Page 51 - Impiantistica industriale Luglio Agosto 20147

by Battery Aggregation (RMBA) (Virtual Energy is increased to meet demand. And, if demand is
Storage). less than supply then the supply is decreased.
This RMBA enables the grid operator to defne the Large energy storage plants like the hydro pumped
total capacity of batteries for RMBA. storage or the CAES increase their power output
Figure 2 indicates the Capital Cost per Unit Power in case of out of service of large fossil or nuclear
vs Capital Cost per Unit Energy. plants.

6. Discussion of the Position Renewables capacity frming
Paper of Anie Capacity frming uses energy storage, located also
and Confndustria nearby to the renewable plants, to mitigate rapid
output changes from renewable generation due to:
It is evident that any form of energy storage will • wind speed variability affecting wind
be crucial to allow the large-scale deployment of generation;
fuctuating renewable power generation. Figure 3 • shading of solar generation due to clouds;
indicates the trend of the energy storage systems this is important because these rapid output
market for solar PV plants on world wide basis. changes can start to create grid instability.
Anie (The Italian Association of the electro-technical
and electronic Industry) underlines that it will be very
important set up a new planning of energy storage Power quality
systems within the National and the European Renewables instability and volatility can lead to grid
energy program, giving adequate importance to frequency variation, to grid instability and to a total
the development of the electrochemical storage. or partial loss of load power supply. Additionally, the
Anie is also considering important that Italian presence of a static converter as output interface
Industry will sponsor a research program relating to of the generating plants introduces voltage and
the development of energy storage systems and of current harmonics into the electrical system
associated electronic control systems. that negatively affect system power quality. By
integrating distributed power generation systems
7. Different applications closed to the users loads in the electric grid with
energy storage systems, we can eliminate the need
of energy storage systems to transfer energy over long distances through the
within the grids electric grid.
The two man tasks of the energy storage systems
are: Peak shaving
• save the energy during the hours when the Peaking power plants are power plants that
energy produced by renewables is higher of generally run only when there is a high electricity
the consumed energy; demand, known as peak demand. Because these
• maintain the stability of the grid, regaining its plants supply power only occasionally, the cost of
operating equilibrium after being subjected to kWh of these units is high. One option is to use
disturbance. energy produced from renewables and stored
when not require by the grid.
We remember that within an electrical grid there are
the two following different controls [1]:
• primary control: the objective of the primary Load leveling
control is to maintain the balance between Load leveling is one of the best ways to reduce
generation and load; energy pricing, because the most expensive
• secondary control: the objective of the component of the rates we pay is for power
secondary control is to restore the frequency produced by peaking power plants. Some power
to its nominal value. plants run all the time, providing what’s known
as base load, but other ones are in operation,
The range of applications of the energy storage essentially, to cover demand when it spikes
systems are the following. (mid-afternoon in July, when everyone has AC in
operation, for example).
Frequency control
Frequency regulation involves moment-to-moment Rotating reserve
reconciliation between the supply of electricity Energy storage can be implemented into the power
and the demand for electricity. The reconciliation grid as spinning reserve assets. This can replace at
is done continuously. So at any given moment, if lower cost reserve capacity created by generators
electricity demand exceeds supply then the supply that are already synchronized with the power grid

Impiantistica Italiana - Luglio-Agosto 2014 47