INTEGRATING VARIABLE RENEWABLES
INTEGRATING VARIABLE RENEWABLES: TECHNICALLY FEASIBLE
AND AFFORDABLE
Renewable power sources are variable: their production fluctuates due to natural circumstances.
Yet electricity supply cannot be variable; it must meet demand at all times, or blackouts will
occur.
Solar energy is diurnal, with a typical solar photovoltaic (PV) capacity factor of 12%-25%. Wind availability ranges from 20%-50% and tends to be higher for offshore wind than for onshore wind; it also increases with turbine
height. Biomass and hydropower resources can be seasonal and may vary from year to year. The variability of
these renewable energy sources can impede efforts to integrate renewables into the electricity supply.
The need to provide a constant supply of electricity creates challenges for utilities and grid operators on the
short time scale of seconds and minutes, as well as on the longer time scale of days and weeks. Grid stability
issues are more pronounced for smaller grids and individual power plants than for large, integrated grids, as
fluctuations in supply tend to be less pronounced for larger grids. However, problems can still arise on the local
scale.
A range of technical options exists to deal with variability. There is no “one size fits all” solution.
Technologies which can play a key role in supporting the integration of variable renewable energy sources
include: diversification of renewable energy resources in space and by type, integrated network expansion
(including interconnectors), the latest grid codes (including grid service specifications for renewable supply
options), market models which provide better price signals, demand-side management, smart grid technologies, backup fossil fuel capacity and electricity storage. Yet the right mix depends on the grid specifications,
the mix of supply technologies and the demand characteristics.
Technical solutions exist to maintain grid stability; however, markets need urgent reform to make
a viable business case for such solutions in all locations.
Experience in Denmark, Germany, Ireland, Iceland and several island countries has shown that existing grids are
already capable of integrating significant amounts of variable renewables, in excess of 25% of total electricity
generated. And in many developing countries, electricity demand exceeds capacity and blackouts and burnouts occur regularly in fossil fuel based grids. Where this is the case, even variable renewables can enhance
the reliability of the power supply.
Many governments underestimate the growth of variable renewable energy and are not planning
adequately for higher shares of variable renewable power.
For solar PV and wind power in particular, government targets are well below current market growth rates with
950 gigawatt (GW) of wind and 450 GW of solar PV capacity for 2030. According to REmap 2030, market
growth could accelerate further from today’s growth and reach around 1 500 GW of wind and 1 250 GW of
solar PV capacity in 2030.
Despite rapidly growing capacity additions, the shares of variable solar PV and wind power in
electricity generation will still be relatively modest in 2030.
At a global level, the average share of variable renewables in power generation in 2030 is around 18%. This is
less than the shares of variable renewables that currently are integrated into the electricity systems of Denmark, Germany, Ireland, Portugal and Spain. Only a handful of countries – Australia, Denmark, Germany, Morocco, Tonga and the United Kingdom – will reach shares of variable renewables of 30% or higher (see Figure 1).
Achieving such high shares of renewables will require more accurate forecasting methods, more stringent grid
codes and upgrades of both transmission and distribution networks. But the good news is that many countries
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INTEGRATING VARIABLE RENEWABLES
have already begun to use innovative tools
and policies to support the integration of
renewable energy into the grid.
Integrating variable renewables can
create both costs and benefits.
The integration of variable renewables can
lead to additional grid infrastructure costs
if: 1) the variable renewable resources are
located farther from demand centres than alternative power resources, 2) the operational
costs of existing power stations are increased
and 3) additional capacity is required to ensure that peak demand is satisfied.
The opposite relation, however, is also true.
Variable renewables can reduce grid costs
and grid losses if these resources: 1) are located close to demand centres (e.g. solar PV
systems on rooftops), 2) improve operations
of existing power systems, 3) reduce the
additional capacity needs required to ensure
that peak capacity is satisfied (e.g. if solar PV
matches with air conditioning loads) and 4)
reduce wholesale electricity prices, as witnessed in Germany.
Figure 1: Renewable energy share in total gross power
generation in REmap 2030
Denmark
Germany
United Kingdom
Australia
Wind
Italy
Solar PV
Global Average
Solar CSP
France
Japan
Biomass
USA
Geothermal
Morocco
India
Ocean
China
Hydro
South Africa
Ukraine
Saudi Arabia
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
RE share in power generation
A comparative analysis – focusing on the REmap results for Germany and Japan – has shown that
grid integration costs can be in the range of 10-15% of total electricity supply costs.
Grids account for around 40% of projected power supply investment needs between now and 2030. The
additional costs for integration of higher shares of variable renewables are comparatively small. Smart grid
IT-technology helps to reduce investment needs as it increases flexibility of supply and demand. Cost tend to
rise exponentially with the share of variable renewables.
REmap analysis suggests a growth in energy storage from 150 GW today to 500 GW by 2030. Pumped hydropower is currently the main centralised power technology used to store electricity and release it when it
is needed. Today, less than 3% (150 GW) of global installed power capacity is pumped hydro, and in REmap
2030 the installed capacity would double. Other large-scale storage options, such as compressed air storage,
exist but are not widely deployed.
Today, less than 1 GW of other storage technologies but pumped hydro is deployed worldwide. To address
minute-to-minute or hour-to-hour variability, the latest developments in more decentralised electricity storage technologies – such as batteries and flywheels – are of interest. These decentralised solutions would allow
residential users to increase their self-consumption to beyond 60%, and it would allow generators of variable
renewable power to smooth their output and provide grid quality services.
For more details, please visit www.irena.org/remap.
Th e Int e r na t iona l Re n ewa b l e E n e r g y Ag e n cy ( I R EN A ) i s a n i nt er gover nm ent a l o r ga ni s a t i o n p ro m o t in g the
wid e s pread an d i n c re as e d adop ti on an d s us t a i na bl e us e o f a l l fo r m s o f renewa bl e ener gy wo r l d w id e ,
­i nclud ing bioen e r g y, g e oth e r m al e n e r g y, hy d ro p ower, o cea n ener gy, w i nd ener gy a nd s o l a r ener gy.
w ww.ire na.or g
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Fac t sh e et 10: Int egr a t in g Var ia bl e Re n ewa b le s
In most cases, energy storage is not a necessity, although variable renewables could become an
important driver for deployment of storage options.