Operation & Maintenance
Once plant installation has been completed, the required levels of performance and availability, and the associated economic benefits, can only be achieved and optimised if the plant is correctly operated and maintained.
Plant Operation
Once plant installation has been completed, the required levels of performance and availability, and the associated economic benefits, can only be achieved and optimised if the plant is correctly operated and maintained. There are examples of effective and efficient CHP plants failing to deliver the anticipated benefits because of a lack of emphasis on the on-going management of plant operations and maintenance.
Effective operation of a CHP plant requires the continuous monitoring both of site energy demands, and of the tariffs and costs associated with meeting those demands. Monitoring must be used as a means of continuously evaluating the most economic use of the plant, taking into account its performance and efficiency, its maintenance costs, and the costs of external energy sources such as electricity and gas. One typical scenario arising from this is that, during the overnight period, it may be cheaper to supply electricity from external sources and to use back-up heat supply plant, than to operate the CHP plant.
It is equally important to be aware of the future maintenance costs that are being built up by operating the plant. This is particularly important where the costs of plant operation and the costs of plant maintenance are managed by separate budget holders. At the same time, plant operation must not be constrained by inadequate maintenance budgets that prevent the optimum energy performance of the plant from being achieved.
Many industrial CHP plants incorporate numerous items of equipment, which may include fired boilers and auxiliary items such as compressors, chillers etc. Overall plant control techniques need to be flexible enough to ensure optimum performance of the whole installation. There are varying levels of automation that can be used to achieve the required level of control.
Particular attention should be paid to:
Plant maintenance
All CHP plant requires effective and reliable monitoring and maintenance in order to provide the required levels of reliability and efficiency. Maintenance can be broken into two key groups: prime mover maintenance requirements and site maintenance requirements. The complexity and frequency of maintenance varies for different plant items, and this influences the options for selecting the best source of maintenance and repair expertise.
Responsibility for plant maintenance usually rests with the plant owner or operator. This may be the site owner, a contractor that has installed the plant under an energy services company (ESCO) contract or equipment supplier finance arrangement, or a contractor to whom all aspects of plant operation and maintenance have been subcontracted.
It is common for some maintenance work on specialised plant such as gas turbines and engines to be contracted out to the equipment manufacturer or supplier, or to other specialist organisations. The level to which a plant owner or operator will retain or subcontract these responsibilities will depend on the expertise available in-house and on the degree to which there is a desire to subcontract the risks and liabilities associated with plant performance and availability.
While the use of in-house resources may be appropriate for minor maintenance tasks such as routine plant checks, lubrication, oil changes, filter changes, set point adjustments etc., it is normally necessary to have major work, whether planned servicing and overhauls, or breakdown repair work, carried out under maintenance contracts with the original equipment supplier. In all cases, the establishment of a suitable long-term maintenance contract should be considered as part of the equipment procurement procedure. It should cover all the maintenance needed to achieve a defined level of plant availability. This approach allows a CHP operator to make better decisions on the total life-cycle costs and benefits of the project. The contract should also provide for some assurance regarding the quality and suitability of replacement parts and components.
Performance Assessment
Condition monitoring of the CHP plant is an important part of preventive maintenance. Performance monitoring is essential to ascertain whether plant outputs and efficiencies are consistent with those demonstrated in the performance tests prior to handover.
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