Looking At The Subtropical Climate In Hong Kong Construction Essay

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Hong Kong is a high-rise and high-density city with a subtropical climate. At present, Hong Kong does not as yet make significant use of renewable resources to meet its energy needs. Lack of incentives and shortage of land and space are the key factors limiting the deployment of renewable energy systems (Hui, Cheung and Will, 1997). Large hydropower, traditional biomass and geothermal energy are not feasible in Hong Kong because of the local conditions and resources. Only a few projects in Hong Kong now have extensively adopted some forms of renewable energy, such as solar water heating.

Nevertheless, with growing concerns about energy and the environment, Hong Kong has been working hard in the past decade to develop energy efficiency programmes and to find ways to minimise the environmental impact of energy production and use (ESB, 1998). There is a need in Hong Kong to establish a renewable energy market so as to satisfy the local demand for green energy and create business opportunities for promoting renewable energy in mainland China (Hui, 1997). Solar energy systems, such as solar thermal and photovoltaics, are believed to be one of the potential areas for future development. Under the Hong Kong's urban context, technologies that can be integrated into a built environment with high-rise buildings are important. Countrysides and new towns in Hong Kong are also potential candidates for renewable energy systems.

In Hong Kong, utilisation of solar energy for domestic, commercial and industrial purposes is affected by the following factors (Hong Kong Government, 1985):

High-rise buildings and high population density make it difficult to find suitable locations for solar collectors and equipment.

As the demand for heating energy is relatively low in many buildings, the economic advantage of directly using solar heat is weakened.

The requirement of strong anchorage to withstand high gales in the typhoon season adds extra costs to the solar energy installation.

In the absence of a local equipment industry, the majority of the equipment has to be imported from overseas and the price of the equipment is high compared with the potential saving.

Building developments in Hong Kong are usually fast track and demand quick returns on investment. This creates barriers to solar systems which often require much time to design and have a longer payback period.

As the energy price in Hong Kong is very low compared with the land and construction costs, the developers and building owners lack the incentive to use solar energy systems. With a small number of applications and limited market, the possible economics of scale cannot be achieved at present and the awareness and knowledge for the technology are comparatively low.

Despite of the difficulties mentioned before, the Hong Kong Government has tried to use and explore solar energy systems in their premises since 1980. The purpose is to collect performance data and build up experience from the completed installations before the economic advantage of the solar systems can be justified in a business environment. In recent years, a few large-scale projects for solar thermal systems have been completed to demonstrate the importance of such applications and to change people's general attitudes.

Solar Thermal System Application

Solar thermal systems using sunlight to heat water directly or indirectly have been installed in nine government premises with a total solar collection area of over 1,700 m2. These premises include public bathhouses, prison (for kitchen and laundry equipment), military camp, swimming pool complex, hospital, and a new slaughterhouse. The major functions of hot water produced by solar heating are for bathing, pool heating and pre-heating of boiler feed water. The estimated payback periods vary from 6 to 27 years depending on the usage of the systems. Table 3 shows a list of the large-scale solar thermal applications in Hong Kong. Most of them are government projects installed in rural areas or new towns, since it is difficult to find suitable locations in urban areas.

Experience showed that putting solar installation into a new building usually is more favourable than retrofitting an existing building because the cost of retrofitting in framing and plumbing may be much as the cost of the collectors for a small project. Sizing the pipework and circulating pump accurately can reduce the operating cost. To avoid waste of thermal energy, insulation should be designed properly. Proper operation and maintenance of the installation are critical to generating of energy and cost savings from the system.

Apart from government projects, a few private buildings in Hong Kong have tried to install solar thermal systems for generating hot water. Their considerations for economic justification are important and this is usually met by matching solar heat with sufficient hot water demand, such as in hotels and youth hostels.

To improve the efficiency of the system, other measures or technologies may be utilised to compliment the solar heat, such as the use of heat pump or heat recovery systems to reclaim heat from the air-conditioning plant so as to raise water temperature in the hot water system (see Figure 1). An integrated approach to designing of the building energy systems is important for achieving an optimal design solution which minimises total non-renewable energy use. A careful understanding of the cooling and heating demands is necessary for designing and matching the system components. This will help lower the capacity and initial investment of the systems.

Figure 1.  Solar thermal system integrated with heat pump chiller for hot water generation

Policy

The Government's commitment is critical for the development and implementation of solar energy systems in Hong Kong since there are various institutional and technical barriers in the free-market business environment that prevent the renewable energy industry from growing easily by itself. With a vision to achieve sustainable development in Hong Kong for the 21st century, the Government has carried out studies and considered ways to improve urban environment and make better use of resources (Planning Department, 1999).

Among the various agenda items, renewable energy is one of the key issues that most people agreed to pursue unanimously. The major question at this point is to investigate the most suitable renewable energy for Hong Kong and build up skills and experience for its development, design and operation. Bear in mind the social and economic conditions of Hong Kong, it is important to recognise that solutions to the energy problems are not simply a matter of applying technology and enforcement through legislation. It requires public awareness and participation as well. Therefore, measures to promote public awareness and education are crucial for the implementation of the renewable energy policy.

Conclusion

Solar energy has definite possibilities in Hong Kong since there is abundant sunlight. High-rise and high-density urban environment create difficulties to solar energy applications. Current business practices do not favour renewable energy and the Government's role is critical for stimulating the market. Although current applications (solar thermal and photovoltaics) are small in number, they can provide valuable information and draw people's attention to the technology.

Interesting suggestions for using solar systems have been raised in the community. For example, it was suggested to build solar and wind energy systems in the "Hong Kong Disneyland"; a holistic approach for designing solar systems in the new towns was proposed; highways and tunnels may be lit and ventilated by a renewable source of energy; solar-powered streetlight systems may be widely adopted. More research and innovation are needed to examine and identify suitable design options. Partnership between Hong Kong and mainland China will open up a new era for achieving sustainable energy development.

 

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