ENG1002 Design Project – S2 2019 – V2 1
Client Brief – Sunshine Lifts – Version 2
1. Project Outline
Sunshine Lifts Pty Ltd manufacture passenger lifts for domestic use and small commercial premises. They have been quite successful to date with their range of standard mains powered lifts, but now plan to develop a product range of ‘solar powered lifts’. That is – a lift powered from solar panels which utilises battery storage to ensure operation is available at all times. To reduce the time to develop the system and keep costs down, the company plans to base their solar powered lift as much as possible on materials and components which they currently stock for their existing products.
Sunshine Lifts are seeking a preliminary design analysis for two sizes of lift – one to suit the domestic market and one to suit their small commercial market. Both configurations only need to service three floors as shown in Figure 1.
The sections of the design requiring analysis include: the lift size, the winch selection, battery selection, solar panel selection and analysis of costs.
Figure 1: Proposed Solar Lift equipment (not to scale)
1.1. Proposed Solar Powered lift
The proposed equipment configuration is shown in Figure 1. The design will use an array of solar panels to charge a battery, which provides electrical energy to the lift controller to drive the winch motor. A cable attached to the lift cage is wound around the winch drum to raise or lower the lift.
Students please note –
Any comments in the brief in red italics are directed at the student for clarification.
Also you MUST READ the IMPORTANT NOTES on the last page of this document.
charger
battery
controller
Solar Panels
Winch Motor
Winch Drum
cage height 2.2 m
Cable
4.5 m
3.0 m
3.0 m
cage width W
ENG1002 Design Project – S2 2019 – V2 2
2. Project Design Sections
The project is divided into five design sections including the costing. This ensures that the requirements of the project are clear. Each section of the design is defined by the set of design parameters, listed in bold. Any company submitting an analysis or design proposal must use the stated letters for these parameters. Each design section requires a technical analysis which is to be summarised in the final design proposal.
The five numbered sections are: (all sections are to be complete for the DP assignment)
1. Lift occupancy, size and mass
2. Winch selection
3. Battery selection
4. Solar panel sizing
5. The cost of equipment
Design Section 1 – Lift occupancy, size and mass
Two lift sizes are required – one to service the domestic market and one for the small commercial market.
Domestic: at least 4 passengers, or 1 wheel chair plus occupant Commercial: at least 8 passengers, or 2 wheel chairs plus occupants plus 4 passengers
The nominal floor area required per passenger is 0.405 m2 per person, but the shape of the area occupied by a person does NOT have to be square. The nominal floor area required for a wheel chair is 0.81 m2 per wheel chair, and the shape of that area must be a square of 0.9 m x 0.9 m.
An important constraint of the design is that the width of the lift door must be no less than 0.9 m wide, to accommodate wheel chair access. (Assumed as the full width d between inside edges of a frame)
Figure 2: Lift cage components and dimensions (not to scale)
w
w = 50 mm= 50 mm
W
W
Floor
Floor — stastainless steel plateinless steel plate
cable
cable
base and top
base and top
Plan view
Plan view
Side view
Side view
glass panels
glass panels
Frame
Frame — stainless steel square tubingstainless steel square tubing
50 x 50 RHS (Rectangular Hollow Section)
50 x 50 RHS (Rectangular Hollow Section)
w
w
6 mm thick
6 mm thick
6mm thick
6mm thick
W
W
w
w
Available passenger floor area Af
Available passenger floor area Af
Glass panels are positioned i
Glass panels are positioned in the steel framesn the steel frames
One panel acts as a door, ignore hinging.
One panel acts as a door, ignore hinging.
h
h = 2.2 m= 2.2 m
inside the frame of the lift
inside the frame of the lift
4 tempered
4 tempered
door width
door width dd
ENG1002 Design Project – S2 2019 – V2 3
The outer width of the passenger cage W is to be specified by the designer, so W is considered a variable for the purposes of analysis. Number of passengers np and wheel chairs nw are to be rounded down to whole numbers.
