Getting Started with PVSyst in Japanese: An Introduction to Solar Power Planning for Municipalities

Introduction: Why municipalities need solar power plans now

Against the backdrop of climate change measures and rising energy prices, promoting renewable energy has become an urgent task for municipalities as well. Aiming for carbon neutrality by 2050 (net zero greenhouse gas emissions), the Japanese government has set a target to supply roughly 40% of the power mix from renewable energy by 2030. Accelerating the adoption of solar power across the country is indispensable to achieve that goal. In fact, in 2024 the Ministry of the Environment set installation targets (in kW) by facility type for solar panels on facilities owned by local governments to strengthen these efforts. Some municipalities have also begun moves to make solar panel installation mandatory on new buildings. For example, from April 2025 Tokyo will require major housing developers to install panels on new homes, and similar ordinances are planned in other areas such as Kawasaki and Sagamihara. In this context, municipalities themselves are expected to take the lead in formulating and implementing plans to install solar power systems on public facilities and to lead local decarbonization.

Furthermore, installing solar power at public facilities can reduce costs through local production and consumption of energy and enhance resilience during disasters. If schools or municipal offices install solar systems with batteries, they can secure emergency power during outages and strengthen their function as disaster response hubs. For municipalities, solar power planning is an important measure that can bring benefits not only in meeting environmental goals but also in fiscal and disaster-preparedness terms.

Overview of PVsyst and the significance of learning via "PVsyst in Japanese"

Tools that can simulate generation forecasts and system design are indispensable when planning solar power systems. A leading example is PVsyst. PVsyst is a professional solar power simulation software developed in Switzerland and used by designers and engineers worldwide:contentReference[oaicite:0]{index=0}. By inputting panel and inverter specifications, local meteorological data, shading conditions, and more, it can calculate annual energy production, loss breakdowns, and performance indicators (PR) in detail. It is useful across a wide range of cases from large-scale mega-solar to school rooftop installations, and is powerful for visualizing and optimizing solar power plans.

However, because PVsyst has traditionally been provided in English, some municipal staff and technicians in Japan have found it challenging. This is where "PVsyst in Japanese" becomes notable. Fortunately, recent versions allow users to switch the software menus and screen displays to Japanese:contentReference[oaicite:1]{index=1}. In addition, materials that explain PVsyst simulation reports and terminology in Japanese have appeared. For example, guides to interpreting simulation reports in Japanese and glossaries of key technical terms are being prepared. These Japanese-language learning supports make PVsyst more accessible to those less comfortable with English and help build in-house capacity within municipalities. By using PVsyst that can be learned in Japanese, staff can run generation simulations themselves and reflect the results in planning, improving plan accuracy and reducing reliance on external parties.

Key terms used in PVsyst and their Japanese translations

Understanding technical terms is essential to master PVsyst. Below are explanations of frequently appearing terms in the software and reports, accompanied by their Japanese translations.

• Solar panel / module: The panels used for solar power generation. In English, PV module or panel. The generation capacity per panel is typically a few hundred watts, and a system is built by combining multiple panels.

• Inverter (power conditioner): A device that converts direct current (DC) to alternating current (AC). Since electricity from PV is DC, it must be converted to AC for use in homes and facilities, and any surplus can be exported to the grid. It is sometimes abbreviated as “power-con” (パワコン).

• Rated output (kW) and energy generation (kWh): Rated output (system capacity) is the maximum output the system can produce, measured in kilowatts (kW). Energy generation is the actual energy produced, measured in kilowatt-hours (kWh). For example, even a 10 kW system will produce varying energy amounts depending on sunlight conditions; on sunny days it might generate around 50 kWh in a day.

• Irradiation: Refers to the total amount of solar energy. It is the accumulated solar radiation at a location, typically expressed in units such as kWh/m². It is related to irradiance, but that term refers to instantaneous irradiance (W/m²). PVsyst uses annual and monthly average irradiation as meteorological input data as the basis for generation calculations.

• Azimuth: The direction a panel faces, expressed as an angle. In PVsyst, for the Northern Hemisphere, true south is 0°, west is positive, and east is negative:contentReference[oaicite:2]{index=2}. In Japan, panels are generally south-facing, but roofs may face east or west; in such cases, generation is somewhat lower than south-facing installations.

