Solar Radiation and Solar Programs Training Consulting Engineering Publications
SOLAR RADIATION
Purposes of Solar Radiation Software Successful project planning and solar plant implementation starts by determining the solar radiation of a location. Assessing site solar radiation includes: Quantifying the solar resource Producing the solar resource data if there is none available Performing statistical analysis of the data if possible to verify accuracy Usage of solar radiation software to simulate PV performance throughout the year. This will then produce the following: 1. Amount of energy (kwh, MWh) produced by the PV installation per anum 2. Savings generated or income produced 3. Assist in determining the economical feasibility of the installation
Solar Radiation Resource: Weather One of the most important considerations for the siting of a solar plant is the level and variability of solar irradiation at the site. Naturally, areas with consistently high levels of irradiation are favourable and give higher yield and performance. Ideal locations will have long daylight hours, minimal cloud cover and have little risk of shading/soiling from snow or dust. Tropical areas close to the equator tend to have a better solar resource in the dry season, with longer days and clearer skies. However, during the rainy season there is frequent cloud cover, which can substantially reduce energy output of the system. Areas close to the poles tend to have very poor output during winter because of the minimal daylight hours and soiling from snow cover, but these areas will have a much higher output during the summer months.
Solar Radiation Resource: Weather Rainfall and cloud cover Although some rainfall can be an advantage for solar plants because it acts as a cleaning mechanism, too much rainfall can reduce the overall performance because it means increased cloud cover or flooding in extreme cases. It is therefore important to assess the volume and frequency of rainfall and/or cloud cover at the prospective site. A high degree of cloud cover coupled with unfavourable topography at the site can mean that the chances of flooding are high.
Solar Radiation Resource: Weather Temperature It can also be important to establish accurate temperature data for the site in order to predict the system performance. Higher temperatures usually affect the solar system s power output and therefore the system s performance. Temperature data is required to determine the system s maximum and minimum array voltages, and this information is in turn required for sizing inverters. Source: NASA
Solar Radiation Resource: Data Two main types of radiation data are collected: Irradiation The amount of energy from the sun that is collected over a flat surface. Unit: kwh/m 2 or kj/m 2 Irradiance The amount of power from the radiation from the sun that arrives on a flat surface. Unit: kw/m 2 Note that the radiation data is from the perspective of a flat, horizontal surface. Having the modules inclined at an angle will change the relative amount of solar radiation received by the PV modules throughout the day as the sun moves across the sky. Source: Christian Pinatel de Salvator
Solar Irradiation Data A world map of long-term average global horizontal irradiation is shown below. Although this kind of map is useful for recognising areas of high irradiation on average, it does not show seasonal, daily or inter-annual variation, which is necessary in order to quantify the uncertainty in revenue from the solar plant in any given year. Source: Solar GIS
Solar Irradiation Data In order to accurately assess the solar resource, it is important to have accurate solar resource data for the site. Global horizontal irradiation is the sum of direct and diffuse radiation and is the most useful parameter for evaluating the solar resource at a given site. Note that the data will not account for extreme variations of weather, such as El Niño/La Niña and tropical hurricanes or cyclones. Existing long-term data is available from ground-based weather stations and satellitederived data sets. Some examples are given below: NASA Surface Meteorology and Solar Energy Data Set (for all locations) http://eosweb.larc.nasa.gov/sse/ The Australian Solar Radiation Data Handbook Exemplary Energy http://www.exemplary.com.au/solar_climate_data/asrdh.php The Australian Government Bureau of Meteorology http://www.bom.gov.au/climate/data/ PVGIS EU Joint Research Centre (for Europe and Africa) http://re.jrc.ec.europa.eu/pvgis/ NREL monthly average and annual average daily total solar resource data (for USA) http://www.nrel.gov/gis/data_solar.html
Solar Irradiation Data For the highest accuracy, a land-based sensor such as a thermal pyranometer should be installed at the site to measure data for at least 12 months (ensuring seasonal variation is captured). This ground-measured data can then be calibrated against pre-existing data sets to get a more accurate estimation of annual solar radiation. Source: NREL
Measuring Shading Using onsite solar radiation measurements will account for any reduction in solar access due to natural landscape, such as a valley that cuts out the sun in the early morning and late afternoon. There are various tools that can be used to conduct a full solar access and shading analysis throughout the year. For example Solar Pathfinder projects the sky image onto a latitude-range specific Sunpath diagram to measure any objects that may shade the array at any time of the year. The Solar Pathfinder is a low tech way of approximating the shade scene. Another tool used is the Solmetric SunEye which is a digital handheld tool which calculates predicted loss due to shade.
