Sustainability 2011 , 3
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Table 3. Cont.
- Taxes on net revenue are 36% of net revenue, approximating the ratio of total US local, state and federal
government costs to GDP, from an online calculator http://www.usgovernmentrevenue.com/
yearrev2008_0.html;
- The production tax credit considered in the financial model is assigned an Eii of zero and not, considered as a
transfer payment from other tax payers and not included in the cost totals here or considered as an energy source;
- The accumulative internal EROI of 9:1 and external EROI of 6:1 indicate the energy available to society before
and after including the basic operating costs of the economic environment, dSEA4.
- Whole System SEA and EROI Estimate Models and Results
3.1. Method 1. SEA Table and 20 Year Average Costs
Table 3 shows our assessment of the business plan for the wind farm, beginning with the LCAE
energy content of 90.9 kWh/kW and the implied EROI of 31:1 for delivering the 2856 kWh output.
From that we ask what else is needed and add energy requirements for successively larger parts of the
business operations required to deliver the energy for sale. The accumulative EROI for each level is
shown in column 9 and the SEA and EROI results are graphed in Figures 6, 7, 10 and 12.
The basic procedure for each item in the table starts with either column 1 or 3, a dollar cost or an
energy cost. We assigned budget range estimates for all inputs as shown in column 8, with
accumulative variances at each level shown underlined and graphed as error bars in Figures 7 and 12.
The next step is to estimate values for Tii and Eii as above or below average and establish what value
of $T (column 4) to remove from $E (column 1) in calculating EE (column 6) using Equations 5 to 8
for possible overlap. It’s important to note, that if it happens that Eii = 1 then the values of TE cancel
out in Equation 8, making the equation for SEA = TE + (EE – TE). That shows that if you don’t know
much about the energy intensity of any item, finding some partial records of direct energy use to both
add and then subtract in equal amounts, does not improve the estimate. So without doing a fairly
careful study the simple estimate using Eii = 1 for average energy use per dollar is implied. It also
shows the need for empirical studies to develop other guideline intensity factors for Eii and Tii for
various common types of businesses and expenses.
3.2. Summary of Method 1. Results
As more of the needed business operations are counted from SEA0 to SEA3, and we count costs
further removed from the high cost heart of the business operation, we find a succession of smaller
changes in the partial estimates of EROI (Figure 6,7,8). When crossing the boundary from accessing
the business’s internal to external environment needs, going from SEA3 to SEA4, quite large monetary
and implied energy costs and uncertainties are found again, associated with financing, unpredictable
net revenues and taxes. As a metaphor, it portrays the business operating as a fairly well defined ship
navigating relatively large and unpredictable shifting seas of other things. The partial estimates of
EROI decline from 31:1 at LCAE to 9:1 at SEA3, with an increase of 350 % of in the energy use
accounted for. It further declines to 6:1 at SEA4 for an added 150% in the energy use accounted for.
One of the interesting points is how the intensity factor of Eii = 1.5 (Table 3, col. 5, 2 nd & 3rd line)
was arrived at for the capital costs of the business. In an initial attempt to use realistic values, 1.5 was a
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