1 USE OF SOLAR PV ENERGY TO REPLACE NUCLEAR POWER IN TAIWAN Bin-Juine Huang, P.C. Hsu, Y.H. Wang, J.H. Tsai, Leo Chen, Kang Li, KY Lee + Department of Mechanical Engineering Department of Engineering Science and Ocean Engineering + National Taiwan University, Taipei, Taiwan. ABSTRACT: The present study shows that performing energy saving retrofit in air conditioning (A/C) and lighting then utilizing solar PV energy to supply the remaining load demand in grid can reach non-nuclear goal in Taiwan. An office was chosen as the demonstration site (D-1). Four energy-saving retrofits on air conditioning and lighting results in 65% energy saving. A 6 kWp solar PV system for self-consumption and without feeding energy back to grid is further installed to replace additional 20% energy to reach 85% total energy saving. The total investment for solar PV system and energy-saving retrofit is USD30,000. The net total energy saving in 20 years is USD80,000, including M&O cost. If energy-saving in air conditioning and lighting can reach 60% as D-1 did in the whole country, the nuclear power (18% electricity) can be abandomed. Several scenarios to reach non-nuclear goal are proposed. The energy storage for each 3 kWp PV unit is estimated around 4-6 kWh. Heat storage can be utilized to reduce cost dramatically as it is 10 times cheaper than battery. Keywords: PV System, Solar Home System, Hybrid PV 1 INTRODUCTION Since Taiwan is located in subtropical area, there is a peak load around 13:00 during summer around 34GW. From a long-term study, the power consumption of air conditoning contributes about 9 GW. Energy saving of air conditioning systems is thus most important. Taiwan Government has set up a energy-efficiency classification for all air conditioners since 2010. Five categories are defined according to the energy efficiency ratio (EER) (W/W) and cooling capacity. See Table 1. However, EER of majority of air conditioners in the market or ever installed is below 3.5 (Category 3~5) . In 2010, 70% of air conditoners belongs to Category 5. Large potential of energy saving is feasible since the EER of the most advanced air conditioner in the market is higher than 5.6. Table 1: Category of air conditioners Brand Cooling capacity, kW EER (W/W) Category 5 4 3 2 1 Integral- type <2.2 <2.95 2.95~3.1 3.1~3.25 3.25~3.4 >3.4 2.2~4.0 4.0~7.1 7.1~10 Split-type <4.0 <3.45 3.45~3.69 3.69~3.93 3.93~4.17 >4.17 4.0~7.1 <3.2 3.2~3.42 3.42~3.65 3.65~3.87 >3.87 >7.1 <3.15 3.15~3.37 3.37~3.59 3.59~3.81 >3.81 Besides, lighting consumes about 10~15% energy in Taiwan. It is known that LED (light-emitting-diode) can save more than 50% lighting energy. Thus, lighting energy saving using LED is also feasible. The cost of solar PV energy is reduced dramatically recently to bring the grid-parity age to come. Energy from solar PV is equal or cheaper than from the grid. High-efficiency air conditioning, LED lighting, and low-cost solar PV are all technically mature and available in the market for energy saving. The purpose of the present work is to demonstrate that, the utilization of solar PV energy in buildings for peak shaving, associated with energy-saving retrofit, can solve the energy shortage problem when nuclear power is abandoned in Taiwan (Figure 1). Figure 1: Schematic diagram showing peak saving by energy saving and peak supply by PV to abandom nuclear power. 2 ENERGY-SAVING RETROFIT OF OFFICE 2.1 Energy consumption before energy-saving retrofit The office of the Department of Mechanical Engineering, National Taiwan University, with 150m 2 floor area and occupied by 15 employees, was chosen as the demonstration site (D-1). The major energy consumption of the office comes from air conditoning, lighting, and PC. The power and daily energy consumption of air conditioners, lighting, and laptop PC was calculated and listed in Table 2. It is seen that the total power consumption for air conditioners, lighting, and PC reaches 10.16 kW and the daily total energy consumption reaches 81.3 kWh. 64% energy is consumed by air conditioners. 2.2 Energy-saving retrofit and energy consumption To reduce energy consumption, four retrofitting was carried out: (1)air conditioning system is renewed with high-efficiency split-type air conditioner (Hitachi RAC- 22NB) with COP 5.6; (2)lighting is retrofitted with LED luminaire with 100 Lm/W; (3)all lap-top computers are changed into notebook PC; (4)the window glass is covered with low-E film to block IR part of solar radiation penetrating into the office. The above four retrofits results in 65% energy saving as shown in Table 3, at average power 3.6 kW and daily energy consumption 28.6 kWh/day.