Fixed-Pitch Straight-Bladed Vertical Axis Wind Turbine: … · · 2010-03-13Turbine: Design Challenges and Prospective Applications . 1)Introduction ... weight pultruded Fibre Reinforced

Mazharul Islam, PhD

Fixed-Pitch Straight-Bladed

Vertical Axis Wind Turbine: Design Challenges and

Prospective Applications

1)Introduction

2)Design Challenges

3)Prospective Applications

4)Potential Research Areas

5)Concluding Remarks

At present, wind energy is the fastest growing Renewable Energy Technology;

Currently there are two main categories of modern wind turbines, namely Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT);

This presentation attempts to highlight design aspects and prospective applications of smaller-capacity (<10kw) fixed-pitch straight-bladed VAWT (SB-VAWT) only.

Comparisons between VAWT and HAWT

HAWT

Sensitive to wind direction

Complex Blade Design

More Noisy

Matured Technology

VAWT

Insensitive to wind direction

Simple Blade Design

Less Noisy

Needs More R&D

1. Introduction …

Smaller-Capacity Fixed-Pitch SB-VAWTs

Simplest Wind Turbine;

Insensitive of incoming wind direction;

Absence of yaw mechanisms like HAWTs;

The elimination of variable pitch mechanism makes simple both its manufacturing and maintenance;

However, the aerodynamic factors related to SB-VAWT are quite complex.

They generate low starting torque;

1. Introduction …

The overall cost of the SB-VAWT will mainly depend on different salient design parameters.

There are multiple design parameters which should be critically analyzed and optimized for a successful design.

Some of the critical parameters are type of blade support, solidity, blade material and blade airfoil and supporting struts shape

Design Parameters

(i) Blade Shape; (ii) Number of Blades; (iii) Supporting Struts type and shape; (iv) Central Column; (v) Swept Area; (vi) Solidity; (vii) Aspect Ratio; (viii) Chord/Radius Ratio; (ix) Rated Power Output; (x) Rated Wind Speed; (xi) Cut-in Speed;

(xii) Cut-out Speed; (xiii) Power Coefficient; (xiv) Tip Speed Ratio; (xv) Rotational Speed; (xvi) Pitching of Blade; (xvii) Tower; (xviii) Braking

Mechanism; (xix) Load; (xx) Material; (xxi) Noise; and (xxii) Aesthetic.

2. Design Challenges …

MI-VAWT 3000: A New Class of SB-VAWT

Power Output: 3 kW

Blade Airfoil: MI-VAWT1

Supporting Strut Airfoil: MI-STRUT1.

Blade Material: light-weight pultruded Fibre Reinforced Plastic (FRP)

Configuration: Overhang type with endplates.

Solidity: 0.5

Aspect Ratio: 13.6

2. Design Challenges …

Straight-bladed VAWT is a candidate for urban and remote applications if a successful commercial model can be fabricated.

From the past experiences, it is evident that wind turbines can compete with conventional sources in niche markets.

Cost-effective smaller capacity SB-VAWT can be utilized for an array of applications to provide mechanical, electrical and heat energy.

Electrification of Remote Communities

Remote off-grid communities can be found in most of the countries in the world which are ideal consumers of sustainable energy sources such as wind.

At present, expensive diesel or propane driven gensets are used for supplying electricity and heat in these locations.

In these remote areas, generating electricity with diesel generators can range from $0.25 to $1.00 per kilowatt hour [CANRen 2006].

SB-VAWTs can be used in these locations for electricity generation.

3. Prospective Applications …

Source: Cleanfield, Canada

[Source: Islam et. Al. 2007. Assessment of Small-Capacity Straight-bladed VAWT for Sustainable Development of Canada. International Journal of Environment Studies. Vol 64, No 4, pp 489–500..]

Figure : Schematic of a Typical SB-VAWT Stand-alone Electric System [Islam et. al. 2007. Assessment of Small- Capacity Straight-bladed VAWT for Sustainable Development of Canada. International Journal of Environment Studies. Vol 64, No 4, pp 489–500..]

Electrification of Urban Cities

In the future, most of the people in the world will live in urban areas [Research Group on the Global Future 2006].

Due to this process, increasing amount of cleaner energy technologies, like wind energy, are required for the urban population for sustainable human development.

Smaller capacity SB-VAWT has a clear niche market in the urban areas due to their low levels of noise and the independence from the wind direction [Hannes 2003].


Ropatec, Italy


Figure : Schematic of a Typical SB-VAWT Grid-connect Electric System [Islam et. al. 2007. Assessment of Small- Capacity Straight-bladed VAWT for Sustainable Development of Canada. International Journal of Environment Studies. Vol 64, No 4, pp 489–500..]

Pumping Water

A smaller capacity SB-VAWT can be utilized to drive a rotating or reciprocating pump.

It has a particular advantage of locating the pump at the ground level which can be directly coupled with the rotating shaft of SB-VAWT and thus might be able to eliminate the need for a gearbox or belt-drive.

Furthermore, these turbines can be used to drive a pump indirectly where the turbine generator can provide electricity for a remotely located electricity-driven pump.



Figure : Schematic of a Typical SB-VAWT Mechanical Pumping System [Islam et. al. 2007. Assessment of Small- Capacity Straight-bladed VAWT for Sustainable Development of Canada. International Journal of Environment Studies. Vol 64, No 4, pp 489–500..]

Remote Telecommunication

Supplying an isolated telecommunication station exclusively with a diesel or propane driven genset is very expensive due to very high transportation costs of fuel and recurrent maintenance problems.

It has been found with tests of horizontal axis wind turbines that not all these equipment could fulfill the expectations with regard to low maintenance and resilience in extreme conditions [Hannes 2003].


