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Existing Concept - A Folding Vertical Turbine

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Existing Concept - A Folding Vertical Turbine

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5 W's

What:
A flat pack vertical wind turbine
Where:
remote or underdeveloped places, may have conditions that prevent larger scale construction.
Who:
Humanitarian Aid organisations. people living at outposts (Military and Research),remote houses or settlements. festivals. Developing nations
Why:
Currently renewable power is a permanent fixture that must be professionally constructed. Limited by weather, building situation. requires permanent maintenance.
When:
Following natural disaster. or somewhat developed developing countries

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Our existing product was an interesting concept however the prototype model had a few flaws (In order of severity):

- Very low power generation
- No way to ensure blades were taught
- Awkward guy-line assembly and structure
- Bulky disks

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Define product:
- Target Market
- Evaluate stakeholders, all parties involved in product life-cycle.
- Use cases
- Identify Requirements

Research:
- Basic turbine science, efficiency, power estimates
- Aerofoil shape, number and size.
- Look at sailboats for construction ideas/material.
- Durability

Prototyping:
- Virtual airflow modelling?
- minimizing material/cost
- Storyboard assembly on-site.

Engineering Details
- Minimize wobble, stability without foundations.
- Maximum speed limit, failsafe.

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To improve the power generation of the turbine I wanted to move away from the Savonius style rotor as it has a very-low maximum power coefficient.

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Kyle - Who are you designing for? user requirements! decide this today. where and why and who it's for when considering the scale and power requirements. assembly? again user requirement based! Maintainable? swapping parts out etc. Modular?

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Humanitarian Aid
- Cost Effective
- Usable in areas with limited infrastructure
- Temporary construction
- Small and lightweight
- Low maintenance

Outposts (Research/Military)
- High Capacity
- Durable and Reliable
- Efficient

Rural Communities (Developing Nations)
- Cost effective
- Usable in areas with limited infrastructure
- Very low maintenance
- small and lightweight
- Simple to construct

Remote Housing (First World)
- Medium power generation
- Simple to construct
- Small and lightweight
- Low maintenance

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Over 1 billion live without access to any electricity. Developing nations are left to choose between expensive, unreliable clean energy and cheaper fossil fuel alternatives.
Electrical grid is incredibly expensive to build and maintain, particularly over Africa. Many people without electricity live in areas with difficult building conditions.

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Sustainable energy for developing countries

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Sustainable energy for developing countries

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Dilip Ahuja et al
https://journals.openedition.org/sapiens/823

'Overall, at least one quarter of the world’s 6.6 billion people are unable to take advantage of the basic amenities and opportunities made possible by modern forms of energy. The inequities in per capita use of electricity are even greater than the inequities in per capita use of primary energy. In 2005, the average citizen in the OECD countries used 8,365 kwh of electricity. In contrast, the average citizen in China used 1,802 kwh and the per capita average for the rest of Asia was 646 kwh. The per capita average use of electricity in 2005 in Latin America and Africa were 1,695 kwh and 563 kwh respectively.'

These regionally or nationally aggregated figures mask even starker within-country disparities, since the energy consumption patterns of elites in many developing countries are similar to those of the general population in developed countries. In fact, although it has been estimated that developing countries were spending as much as $40 to $60 billion annually on electricity systems by the end of the 20th century (G8, RETF, 2001), approximately 40 percent of the population in these countries remained without access to electricity. This means that the number of people throughout the world who had no access to electricity has hardly changed in absolute terms since 1970 (UNDP, 2000, p. 374). Not surprisingly, the rural poor in developing countries account for the vast majority (nearly 90 percent) of households that have no access to electricity.

To pay for even basic services, however, households need income-generating opportunities. These also require energy. Table 1 below shows typical electric service requirements for off-grid households in developing countries, assuming an average household size of five persons. It has been estimated that basic household services, along with commercial and community activities (e.g., rural clinics and schools), can be provided for an average of just 50 kilowatt-hours (kWh) per person annually. (Note that this figure includes only basic electricity needs. The energy requirements of cooking and transportation are not included).

