Bangladesh Metro7.96MWPhotovoltaic Construction

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Year 2025

Project Initiation Analysis

The proposed project location isthe warehouse workshop and stables in Uttara, Dhaka, Bangladesh (23°52′41″N, 90°21′30″E),with a roof area of 60,000m² for the workshop buildings and stables in the warehouse area. The planned photovoltaic capacity is 7.96MWp, with a net output of 6.52MW.

Basis for Project Approval

This project is based on the following relevant national policy provisions of Bangladesh:

The "Mujib Climate Prosperity Plan 2030" issued by Bangladesh in 2021 proposes the goal that "with the support of international and other investments, renewable energy will account for 30% of energy consumption by 2030, reach at least 40% by 2041, and achieve grid resilience and modernization."

In the "Bangladesh Vision Plan 2021-2041," the Bangladesh government has identified green energy as a key development area and set a strategic goal for renewable energy power generation capacity to account for 40% of energy supply.

“Draft Integrated Energy and Power Master Plan of Bangladesh”: By 2025, Bangladesh’s electricity demand is expected to reach 32,659 megawatts; by 2050, it will reach 84,858 megawatts. The government is committed to achieving 10% renewable energy by 2025 and 100% renewable energy by 2050.

Necessity Analysis

Bangladesh’s power sector infrastructure is insufficient, with a significant domestic electricity shortage, and its mineral resources such as coal are scarce. Currently, proven coal reserves are only about 402 million tons, with a daily coal production of about 3,000 tons, which greatly limits domestic traditional thermal power generation and creates an urgent demand for renewable energy generation. According to information from the Bangladesh Ministry of Energy on June 26, 2024, Bangladesh’s total installed renewable energy capacity is 1,373.81 megawatts, of which nearly 80% comes from solar energy, totaling 1,079.82 megawatts.

Electric PowerEnergy Structure Urgently Needs Optimization

As an emerging economy in South Asia, Bangladesh's electricity demand growth rate ranks among the highest globally, but its energy structure is still dominated by natural gas (55%), heavy oil (20%), and coal (15%), with renewable energy (solar, wind) accounting for less than 5%.The main reasons for the energy system transformation are the unreasonable power supply structure and high electricity costs. There is overcapacity in natural gas power generation units, but fuel supply cannot keep up; fuel oil power generation costs are high, and the development of clean energy such as wind and solar is slow, with a small share. Electricity demand has not met growth expectations, and the government must pay expensive capacity costs according to power purchase agreements. Meanwhile, many planned projects are progressing slowly. Ensuring energy security and a green, low-carbon power transition is key to improving Bangladesh's energy development, including diversifying fuel supply, efficiently utilizing existing power generation assets, reducing generation costs, lowering dependence on fossil fuels, and increasing the share of renewable energy.

Bangladesh Power Energy Structure Diagram

Huge Potential for Distributed Photovoltaic Development

Abundant Solar Resources:Bangladesh has abundant solar resources, with annual utilization hours reaching 2,500 hours, especially in the southern region where the average daily radiation intensity reaches up to 6.5 kWh, making its natural resources uniquely advantageous.

Figure Bangladesh Solar Radiation Intensity Map

Figure BangladeshSolar Energy ResourcesFigure

Bangladesh Dhaka Climate Data Table (1981-2010)

Unit: ℃, mm, hours

Tax exemption policy support:The Bangladeshi government attaches great importance to renewable energy power generation, actively promoting the construction of photovoltaic and wind power projects, providing new development opportunities for the photovoltaic industry. The Bangladeshi government has also extended the tax incentive policy for renewable energy enterprises (from 10 years to 15 years), offering 10 years of full tax exemption, 3 years of half tax reduction, and 2 years of 25% tax reduction for renewable energy power generation projects put into operation from July 1, 2025, to June 30, 2030.

Constraints on Centralized Photovoltaic Development: Land issues have become one of the main reasons why photovoltaic projects in Bangladesh have not been implemented. The Bangladeshi government stipulates that agricultural land cannot be used for photovoltaic power station construction. Additionally, since land in Bangladesh is privately owned, individual landowners hold relatively small land areas, which cannot meet the land requirements for photovoltaic project construction.

The total rooftop area in Bangladesh is 4.712 billion square meters.Assuming10% of the rooftop area (471 million square meters)is installed withrooftop photovoltaics, it can produce at least 46,644 megawatts of clean electricity.

Project Outcome Efficiency Analysis

Macro Level

Alleviating the tight electricity supply issue. Bangladesh’s power infrastructure construction is insufficient, with a significant domestic power shortage, scarce mineral resources such as coal, and limitations on traditional thermal power generation, creating an urgent demand for renewable energy power generation. Distributed photovoltaic power generation can increase power supply and alleviate the tight electricity supply problem.

