comment:
This is an IPAT-S script. IPAT-S is an open-source scripting language
for developing sustainability scenarios. It can be run using the free
IPAT-S software, available from:

	http://ipat-s.kb-creative.net/

For more information, please contact the author of IPAT-S,
Eric Kemp-Benedict (eric@kb-creative.net)
:comment

comment:
This script implements a model inspired by the "energy ladder"
hypothesis. The hypothesis is that households at different income
levels climb an "energy ladder," from less-expensive and less-
convenient fuels to more-expensive and more-convenient fuels.

In the script below, the "convenience" of fuels is a numerical
parameter. In practice, this might come from an expert panel or
from a household survey.

NOTE: The parameters in the equations below are to illustrate the
IPAT-S language only: they are not estimated from data.
:comment

baseyear 2000
scen years 2005 to 2020 by 5

dim household 'low' 'mid' 'high'
dim fuel 'dung' 'wood' 'coal' 'kerosene' 'LPG' 'electricity'

# Declare variables (entries for households are per household)
summ var FuelBudget{household} aveFuelBudget
summ var totFuelUse{household}
var HHShare{household}
ratio income{household}

summ var FuelUse{household fuel}
summ var totFuelByFuel{fuel} totFuel
var convenience{fuel} cost{fuel}

# Set up hh distribution table -- constant all years
HHShare{household = 'low'} = 20%
HHShare{household = 'mid'} = 60%
HHShare{household = 'high'} = 20%

# Initialize values for households
FuelBudget.by{household = 'low'} = 50
FuelBudget.by{household = 'mid'} = 150
FuelBudget.by{household = 'high'} = 750

totFuelUse.by{household = 'low'} = 105
totFuelUse.by{household = 'mid'} = 130
totFuelUse.by{household = 'high'} = 190

income{household = 'low'} = gr(<1.50%>)
income{household = 'mid'} = gr(<2.25%>)
income{household = 'high'} = gr(<3.0%>)

# Calculate future household characteristics -- use elasticities
chain >> income^<0.75> -> FuelBudget
chain >> income^<0.25> -> totFuelUse

summarize FuelBudget * HHShare as aveFuelBudget

report aveFuelBudget as "Ave. HH fuel budget (l.c./hh)"

# Set up convenience/cost parameters
convenience{fuel = 'dung'} = 1
convenience{fuel = 'wood'} = 2
convenience{fuel = 'coal'} = 3
convenience{fuel = 'kerosene'} = 4
convenience{fuel = 'LPG'} = 5
convenience{fuel = 'electricity'} = 6

cost{fuel = 'dung'} = 0.2
cost{fuel = 'wood'} = 0.5
cost{fuel = 'coal'} = 1.2
cost{fuel = 'kerosene'} = 2.5
cost{fuel = 'LPG'} = 4.2
cost{fuel = 'electricity'} = 7.0

# Next, solve the LP for each year and see how fuel use changes
LP:
solve for FuelUse
max convenience * FuelUse

cost * FuelUse <= FuelBudget
FuelUse = totFuelUse

:LP

chain HHShare * FuelUse -> totFuelByFuel -> totFuel
report 100 * totFuelByFuel/totFuel as "Fuel share (%)"