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Studying Sailboat manufacture and existing vertical turbines to get an idea of current power generation and potential areas for innovation

https://www.youtube.com/watch?v=FYvvKvteWWM

https://neuhaeuser.com/windtec_en/

https://www.quietrevolution.com/

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These ideas explored if an air foil vertical turbine could be folded or and packed flat to allow for easy setup and transport

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Following the research into the turbine variations it appeared that a vertical turbine still remained the superior option as due the small scale of the product it would likely be near people and in turbulent conditions, making a quieter, omni-directional turbine ideal.

Though the savonius style turbine is cheap the largest issue with our prototype was low power generation.

From my research a helical shape represented the best option for creating a durable, quiet and efficient turbine. However it was also the most complex. This could be minimized using blades that were manufactured straight and naturally twisted when the turbine unfolded. The folding also solved the issue of vertical turbines having no way to de-power in a storm

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General rule of thumb; Turbine must be mounted 30ft (9m) in the air to avoid turbulence and increase available wind energy [1]

he capacity-weighted average cost of small wind projects installed in 2019 was $8,300/kilowatt[2]. Though this increases substantially based on construction site suitability and other factors.

Turbine power calculation:

Power = Cp 1/2 ρ A V³

P = Power output, watts

Cp = Maximum power coefficient, ranging from 0.25 to 0.45, dimension less (theoretical maximum = 0.59)

ρ = Air density, kg/m³

A = Rotor swept area, m² or

π D² / 4 (D is the rotor diameter in m, π = 3.1416)

V = Wind speed, m/s

As turbine power is proportional to wind speed cubed it is crucial to get as high a wind speed as possible.

Due the constant charging and discharging batteries must be rated to maintain efficiency well. Often called deep cycle batteries - can keep 80% of efficiency even after 1000's of discharge cycles [3]

[1] American Planning Association. (2011). Planning for Wind Energy

[2]Pacific Northwest National Laboratory. 2019 Distributed Wind Data Summary

[3]U.S. Department of Energy. Balance-of-System Equipment Required for Renewable Energy Systems

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A set of design requirements based on research findings for the final product to acheive.

1Kw power generation
- Can power ~10 Developing households
- ~2m diameter

10m Height
-  To avoid turbulence

Construct in less that an hour
- no specialist tools or electricity
- Depower for storms

Compact to transport
- all parts fit in van or can be carried by 2 people

Lightweight and cost effective

Simple to manufacture
- avoid complex aerofoil manufacture

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Designs for flat-pack/easy to set up mounting poles to get the turbine to the highest elevation possible

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The communities in developing nations could likely mount the turbine high if necessary, cheaper than building a portable tower.

Plan:
Focus on making turbine easy to DIY mount using limited equipment

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This first design was created to test if the twist and compress blades were possible.

The design was created using 3D printed part that went through 3 iterations before reaching the desired functionality. The 'blades' were made using a short section of printer filament. Each blade was angled at 40 degrees to the arm tangent to bend the  blade into a curved shape.

The model did not need a central shaft or any external force to twist correctly, showing that if the airfoil connectors were designed correctly it would create helical turbine that naturally bent into shape.

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An unintended discovery was that if compressed completely the shape would fold flat and when wire tension was released, would once again pop-up into the turbine position. I decided to explore this eliminating the central shaft

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Very simple sketches to work out the basic form of the turbine and if it would be be stable using only cables and bending tension

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Previously I calculated that the turbine would need to have the same area as a 2m horizontal turbine to generate the 1kW required. I made some basic dimensions to ensure the first design would roughly meet this.

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The initial version of the turbine using aluminium piping to form the main structure.

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The 3 are pulled in using a central winch, causing the turbine to collapse into it's folded position

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The holder has holes for swivel connectors to be mounted. The airfoil beams are then be pushed onto these connectors allowing them to rotate freely along the correct axis.

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The orignal plan involved using 4 tent poles to form a rough airfoil shape, however the taught plastic would create a relatively useless diamond shape. This updated model used 2 poles to reduce complexity/cost and utilised plastic ribs, similar to lightweight planes and gliders to create a smoother airfoil shape.

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based on the previous prototype folding flat and popping back up with relative ease, the full design mimics this process. It does however require very strong tent poles to prevent the top part of the turbine from moving laterally. More research will need to be done to work out if it is possible

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Consider if product is viable for market

Stability and durability should be investigated

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As I consider more and more parts of this design it is becoming a more complex structure that will be a difficult to price correctly for developing nations. The plan for one turbine to be power multiple households also makes it difficult to sell as a single product. future iterations will require significant value engineering

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Turbine was designed to be easily purchased and brought to setup location however this idea of selling a turbine as a product, rather than an installed structure may be better suited to other markets. developing communities would have no problem creating a permanent  installation provided the parts were easy to transport.