Promote green development and reduce carbon emissions. Distributed photovoltaic power generation, as a clean energy source, produces no greenhouse gas emissions and can effectively reduce carbon emissions, playing an important role in combating global climate change.

Promoting economic development and creating job opportunities. The development of the photovoltaic industry not only drives the growth of related industrial chains but also creates a large number of jobs. Government support policies for the photovoltaic industry, such as tax incentives and investment encouragement, have attracted domestic and foreign investments, further promoting economic growth.

Aligning with the national green development strategy. The government of Bangladesh places great importance on renewable energy power generation, designating it as a key development area and setting a strategic goal for renewable energy power generation capacity to account for 40% of the energy supply. Distributed photovoltaic power generation projects align with the government's green development strategy and help achieve this goal.

Microscopic level

The MRT Line 6 is a new electrified metro system implemented by the Dhaka Mass Transit Company Limited (DMTCL). This system is part of the large-scale rapid transit system approved by the Dhaka Transport Coordination Authority (DTCA) within the 20-year Strategic Transport Plan (STP). Once completed, the public transit system is expected to promote economic and social development in the Greater Dhaka area.

Reducing energy consumption costs.The operation of rail transit requires a large amount of electrical energy. Traditional power supply methods often rely on the power grid, which is not only costly but also faces sustainability challenges in today's increasingly tight energy environment. The emergence of photovoltaics provides a new energy solution for rail transit.

Reducing carbon emissions.Rail transit itself is a relatively low-carbon mode of travel, but it still produces some carbon emissions during operation. Photovoltaics, as a clean energy source, generate almost no carbon emissions during electricity production.

Enhancing the reliability of energy supply.By installing distributed photovoltaic power stations in the region, even if the power grid fails, the photovoltaic power generation system can still provide power support for critical rail transit equipment, ensuring the basic operation of trains and emergency lighting functions at stations.This greatly improves the reliability and stability of the energy supply for rail transit.

As a green demonstration case of the "Rail Transit + Photovoltaics" project, the metro photovoltaic power generation project can provide experience and model references for other industry sectors, promoting the application of distributed photovoltaic power generation projects,andthe project will become a flagship project for public utilities in nationalconstruction.

Construction Concept

Distributed photovoltaic power generation with an installed capacity of 7.96MW is planned on the total 60,000m² roof area of the warehouse workshop and stable of MRT Line 6 in Uttara, Dhaka, Bangladesh. A total of 1,2240 pieces of 650Wp monocrystalline silicon panels will be laid, connected in series with 30 modules per string, and 408 strings connected in parallel. The installation will use Building Attached Photovoltaic (BAPV) method, with the silicon panels tilted at an angle of 20 degrees. The system will be equipped with 23 inverters, which connect to box-type transformers. The transformers are rated at 0.8/35 kV with a capacity of 6500 kVA, and connect to the plant station’s 132/33 kV main transformer to complete grid connection. Energy exchange with the grid will be conducted via net energy metering. Excess electricity generated after self-consumption will be fed into the grid. The net exported electricity can be credited to offset any consumption in the next rolling period or can be paid at a specific rate determined by the utility company/agency at the end of the settlement period.

System Architecture

Technical Solution

7.96 MW photovoltaic reference for the warehouse workshop and stable roof of MRT Line 6 in Uttara, Dhaka, Bangladesh, according to the "Net Energy Metering Guide". The main equipment includes photovoltaic modules, inverters, transformers, etc.

Equipment Selection

Selection of Photovoltaic Modules

The main types of solar photovoltaic cells include: crystalline silicon cells (including monocrystalline silicon Mono-Si, polycrystalline silicon Multi-Si, ribbon/sheet silicon Ribbon/Sheet-Si), amorphous silicon cells (a-Si), and non-silicon photovoltaic cells (including copper indium selenide CIS, cadmium telluride CdTe).

Most of the solar photovoltaic cells currently produced and used in the market are made from crystalline silicon materials. From an industry perspective, solar photovoltaic cells can be divided into silicon-based cells and non-silicon cells. Silicon-based cells, with better cost performance and mature technology, occupythe vast majority of the market share.

Economic comparison between polycrystalline silicon cells and monocrystalline silicon cells: According to the current market situation, the unit price of monocrystalline silicon cell modules is almost equal to that of polycrystalline silicon cell modules, while monocrystalline silicon modules have obvious advantages in photovoltaic sites with limited space. Considering all the above factors comprehensively, this project recommends the use of monocrystalline silicon photovoltaic modules.

