It is important to realize that photovoltaic power systems are expensive when compared with the low price of utility power in North America and the rest of the world. Normally.

You should reserve the electric power produced by photovoltaic modules for your most energy-efficient appliances, tools, lights, etc.

Although it is technically possible, heating with photovoltaic systems is generally not recommended. You can easily and more efficiently collect heat with a solar thermal system.

A solar water heater or a solar pool heater, as mentioned earlier, generates more hot water with less initial cost than any photovoltaic-powered heater.

Also, for cooking, it is normally more cost-effective and convenient to use a stove that operates on propane or natural gas rather than solar electricity.

Stand alone solar-powered homes and cottages often rely on wood cook stoves for cooking and space heating. Refrigerators are becoming more energy efficient, so the cost of operating them with solar power is now feasible. There are some great energy-efficient products now.

From an economic point of view, first consider investing in energy-efficient electric AC appliances, and then size your photovoltaic system based on actual consumption (read our post on How to Size your Home Made Renewable Energy System). For example, using compact fluorescent lights will reduce your electrical consumption for lighting by 80 percent or more.

In our next post we will discuss the types of solar panels to choose. Stay tuned

The term photovoltaic is derived from a combination of the Greek word for light “photo”, and “Volta,” the name of the Italian physicist, Alessandro Volta, who invented the battery in 1800.

The photovoltaic effect is the direct conversion of solar energy into electricity. This process does not generate much heat like solar domestic hot water or solar pool heating systems do. It also differs from the process used in solar thermal, where concentrated solar energy is used to produce steam that activates a turbine connected to a generator.

Photovoltaic power systems do not have any moving parts. They are reliable, require little maintenance and generate no noise or pollutants. Photovoltaic systems are great in that they are modular. The building blocks or cells come in a wide range of power capabilities, from a fraction of a watt to more that 300 W.

Modules can be connected to achieve the power that your application requires. Some large photovoltaic power plants have several megawatts of power, although most installed PV systems are much smaller. Unfortunately, there is a lot of the sun’s energy lost in this transfer of energy from light to electricity. Everyday larger and more efficient panels are manufactured as technology & research develop to produce more efficient solar cells.

Even though solar panels are not that efficient at converting light to electricity, they remain a very good choice in the search for renewable energy system because of their low maintenance and long life.

Properly installed, your solar panel array should last around 50 years. Not a bad long term investment for most people.

The Advantages of PV Power Systems

Users of photovoltaic power systems appreciate their quiet, low-maintenance, pollution-free, safe and reliable operation, as well as the degree of independence they provide.

Why else should you consider a PV system?

If you are at some distance from an electrical grid, it may be cheaper to generate your own power rather than pay to extend transmission lines from the grid.

Fossil fuel- Diesel, gasoline or propane generators are the main alternatives, but many people find them noisy, polluting and costly to run and maintain. You can check our Bio Diesel Fuel information as a source of clean renewable energy option.

It also makes little sense to turn on a 5-kW generator to power a few 100-W light bulbs or the TV. Photovoltaic systems reduce the negative aspects of generators by using them only as a backup.
When capital cost is an issue, or when photovoltaic systems alone are not enough to replace an existing generator, you can use a wind generator as part of a hybrid system. It works great and reduces the use of the generator.

This kind of charging system is more efficient than a generator running continuously at low load. In addition to saving fuel and lowering maintenance costs, you will increase the generator’s life span.

Also, since the solar panels and battery banks are modular, you can expand the photovoltaic system gradually as your budget or needs increase. That, we think is the best part.

Whether you build your own, or buy one, you will need some sort of controller for your wind turbine.

There are lots of charge controllers manufactured for solar and wind power systems. Any company that sells alternative energy stuff will have them. There are also always lots of them for sale on Ebay.

What’s a Charge Controller?

Basically, the general principle behind a charge controller is that it monitors the voltage of the batteries in your renewable energy system. The controller either sends power from your homemade wind generator into the batteries to recharge them, or diverts power coming from the wind generator to another place. This only occurs if the batteries are fully charged (to prevent over-charging and destroying the batteries).

We are assuming you are using a 12 volt battery system for the purposes of this discussion.

When your homemade wind generator is in operation, the wind generator is connected to the controller. Wires then run from the controller to the battery.

When you use power to run some appliance, say your TV, the power is then taken directly from the battery. If the battery voltage drops below 11.8 volts (you can set this on the controller), the controller switches the generator power to charging the battery. If the battery voltage rises to 14.5 volts (again, you have to set this), the controller switches to dumping the generator power into the dump load.

Usually, a water heater, or some other small device is used as a dump load. There are switches to adjust the voltage levels at which the controller changes between the two states of charging. A 11.8 and 14.5 volts as cut-in and cut-out voltages are recommended after consultation with battery experts.

There are two LED lights on the charge controller. When charging the battery, one LED is lit. When the power is being dumped to the other load the other light will be lit.

Usually the system runs pretty automatically and the LED lights gives us easy feedback on whether our renewable energy system is performing properly, and what it is doing right then. When the wind is really blowing more current goes into the batteries, which means more load on the generator. The system pretty much governs itself.

In a storm the force of the winds wind can get pretty dangerous. Switching the controller to dump power into the other load does a good job of braking the homemade wind generator and slowing it down.

Warning: the whole blade and hub assembly can swing around and knock you on the head if you are not very careful and the wind changes direction while you are working on it.

Next post: Wiring The Wind Generator. Stay tuned

For some of you it may be instructional to start at a basic level in understanding how electricity works in everyday life.

Watts

You might have noticed that the power consumption of electrical devices is measured in watts. Most people are fairly familiar with the term watt, but most don’t know what it describes. A watt is the power produced by current (amps) flowing through a wire multiplied by the pressure (voltage) at which it flows.

