By Cheng Ya-Tang & Hsu Jen-Ming Power Research Institute, Taiwan Power Company
The indigenous energy is unproportionately deficient in the Taiwan area. The vast majority of energy supply is imported and the percentage keeps rising in recent years. In 1993, Taiwan imported 96% of the total energy, leaving 4% of its energy obtained locally. This makes the development and utilization of renewable energy remarkable important.
This paper briefly describes the conditions of applications and the undertaking of the research status of hydropower, geothermal, solar, wind, wave, tidal and ocean thermal energy conversion as well as bioenergy in the Taiwan area.
II. Resources and Application Demonstration
Hydropower is the most precious indigenous power and plays a very important role in electric power system in Taiwan. Altogether there are 129 large and small rivers in the region. According to the survey, the theoretical hydropower resources amount to 11,730 MW, of which 5,100 MW would be technically feasible. Presently, there are 36 hydroelectric power plants (including the Ming-Hu Pumped Hydropower Plant) with 76 generators totaling 2,576 MW in capacity. Among these plants, there are 10 mini-hydropower plants (capacity less than 2 MW) with 21 generators totaling 15 MW. In 1993, the total electricity generated by hydropower was 6.7 X 109 kWh. The total capacity of power plants currently under construction including the Min-Tan Pumped Hydropower Plant, the New Tien-Lun Hydropower plant and the Ma-An Hydropower plant is 1,852 MW.
2. Geothermal Power
A preliminary estimate on geothermal power resources in Taiwan area was made. Results show that there are close to a hundred areas having hot springs in the island which are geologically active and have high potential in geothermal power generation.
Consolidating results from previous geothermal surveys, there are 26 primary areas in Taiwan where the potential power generating capacity totals 1,000 MW approximately which matches close to 2.5 million tons of coal equivalent per year. Estimating 30 years power generation by this energy source represents a significant amount of 75 million tons of coal equivalent. Mt. Ta-Tun area with 500 MW potentials is among the largest potential. The less potential areas include Tsing-Tsui, Tu-Chang and Kim-Lun areas, each having between 25 to 70 MW in capacity. In thermal application of geothermal energy, the potential capacity is 5 X 1015 kJ approximately, close to 180 million tons of coal equivalent. Hence, the total potential of geothermal energy in Taiwan can be as high as 255 million tons of coal equivalent.
Generally speaking, the temperature of geothermal water from volcanic systems is high. However, it is also acidic and corrosive, not suitable for power generation. For instance, because the material presently available could not handle the corrosive problems of the acidic geothermal water from Ta-Tun area, this energy could not be further utilized. Conversely, the geothermal water from non-volcanic systems is weakly alkaline in nature with lower temperature of around 100 to 200¢XC, suitable for power generation and other uses. Both the Tsing-Tsui and Tu-Chang geothermal power plants in I-Lan area use the geothermal hot water and steam of this non-volcanic system.
The first geothermal power plant in Taiwan area is the Tsing-Tsui power plant which was installed in 1981. Using direct flashing power generating method, the designed capacity is 3MW. Since its commercial commission, the capacity drp[[ed from 945 kW in 1982 to 250 kW in 1993. The most probable cause for its decline in capacity may be attributed to the deficiency in geothermal resource, as well as the severe scaling in the wells that causes the diminishing of the production of hot water and steam. At present, confronting the losses in operation, the Chinese Petroleum Corporation has decided to close the wells and the Tsing-Tsui Power Plant was forced to terminate its power generations.
The Tu-Chang Geothermal Power Plant located in the Tu-Chang geothermal multi-purpose demonstration area is the second geothermal power plant in Taiwan. It uses the binary cycling power generation method and the designed capacity is 300 kW. It was commissioned to the power grid of the Taiwan Power Company system in November 1986. In addition, carbon dioxide was recovered from the geothermal fluid, and flower cultivation inside greenhouses, as well as geothermal space heating and other uses were also demonstrated.
3. Solar Energy
Power generation from solar energy can be divided into solar thermal power generation and photovoltaic power generation. Solar thermal power generation is similar to traditional thermal power generation while photovoltaic power generation transforms the solar energy directly to electricity making use of photovoltaic effects from semiconductors.
Averaging 320 cal/cm2/day of solar energy in the Taiwan area, the total potential energy resources in this area of 36,000 square kilometers can be approximated at 4.89 X 104 TWh. Estimating the conversion efficiency of solar cells to be 10%, the total theoretical energy for the whole area in Taiwan can be as high as 4.89 X 104 TWh.
The area needed to generate 0.1 kW of electricity by photovoltaic cells is about 1m2. Estimating 1% of the total construction area of Taiwan of 1,557 km2 to be used for producing electricity from photovoltaic power generation, the total potential capacity then is 1,557 MW.
In helping the general public in understanding the applications of photovoltaic systems, a few demonstration projects have been set up, such as the indication lights to the emergency shelter in Mt. Chi-Lai and Mt. Nan-Hu, as well as the lighting system in the pedestrian paths of the White Pine Falls in the Tairouko national Park. In addition, a 10 kW photovoltaic system was set up in the highest point in Taiwan, the Jade mountain meteorological Station. For large scale applications, more time would be needed for the technological advancements that lead to economical feasibility of the photovoltaic system.
