25-06-2013, 04:51 PM
Photovoltaics: Emerging Role as a Dominant Electricity Generation Technology in the 21st Century
Photovoltaics.pdf (Size: 1.03 MB / Downloads: 23)
Abstract
Photovoltaics (PV) offer a unique opportunity to solve
the 21st century’s electricity generation problem because solar
energy is essentially unlimited and PV systems provide electricity
without any undesirable impact on the environment. With current
technology of silicon based PV systems, volume manufacturing ,
appropriate business model and without any subsidy, PV
electricity can be generated today at the cost of less than
$0.10/Wp. Silicon based PV systems will continue to dominate
the PV market. Multi-junction PV systems based on Si and other
abundant materials have the potential of manufacturing the next
generation of ultra-low cost PV modules. For storing PV
electricity there are many directions that have the potential of
providing a low-cost solution. Overall, the future of PV electricity
generation for rich and poor all over the world is bright.
INTRODUCTION
The world population is currently about 7 billion and by
year 2100 we expect 10.1 billion people to be living on
planet earth. In developing countries some 2.5 billion
people are forced to rely on biomass (fuel wood, charcoal
and animal dung) to meet their energy needs for cooking.
In countries such as India the acute shortage of electricity is
a fundamental road block in economic growth [1]. Recently
during World Future Energy Summit, United Nations
secretary general Ban Ki-moon stressed the need to end
global energy poverty in a sustainable fashion today, and
issued a stern warning to the international community on
climate change [2]. Providing clean energies to 2.5 billion
people can have far reaching socio-economic impact.
Based on the history of last 150 years it is a known fact
that crude oil is one of the oldest and most complex
commodities in the world heavily underpinned by
geopolitics, and market speculation [3]. Recent estimate
shows that every 1-cent increase in the price of gasoline
costs the US economy $1.4 billion [3]. At the time of
writing this paper oil prices are over $100 per barrel and
are returning back to the highest levels of 2008. According
to International Monetary Fund (IMF) higher oil prices
pose a threat to the global economy [4].
Manufacturing and System Integration
Other than technical knowhow, manufacturing is a
complex matter, involving financing, tax, trade, regulatory
policy, exchange rate and educational skills. In order to
create huge PV markets, the following selection criterion
must be used in the selection of appropriate photovoltaic
module manufacturing technology: (a) no material supply
constraint, (b) low cost of ownership, © low production
cost, (d) the prospect of further cost reduction, and (e)
green manufacturing with no environmental safety and
health issues. In previous publications we have discussed
the fundamentals of photovoltaic manufacturing [9, 11-12].
In this paper only key points are summarized.
Global and Local Economy.
The estimated GDP growth for 2011 for selected
countries is shown in Table I. Based on the oil prices and
demand of oil in recent years it is obvious that excluding
US, the global demand of oil is increasing [17]. The past,
current, and projected population for the most populous
five countries of the world is shown in Figure 4. When
compared to emerging economies, the GDP growth rate of
developed economies is much slower. However, based on
the projected population growth of US in the next couple of
decades, one will expect meaningful GDP growth in future
and one will expect that demand of electricity will rise in
future. Nevertheless, this rise in electricity demand will be
at a much slower rate than that of the emerging economies.
In case of Eurozone, meaningful economic growth is an
open question. Overall, the global GDP will grow and the
demand of electricity will grow significantly. Maximum
demand will be coming from developing economies.
THIRD GENERATION PHOTOVOLTAIC SYSTEMS
The first generation of photovoltaics refers to bulk
silicon solar cells and the second generation refers to
current thin film solar cells. The third generation refers to
higher performance PV systems than the previous
generation of PV systems [36]. In search of devices for
obtaining efficiencies beyond the Shockley-Queisser limit,
some authors consider multi-junction cells, intermediateband
cells, hot carrier cells, and spectrum conversion
devices as part of third generation photovoltaics [37].
Photovoltaic devices based on multiple exciton generation
(MEG) [38] are also part of third generation photovoltaics.
Multi-junction solar cells based on III-V compound
semiconductors are not cost effective for terrestrial
applications. However by using other materials that
satisfies the manufacturing criterion discussed earlier in
section III-A, it is possible to develop third generation
photovoltaics. In recent publications [39, 40] we have
shown that other than multiple junction PV systems, due to
fundamental considerations of device physics and
manufacturing, no other type of third generation PV system
has any prospect of being manufactured.
STORAGE OF ELECTRICITY GENERATED BY
PV SYSTEMS
Batteries and capacitors have the ability to store
electricity generated by PV systems. The energy density
and power density of current energy storage systems is
shown in Fig. 17 [43]. The progress in lowering the cost of
batteries and capacitors has been slow. New electrode
chemistries are under investigation and have the potential
of reducing the cost of batteries. In the future, we are
hoping that the rural market for PV will grow and volumemanufacturing
techniques used by semiconductor industry
are implemented in battery manufacturing, the cost will
drop significantly. Additionally, solid-state capacitors
based on ultra high dielectric materials have the potential
of solving PV electricity storage problem.
RURAL ELECTRIFICATION
As discussed earlier, the energy requirements of
developed and emerging economies are different. Also our
cost analysis has shown that PV is cost-effective today for
places that have no connectivity to the grid. Most of the
people who have no access to any type of clean energy live
in emerging economies and have lot a of sun-shine. Similar
to the massive use of cell phones, the concept of PV based
Nano grid (Fig. 18) can bring the clean energy revolution
to the rural world. Unlike the well-established old grids in
the urban world, Nano Grids can be ultra low-cost and
implemented today. The immediate adoption of Nano Grids
in the rural world will provide a huge growth of PV
industry.
CONCLUSION
In this paper we have presented the current status
and future potential of photovoltaics. With the current
technology of silicon based PV systems, appropriate
business model and without any subsidy, PV electricity can
be generated today at the cost of less than $0.10/Wp. In any
country if subsidies should be cut, they should be cut
uniformly for all type of electricity generation systems.
Silicon based PV systems will continue to dominate the PV
market. Multi-junction PV systems based on Si and other
abundant materials have the potential of manufacturing
next generation of ultra-low cost PV modules. The progress
in storage of PV electricity generation has been slow, but
there are many directions that have the potential of
providing a low-cost solution. The immediate adoption of
Nano Grid in rural world will provide a huge growth of PV
industry. Overall, the future of PV electricity generation for
rich and poor all over the world is bright.