• Tilt: The installation angle of the panel relative to the horizontal plane. 0° is horizontal (flat), and 90° is vertical. In Japan’s latitudes, a tilt of about 30–35° is said to maximize annual generation. However, roof shapes and structural constraints often prevent achieving the optimal angle, so PVsyst is used to examine generation changes with different tilt angles.

• Shading: Shadows caused by surrounding buildings, trees, or terrain. Shadows on solar panels significantly reduce output, so understanding shading at the installation site is crucial. PVsyst allows settings for near shading (from nearby objects) and distant horizon shading (terrain blocking sunlight), and can simulate losses due to shading.

• Losses: A collective term for factors that reduce actual generation from the theoretical maximum. Examples include efficiency reductions due to panel temperature rise (temperature losses), losses in wiring and transformers, and losses due to soiling or aging of panels. PVsyst outputs a “loss breakdown” diagram in simulation results that quantifies losses at each stage from incident light to final output.

• Performance Ratio (PR): Short for Performance Ratio, a quality indicator for a plant. It shows how much of the energy expected under ideal conditions is actually obtained:contentReference[oaicite:3]{index=3}. For example, a PR of 80% means the plant yields 80% of the ideal energy. The fewer the losses, the higher the PR; for typical outdoor PV systems, PR values are usually around 70–85%.

Points to note when designing solar power systems for public facilities and communities

When municipalities design solar power systems for schools, municipal buildings, idle land, and other sites, they need to pay attention to the following points.

1. Plan to minimize shading impacts: As mentioned earlier, shading on panels significantly reduces generation. Therefore, it is important to survey shading conditions on site in advance and design layouts accordingly. On rooftops, shadows can be caused by outdoor AC units or elevated water tanks; on idle land, surrounding trees or structures may cast shadows. If necessary, consider removing or trimming obstacles or adjusting panel spacing. PVsyst’s 3D simulation feature can visualize seasonal and diurnal shadow movement, helping design layouts that minimize shading impacts.

2. Optimize azimuth and tilt: In Japan, south-facing panels at an appropriate tilt are the norm, but site conditions may impose constraints. If a roof faces east-west, panels will be installed facing east or west accordingly. In that case, generation near midday is lower compared to south-facing panels, but morning and evening solar energy can still be effectively utilized. Regarding tilt, installing panels to match roof slope often deviates from the optimal angle. While flat roofs can use mounting structures to set the tilt, excessive tilt increases wind loads and construction costs. It is advisable to use PVsyst to test various tilt and orientation patterns and balance generation, structural safety, and costs.

3. Adapt to local weather conditions: Local climate characteristics should be considered. Irradiation varies greatly by region, with differences between Pacific coast and Sea of Japan sides and by latitude affecting annual generation. PVsyst can import meteorological data for various locations (e.g., NEDO regional irradiation data), so always use data that match the site. In snowy regions, measures against generation loss due to snow are important. For areas prone to heavy snowfall, steeper tilts to shed snow or plans for snow removal may be necessary. In salt-damaged or typhoon-prone regions, select weather-resistant equipment and robust mounting methods appropriate to local environmental risks.

4. Regulations and safety: Installing solar systems on public facilities requires compliance with various regulations and ensuring safety. This includes filings for structures under the Building Standards Act, compliance checks for electrical equipment technical standards, and waterproofing and load-bearing checks for rooftop installations. For schools, ensure evacuation routes remain clear and take measures against falling objects. Identifying such constraints during the planning stage and consulting with relevant departments and experts helps prevent problems during construction.

Tips to improve generation simulation and design accuracy

To increase the accuracy of solar power planning, careful planning using simulations is essential. The following points help improve the precision of generation forecasts.

• Choose appropriate meteorological data: Simulation results are heavily influenced by the irradiation data used as input. Select reliable data sources and use meteorological conditions that closely reflect the site. In Japan, data from NEDO or the Japan Meteorological Agency and, internationally, satellite-based global datasets are used. Since estimates of irradiation differ across datasets, it is advisable to run simulations with multiple datasets where possible and compare differences.

• Detailed shading simulation: To accurately estimate shading effects, create and verify a 3D model of the site. By inputting buildings and trees into PVsyst’s 3D editor and reproducing seasonal shading, you can account for partial shading in mornings and evenings that simple calculations might miss. If possible, create precise models using drone photogrammetry or laser scanning, but if that is difficult, supplement with site photos and a sun chart.

