How do solar cells generate electricity?

Photovoltaics or PV for short can be thought of as a direct current (DC) generator powered by the sun. When light photons of sufficient energy strike a solar cell, they knock electrons free in the silicon crystal structure forcing them through an external circuit (battery or direct DC load), and then returning them to the other side of the solar cell to start the process all over again. The voltage output from a single crystalline solar cell is about 0.5V with an amperage output that is directly proportional to cell's surface area (approximately 7A for a 6 inch square multicrystalline solar cell). Typically 30-36 cells are wired in series (+ to -) in each solar module. This produces a solar module with a 12V nominal output (~17V at peak power) that can then be wired in series and/or parallel with other solar modules to form a complete solar array to charge a 12, 24 or 48 volt battery bank.

Will solar work in my location?

Solar is universal and will work virtually anywhere, however some locations are better than others. Irradiance is a measure of the sun's power available at the surface of the earth and it averages about 1000 watts per square meter. With typical crystalline solar cell efficiencies around 14-16%, that means we can expect to generate about 140-160W per square meter of solar cells placed in full sun. Insolation is a measure of the available energy from the sun and is expressed in terms of full sun hours (i.e. 4 full sun hours = 4 hours of sunlight at an irradiance level of 1000 watts per square meter). Obviously different parts of the world receive more sunlight from others, so they will have more full sun hours per day. The solar insolation zone map on the right will give you a general idea of the full sun hours per day for your location.

How much will a system cost for my 2000 square foot home?

Unfortunately there is no per square foot average since the cost of a system actually depends on your daily energy usage and how many full sun hours you receive per day; And if you have other sources of electricity. To accurately size a system to meet your needs, we need to know what breakers are in your service and the AMP ratings.  Call (941)-812-3514 or contact us to have a Firebirdsolar Specialist help you calculate costs.

Can I use all of my normal 120/240 VAC appliances?

Yes.  Many older homes were not designed or built with energy efficiency in mind. When you purchase and install a renewable energy system for your home, you become your own power company so every kWh of energy you use means more equipment (and hence more money) is required to meet your energy needs. Appliances that operate at 240 VAC (such as electric water heaters, cook-stoves, furnaces and air conditioners) are, in most cases, impractical loads to run on solar. You should consider using alternatives such as LP or natural gas for water/space heating or cooking, evaporative cooling instead of compressor based AC units (unless the AC is above 14 seer) and passive solar design in your new home construction if possible. Refrigeration and lighting are typically the largest 120 VAC energy consumers in a home (after electric heating loads) and these two areas should be looked at very carefully in terms of getting the most energy efficient units available. Great strides have been made in the past 5 years towards improving the efficiency of electric refrigerators/freezers. Compact fluorescent lights use a quarter to a third of the power of an incandescent light for the same lumen output and they last ten times longer. These fluorescent lights are now readily available at your local hardware or discount store. The rule of thumb in the renewable energy industry is that for every dollar you spend replacing your inefficient appliances you will save three dollars in the cost of a renewable energy system to run them. So you can see that energy conservation is crucial and can really pay off when considering a renewable energy system.

What components do I need?

There are many components that make up a complete solar system, but the 4 main items are: solar modules, charge controller(s), batteries and inverter(s). The solar modules are physically mounted on a mount structure (see question 7) and the DC power they produce is wired through a charge controller before it goes on to the battery bank where it is stored. The two main functions of a charge controller are to prevent the battery from being overcharged and eliminate any reverse current flow from the batteries back to the solar modules at night. The battery bank stores the energy produced by the solar array during the day for use at anytime of day or night. Batteries come in many sizes and grades. The inverter takes the DC energy stored in the battery bank and inverts it to 120 VAC to run your AC appliances.

Where should I mount the solar modules and what direction should I face them?

If your site is in the Northern Hemisphere you need to aim your solar modules to the true south direction (the reverse is true for locations in the Southern Hemisphere) to maximize your daily energy output. For many locations there is quite a difference between magnetic south and true south, so please consult the declination map below before you setup your mount structure. The solar modules should be tilted up from horizontal to get a better angle at the sun and help keep the modules clean by shedding rain or snow. For best year round power output with the least amount of maintenance, you should set the solar array facing true south at a tilt angle equal to your latitude with respect to the horizontal position. If you plan to adjust your solar array tilt angle seasonally, a good rule of thumb to go by is latitude minus 15? in the summer, latitude in the spring/fall and latitude plus 15? in the winter. Most mount structures provide for a seasonal adjustment of the tilt angle from horizontal to 65?.

