The LEAP (Long range Energy Alternatives Planning system)
model is a static energy-economy-environment model developed
by the Stockholm Environment Institute since the early 1980s
[42]. The model forecasts the energy demand, consumption and
environmental emissions impact of each sector of an economy
and analyzes the benefits of different energy scenarios compared
to a reference scenario. The model is the simulation of the energy
and environmental system and is called a bottom-up or end-use
energy consumption model [43]. In this study, the new capability
of the LEAP software tool is used to calculate the optimal solution
and dispatch of power plants for Indonesia and Thailand in the
Southeast Asian electricity system. The ‘optimal’ is referred to as
the energy system with the lowest total costs or net present value
of the social costs of the system over the entire planning period, i.e.
from the base year to the end of the planning year. The least cost
system is calculated subject to different user-defined constraints
including maximum allowable annual emissions for any given pollutant
and minimum or maximum capacities for certain power
plant types in the electricity supply side. For example, future
generation pathways for an energy system can be calculated so
that it meets the minimum renewable portfolio standard in
addition to meeting greenhouse gas emissions targets set by the
Federal Governments [44].
The least cost solution of a given pathway could be very sensitive
to input assumptions about the future, such as capital costs,
energy efficiency, different fuel costs, or GHG reduction targets. A
system that is optimal for a country under one set of assumptions
may be far different for another set of assumption for another
country. Generally, in any integrated system planning tool the goal
is not to identify a single optimal solution, but rather to identify
robust energy policies that work well under a range of plausible
input assumptions. Moreover, in the present study, the LEAP
model’s scenario generation features are used to calculate and
explore different optimal solutions under different sets of input
assumptions. LEAP includes the capability to automatically
calculate least cost future capacity expansion and dispatch of
supply-side transformation modules.