In the last two articles in the Solar Energy Primer we discussed how to reduce energy consumption and Solar Panels.  In this article we will discuss DC to AC Inverters and the different models on the market.

The AC inverter is the heart of your Renewable Energy Systems Power Panel.  Unless you want to revert back to really old school where the only off-grid options where a battery bank and 12volt RV appliances, it is necessary to have an AC Inverter.  The basic function of an Inverter is to take input DC voltage (VDC) and convert it to AC voltage (VAC).  It's secondary function is to charge a battery bank should you chose to have one.  Most grid tie systems don't have a battery bank, but could have one for backup power supply.  If you are off-grid, a battery bank is a requirement.  During times of none sufficient power supply from your renewable energy systems, the inverter will convert DC power from the battery bank to AC power for your home appliances.

Electricity can be viewed as a Sine Wave, which is a mathematical function that can be viewed as a graph.  You can search the Internet for more information, but for our purpose think of Sine Waves as the purity of the electricity provided by your inverter to your appliances.

There are 4 types of Inverters:

• Square Wave Power Inverter - These are very inexpensive and not to be used for home systems.  Usually in the under 500W range, you will see these inverter types used in cars and boats and plug into a cigarette lighter.
• Modified Sine Wave Power Inverter - One of the most popular inverters due to its economic price, it produces and AC wave form somewhere between Square Wave and Pure Sine Wave.  These inverters are sometimes called Quasi-Sine are less expensive and work with most AC appliances.  Some appliances without a regulator will cause a buzzing sound and some appliances such as motors that use speed controls or timers will not function with these inverters.  Modified Sine Wave Inverters are recommended for small cottage use or boats, but not your average home use.
• True Sine Wave Power Inverter - These inverters produce the cleanest power and work best with all AC powered appliances in your home.  Although True Sine Inverters are more expensive, it is worth every penny.  After spending your hard earned money on producing your energy via Solar, Wind or Mini-Hydro, the last thing you want is to then lose it and/or produce "dirty" power.  True Sine Wave Inverters are now very affordable and are really the only way to go for off-grid home AC inverter use.
• Grid Tie Power Inverters- If you are already connected to the Utility, you can stay that way with a Grid Tie Inverter and use the Utility as your backup power.  As an added bonus, most Utilities now provide "net-metering" which allows you to sell your extra power to them.  This in effect means during peak producing hours, and after your optional battery banks have been charges, you will sell your extra power back to the Utility actually spining your meter backwards.  The Grid Tie Inverters are True Sine Wave Inverters with a added function of sensing your power consumption and synchronizing with the Utility to sell it and push to the grid.  It also has a safety feature to sense power failure from the grid and if so, cease pushing electricity.  This is a safety feature for Utility workers to ensure no home electricity is powering the grid while the workers are repairing the issue.

When configuring your Renewable Energy System keep in mind that all your DC components such as Solar Panel array, Battery Bank and Inverters all need to run on the same voltage.  In followup articles we will discuss wiring run length and gauge.  These are all tied into selecting the proper VDC for your system.

You may be wondering what to do with your heavy usage appliances like stove and dryer?  Well you can compatible inverters in series to double the ouput voltage.  You would use this technique to produce 220-240 volts required for these heavy appliances.  You can also configure them in parallel to double your power.  We will cover these topics in much more details in later follow-up articles in Solar Power Primer series so stay tuned!

Keep it Green...

In the first part of Solar Energy Primer we discussed the prequel of planning your renewable energy system, reduced consumption and calculating the consumption of your main appliances.  Part two of Solar Energy Primer will discuss Solar Panels.  Subsequent parts of Solar Energy Primer will cover Power Inverters, Charge Controllers, Batteries and more... so stay tuned!

Solar Panels, also called Photovoltaic (PV), convert the sun's energy into electricity we can use to power our appliances and run our homes.  In very basic terms, solar panels capture photons in thin silicon wafers which cause electrons to get "excited" and move, thus producing electricity.  A solar panel is a collection of silicon solar cells wired in series to produce a specific voltage.

