This presentation reveals the solar energy potential of Nigeria and a cheap way of tapping into it using agricultural wastes.

1. SYNTHESIS OF AMORPHOUS
SILICON NANOPARTICLES
FROM AGRICULTURAL
WASTES FOR SOLAR
APPLICATIONS – A REVIEW
S. B. Hassan, J. A. Adebisi, O. A. Ojo and J. O. Agunsoye

2. INTRODUCTION
 Energy generation and supply are problems that attract attention of all
nations because human welfare in modern life is closely related to the
amount and quality of energy utilized.
 There has been a lot of projections on the nature and quantity of energy
that will be required in the next decades.
 Institutions such as the International Energy Agency (IEA), the U.S. Energy
Information Administration (EIA), and the European Environment
Agency record and publish energy data periodically.
 These data help in the understanding and revealing of the World Energy
Consumption systemic trends and patterns, which could help frame current
energy issues and encourage movement towards collectively useful
solutions.
 The International Energy Agency has projected that energy demands will
continue to increase until 2030.
2

3. World* total primary energy supply by fuel
71,013 TWh 155,505 TWh
*World includes international aviation and international marine bunkers;
** Peat and oil shale are aggregated with coal; and
***Includes geothermal, solar, wind, heat, etc.
IEA, (2014). Key World Energy Statistics.
3

4. World total primary energy supply by region
71,013 TWh 155,505 TWh
*Asia excludes China.
** Includes international aviation and international marine bunkers.
OECD: Organisation for Economic Co-operation and Development
IEA, (2014). Key World Energy Statistics.
4

5. World electricity generation (TWh)
IEA, (2014). Key World Energy Statistics.
5

6. Electricity generation in Africa (TWh)
IEA, (2014). Key World Energy Statistics.
6

7. Electricity production to include Nigeria (kWh)
Index-Mundi. Electricity production (kWh). 2014 [cited 2014 12/11/2014]; Available from:
http://www.indexmundi.com/facts/indicators/EG.ELC.PROD.KH/compare?country=ng#country=dz:eg:ng:za.
7

8. Population and electricity consumption per
capita for selected Africa countries
Extracted form: BP. Statistical Review of World Energy 2014.
PRB. Population Mid-2014.
8

9. Renewables energy consumption - Solar (TWh)
IEA, (2014). Key World Energy Statistics.
9

10. What could be done in Nigeria?
 In 1998, Aduroja et al. reviewed the potential of photovoltaic
system in Nigeria.
 In 2005, An electricity reform was suggested by Ikeme and
Ebohon that include increasing efficiency and share of
renewables in energy generation, as well as minimising
environmental damage.
 In 2008, Akin Iwayemi suggested that one of the basic factors in
securing the electricity future in Nigeria is the energy mix (crude
oil, natural gas, coal, hydro, solar, wind and biomass) over the
next several decades.
 In 2012, Oji et al. presented the viabilities for power generation
in Nigeria by the utilization of the sun’s energy through solar-
thermal or photovoltaic technologies.
 There are several researches that has been done that focused
on how to solve the problems in this sector.
10

11. Renewable energy
 One of the recurring suggestion here is the solar photovoltaics
technologies.
 Solar photovoltaic (PV) energy has been seen as an elegant and
effective renewable energy resource that has proven to be a
promising candidate for provision of clean and sustainable power.
 A solar photovoltaic (PV) module works by converting solar
radiation directly into electricity, using semiconductor technology.
 From researches, it was observed that Nigeria could generate about
600,000 MW of electricity by deploying solar photovoltaic panels of
only 5% efficiency from just 1% of her land mass.
 In the first quarter of 2014, Federal government of Nigeria planned
to fully harness the solar energy potential of the country through the
use of solar cells.
 This has shown positive results in many countries like Turkey, EU
member states, India, Brazil, Algeria, etc.
11

12. What do we have?  The energy available in the
sun is more than 10,000 times
that required on the planet.
 It is the cheapest form of
energy in areas where its
reception is high.
 It costs nothing but space and
gadgets required to tap into it.
 The average radiation in
tropical and sub-tropical
regions located in developing
countries can be compared
to that of annual global
radiation of about 1600 – 2200
kWh/m2.
12
EIA, (2011). World map of solar resources. US
Energy Information Administration.