The lift occupancy and dimensions are defined by the parameters:
 W – the outer width of the lift cage (m) [variable – to be determined]
 w – width of frame material (50 mm) [constant]
 h – height of the cage (2.2 m) [constant]
 d – the width of the door (m) [to be determined]
 Af – the available floor area (m2) [to be determined]
 np – the number of (non-wheel chair) passengers accommodated [to be determined]
 nw – the number of wheel chairs accommodated [to be determined]
The lift materials and mass are defined by the parameters:
 L – the length of 50×50 mm RHS stainless steel required to construct the lift cage (m) [to be determined]
 Ag – the surface area of tempered glass required to fill the four side frames (m2) [to be determined]
 As – the surface area of the stainless steel plate required to construct the floor (include corners) (m2) [to be determined]
 mpm – the mass per linear metre of the 50×50 RHS (4.43 kg/m) [constant]
 ρg – (rho g) the density of tempered glass (2600 kg/m3) [constant]
 tg – the thickness of the tempered glass (6 mm) [constant]
 ts – the thickness of the stainless steel plate (6 mm) [constant]
 ms – the mass of the steel in the frame (kg) [to be determined]
 mg – the mass of the tempered glass (kg) [to be determined]
 Mtare – the mass of the empty lift (kg) [to be determined]
 mp – the mass of a passenger (90 kg) [constant]
 mw – the mass of a wheel chair plus occupant (120 kg) [constant]
 Mnet – the maximum mass of the contents of the lift (kg) [to be determined]
 Mgross – the maximum mass of the lift and its contents (kg) [to be determined]
A sheet of Perspex will be used to form the internal ceiling in the lift, but its cost and mass are considered negligible and hence this component is to be ignored in the design analysis.
Technical Analysis required for Section 1
The technical analysis of this section should determine:
 the relationship between the number of passengers np and wheel chairs nw and the width of cage W
 the relationship between W and the width of the door d
 the relationship between W and the available passenger floor area Af
 the relationship between W and the length L of RHS tubing required to construct the lift cage
 the relationship between W and the surface area of tempered glass required Ag
 the relationship between W and the surface area of the stainless steel plate As
 the relationship which defines the mass of the empty lift cage Mtare
 the relationship which defines the maximum mass of the lift contents Mnet
 the relationship which defines the maximum mass of the lift cage and lift contents Mgross
Note – other quantities (eg. w, h, mpm etc) may need to be included when formulating some of the above relationships.
The technical analysis of this section should also include at least one diagram showing how the maximum number of passengers and wheel chairs can be accommodated for each lift size.
ENG1002 Design Project – S2 2019 – V2 4
Design Section 2 – Winch selection
Figure 3: Winch components and dimensions (not to scale)
The term LIFT – from here on – includes both the lift cage and its contents. Maximum mass should be considered.
The lift is raised and lowered by an electric winch via a cable which is wound around the winch drum of radius r (0.45 m). The winch includes an electric motor and a gear box which drives the drum at a low rotational speed.
 To raise the lift the winch must be able to exert a force F upward on the cable (via the drum) of at least 5 times the weight of the lift. Ie. It must not only support the weight of the lift, but be capable of exerting additional force on the cable to raise the lift. This multiplier is often termed a ‘Design Factor’. Eg. DF = 5.
 To lower the lift the winch is driven in the opposite direction to pay out the cable. It is to be assumed that negligible electrical power is required to lower the lift and the effects of braking are to be ignored.
Only upward motion is to be considered in determining the power and energy requirements for the operation of the lift. For the purposes of this design a ‘trip’ will always be considered as one upward and downward movement of the lift over two floors (6 m).
The lift is required to move from up two floors (6 m) in a time (t) of 10 seconds. The change in the velocity of the lift from stationary to travel speed and when stopping at the next floor is instantaneous, ie. it takes zero time to reach travel speed and zero time to stop.
