Lucena_subbed.qxp 17/8/09 10:51 Page 21
Renewable Energy in an Unpredictable and Changing Climate
climate change on Europe’s exploitable and developed hydropower
Figure 1: Climate Change Impact Assessment Methodology
potential. Based on projected inflow series to the reservoirs of 148
hydropower plants, Lucena et al.
20
used a simulation model to assess Greenhouse gas emission
climate change impact on the hydropower generation system’s average
and concentration scenarios
9
and firm power in Brazil.
General
circulation models
Cumulative uncertainties
Sailor et al.
25
tested a downscaling technique based on a neural network Large-scale projection
for climate variables
approach to assess wind power implications of climate change at three
(e.g. temperature, precipitation,
sites in the US. On a larger scale, Breslow and Sailor
26
assessed the
wind speed)
vulnerability of wind power resources across the continental US to climate
Downscaling
techniques
change. Using a similar approach, Lucena et al.
27
evaluated the impact
Regional-scale projection
of changes in wind speed on Brazilian wind power generation
for climate variables
potential. Segal et al.
28
investigated the impact of wind speeds as
(e.g. temperature, precipitation,
wind speed)
projected by the downscaled results of the HadCM2 GCM on wind power
Impact assessment
for specific sites in the US. Sailor et al.
29
investigated scenarios of climate
methodologies
change impact on wind power generation potential in the north-west US
Sectoral climate change
using five major airport weather stations as reference points. The impact impact assessment
of climate change on wind speed and energy density across northern
Europe was examined by Pryor et al. using dynamically
30
and statistically
31
western Europe), or complemented by other power sources (e.g. Brazil
downscaled data. Finally, offshore wind power generation was and Norway). If it is complementary to other generating sources,
investigated by Harrison and Wallace,
32
emphasising the vulnerability of average values for hydropower production generally provide a good
marine energy to climate changes in western Scotland. measure of impact. However, to minimise the risk of power shortages,
climate impact on hydro-based power generation systems must be
Hydropower Generation assessed in terms of firm power, which is estimated according to the
Studies that assess the impact of climate change on hydropower worst-case hydrological scenario.
production usually convert downscaled results for climatic variables of
one or more GCMs into water inflows to the reservoirs of hydropower The second factor is geographical dispersion and the level of
plants using a hydrological model. An electric power model is then integration through transmission capacity. In large interconnected
used to convert hydrological impact into variations in electricity hydropower systems that cover a vast area, transmission may play an
production. Some studies go further to investigate economic impact important role in optimising regional climate variations or even possible
in terms of investment return or revenue maximisation.
23,21
Other seasonal complementarities. For example, in 2007 the Brazilian
studies also assess how changes in power dispatch can affect the interconnected system had 119 power plants (24 of which were larger
whole energy system.
33
than 1,000MW) in 10 different large river basins
43
across an area
of more than 8 million km
2
in national territory.
44
That year,
Methodologies for assessing the hydrological impact of climate change hydroelectricity accounted for 82% of the country’s interconnected
are well developed in the international literature.
34,35
Using downscaled system’s capacity.
43
Just as the operation of different plants in the same
GCM results for temperature and precipitation, physical or conceptual river cannot be optimised individually, modelling hydropower operation
water balance models have been applied to evaluate the impact of in these cases should consider the rationality of a central operator that
climate changes on run-off in catchments and river basins of different looks at the whole picture and not individual basins.
sizes.
7,36–38
On a large spatial scale, macro-scale hydrology models have
been used for climate impact assessments on run-off.
39–42
Individual plant characteristics are particularly relevant in small
systems. Small run-of-river plants offer little flexibility and are most
The approach used to translate climatic impact into hydroelectricity vulnerable to climatic variations. Natural river flow can be highly
generation depends greatly on the scale and scope of the analysis. The variable, especially across seasons. Reservoir storage capacity can
characteristics of a hydropower generation system ultimately define compensate for seasonal (or even annual) variations in river flow,
the appropriate impact assessment methods. Physically based enabling electricity generation throughout the year and matching
hydrology models are more appropriate to analyse small river basins varying power demand. Reservoirs act as buffers by ‘storing energy’,
and, thus, a single small or set of small hydropower plants. However, which can help hydropower plants to cope with climate changes.
this may not be viable in large and complex systems with large, Including other reservoir uses (such as flood control, providing water
interconnected power plants at different river basins due to the vast for human and animal consumption, etc.) in the analysis can add a
data requirements of physical hydrological models. significant amount of complexity. In fact, often other uses such as
irrigation can also be affected by climate change.
The complexity of hydropower simulation models can range from
modelling the operation of a single small plant to modelling a complex Finally, climatic impact may not be equally distributed throughout the
system. Besides the characteristics of individual plants, two factors year, so climate change may affect not only the quantity, but also
influence the complexity of a hydropower generation system. The first the timing, of water availability for hydropower generation.
21
In regions
is how relevant hydro generation is for the whole power system or where snowmelt is a relevant issue for the hydrological cycle, for
whether hydroelectricity is complementary to (e.g. the US and most of example, early snowmelt caused by climate change may affect the
MODERN ENERGY REVIEW VOLUME 1
21