Page 45 - Impiantistica industriale Luglio Agosto 20147

ince most renewable sources are criteria of the electrical system is changing and
intermittent in nature, the integration of renewable power could be transferred from one
renewable energy resources into the area to another also back through transmission
fossil and nuclear power generation lines.
and distribution grid infrastructures is We could envisage the following different cases.
Sbecoming today a challenging task.
It is evident that the speed at which intermittent
renewable resources have penetrated into grid 1.1. Electricity management
could create also security problems within electrical before of the development of
networks operation, if adequate actions are not
taken. renewables
Unlikely electricity has to be produced and supplied During peak periods (consumption higher than
at the same time that the consumer demands it , average load), power suppliers complemented
but wind can generate power only when the wind the power output of the base-load power plants
blows and some time it is not easy to predict when (such as coal fred and nuclear units, but also high
wind stops. In addition energy fows through the effciency combined cycle units) with fexible power
grid in accordance to physical laws which are not generation plants. During the off-peak period when
easily controllable by the grid and power plants less electricity is consumed, costly types of power
operators. This gives rise to mutual infuence generation are stopped.
between systems and creates a series of problems
of control and security which call, in case of the
increase of renewable units connected to the grid, 1.2. Renewables sources power
for the establishment of additional regulations in capacity lower of the minimum
the management of the networks and of the fossil
power plants. grid load
The thermal units , due to the growing of the wind In this case all the kWh produced by renewables
and solar plants, will be in future called upon for are always transferred to the users, no renewables
additional fexibility including quick starts, frequent power must be stored and the grid management is
shutdowns and short interval restarts. almost similar to that of the case 1).
Within this context it is becoming day by day more
important to evaluate the opportunity to store
energy for the following main reasons: 1.3. Renewables sources power
• help to fulfll primary and secondary control of capacity (higher of the minimum
the grid;
• recover energy, when the amount of energy grid load, but lower of the
produced by renewable plants is higher in maximum grid required load)
respect to the energy required by the users. In
this case this energy would be lost. In this case a portion of the kWh produced must
be stored and used when renewable power is not
1. Integrating renewables available.
Utilities can obtain fnancial return from investments
energy storages within the in EES (Electrical Energy Storage) reducing total
grids (vs improving fossil generation costs by eliminating power plants
working only during load peak periods.
power plants fexibility and
their ability to daily cycling) 1.4. Renewables sources power

This paragragh, presented within my paper [1] in capacity (equivalent to the
“Power Gen 2013”, is here proposed again being the
basis to understand the needs of the improvement maximum grid load)
of the energy storage systems and their integration In this case an high portion of the kWh produced
into the transmission and distribution grids and must be stored and used when renewables power
also the required design modifcations of fossil and is not available.
nuclear power plants.
In the past the electricity sector was mainly In the case 3) the Authorities could set up an
vertically set up and the electric power was fowing adequate grid control through the following actions:
from the power plants to the fnal users frst through • retroft of distribution and transmission grids
the transmission lines and subsequently sprayed to and set up energy storages within distribution
the users through the distribution lines. networks nearby to the consumption
Being the renewable units mainly connected to the barycenter:
distribution grids, it is evident that the management - improve fossil power generation units

Impiantistica Italiana - Luglio-Agosto 2014 41