The method used to generate electricity from solar thermal energy is to concentrate the solar energy and convert it into thermal energy of higher quality. Electricity is then generated using the common thermal cycle as in other traditional thermal power plants. The thermal cycle efficiency is approximately 10 to 20%. The efficiency of curvilinear surface solar heat collectors is better than the tower solar heat collector. The solar thermal power generation as well as dehumidification air conditioning in Taiwan still need further research and development because of economic reasons. Preliminary success can be observed in the application of solar water heaters in Taiwan area. Since the initiation of the 'Solar Water Heater Promotion Act' by the Energy Commission of the Ministry of Economic Affairs in 1986, the total area of solar collectors installed has amounted to 4.6 X 105 m2 by the end of 1993.
Because the cost of solar cells is still high at present, they are not widely used in power generation. It is hoped that with the continuation of research and development together with the rising concerns of environmental protection, power generation by solar cells will become more common as time progresses. Looking into the future, it is estimated that 160,000 kiloliters of oil equivalent of energy supply will be furnished by solar power in the year 2000.
4. Wind Power
Because the northeast monsoon is common the Taiwan area, the average wind speed exceeds 5 m/s in coastal areas, mountains and remote islands. Hence, the potential of wind energy in these areas are high. According to a survey previously performed by the Energy and Resources Laboratories of the Industrial Technology Research Institute, the total area in Taiwan having an average wind speed higher than 5m/s is as large as 2,000 square kilometers. Hence, the minimum potential of wind power can be estimated to be 1,000 MW.
The development of the applications of wind power was initiated by the Energy and Resources Laboratories (ERL) of the Industrial Technology Research Institute. Additional institutes include National Tsing Hua University, Central Weather Bureau, Academia Sinica, Taiwan Power Company as well as other entrepreneurs. Prototypes of wind power generators of 4 kW, 40 kW and 150 kW capacity were successfully developed by ERL. On the applications of the power generations, the Taiwan Power Company has installed 2 wind power generators of 100 kW capacity each in Chi-Mei of Peng-Hu isalnd. These power generators are connected to the power grid together with the existing diesel power generators. According to the results of the computer simulations, the average power generated is 720 MWh per year, saving as much as 200 kiloliters of light diesel oil annually.
In addition, the yearly average wind speed on the main island of Peng-Hu reaches more than 6 m/s. Hence, the potential of using wind power is high and is possible for developing large scale wind farms to generate electricity. According to the planning study performed by the Taiwan Power Company, it proposed to install the second wind power plant along the embankment of the Che-Kang Ground Water Reservoir in Peng-Hu. The total capacity is about 2 MW and the construction will start in 1995 to be ready for operation in 1996.
5. Wave Power
The total coastal length in the Taiwan island is 1,448 km. The coastal area is constantly subjected to monsoons throughout the year and is therefore rich in wave power resources. Since 1987, the Taiwan Power Company has started to investigate the coasts of the Taiwan island and the prime remote islands on the feasibility of using wave power. Results show that the northern coasts in the Taiwan island and some areas of remote islands have higher potentials with 13 kW per meter of coastal line. The eastern and northwestern coastal areas of the main island are next in wave power potentials of 7 kW per meter and the southwest and that of south coasts is 3 kW per meter.
Lan-Yu island, located at the southeastern corner off the coast of the Taiwan island, was chosen by the Taiwan Power Company as the first site for the demonstration project of using wave power. The project aimed at conceptual designing and planning of an exemplary model of wave power plant. The feasibility result showed that the capacity installed could be of 1 MW capacity, with an average of 371 kW power generated in winter seasons and an average of 129 kW in summer seasons when the sea is calm. This gives a yearly average of 218 kW. Later the plan was abandoned considering the less convenient transportation between the main island to the plant site, as it constitutes higher costs in the overall planning. To cut down the cost of installation, another plan currently under consideration is to place the wave power plants having caisson structure designs in the vicinity of the wave protection embankments of intake cooling water for the Fourth Nuclear Power Plan.
6. Tidal Power
Tides along the coasts of Taiwan area are the greatest in Ma-Chu island. Next would be along the coasts from the south of Nan-Liao in Hsin-Chu to the north of Wang-Kung in Chang-Fa where the average heights between tides could be as much as 3.5 m, merely meeting the minimum requirement for tidal power generation. The average heights between tides of other coasts in the Taiwan area is less than 2 m, much shorter than the ideal 6 to 8 m for this power generation method. Because most of the west coast of Taiwan is flat and with straight sand beaches, there are no ideal geographical site suitable for building short dams to hold large pools of water for tidal power generation. Hence, the conditions for developing tidal power in Taiwan area are not optimistic.
7. Ocean Thermal Energy Conversion, OTEC
The shape of the surface of the sea bottom off the eastern coastal area of Taiwan is steep, having a depth of 800 m not very far from the coast and the temperature of bottom water is close to 5¢XC. Because of these leverages both in geographical shape and water temperature, the potential for power generation by OTEC is high. Hence, the Taiwan Power Company has been working on a series of studies since 1981, studying the feasibility of developing power generation by ocean thermal energy conversion method in the coastal area in the eastern part of Taiwan.