• Set loss coefficients appropriately: PVsyst allows customization of various loss parameters such as voltage drop losses from wiring resistance, panel temperature characteristics, and soiling rates. Set realistic values based on manufacturer datasheets and past performance. Temperature-related output loss particularly affects summer generation, so set temperature coefficients according to installation environment. Fine-tuning settings reduces discrepancies between planned and actual operation.

• Compare multiple scenarios: In the early design stage, run simulations for several patterns to account for uncertainties. For example, create scenarios like “south-facing 15° tilt,” “south-facing 30° tilt,” and “east-west 5° tilt,” and compare generation and construction difficulty for each. Also, plan with margins in mind to account for future panel degradation or irradiation changes due to climate change as a risk management measure.

• Compare with measured data: If possible, obtain generation records from existing solar installations or short-term on-site pyranometer measurements and compare them with simulation results. If simulation values approximate local measured data, the simulation settings are likely reliable. If large discrepancies arise, recheck input data and parameter settings. Using on-site data in this way can further improve design accuracy.

From design to construction: the municipality’s role and process

When a municipality implements a solar power project itself, many steps are involved from planning to construction and operation. The main flow and the municipality’s role are summarized below.

• Feasibility study and target setting: First, survey the possibility of solar installation on municipal facilities such as government buildings and schools, or on suitable sites within the area. Identify roof area, orientation, sunlight conditions, and electricity usage to estimate scale. At the same time, set municipal renewable energy adoption targets (e.g., install XX kW on public facilities by 2030) to determine the plan’s direction.

• Preliminary design and generation simulation: For candidate sites, use PVsyst or similar tools to estimate generation and benefits. Simulation results showing how many kWh per year would be generated by installing X kW on which facilities and how much energy costs would be reduced are essential for deciding whether to proceed. Rough estimates of installation costs and financial projections are also prepared at this stage to evaluate return on investment.

• Budget securing and stakeholder coordination: If simulations indicate benefits, secure funding next. Utilize national subsidies or grants or coordinate budget allocation within the municipality. Approvals from the municipal assembly may be required. At the same time, coordinate with stakeholders such as the board of education or school principals when installing on schools, and explain plans to local residents to obtain their understanding and cooperation. If upfront municipal funding is difficult, consider third-party ownership models (PPA) where private companies install and own the equipment and the municipality pays for the electricity usage, enabling zero initial cost installations. The Ministry of the Environment supports PPA adoption for public facilities and has published guidance.

• Detailed design and procurement: Once funds are secured, move to the detailed design phase. Select specialized design offices and contractors (via bidding if required), conduct detailed surveys and structural checks, and finalize system designs. When panel layout drawings, wiring routes, equipment specifications, and construction schedules are finalized, execute the construction contract. As the client, the municipality should check that the design meets the original project objectives and issue correction instructions as needed.

• Construction management and inspections: During construction, monitor progress with attention to safety and quality control. Municipal staff should regularly inspect the site and hold meetings with the contractor. At completion, perform prescribed inspections to confirm that construction was carried out according to the design and that the generation system operates correctly. Grid interconnection procedures with the power company should also be completed at this stage in preparation for commissioning.

• Operation start and monitoring: After commissioning, carry out generation monitoring and regular inspections and maintenance. Track generation performance and verify any deviations from simulations to feed back into future planning improvements. The generated electricity not only contributes to facility energy savings but can also be used as educational material for local environmental learning or incorporated into emergency power drills, expanding the project’s post-installation benefits.

As described above, municipality-led solar projects require integrated management from planning through construction and operation. While specialized knowledge is needed at each stage, using simulation tools like PVsyst and relevant guidelines will help ensure steady progress and success.

Conclusion: Bridging planning and construction with simplified surveying using LRTK

To reliably realize solar power plans, it is important to bridge planning and on-site construction smoothly. A helpful tool for this is simplified surveying technologies that leverage the latest technology. For example, LRTK is a solution that enables high-precision surveying using a smartphone, allowing quick acquisition of detailed site dimensions and coordinates without specialized equipment. Incorporating LRTK survey data at the planning stage lets you refine PVsyst designs to better match actual site conditions. Conversely, during construction, using LRTK for layout marking based on design data helps align drawings and field work without discrepancies.

By using simplified surveying with LRTK, municipalities can manage the entire flow from solar planning to construction more seamlessly. Linking thorough planning through simulation with precise on-site data improves the accuracy of generation and construction time forecasts and leads to projects with fewer issues. Be sure to incorporate new technologies like LRTK from the planning stage to help municipal-led solar power projects succeed.