Should I set my system's battery bank up at 12, 24 or 48 VDC?

Our solar systems are designed and effective with 12V battery systems wired in 2VDC for smaller systems, and 24VDC for larger systems.  We find this is the most economical way to purchase batteries due to the 2VDC and 6VDC are harder to come by and are much more expensive. The 12V batteries are conveniently found at most auto parts stores.  The type of battery you are searching for is a deep cycle type battery with the highest AMP hr rating you can find.  You can expect up to 15 years of life from the batteries due to the fact that they are designed for charging and discharging thousands of cycles. With EcoStar’s exclusive battery controller technology will keep your battery in optimal operating condition at all times

Should I wire my home for AC or DC loads?

It depends on the size of the system and what type of loads you want to run. DC appliances are usually more efficient than AC since you don't have to worry about the loss through the inverter, but DC loads are typically more expensive and harder to find than their AC counterparts. Small cabin and RV systems are typically wired DC while most home systems are wired for AC loads exclusively. With improvements in inverter efficiency and reliability in the last 5 years, AC is the way to go for a home system. Another advantage AC has over DC is that the voltage drop for a 120VAC circuit is much less than a 12VDC circuit carrying the same power, which allows you to use smaller gauge wire.

Can I use PV to heat water or for space heating?

Yes, with our low voltage water heater element system that uses dump power for water heater

What type of solar module mounting structure should I use?

There are four basic types of mount structures: roof/ground, top-of-pole, side-of-pole and tracking mounts, each having their own pros and cons. For example roof mount structures typically keep the wire run distances between the solar array and battery bank to a minimum, which is good. But they also require roof penetrations in multiple locations (a potential source of leakage) and they require an expensive ground fault protection (GFP- device to satisfy article 690-5 of the National Electrical Code- NEC). On the other hand, ground mounted solar arrays require fairly precise foundation setup, are more susceptible to theft/vandalism and excessive snow accumulation at the bottom of the array. Next are top-of-pole mounts which are relatively easy to install (you sink a 2-6 inch diameter SCH40 steel pole up to 4-6 feet in the ground with concrete). Make sure that the pole is plumb and mount the solar modules and rack on top of the pole. Top-of-pole mounts reduce the risk of theft/vandalism (as compared to a ground mount). They are also a better choice for cold climates because snow slides off easily. Side of pole mounts are easy to install, but are typically used for small numbers of solar modules (1-4) for remote lighting systems where there already is an existing pole to attach them to. Last but not least are the trackers, which increase the daily number of full sun hours and are used for solar water pumping applications. Trackers are extremely effective in the summer time when water is needed the most. In the northern U.S., typical home energy usage peaks in the winter when a tracker mount makes very little difference as compared to any type of fixed mount (roof, ground or top-of-pole). In this situation, having more modules on a less expensive fixed mount will serve you better in the winter than fewer modules on a tracker. However, if you are in the southern U.S. and your energy usage peaks in the summer, then a tracker may be beneficial to match the time of your highest energy consumption with a tracking solar array's maximum energy output.

What does a power inverter do, and what can I use one for?

A power inverter changes DC power from a battery into conventional AC power that you can use to operate all kinds of devices ... electric lights, kitchen appliances, microwaves, power tools, TVs, radios, computers, to name just a few. You just connect the inverter to a battery, and plug your AC devices into the inverter ... and you've got portable power ... whenever and wherever you need it.

The inverter draws its power from a 12 Volt battery (preferably deep-cycle), or several batteries wired in parallel. The battery will need to be recharged as the power is drawn out of it by the inverter. The battery can be recharged by running the automobile motor, or a gas generator, solar panels, or wind. Or you can use a battery charger plugged into an AC outlet to recharge the battery.

Using an Inverter for Emergency Home Backup Power

A very simple way to use an inverter for emergency power (such as during a power outage), is to use a car battery (with the vehicle running), and an extension cord running into the house, where you can then plug in electrical appliances.

What size inverter should I buy?

Short Answer: The size you choose depends on the watts (or amps) of what you want to run (find the power consumption by referring to the specification plate on the appliance or tool). We recommend you buy a larger model than you think you'll need (at least 10% to 20% more than your largest load).

Example: You want to power a computer with a 17 monitor, some lights,
and a radio.