According to the data on investigating deep water in the larger area in the near sea off the eastern coast of Taiwan, survey on environmental data for power plant sites, together with on-site investigation, the Taiwan Power Company provisionally chose Ho-Ping, Shi-Te and Chang-Yuan as candidate sites for the OTEC power plant. From the data on resources of the temperature differences of different depths of sea water, Chang-Yuan would be the best site, followed by Shi-Te and Ho-Ping would come on top, followed by Chang-Yuan and Shi-Te.
After this series of studies, the Taiwan Power Company proposed to build a 5 MW prototype plant for multiproduct applications and demonstrations in both power generation and aquatic nursery using the temperature differences of sea water at different depths. However, detailed geological survey shows signs of rock sliding in the sea bed at the Ho-Ping plant. Hence, this plan was abandoned and a different research project was initiated on the Chang-Yuan plant site.
Biogas can be produced through anaerobic digestion of micro-organisms from rural and urban refuse such as animal excrement, agricultural waster, city garbage and industrial waste water. According to the report on guidelines for developing bioenergy research written by the Energy Commission in 1985, about 120 million tons of biomass are produced each year in Taiwan, a large portion of which is not treated and utilized effectively.
The research in anaerobic digestion and treatment of excrements from hogs was started by the Taiwan Livestock Research Institute and co-sponsored by the Council for Agricultural Planning and Development and Taiwan Provincial Department of Agriculture and Forestry beginning in 1971. This research also aimed at developing different uses of biogas including cooking, power generation and transportation.
In 1981, the Energy and Resources Laboratories installed a system capable of treating excrements from 200 hogs for Kaohsiung Ta-Li Agricultural Livestock company. Biogas produced from this system is used for combustion and power generation directly. In addition, the Chu-Nan Animal Industry Research Institute of the Taiwan Sugar Company has set up a system capable of treating excrements from 200 hogs for Kaohsiung Ta-Li Agricultural Livestock company. Biogas produced from this system is used for combustion and power generation directly. In addition, the Chu-Nan Animal Industry Research Institute of the Taiwan Sugar Company has set up a system capable of treating excrements from 10,000 hogs. The biogas produced from this system is used to supply the energy for the power generator of 170 kVA capacity, producing electricity for the hog farm.
Table 1 Summary of Renewable Energy Potentials in Taiwan Area
|Hydro||11.7GW with annual generation of 103 TWh||5.1GW with annual generation of 6.7TWh|
|Geothermal||1,000MW power generating capacity and 5¡Ñ1015 kJ thermal capacity totalling 2.55¡Ñ109 tons coal equivalent||20 to 30% of estimated potential|
|Solar||4.89¡Ñ104 TWh annually||1.557MW|
|Wave||1,448 km total coastal length, providing 10GW power production||100MW|
|Tidal||3.5m average range of tides||not optimistic|
|OTEC||0.46¡Ñ103 TWh annual generation||46 TWh annual generation|
|Biomass||about 120¡Ñ106 tons per year||700¡Ñ106m3 of biogass per year|
The livestock industry in Taiwan has reached the stage of large scale entrepreneurship. At the end of 1992, the total number of pigs raised is 9,754,460, and that of chickens and ducks are 87,691,000 and 14,719,000, respectively. The excrements from these animals are tremendous. At present, the biogas utilized in Taiwan can be classified as prepurified and purified of which the larger proportion is the former type.
Large scale refuse biomass that is suitable for producing biogas in Taiwan includes excrement from hogs, urban garbage and manure domestic waste water as well as organic waste water from various industries. If anaerobic digestion is used for treatment, 700 million cubic meters of biogas can be produced each year. It is therefore worthwhile to develop bioenergy as it exhibits potential markets.
III. CONCLUDING REMARKS
Since power generation from renewable energy is limited by its natural and inherent conditions, the time of power generation and its stability are difficult to control. For the average cost of electricity of NT$ 1.18 per kWh currently experienced by the Taiwan Power company, there are very few favorable reasons for power generation from renewable energy. Hence, renewable energy can only play a supplemental role or alternative for partial power generation but not used as prime source of energy supply. However, in the midst of the global environmental concerns, the promotion and acceleration of the application of renewable energy in Taiwan will be inevitable.
According to the estimation from the "Total Energy Planning in Taiwan Area" published by the Energy Commission in 1992, the renewable energy supply in 2005 will be as high as 1,294,000 kiloliters of oil equivalent and will reach 2,520,000 kiloliters of oil equivalent, about 2% of the primary energy in the year 2010. Details of this estimation can be found in Table 2. This shows the advancement of the utilization of renewable energy in the future and its limitation to become a major component in energy supply. Further development and integration in the use of renewable should be emphasized.
Table 2 Estimation of Renewable Energy Supply in Taiwan Area
|Year||Solar||Wind||Biomass||Geothernal||Ocean||Total||Percent of Total Primary Energy Supply|
Unit:103 Kiloliters of Oil Equivalent