FINAL EXAM FYS-2017
Exam:
Fys-2017 Sustainable energy
Date & time:
Friday, November 23th, 2012, 09.00-13.00
Approved Remedies: Calculator
English-Norwegian or another language dictionary
Pages:
5 (including front page and Appendix)
Contact:
Thomas Beka, phone 95940852
Muhammad Bilal, phone 45674704
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Problem 1: Thermal Power Plants
a)
Briefly describe the fraction of fossil fuels in the total world energy
consumption today. Explain what it is meant by the R/P factor, and
give a rough estimate of the value for the different fossil fuels.
b)
The Urengoy is the second largest natural gas field in the world. Natural gas typically consists 70-80 % methane (CH4 ). During methane
combustion 55 MJ of heat will be released per kilogram, through the
following chemical process:
CH4 + O2 ! CO2 + 2H2 O
Calculate the amount of CO2 that would be released from 1kg methane
combustion?
c)
A typical steam power plant has approximately a 30% efficiency. Find
the amount of methane needed to run a 650MW steam power plant
per day.
d)
Briefly explain what it is meant by the FER factor. Give two reasons
that make biomass unique from the other renewable energy resources?
e)
Households in most developed countries generate a considerable amount
of waste, the so-called municipal solid waste (MSW). When MSW is
used for electricity generation, 360g CO2 will be released per kWh. On
the other hand, 450g CO2 per kWh will be released from a natural gas
power plant.
Calculate the amount of CO2 that would be possible to reduce when
a 2 GWe natural gas power plant is replaced by MSW power plant.
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Problem 2: Wind Power
a)
A wind turbine with 110m rotor diameter is specified with a rated
power output of 3.5MW at wind speed of 15 m/s at standard
air density (⇢) 1.225 kg/m3 . Find the overall efficiency (⌘) of
this wind turbine. Power available in the wind is given by the
following formula:
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PW = ⇢AV 3
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where ⇢ is air density [kg/m ], A is cross-sectional area [m2 ]
swept by the rotor blades and V is wind speed [m/sec].
b)
Compare the efficiency calculated in part (a) to Betz limit.
c)
What are the cut-in, rated and cut-off wind speeds of a wind
turbine? Based on these definitions, sketch the power output
curve for a typical wind turbine.
Problem 3: Hydro Power
a)
Draw a figure of a high head hydroelectric power plant and mark
its head H.
b)
Show that the available power from the water in the plant can be
written as
P = ⇢gQH
where ⇢ is the density of water [kg/m3 ], g is the gravitational
constant [m/s2 ], Q is the flow rate of water [m3 /s] and H corresponds to the head height [m].
c)
A hydropower plant consists of 4 turbines each with 160MW capacity, and runs with a mean head of approximately H=450 m.
Assuming that the efficiency of the turbines are 95%, find the
maximum flow rate through the turbines.
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d)
The above hydropower plant has two of the turbines that can
be reversed and pump the water from the low to the high water
reservoir. It is used for seasonal storage, and the high reservoir
has a capacity of 3×109 m3 of water. Use the numbers given in
(c), and find how many days of stored energy this corresponds
to when the electricity consumption is 120 TWh per year.
e)
Hydro power is a large and well established renewable energy
source. Discuss some of the most important advantages of Hydro
power over wind and photovoltaic.
Problem 4: Nuclear Fission
a)
Consider a typical fission reactor fueled by neutron induced uranium
chain reaction. What is the role of a control rod in the fission reactor?
b)
In a commercial fission power plant it is desirable to hold the multiplication constant k at 1, the so-called critical stage for self-sustained
power production. Describe briefly two possible methods that could be
employed to hold the chain reaction at a critical stage in the reactor?
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Appendix: Periodic table of elements
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