For this application, you would minimally need a 500 W inverter, and should give some thought to a larger one, as there will likely be a time when you wish you'd bought a bigger model ... in this example, you might decide you'd like to run a fan while you compute, or let the kids watch TV.

Longer Answer: Determine Continuous Load and Starting (Peak) Load: You need to determine how much power your tool or appliance (or combination of them that you would use at the same time) requires to start up (starting load), and also the continued running requirements (continuous load).

What is meant by the terms continuous-2000 watts and peak surge-4000 watts is that some appliances or tools, such as ones with a motor, require an initial surge of power to start up (starting load or peak load). Once started, the tool or appliance requires less power to continue to operate (continuous load)

Helpful formulas:

To Convert AMPS to WATTS:

Multiply: AMPS X 120 (AC voltage) = WATTS
This formula yields a close approximation of the continuous load of the appliance

To Calculate approximate Startup Load:

Multiply: WATTS X 2 = Starting Load
This formula yields a close approximation of the starting load of the appliance, though some may require an even greater starting load. NOTE: Induction motors such as air conditioners, refrigerators, freezers and pumps may have a start up surge of 3 to 7 times the continuous rating.

Most often the start up load of the appliance or power tool determines whether an inverter has the capability to power it.

For example, you have a freezer with a continuous load of 4 amps, and a start up load of 12 amps:

4 amps x 120 volts = 480 watts continuous
12 amps x 120 volts = 1440 watts starting load

You would need an inverter with peak-surge rating greater than 1440 watts.

FORMULA to convert AC Watts to DC Amps:

AC Watts divided by 12 x 1.1 = DC Amps
(this is the size vehicle alternator you would need to keep up with a specific load; for example, to keep up with a continuous draw of 1000 watts, you would need a 91 amp alternator)

Do I need Modified Sine Wave, or Pure Sine Wave?

Advantages of Pure Sine Wave inverters over modified sine wave inverters:

a) Output voltage wave form is pure sine wave with very low harmonic distortion and clean power better than utility-supplied electricity.

b) Inductive loads like microwave ovens and motors run faster, quieter and cooler.

c) Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines.

d) Prevents crashes in computers, weird print out, and glitches and noise in monitors.

e) Reliably powers the following devices that will normally not work with modified sine wave inverters:

Modified Sine Wave works well for most uses, and is the most common type of inverter on the market, as well as the most economical. Pure Sine Wave inverters (also called True Sine Wave) are more suited for sensitive electrical or electronic items such as laptop computers, stereos, laser printers, certain specialized applications such as medical equipment, a pellet stove with an internal computer, digital clocks, bread makers with multi-stage timers, and variable speed or rechargeable tools (see Appliance Cautions below).

If you wish to use those items with an inverter, then choose a Pure Sine Wave inverter. If you mostly want to run lights, TV, microwave oven, tools, etc, a Modified Sine Wave inverter is fine for your needs.

We often are asked if computers will work with Modified Sine Wave. It's been our experience that most (with the exception of some laptops) will work (though some monitors will have interference such as lines or a hum). However, if you have any doubt about any appliance, tool or device, particularly laptop computers and medical equipment such as oxygen concentrators, we recommend that you check with its manufacturer to be sure it is compatible with a Modified Sine Wave inverter. If it is not, choose one of our Pure Sine Inverters instead.

The difference between them is the Pure Sine Wave inverter produces a better and cleaner current. They are also considerably more expensive. You might find it practical to get a small Pure Sine Wave inverter for any special need you may have, and also a larger Modified Sine Wave inverter for the rest of your applications.

Appliance Cautions:

DO NOT plug small appliances into the inverter AC receptacles to directly recharge their nickel-cadmium batteries. Always use the re-charger provided with that appliance.

DO NOT plug in battery chargers for cordless power tools if the charger carries a warning that dangerous voltages are present at the battery terminals.

Not all fluorescent lamps operate properly with an inverter. If the bulb appears to be too bright, or fails to light, do not use the lamp with an inverter.

Some fans with synchronous motors may slightly increase in speed (RPM) when powered by an inverter. This is not harmful to the fan or to the inverter.

Certain rechargers for small nickel-cadmium batteries can be damaged if plugged into an inverter. In particular, two types of appliances are susceptible to damage:

DO NOT use an inverter with the above two types of equipment.