13. 13
http://commons.wikimedia.org/wiki/Fil
e:Solar_panels_on_house_roof.jpg
http://en.wikipedia.org/wiki/
File:Nellis_AFB_Solar_panels.j
pg
http://en.wikipedia.org/wiki/Solar
_power_in_Africa#mediaviewer/Fi
le:SolarGIS-Solar-map-Africa-and-
Middle-East-en.png
http://www.victor.sa.gov.au/page.aspx?u=
822
http://wordlesstech.com/wp-
content/uploads/2011/05/Solar-
panels-in-France.jpg
http://wordlesstech.com/2013/
11/19/kyocera-mega-solar-
power-plant/
http://ts2.mm.bing.net/th?id=HN.607988316
580678329&pid=15.1&P=0
http://ts2.mm.bing.net/th?id=HN.60
8028010674719873&pid=15.1&P=0
http://ts4.mm.bing.net/th?id=HN.608043064
528995095&pid=15.1&P=0
Feasibility of achieving the suggestions

14. Focus of this paper
 Is there a way of harnessing the solar energy with our local
materials?
 Are there agricultural wastes that could be used?
 Burning of wastes increases the amount of greenhouse gas emission.
 Improve the economic status of the farmers.
 Are these materials in enormous production?
 Will their conversion be economical and environmentally
friendly?
 What are the researches that has been done using these
methods?
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15. Cassava peels
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 Nigeria is the largest cassava producing country in the world with a tonnage of
about 30 million tonnes as at 2002.
 Cassava peels can represent 5 to 15% of the root which invariably means 4.5
million tonnes of cassava peel waste could be produced.
 Mostly in Nigeria, they are used for raising goats.
 The part that is needed in the peel is not what the goats need.

16. PHOTOVOLTAIC MATERIALS
 Silicon solar cells make up 95% of solar cells and are the most developed and
commercialized types of photovoltaic cells.
 In terms of purity level, silicon could be classified in priority as either
 semiconductor/electronic grade (EG-Si),
 solar grade (SOG-Si) or
 metallurgical grade (SoG-Si).
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PV materials
Crystalline silicon
86% market share
Thin film
Organic/polymer
Hybrid PV polymer
Dye-sensitized
CdS/CdTe
Amorphous silicon
13% market share
CIS/CIGS
Single junction
Double junction
Triple junction
Mono-Crystalline
Poly-Crystalline
GaAs

17. SoG-Si production/MG-Si purification
 The Siemens based processes (thermal decomposition of silane and/or H2
reduction of silicon halides).
𝑆𝑖𝐻4 𝑔 → 𝑆𝑖(𝑠,𝑝𝑜𝑤𝑑𝑒𝑟) + 2𝐻2(𝑔)
𝑆𝑖𝐵𝑟4(𝑝𝑢𝑟𝑖𝑓𝑖𝑒𝑑) + 2𝐻2(𝑔) → 𝑆𝑖(𝑠)(𝑝𝑢𝑟𝑒) + 4𝐻𝐵𝑟
 Metallothermic reduction of Si halide compounds.
𝑆𝑖𝐹4(𝑔) + 4𝑁𝑎(𝑙) → 𝑆𝑖(𝑠,𝑝𝑜𝑤𝑑𝑒𝑟) + 4𝑁𝑎𝐹(𝑠)
 Reduction of silica.
𝑆𝑖𝑂2(𝑠) + 2𝐶(𝑠) → 𝑆𝑖(𝑠) + 2𝐶𝑂(𝑔)
𝑆𝑖𝑂2(𝑠) + 2𝑀𝑔(𝑠) → 𝑆𝑖(𝑠) + 2𝑀𝑔𝑂(𝑠)
 Fluoride processes for the preparation of high purity silicon.
𝐻2 𝑆𝑖𝐹6 + 2𝑁𝑎𝐹 → 2𝐻𝐹 + 𝑁𝑎2 𝑆𝑖𝐹6
𝑁𝑎2 𝑆𝑖𝐹6 →
Δ
2𝑁𝑎𝐹 + 𝑆𝑖𝐹4(𝑔)
 Upgrading MG-Si.
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18. The make of solar cells
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 It should be noted here that a-Si take 8% production share, it has some
advantages.
 Amorphous silicon solar cells can be fabricated on large area and on
different substrates without raw material problem which makes them suitable
for low-cost and mass production.

