AORC Technical meeting 2014

http : //www.cigre.org C5-1036 AORC Technical meeting 2014 Solar PV Rooftop System Connection to MEA s Distribution Network: Technic and Economic Aspects Tosak Thasananutariya Metropolitan Electricity Authority Thailand SUMMARY In 2013, the Energy Regulatory Commission (ERC) in Thailand announced the purchase of electric power generated by solar PV rooftop system with the total installed capacity of 200 MW from Very Small Power Producers (VSPPs). ERC classified the power purchasing of 100 MW from residential and the rest 100 MW from the building of commercial and industrial. Moreover, ERC defined the Feed-in Tariff (FiT) as the purchase rate and also subsidize this FiT rate for 25 years. All power generation from solar PV rooftop system is supplied to network of two distribution utilities; Metropolitan Electricity Authority (MEA) and Provincial Electricity Authority (PEA). The commercial operating date (COD) is also defined within the end of December 2013. MEA is assigned to purchase electric power from residential and building of commercial and industrial with the installed capacity of 40 MW and 40 MW respectively. This paper presents the technic and economic aspects for connection and investment of solar PV rooftop system application in MEA s distribution network. The background of this project and classification of installed capacity and FiT rate of each VSPP group are introduced. In technic aspect, the regulation of solar PV rooftop system connection to MEA s distribution network is described. The technical definition of inverter such as power quality control and the response to operating voltage range, frequency range, islanding protection and reconnecting after power recovery is proposed. The limitation of power rating for solar PV rooftop system which impact to voltage, power quality and reliability of MEA s distribution network are recommended. The configurations of energy meter installation for low- and medium-voltage customers are illustrated. Moreover, the standard and important property of material, equipment and installation of solar PV rooftop system are discussed. In economic aspect, in order to determine the suitable financial parameters for investing the solar PV rooftop system, the internal rate of return (IRR) and net present value (NPV) are evaluated as the function of discount rates and investment costs. Furthermore, payback period is also calculated. The investment cost of solar PV rooftop system is varied from 60,000 to 10,000 Baht/kW and average electric energy generating per kilowatt is 1,300 kwh/year. The investment of solar PV rooftop system application to residential with installed capacity of 5 kw is evaluated with the variation of discount rate from 3 to 5 percent. As a result, the project can be invested if the initial cost of solar PV rooftop system and discount rate are not more than 60,000 Baht/kW and 4 percent respectively. KEYWORDS Solar PV Rooftop - Renewable Energy Source - Solar PV Rooftop Interconnection tosakt@mea.or.th

1. Introduction Presently, the fuel is used for electric power generation in Thailand depend on natural gas nearly 70 percent. Renewable energy would be counted as target fuel expected to significantly substitute natural gas for electric power generation, especially solar energy, wind energy by type of wind turbine farm, micro hydro, biomass, biogas and waste/garbage. Just in case such those renewable energy technologies would cost lower and getting broaden acceptance that could be developed as major energy for Thailand electric power generation in the future. Fig. 1 shows share of electric power generation by fuel type from January to December 2013. Source: Energy Policy and Planning Office (EPPO) Fig.1. Power generation classified by fuel type Global warming problem causing from GHGs (greenhouse gases) release is the problem currently getting the worldwide attention and speeding up to find restriction measures where trade barrier is one measure with a trend to widely use in the future. This would be an initial point to step into the low carbon society and be exemplary for the world society to cite Thailand as the country with strong intent in using renewable energy. Therefore, the government assigned Energy Ministry to establish Renewable and Alternative Energy Development Plan for 25 percent in 10 years, called AEDP 2012-2021, to identify the framework and direction of Thailand renewable energy development. Focusing on solar energy in AEDP framework, target in 2021 is 2,000 MW with a current total generating capacity at 75.48 MW. The small system project is promoted for installing at household and community level, including solar PV rooftop system, for 1,000 MW in 10 years. This system may be installed at houses in general and community, office buildings and factory roof, housing projects or condominiums, and government building. Moreover, the incentive measure which attraction for investment from private sector is adjustment of the Adder to be Feed-in Tariff (FiT) system. 2. Announcement of ERC on Power Purchase from Solar PV Rooftop System Referring to the Cabinet Meeting on 13 th August 2013, the Cabinet made an approval, according to the National Energy Policy Committee (NEPC) s resolutions of the Meeting no. 2/2013 (no.145) held on 16 th July 2013, on electric power purchase from solar PV rooftop at the feed-in tariff (FiT). By virtue of Section 11(4) of the Energy Industry Act B.E. 2556 (2013) and the Regulation of the Energy Regulatory Commission on Electric Power Purchase from Solar PV Rooftop B.E. 2556 (2013) dated 30 th August 2013, the ERC announce to inviting those who are interested in selling electricity generated from solar PV rooftop to submit their proposals with the following main conditions: 2.1 Electric Power Purchase from Solar PV Rooftop The power distribution utilities shall purchase electricity generated from solar PV rooftop, where the seller s Commercial Operation Date (COD) falls within 31 st December 2013. The classification of building types and their quantity generated at the overall installed capacity of 200 MW is shown in Table 1. The Metropolitan Electricity Authority (MEA) is the power distribution utility in Thailand responsible for supplying electric power to Bangkok and two neighboring provinces; Nonthaburi and Samutprakran cover the service area of 3,192 km 2. In 2013 the maximum power demand in MEA s system is 8,590 MW. The quota of electric power purchase from solar PV rooftop in MEA s service area is 80 MW which is classified in Table 2. 1

