ENGR101 Week 1 Assignment Analysis
ENGR101 Assignment 3, 2014
Energy Units, Conversions and Estimation
The aim of this assignment is to further develop your skills in:
using and converting units
using an appropriate number of significant digits
estimating values
writing down assumptions used in your calculations
checking that answers are sensible
calculations related to energy in various forms
This assignment is due at 5 pm on Friday 11 April. It is worth 8% of your final mark in
ENGR101. You may hand write the answers; there will be no extra marks for a wordprocessed answer. There is no need to write a full report, but your working and answers must be clear enough to enable a first year science or engineering student to understand what you have done …show more content…
and to repeat the calculation. You must show the method you are using. Submit the hard copy, with a cover sheet, to the ENGR101 assignment boxes on level 2 at the north end of the Engineering Core block near E11 with a standard ENGR101 coversheet.
No electronic submission is required.
Not all the required information is given. You are expected to use textbooks, the Internet, or observation to find other information. Reference all sources of information by writing the references with each answer where the information is used. You may just write internet references as a url rather than as a complete APA reference, e.g., http://en.wikipedia.org/wiki/Calorie. In this assignment, and in all engineering work, all answers are expected to have correct units with an appropriate number of significant figures. Some assumptions will be required, so some questions do not have a single correct answer. State your assumptions.
1.
A candy bar has a marked nutritional value of 350 kilocalorie. How many kilowatthours of energy will it deliver to the body as it is digested? Assume 100% conversion. How many hours can the same amount of energy keep a 100 W light bulb operating?
[2 marks]
2.
A solar hot water supply system requires 80 US gallons of warm water each day heated from 70 degrees Fahrenheit to 120 degrees Fahrenheit. How large a solar collector would …show more content…
be needed? Assume the average incident solar energy flux is 800 BTU per square foot for 12 hours, and the collector efficiency is 75%.
a)
b)
Convert this problem to SI
Solve it using the equation: E = m Cp ΔT
where E is the energy input, m is the mass to be heated, Cp is the specific heat capacity of the liquid and ΔT is the temperature change.
[3 marks]
1
3.
There are a number of alternative light bulbs (tungsten, halogen, compact fluorescent,
LED) available which manufacturers claim use less electrical power and last longer. However some, especially compact fluorescent bulbs, do not seem to last as many hours as claimed.
Consider a typical well-used room in a home/flat you are familiar with. Average energy cost:
26 cents per kWh.
a)
b)
c)
d)
e)
f)
Estimate the number of hours lighting is required per year.
Estimate the light power required.
Use web-based data to construct a table showing the equivalent power required for different bulb types.
Calculate the annual electrical energy use (in kWh) for each type of bulb
Calculate the annual total cost of each type of bulb (including both annual running cost and the annual cost of the bulb itself)
Comment on two methods the manufacturer could use to make a more expensive bulb that you have already considered competitive with the cheapest option.
[7 marks]
4.
NZ Oil & Gas Ltd in its March 2013 Quarterly Report stated that production for three months to the end of March 2013 from the Tui field was 348 973 barrels of oil, and from the
Kupe field production was 4.2 PJ of gas, 18034 tonnes of LPG and 364 683 barrels of light oil.
a)
b)
Convert all these values to energy units (perhaps PJ) and determine the relative proportion from each source.
Compare the total to New Zealand’s total consumption of oil and gas.
[4 marks]
5.
The European Aeronautic Defence and Space Company and NASA
(http://www.airportwatch.org.uk/?p=1499) are working on a hybrid aeroplane with lithium battery storage that can be used to store the energy of descent.
Estimate the usefulness of such storage. For example, consider a modern aeroplane such as a
777-200, and estimate the amount of energy that could be stored in batteries with a mass of say
1% of the total of the aeroplane. How far could the aeroplane fly with the energy that could be stored in the batteries? Search for “fuel economy in aircraft” for useful information.
[5 marks]
6.
A nuclear power supply for New Zealand is a politically sensitive topic, especially after the seismic activity in Canterbury and the Fukushima Daiichi nuclear disaster in Japan. In 2012 the energy used by New Zealand for transportation was 199.96 PJ (NZ Energy Data File,
2012).
a)
How many nuclear power plants would it take to produce enough hydrogen to provide the energy needed for transportation? Assume that the conversion efficiency from electricity to hydrogen using electrolysis is 40%. A typical nuclear power plant produces about 1,200 MW of electricity. Assume that a nuclear power plant operates at 80% of its capacity for the year.
2
b)
Comment briefly on the number of nuclear power plants required to provide energy for transportation in New Zealand from environmental and safety perspectives.
