Solar Energy Perspectives - IEA

Chapter 11: Testing the limits
between peak power and base load would become less relevant, as flexible solar thermal
electricity could at all times complement inflexible variable renewables (Figure 11.2). Recent
analysis suggests that an average of two to four hours of storage in solar electricity plants in
the United States would be enough to run the electricity system of that country on very high
proportions (93% to 96%) of solar and wind (Mills and Cheng, 2011a).
Electricity demand
Figure 11.2 Base load versus load-matching
A. with baseload
Fast peaking
( e.g. gas, hydro, combustion turbine)
Intermediate peaking
( e.g. natural gas combined cycle)
Baseload (coal or nuclear)
1 am 6 am 12 pm 6 pm 12 am
B. without baseload
Flexible source ( e.g. solar thermal with storage)
Inflexible source ( e.g. wind or solar without storage)
Electricity demand
Source: Mills and Cheng, 2011b.
Key point
Base load concept may not survive very high penetration of renewables.
In sunny countries with lower DNI, costs of photovoltaic electricity would not be a limiting
factor, but variability would be, unless non-concentrating solar thermal electricity takes off.
In most cases hydro power offers significant potential in such countries, usually of wet
climate conditions. Fully-flexible hydro power would balance inflexible PV production.
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© OECD/IEA, 2011