Australian Solar Irradiation Handbook
Solar Radiation Resource: Types of data- ASRDH
SOLAR PROGRAMS
Software & Data Handling Besides ensuring that the solar radiation data itself is reliable and trustworthy, it is important to have a useful and functional solar radiation software. There are many options available of either free or paid software packages. With the following implications: Free software will likely not be as complete, stable, or capable compared to paid software. In some cases, paid software would be more reliable. Paid software can be expensive, and could have recurring costs There may be trial or demo versions of paid software that have set limitations Paid software tends to have a better support options (help, forums, hotline, etc.) Free software may be limited to one operative system (OS), such as Windows. The following sections introduce and describe several available free or paid software programs to perform analysis of solar radiation and system performance. Source: Precision Solar Technologies
ARENA
PVSyst PVSyst is a software package designed for photovoltaic installations. Very useful for data science. Very popular program. Can produce high resolution data analysis of PV performance Handles and imports meteorological data from many online databases and can manipulate such data Contains specifications for many solar panel and inverter manufacturers Produces reports and graphics with great detail Requires a moderate to elevated understanding of solar radiation concepts as well as data processing and statistics for detailed analysis Expensive Source: PVSyst pvsyst.com
PVSyst Weather data for locations around the world Array tilt and effect on irradiation simulation Source: PVSyst pvsyst.com
System Advisor Model (SAM) The System Advisor Model is a performance and financial model software package for renewable energy installations. Developed by the National Renewable Energy Laboratory (NREL), its focus is on grid-connected projects. Provides useful performance and cost of energy estimates Can import weather files and has its own database Produces very useful charts and graphs Can be used for scenarios involving PPA s Can implement time-sensitive interval analysis Tricky to modify tariff data and timesensitive costs since it assumes US tariff structures and tax incentives by default Free. Source: NREL (sam.nrel.gov)
System Advisor Model (SAM) Cash flow analysis for a wind farm project Performance of a PV system with battery storage Source: NREL (sam.nrel.gov)
HOMER Pro HOMER Pro by HOMER Energy is a powerful microgrid designing tool for installations involving off-grid PV systems, generators, wind turbines, and more. Performs simulations for possible combinations of equipment Financial and economic analysis High granularity in data analysis Provides sensitivity analysis of a system on-the-go Modular software: modelling packs can be installed for specific systems: biomass, hydro, hydrogen, thermal, energy storage etc. Industry leading software Twenty one day trial, then fees apply Source: Homer PRO (homerenergy.com)
HOMER Pro System optimization for multiple configurations Thermal load model for scenarios involving heating Source: Homer PRO (homerenergy.com)
RETScreen RETScreen is a multi-purpose clean energy management software developed by Natural Resources Canada. For renewable energy and energy efficiency projects Economical, technical, and financial analysis of projects Integrates weather databases from around the world Complex but highly versatile (includes extensive manual) World renowned and recognized Free but requires purchase for full version The program landing screen showing the process flow in the center of the screen
Screenshots from the RETScreen program, showing the detailed information that can be obtained for a sample site in Montreal
FreeGreenius FreeGreenius is a performance calculation tool for concentrated solar power and other renewable energy systems involving solar thermal. Developed by the German Aerospace Center. Implements solar thermal processes including concentrated solar power, solar towers, solar heating and solar cooling Can import third party meteorological data and produce high resolution results Calculation of cash flows for economical and financial analysis Free full version available Source: FreeGreenius freegreenius.dlr.de
Source: FreeGreenius freegreenius.dlr.de
Meteonorm Meteonorm is an advanced solar radiation data suite developed by Meteotest that can generate accurate weather data for locations around the world. Industry standard Reliable and accurate data for typical year weather data from a large global database Database from satellite and ground weather stations Produces high resolution analysis Can simulate extreme weather and climate change IPCC scenarios Can import third party data for processing Source: Meteotest (meteonorm.com)
Meteonorm Meteonorm can produce high resolution data while also giving the user advanced options to obtain reliable results that can be implemented in other programs such as PVSyst or Homer PRO. Source: Meteotest (meteonorm.com)
Web based platforms The following lists several online web-based platforms for solar radiation analysis. There are many available for free. Some may be restricted to certain geographical areas, while others may require a stable internet connection or a more capable computer. They should be for guidance or quick calculations only since they are susceptible to higher degrees of error than standalone software. Google Project Sunroof (USA only) APVI Solar Map (Aus only) PVWatts Calculator There are many different variants of these online, but they often lack the degree of customization and detail that standalone software tends to have. The data and reports they generate are usually very simple and often make many assumptions that may not be evident to the user.
Notes Not all programs are perfect, but all will provide to a certain degree the ability to enable the user to verify the suitability and feasibility of a renewable energy project.