2                                            CONSIDERATION OF ALTERNATIVES

2.1                                      Background to the Project

Wind energy has been the world’s fastest growing sector of the energy industry over the past two decades.  Technological developments have made wind energy a promising renewable source of power in the near term.  The many benefits wind energy offers the world are compelling: pollution-free, technological innovation, rapid development, diversity, security of supply, etc.  Globally, this was about 40,000MW of installed capacity of wind energy at the end of 2003 and it is one of the faster growing, reliable and competitive sources of renewable energy.

As a continual commitment to promoting environmental protection and sustainable development, the Hongkong Electric Co Ltd (HEC) commenced a feasibility study in April 1999 to collect wind data on Po Toi and Lamma Island to evaluate the wind potential for utilization of wind energy on these two outlying islands.  The colleted wind data revealed that Po Toi and Lamma have similar wind potential and are both suitable for power generation.

After careful consideration of the technical, economic and environmental factors pertinent to the best choice for utilizing wind energy, HEC is proposing to install a 600-850kW wind turbine at Tai Ling of Lamma Island as a demonstration of the potential for wind utilization in generating power.  The wind turbine will be built in a grid connection scheme for supplying “green” electricity to HEC customers.  The objectives of the project are as follows:

·           Demonstration of utilizing wind energy for power generation:  The proposed wind turbine will be the first utility scale and grid-connected wind project in Hong Kong.  Based on the wind potential on Lamma, the proposed wind turbine will harvest about 700MWh of electricity per annum, helping to avoid the use of up to 240 tonnes of coal and reduce the associated emissions every year.

·           Education purpose:  Visitors’ facilities such as display boards and guided tour will be provided at the wind turbine site to explain the principle of power generation by wind and the benefits of renewable energy.  The wind turbine project will serve as educational use for promotion of green awareness among the public, in particular with students.

·           Wider application of renewable energy:  The project will provide invaluable local experience on the design, construction, operation and maintenance of wind turbines.  Future utilization of wind energy in Hong Kong can be explored based on the information collected and experience gained, keeping pace with Government's policy, and the publics expectation of the promotion of renewable energy and improvement in air quality.

2.2                                      The Future Plan

The proposed wind turbine project will be planned and implemented by HEC’s in-house staff together with consultants and contractors.  Site erection will commence in early 2005 and commissioning of the project is scheduled for early 2006.  The design life of the wind turbine is 20 years.  A project area of about 4,400 m2 is being applied through short term tenancy (STT) for an initial term of 5 years and renewal of the STT will be made subject to further evaluation of the situation at that time.

The wind turbine project will serve as a pilot project for demonstration of power generation by wind and grid-connection with renewable energy.  The performance of the wind turbine will be monitored and evaluated during the operational phase including:

·           Amount of electricity generated:  The annual electricity harvested by the wind turbine will be compared with design figures to verify the site specific performance of the wind turbine at Lamma where the terrain is complicated and air turbulences are hard to predict.

·           Quality of power:  As wind is time and season dependent and fluctuating in nature, the interaction between the wind turbine and the existing 11kV power grid will be monitored to assess the effects of connecting the electricity generated by the wind turbine to the grid.

·           Resistance to wind load:  Hong Kong is situated in a typhoon-affected zone and it is essential to ascertain that the wind turbine can be designed to withstand strong winds.

Subject to the result of evaluation on various technical, environmental and commercial aspects and data collected during operational phase of the project, HEC will evaluate the potential for wider application of wind energy in Hong Kong.  Any further plan for installation of additional wind turbine will be subject to approval by the Government.

2.3                                      Justification for Choosing the Present Site

The EIAO Study Brief issued for this Project requires the justification for choosing the present site (Clause 3.3.3) with a view to avoiding or minimising the potential environmental impacts of the Project, specifically intrusion into Country Parks and other environmentally sensitive areas.

As a demonstration project for renewable energy, the study envelope was confined to locations away from densely populated areas.  Po Toi and Lamma Islands were subsequently identified for assessment of wind potential.  Two wind monitoring stations, one on Po Toi and another on Lamma, were set up in April and November 2001 respectively to record one-year wind profile.  The wind monitoring was completed at the end of 2002 and the data were fed into computer software for analysis.

Desktop screening and site surveys were subsequently conducted after completion of wind data logging to identify potential sites for a wind turbine of suitable size on Lamma and Po Toi Island based on the criteria recommended in the guidelines for wind energy development issued by reputable international organizations of wind energy.  The site search was confined to Lamma and Po Toi where reliable wind data are available.

