sustainability - SUNY College of Environmental Science and Forestry

Sustainability 2011 , 3
1922

EiW(x)= 2. 24 *( 1 −. 013 )X (kWh/$ for 2006 +X) (2)
It is not necessary to account for the business as having nested scales of organization. We do it
largely to help demonstrate the method. We aggregate the additional energy identified at each jth
working unit level as dSEAj, as shown in Equation (3), where TE,k and EE,k are combined after
adjustment to for overlap if needed, for “M” business costs assessed, and “j” is the level of
organization considered. The total energy input (SEAN) for the whole business system is the sum of
the added energy inputs for each of the “N” business units (Equation 4).

d ∑[ ]

=

= +

M

k

SEAj TEk EEk

0

, ,^ (3)^

∑

=

= +

N

j

SEAN LCAE dSEAj

0

(4)

Values of technology energy (TE) may be obtained either from fuel use records or from fuel or
technology costs or budgets ($T) multiplied by the appropriate intensity weight factor Tii and the
average energy intensity of money (EiW), Equation 5. Values of economic energy use (EE) are
similarly calculated using economic costs ($E) multiplied by the appropriate intensity weight factor
(Eii) and the average energy intensity of money (EiW), Equation 6. If those values represent partial
measures for different things that may overlap the added step of removing an estimated economic
value for TE from $E is needed to eliminate the overlap between the definitions of the two measures
(Figure 5), so $E is reduced by $T before TE and EE are combined (Equation 7, 8).

TE = recorded fuel use, or TE = $T · Tii · EiW in relation to cost (5)

EE = $E · Eii · EiW in relation to cost (6)

Or, with $T = TE/(Tii · EiW) (7)

EE = Eii · EiW · ($E –$T) (8)

2.4. Models and Input Values

We present two separate models (1) using a table with 20 year average costs without discounting
and (2) a cash flow model with discounted costs over time. Both models use the same 20 year business
plan based on the JEDI budget for a 100MW wind farm [26] as if located in Texas. All money and
energy costs are stated as per kW of total generating capacity. LCA data was obtained from the Vestas
Onshore 2.0 MW wind turbine study [25], 13,100,000 MJ (3,640,000 kWh). The distribution of energy
types for the LCA account is shown in Table 1, showing somewhat more fuel from oil than the world
average. Table 2 displays the key business model inputs, including the wind generation capacity factor
and other distributions from the DOE 2008 wind report [10]. Our equations for both partial and total
EROI and LCOE measures follow the usual standard definitions as in Equations 9 and 10 respectively.
A simple version of our Excel model with data and formulas is available [ 29].

EROIn = Eout/Ein for each SEA level (9)

out out

T E

n NPV E E

NPV C C

LCOE partial^ costs^ assessed

( )

( )

∝

+

= ∑ (10)

G