Page 17 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

4 Renewable Energy Devices and Systems with Simulations in MATLAB and ANSYS ®
®

Share in global net capacity additions (%) 100 0 58%
Renewables

50

42%
50

100 Nonrenewables
01 02 03 04 05 06 07 08 09 10 11 12 13
Year (2001–2013)

FIGURE 1.4 Annual installations of renewables and nonrenewables as a share of the net total additions
based on data available from IRENA statistics.

In Europe, Denmark has now 60% of its electricity supplied from renewable resources, mostly
wind and a little from solar [3]. This is the result of pioneering efforts started in the 1970s and of
the systematically favorable governmental policy over the decades since then. Two other countries,
Portugal and Spain, generate today approximately 30% of their electricity from renewables.
Some of the early technological developments of PV cells, wind turbines and farms, and large
solar thermal power plants originated in the United States. Although here the contribution of renew-
ables remains relatively low, at only 10% of the total power sector electricity supply in 2010, exten-
sive studies have been done focusing on 80% of all U.S. electricity generation from renewables in
2050 [4].
Worldwide, the shift toward renewables is most significant. This is, for example, documented in
two papers reporting on recent developments and state-of-the-art technology in China and India pub-
lished in a special issue, 43(8–10), 2015, of the Electric Power Components and Systems journal [5, 6].
Among the technologies that supported the growth of renewables, power electronics has been
representing a major technology enabler. The power electronics converters have made it possible to
connect renewable energy generators to the legacy power systems, as schematically illustrated in
Figure 1.5, improving the efficiency of energy harvesting through dedicated controls. Furthermore,
power electronics is extensively used on the consumer side and it is a core technology for the new
smart grid.
Wind turbine systems have experienced substantial transformation over the years. In the 1980s,
a wind turbine of 50 kW was considered large, while today’s typical wind turbines are rated at 2–3
MW and design is now approaching 10 MW. Much of the development for larger units was driven
by the need for lower cost of energy, while some of the electric technology changes were imposed
by performance improvements, especially in terms of grid connection.
Older designs that are based on doubly fed induction generators [36] for which only the rotor
circuit employs a power electronics converter of reduced rating, while the stator winding is con-
nected to the AC line, are being replaced by newer topologies with full-scale power converters and
induction, permanent magnet, or wound-field synchronous generators (see Figure 1.6). An example
of the state-of-the-art wind turbine nacelle, incorporating gearbox, electric generator, and power
electronics converter, is depicted in Figure 1.7.
For solar energy, it can be used in different ways. The power generation is based on the PV effect,
where the voltage or current level is very low for a single solar PV cell. Hence, in practical applica-
tions, a considerable number of solar PV cells have been connected in parallel and in series in order to