Sustainability 2011 , 3
1916
Figure 2. The distribution of estimated EROI values from a survey of past wind energy
studies [14], showing the number of findings in each EROI estimate range. The unusually
wide variation in estimates implies the use of inconsistent standards.- Methods
The SEA method allows us to disaggregate global energy use data for individual business costs. It
uses “hybrid” accounting to combine recorded and proxy measures of energy use based on average
intensities for monetary costs, not dissimilar to Bullard or Treloar [11,20]. Instead of using intensities
for only technology energy uses, our intensities are for shares of global economic energy use, adjusted
in relation to that average if good reason is found.
The key step, from a physical science view, is our method of deciding what energy uses to count.
To identify what energy uses are necessary for the operation of a complex environmental system, such
as a business, one needs to develop an exhaustive search strategy as a means of deciding what to
include. In practical terms that means defining a starting point a then a way to expand the search and
then determine when you are at a stopping point. The starting point we use for our case study is an
LCA estimate for the life cycle energy costs of the wind turbines and their related capital costs for
plant and equipment, for our conceptual model of a Texas wind farm, based on JEDI and VESTAS
project data [25,26]. We could start from any other part of the business too. We just chose to use the
usual ending point of business energy assessment as our starting point.
Our procedure is then to ask what else is needed to make those parts of the business work, over and
over, until we have exhausted what is needed to deliver the product to market. In that way we let the
business as a working system, in its natural form, guide the questioning and determine the limits. That
end point identifies the whole working organization of the business as an operating system. A business
is a system that makes internal choices for how to work as a whole, operating in a larger open market
economy. The economy may determine what its options are, but leaves it a considerable range of
choices. As an financial system the line where the internal organization of the business comes to an
end, and the external parts and market organization of the economic environment begin, is determined
by whether decisions made affecting the business are being paid for from business revenues. Those