Page 245 - Hybrid-Renewable Energy Systems in Microgrids

222 Hybrid-Renewable Energy Systems in Microgrids

been observed that neither the standalone solar energy system or the wind energy sys-
tem can provide a continuous power supply due to seasonal and periodical variations
for standalone applications [11].
The problems caused by the variable nature of these resources can be overcome by
integrating more than one renewable energy sources in a proper combination, using
the strengths of one source to overcome the weakness of the other. The use of different
energy sources allows improving the system efficiency and reliability of the energy
supply and reduces the energy storage requirements compared to systems comprising
only one single renewable energy source [10]. Due to the complementary characteris-
tics of solar energy and wind energy for certain locations, the RES comprising of both
solar wind with storage offers a highly reliable source of power. This types of RES that
are consist of more than one types of renewable energy sources are called hybrid RES.
Also, Hybrid renewable energy system (HRES) can be a combination of renewable
and conventional energy sources.
The HRES containing both solar and wind energy as the key resources can operate
in two modes: simultaneous and sequential. In a simultaneous mode, the solar and
wind energy system produces energy concurrently while in the sequential mode they
produce electricity alternatively [12,13]. The significant characteristics of HRES are
that they combine two or more renewable power generation technologies to make
proper use of their operating characteristics. That helps the HRES to obtain efficien-
cies higher than that could be achieved from a single power source. HRES may work
in stand-alone or grid connected mode.
The basic component of solar–wind hybrid renewable energy system can be repre-
sented as is Fig. 12.2 [6]. The wind /solar sources and the storage are connected to an
AC/DC bus via converters. That AC/DC bus may be connected to another AC/DC bus
via converters as per network requirement. That AC/DC bus may be connected to the
grid (in the case of grid connected systems) or load.
The design of HRES more complicated in comparison with single energy systems.
The optimum design of an HRES becomes complicated due to various facts, like the
uncertainty of renewable energy supplies, load demand, nonlinear characteristics of

Figure 12.2 The basic component of solar–wind hybrid renewable energy system.