Modeling your installation

Now that you have an idea of cost of the install, insurance, location of the installation etc you can model the project and determine if it is viable. What does this mean? You can utilize your existing data and data provided within the internet applications or software listed below and then project outcomes over a timeline. If you have a microFIT contract that would be 20 years.

There are a number of applications out there, both free and paid. 

PVWatts

This is a free site that seems to be the standard that most people refer to in order to get a basic understanding of their homes solar potential. I highly recommend this site as your first calculator. It is simple to use and provides clear explanations of each area.

http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/

This is an interesting site that provides a site assessment online using google earth. Interesting tool to use for preliminary investigation but you should still have a proper onsite review.

http://solarrating.ca/

SAM –System Advisor Model

SAM

This application is free and downloadable from the National Renewable Energy Laboratory in the U.S It is a performance and financial model that allows you to change different variables that may impact your project from the module and inverter to costs, taxation, etc etc. It is very comprehensive and once the info is plugged in, allows you to view this info in a number of ways such as charts or just numbers in columns and then export to excel. It includes an extensive database of inverters and modules so you can automatically plug in specific info on the inverter or modules that you intend to purchase.

https://sam.nrel.gov/

PVsyst

Although not free, you can download it and use it for a short period of time ( I think 20 days) before the trial expires. It is as extensive and detailed as the SAM software. http://www.pvsyst.com/

PV*SOL

Another European software that must be purchased. It does come in several configurations. http://www.solardesign.co.uk/pv.php

Excellent article explaining “derate” Derate is a factor you use that includes all the elements that may “derate” or reduce the efficiency of the PV array such as soiling, wires, inverter effieciency et.

http://homerenergy.com/documents/SolarPro3_%20Production%20Modeling%20High%20Res_201004-1.pdf

Below are 2 services from Europe that aggregate data both paid and purchased mainly geared to solar professionals.

The SoDa Service is a broker to a list of services and webservices related to Solar Radiation proposed by several research centers in Europe and abroad.

http://www.soda-is.com/eng/index.html

The goal of IEA/SHC Task36 "Solar Resource Knowledge Management" is to provide the solar energy industry, the electricity sector, governments, and renewable energy organizations and institutions with the most suitable and accurate information of the solar radiation resources at the Earth's surface in easily-accessible formats and understandable quality metrics. 

http://project.mesor.net/web/guest/unifying

The Future of Sunlight

One variable that hasn’t been addressed is the future of solar irradiation of the earth. In other words what predictions are there about the amount of sunlight in the future. None of the software above that I am aware has taken this into account. The only mention of a “forecast of solar potential” is in a document that I have read on the internet where they mention some global climate prediction models;

http://www.wspgroup.com/upload/Upload/SEBE_State_of_the%20Art_120323.pdf

Essentially what is reported is that there will not be any great variance in solar insolation over the next 100 years although climate change will heat up the planet. In some areas of the planet there may be a slight decrease in sunlight while in other areas ( the Mediterranean) there will be a slight (3%) increase in sunlight.