• Project Background and Objectives
• Design and Engineering
• Construction and Commissioning

Providing adequate and reliable electricity is vital to the sustained economic development of Hong Kong. The Hongkong Electric Company, Limited (HEC) is committed to ensuring quality power supply to its customers, while paying due care and respect for the environment.

Feasibility Study and Wind Monitoring Programme

Recognizing the importance of sustainable development and the pressing need to improve air quality in Hong Kong, HEC took an initiative in 2000 to explore the feasibility of utilizing wind as renewable energy to supplement fossil fuel for power generation in Hong Kong.

Using wind energy for power generation has been expanding very fast over the past decades as it offers a clean power source, which completely avoids the emission of carbon dioxide and other gaseous pollutants. Historic meteorological data indicate that some areas in Hong Kong have fairly good wind potential. However, there was limited information on the wind profile analysis and utilizing wind energy in commercial scale locally in Hong Kong. As such, HEC carried out a detailed feasibility study and wind monitoring programme to identify suitable sites on Lamma Island with a view to building Hong Kong’s first wind turbine for power generation.

Wind monitoring programme at Po Toi and Lamma Island was commenced in April 2001. HEC submitted a Project Profile in March 2004 to the Environmental Protection Department (EPD) for building Hong Kong’s first commercial-scale, grid-connected wind turbine on Lamma Island as a pilot project. The Environmental Impact Assessment Report was approved by the EPD in October 2004 and HEC received the Environmental Permit for construction and operation in November 2004.

Main Objectives

The main objectives of the project are to acquire knowledge in the design, construction and operation of wind turbine and promote public awareness of the benefits as well as the limitations of utilizing wind as renewable energy for power generation in the context of Hong Kong’s unique situations.

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The design of Lamma Wind Turbine follows the typical configuration comprising three rotor blades, a nacelle and a tubular tower. The nacelle houses the rotor blade shaft, gearbox, generator and electrical instrument and control components. The wind turbine uses the profile of the rotor blades to transform the lift forces generated by the wind into a rotating motion. The rotor blade shaft drives the generator via a gearbox to produce electricity. The electric power generated is transmitted to the nearby power grid via power cable.

With all technical requirements and constraints stipulated in the Tender Specification, invitation to tender for the design and supply for the Lamma wind turbine was issued in July 2004 to major wind turbine manufactures. Proposals received were critically reviewed and evaluated against compliance with international guidelines and HEC’s Specification. The contract was awarded to Nordex Energy GmbH of Germany in December 2004.

Design Features

The Lamma Wind Turbine is Nordex’s standard N50/800kW machine with a rotor diameter of 50m and a rated power of 800kW. The wind turbine is of stall-regulated, “horizontal axis” design and is mounted up-wind.

The N50 model is a compact machine of high-energy yield designed for a service life of 20 years. The rotor blades are made of high quality glass fibre reinforced plastic with a length of 23.3m. The end 3.7m blade tip is pivotable and can be swiveled 85 degrees relative to the main blade to act as aerodynamic brakes. Lightning receptors are integrated into the blade tips to divert energy from lightning strike to the hub. The rotor drives a main steel shaft which is connected to a gearbox. Rotation is speeded up after the gearbox to drive a generator for power generation. All components apart from the blades are housed inside a nacelle made of glass fibre reinforced plastic supported by steel frame.

The design of N50 machine allows operation of the wind turbine to be responsive to the prevailing wind conditions. Wind direction and wind speed are constantly monitored by two mutually independent wind sensor systems mounted on top of the nacelle. When the wind direction is different from the facing direction of the rotor blades, the nacelle can be yawed actively in a smooth manner at a speed of around 0.6º per second to maximize energy captured by the wind turbine.

The nacelle is mounted on top of a tubular steel conical tower of height 46m. Pre-fabricated ladder and working platforms are installed inside the tower for access and maintenance. The tower is fabricated in Denmark with stringent quality control to ensure it can withstand severe wind load during operation. The tower is designed according to IEC 1 standard capable to survive a maximum wind speed of 70m/s for 3 seconds. Corrosion of tower is protected by application of acrylic polyurethane top coating.

