Solar electricity handbook_ - A simple, practical guide to solar energy - how to design and install photovoltaic solar electric systems (2012 edition) ( PDFDrive )

Solar electric bikes

Electric bikes and motorbikes are gaining in popularity and are an excellent way
of getting around on shorter journeys.

Electric bikes with pedals and a top power-assisted speed of 15mph are road-
legal across Europe, Australia, Canada and the United States. You can ride an
electric bike from the age of fourteen.

Legally, they are regarded as normal bicycles and do not require tax or
insurance. They typically have 200-watt or 250-watt motors (up to 750-watt
motors are legal in North America). Most electric bikes have removable battery
packs so they can be charged up off the bike and usually have a total capacity of
330–400 watt-hours and a range of 12–24 miles (20–40km).

Thanks to their relatively small battery packs, a number of owners have built a
solar array that fits onto a garage or shed roof to charge up their bike batteries.
This is especially useful when you have two battery packs. One can be left on
charge while the second is in use on the bike.

A number of people have also fitted solar panels onto electric trikes in order to
power the trike while it is on the move. Depending on the size of trike and the
space available, it is usually possible to fit up to around 100 watts of solar panels
to a trike, whilst some of the load-carrying trikes and rickshaws have enough
space for around 200 watts of solar panels. Such a system would provide enough
power to drive 15–20 miles during the winter, and potentially an almost
unlimited range during the summer, making them a very practical and
environmentally friendly form of personal transport.

Whilst the solar-only range may not seem that great, there are many drivers who
live in a sunny climate and only use their cars for short journeys a few times
each week. For these people, it could mean that almost all their driving could be
powered from the sun.

Even in colder climates such as the United Kingdom and Northern Canada, solar
power has its uses in extending the range of these cars: by trickle-charging the
batteries during the daytime, the batteries maintain their optimum temperature,
thereby ensuring a good range even in cold conditions.

Meanwhile, a number of electric car owners have already made their cars solar
powered by charging up their cars from a larger home-based solar array,
providing truly green motoring for much greater distances. Several electric car
clubs have built very small and lightweight solar powered electric cars and

tricycles and at least one electric car owners’ club is planning to provide a solar
roof to fit to existing electric cars in the coming year.

Appendix F – Building Your Own Solar

Panels (and Why You Shouldn’t)

A number of people have asked me about building their own solar panels from
individual solar cells and asked for my opinion on a number of websites that
make claims that you can build enough solar panels to power your home for
around $200 (£120).

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 websites that say it is possible
to build your own solar panels and run your entire house on solar for an outlay of
$200 or less, selling excess power back to the utility grid and even generating 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 free 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 websites omit to tell you that.)

A list of companies and eBay sellers who will sell you individual solar
cells

Many of the websites claim, or at least imply, that you can run your home on a
solar panel built for around $200. In reality, this amount will buy you enough
solar cells to build a solar panel producing 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 cheap, but professionally
built 60–100 watt solar panel with five-year warranty and anticipated 25-year
lifespan for around $200 (£120) 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 specifically designed
components. They are built in a clean room environment to very high
standards. For example, the glass is a special tempered product designed to
withstand huge temperatures and ensure maximum 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 inside a
solar panel are likely to create a high temperature arc, which can start a fire

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 websites 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 be in violation of the
National Electric Code and you would therefore not be allowed a permit to
install them

Many of these websites imply 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.

Most instructions recommend building a frame out of wood and covering it with
Plexiglas or acrylic. This is extremely bad advice:

Never build a solar panel 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 heat build-up within the panel due to
short circuits or poor quality soldering, these spot temperatures could be as
high as 800°C (1,472°F). At these sorts of temperatures, you can easily start
a fire

Do not use Plexiglas or acrylic to cover your home-made solar panel.
Tiny imperfections in the material can lead to light refractions and intense
heat build-up on elements within the panel. Plexiglas and acrylic can also
distort under high temperatures, increasing these light refractions over time.
The effect can be like a magnifying glass, concentrating the intensity of the
sunlight onto a small spot on the solar cell, which could result in fire

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 websites 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

Table of Contents

Copyright
Introducing Solar Energy
A Brief Introduction to Electricity
The Four Configurations for Solar Power
Components of a Solar Electric System
The Design Process
Scoping the Project
Calculating Solar Energy
Surveying Your Site
Understanding the Components
Components for Grid-Tie systems
Components for Stand-Alone Systems
Planning, regulations and approvals
Detailed Design
Installation
Troubleshooting
Maintaining Your System
Internet Support
A Final Word
Appendix A – Crystalline Solar Panels and Shading
Appendix B – Solar Insolation
Appendix C – Typical Power Requirements
Appendix D – Living Off-Grid
Appendix E – Other Solar Projects
Appendix F – Building Your Own Solar Panels (and Why You Shouldn’t)