(See http://canta.co.nz/features/the-unclear-nuclear-future-nuclear-power-for-new-z/ for more information) [5 marks]
7.
The blue ENERGY STAR® mark is a shortcut to identifying New Zealand’s most energy efficient products. Only the top 25% of products meet ENERGY STAR’s stringent energy efficiency requirements, so one can be sure the performance of the purchased products is of superior energy efficiency.
For heat pumps, in order to achieve the Energy Star, it must be able to perform efficiently at 2
°C, this is called H2 testing condition (previously H1, tested at 7 °C). This data is submitted to the Government agency EECA (Energy Efficiency Conservation Authority) with supporting evidence. The efficiency of a heat pump can be represented by the Coefficient of Performance (COP).
For a heat pump that produces 4 kW of the heat energy out for 1 kW of electrical energy in, plus 3 kW of heat energy transferred from outdoor environment, the COP is 4 (heat energy out/electrical power in). For an electric bar heater, gas heating and wood fire, the typical COPs are 1, 0.85 and 0.65, respectively.
Table 1. Performance and cost of heat pumps.
Heating
Cost of heat pump
(NZD)
Max. Output
(kW)
Power Input
(kW)
Heat Pump A
2.50
0.45
2500
Heat Pump B
5.00
0.99
2400
Heat Pump C
3.20
0.59
2600
Heat Pump D
3.60
0.75
2000
a) Calculate the star rating (heating only), round to the nearest 0 or 5 with 1 decimal place
(e.g. 3.53 rounds to 3.5), for each heat pump given. Equations for Appliance Star
Ratings can be found from reference 3 under “Air Conditioners – AS/NZS 3823.2 from
April 2010”.
b) Calculate the annual running cost for the heat pumps given.
c) Determine which heat pump is the most economic option overall (for a time period of 2 years). 3
Assumptions:
Average energy cost: 26 cents per kWh
Number of months heat pump used for heating per year: 6 months
Typical hours used per day: 6 hours
Operating condition: Maximum output
References
1. www.eeca.govt.nz.
2. http://www.energyrating.gov.au/products-themes/cooling/air-conditioners/star-rating/
3. http://www.energyrating.gov.au/wpcontent/uploads/Energy_Rating_Documents/Library/General/Labelling_and_MEPS/ap pliance-star-ratings.pdf [4 marks]
4
Energy Units, Conversions and Estimation
The aim of this assignment is to further develop your skills in:
using and converting units
using an appropriate number of significant digits
estimating values
writing down assumptions used in your calculations
checking that answers are sensible
calculations related to energy in various forms
This assignment is due at 5 pm on Friday 11 April. It is worth 8% of your final mark in
ENGR101. You may hand write the answers; there will be no extra marks for a wordprocessed answer. There is no need to write a full report, but your working and answers must be clear enough to enable a first year science or engineering student to understand what you have done …show more content…
and to repeat the calculation. You must show the method you are using. Submit the hard copy, with a cover sheet, to the ENGR101 assignment boxes on level 2 at the north end of the Engineering Core block near E11 with a standard ENGR101 coversheet.
No electronic submission is required.
Not all the required information is given. You are expected to use textbooks, the Internet, or observation to find other information. Reference all sources of information by writing the references with each answer where the information is used. You may just write internet references as a url rather than as a complete APA reference, e.g., http://en.wikipedia.org/wiki/Calorie. In this assignment, and in all engineering work, all answers are expected to have correct units with an appropriate number of significant figures. Some assumptions will be required, so some questions do not have a single correct answer. State your assumptions.
1.
A candy bar has a marked nutritional value of 350 kilocalorie. How many kilowatthours of energy will it deliver to the body as it is digested? Assume 100% conversion. How many hours can the same amount of energy keep a 100 W light bulb operating?
[2 marks]
2.
A solar hot water supply system requires 80 US gallons of warm water each day heated from 70 degrees Fahrenheit to 120 degrees Fahrenheit. How large a solar collector would …show more content…
be needed? Assume the average incident solar energy flux is 800 BTU per square foot for 12 hours, and the collector efficiency is 75%.
a)
b)
Convert this problem to SI
Solve it using the equation: E = m Cp ΔT
where E is the energy input, m is the mass to be heated, Cp is the specific heat capacity of the liquid and ΔT is the temperature change.
[3 marks]
1
3.
There are a number of alternative light bulbs (tungsten, halogen, compact fluorescent,
LED) available which manufacturers claim use less electrical power and last longer. However some, especially compact fluorescent bulbs, do not seem to last as many hours as claimed.
