IEEE Power & Energy Magazine - September/October 2020 - 38

Scenario Definition

Power Generation Planning Model

The development options were derived through extensive communication with the Paraguayan utility company ANDE. In
total, eight scenarios were developed. Options 0 and 1, which
simply represent the continued operation of the existing Acaray I and II power plants, were used as the basis of comparison for all future scenarios. Options 2-4 dealt with various
upgrade scenarios for the existing power plants. Options 5-7
involved the construction of new facilities in combination with
upgrade options. This is described in more detail in Table 1.

The purpose of the model was to conduct detailed simulations for each development option-and to calculate their
respective generation-with a corresponding cost reduction
to meet system load. The model dealt with the hydraulic
representation of the Acaray River system and included the
natural inflow points, storage at Yguazú dam and Acaray
power stations, generating units, tailwater effects, and conveyance between reservoirs. The transmission system was
also modeled and included the energy market representation
so that the contribution of both the Acaray power plants and
the energy transactions in meeting load were properly calculated. In this analysis, the following markets were considered (Figure 2):
✔ Itaipú contract; both as a guaranteed capacity contract
and a nonguaranteed hourly contract
✔ Itaipú excess contract
✔ Yacyreta hourly contract.
Overall, the implementation of the model required the
following steps:
✔ determination of the model inputs through
* data collection, including a review of historical records and meeting with ANDE staff
* on-site efficiency testing
* hydrologic analysis
* market and load analysis
* review of the main assumptions
✔ model calibration
✔ model setup and simulations for all the scenarios defined in Table 1
✔ sensitivity analysis.
The unit efficiency at both plants was determined by performing efficiency tests during one of the site visits. Because
modern units would bring significant efficiency improvements, assessing current unit efficiency provides critical information in characterizing the economic benefits of any future
unit upgrades.

Vista DSS
Revenue
Calculations-All
Options

Benefits

Acaray III/Yguazú
Options
Engineering
Estimated Costs

Hydrovantage
Rehabilitation and
Upgrade Options
Costs

Cost-Benefit
Vista Report

Cost-Benefit
Hydrovantage

Cost-Benefit Comparison-All Options

figure 1. The cost-benefit evaluation process.

table 1. The scenario definition.

Development Option

Description

Basis of Comparison

Historic operation

Actual generation from historic records

Optimized operation of existing facilities

Historic operation (option 0)

Rehabilitation of Acaray I/new generators at Acaray II

Optimized operation (option 1)

Runner replacement at Acaray I/new generators at Acaray II

Optimized operation (option 1)

Upgrade of Acaray I/new generators at Acaray II

Optimized operation (option 1)

Upgrade of Acaray I and II

Optimized operation (option 1)

New development at Acaray III

Upgrade of Acaray I and II (option 4)

New development at Yguazú

Upgrade of Acaray I and II (option 4)

New development at both Acaray III and Yguazú

Upgrade of Acaray I and II (option 4)

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IEEE Power & Energy Magazine - September/October 2020

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