SAWT, China

Operating Street Lamps

Street lamps are quite commonly used in urban and rural areas.

SB-VAWT can be installed above the towers to power the street lamps through battery banks.

SAWT, China


Ventilation

Smaller capacity SB-VAWT can also been applied for ventilation purpose.

Ove Arup, an Australia-based company, has developed a wind turbine able to rival electricity as a power source for ventilation.

The cost of installing their SB-VAWT is similar to that for conventional ventilation.

But they have found it less noisy and in some conditions, a building can cool and ventilate itself [Ove Arup & Partners 2003].


Vawtex, Australia [Ove Arup]

Vawtex, Australia [Ove Arup]

Heating Water by Fluid Turbulence

During the winter months, it is possible to use wind energy directly for heating purposes.

In this application, instead of arrangement of generator and gearbox, the wind turbine contains a brake that directly warms up water in an insulated tank by whirling [Grauthoff 1991].

The thermal inertia of the system being heated provides energy storage. This system can offer good torque-speed matching and efficient energy conversion [Kirke 1998].

Several heating systems are already in use in Japan for converting wind power for heating greenhouses [Nagai et. al 1986].


Refrigeration

It is also possible to couple a wind turbine directly with the compressor of a refrigeration unit.

From a feasibility study funded by the European Union, it appeared that the application of wind energy driven cooling systems can be economically justified, especially when used as an autonomous system in remote areas [Foellings et. al 1985].

This type of system has prospect for community cold storages in remote islands and coastal areas.


Mechanical Aeration for Ponds, Lakes & Wastewater Treatment Plants

Aeration improves water quality by maintaining good dissolved oxygen levels throughout all of the water, including the bottom.

This is very important because once the lake or pond has oxygen near the bottom, new insect larvae, snails, and other fish food can begin to live there.

So, vertical axis type surface aerators can directly be coupled with smaller capacity SB-VAWT for the above-mentioned low intensity aeration applications, requiring no gearing or right-angle drives [Kirke 1995].


Desalination and Water Purification

The traditional desalination method requires heat and/or reduced pressure.

In most situations electrodialysis or reverse osmosis is the most economical desalination system [Smith and Swinton 1988, Fell 1985].

Electrodialysis requires electrical current but reverse osmosis requires only a pressure difference, which is provided by pumping.

SB-VAWTs can provide energy for each of these methods of desalination and decontamination, but wind-powered reverse osmosis in particular appears to merit further investigation [Kirke 1998].


Hydrogen Production

One of the important issues related to wind energy is its intermittent nature.

To address this issue, production of hydrogen through the electrolysis of water can be done with the help of electricity generated by SB-VAWTs.

The stored hydrogen can subsequently be used to produce electricity during time when energy production from wind turbines are not sufficient to meet the demand.

The energy in the stored hydrogen can be converted into electrical power through fuel cell technology or a combustion engine linked to an electrical generator.


Exploration of alternative materials (maybe nono-materials)

Finite Element Analysis (FEA) Analysis for Consideration of Natural Frequencies

CFD Analysis for Assessment of Turbulence Effect

Development of a MI-VAWT 3000 Prototype and eventually a commercial product.

Still there are several challenges which are hindering the wide spread application of the smaller-capacity fixed-pitch SB-VAWT.

A robust design of efficient SB-VAWT with self-starting characteristics is very importance.

It should be designed and developed in a cost-effective manner for successful deployment.

References CANRen. 2006. Natural Resources Canada. Available online at: http://www.canren.gc.ca (cited 11 September

2006).

Fell, C. 1985, Desalination Processes and Theory. Proceedings of Australian Water & Wastewater Association, Seminar on Desalination, Adelaide, Australia. June.

Foellings, F.J. and Smulders, P.T. 1985. Wind Energy and Cooling. Report of Commission of the European Communities. pp 624–628.

Grauthoff, M. 1991. Utilization of Wind Energy In Urban Areas – Chance or Utopian Dream? Energy and Buildings, Vol 15–16, pp 517–523.

Hannes, R. 2003. HAWT versus VAWT. Refocus July/August.

Islam, M., Ting, D. S-K. and Fartaj, A. 2007. Assessment of Small-Capacity Straight-bladed VAWT for Sustainable Development of Canada. International Journal of Environment Studies. Vol 64, No 4, pp 489–500.

Kirke, B.K. 1995. Wind Powered Aeration for Wastewater Treatment, Aquaculture And Lake Destratification. Wind Engineering. Vol 19, No1, pp 1–12.

Kirke, B.K. 1998. Evaluation of Self-Starting Vertical Axis Wind Turbines for Stand-Alone Applications. PhD Thesis, Griffith University, Australia.

Nagai, H., Shinoda, J. and Ushiyama, L. 1986. Agricultural Applications of Wind Power in Japan. Proceedings of European Wind Energy Association Conference (EWEC), 7–9 October, Rome, Italy. pp 463–468.

Ove Arup & Partners. 2003. Harare International School, Zimbabwe. Zimbabwe.

Research Group on the Global Future. 2006. Global statistics: urban/rural population, Center for Applied Policy Research, Munich University, Germany. URL: http://www.cap-lmu.de/fgz/statistics/urban_pop.php. (cited September 14, 2006).

Smith, B.R. and Swinton, E.A., 1988, Desalination Costs In Australia: A Survey of Operating Plants. Desalination, Vol 70, pp 3–15.

Thank You Very Much

Fixed-Pitch Straight-Bladed Vertical Axis Wind Turbine: … · · 2010-03-13Turbine: Design Challenges and Prospective Applications . 1)Introduction ... weight pultruded Fibre Reinforced

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