The rotational speed ω (omega) of the winch and drum can set by the lift controller to any percentage between 20% and 100% of its maximum speed. (How that is achieved is outside the scope of this work.) The rotational speed of the winch and drum must be specified for the design to match the required velocity of the lift.
The torque T delivered by the winch varies with its rotational speed ω as shown in Figure 4 on page 5. The maximum output torque of a winch is the maximum torque that winch would deliver at zero rpm. This is also called the stall torque. The torque (moment) delivered by the winch at the required speed must be able to exert the force F to raise the lift as described above. (Controlling the instantaneous torque requirements to raise the lift and maintain the required speed under different loads is the responsibility of the lift controller and is outside the scope of this work.)
Winch Motor
Winch Motor
Force F
Force F
cage height 2.2 m
cage height 2.2 m
Cable
Cable
4.5 m
4.5 m
3.0 m
3.0 m
3.0 m
3.0 m
Winch Drum
Winch Drum
W
W
radius
radius r = 0.45mr = 0.45m
ENG1002 Design Project – S2 2019 – V2 5
The power required Pr to operate the lift at the required speed and torque (as described above) is calculated from Pr = T * ω. (where ω is in radians/sec) The output power rating of a winch is the maximum power that winch can deliver. If the rated output power of the winch is greater than the power required then it meets the requirement. Utilising a winch with a higher output power rating will provide extra capacity to lift larger loads. (Controlling the instantaneous power requirements to raise the lift and maintain the required speed under different loads is the responsibility of the lift controller and is outside the scope of this work.)
Sunshine Lifts currently stock several models of winch with various output power ratings, maximum torques and maximum speed of rotation as specified in Table 1. Only winches specified in Table 1 and are to be used in preparing a domestic lift design or a small commercial lift design.
Table 1. Winch Selection
Winch Model
Output power rating
(kW)
Maximum output torque (kNm)
Maximum rotational speed (rpm)
M-1
20
25
50
M-2
25
30
50
M-3
35
30
100
M-4
40
38
50
M-5
45
38
100
M-6
50
38
50
Figure 4: Winch speed versus torque curve
The winch and its operation are defined by the parameters:
 Mgross – the maximum mass of the lift cage and lift contents [determined in Section 1]
 t – the time for the lift to travel two floors (10 sec) [constant]
 v – the velocity of the lift (m/s) [to be determined]
 F – the force (N) the winch needs to exert on the cable [to be determined]
 T – the torque (N.m) required to apply the required force [to be determined]
 r – the winch drum radius (0.45 m) [constant]
 ω – (omega) the rotational speed (radians / sec) of the winch and drum [to be determined]
 Pr – the power (W) required to meet the torque and speed requirements [to be determined]
 M-x – the model number of the selected winch [to be selected for each lift design]
20
20
40
40
60
60
80
80
100
100
120
120
20
20
40
40
60
60
80
80
100
100
Percentage of maximum Torque
Percentage of maximum Torque
Percentage of maximum rotational speed
Percentage of maximum rotational speed
ENG1002 Design Project – S2 2019 – V2 6
Technical Analysis required for Section 2
The technical analysis of this section should determine (for each of the two lift sizes):
 the relationship between the time of travel t and the velocity of the lift v
 the relationship between the force required F and the maximum lift mass Mgross
 the relationship between the torque required T and the force required F
 the relationship between the required velocity of the lift v and the torque required T
 the relationship between the required the rotational speed of the winch ω and velocity of the lift v
 the power required Pr to operate the winch
 the models of winch M-x that meet the design requirements
Note – other quantities may need to be included when formulating some of the above relationships.