The standard design of wind turbine tower comprises top and bottom segments of 26.3m and 17.6m respectively. However, this standard design poses practical difficulty in delivering the long top tower segment to site as the turning radius of sharp bends along the narrow and winding transportation route cannot accommodate it to pass through unless substantial amount of trees and plantation along the transportation route are removed. Having considered the impact on terrestrial ecology resulted from tree cutting, the top tower was modified by splitting it into two segments: top and middle of length 11.7m and 14.6m respectively to facilitate road transportation.

The entire wind turbine weights more than 80 tonnes. Taking into consideration of the wind load and dynamic load during operation of the wind turbine, a robust foundation was required to support the entire wind turbine atop. A conical reinforced concrete footing of approximately 15m diameter and 4m depth was constructed below ground level of the site platform as foundation of the wind turbine. A total of 120 pieces of specially designed M36 anchor bolts of length more than 4m each was precisely embedded into the concrete foundation to hold the bottom flange of the lower tower segment.

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Inland Transportation

In mid-August 2005, various components of the wind turbine arrived at Lamma Power Station, a few kilometers away from the wind turbine site in Tai Ling. The equipment was transported to Tai Ling by an 80 tonne trailer maneuvering along the narrow and winding 275kV cable route adjoining Lamma Power Station and Tai Ling. Challenges faced for the delivery were mainly attributed to the weight and size of bulky equipment in which the heaviest equipment weights 29 tonnes while the longest equipment has a length close to 20m.

Full load trial running of the trailer was carried out prior to the actual equipment delivery to ascertain the feasibility of transportation. It was revealed that road surface modification was necessary to eliminate slipping of the trailer. Structural calculation was conducted to ascertain the loading of heavy equipment would not pose impact to the 275kV power cable located underneath the cable route.

Equipment Installation

Installation of wind turbine commenced in early September 2005. In view of the limited space available on site, logistic arrangement on equipment delivery schedule to site was carefully planned in such a way that sequence of delivering equipment would match with the daily installation programme. Two hydraulic lifting cranes, one of 200 tonne and the other of 45 tonne load rating were employed to carry out the equipment lifting and installation works.

Prior to tower installation, preparation works were performed, including setting of compensation plates to ensure leveling of the foundation platform supporting the bottom tower. Control cabinet housed inside the wind turbine tower was installed prior to setting the lower tower segment on the base.

Theodolit measurements were carried out to ensure the bottom tower segment was straightly aligned to avoid tilting of the wind turbine tower resulting in unsafe operation of the wind turbine. The middle and top tower segments were subsequently installed but no further alignment verifications to installations of these segments were required on site as stringent quality control of the tower manufacturing process was conducted at shop which eliminated the possibility of misalignment between these segments. All tower segments were flange connected by bolts tightened to specified torque levels using special torque wrenches.

As the tower stood 46m above ground level which would be subject to significant wind loading, it was necessary to complete the installation of the nacelle on the same day to provide adequate dead weight to counter the wind load effect and avoid the tower being subject to excessive swinging. The nacelle was successfully mounted on tower on the second day. In the absence of power supply for the permanent aviation warning light on top of the nacelle, a temporary warning light was installed during the transition period to warn any low flyers approaching the tower.

Installation of rotor blades posted a significant challenge to the project team as the lay-down area available for site assembling the rotor blade of diameter 50m was very limited. Part of the rotor blades were inevitably placed extending over the site boundary and protruding over the slope, and one of the rotor blade had to be held in position by a 45 tonne crane.

The fully assembled rotor blades had to be placed at ground level for two days awaiting suitable weather condition for lifting onto the nacelle. This was necessary because the blade assembly, once lifted up on air, was susceptible to collision onto the tower by wind current causing damage to the wind turbine equipment.

Electrical installation work was subsequently carried out including cable connection and termination between the nacelle and tower bottom, installation of ethernet switch for data transfer, powering up of aviation warning light, setting up of park and remote monitoring PCs and energization of the High Voltage Distribution Pillar. The wind turbine system was ready for power receiving on in September 2005 and entering into the testing and commissioning stage.