Solar Panel Calculations Featured

Written by Bayliner Owners Club
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As solar panel use increases in marine use, navigating (see what I did there) ? which panels to use and how much energy you can expect from a panels can be confusing. The tool in the link at the bottom of this page is designed to help calculate how much energy you can get from your panel(s) wherever you boat in the world.
To calculate your boat’s daily 12-volt needs, and therefore the size panel you need, multiply the average time each onboard appliance is used (in hours) times its amperage rating. Choose solar capacity based on your battery amp-hour rating—for example, if you have 400 amp-hour batteries, choose a 350-watt panel. Vessel Energy Use Calculator.
Volts x Amperes = Watts Watts x Hours of Use = Watt-hours
We cannot overemphasize the importance of putting together the most accurate information. you can. Without it you are only guessing.
Load Evaluation Form
Solar Array Sizing. Use this example to determine your solar module requirements. We have included an example column and a column for your system.
Solar Array Sizing
 
The chart below shows examples of energy consumption of various equipment. The current (amps) is multiplied times the amount of hours per day is used to determine the Amp Hours per day of energy that is consumed. These values are based on a 12 V DC nominal system.
If selected items in the above charts do not match to your usage, make up you own chart similar to above, calculate the amp-hrs per day for each item you use on board, then just total the items and you will know your daily amp-hour demand
 

Getting started with PVGIS

What is PVGIS?

PVGIS is a website that gives you information about solar radiation and PhotoVoltaic (PV) system performance. You can use PVGIS to calculate how much energy you can get from different kinds of PV systems at nearly any place in the world.
This page is meant to give you an introduction to using PVGIS. There is a lot more information about PVGIS, for instance go here to learn more about how PVGIS calculations are made.

PVGIS, first look

The PVGIS web interface looks like this:
Figure 1. PVGIS interface when you first access the web application, before doing anything.
 
There are many options in PVGIS, and for most of them you can get help by clicking on the text of the option. For instance, if you click on the text "Lat/Lon" below the map, you will get a help text on that topic (see Figure 2).
Figure 2. Example of help text in PVGIS
 
At this point you can't make any calculations because you have not yet chosen the place for which you want to calculate! You can choose a place in three different ways:
  • By clicking on the map (you can zoom in and move around in the usual way).
  • By entering the name of a place (town, street) in the "Address" field below the map.
  • By writing the latitude and longitude coordinates in the boxes below the map.
Figure 3 shows you where to find these three options in the interface.
 
In some areas we don't yet have the necessary data, especially solar radiation data. If you choose a place where there are no data, you will get a message in red to the right of the map, saying "Location without data". In some areas we have data on the terrain but not solar radiation, so you can download the horizon height but nothing else. Then the warning will be: "Location without radiation data. Just horizon data available". Figure 4 shows a map of the extent of the different solar radiation data sets used in PVGIS.
 
Figure 4. Geographical extent of the solar radiation data sets in PVGIS
 

Choosing type of calculation

You can make several different types of calculations with PVGIS. You choose which type by selecting one of the tabs to the right of the map (see Figure 5). For each of the calculation types you can get help by clicking on the title of the calculation tab.
Figure 5. Selecting the type of calculation
 
At the moment the calculations that can be made with PVGIS are:
  • Performance of grid-connected PV Here you can calculate the long-term average energy output from PV systems that are connected to the electricity grid so that the energy produced can be used locally or sent to the grid. This works for fixed PV systems, where the PV modules are mounted in a fixed position, either on a free-standing rack or on a building.
  • Performance of tracking PV systems Here you can calculate the long-term average energy output from grid-connected PV systems where the modules are put on a sun-tracking mounting so the modules receive more sunlight. You can choose between a number of different types of tracking systems.
  • Performance of off-grid PV systems This tool allows you to make calculations on PV systems that are not connected to the electricity grid but use batteries as energy storage.
  • Monthly radiation With this tool you can get monthly average radiation and temperature data for each month over a range of years.
  • Daily radiation Here you can calculate the average solar irradiance and temperature during the day for an average day in each month.
  • Hourly radiation This tool lets you download a time series of hourly solar radiation and/or PV power values.
  • TMY A tool to generate Typical Meteorological Year (TMY) data of solar radiation, temperature and other meteorological data, used in many fields, for instance in the calculation of the energy performance of buildings.

Getting results!

For each of the calculation types you have to enter some information about the type of calculation you want to make. Once you have done this, you can do one of two things:
  • You can see the results of the calculation as graphs and numbers in the PVGIS web page. The results will appear below the map and input fields.
  • You can download the calculated data in CSV format, suitable for use with spreadsheets and other software. The formats of the downloaded data for each of the calculation options are described here.
The general way to do this is to just click on one of the two buttons at the bottom of each calculation tab. These are shown in Figure 6.
Figure 6. Buttons for selecting the type of output of the results
 
There are a couple of exceptions to this. The hourly time series calculation will give you so much data that it doesn't make sense to try to make graphs of the data. In this case there is only the option to download CSV data. For the TMY data you can download the data in two different formats. One is a normal CSV file, while the other is in the EPW format (strictly speaking this is still CSV) which is used for the EnergyPlus software.
The results shown in the web page consists of graphs and statistical data, such as yearly averages. In many of the graphs you can see the values by letting the mouse hover above the graph. The graphs can be downloaded as graphics files (PNG format). It is also possible to get the output as a PDF file, showing graphs and tables of the values used to produce the graphs.
Other great links to Solar Panel information
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