Page 290 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

Other Aspects of Ocean Renewable Energy Chapter | 10 277

In addition, with generally increasing global temperatures and a blurring of the
distinction between seasons, the intraannual pattern of demand for electricity
may vary significantly in the future within the context of global warming.
For example, hotter summers could lead to more demand for electricity to
provide cooling during summer months (generally a period of lower demand
for electricity at relatively high latitudes—see Fig. 10.1D), yet milder winters
would lead to lower demand for electricity for heating during what is currently
2
the time of year that is associated with the highest demand for electricity. Here,
we focus on how marine renewable energy resources (rather than demand for
electricity) are likely to change in the future.

Wind Energy
There have been several studies that examine how the wind resource is likely to
vary in the future, although these studies generally make no distinction between
the onshore and offshore wind resource. It is important to note that there is
already large interannual variability in the wind resource, and so future trends
are often difficult to distinguish in such analysis. In general, studies are based
on the outputs of global climate models (GCMs) through either dynamical or
statistical downscaling [5]. Within Europe, the general trend is for an increase,
towards the end of the 21st century, in the autumn and winter wind energy
resource in northern and central Europe, with a corresponding reduction of the
resource across the Mediterranean (with the exception of the Aegean) [6–8],
and this trend also generally applies to annual mean wind speeds [5]. These
findings are consistent with a progressive tendency towards the positive phase
of the North Atlantic Oscillation (see Section 5.5), which is strongly linked
to winter wind speeds in northern Europe. Changes in the annual mean wind
energy density are within the range ±10%, but the change during winter months
alone is around ±20% towards the end of the 21st century, with increases
up to 25% predicted for the United Kingdom [8]. In the period 2081–2100,
Cradden et al. [9] calculated, based on analysis of a range of climate scenarios,
that in the United Kingdom, wind speeds will generally increase by around 5–
8% in autumn/winter, and reduce by 5–8% during summer months (Fig. 10.4).
However, they found that, although there were spatial and temporal differences
in the future UK resource, in general the annual capacity factor from two
offshore wind farms is almost unchanged in the future (2081–2100), compared
with a 1961–90 baseline, under a range of Intergovernmental Panel on Climate
Change Fourth Assessment Report (IPCC AR4) climate scenarios (Table 10.1).
Similar studies for Ireland [10] and southern Africa [11] also demonstrate
significant seasonal changes, but little change in the annual mean wind resource
up to the middle of the 21st century. Fant et al. [11] reported that the largest
change in wind speeds in the middle of the 21st century across southern Africa

2. Although the demand for lighting will not be affected by climate change.