mirrors instead of the parabolic-shaped collectors
in trough CSP. The mirrors are close to the
ground, have a low wind load, a compact simple
structure, and high land use efficiency; (ii) the
heat transfer tubes do not need to be a vacuum,
which simplifies the design and lowers the
overall cost of the system; and (iii) the system’s
concentration ratio, operating temperature and
system efficiency are low.
Currently, trough CSP technology is mature;
tower CSP technology is approaching an early
stage of maturity and has great potential; Fresnel
and dish technologies are still at the demonstration stage. There is still much to do in CSP
technologies.
(3) Trends in related technologies
First, wind turbines will use longer and lighter
blades of modular design, thereby improving
power generation efficiency. The number of
direct drive (gearless) wind turbines is expected
to increase.
1. Wind turbines will use longer and lighter
blades with modular design. As wind
resource-rich regions with low wind velocity
become hot spots for development, the swept
area per kilowatt generated needs to be
increased to capture more energy. Compared
with the past decade, the rotor diameter and
rated power of wind turbines have increased
by 70% and 50–100% respectively. Currently, the average rotor diameter of
low-velocity turbines is 116 m and is forecast
to reach 160 m in the next decade, with swept
area and annual availability expected to
double. However, a new problem will then
arise—ultra-long blades make transport and
hoisting on challenging terrain difficult. Road
construction, piling and hoisting costs will get
higher and safety risks could increase.
Modular blade technology simplifies production, ensures product quality and facilitates
transport and erection.
2. The proportion of direct drive (gearless) wind
turbines is expected to rise. Direct drive (including excited and permanent magnet direct
drive) wind turbines is a hot area of research.
Germany-based Enercon and other vendors
using excited direct drive systems have
around an 8% share of the global market.
These turbines feature stable performance and
mature technology. Permanent magnet direct
drive wind turbines have no gearbox and
avoid some of the mechanical faults associated with gearboxes. The magnet remains
stable, withstanding vibrations and temperature variations.
Second, improved conversion efficiency and
lower cell production costs characterise solar PV
technologies.
1. PV cell conversion efficiency is improving.
The conversion efficiency of monocrystalline
silicon cells is currently about 19%, while
that of third-generation polycrystalline silicon
cells is around 18%. New technologies will
improve crystalline silicon cell conversion
efficiency over time. Passivated emitter rear
cell (PERC) technology improves cell conversion efficiency by adding a dielectric passivation layer to the back of the cells.
2. Cell production costs are falling. Fierce
competition is forcing cell manufacturers to
lower production costs in several ways. The
first method is to improve conversion efficiency through technical progress, primarily
through metal wrap through (MWT) and
interdigitated back contact (IBC) technologies. Experience shows that when cell conversion efficiency is improved by 1%,
production costs are lowered by 7%. The
second method is to reduce material consumption and thus costs. The cost of cell
processing comes mainly from the slurry. It is
difficult to lower the cost of slurry because it
contains silver and other commodities.
Therefore, manufacturers choose to reduce
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S. Zifeng and N. Dickens
in trough CSP. The mirrors are close to the
ground, have a low wind load, a compact simple
structure, and high land use efficiency; (ii) the
heat transfer tubes do not need to be a vacuum,
which simplifies the design and lowers the
overall cost of the system; and (iii) the system’s
concentration ratio, operating temperature and
system efficiency are low.
Currently, trough CSP technology is mature;
tower CSP technology is approaching an early
stage of maturity and has great potential; Fresnel
and dish technologies are still at the demonstration stage. There is still much to do in CSP
technologies.
(3) Trends in related technologies
First, wind turbines will use longer and lighter
blades of modular design, thereby improving
power generation efficiency. The number of
direct drive (gearless) wind turbines is expected
to increase.
1. Wind turbines will use longer and lighter
blades with modular design. As wind
resource-rich regions with low wind velocity
become hot spots for development, the swept
area per kilowatt generated needs to be
increased to capture more energy. Compared
with the past decade, the rotor diameter and
rated power of wind turbines have increased
by 70% and 50–100% respectively. Currently, the average rotor diameter of
low-velocity turbines is 116 m and is forecast
to reach 160 m in the next decade, with swept
area and annual availability expected to
double. However, a new problem will then
arise—ultra-long blades make transport and
hoisting on challenging terrain difficult. Road
construction, piling and hoisting costs will get
higher and safety risks could increase.
Modular blade technology simplifies production, ensures product quality and facilitates
transport and erection.
2. The proportion of direct drive (gearless) wind
turbines is expected to rise. Direct drive (including excited and permanent magnet direct
drive) wind turbines is a hot area of research.
Germany-based Enercon and other vendors
using excited direct drive systems have
around an 8% share of the global market.
These turbines feature stable performance and
mature technology. Permanent magnet direct
drive wind turbines have no gearbox and
avoid some of the mechanical faults associated with gearboxes. The magnet remains
stable, withstanding vibrations and temperature variations.
Second, improved conversion efficiency and
lower cell production costs characterise solar PV
technologies.
1. PV cell conversion efficiency is improving.
The conversion efficiency of monocrystalline
silicon cells is currently about 19%, while
that of third-generation polycrystalline silicon
cells is around 18%. New technologies will
improve crystalline silicon cell conversion
efficiency over time. Passivated emitter rear
cell (PERC) technology improves cell conversion efficiency by adding a dielectric passivation layer to the back of the cells.
2. Cell production costs are falling. Fierce
competition is forcing cell manufacturers to
lower production costs in several ways. The
first method is to improve conversion efficiency through technical progress, primarily
through metal wrap through (MWT) and
interdigitated back contact (IBC) technologies. Experience shows that when cell conversion efficiency is improved by 1%,
production costs are lowered by 7%. The
second method is to reduce material consumption and thus costs. The cost of cell
processing comes mainly from the slurry. It is
difficult to lower the cost of slurry because it
contains silver and other commodities.
Therefore, manufacturers choose to reduce
342
S. Zifeng and N. Dickens