Patrick Collins*, Yuliman Purwanto** & Xu Chuang Ji***

The Asia-Pacific region as a whole consumed some 35% of world energy supply in 1990, and has since grown to exceed energy consumption in Europe. The average growth rate of energy consumption in the region is about 4% per year, approximately twice the world average, and by 2005 it is predicted that the Asia-Pacific will represent some 40% of world energy consumption.

Currently supplied by many different sources, one additional possibility for the future is the reception of large-scale microwave power beams transmitted from orbiting satellites. Such beams could each provide as much as several gigawatts of electricity. The dedicated microwave power receiving antennas, or "rectennas" required for this purpose would cover tens of square kilometers if the Industrial, Scientific and Medical (ISM band) frequency of 2.45 GHz is used. This will make this power source relatively attractive to countries with large areas of low-value land.

Considered as specialised terrestrial electricity supply facilities which purchase "microwave fuel" from orbiting power satellites owned and operated by different companies, rectennas could make a significant contribution to electricity supply in appropriate countries.

In recent years both China and Indonesia have had energy growth rates that are approximately twice the average of the Asia-Pacific region, making them increasingly important consumers of energy. Both countries also have large areas that are potentially suitable for construction of multiple rectennas of this scale, making them both potential large-scale users of microwave power from space in the future.

Due to their large and suitable areas, both countries also have the potential to collect microwave power and to export electric power to neighbouring countries which are less well-endowed with land area. The potential for these two countries as SPS users is considered in turn below.

China has a land area of some 9.3 million square kilometers, and a population of some 1,200 million. The trend of population growth suggests that China's population will reach 1.3 billion by 2000, 1.4 billion by 2010,　and 1.5 billion by 2020. Energy demand in China has been growing recently at an annual rate of 8.9%. Due to this rapid increase in demand, China has become a net importer of oil since 1993. Since it is intended that the energy consumption level per capita should reach the same level as in the advanced countries, the demand for energy will grow to become much higher than the supply that is expected to become available domestically. Consequently in future the potential market in China for new energy supply systems will be very large. Population distribution and energy demand

Some 94% of the Chinese population live in the eastern part of the country comprising 45% of the area, while only 6% of the population live in the sparsely populated western part of the country comprising 55% of the total area. The highest population density is centered in East China and Central China and along the eastern sea-board. The national population distribution is shown in the following table.

The unequal distribution of the population can be seen clearly. It is made even more clear by considering that the sub-section of the country represented by the sparsely populated districts Nei Mongol +Tibet + Gansu + Qinghai + Ningxia + Xingjian contains only 6.2% of the total population, but represents 54.6% of the total land area.

In contrast to the population distri-bution, the distribution of energy resources is mainly concentrated in North China and the northeast and northwest regions. Thus the present situation, in which coal reserves in the west are transported to the east, and coal supplies from the north are transported to the south, can be expected to continue.

Rapid growth in demand for energy is expected to continue in the east where economic growth is strong. Demand will also increase in those western areas which have relatively higher populations and are achieving local economic development. However, unless there is large-scale migration from the east to the west, the overall pattern of electricity supply and demand will continue to maintain its present character.

There are 556 billion tons of known reserves of coal, of which 167 billion tons are exploitable, giving 141 tons per capita, putting China in the 70th position in the world (1993). Average consumption is one ton of coal per capita per year, the 89th in the world, and between 5% and 10% of the average consumption in advanced countries.

In the year 2000, demand is forecast to be 1.9 billion tons of standard coal, of which some 1.4 billion tons are expected to be supplied, leading to a shortfall of some 0.5 billion tons. In the year 2010 demand is expected to reach 3.0 billion tons of standard coal, of which some 1.9 billion tons could be supplied.

3.3 billion tons of oil and gas are known to be exploitable, 1/50 of known world reserves, which are expected to last for another 22 years. However, environmental pollution by CO2 from fossil fuel burning in China is already second in the world. Economic losses due to this are estimated to be more than RMB 10 billion/year, and further large increases are not attractive.

For recording the distribution of electric power supplies the country is divided into North China, Northeast China, East China, Central China, Northwest China, South Union (4 provinces) and 10 independent province networks. Among these supply networks 4 have more than 30 million kW capacity, the South Union and East China networks each having 40 million kW capacity.

Total capacity in 1997 was 250 million kW, and electricity consumption in 1997 was 1,135 billion kWh. This is equivalent to 0.21 kW per capita, which is 1/3 of the world average, putting China in 85th position. In addition there are some 60 million people living in 11 counties in China who still have no electricity supply. The supply target of the electricity industry is to reach 290 million kW capacity by the year 2000; to reach 500 million kW capacity by the year 2010; and to reach 700 - 800 million kW capacity by the year 2020.

