of assistance in explaining service policies and can tell you about other CHP installations in your area.
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