Design Section 3 – Battery selection
The energy required to raise the lift will be dependent on its mass and the lift height. The electrical energy consumed by the winch to do this work is provided by the battery through the controller. Losses of energy occur in the lift controller and in the winch and drum mechanism. These losses are accounted for within the stated efficiencies of these devices. The energy efficiency of the lift controller is 90%. The energy efficiency of the winch and drum mechanism is 50%. (This efficiency factor allows for the losses in the motor, gearing and friction in the mechanism)
In this ‘solar powered lift design‘– the battery serves three purposes:
 to provide a constant voltage to the lift controller independent of the instantaneous intensity of the solar insolation (sunlight) falling on the solar panels, and
 to deliver bursts of energy to the lift controller when needed, which may be greater than the solar panels could directly deliver, and
 to store the electrical energy the lift controller needs to run the lift for several days in poor weather conditions.
(How the first two dot points are achieved is beyond the scope of this design)
For this design the battery must store enough energy for 3 days of operation during poor weather. This period is the maximum period during which the solar panels will be unable to charge the battery. Assume that the battery is kept fully charged on sunny days.
For the two lift sizes the minimum number of trips the lift must be able to complete per day is: 20 trips for the domestic lift and 200 trips for the commercial lift. In Section 2 it was stated –
Only upward motion is to be considered in determining the power and energy requirements for the operation of the lift. For the purposes of this design a ‘trip’ will always be considered as one upward and downward movement of the lift over two floors (6 m).
A further requirement is that the battery is NOT to be fully discharged during these poor weather events. Fully discharging the battery significantly reduces its cycle life. (The number of times it can be charged and discharged.) How much a battery is discharged is called its ‘depth of discharge’, stated as a percentage of the battery’s capacity. Eg. 25%. Limiting the depth of discharge improves the life of the battery, but it essentially reduces its storage capacity TO that percentage.
Two battery types are to be considered for this design: a Flooded Lead Acid (FLA) battery and a Lithium Ion (LI) battery. The acceptable depth of discharge for a FLA battery is 50% and for a LI battery is 25%. The cycle life of a FLA battery is typically 600 cycles and for a LI battery is 2500 cycles. The cost of a FLA is $100/kWh and the cost of a LI battery is $500/kWh.
ENG1002 Design Project – S2 2019 – V2 7
The battery and its energy requirement are defined by the parameters:
 N – the minimum number of trips the lift is required to make [constant for each lift size]
 D – the minimum number of days of storage (3) [constant]
 Ew – the energy required to be delivered (kWh) by the winch [to be determined for each lift design]
 ηw – the efficiency of the winch and drum mechanism (50%) [constant]
 ηw – the efficiency of the lift controller (90%) [constant]
 Eb – the energy required to be delivered (kWh) by the battery [to be determined for each lift design]
 B – the battery type [to be selected for each lift design]
 DoD – the depth of discharge [constant for a battery type]
 Sc – the rated energy storage capacity of the battery (kWh) [to be determined for each lift design]
 Cb – the cost of the required battery [to be selected for each lift design]
Technical Analysis required for Section 3
The technical analysis of this section should determine (for each of the two lift sizes):
 the relationship between energy Ew required to be delivered by the winch and the number of trips N, number of days D and mass of the lift Mgross
 the relationship between the energy required to be delivered by the battery Eb and the energy required to be delivered by the winch Ew
 the relationship between energy storage capacity of the battery Sc, depth of discharge DoD, selected battery type B and the energy required to be delivered by the battery Eb
 the cost of the required battery Cb
Note – other quantities may need to be included when formulating some of the above relationships.
ENG1002 Design Project – S2 2019 – V2 8
Design Section 4 – Solar Panel sizing
The energy used to charge the battery is provided by an array of solar panels through a battery charger. Losses of energy occur in the battery charger and in the battery itself during charging. These losses are accounted for within the stated efficiencies of these devices. The energy efficiency of the battery charger is 98%. The energy efficiency of the Flooded Lead Acid battery is 80% and for the Lithium battery is 95%. (This battery efficiency allows for both charge and discharge losses.)