The majority of portable appliances do not have this problem. Most portable appliances use separate transformers or chargers that plug into AC receptacles to supply a low-voltage DC or AC output to the appliance. If the appliance label states that the charger or adapter produces a low-voltage DC or AC output (30 volts or less), there should be no problem powering that charger or adapter.

How do I hook up the Inverter? What size cable should I use?

The small inverters (400 watts and under) come with a cigarette lighter adapter, and may be plugged into your car's lighter socket (although you will not be able to draw more than 150 to 180 watts from the cigarette lighter socket). The small units also come with cables that can be clamped directly to a battery. If you want an inverter that will plug into your cigarette lighter, you must choose one that is 400 watts or less.

Larger inverters (500 watts and over) must be hard-wired directly to a battery. The cable size depends on the distance between battery and inverter, and will be specified in the Owner's Manual.

When connecting the inverter to the battery use the thickest wire available, in the shortest length practical.

General recommendations — Inverters 1500 watts and under: If battery and inverter are within 4', use #4 gauge AWG. If 4'-6', use #2. If more than 6', use #0 gauge wire (#0 gauge wire may require a 0 to 4 Gauge Adapter). The maximum length generally recommended is 10', and shorter is better. If you need more length, it is much better to put it on the AC side (as with an extension cord from inverter to appliance) than on the DC side.

Inverters over 1500 watts will require #1/0 or larger cable, in the shortest possible length.

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What type of battery should I use (automotive or deep cycle)?

True deep cycle only!

How long can I run the inverter on my battery?

Tip: Deep cycle (marine) batteries generally have the highest reserve ratings. They are also capable of withstanding repeated drains of power and recharging.

Tip: Engine start batteries should not be discharged below 90% charged state, and marine deep cycle batteries should not be discharged below 50% charged state. Doing so will shorten the life of the battery based on most battery manufacturers recommendations.

Note: If you intend to use power tools for commercial use, or any load of 200W for more than 1 hour regularly (between battery recharging) we recommend installing an auxiliary battery to provide power to the inverter. This battery should be a deep cycle type and sized to meet your run time expectations with the engine off. The auxiliary battery should be connected to the alternator through an isolator module to prevent the inverter from discharging the engine start battery when the engine is off.

How do I connect two or more batteries?

It may be advisable to operate the inverter from a bank of 12 Volt batteries of the same type in a parallel configuration. Two such batteries will generate twice the amp/hours of a single battery; three batteries will generate three times the amp/hours, and so on. This will lengthen the time before your batteries will need to be recharged, giving you a longer time that you can run your appliances.

You can also connect 6 Volt batteries together in series configuration to double the voltage to 12 volts. Note that 6 Volt batteries must be connected in pairs.

 

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Operating a Microwave with a Power Inverter

The power rating used with microwave ovens is the cooking power which refers to the power being delivered to the food being cooked. The actual operating power requirement rating is higher than the cooking power rating (for example, a microwave with advertised rating of 600 watts usually corresponds to almost 1100 watts of power consumption). The actual power consumption is usually stated on the back of the microwave. If the operating power requirement cannot be found on the back of the microwave, check the owner's manual or contact the manufacturer. Television and Audio Suggestions

Although all our inverters are shielded and filtered to minimize signal interference, some interference with your television picture may be unavoidable, especially with weak signals.

Here are some suggestions that may improve reception:

1. First make sure that the television antenna produces a clear signal under normal operating conditions (i.e., at home plugged into a standard 110AC wall outlet). Also insure that the antenna cable is properly shielded and of good quality.

2. Change positions of the inverter, antenna cables and television power cord.

3. Isolate the television, its power cord and antenna cables from the 12 volt power source by running an extension cord from the inverter to the TV set. Insure that any excess AC power cord is a distance away from the TV set.

4. Coil the television power cord and the input cables running from the 12 volt power source to the inverter.

5. Attach a Ferrite Data Line Filter to the television power cord. More than one filter may be required. These are available at electronic supply stores including Radio Shack (Radio Shack Part No. 273-105)

NOTE: Some inexpensive audio systems may discharge a slight buzzing sound when operated with an inverter. This is caused by deficient filters in the audio system. The only solution to this problem is using a sound system with a higher quality power supply.

 

Safety Warning: 110 Volts of current can be lethal. Improper use of a power inverter will result in property damage, personal injury, or loss of life. Please read and follow carefully the instructions in the Owner's Manual provided with every inverter for important safety considerations and precautions.

General Safety Precautions and Installation Tips: