Page 19 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

6 Renewable Energy Devices and Systems with Simulations in MATLAB and ANSYS ®
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Wind turbine Power electronics system Power grid
Gearbox/ Rectifier Inverter
gearless Generator v ge υ DC υ g Transformer
Wind G

AC DC DC AC
υ ge υ DC υ g

FIGURE 1.6 Power electronics–enabled wind turbine energy conversion system, where the generator can be
induction, permanent magnet, or wound-field synchronous generators.

FIGURE 1.7 Bird’s-eye view of the nacelle of a state of the multi-MW wind turbine, including electric gen-
erator and power electronics converters. (Courtesy of Vestas Wind Systems A/S.)

form PV panels and thereby PV arrays. Figure 1.8a shows the one using conventional solar PV cells,
whose efficiency is around 20% [7]. To improve the efficiency, the concentrator PV is also observed
in the market, as shown in Figure 1.8b, where highly efficient multi-junction solar cells can be used.
Grid-connected PV systems, such as the one schematically illustrated in Figure 1.9, comprise a
power electronics DC/DC converter, which ensures a maximum solar energy harvesting through a
maximum power point tracking (MPPT) control, and a DC/AC converter for interconnection to the
grid. PV systems have gained large popularity not only for multi-MW utility-scale power plants/
farms but also as rooftop installations on commercial and residential buildings with ratings as small
as hundreds of Watts (see Figure 1.10), but typically in the kW range.
The dramatic reduction in the price of PV cells contributed to recent very large-scale deploy-
ments. National and regional tax incentives were another contributing factor to the deployment. At
the same time, technological progress made possible the increase in reliability, such that some PV
systems now have an expected life span of 25 years or even longer.
In addition, electricity can be generated in CSP (which is called concentrating solar power or
concentrated solar thermal power) systems [8], as it is illustrated in Figure 1.11. CSP can concen-
trate sunlight by using reflective components (e.g., typically mirrors) to receivers (e.g., a tower or
pines), which can carry or transfer the generated heat. Then, the heat can drive an engine that is
further connected to an electrical generator to produce electricity; or the heat can be used to power
thermal–chemical reactions.