Photovoltaic cell modules are the core components of solar photovoltaic power generation systems. Their photoelectric conversion efficiency and various parameter indicators directly represent the power generation performance of the entire photovoltaic power generation system. The parameters characterizing the performance of solar cell modules include peak power under standard test conditions, optimal operating current, optimal operating voltage, short-circuit current, open-circuit voltage, maximum system voltage, module efficiency, short-circuit current temperature coefficient, open-circuit voltage temperature coefficient, peak power temperature coefficient, output power tolerance, etc. There are many power specifications for solar cell modules, but when selecting, the main consideration is generally modules with high individual power and commercial application. Modules with high individual power require fewer modules for a photovoltaic power station of a certain capacity, fewer connection points between modules, reduced failure probability, lower contact resistance, less cable usage, reduced overall system loss, and less maintenance and inspection work for the panels later on.small.

Taking into comprehensive consideration the project construction layout, installed capacity, usable building area, market supply capacity, and the performance stability and reliability of actual commercial applications, this project plans to useTrina Solarhigh-efficiency monocrystalline single-sided modules with an individual power of650Wp,model TSM-DEG21C.20-650Wp,with the main module parameters shown in the followingfigure.

Inverter Selection

Common types of inverter structures are as follows:

1) Centralized Inverter:Centralized inverters are currently the widely used power conversion devices in large-scale photovoltaic power plants and are among the most mature technical solutions. Centralized inverters typically use a single maximum power point tracking (MPPT) input, centralized MPPT optimization, and centralized inverter output. After large-scale series and parallel connections of photovoltaic module arrays, they are connected to high-capacity centralized inverters for "DC to AC" conversion and then integrated into the grid. Since centralized inverters are installed in a centralized manner, installation is relatively simple and maintenance is more convenient. Additionally, they use a single-stage control method, which is relatively simple to control, with mature related technologies and low unit system cost. As the development and operation of photovoltaic power plants enter a refined stage, photovoltaic power generation systems using centralized photovoltaic inverters have also revealed some drawbacks. Because a single centralized inverter usually only has one MPPT channel, it cannot precisely track and control each photovoltaic string due to mismatch deviations among photovoltaic modules (such as differences in panel parameters, inconsistent degradation characteristics, varying degrees of surface dust shading, different shading conditions at different times, differences in panel tilt and orientation, issues caused by power plant design and construction quality, etc.). Therefore, this scheme’s mismatch losses reduce the power generation capacity of some panels, resulting in decreased system power output.

2) String Inverter:String inverters were originally designed for small photovoltaic power systems such as rooftop PV and can be directly connected to low-voltage grids without the need for isolation transformers or step-up transformers, making them especially suitable for low-voltage grid-connected distributed photovoltaic power generation. String inverters optimize MPPT in a decentralized manner for sub-arrays of photovoltaic modules, then the AC outputs are combined in parallel and centrally stepped up for grid connection, effectively addressing the power loss caused by photovoltaic module "mismatch" in large-scale photovoltaic power plants.

3) Distributed Inverter:In a distributed photovoltaic inverter system, each photovoltaic module sub-array is processed through an MPPT optimization unit, outputting DC, which is then connected in parallel via a DC bus and converted to AC by a single centralized inverter before being stepped up and connected to the grid. The distributed inverter system performs decentralized optimization for each photovoltaic module sub-array, effectively solving the "mismatch" losses between photovoltaic strings. Distributed photovoltaic inverters represent an innovative technical solution in photovoltaic power generation technology development. Compared with centralized and string inverters, they unify "decentralized MPPT tracking" and "centralized inverter grid connection," providing a clear system solution that is relatively simple to implement. This approach addresses the string "mismatch" loss problem found in centralized inverters and avoids the high system costs and grid oscillation risks caused by AC parallel connections faced by string inverters.

According to the layout capacity and slope of the roof components in this project, considering that the string inverter adopts a modular design with maximum power tracking function on the DC side and parallel grid connection on the AC side, its advantage is that it is not affected by differences between string modules and shading, while also reducing the mismatch between the optimal operating point of the photovoltaic modules and the inverter, thereby maximizing power generation. Therefore, this planned project intends to adopt a string inverter design scheme. According toproject analysis, this project usesHuawei300kWstring inverters,modelSUN2000-300KTL-H0,the detailed parameters are shown in the figure below.