Table 1 Classification of building types and installed capacity Limit of installed capacity Installed capacity Building types (kw) (MW) 1. Residential not more than 10 100 2. Small business more than 10 to 250 100 3. Medium, large business/ industrial more than 250 to 1,000 Table 2 Classification of building types and installed capacity in MEA s service area Limit of installed capacity Installed capacity Building types (kw) (MW) 1. Residential not more than 10 40 2. Small business more than 10 to 250 40 3. Medium, large business/ industrial more than 250 to 1,000 2.2 Electric Power Purchase Tariff Electric power purchase tariff paid to a person who intends to generate electricity from a solar PV rooftop system must be in accordance with the Feed-in Tariff (FiT) as shown in the Table 3 for the duration of 25 years starting from the scheduled commercial operation date (SCOD). Table 3 Feed-in tariff Building types Limit of installed capacity FiT rate (kw) (Baht/kWh) 1. Residential not more than 10 6.96 2. Small business more than 10 to 250 6.55 3. Medium, large business/ industrial more than 250 to 1,000 6.16 3. Solar PV Rooftop System The solar PV rooftop system consists of photovoltaic panels which will generate direct current from solar energy. The generated direct current will be sent to grid connected inverter to convert into alternative current before the current will be supplied through watt hour meter and connected to network of power distribution utility as shown in Fig. 2. Fig.2. Solar PV rooftop system connecting to low-voltage system The solar cell system to be installed on building s roof consists of materials and equipment which describe in the following sub-sections, including other necessary installing materials that the installer use in installation of the system at the targeted location to ensure accuracy, tidiness and safety. 3.1 Photovoltaic Panel If photovoltaic panel is Crystalline Silicon, its manufacture and model must be approved by TISI 1843 or IEC 61215 Crystalline silicon terrestrial photovoltaic (PV) modules-design qualification and type approval. Two types of crystalline silicon are used in the industry; monocrystalline and multi (poly) crystalline. The main trend in crystalline silicon cell manufacture involves a move toward multicrystalline technology. Fig.3. Photovoltaic panel (a) Multicrystalline, (a) (b) (c) (b) Monocrystalline, and (c) Thin-film 2

