Page 408 - A Comprehensive Guide to Solar Energy Systems

Chapter 21 • (EROI) and (EPBT) for PVs 417

=
nr CED(PE nr + Inv)/Out (21.7) nr−CED=(pEnr+Invnr)/Out
−
nr
where pE nr is the nonrenewable share of the primary energy directly harvested over system
lifetime; and Inv nr is the nonrenewable share of the energy investment in terms of its non­
renewable primary energy demand.
This relation expresses the nonrenewable primary energy harvested from nature per
unit of energy delivered to society as electricity. It is recommended to distinguish between
renewable and nonrenewable energy. The purpose of this metric is to evaluate the sus­
tainability and efficient use of nonrenewable primary energy resources from a long­term
perspective.
As previously described, using CED in accounting for energy inputs to a pv system
intrinsically handles the issue of energy quality corrections. Also, CED can analyze the
impact of an energy carrier on the stocks of primary energy sources and thus evaluate ef­
ficiency in that regard. As it can also differentiate between renewable and nonrenewable
primary energy inputs, this method also provides information on the sustainability of a
technology within a given primary energy source mix over the long­term. Unfortunately, it
becomes obvious that there is no one method for analysis that can answer every question
of pv system efficiency in society, and there is no one EROI for all pv systems. Every system
must be analyzed within its own set of boundaries and carefully stated objectives. Then,
perhaps the analyses can be harmonized given certain assumptions and comparisons can
be made.

21.3 Results of EROI Analysis of PV Systems, Harmonization
and Trends Over Time

21.3.1 Results of a UK Case Study Comparing PV and Nonrenewable
EROIs
In 2016 Raugei and Leccisi published a study that performed an NEA through EROI analy­
sis of the United Kingdom and its full range of electricity generation technologies, includ­
ing pv, using the methods described previously [34]. To their knowledge, this was the first
such national­level analysis at the time and is relevant to the body of information con­
cerning the EROI of pv systems. Although the vast majority of pv in the United Kingdom
is currently in the form of mono­Si and poly­Si, Raugei and Leccisi also included CdTe
in their study. The conclusions offer a comparison between those technologies and wind
(on­shore and off­shore), hydro, biomass, nuclear, gas (including combined cycle), oil,
and coal in terms of their impacts on UK economic growth. The comparisons calculated
as EROI el are illustrated in Fig. 21.4 along with the value for the UK electric grid as a whole.
The range of resulting EROI el of the different technologies comprising UK electricity is
fairly large due to the very low value of biomass and the very high value and potential of
hydropower. Gas­fired, nuclear, and wind energy can all be classified as well performing,