2.3.1                                Po Toi Island

Po Toi Island is an ecologically sensitive area which has been identified as a potential Country Park.  As there is no vehicular access on Po Toi, a properly paved access road with a minimum width of 5m and a maximum inclination of not greater than 15° has to be constructed to link up the pier and sites of favourable wind potential for construction of a 600-850kW wind turbine.  Access roads meeting the above criteria on Po Toi would have a length of approximately 1,000m and cross the hill- slopes on western part of the island (Figure 2.1).  The new access road and the associated extensive reinforcement works would inevitably change the natural landscape (mainly shrub cover hillside) and disturb the habitat of resident species.  Construction of new road in a hilly island was therefore not considered suitable due to the potential adverse environmental impacts. 

Alternatively the wind turbine equipment and construction tools will have to be transported to the wind turbine site on Po Toi by helicopters.  Considering the limited payload of local helicopter services, the maximum capacity of a wind turbine on Po Toi would be restricted to about 50 kW. 

Moreover, electricity generated on Po Toi could only be transmitted to the HEC grid through the use of submarine cables.  The shortest possible route of the proposed submarine cable extended from Hong Kong Island would have a length over 5km.  It would not be cost effective without a large capacity of output (e.g. a wind farm of less than 20MW).  Given that the marine waters between Po Toi, Hong Kong and Lamma Island are already quite congested with seabed utilities, finding an acceptable route for a cable may prove technically challenging.  Although not expected to be unacceptable, the installation of a submarine cable would introduce additional environmental impacts.

At present, electricity supply on Po Toi is by means of an independent and autonomous grid.  Currently two 50 kW diesel generators installed by EMSD are operated during the night-time and residential tee-off points are connected to the nearest lampposts to take power from the grid.  To cater for the mismatch of wind profile and demand pattern on the island, a costly hybrid control system and battery bank will be required for synchronization of the wind turbine with the existing diesel generator.  Worldwide experience in the wind-diesel power generating system is rather limited and there are very few suppliers that can offer a reliable hybrid control system.

In view of the accessibility considerations and absence of a power grid, Po Toi is considered neither technically feasible nor environmentally and economically attractive for a demonstration project with commercial scale wind turbine.  The aerial photograph of West Po Toi Island where the wind potential is sufficient for wind turbine is presented in Figure 2.1.



Figure 2.1        Aerial Photo of West Po Toi Island

2.3.2                                Lamma Island

Once the above considerations had been accounted for, site selection was focussed on Lamma Island.  The wind turbine site was then examined against engineering requirements and environmental concerns and further refined using the following site screening criteria. 

Wind Potential

Following completion of a 12-month wind power monitoring at Lamma in November 2002, a wind atlas was developed to assess the wind potential of Lamma Island.  Figure 2.1 shows the “isovent” map of equal power density in terms of energy per swept area of wind turbine blades.

Areas of wind power density over 150 W/m2, equivalent to the average wind speed of about 5.5 m/s, are considered suitable for wind energy utilization and warrant further evaluation ([1]) ([2]) ([3]).  Modern wind turbines have the cut-in wind speed of approximately 2.5 to 4 m/s and sites with annual wind speed below 5.5 m/s are in general not considered economically viable due to low electricity output of wind turbine.  Areas of high wind potential are in general found on hilltops and areas of high elevation.  Most of the potential areas are concentrated in South Lamma island.



Figure 2.2        Wind Source Map of Lamma Island

Site Access

For Lamma Island, the vehicular roads that allow passage of heavy vehicles and mobile equipment are the 275kV Cable Routes built by HEC (Figure 2.2).  Since building a new access road leading to a remote site is not recommended from environmental and economical viewpoints, potential sites on Lamma Island for the wind turbine are limited to areas along HEC’s cable routes or closed to existing berthing facilities.  South Lamma Island, which consists of Site of Special Scientific Interest (SSSI) and potential Country Park and frequent records of the Romer’s Tree Frog was therefore avoided.


Figure 2.3        Vehicle Access Road on Lamma Island

Height Restriction

The Civil Aviation Department (CAD) has imposed height restriction for all permanent structures on Lamma Island in accordance with the Hong Kong Airport Control of Obstructions Ordinance.  Most areas in North Lamma along the 275 kV Cable Routes fall between the restricted heights of 160 to 165 m above the Hong Kong Principal Datum (PD) respectively (Figure 2.3).  Taking consideration of the regulations as well as the topography of North Lamma, the design and height of the wind turbine will be restricted.  In selection of suitable sites for a wind turbine of the appropriate capacity, consideration should be given to the maximum tip height of about 68 m and 90 m for a 600kW and 1MW wind turbine respectively.