Typically, efficiencies of monocrystalline and multicrystalline are around 15 and 12% respectively. If photovoltaic panel is Thin Film, its manufacture and model must be approved by TISI 2210 or IEC 61646 Thin-film terrestrial photovoltaic (PV) modules-design qualification and type approval. The efficiency of thin-film is around 6%. Fig. 3 shows three types of photovoltaic panel. 3.2 Grid Connected Inverter The grid connected inverter must have the following specifications: 3.2.1. Brand and model must be approved by IEC 61727 Photovoltaic (PV) systems Characteristics of the utility interface and IEC 62116 Test procedure of islanding prevention measures for utility-interconnected photovoltaic inverters or be a product with test report approving specifications according to IEC 61727 or IEC 62116; 3.2.2. There must be a copy of certificate of industrial standard as specified in 3.2.1 issued by Certification Body (CB) or a test report showing that specified qualifications are met where the test report must be issued by an accredited laboratory according to TISI 17025 or ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories; 3.2.3 Its electrical specification must be in accordance with the power distribution utility s Regulation on Specifications on Power Network Connection B.E. 2551 or other relevant regulations where test report, issued by testing unit approved by the power distribution utility, must be provided. 3.3 Control and Protection The control and protection of solar PV rooftop system is divided into two types as follows: 3.3.1 Direct Current Control Device 1) In case of safety switch, (a) the device must be of Fusible Type 1 Phase 2 Wires or other types with better qualifications; (b) the structure must be made of metal with cover protecting the switch when it stays at ON position; (3) the fuse must be DC fuse with rated current not less than 1.25 times of short circuit current (I SC ) at the Standard Test Condition (STC) of the photovoltaic panel; 2) In case of circuit breaker; (1) the device must be modeled case circuit breaker (MCCB); (2) the device must be a product according to IEC 898 or IEC 947-2 or other equivalent or better qualification; (3) the device must have Ampere trip, AT not less than 1.25 times of I SC at the STC of the photovoltaic panel. 3.3.2 Alternating Current Control Device 1) The device must be MCCB; 2) The device must be a product according to IEC 898 or IEC 947-2 or other equivalent or better qualification; 3) The device must have ampere trip, AT not less than 1.25 times of rated power at unity power factor of electrical inverter specified in 3.2. 4. Regulation on Grid Connection of MEA The solar PV rooftop system must be installed according to the regulation of MEA s grid connection which briefly describe in the following subsections. 4.1 Regulation for an Inverter Used in Grid Connection The inverter used in Solar PV Rooftop must have qualifications as required in the Requirements for an Inverter Used in Grid-connected Power Generating System and a report must be attached to show a test result that the inverter meets all requirements. This report must be published by an institute or unit that is impartial and certified ISO/IEC 17025 (for inverter) from a laboratory or inspected and approved by MEA. The technical requirement for inverter consists of power quality control and response to electrical system. 3

4.1.1 Power Quality Control 1) Harmonic When the inverter supplies electricity to the balanced linear load, it must not inject harmonic current to distribution network over the limitation shown in Table 4 (shows in the percentage compared to the inverter s current rating). Table 4 Limitation of harmonic current Odd order Current limit (%) Even order Current limit (%) 3-9 4.0 2-10 1.0 11-15 2.0 12-16 0.5 17-21 1.5 18-22 0.375 23-33 0.6 24-34 0.15 35 0.3 36 0.075 Total current harmonic distortion (THD i ) 5% 2) Voltage fluctuation of flicker The inverter must not cause voltage fluctuation or flicker over the limitation specified by IEC 61000-3-3 (2008) or IEC 61000-3-5 (2009) or IEC 61000-3-11 (2000) standards for the inverter with current rating not over 16 A or with current rating over 75 A or with current rating not over 75 A respectively. 3) DC injection The inverter must not inject direct current to distribution network more than 0.5% of the inverter s current rating. 4.1.2 Response to electrical system 1) Voltage range The inverter must disconnect from distribution network if the line-to-line or line-to-neutral voltage in the network differs from 346 416 V and 200 240 V respectively with the duration listed in Table 5. Table 5 Voltage ranges and duration Voltage range (V) Maximum time to disconnect Line-to-line Line-to-neutral (seconds) V < 199 V < 115 0.1 199 V < 346 115 V < 200 0.2 346 V 416 200 V 240 Continue to operate 416 V < 539 240 V < 311 2.0 V 539 V 311 0.05 2) Frequency range If the frequency of the network is out of range between 49 and 51 Hz, then the inverter must disconnect from distribution network within 0.1 second. 3) Islanding protection When islanding takes place, the inverter must discover and disconnect from distribution network within 2 seconds. 4) Response to utility recovery After the inverter is disconnected due to power interruption or out of ranges voltage/frequency and when the distribution network recovers, the inverter must delay the connection to the network for at least 2 minutes. 4.2 Limitation of Solar PV Rooftop System Capacity In order to control the impact from Solar PV Rooftop electric power generating system that may occur to voltage, power quality and reliability of distribution network, therefore, MEA defines the limitation of Solar PV Rooftop s total installed capacity that can connect to the network of MEA as follows: 4.2.1 Low-Voltage System (230/400 V) Connection 1) If it is a single phase electric power generating system, the installed capacity must not exceed 10 kw per applicant. 2) The total installed capacity of solar PV rooftop system (in kw) that connects to a distribution transformer of MEA must not exceed 15% of the distribution transformer s rating (in kva). 4

