The 70% Report contains a summary of planned and unplanned outage times for the major components in the heating and refrigeration systems. This is useful information. The available capacities for each day in the heating and refrigeration systems were calculated by comparing the coincidental planned/unplanned outages of each major component in the two systems. The report states that the outage data were consolidated on a monthly basis and compared with the system peak load to determine the availability of the CPP to serve the monthly steam and chiller requirements of the U.S. Capitol Complex. The report notes that monthly availabilities greater than 100 percent indicate excess capacity. This is an interesting general analysis of the recent past performance of the existing plant. However, it does not provide a frame of reference or specific reliability indices that can be used in a comparative analysis of the present system and other options.

The word “availability” in common reliability engineering analysis is typically used to express the probability or percent of time that a component or system is in the operable state where it can perform its intended function. In the case of the steam and chiller systems in the CPP, the concepts of availability and unavailability can be extended to provide the probabilities of various output levels in the two systems resulting from subcomponent failures and other factors such as fuel, water, and electricity supply. The steam and chiller probability models can be combined with the relevant CPP demand models to produce responsive plant reliability indices. These indices can also be used to assess the reliability implications associated with increased or uncertain load demands and the reliability effects of de creased load demands due to building efficiency or technology improvements. The CPP models can also be combined with probabilistic delivery system models to produce AOC building reliability indices.

CPP Option 2 uses the concept of cogeneration to meet the electric, steam, and chiller requirements, while Option 3 involves the construction of a new conventional plant using different fuel mixtures. In each case, the ability to serve these functions can be examined using an approach similar to that applied to Option 1 and expressed by similar reliability indices.

Similar analyses can be conducted for Primary Options 4 through 10, if required. These options involve advanced technologies that may not have yet matured and been placed in commercial service. In these cases, there may be relatively little or no available reliability data. The basic methodology and resulting indices should, however, be common to all the analyzed options.

In summary, the committee recommends that a comprehensive risk analysis of the viable proposed options be performed before a commitment is made to any of them. This should include a clear statement of the governing reliability criteria and include numerical reliability indices that can be used to facilitate the decision-making process. The indices should express the ability of the CPP system to meet the future demands for electricity, heating, and refrigeration; account for the age of the primary and auxiliary equipment; and include the reliability of water, fuel, and grid-supplied electricity. The analyses should include the ability of the CPP to meet the electricity, heating, and refrigeration requirements and the ability of the tunnel configuration to deliver these requirements, including a differential analysis of looped tunnels versus pipe loops in single-tunnel configurations. An evaluation of the risk of cascading failures among steam, chilled water, and other utility lines within the tunnels may also be appropriate. The basic methodology used in evaluating the reliability indices should also be amenable to incorporating renewable fuel alternatives such as solar thermal, solar photovoltaic, and wind power generation in future applications.


Congress and the AOC’s other clients in the U.S. Capitol Complex need a strategic decision-making tool to aid them in planning and seeking funding for the upgrading of the CPP

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