Figure 2.4        Height Restriction Map for Lamma Island

Electrical Connection

Electricity generated from the wind turbine will have to be transmitted to the load center or connected to the main power grid.  Lamma Island has presently a network of the 11 kV network allowing connection by the wind turbine via new power cables and transformer.  The distance and routing of the transmission cable connecting the potential sites to the main power grid are evaluated from technical, environmental and cost considerations.

Area and Land-use

South Lamma is of high ecological value consisting of SSSI, potential Country Park, Restricted Area and conservation area.  However, Lamma Island is not an identified/ reported important site for migratory birds.  Lands along the 275 kV Cable Routes are located on North Lamma which are well away from areas of ecological importance such as green turtles nesting site in Sham Wan, and have been zoned mainly as agricultural and green belt areas and are therefore compatible.

A working platform of about 30 m x 20 m including the 15 m x 15 m wind turbine foundation is required for erection of a 600kW class wind turbine.  Areas meeting the above requirement along the 275 kV Cable Routes were further identified taking into account the landownership, present and future land-use with reference to the latest Lamma Island Outline Zoning Plan.

2.3.3                                Preferred Sites on Lamma Island

Taking into account the above criteria, six potential sites were identified with the application of constraint mapping techniques (Figure 2.4).  The details are presented in the Site Search Report (Annex A).  The six long-listed sites are:

Site 1   -      Lamma Power Station Extension

Site 2   -      Tai Ling

Site 3   -      Yung Shue Long

Site 4   -      Tai Peng

Site 5   -      Pak Kok Tsui

Site 6   -      Lamma Quarry

All of the sites avoided ecologically sensitive areas, SSSI and the potential Country Park at South Lamma.  The six identified sites are situated away from the ecological sensitive areas and along the existing 275 kV Cable Routes which are the only vehicular roads on Lamma island. 


Figure 2.5        Long-listed Sites for Wind Turbine Installation

Having identified sites that meet the broad environmental and engineering criteria, a site-specific appraisal has been conducted to establish a short-list of feasible sites for further detailed investigation.

Qualitative approaches have been adopted to identify potential conflicts with the development of the wind turbine.  Each potential site was scrutinized more closely with engineering criteria on wind potential, geological considerations and electrical connection; and environmental criteria concerning visual, noise and ecological impacts.  Of the 6 long-listed sites within the areas of least constraints, four sites have been excluded due to principal conflicts identified (Annex A), leaving the following two sites for the final comparative assessment:

Site 2   - Tai Ling

Site 4   - Tai Peng

The two sites have been evaluated and compared according to the potential impacts likely to arise as a sequence of construction and operation of the wind turbine system.  Site 2 – Tai Ling is identified as the overall preferred site due to its distinct merits in site access, ground conditions, noise and visual impact compared with Site 4 – Tai Peng (Annex A).  The site at Tai Ling is also the more remote of the two in terms of proximity to village houses.

The preferred site at Tai Ling is a relatively level platform to the east of joint bay of HEC's existing cable route.  Taking advantage of the joint bay area as part of the works area for erection of the wind turbine, the landtake requirement can be optimized.  Moving the wind turbine site further north away from the noise sensitive receivers are not preferred due to the need for extensive excavation of the hill slope to form access road for the wind turbine, and the terrain around Tai Ling site is indicated in Figure 2.6.



Figure 2.6        The existing terrain around Tai Ling site

2.4                                      Potential Capacity for the Wind Turbine

The planned capacity of the wind turbine at Tai Ling is 600 to 850 kW depending on the model sizes available from respective suppliers.  The wind turbine capacity is selected based on the following considerations:

·           600 kW class wind turbine is of proven design with a large number of installations worldwide.

·           600 kW class wind turbine is now becoming the smallest size available from the majority of the suppliers due to the worldwide trend for large capacity machines.

·           600 kW class wind turbine is the maximum size of machine complying with the height restriction at Tai Ling Site.

The wind turbine design, construction methods and Project programme are further discussed in Section 3.


([1])      Wind Energy - The Facts, European Wind Energy Association, 2004.  http://www.ewea.org/06projects_events/proj_WEfacts.htm

([2])      Wind Force 12, European Wind Energy Association, May 2004.  http://www.ewea.org/03publications/WindForce12.htm

([3])      Assessing the World's Wind Resources, Dennis Elliott, IEEE Power Engineering Review, Vol. 22(9), Sept 2002 & NREL National Wind Technology Center Publications 2002