There are 3 basic types of Solar Panels on the market today:

• Monocrystalline: The most efficient and expensive solar panels are made with Monocrystalline cells. Long silicon rods are produced which are cut into slices of .2 to .4 mm thick discs or wafers which are then processed into individual cells that are wired together in the solar panel.
• Polycrystalline: Usually called Multi-crystalline, Polycrystalline cells are slightly less expensive and efficient as Monocrystalline cells because they are grown in a large block of crystals rather then on long silicon rod like Monocrystalline crystals.
• Amorphous: Usually called Thin-Film, a thin layer of silicon deposited on a base material such as metal or glass to create the solar panel. Amorphous solar panels are cheaper, but much less efficient then Monocrystalline or Polycrystalline panel.  Although less effective, Amorphous solar panels can be made into long sheets of roofing material to cover large areas of a south facing roof surface.

It is important to note that PV panels produce Direct Current (DC) electricity or most commonly called VDC.  Our home appliances require Alternate Current (AC) power (VAC), thus a power inverter is required to convert DC to AC power we will use in our homes.  We will get into Power Inverters and Chargers in Part 3, but keep this in mind that we are talking DC Volts when discussing raw electricity produced from Solar.

A typical 12V PV panel contains 36 solar cells and be rated up to 100 watts.  Solar Panels above 100W are usually 24V, two 36 solar cells wired in series.  It's more common to see 24V or 48V (two 24V wired in series) systems installed than 12V systems.  The advantage is the higher the voltage, the smaller the wire gauge required to transfer the electricity to from the solar array to the inverter.  The inverter will be configured to accept the VDC from the Solar Array and convert it to VAC for home appliance use.  In solar energy systems that have a battery bank to charge, the inverter will drop the higher 24V or 48V to charge the battery bank and when necessary convert the 12VDC from the battery bank to 120VAC.

Stay tuned for more Solar Energy Primer series covering Solar Energy Systems.

PART 1

Before you start shopping for Solar Panels and related Solar Power Equipment, you must first determine your electrical consumption to size the system that is required to meet your needs. It is more cost effective to reduce consumption then to produce or harness the Solar Energy. There is no need to buy everything immediately. It is easier to proceed one step at a time and avoid buying equipment that will have to be replaced later.

Start by listing the electrical equipment that will be used and determine how energy will be consumed. There are products such as the cent-a-meter that is wired directly to your electrical panel and can be used to monitor and trend your electrical use. This research, monitoring and planned reduction will open your eyes as to how much electricity we waste. The more accurately you define your energy requirements, the easier it is to determine which photovoltaic energy system meets your expectations.

After you have accurately defined your present and extrapolated future needs and identified your consumption habits, you can decide what size of system you need. Some of the factors that need to be considered include:

• the seasonal profile of the load, i.e. the period when electricity demand is highest and electricity output is lowest, which is usually in fall or winter.

• the weekly/monthly profile of the load.

• the daily profile of the load (power required and number of hours per day) for each appliance.

• -type of load to be powered (motors, lights, etc.)

As the consumption for each household is different, so will the configuration of the system. Just remember, you do not have to create a 100% self sufficient Solar PV Array or invest hundreds of thousands of dollars to setup an off-grid or grid-tie renewable energy system. Start slow, research and plan... the point is to start and take action. Keep it Green!

Solar energy is a clean and abundant energy resource that can be used to supplement many of your energy needs. Solar energy can be utilized as a form of heat, such as solar water heating, and as electricity, such as solar photovoltaicc. Solar water heating systems are commonly referred to in the industry as Solar Domestic Hot Water (SDHW) systems.

Solar hot water heater collectors are good for your wallet and the environment. Heating domestic hot water accounts for about 20-25% of your home heat energy requirement. A correctly-sized solar system can provide 60%-70% of a household’s hot water needs. Providing more than this is not advisable, as too much heat will be produced in the summer.

Solar should not be seen as an alternative to gas or electricity, but rather as a supplement. Solar cannot totally replace the need for gas or electric heating as there are sometimes days when there is little sunlight.

Consumers can now buy "off-the-shelf" solar water heaters that meet industry-wide standards, providing a clean alternative to gas, electric, oil or propane water heaters. Freeze-protected solar water heaters have been specifically designed to operate reliably through the entire year, even when the outside temperature is either well below freezing or extremely hot.

From March to September solar energy could provide all your hot water but will only partly heat the water during the winter months, when your conventional heating method will need to be used to bring it up to temperature. Most homes will need to replace their current hot water cylinder, with a dual coil solar model.