However, the present speed of net electricity generation capacity construction is too slow; the design of power-generating and power-utilising equipment is unsatisfactory; and the relative development of different geographical areas is unbalanced, so it will be difficult to reach these targets. Indeed, the development of electric power supply capacity can probably only maintain the present average level per capita. In order to keep up with the national economic growth rate of 8-9% it is considered necessary to achieve an annual supply growth rate of 5-6%. Consequently concepts for new sources of energy are potentially of great interest.

After the United Nations' world environment and development meeting in 1992, the Chinese government proposed measures to encourage the exploitation of clean energy sources such as solar energy, wind energy, geothermal energy, tidal energy and biomass energy (2). Subsequently a 15-year plan was prepared for research and exploitation of new and renewable energy sources to run from 1996 through 2010 (3).

Following the 47th IAF Congress in Beijing in 1996, the concept of solar power from space was considered, and it was included in the developing programme of higher science and technology to be studied, demonstrated and exploited in the future (2).

From an economic point of view, rectennas for collecting microwave power beams delivered from space have the advantage that they are relatively low-technology and could be efficiently constructed, operated and maintained using relatively labour-intensive methods with relatively low-cost staff. Thus they could be attractive investment projects compared to other power sources that require more capital investment and staff with advanced educational levels.

Rectenna siting

As shown above, some 38% of the population live in some 17% of the land area in the east and north-east areas of the country, making it more than twice as densely populated than the average. Thus it would not be easy to select land areas suitable for siting large-scale rectennas in the east of the country where the energy demand is highest.

However eastern China also has a long sea coast, where there are a large number of islands. It may be feasible to site rectennas on some of these islands and/or in the neighbouring areas of shallow sea. These rectennas could be used for supplying power to the large and dense populations in the east of the country.

In western China there are many deserts, both large and small in area. Rectennas could be located economic-ally near the edges of such deserts at sites which are not far from regional population centres. Land purchase costs would be low, and construction and maintenance costs should also be low due to the benign environment. However it will not be attractive to set up large rectenna power stations for the least-populated areas since the effective economic demand for the power produced would be insufficient. This situation will change progressively in the future as electricity distribution grids become more advanced and long distance electric power transmission becomes more cost-effective. Recent progress in high-temperature super-conductor technology has raised the possibility in future of lossless transmission over long distances of thousands of kilometres. In this case, transmission of electric power from western districts to eastern districts could be expected to increase substantially.

Export potential As such long- distance power transmission becomes feasible, neighbouring countries could also become potential customers for electricity exports from China if it was decided to build and operate some rectennas for this purpose. In such a scenario, one potentially major customer for electric power exports from China in the future is Japan, which is particularly poorly endowed for siting large-area rectennas, having a relatively small land area of which a large proportion is steep mountains.

This would require even longer-distance power transmission. However, conceptual plans have already started to be prepared for a global electric power distribution grid which would make this possible (4). As different countries' national electricity grids are extended over the coming decades they will find advantages in progressively linking together, enabling them to transmit power to different time-zones and thereby profit from the price differences between peak and off-peak supplies. Described as the "Genesis Project", north-east Asian connections in such a grid will include high-voltage links from China through Korea to Kyushu and Yamaguchi in the south of Japan, and from Siberia through Sakhalin to Hokkaido in the North (4). Completion of these links could open very large export markets to rectennas sited in the least used desert regions in the west of China.

Indonesia has a land area of some 1.8 million square kilometres and a population of more than 200 million, of which the density varies widely between districts. For example, some 64% of the population live on the island of Java which has only 7% of the area.

Having achieved economic growth averaging some 7% per year through the first half of the 1990s, commercial energy demand for the 1995 - 99 period is predicted to grow at an average of about 10% per year. Electric power demand for the same period is predicted to grow at about 15% /year.

Proven coal deposits are concentrated in Sumatera with 26 billion tons (72%) and Kalimantan with 10 billion tons (27.3%). Java (with 72 million tons), Irian Jaya/West Irian (with 72 million tons), and Sulawesi/Celebes (with 36 million tons) have just 0.5% of national reserves. These reserves may last from 40 years to more than a century, depending on the rate of consumption.

There are proven deposits of about 5.6 billion barrels of oil, which will be exhausted within some 11.5 years. Potential deposits of some 48.5 billion barrels are expected to be finished in 100 years, at the same rate of consumption. Proven deposits of gas are expected to be exhausted within 35 - 65 years.

