Cogeneration CHP, Equipment, Equipment & Technology

How to maximize availability

The car analogy falters when considering that driving a car can be a pleasure in itself. Operating an industrial gas turbine is not done for pleasure; it is a means to an end. The power that a gas turbine produces allows the owner-operator to carry on with its core business, be that automobile manufacture, chemical processing or foodstuff extraction.

Table 1. A typical gas turbine maintenance schedule
Interval Action
Every 4000 running hours (engine remains installed) Inspection of gas generator inlet
Removal of low-pressure compressor casings to permit inspection of compressor stator and rotor
Borescope inspection of high-pressure compressor, combustion section, turbines and integrity features
Inspection of oil filters and chip detectors
Inspection of engine’s exterior
Every 8000 running hours (engine remains installed) As for 4000 hour action plus:
Replacement (exchange) of high-pressure compressor stator assembly
Refurbishment of low-pressure compressor vane assembly
Every 25,000 running hours (engine removed) Replacement (exchange) of hot section module:
combustion and high-pressure turbine modules
Every 50,000 running hours (engine removed) Full overhaul and reconditioning of complete engine to return to an ‘as new’ standard

Maintenance, repair and overhaul (MRO) service providers, such as Volvo Aero, take on the challenge of maintaining gas turbines so that customers can focus on their core business. The more risk that a customer passes to its MRO service provider, the greater its peace of mind.

in a restructured electricity market

The benefits of cogeneration extend well beyond reduced energy bills to the user. Other parties benefit from reduced emissions, deferred investment in grid strengthening and the alleviation of grid congestion. But it is not easy to put a monetary value on these attributes. Christopher Beebe has started to quantify the benefits for one US city.

The author (left) and a colleague measuring the load of the cooling system for a building at the University of Massachusetts, US, to evaluate the feasibility of a cogeneration system there

Throughout the US concerns are growing that consumption of electricity is outpacing upgrades made to the electricity grid system. As the disparity grows between electricity consumption and the ability of the grid to handle the required loads, price spiking, price increases and reliability issues will become more prevalent.

Such factors as the deregulation of the electricity industry, transmission and distribution upgrade costs, environmental concerns and worries over energy security have prompted regulators, legislators and developers to investigate the use of distributed generation (DG) as a solution to help alleviate these concerns. Cogeneration, or combined heat and power (CHP), is a specific type of DG that refers to a strategically placed electricity power-generating unit at or near a facility where waste heat from the generation process is used to supply on-site thermal processes. Cogeneration is the production of both electrical energy and thermal energy within one system and can be nearly twice as efficient as conventional power systems.

Although cogeneration is continuing to be recognized for its far-reaching energy-conservation, environmental and economic benefits, there has been no method developed for calculating the exact economic value of these external impacts. Additionally, it has not been determined which stakeholders among the end-user, the electricity utility or society as a whole would reap these externality benefits.

In this market, externality benefits are defined as the positive impacts of a technology that spread beyond its immediate simple payback. In the case of cogeneration there is expected to be positive economic value created regarding its impact on the electricity transmission and distribution system, wholesale power pricing, system installed capacity, and emission and environmental issues. If a method to extract these values is developed, the estimated payback of four to six years for a well-sited cogeneration application may be substantially reduced.