Hong Kong is a high-rise and high-density city with a subtropical climate. In mid-1999, it has a population of 6.84 millions and an area of only 1,097 square kilometres. It does not have any indigenous fossil resources and depends entirely on imported fuels, including coal, natural gas and oil, for energy generation.

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.
 

2. Solar and Weather Conditions

The solar and weather data provide an important background for assessing the solar potential and the characteristics of energy use in buildings. Table 1 shows the solar conditions in Hong Kong (HKO, 1999). The annual mean daily global solar radiation is 14.46 MJ/m². Compared with a figure of around 9 MJ/m² in London, this is not bad at all. If we look at the cloud amount and percentage of sunshine, the data indicates that cloudiness in some months may affect directional solar radiation. Diffuse component of the solar radiation becomes significant, especially in months from February to June.

Table 1. Solar conditions in Hong Kong

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
GSR	11.63	10.69	11.24	13.14	16.12	16.55	19.15	17.61	16.49	15.46	13.39	12.03	14.46
% sunshine	45	30	26	29	38	40	56	52	49	54	55	54	44
Cloud %	58	73	76	78	74	75	65	66	63	56	53	49	65

Note:  GSR = mean daily global solar radiation (MJ/m²); % sunshine = percentage of possible bright sunshine (%); Cloud % = Cloud amount (%)

Table 2. Average temperature and humidity in Hong Kong

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
DBT	15.8	15.9	18.5	22.2	25.9	27.8	28.8	28.4	27.6	25.2	21.4	17.6	23.0
% RH	71	78	81	83	83	82	80	81	78	73	69	68	77

Note:  DBT = dry bulb temperature (^oC); % RH = relative humidity (%)

Average temperature and humidity in Hong Kong are given in Table 2. With an annual dry-bulb temperature of 23.0 ^oC, the heating demand in most buildings in Hong Kong is not significant. The cooling requirements is large in the summer period which lasts from May to October. The humidity level remains high in months from February to September and this presents a need for dehumidification or sufficient ventilation in most buildings in order to maintain human comfort.
 

3. Major Constraints

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.

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.
 

4. Solar Thermal Applications

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.

Table 3. Examples of large-scale solar thermal applications in Hong Kong

Year completed	Location	System description
1978	A hotel and office complex in Tsimshatsui facing Victoria Harbour (* by a private developer)	280 nos. of flat-plate collectors each 900 mm x 2130 mm
1983	A drug addiction treatment centre on a remote island (Hei Ling Chau)	400 m2 of flate-plate collectors and two 16,000 litre solar water storage tanks
1983	A prison on Lantau Island (Shek Pik)	450 m2 of flate-plate collectors and five calorifiers of capacity 36,400 litres
1994	A hospital in a new town (Tuen Mun)	96 m2 of solar panels designed to serve a hydrotherapy pool
1998	A swimming pool complex in a town area (Kwai Chung)	168 nos. of solar panels with total 330 m2 to support swimming pool heating
1999	A new slaughterhouse in rural area (Sheung Shui)	450 nos. of solar panels to provide hot water for processes

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.

A pilot scheme on a PV system for lighting has been carried out in the Kowloon Walled City Park which is a public park located in the middle of the city. Other PV applications are being investigated in some research projects of the local universities. Unlike western countries, PV applications on rooftop and open space are limited in Hong Kong, except for a few rural areas. Effective strategy and technology are needed to apply PV in the urban environment so that high-rise buildings in Hong Kong could benefit from renewable energy supply.
 

A weather station powered by photovoltaic panel

PV research at a university in Hong Kong (Photo: H X Yang)

The concept of building-integrated photovoltaic (BIPV) system is believed to be a potential area for solar applications in Hong Kong because it can fit PV cells or panels into the building components such as building facade, shading device and roof. By combining the functions of the PV panels, the overall investment of the system can be reduced significantly. To put this concept into practice, the Hong Kong Government is planning in the year 2000/2001 to install PV systems on two government office buildings which have curtain wall construction in their building facades. The electricity from the PV panels will meet part of the electrical energy demands of the buildings.