Transformer Selection

Power transformers are typically used in transmission networks to increase or decrease AC voltage levels. In this project, a containerized prefabricated substation is configured and connected to the on-site 132/33 kV main transformer. A 0.8/35 kV transformer with a capacity of6500 kVA is required to step up the voltage. The prefabricated substation integrates RMU, CT, PT, circuit breakers, lightning arresters, relay protection devices, UPS, etc., which will relatively ensure a shorter overall delivery time and minimal on-site work.

Construction Plan

Installed solarmodulespower650Wp total12240pieces,module modelTSM-DEG21C.20-650Wp,total installed capacity is 7956kWp, net output capacity is 6524kW.Roof 1 is expected to have 7050 photovoltaic modules installed, with an expected installed capacity of 4582.5kW; Roof 2 is expected to have 5190 photovoltaic modules installed, with an expected installed capacity of 3373.5kW,the overall layoutis shown in the figure below

Photovoltaic modulesuse trapezoidal plates, as shown in the figure below.

Photovoltaic modulesare installed in a horizontal layout, with 30 modules connected in series,and 408 modules connected in parallel,the photovoltaic modules are installed at a 20-degree tilt angle,the typical array layout is shown in the figure below.

Photovoltaicmodule strings are connected through combiner boxestoinverters, the inverters connect to the grid connection point at a 0.8kV/35kV transformer, which connects via the transformer to the132/33kV substation, completing the grid connection, the electrical drawings are as follows:

Construction Results

After the photovoltaic systemis builtthe total electricity generated over 25 years234,441,000kWh, net electricity cost savings14,090,589.06USD (construction and operation & maintenance costs not yet considered),with a carbon factor of 0.785, the total carbon emission reduction is184,036.19tons, the average annual electricity generation is9,377,640kWh, the average annual net electricity cost savings are563,623.56USD, and the average annual carbon emission reduction is7,361.45tons.

The detailed calculation process is as follows:

Photovoltaic operation simulated using pvsyst software, after checkingthe warehouse workshop and stable in Uttara, Dhaka, Bangladesh (23°52′41″N, 90°21′30″E)the annual total horizontal irradiation for photovoltaics is 1496.7 kWh/m2^/yr.

Figure Project photovoltaic annual total horizontal plane radiation

Photovoltaic Array System Efficiency Calculation:

(1) Photovoltaic Temperature Factor The efficiency of photovoltaic modules varies with their operating temperature. When their temperature rises, the efficiency of most types of photovoltaic cells tends to decrease. The derating factor is taken as 97%.

(2) Dust loss of the photovoltaic array is caused by pollution from dust or water accumulation on the photovoltaic modules. Statistics show that modules frequently washed by rain have an average impact between 2% and 4%,while modules not washed by rain and thus dirtier have an average impact between 8% and 10%. This project comprehensively considers a derating factor of 3%, i.e., a pollution derating factor of 97%.

(3) Average Efficiency of Inverter The current average efficiency of grid-connected photovoltaic inverters is about 98.4%.

(4) Preliminary estimation of energy losses such as electricity consumption and line loss within the photovoltaic power station shows that the AC and DC distribution loss of the photovoltaic array is about 4.5%. The comprehensive distribution loss coefficient is 95.5%.

(5) Although the failure rate of photovoltaic modules is extremely low, periodic maintenance and grid faults still cause certain losses. The loss coefficient is taken as 1%, resulting in a utilization rate of 99% for the photovoltaic power generation system.

(6) Photovoltaic module differential loss is 3%, with a utilization rate of 97%.

(7) Radiation loss during early morning and evening when not usable is 3%, with a utilization rate of 97%.

Considering all the above reduction factors, the overall efficiency of the monocrystalline silicon photovoltaic module array system is 82%.

Create the project and import the meteorological data. The optimal tilt angle of the photovoltaic module is 20 degrees. Select the Trina photovoltaic module model Trina_TSM_DEG21C_20_650Wp.PAN (650 Wp) with 1,2240 units, Huawei inverter Huawei_Sun2000_300KTL_H0.0ND (300 kWac) with 23 units. Project information is shown in the figure.

Figure Photovoltaic Project Matrix Information

Simulation results show the system generates 10260 MWh/year, with an annual unit power generation of 1290 kWh/kWp/yr, and a system efficiency of 0.82.

Figure Photovoltaic Simulation Results

Using a first-year power degradation rate of 2%, and a decrease of 0.55% from the second year to the twenty-fifth year, the utility electricity price is calculated at 8 BDT, equivalent to 0.066 USD.

Photovoltaic Annual Power Generation Revenue Table

Unit: kWh, USD

Total photovoltaic electricity generation over 25 years234441000kWh, net electricity cost savings14090589.06USD.

Construction List