Measuring Performance of Long-Term Power Generating Portfolios - Green Energy and Efficiency: An Economic Perspective - page 408

CO2 emissions (yearly average)

140

120

100

80

60

40

20

0

GONE GREEN SLOW

PROGRESSION

ACCELERATED
GROWTH

CONTRACTED
BACKGROUND

Scenario

Fig. 14 Yearly average carbon emissions from each GB generation mix over 2012 - 2032

emission allowance price to some extent. Yet the amount of carbon emissions can
be used as such to assess the four generation portfolios from an environmental point
of view.
We computed the average of the 750 cumulative values for the above variables
and others. Dividing these by the 20 years in our time horizon we obtained yearly
averages.
Each scenario involves different utilization patterns of power technologies thus
giving rise to different levels of CO 2 emissions. Here again the CB scenario out-
performs the others, so in principle there seems to be no trade-off between cost
ef

ciency and carbon objectives. Figure 14 displays the average results. Note that
even if the time pro le of these emissions is asymmetric (which will render average

values unreliable), from an environmental viewpoint it is basically the same whe-
ther a ton of CO 2 is emitted in 2017 or 2023 (it will stay in the atmosphere for
centuries). It is the cumulative emissions from each portfolio that matters. Since the
time horizon considered is the same across the four portfolios, the ranking based on
cumulative emissions coincides with that based on average yearly emissions.
Nonetheless, the time pro le of these emissions is quite asymmetric (as the

composition of the generating eets changes over time) so their yearly averages

must be taken with caution. We resort again to the target curves that result from
alternative power portfolios; see Fig. 15 . The CB portfolio stochastically dominates
the other portfolios. In other words, it entails a lower probability of surpassing any
given level of carbon emissions. As expected, AG comes second, followed by GG;
SP portfolio is last.

3.7 Diversi cation and Concentration Issues

Depending on the prevailing circumstances, an ef cient generation portfolio could

in principle concentrate on one or two technologies (and hence primary energy
sources). For example, the lack of long-term nancial instruments for managing