Market towards temporary dwellings? places that are not in constant use or may move.

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The material to be used for the airfoil is critical. To narrow the selection I am only considering materials used for sailcloth or tents as they have the required flexibility and weather resistance.

The most important categories to analyse are UV resistance, resistance to stretching and price.

At the moment I am unsure what forces the material will be under. both the wind forces and the tensile force of making the fabric taught will need to be considered, I expect it to be much less than that experienced by a sail. Nylon is low-cost and has good UV resistance so will be the current selection however may need to be updated if it will stretch or flex too much.

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Kenya and other emerging nations sell personal solar panels for their citizens to purchase, allowing them basic power use. One of these brands, Sollatek sell a 130W panel for 8864 KES (£60). A price of ~£0.5/W. Current turbine is designed for up to 1Kw however when taking into account wind factor to calculate average power over a year, the value is closer to 300W. To be viable this turbine would need to cost less than £200 which is not possible with the current design.

https://sollatek.co.ke/shop/solar-systems/solar-panels/solar-panel-14w-120w/

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Aluminium (variant undecided) will be used for the pipes and connectors that form the frame of the turbine. The 'tent-poles' will be made of fibreglass to reduce cost. Remaining plastic pieces will be injection moulded from a suitable plastic

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Using flexible beams from pop-up laundry baskets and some 3D printed ribs I created a simple prototype of the airfoil structure.

I expected the beams from the laundry baskets to be cylindrical however they were instead flat lengths, To help remedy this I combine 3 together so they had a roughly square cross-section

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Initial sketch for a larger prototype that would uses a broom stick as a central shaft

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Adding the necessary angle to main piece.

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Adapter piece to hold the air foil beams

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Adapter piece to hold the air foil beams

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3D printing is unique as it allows large overhangs, provided that the angle is not too sharp. These parts have teardrop shaped holes to ensure to minimise the overhang hole.

3d printed parts are also weakest along the layer lines. These have been designed so that the layer lines will be perpendicular to the highest forces.

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The posts to support the air foil adapter will be attached using screws to improve strength

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Doesn't work, air foil flat and not at correct tangent. Need development

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Though unlikely to work entirely changing how the airfoil adapter turns may give more understanding of the twisting mechanic

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Prototype was slightly more functional in terms of shape however 3D arms we're too fragile for many tests/pictures

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one example of some very rough sketches to try work out if 2 parallel poles would be possible. do they be equal length/need to change length?

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Design works with 2 beams of identical length, previous issue was the 2 beams rotating along the same path tangent. Because of this they were not angled away from the shaft in the correct direction.

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new design in which the turbine can be mounted like a parasol and then pushed down to secure and expand

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Turbine will be slightly smaller, with 150cm long blades.  105cm diameter means 45cm of compression to create a circle with maximum cross sectional area

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Using lightweight tent-poles to also make a base for the turbine could be effective if it was marketed towards campsite use.

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As the shaft now moves vertically a regular motor/generator would get in the way. Motors with a hollow bore are available though are less common and significantly limit shaft diameter.

https://www.pumpsandpressure.co.uk/240v-electric-motor---30-hp---1450-rpm-9000190-3028-p.asp

https://www.applied-motion.com/products/series/hollow-shaft-step-motors#:~:text=A%20hollow%20shaft%20step%20motor%20has%20a%20machined%20hole%20running,the%20shaft%20would%20normally%20be.

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This product would likely not sell enough units to make a custom/more expensive hollow bore motor worthwhile so I designed a different method using an offset motor and pulley. a bearing at the top and bottom of the mounting shaft provide stability and the lower bearing features a extra keyway to lock the shaft in place.

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This low-cost motor is a permanent magnet variety, making it more efficient than other types

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We support the following payment methods.Click for more information if you are confused about how to pay.