Volts

Like water pressure in a pipe, voltage is the pressure of electricity flowing through the wire.

Amps

This is the amount of electricity flowing through the wire.

Power Rates

We are most familiar with the term KWH (or Kilowatt-Hour) as it appears on our monthly power bills. This is the rate of power flowing through a wire. As an example, if a 100 watt light bulb is turned on for ten hours the power rate would be 100 x 10 = 1,000 watt-hours or 1 Kilowatt hour (kilo means 1000)

Direct Current (DC)

We will be discussing both Direct Current (DC) power and Alternating Current (AC) in the planning of your renewable energy system. AC current is what you presently use in your home.

The most important difference between AC and DC power is that DC current can be stored in a battery while AC power cannot.

In the renewable energy system that you are designing to run your home, DC power produced by your wind generator or your solar panel will be converted to AC power by using an inverter. In this way you can still use many of the same AC appliances that you currently depend on.

Common DC voltages are 12, 24 and 48. The advantages of DC appliances are many, but most important is that DC motors are more efficient than AC motors. There are many applications for DC power and the benefit is that we can use this form of energy in our off grid home, while in your present tied-to-the-grid home you cannot.

AC Current

Alternating current is called this way because the current changes direction constantly. AC is the most common form of electricity usage today mostly because it is easier to work with than common DC current.

To size a wind power renewable energy system, you first have to determine your energy budget.

In order to complete an energy budget you will need to know how much power typical appliances use. What follows is a chart to help you.

AC Appliances Typical Energy Usage in Watts

Toaster Oven 1500
VCR 35
Well Pump 800
Sewing Machine 87
Satellite TV 50
Refrigerator/freezer 460
Vacuum 1125
Circular Saw 1500
Hair Dryer 1500
Jigsaw 300
Computer 100
Laptop 60
Monitor 60
27” TV 200
DVD 14
Drill 800
Microwave oven 1245
Compact fluorescent 13
Battery Charger 25
Blender/mixer 350
Belt Sander 800
DC Appliance Energy Usage
Appliance Watts
Cell Phone 4
Motor (small) 65
Sunfrost refrigerator 13
Radio 15
Stereo 30
Water Pump 50
VCR 15
14” Color TV 75
Battery Charger 7
Inverter Standby 5
Halogen Light 20

Now that you know how much energy your appliances use you can figure out your total energy usage per week, and per month.

In order to do this, simply figure out how many hours each device is used each day. Multiply this number by the number of watts that device uses and you will come up with the watt-hours of usage. Add all of the totals together to come up with your total watt-hours of usage for the week, and for the month.

Keep these numbers with your notes; you will use them to design your charging capacity, battery bank and inverter sizing.

Figuring out your own energy usage

Take the numbers you got from your own appliances or use the numbers we provided and work out your own energy budget.

Example:

Add as many items as it takes to complete your inventory. It should be noted that most households use approximately 20 Kilowatt hours per day on average.

Your new wind-powered renewable energy system would have to be very large to compensate for this high level of usage. A typical home made wind generator is only going to produce about 1 Kilowatt (1000 watts) of power. This is a wind turbine with blades 4 feet long, making a blade outside diameter of 8 feet.

Through conservation and buying newer more energy efficient appliances you can achieve the goal of living off the grid. It just takes some time and effort on your part. You can live on a total family usage of about 2 or 3 Kilowatt-hour per day and live a relatively normal life, with satellite TV, satellite internet, DVD’s, lights etc. It can be done.

Some questions answered

Once I know how much power I will need to run my home, how will I figure out how much power production I need?

Answer: You figured out how much power you use in the earlier exercise. You should be aiming for around 10 kilowatt hours per day. You could actually run your entire home on just under 3 kilowatt hours per day with energy conservation measures

The power formula goes like this:

System Power = (Wind Speed ^3) (Blade Diameter ^2) x .00478

Wind Speed is measured in miles per hour.

Blade Diameter is measured in feet.

Power is measured in Watts

It is easy to figure out your blade diameter. A widely used 8 foot blade diameter has been proved with great success.

To find your wind speed you will have to find a wind speed chart, or monitor your own wind speed for a while to obtain your own readings.

Here is a source of wind speed data.

World Wind Speed Data Maps

Let’s say your average wind speed is about 12 mph, which is pretty good. Plug that into your formula too. It would look something like this:

System Power = (12^3) (8^2) x .00478 = (1728) (64 ) x .00478
= 110592 x .00478 = 528 watts

Multiply this by 24 hours and you will have 12672 watt-hours, or about 1.2 kilowatt hours per day.

Wind speed has the greatest impact on power output since it is cubed in the previous formula. You can’t change wind speed though. You either have it or you don’t.

This brings up our next question.

Should I build one large wind generator, or several small ones?

Answer: Obviously blade diameter can have a huge impact on the amount of power that your homemade wind generator produces. There are a few concerns though. Yes, you could put up a homemade wind generator with a 20 foot blade diameter, but the forces of the wind at storm levels would demand a very substantial tower. Also, if you live in a populated area your neighbor might not appreciate a huge wind generator in your backyard. Ask first.

Some areas even have bylaws about this stuff, do some research first and find out what you can and cannot do.

Usually it is much easier to find towers for several smaller wind generators and parts to build them too. If you have areas on your property that are clear in different directions, put up several homemade wind generators to capture the wind more effectively from different directions with much smaller towers.

One final thing, when you have several homemade wind generators you can shut one down for cleaning or maintenance (or if a storm does this for you) and your other ones are still providing power.

A lot less work in the long run, and less headaches with a smaller system.

Get the full scoop on How to Build Your Own Home Made Wind Generator