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300 Sustainable Cities and Communities Design Handbook

was successfully launched in the city of Juiz de Fora in Brazil. Having an
installed capacity of 87 MW, the plant can supply the power demand of the
150,000 inhabitants (Power-technology, 2015). On the basis of an energy
content of 6.53 kWh per liter of ethanol (University of Wisconsin, 2016)
and a similar conversion efficiency for the power plant (Ethanol Producer
Magazine, 2010), the electricity generation capacity from the total annual
ethanol production would amount to approximately 470 GWh, representing
21% of the total electricity generation in 2015 (SM, 2016a).

Flexible Generation and Storage
Some of the renewable sources of energy proposed among the roadmap
technologies are intermittent in nature, implying that their availability varies.
For instance, the output of PV and wind power plants will depend on the
amount of solar irradiance and wind characteristics at the site, respectively.
Conventional power systems are used to deal with variability on the load side
and balancing supply accordingly. The integration of RE in the grid brings
variability on the supply side as well. At high levels of RE integration, the
possibility of large fluctuations in generation within small timescales presents
new challenges for power systems. To deal with the intermittency of RE
resources and maintain reliability, the system must be flexible enough to
closely match the electricity demand at all times. Therefore on the supply side,
the grid should be upgraded to feature power plants with wide operating
capacity ranges and fast ramping rates. Open-cycle gas turbine units are ideal
for sudden load because they have the ability to start-up and reach full power
output within minutes. On the demand side, efficiency programs and time-
of-use pricing (demand response), can also address the balancing issue in an
economical way by decreasing or shifting load as needed. Another important
measure to reduce the flexibility requirements of the power system is the
development of more accurate forecasting and scheduling systems. In recent
years, much progress has been made in forecasting intermittent RE output
(Kaur et al., 2016).
Adequate storage capacity is also central for enhancing flexibility in power
systems with large shares of clean but variable RE. Much research has been
dedicated lately to the development of efficient and high-capacity storage
technologies, including mechanical storage such as pumped hydro, compressed
air energy and flywheels, batteries, supercapacitors, and fuel cells. Due to their
fast response time, storage systems are required to provide power during the
interval between the falling off of intermittent RE output and the moment that
flexible generation capacity is ready to come online. Several of the existing
hydropower stations in Mauritius are situated in sites with topographical
features that would enable coupling of PV or wind power with pumped storage
systems. Convenient storage technologies like batteries, fuel cells, and super-
capacitors are still being optimized, and it is anticipated that they will become