CONNECTING RENEWABLE ENERGY WITHIN THE GRID

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CONNECTING RENEWABLE ENERGY WITHIN THE GRID
Ahmed S. Bouazzi École Nationale dIngénieurs
de Tunis (ENIT) University of Tunis El Manar PO
Box 37, Tunis 1012, Tunisia asbouazzi_at_gmail.com
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introduction
The new context of increased concern over urban
air pollution, global warming and fossil
resources depletion pushes the states and the
regional alliances to introduce renewables into
their energy resources to feed their industry and
their population with energy. Despite the fact
that the Arab states are the biggest oil and gas
producer in the world, it is wise to prepare a
safe future for their children by introducing
renewables among their energy sources and hence
safeguarding the environment from pollution. A
clean environment will represent a treasure in
the future if we take into account the
overpopulation and the scarcity of clean spaces.
In this frame, this paper presents a study about
the world photovoltaic (PV) production and net
metering. In the case of Tunisia, it simulates
the PV energy production depending on the site
and on the amount of sunshine and estimates its
profitability.
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Comparison of external costs of electricity
Range of typical retail prices of electricity is
40 to 80 mEuro/kWh
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An estimate of the physical impacts of global
warming, for 2xCO2 (2.5C warming)
Type of damage Damage indicator Agricultural
production loss 0.23 of GDP Loss of forest area
106 km2 Fishery, reduced catch 7 ? 106
t Increased electric demand 350 TWh Reduced
water availability 230 km3 Coastal protection
expenditures 109/yr Dry land loss 0.1 106
km2 Wetland loss 0.3 106 km2 Premature
deaths 140,000 Migration millions Deaths
due to hurricanes thousands/yr
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Typical damage costs per kg of pollutant emitted
by power plants in Europe
Pollutant Impact Cost, /kg PM10 (primary)
mortality and morbidity 15.4 SO2 (primary)
crops, materials 0.3 SO2 (primary) mortality
and morbidity 0.3 SO2 (via sulfates) mortality
and morbidity 9.95 NO2 (primary) mortality and
morbidity small NO2 (via nitrates) mortality
and morbidity 14.5 NO2 (via O3) crops 0.35 NO2
(via O3) mortality and morbidity 1.15 VOC (via
O3) crops 0.2 VOC (via O3) mortality and
morbidity 0.7 CO (primary) morbidity 0.002 As
(primary) cancer 171 Cd (primary) cancer
20.9 Cr (primary) cancer 140 Ni (primary)
cancer 2.87 Dioxins, TEQ cancer 1.85 107
CO2 Global warming 0.029
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Cost of environmental damages for various power
generation cycles. -cents/kWh
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Net Metering Schematic Diagram
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THE ECONOMICS OF NET METERING
Any producer may sell the energy to the
distributor at the gross rate while the
distributor (the utility) transports it to the
consumer and sells it at the retail price. A PV
system that produces during the day more than the
owner consumption spins the meter backwards
during the day while the meter spins forwards
during the night since the major individual
energy consumption happens during the evening.
The PV system owner may sell then the energy in
excess to the utility like any other energy
producer.
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Cumulative installed PV Power (MW)
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Production and consumption of fossil fuel in
Tunisia
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Installed PV systems in Tunisia from 1997 to 2003
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Installed PV systems in Tunisia
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In the frame of the new economic policy, Tunisia
opened its market to the private sector in many
domains, especially in the energy production
sector. A tender has been launched in 1997 for
a build-own-operate (BOO) electrical power plant
to provide electricity for the fast growing
energy market. The winner of the bid is CEA
(Community Energy Alternatives), which invested
in Tunisia to achieve the 470 MW BOO Combined
Cycle Power station in the site of Rades in the
north east of Tunisia, near the capital Tunis,
together with all the additional installations.
The construction of the plant has been completed
last winter, the cost is estimated at 260 Million
USD, and it is expected to supply 23 of the
National demand for electricity. Tunisia has
produced in 2002 more than 12 Terawatt-hour.
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The national company STEG will continue to
distribute and sell the energy to the customers.
The gross price will be near 0.030 Tunisian Dinar
while the retail price is near 0.100 TND (1 TND
equals roughly 0.8 USD). This way of energy
business opens a real opportunity to renewables
to be among the producers of energy, and net
metering is no more a special operation since the
renewable energy plant owner may sell the energy
like any other producer. Already a 20 MW wind
farm, owned by the national electric company
(STEG) is connected to the grid. It is expected
that more wind farms will be installed by 2006 to
produce 100 MW.
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Why PV ?