As the costs and space for battery storage often create difficulties to PV system design, pilot research is being carried out to investigate how grid-connected PV systems can be used in Hong Kong to eliminate the need for battery storage. Connecting PV or other renewable energy systems to the electricity grid requires the cooperation of the power companies. Current electricity regulations and the control scheme between the Government and power companies will have to be reviewed so as to arrange for effective power generation, distribution and purchasing. The possible control problems, local pollution and the effective use of land have to be considered when making the final decision.
 

6. Government 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.
 

7. Relationship with Mainland China

One very important thing is the Hong Kong's relationship with mainland China and its implications to renewable energy development (Hui and Cheung, 1998). If Hong Kong, in pursuit of renewable energy, could adopt an integrated approach through collaboration with Southern China (such as Guangdong) which has abundant renewable energy resources and land, then the cross-boundary cooperation would bring about greater benefits to both sides. As the electricity transmission system of Hong Kong is interconnected with the Guangdong Province in the mainland China, it is possible for Hong Kong to make use of the mainland's renewable energy resources to meet its energy need in an environmental friendly and sustainable way.

It is clear that China is keen to develop renewable energy (Lindley, 1998). For example, in the coming years, the largest solar product manufacturing plant in China will be built in Shenzhen (through joint venture with a French company). If Hong Kong could play an active role in promoting renewable energy development in mainland China, such as by serving as a financial intermediary and an information and technology gateway, then good business opportunities and industrial development may be generated.

An interesting example of such collaboration is a "solar-powered air-conditioning" project in Jiangmen City, near Guangzhou in southern China (Wolin, 1998). A university professor from Hong Kong has been the project leader working with colleagues at Guangzhou Institute of Energy Conversion to design and implement this innovative project.
 

8. Future Prospects

It will take time to evaluate the potential of active solar energy systems in Hong Kong and develop cost-effective strategies for large-scale and/or commercialized application. In short term, these systems are unlikely to spread widely in Hong Kong and the energy saving methods will continue to be the main focus for improving energy efficiency in buildings. Measures like passive solar design, passive cooling, shading and sun control, ventilation strategy, use of natural sunlight, energy efficient lighting and air-conditioning should be fully explored.

In medium to longer term, solar thermal and photovoltaics should play a more important role in meeting Hong Kong's energy demand. Opportunities in other renewable areas such as wind energy, small hydro, solar hydrogen, and biomass should be evaluated to identify potential niche markets for their application. Knowledge and skills about the renewable energy systems is useful for promoting them in mainland China, even though they might not be applied in Hong Kong.

Another related area is the Asia's largest refuse incinerator that the Hong Kong Government is planning to build in the coming years. Although the purpose of the incinerator is to reduce the volume of waste in Hong Kong, useful heat/electricity can be produced by the waste-to-energy facilities.

Experience in USA and Europe indicates that the role of utility companies is quite important for renewable energy deployment. With a world-wide trend for utility deregulation, it is necessary to review and redefine the role of Hong Kong's utility companies so that, instead of creating barriers to private renewable generation, they could make active contribution to the "solar business" in the energy market.
 

9. Conclusions

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.
 

References

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• HKO, 1999. Monthly Meteorological Normals and Extremes for Hong Kong, Hong Kong Observatory (HKO), "http://www.info.gov.hk/hko/wxinfo/climat/normals.htm".
• Hong Kong Government, 1985. The progress and development of solar energy in Hong Kong, In Proc. of the Regional New and Renewable Sources of Energy Development Programme for Asia and Pacific, November 1985, Bangkok, published by United Nation.
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• Hui, S. C. M. and Cheung, K. P., 1998. The role of Hong Kong in the development of renewable energy in China, In Proc. of the World Renewable Energy Congress V, 20-25 September 1998, Florence, Italy, pp. 2571-2574.
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• Lindley, D., 1998. An overview of renewable energy in China, Renewable Energy World, Vol. 1, No. 3, November 1998, pp. 65-69.
• Planning Department, 1999. Study on Sustainable Development for the 21st Century, Planning, Environment and Lands Bureau, Hong Kong, "http://www.info.gov.hk/planning/susdev/venue-e.htm".
• Wolin, M. L., 1998. Cooling down, Far Eastern Economic Review, Vol. 161, Iss. 41, October 8, 1998, pp. 80.