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DC 24V 350W 2700RPM Permanent Magnet Electric Motor Generator for Wind Turbine

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We support the following payment methods.Click for more information if you are confused about how to pay. * We currently offer COD payments for Saudi Arabia, United Arab Emirates, Kuwait, Oman, Bahrain, Qatar, Thailand, Singapore, Malaysia, Philippines, Indonesia, Viet Nam, India. We will send a confirmation code to your mobile phone to verify that your contact details are correct.

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3D model

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The pulley system adds additional complexity so I simplified the design having the motor directly below the shaft such that it is only connected when the turbine is in the expanded position

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Simplified motor mount with bearing for stability. Motor would be placed at the bottom with ribs for support. 2 Identical halves

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Outer tube and top bearing

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Designing a piece to hold the air foil beams while still allowing rotation.

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Largely base on working prototype V3

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Cylinder allows rotation and tent poles are pushed on to square peg

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Sandwiched between Side B and support piece so has 3 through holes for alignment pegs/screws.

Channels for pins to be inserted.

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Similar design however with open channels so the pins can connect to air foil

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Ribs to provide more strength

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Parts stack together with 3 screw holes for assembly

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All parts so far are designed for injection moulding, featuring no overhangs, walls that are 3mm or above and ribs/gussets for extra support. The part selected for the engineering drawing will also have the following requirements considered:

Rounding sharp corners
Draft angles
Support for bosses
Crush ribs on press-fit joints

Injection moulding was selected as it is common and in general has the cheapest per part cost for complex plastic shapes.

https://3space.com/blog/injection-mold-design/

https://3space.com/blog/injection-molding-crush-ribs/

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Research into bearings and tolerance

http://mmto.org/~dclark/Reports/Encoder%20Upgrade/fittolerences%20%5BRead-Only%5D.pdf

https://www.skf.com/uk/products/rolling-bearings/principles-of-rolling-bearing-selection/bearing-selection-process/bearing-interfaces/tolerances-and-resultant-fits

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Part will have B-3 SPI mould rating to give a semi-gloss finish, requiring a surface roughness of 0.28 - 0.32 micrometres. This was selected as it requires minimal additional mould cost with parts still smooth enough to slide with low friction.

https://www.3dhubs.com/knowledge-base/injection-molding-spi-surface-finishes/

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Using CES Granta I limited the selection to plastics that met these categories:

-Extrusion moulding capability
-Good UV resistance
-Excellent Water Resistance (Salt and Fresh)
-Recyclable
-acceptable environmental costs

This revealed POM homopolymer as a low cost yet strong plastic to be used. Further research indicates it also has a low coefficient of friction which also well suited to other components with sliding parts.

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Angled keyway to allow for twist motion.

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Using McMaster-Carr catalogue to select appropriate screws

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Using McMaster-Carr catalogue to select appropriate screws

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M3x0.5 91290A572 15mm
£10 per 50
6 required

M3x0.5 91290A171 30mm
£7.17 per 10
4 required

M2x0.4 91280A131 10mm
£7.85 per 25
3 required

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Work out how products will be manufactured

Create a bill of materials with pricing

General Arrangement drawing is difficult to understand

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As the product market is relatively niche the initial batch will be 5000 units in order to take advantage of low volume mould manufacturing.

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Estimating cost of injection moulding using online calculator

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Estimating cost of part machining using online calculator

http://www.custompartnet.com/estimate/machining/

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Though the angled keyway is necessary it is a difficult piece to manufacture. Due to the length of the part it is not possible to mount the part vertically and use a traditional CNC mill. In future Iteration I would look into ways to simplify this part.

https://www.manandmachine.co.uk/fusion-360-cam-cutting-axial-grooves-on-a-turned-part/

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https://prototechasia.com/en/how-much-does-cnc-machining-cost

A 4 axis CNC could create the necessary groove however they are more specialist machines. costing 2 - 3x as much per hour. The previous price estimation for processing cost will be multiplied by 2.5.

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The air foil bracket assembly will be costed according to manual handling guidelines. This will then be multiplied by 4 to account for the other assemblies. Very rough estimate however I learned a lot about designing for assembly. The process for attaching the air foil sleeve to the ribs is not defined or standardised so 5 minutes will be used as a rough estimation.

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A quote received from Protolabs for the motor shell shows a price close to that which was calculated. It has a slightly higher part price and slightly lower tooling cost. Both likely due to the fact the quantity ordered was lower than that in the BOM