Existing sources of hydro-electric power are about 76,000 MW, spread between more than 1,300 locations, including 22,400 MW in Irian Jaya (West Irian Island), 21,600 MW in Kalimantan Island, 15,800 MW in Sumatera Island, 10,200 MW in Sulawesi Island (Celebes), 4,500 MW in Java Island, 700 MW in Bali and Nusa Tenggara Islands, and 400 MW in Moluccas Islands (5).

It has been estimated that hydro-electric power supplies could potentially reach as high as 750,000 MW. However, development of these supplies would require enormous capital investments, and would have increasingly damaging environmental impacts as less and less efficient sites would have to be used.

Indonesia's energy and electric power policy are based on the following principles (5).

1. Substitution of non-renewable energy resources as far as possible.
2. Environmental conservation by:
   1. increasing the use of renewable energy resources.
   2. decreasing negative impacts on the environment of emerging energy resources.
   3. improving efficiency of non-renewable energy resource use in the transition period, and optimizing the utilization of renewable energy resources.
3. Diversification to reduce oil consumption and substitute other types of energy.
4. Increased utilization of alternative energy sources.
5. Electricity supplies for rural and remote areas to utilize local and renewable energy sources like hydro, solar, and geo-thermal gas energy.
6. Small-scale electric power supply projects in rural and remote areas to have the following priorities:

1st

wind, solar, and mini-hydro.

2nd

waste matter, dendro-thermal resources, and geo-thermal gas.

3rd

hybrid (gas/coal/oil) power.

4th

natural gas, coal, or oil power.

In the future, if solar power satellites are developed that are capable of delivering large scale microwave power to users on Earth at a price that is competitive with other energy sources, it could be attractive to Indonesia since it matches the requirements of this policy: use of microwave power could reduce the use of fossil fuels for electricity generation, and would cause minimal environmental pollution. It also matches the country's large area, as discussed in (6).

Rectenna Siting

Indonesia possesses more than 10,000 islands surrounded by shallow sea. Many of the smaller ones are unpopulated and could therefore be used for siting rectennas, as proposed by Purwanto et al (6). For large scale rectennas several such islands might be used to site a single large rectenna from which power could be delivered to population centers.

Export Potential Following the concept of the "Genesis project", described above, as it relates to Indonesia, in future there could be high-capacity international electricity grid connections between Indonesia and Singapore and Malaysia to the north, Philippines to the north-east, Australia to the south east, and eventually even India and Sri Lanka to the west. These would provide extensive opportunities for selling electric power to users in other time-zones which could help to optimise the utilization of large scale rectennas which are capable of generating power continuously.

As discussed above, in both China and Indonesia land and labour costs are relatively low, enabling rectennas to be constructed economically, and with less capital investment than in countries with higher average incomes.

In principle, the price that a utility company could pay per kilowatt-hour of microwave energy delivered from space is the difference between the cost of alternative supplies and the cost of using the rectenna. Thus countries with low rectenna costs and high demand for power will be able to offer attractive prices to suppliers of micro-wave energy from orbit, and will be supplied in preference to potential customers who have much higher rectenna costs, and who will therefore offer lower prices for microwave power.

Although rectennas can be designed so that the land beneath them can still be used for various purposes, siting full-scale rectennas some tens of square kilometres in area will have major implications for those living in the districts in question. Their planning will therefore require extensive coordination with regional long-term land-use plans.

The SPS project involves both the electricity industry and the space industry, and participation will require countries to select the role they will play, from the use of a rectenna for purchasing microwave power, to participation in the system design and/or manufacture of the satellites. Both China and Indonesia are actively investing in aerospace as a promising new industrial sector: by working in this industry, companies learn modern precision engineering, and other state-of-the art industrial techniques. Delivery of microwave power from space could grow into a major new business opportunity provided that launch costs are reduced sufficiently from their present levels to make it economical.

For the near term, an SPS pilot plant project, "SPS 2000", using a satellite in low equatorial orbit is being studied in Japan (1). Planned as an inter-national collaborative project to demonstrate the delivery of 10 MW of microwave power to rectennas sited within a few degrees of the equator, the current design specifies an altitude of 1100 km for the satellite which will deliver power for 200 seconds on each pass over a rectenna.

To date 8 countries, including Papua New Guinea, Indonesia, Ecuador and Colombia on the Pacific Rim, as well as Malaysia, Brazil, Tanzania and Maldives, have all agreed to participate in the project by planning a rectenna near the equator. The design of the first satellite to be used in the system has not yet been finalised, but realization of the first ever SPS pilot plant system is expected to stimulate interest in SPS among electricity supply companies around the world.