In section 3 the battery capacity Sc had to be specified such that it could store enough energy for 3 days of operation during poor weather. (ie. While the solar panels were unable to charge the battery.) Once that period of poor weather is over, the solar panels need to be able to recharge the battery AND provide the energy the lift normally needs to operate. To ensure the solar panels can achieve this – the energy able to be generated by the solar panels each day is to be twice that required to operate the lift. This is termed the recharge factor RF = 2.
Note that the energy required to operate the lift each day (20 trips domestic and 200 trips commercial) is NOT the same as the storage capacity of the battery.
The level of solar insolation (sunlight) falling on the array of panels will vary across the day and seasons, however it is to be assumed that the array can (on average) produce electrical energy at a rate equal to its total rated output power Ps for 6 hours each day.
The array of panels is to be made up of a number (Ns) of panels each rated output power of Ppp = 280 W.
The solar panels and battery charger are defined by the parameters:
 ηb – the efficiency of the battery (SLA 80% and LI 95%) [constants]
 ηbc – the efficiency of the battery charger (98%) [constant]
 hg – the hours of generation (6 hr) by the panels at its rated output [constant]
 RF – the recharge factor (2) [constant]
 Ps – the total output power rating of the solar panel array [to be determined for each lift design]
 Ppp – the output power per panel (280 W) [constant]
 Ns – the number of solar panels required in the array [to be determined for each lift design]
 Cpp – the cost per solar panel ($350 each) [constant]
Technical Analysis required for Section 4
The technical analysis of this section should determine (for each of the two lift sizes):
 the relationship between the energy required to be delivered by the solar panel array Es and the energy required to be delivered by the battery Eb
 the relationship between the energy to be delivered by the solar panel array Es , the 6 hours generation and the power output rating Ps of the solar panel array, taking into account the recharge factor RF
 the number of panels Ns required to form the array to deliver the power output rating Ps, (for the two battery types)
 the cost of solar panel array Cp (for the two battery types)
Note – other quantities may need to be included when formulating some of the above relationships.
ENG1002 Design Project – S2 2019 – V2 9
Design Section 5 – the cost of equipment
The total cost of the components included in the design are to be estimated from the design analysis, for both the domestic lift design and for the commercial lift design. This total cost Ctot includes costs of –
 Clift – materials that comprise the lift (stainless steel RHS and plate plus the tempered glass)
 Cw – the winch
 Cb – the battery required for each battery type
 Cbr – cost of battery replacement (as required) across the design life of the equipment
 Cp – the solar panel array
The design life of the equipment is specified as 12 years. The life of the Flooded Lead Acid battery is specified as 3 years. The life of the Lithium battery is specified as 12 years.
The costs of materials are:
 $40 / linear metre of stainless steel RHS
 $20 / m2 of stainless steel plate
 $40 / m2 of tempered glass
 $100 / kWh capacity for FLA battery
 $500 / kWh capacity for Lithium battery
 $350 / solar panel (280 W)
Table 2. Winch costs
Winch Model
Cost ($)
M-1
2000
M-2
2500
M-3
3500
M-4
4000
M-5
4500
M-6
5000
ENG1002 Design Project – S2 2019 – V2 10
3. Design Specifications
3.1 Design Goals
The design goals for the project are to:
G1. minimise the capital cost of equipment.
G2. maximise the rate at which people can be transferred between floors without exceeding the budget.
3.2 Design Requirements
The following requirements must be met:
R1. Provide the following minimum capacities for the relevant lift size:
Domestic: at least 4 passengers, or 1 wheel chair plus occupant Commercial: at least 8 passengers, or 2 wheel chairs plus occupants plus 4 passengers
R2. A Design Factor of DF = 5 is to be used when determining the force the winch is able to deliver.
R3. The lift must be able to operate on energy stored in the battery for at least 3 days during bad weather.
R4. The lift must be able to provide the following number of trips in a day
Domestic: 20 trips Commercial: 200 trips
R5. A recharge factor of RF = 2 is to be used when determining the output rating of the solar array.