• Portability many kinds of PV systems can be
  moved about easily.
• Reliability they operate for long periods with
  little maintenance.
• Low operating costs the fuel is free and there
  are no (or few) moving parts.
• Low environmental impact they are quiet and
  nonpolluting (no greenhouse gas emissions).
• Modularity power output can be increased by
  adding more modules.
• Safety they are not flammable.
• Versatility they operate well in almost any
  climate.
• Ease of installation no heavy construction
  equipment is required
• Short lead time prepackaged PV systems are
  available, and utility easements aren't needed.
• Stand-alone capability they operate in remote
  areas far from power lines.

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Tunisia has now a large government funded PV
program aimed to bring electricity to remotes
rural houses. By the end of 2002, the national
agency for renewable energies (ANER) installed
already more than 10,000 stand-alone PV systems
to electrify remote houses in the countryside. It
is foreseen that around 10,000 more remote houses
will be electrified in the same way by 2010. Many
demonstration PV installations has been installed
since 1980, among them a 28 kW peak PV plant to
supply the village of Hammam Biadha, 150 km
southwest of Tunis. This plant installed with the
help of US AID and owned presently by the
National Electric Company (STEG) will be
connected to the grid in the near future.
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Average amount of sunshine(hours/year)
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Daily Global In-plane Irradiation(Wh/m2/day)
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THE OUTPUT OF 1 kWp PV SYSTEM OVER ONE YEAR
We made the simulation for the case where we have
panels with a peak power (PP) of 85 Watt under an
incident light of 1000 W/m2, dc-ac inverters with
efficiency (hIn) of 93 and a maximum energy need
(EN) of 7000 Wh per day. EP is the energy given
by a panel, it is given by
The number of PV panels to satisfy one house need
is
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Monthly output energy from a PV system made up of
17 panels, each panel has a peak power of 85 W,
connected to the grid through a dc-ac inverter
with an efficiency of 93. The simulation was
made with the meteorological data of Tunis site
(3648 N, 1011 E)
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A map of Tunisia, the blue lines show the annual
output of 1 kWac PV system (in MWh/yr)
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COST-COVERING PRICE
The market price of an installed 1,445 Wac PV
system is presently around 15,000 TND. One peak
watt of this system produces an amount of energy
from 34 to 44 kWh over 20 years depending on the
site. If we assume a 4 fixed interest rate
long-term loan over 20 years, a 5 rate of
discount and a 3.7 inflation rate, one can
extract the components of the cost of one
kWh. The amortization cost is 0.410 TND per kWh,
the maintenance cost is 0.050 TND per kWh and the
interest rate costs 0.010 TND per kWh. This gives
a grid connected PV kWh price of 0.470 TND, which
represents the cost covering price.
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The cost-covering sell back price of the PV kWh
for six cases in Tunisia. The lifetime of the
system is supposed to be 20 years
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Net metering is a way to allow people to buy
photovoltaic energy within the grid. The present
PV kWh price is too high to make it cost
effective by itself. Funds must be found from the
collectivity to pay the difference between the
conventional kWh price and the PV kWh price.
External costs of energy from fossil fuels could
be used to subsidize PV electricity producers.
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• Introducing PV systems among the sources of
  energy production is a must.
• Developing research on renewables and pollution
  is a must.
• By doing this
• We will master the technology of the PV
  connection to the grid.
• We will safeguard our environment by using less
  polluting sources of energy.
• A clean environment will represent a treasure in
  the future if we take into account the
  overpopulation of the globe and the scarcity of
  clean spaces.