19. SYNTHESIS OF NANOPARTICLES
No
Starting
material(s)
Reagents/other materials Procedural highlights Product(s)
Particle size
(nm)
1
Corn tissues
(leaves, roots,
stalks, silks, and
husks)
HCl, ethanol solution of
tetrabutyl titanate
Acid pre-treatment, in-situ growth
(impregnation), calcination,
crystallization
Max. Temp. 550 oC
porous
TiO2–SiO2
composites
13.8 – 20.3
2 Rice husk (RH)
HCl, H2SO4, HNO3,
CH3COOH, NaOH, CaO,
NH4OH, EDTA, KOH
Acid pre-treatment, combustion,
leaching, pyrolysis, sol-gel
Max. Temp. 500 °C, 700 °C, 1,000 °C
Silica 6
3
RH (from 2
different sources)
acetic, citric and phosphoric
acids
Leaching, calcination
Max. Temp. 650 oC
Silica 181.2 – 294.7
4 Corn hob
NaOH, HCl, cetyltrimethyl
ammonium chloride
(CTMAC), ammonia
Pyrolysis, sol-gel, calcination
Max. Temp. 700 oC
Silica 305
5
Rice, sylvan
horsetail, scouring
horsetail and larch
needles
HCl, Mg, H2SO4, HF
Hydrolysis, calcination, metallothermic
reduction
Max. Temp. 700 oC
Amorphous
silica
50 – 200
6 sugarcane bagasse
H2SO4, benzene, methanol,
acidified NaCl, KOH,
Pulverizing, isolation, acid-hydrolysis
Max. Temp. 105 ◦C
Cellulose 20-60
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20. PRODUCTION OF SILICON
 Four research works were obtained from previous works.
 Banerjee et al. (1982): RH, HCl, HF, H2SO4, Mg, MgO.  amorphous silica, silicon.
 Mishra et al. (1985): RH, HCl, HNO3, HF, Ca.  amorphous silica, 99.9% silicon.
 Ikram and Akhter (1988): RH, HCl, Mg.  amorphous silica, 99.95% silicon.
 Larbi et al. (2012): RHA, HCl, CH3COOH, PVA, Mg.  amorphous silica, 99.3% silicon.
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Pre-treatment
• Washing/rinsing
• Acid leaching
• (RH, HCl, distilled
water)
Silica Production
• Burning in air
• Acid leaching (may
involve several
stages)
• (RHA, HCl, HF,
CH3COOH, H2SO4,
HNO3)
Silicon production
• Metallothermic
reduction
• Acid leaching (may
involve several stages)
• (Silica, Mg/Ca,HCl, HF,
CH3COOH, H2SO4, HNO3)

21. PURIFICATION OF SILICON
 This is an essential step in industrial SoG-Si production.
 It has been employed for upgrading MG-Si to SoG-Si at
lower cost.
 The various methods could be grouped as follows:
21
Leaching
Ladle treatment (slagging, gas blowing)
Solidification methods
Crystallization methods
Solvent refining
Ion exchange
Vacuum methods

22. CONCLUSION
 Energy generation and supply are still challenges in Nigeria.
 Waste generation and management in the country constitute
to the environmental pollution and their conversion to wealth is
still low.
 Renewable energy has been seen as the solution to energy
challenges and climate change.
 Conversion of waste to wealth could ameliorate our
unemployment challenges and reduce environmental
problems.
 This review has been writing to convert some agricultural
wastes to renewable energy sources in the country.
 The silicon grade that is aimed will be focused in solar energy
application.
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23. Await your
contributions
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