3.3 Design Constraints
The following constraints apply:
C1. The maximum budget for the two lift designs are:
Domestic: $ 8,000
Commercial: $ 50,000
C2. The space allocated for a wheel chair must be a square of 0.9 m x 0.9 m.
C3. The width of the lift door must be no less than 0.9 m wide.
C4. The acceptable depth of discharge for a FLA battery is 50% and for a LI battery is 25%.
C5. The life of a FLA battery is 3 years, the life of a Lithium battery is 12 years
C6. The expected design life of the equipment is 12 years.
C7. Only winches specified in Table 1 and are to be used in preparing a domestic lift design or a small commercial lift design.
3.4 Simplifying Assumptions
The following simplifying assumptions are to be made:
A1. Negligible electrical power is required to lower the lift and the effects of braking are to be ignored.
A2. Costs of the components not specifically provided in versions of the Client Brief are to be ignored.
3.5 Scope
The technical analysis and design work required for this project requires the specification of values for the parameters listed for each design section and the selection of components only from those provided in this Client Brief. All components or materials not specified in versions of this brief are outside the scope of the design and should not be considered.
ENG1002 Design Project – S2 2019 – V2 11
Important notes to students
The sections listed above are to be used to subdivide the analysis and design process and identify the sections you are to use for your Technical Analysis & Presentation and Design Proposal assignments.
IMPORTANT: This is a closed design problem where all information required to complete the technical analysis, calculations and evaluation of possible solutions will be available in the Client Brief, your text books or other provided assignment material. The problem presented is a simplified version of a real design problem, so the more complex aspects and fine details of the components of the proposed system are ignored.
If you find yourself seeking information beyond that provided in the Client Brief, your text books or other assignment material then you are probably over thinking the problem. The three assessments using this problem are able to be completed using just the engineering fundamentals you are studying, supported by other course material and tools like the spreadsheet. There is no need to research commercial equipment.
For the technical analysis report (in the TAP assignment) all students must complete a technical analysis and prepare a short technical report on design section 1 (only) of the project.
For the presentation (in the TAP assignment) all students must complete a technical analysis and prepare a short oral presentation on design section 2 OR 3 (only) of the project. Present a summarised technical analysis of that section of the design and how it links to section 1 of the design. The presentation is to be prepared and delivered as if it was to be delivered to colleagues in your company who are working with you on the larger project.
For the Design Proposal assessment students are expected to complete the technical analysis for the whole project, model the design on a spreadsheet, evaluate some alternatives within the design and select a specific design solution to recommend in their report. The recommendation must clearly specify all of the parameters listed in the design sections in bold, as they define each section of the design.
Students should note there is more than one correct answer to this problem, as several possible solutions will meet the requirements of the design. You are NOT expected to find an optimum solution, but simply to identify where the better solutions are across the possible solution space (defined by a range of parameters) and recommend one solution.
Furthermore – a technical analysis of a single design section ALONE is unlikely to identify a set of design parameters that results in a workable final design, as the sections are somewhat dependent on each other. Hence when you complete a technical analysis on a single section of the design you are not looking for a specific single ‘answer’, but identifying the range of parameters that meet the requirements of that section.
The staged release of a Version 1 and a Version 2 of the Client Brief is intended to discourage students from trying to ‘solve’ the whole problem at once, because some students try to present a single ‘best case’ as the outcome of an analysis of a single section.
Your analysis should show the relationships between the parameters within each section and possibly with those in other sections of the design. This analysis will allow you to eliminate some of the alternative equipment suggested (when it is evident it cannot do the job), or you may be able to reduce the range of values for some parameters which offer a possible solution.
ENG1002 Design Project – S2 2019 – V2 12
Company Profiles and addresses
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Domineering – family surnames beginning with P – S
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Exemplar Designs 55 Technic Way Newstead QLD Australia 4006