installing a roof panel

SOLAR PANELS FOR YOUR HOME: AN INTRODUCTION

Solar Power

Solar panels- are they the way of the future? Are they right for you? I have no idea. But this article is meant to be an introduction on the subject, so you can decide for yourself.

In a solar power system (also known as a photovoltaic system), power is produced for your home using a 3-part system. Solar panels, usually placed on your roof and facing south in the northern hemisphere, absorb sunlight and convert it into direct current. Mounting systems adjust the angle of your solar panels, to optimize energy absorption. Then an inverter converts the power from direct current to alternating current, making it useable for household appliances.

Update: February 2017 – Recently, I have come across some modern devices that function extremely well as a solar gadget, particularly with cell phone charging. This post outlines some ways in which you can harness the energy of the sun to keep your mobile devices powered up on the go, which can be extremely handy if you are out in nature. This is ideal for camping trips or for emergency situations if you get lost in the woods and need to contact help. Don’t leave home without your Grid2Go!

There are two options for the surplus energy produced- a grid connect system and a standalone system.

installing a roof panel

GRID CONNECTED vs STAND ALONE SYSTEMS

GRID CONNECT SYSTEMS

A grid connect system works like this- during the day, solar panels produce electricity, supplying all of your energy needs. All surplus energy is fed back into the grid, for which your energy provider pays you. This is commonly known as a Feed in Tariff. During the evening, the grid supplies your household’s energy needs. In this manner households can greatly reduce their energy bills, sometimes even turning a profit when the energy they feed to the grid exceeds the energy they take from it.

STAND ALONE SYSTEMS

A standalone system is designed to be independent of the gird. The surplus electricity generated during the day is fed into storage batteries. The system should be designed so that enough energy is collected during the day to supply the energy needed for the evening. A backup generator is an extremely good idea for such a system, to supply power in periods of very high demand or extended cloudy weather/winter months. Where overall performance is the focus of a grid connect system, in a standalone system daily energy generation to meet your needs is critical.

THE EQUIPMENT OF SOLAR POWER SYSTEMS

SOLAR PANELS

The solar panels (or solar module) is where the energy is produced.  The panels are made of silicon, and when they absorb the light from the sun they give off electrons. These electrons are then harnessed and turned into the kind of electricity used in the home.

There are 4 kinds of solar panels available commercially.
Single crystal modules have been around the longest and are the most effective. They are the most efficient (10-17%) but also the most expensive. They are the dotted or octagon shaped panels you would often see on satellites.
Poly/Multicrystalline modules are second in line. They are cheaper than single crystal, but run at 9-14% efficiency. They are the blue colored panels you sometimes see.

String ribbon modules are fairly cheap and are 7-8% efficient.
Thin Film (Amorphous) modules are a thin layer of silicon deposited on top of steel or glass. They are cheap to make, but their efficiency is very low (5-7%). This is what they use in solar powered calculators.
Solar modules are rated by wattage output, more accurately peak watts (STC). These are based on laboratory conditions, and real life results will tend to fall short of these. Plan for an 80-90% output of the STC.

While summer has longer days and therefore more hours of direct sunlight, PV systems perform more efficiently at lower temperatures. A clear winter day with sun reflecting off of the snow may potentially produce more energy output than a hot summer day. Kind of mind blowing, really.

MOUNTING SYSTEM

These adjust the angle of your panels to optimize energy production. You’ll generally want the angle of your panels to be equal the distance you are from the equator is degrees of latitude. Example, New York City is at 40 degrees latitude, so you’d want your panels to face south at a 40 degree angle in NYC.

INVERTER

Amplifies one voltage to another, and converts direct current to alternating current, which our homes use. 6-13% of energy is lost. The cooler it is, the more efficiently it operates. A fan or heat sink a good idea.
Some final notes:

The best situation is to have your panels face south (In the northern Hemisphere). They can face East/West, but that will lose 10-20% efficiency. Facing north is basically useless.
Bigger panels means less wiring, and therefore lower labor costs. You want to take advantage of all the power produced, so efficient wiring is key (use 10 gauge instead of 12 if the lines between your panels and inverter in over 100 feet).