3) In case that the VSPP applicant still intends to sell electricity although the distribution transformer in that area already reaches the limitation of Solar PV Rooftop, the applicant can connect to sell electricity on 12 or 24 kv system. The applicant must provide and install the distribution transformer along with the protection equipment by MEA standard. 4.2.2 Medium-Voltage System (12 or 24 kv) Connection 1) The power generating system that has capacity (in kw) exceeding 15% of the distribution transformer s rating (in kva) in that area must connect to sell electricity on 12 or 24 kv system. The applicant must provide and install the distribution transformer along with the protection equipment by MEA standard. 2) The total installed capacity of a generator from every type of power producers (both Solar PV Rooftop and other power generators) that is installed in the same feeders must not exceed 8 MW and 4 MW per feeder for 24 kv and 12 kv systems respectively. 4.3 Energy Meter Installation The installation of energy meter for sell electricity at low- and medium-voltage system is shown in Fig. 4. Fig.4. Energy meter installation configurations 5. Economic Analysis The cost of solar PV rooftop system, operation & maintenance (O&M) cost, financial mechanism, FiT system of the solar PV rooftop system are analyzed to determine the financial parameters in term of simple payback period, net present value (NPV) and internal rate of return (IRR) from the solar PV rooftop system owner s perspective. The calculation of the financial parameters uses the following equations: Initial investment cost Payback period ( in year) = (1) Net annual cash flows n Ct Net present value = I t o (2) I + r t = 1 ( ) 5

n Ct Internal rate of return = Io = 0 (3) t = 1 t ( I + r) where C t is the net cash receipt at the end of year t, I o is the initial investment cost, r is the discount rate, and n is the project/investment's duration in years. In this paper, the economic evaluation of solar PV rooftop system investment for 5 kw residential is studied. The technical parameters are used to estimate initial cost of project, O&M and installed capacity requirement. Table 6 shows such technical parameters and cost assumption. It notes that cost of solar PV rooftop system includes cost of PV array, inverter, protection equipment and wire. Table 6 5 kw solar PV rooftop system: technical parameters and cost assumptions (1 USD = 32 THB) Parameter Unit Value Initial cost of solar PV rooftop system Baht/kW 60,000 100,000 Installed capacity requirement with 15% derating factor kw 5.75 Operating and maintenance cost Baht/year 5,000 Energy meter cost Baht 10,000 Feed-in tariff Baht/kW 6.96 Average electric energy generating per 1 kw kwh/kw/year 1,300 Discount rate percent 3 5 Project lifetime year 25 The NPV and IRR are evaluated as the function of discount rate is varied from 3 to 5 percent and initial cost of solar PV rooftop system is varied from 60,000 to 100,000 Baht/kW. The evaluation results of these financial parameters and simple payback period are shown in Table 7. Table 7 Economic evaluation results Cost of solar PV rooftop system (Baht/kW) Payback period (year) Discount rate 3% 4% 5% NPV IRR NPV IRR NPV IRR 60,000 8.82 65,815.03 7.16 32,323.95 6.13 3,190.91 5.12 70,000 10.25 11,053.12 5.32-22,437.96 4.13-51,570.99 3.31 80,000 11.68-43,708.78 3.86-77,199.86 2.86-106,332.90 1.88 90,000 13.11-98,470.69 2.66-131,961.77 1.67-161,094.80 0.70 100,000 14.54-153,232.59 1.64-186,723.67 0.67-215,856.71-0.29 The investment of this project should be done when the initial cost of solar PV rooftop system and discount rate are not more than 60,000 Baht/kW and 4 percent respectively. 6. Conclusion The solar PV rooftop program is implemented according to Renewable and Alternative Energy Development Plan for 25 percent in 10 years, or AEDP 2012-2021. MEA s quota for purchasing electric power from solar PV rooftop system is 80 MW. This paper describes the solar PV rooftop system including PV panel, grid connected inverter and control and protection equipment. The regulation on grid connection of solar PV rooftop system that installed in MEA s service area including regulation of an inverter, limitation of solar PV rooftop system capacity and energy meter installation is also presented. The economic analysis of solar PV rooftop system for residential is evaluated in order to suggest the investment to customers. Bibliography [1] The Renewable and Alternative Energy Development Plan for 25 Percent in 10 Years (AEDP 2012-2021). (www.dede.go.th/dede/images/stories/dede_aedp_2012_2021.pdf ). [2] The ERC rules and Regulation on Thailand s Solar Rooftop Program. (http://www.erc.or.th/ercweb2/front/staticpage/staticpage.aspx?p=200&tag=solarrooftop). 6