Page 402 - A Comprehensive Guide to Solar Energy Systems

Chapter 21 • (EROI) and (EPBT) for PVs 411

FIGURE 21.3 Mean EROI (and standard error) for electric generation systems. Adapted from Hall CAS. Energy return on
investment: a unifying principle for biology, economics, and sustainability. Springer Nature, Lecture Notes in Energy, vol.
36. Cham: Springer International Publishing AG; 2017; Lambert J, Hall CAS, Balogh S, Gupta A, Arnold M. Energy, EROI,
and quality of life. Energy Policy 2014;64:153–67. For explanation and detailed references please see Hall CAS, Lambert
JG, Balogh SB. EROI of different fuels and the implications for society. Energy Policy 2014;64:141–52.

Despite the protocols offered by murphy et al. [19], given the relatively novel nature of
EROI, and the state of energy data in the world, many issues arose from differing calcula­
tions in EROI analyses over time. Although output data is generally published in technical
or industrial reports, for pv the nameplate or total capacity of a system is not always real­
ized and intermittency is an unpredictable variable. Also, the system lifetimes can vary
from region to region as well. Deriving energy inputs is even more difficult and less certain.
As most EROI analyses for fuels involve large industries and resources, direct measure­
ments are usually not available as an option. Also, it can be difficult to get the desired
energy cost data for calculating EROI because they can be privately owned by corporations
that tend not to make data of any kind available to the public and few nations maintain
industry­level energy data over time. There are also two different types of inputs—direct
and indirect energy costs. Direct energy is used on site, such as electricity used to dope or
cut wafers of solar cells. Indirect energy is used off site to derive materials or services used
later on site or other places in the development process. Indirect energy costs can add a
significant amount of ambiguity to methods not just because of data availability, but also
because of the problem of defining boundaries of analysis. For example, calculating the
indirect cost of the manufacturing of an aluminum frame for a pv array can be straight­
forward, but what about including the energy costs of business services, labor, and taxes?