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The Feasibility of Wind Power for Townsville

Based on an examination of the feasibility and economic viability of wind power for the Cleveland Bay Purification Plant by Dr Harry Suehrcke.

REpower MM70 - 2 MW wind turbine

- Townsville has commercially viable wind resource

- Study based on REpower MM70 (pictured left)

- Using data collected by AIMS and processed by CSIRO

- Payback in 7.7 years

Townsville City Council
(TCC) is considering the feasibility of using wind power to generate clean electricity at its Cleveland Bay purification plant to power a reverse osmosis filtration plant. This plant, part of the proposed Carbon Neutral Water Recycling Project, would filter 60% of Townsville's wastewater for reuse in irrigation and industry. It is estimated that the filtration process would require a continuous power input of approximately 1,200 kW (1.2 MW). The opportunity exists to produce some or all of the power requirement from renewable sources. One opportunity is wind power.

With the exception of the occasional cyclone, Townsville is not noted as a particularly high wind area. A study by Notus Energy (2003) of average wind speed at the Townsville Port at 65m above ground level (the rotor hub height of a REpower MM70 wind turbine) calculated an annual average wind speed of 7.1 metres per second (m/s). This speed was extrapolated from a computer model, based on wind speed date collected from the Cleveland Bay AIMS site weather monitoring station. A similar study was undertaken for the Cleaveland Bay Purification Plant site. Here, the average annual wind speed is slightly lower at 6.9 m/s.

REpower MM70

Factors to consider in wind turbine economics:

  • Power output is proportional to annula average wind speed, the area swept by rotor blades and hub height
  • Elevated positions, such as hills, often have higher wind velocity due acceleration of wind over
  • Trees and other obstacles can reduce wind speed and/or increase turbulence
  • Power output of a wind turbine is proportional to the cube of the wind speed
  • The proximity of port infrastructure for importation of turbine components reduces transportation costs
  • Accessibility to power lines and other infrastructure (e.g. roads)
  • MM70 Link to REpower website

The power generated by a wind turbine is highly dependent on wind speed. However, not all wind power can be extracted by a turbine due to the need to maintain an airflow. For example, at a wind speed of 14m/s, a MM70 turbine converts approximately 34% of the wind energy into electrical power. The actual (electrical) power output of the MM70 turbine as a function of wind speed is shown in Figure 1.

Figure 1. REpower MM70 wind turbine power output characteristics (Notus Energy, 2003)

Figure 1 shows that power output starts when the wind speed exceeds 4 m/s and reaches its maximum generation of 2,050 kW at approximately 14 m/s. From calculations based on an average wind speed of 6.9 m/s (average wind speed calculated at Cleveland Bay purification plant), the average power output of an MM70 wind turbine is 470kW, about 23% of its maximum output.

Did you know: an average home draws about 1 kW of energy, so two 2 MW wind turbines, when running at full output could power 4,000 homes.

Power output could be increased if the turbine was located at another site with higher wind speeds. For example, an increase in wind speed of 1m/s increases the average output from 470 kW to 650 kW (or 32% of maximum output). An increase of 2 m/s increases the output to 856 kW. Turbines are often placed on elevated points, such as on smooth hills, where wind speed is greatest. Trees and other obstacles can negatively affect wind speed.

The initial consideration was to locate the wind turbines at the CBPP plant in order to direct feed the power into the system and offset the purchase of electricity from the mains grid. THis would give an economic worth of the wind energy of about 10c per kWh.

It is noted that locating the turbines at a site with higher wind speeds (around 8.9 m/s) would significantly increase the power output. However, this may then facilitate the need to sell the power to the local utility and buy it back at the treatment plant. Alternatively, it would be necessary to install a power line between the turbines and the treatment plant that would increase costs and also increase transmission loss through electrical resistance.

Using simple economic calculations involving the initial cost of the turbines, annual operating costs, and the value of the power generated, the time taken to repay the initial outlay of two wind turbines at the Cleveland Bay purification plant is 7.7 years. This would mean that, given a 20 year minimum life span of the turbine, 12.3 years of power output would be free excluding minimal maintenance.

Key Findings

  • Locating two wind turbines at the Cleveland Bay purification site would produce approximately 470kW (23% of maximum turbine output)
  • A simple economic calculation (not including interest and inflation) shows the turbines would be paid back in 7.7 years
  • Locating the turbines at a site with higher wind speeds would generate greater output, and a gain in greenhouse gas abatement

Repower MM70 - The reliable 2-megawatt power plant with 70 meter rotor diameter (.pdf 328Kb)

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