Sizing Procedures

Hay (1987) considers the use of the load duration curve to model variable thermal and electrical loads in system sizing, along with four different scenarios described in Figure 7.14. Each one of these scenarios defines an operating alternative associated to a system size.

Oven (1991) discusses the use of the load duration curve to model variable thermal and electrical loads in system sizing in conjunction with required thermal and electrical load factors. Given the thermal load duration and electrical load duration curves for a particular facility, different sizing alternatives can be defined for various load factors.

Eastey et al. (1984) discusses a model (CO-GENOPT) for sizing cogeneration systems. The basic inputs to the model are a set of thermal and electric profiles, the cost of fuels and electricity, equipment cost and performance for a particular technology. The model calculates the operating costs and the number of units for different system sizes. Then it estimates the net present value for each one of them. Based on the maximum net present value, the "optimum" system is selected. The model includes cost and load escalation.

Wong, Ganesh and Turner (1991) have developed two statistical computer models to optimize cogenera-tion system size subject to varying capacities/loads and

Figure 7-14. Each operation mode defines a sizing alternative. Source: Hay (1987).

to meet an availability requirement. One model is for internal combustion engines and the other for unfired gas turbine cogeneration systems. Once the user defines a required availability, the models determine the system size or capacity that meets the required availability and maximizes the expected annual worth of its life cycle cost.

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