Page 50 - Impiantistica industriale Luglio Agosto 20147

diffculties during its scaling-up to commercial integration with the smart distribution grids are
size. It’s thought that these problems might be designed specifcally for facilitating the transition to
adequately addressed with suffcient time and new ways of generating and distributing electricity.
investment of resources. Although much of the These batteries could be small or medium scale and
construction as been completed at the Columbus distributed within the consumption area. The use of
site, none of the key electrochemical components the energy storage capabilities of these batteries
from Regenesys had been installed. could be optimized by battery aggregation and
Today different design variants are under study control technology to manage them also in a Virtual
where the used Redox couples are: vanadium, zinc- Energy Storage System (VEES).
bromine (Zn-Br), polysulphide-bromide (PSB) etc. The Distribution Grid Operator is supported by a
A vanadium redox battery consists of an assembly control technology comprising a grid EMS (Energy
of power cells in which the two vanadium base Management System) and communications via
electrolytes are separated by a proton exchange battery SCADA (Supervisory Control And Data
membrane. The electrolytes include electrolytically Acquisition).
dissolving vanadium pentoxide (V O ) in sulfuric acid Different modes of control could be envisaged, but
2
5
(H SO ). The solution remains strongly acidic in use. one solution looks the VESS managed by a central
2 4
facility that aggregates multiple small and medium
5. Defning criteria of the energy storage units (also of different technologies)
that can be utilized in the same manner as a single
installation of the battery conventional storage.
storage systems (and of The following two scenarios that describe control
functions for battery aggregation are.
additional control required
within distribution grids) 5.1. Load Frequency Control by
Today’s and futures power grids are characterised battery aggregation
by a high share of renewable energy sources. This
leads to a massive injection of fuctuating power, The sequence of this LFC could be as follows:
which needs to be balanced by battery energy • grid operator defnes through the battery
storage. SCADA the total capacity of batteries to be
There are the following two level of electrical used for this aggregation;
network operation: • SCADA calculates the charging/discharging
• Transmission System Operator (TSO) that control value for each stationary battery;
manage the energy produced by large power • each battery charges and discharges
plants and transported by high voltage according to the defned charging / discharging
transmission lines at national or regional level; control values, in agreement with the grid
• Distribution Network Operations (DNOs) are requirements.
the companies in charge to distribute electricity
at local level and that are also responsible of
the integration of renewables connected to the 5.2. Reserve margin by battery
local grid. aggregation
Battery energy storage solutions and their The key of this scenario is the Reserve Margin

Fig. 3 - Energy storage sy-
stems market for solar PV
plants from 2015 to 2030
vs application (Billion Euro)
2015 2020 2025 2030

46 Impiantistica Italiana - Luglio-Agosto 2014