The southernmost parts of China's territory are too far north to host a rectenna for this demonstrator project, since the current specifications enable power to be delivered no further than 3 degrees from the equator. However, Indonesia has territory on both sides of the equator, and a study is currently under way of a potential site in Halmahera island in the north eastern province of Moluccas (6).

Halmahera rectenna site

Moluccas consists of some 1,200 islands, and covers 850,000 square kilometres in area, of which 90% is ocean. The major economic activities are fishing, plantations, wood industries, and tourism. The main commercial facilities are a banana plantation in Mobapura; wood processing in Bare-bare on Morotai Island, Sidangoli and Mangole; pearl cultivation in Kao, Lolobata and Meloka; lobster cultiv-ation in Kao-bay; sea-cucumber cultivation in Morotai-strait; and tuna cultivation in Weda-bay.

Tourism sites include Gunung Mamaju, Danau Duma, the 13th century palaces of Sultan Jailolo and Kesultanan Bacan, the National Parks of G. Sibela on Bacan Island (23,024 ha), Alam P.Seho (1,250 ha) and Lifamatola, and the wartime command quarters of the Japanese (1942-1945) and General Mc.Arthur (1945).

Potential land areas that can be developed include a 9,487 hectare airport corridor in Bosso, the 19,468 hectare Gane corridor in.Dodingan, the 13,063 hectare Akelamo corridor in Ekor, and the 7,400 hectare Patani corridor in Sagea.

Halmahera is the second largest island in the Province of Moluccas, after Seram, with an area of 18,000 square km, divided into 2 administrative districts, North Moluccas District and Central Halmahera District. The population is estimated to be some 30-40,000. There is a harbour in the neighbouring island of Ternate, and ferry stations at Bastiang and Sidangole. There are plans to develop two new airports in Halmahera, Bandara Gamar Malamo at Galela, and Bandara Kuripasi at Jailolo.

The potential for siting a pilot plant rectenna on Halmahera was discussed in the report of a field visit there in early 1996 (7). At that time the governor of Moluccas expressed support for participating in the SPS 2000 pilot plant project, and two attractive possibilities were identified. One would be to use unused open land near a village of several hundred inhabitants. The other would be to use one of many small uninhabited islands and transmit power by cable to the main island.

When developed and in operation, the planned system of 14 rectennas around the equator will provide an initial market for microwave power from space to which commercial satellite companies might also supply micro-wave power, as suggested in (8). Starting from this base, such a service could be expected to grow progressively in size up to large-scale satellites in geo-stationary orbit, of which both China and Indonesia could become major users.

In order for microwave power from space to become a serious candidate for large-scale electricity supply in the future, major progress is required in reducing costs of both launching cargo to low Earth orbit, and of long-distance electricity transmission technology. In that case SPS would have huge potential for providing essentially unlimited supplies of clean electric power to Earth (9).

However, in order to access this potentially major new energy source there is an urgent need for funding for appropriate studies in various fields, and for the realisation of an inter-national pilot plant project. In view of the many tens of $ billions of taxpayers' that are spent every year both on other energy projects and on other space projects, there is a strong case for some of this funding to be used for a project which would tackle both global environmental problems and global energy problems in a fundamental way (9).

Although the subject of using large areas of land for siting rectennas is a sensitive one due to the many people who could be affected by such decisions, long-term planning requires long lead-times, and so early consideration of possible sites, in both China and Indonesia, can already be useful.

1. M Nagatomo, 1996, "An approach to develop space solar power as a new energy system for developing countries", Solar Energy, Vol. 56, No 1, pp 111-118; also downloadable from www.spacefuture.com
2. Li Guoxin and Xu Chuangji, 1997, " On the future perspectives of space-based solar power plant to China", Proceedings of SPS 97, pp 11-18
3. Shi Ding-Huan, 1995, " Outline of the development of new renewable energy sources in China: 1996-2010", Chinese Solar Energy, No 3, pp 2-4.
4. Y Kuwano, 1992, " The new era of solar cells", Kodansha (in Japanese).
5. Elektro Indonesia, 1997, Department of Energy and Mining, National Electrical Power Company, December.
6. Y Purwanto, 1997, " A preliminary study of rectenna development aspects in Indonesia for SPS 2000 energy reception", ISAS Research Note 614.
7. H Matsuoka et al, 1996, " Field research for solar power satellite energy receiving stations: Indonesia", Matsuoka Lab. Working Paper 6, Tokyo University.
8. M Hoffert and S Potter, October 1997, " Beam it down: How the new satellites can power the world", Tech. Review, pp 30-36.
9. H Matsuoka, 1998, " Global environmental issues and space solar power generation: promoting the SPS 2000 project in Japan", Technology in Society, in press.