Build your own solar panels? Proceed with caution

A number of people have asked me about building their own solar panels from individual solar cells and asking for my opinion on a number of web sites that make claims that you can build enough solar panels to power your home for around $200.

I have a huge amount of respect for people with the aptitude and the ability to build their own equipment. These people often derive a great deal of personal satisfaction from being able to say, "I built that myself". Largely, these people are to be encouraged. If you want to build your own solar panels, however, I would advise caution.

There have been many claims made from certain web sites that say it is possible to build your own solar panels and run your entire house from solar panels for an outlay of $200 or less, sell excess power back to the utility grid and even generate an income from solar.

Most of the claims made by these websites are either false or misleading. When you subscribe to these services, you typically receive the following:

• Instructions on how to build a solar panel that are virtually identical to instructions that are available freely from sites like instructables.com
• Information on tax credits and rebates for installing solar PV in the United States. (However, these credits and rebates are not applicable for home built equipment. The web sites omit to tell you that).
• A list of companies and individuals who will sell you individual solar cells.

Many of the web sites claim, or at least infer, that you can run your home on a solar panel built for around $200. In reality, your $200 will buy you enough solar cells to build a solar panel producing between 60-120 watts, which is certainly not enough to allow you to run your home on solar power.

Leaving aside the obvious point that you can buy a professionally built 60-100 watt solar panel with five-year warranty and anticipated 25-year lifespan for between $80-140 if you shop around, there are various reasons why it is not a good idea to build your own solar panels using this information:

• A solar panel is a precision piece of equipment, designed to survive outside for decades of inclement weather and huge temperature variation including intense heat.
• Professionally manufactured solar panels use highly specialised components, in a clean room environment and to very high standards. For example, the glass is a special tempered product designed to withstand huge temperatures and optimise light penetration with zero refraction.
• The solar cells you can buy from sellers on eBay are factory seconds, rejected by the factory. Many of them are blemished or chipped and damaged. They are extremely fragile, almost as thin as paper, brittle like glass and very easy to break.
• Unless you are an expert at soldering techniques, you are likely to create a cold solder joint between one or more solar cells. Cold solder joints are likely to create a high temperature arc, which can start a fire.
• Do not use plexiglass to cover your home made solar panel. Tiny imperfections in plexiglass can lead to light refractions and intense heat build up on elements within the panel. Plexiglass can also distort under high temperatures, increasing these light refractions over time.
• Most instructions recommend building the frame and backing out of wood. This is dangerous because of the intense heat build up in a solar panel. On a hot and sunny day, the surface temperature of the panel can exceed 90°C (175°F). If there is any additional localised heat build up within the panel, these spot temperatures could be as high as 800°C (1472°F).
• There are several documented cases where home made solar panels have caught fire and caused damage to people's homes. These fires are typically caused by poor quality soldering, or the use of wrong materials.
• Many of the web sites promoting home made solar panels claim that you can power your house with them. In the United States, connecting home made panels to your household electrics would in violation of the National Electric Code and you would therefore not be allowed a permit to install them.
• Many of these web sites infer that you can also sell your power back to the utility companies. It is actually illegal to install non-approved power generation equipment to the utility grid in many countries, including both the United States and the United Kingdom.
• The tax credits and rebates that are available for installing solar PV on your home are not available for home built solar panels.

Many people who make their own solar panels have found that they fail after a few months due to moisture penetration, or fail after only a few days or weeks due to high temperature arcing and panel failure.

If you wish to build a small solar panel for fun, as a way of learning more about the technology, then you can get instructions on how to do this free of charge from many web sites such as instructables.com. Build a small one as a fun project if you so wish. You will learn a lot about the technology by doing so. However:

• Treat your project as a learning exercise, not as a serious attempt to generate electricity.
• Never build a solar panel with a wood frame.
• Treat your home made solar panel as a fire hazard.
• Do not mount your completed home made solar panel as a permanent fixture.
• Only use your home made solar panel under supervision, checking regularly for heat build-up on the solar panel or frame. Remember that the front of the solar panel may get extremely hot, especially on hot, sunny days. Do not touch the solar panel with your fingers.
• Visually check your home made solar panel every time you plug it in to ensure there is no moisture penetration. If you spot moisture penetration, stop using the solar panel immediately.
• Use the cheapest solar charge controller you can find for your project. The warranty will be invalidated on the controller by using a home made panel, but at least if you damage a cheap controller you haven't damaged an expensive one.
• Never charge batteries using your home made solar panel without using a solar charge controller.
• Never run an inverter directly from your home made solar panel.

Michael Boxwell is a technical architect and designer. He is the author of a number of books including the Solar Electricity Handbook and The Electric Car Guide series of books.