Consider a typical well-used room in a home/flat you are familiar with. Average energy cost:
26 cents per kWh.
a)
b)
c)
d)
e)
f)
Estimate the number of hours lighting is required per year.
Estimate the light power required.
Use web-based data to construct a table showing the equivalent power required for different bulb types.
Calculate the annual electrical energy use (in kWh) for each type of bulb
Calculate the annual total cost of each type of bulb (including both annual running cost and the annual cost of the bulb itself)
Comment on two methods the manufacturer could use to make a more expensive bulb that you have already considered competitive with the cheapest option.
[7 marks]
4.
NZ Oil & Gas Ltd in its March 2013 Quarterly Report stated that production for three months to the end of March 2013 from the Tui field was 348 973 barrels of oil, and from the
Kupe field production was 4.2 PJ of gas, 18034 tonnes of LPG and 364 683 barrels of light oil.
a)
b)
Convert all these values to energy units (perhaps PJ) and determine the relative proportion from each source.
Compare the total to New Zealand’s total consumption of oil and gas.
[4 marks]
5.
The European Aeronautic Defence and Space Company and NASA
(http://www.airportwatch.org.uk/?p=1499) are working on a hybrid aeroplane with lithium battery storage that can be used to store the energy of descent.
Estimate the usefulness of such storage. For example, consider a modern aeroplane such as a
777-200, and estimate the amount of energy that could be stored in batteries with a mass of say
1% of the total of the aeroplane. How far could the aeroplane fly with the energy that could be stored in the batteries? Search for “fuel economy in aircraft” for useful information.
[5 marks]
6.
A nuclear power supply for New Zealand is a politically sensitive topic, especially after the seismic activity in Canterbury and the Fukushima Daiichi nuclear disaster in Japan. In 2012 the energy used by New Zealand for transportation was 199.96 PJ (NZ Energy Data File,
2012).
a)
How many nuclear power plants would it take to produce enough hydrogen to provide the energy needed for transportation? Assume that the conversion efficiency from electricity to hydrogen using electrolysis is 40%. A typical nuclear power plant produces about 1,200 MW of electricity. Assume that a nuclear power plant operates at 80% of its capacity for the year.
2
b)
Comment briefly on the number of nuclear power plants required to provide energy for transportation in New Zealand from environmental and safety perspectives.
(See http://canta.co.nz/features/the-unclear-nuclear-future-nuclear-power-for-new-z/ for more information) [5 marks]
7.
The blue ENERGY STAR® mark is a shortcut to identifying New Zealand’s most energy efficient products. Only the top 25% of products meet ENERGY STAR’s stringent energy efficiency requirements, so one can be sure the performance of the purchased products is of superior energy efficiency.
For heat pumps, in order to achieve the Energy Star, it must be able to perform efficiently at 2
°C, this is called H2 testing condition (previously H1, tested at 7 °C). This data is submitted to the Government agency EECA (Energy Efficiency Conservation Authority) with supporting evidence. The efficiency of a heat pump can be represented by the Coefficient of Performance (COP).
For a heat pump that produces 4 kW of the heat energy out for 1 kW of electrical energy in, plus 3 kW of heat energy transferred from outdoor environment, the COP is 4 (heat energy out/electrical power in). For an electric bar heater, gas heating and wood fire, the typical COPs are 1, 0.85 and 0.65, respectively.
Table 1. Performance and cost of heat pumps.
Heating
Cost of heat pump
(NZD)
Max. Output
(kW)
Power Input
(kW)
Heat Pump A
2.50
0.45
2500
Heat Pump B
5.00
0.99
2400
Heat Pump C
3.20
0.59
2600
Heat Pump D
3.60
0.75
2000
a) Calculate the star rating (heating only), round to the nearest 0 or 5 with 1 decimal place
(e.g. 3.53 rounds to 3.5), for each heat pump given. Equations for Appliance Star
Ratings can be found from reference 3 under “Air Conditioners – AS/NZS 3823.2 from
April 2010”.
b) Calculate the annual running cost for the heat pumps given.
c) Determine which heat pump is the most economic option overall (for a time period of 2 years). 3
Assumptions:
Average energy cost: 26 cents per kWh
Number of months heat pump used for heating per year: 6 months
Typical hours used per day: 6 hours
Operating condition: Maximum output
References
1. www.eeca.govt.nz.
2. http://www.energyrating.gov.au/products-themes/cooling/air-conditioners/star-rating/
3. http://www.energyrating.gov.au/wpcontent/uploads/Energy_Rating_Documents/Library/General/Labelling_and_MEPS/ap pliance-star-ratings.pdf [4 marks]
4