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We also carry Matrix, B.P., G.E., Sharp, Sanyo, Uni-Solar, Mitsubishi, Photon, Suntech, ALPS Solar Photovoltaic Panels

Photovoltaic equipment is also widely known as P.V. or solar electricity. P.V. is the high tech side of the solar

industry. The photovoltaic industry is still in its relative infancy compared to the solar heating industry. If the

efficiencies of P.V. panels ever reach the efficiency of today’s heating collectors, and the costs are kept down,

the energy usage on earth will be dramatically changed.

The basic building block of photovoltaics is the cell. Cells are either round or square and convert sunlight to

D.C. electricity. The photons of light cause electrons to flow in the cell usually made of a doped silicon crystal. 

Each cell produces about 1/2 a volt of load. The current produced by each cell depends on its  size. Most cells 

manufactured today produce from two to four amps of current. Cells are normally wired  module or panel. 

Modules are usually wired to produce from 14 1/2 to 17 volts. These are called 12 volt modules because they 

are used to charge 12 volt batteries. A 12 volt lead acid battery is fully charged at about 13 1/2 volts and the  

module must produce a higher voltage than 12 volts to fully charge the battery. Two or more modules is called 

an array. Modules, like the cells that they contain, may also be wired in series, parallel or both.

How cells and modules are wired give a designer a wide range of voltage and amperage outputs. The majority

of applications in smaller projects are for 12 to 24 volt outputs with the amperage depending on how much

power is required. Although the photovoltaic effect was discovered over a hundred years ago, due to low

outputs and extremely high costs, applications for P.V.’s didn’t get going until the space program. Satellites in

earth orbits or deep space required a source of energy to power their transmitters and other equipment.

Photovoltaics, regardless of cost were the only viable option available to NASA engineers. The fruits of the

space pioneer’s development are harvested today in applications such as remote communications, powering

homes, pumping water, charging R.V. batteries and remote lighting. The effort in  bringing down the cost of

P.V.’s is opening new markets daily although payback cannot yet realized if low cost grid power (power

lines) are available. Today, it is smart to consider P.V.’s if power lines are more than 1/4 of a mile away.

Any application which requires electricity duing the daylight hours only is termed P.V. or Load Direct.

Powering pumps for crop irrigation or stock watering and pumps or blowers for solar heaters are some

common load direct applications. Recent innovations include the National Park Service using P.V. powered

blowers with solar air collectors in back country self-composting toilets. P.V. direct systems are simple, lower

in cost and virtually maintenance free.

If an application needs power available at night, lighting for example, batteries and a charge are necessary to 

store the electricity. Charge controls keep batteries from damage through overvoltage. The charge control cuts 

the power to the batteries when full charge is achieved. It is a must on all systems except ones with very large 

battery banks and small P.V. charging capacity. If the battery storage capacity is more than fifty times the P.V. 

daily output a charge control is not necessary. Batteries used with photovoltaic modules are called deep cycle. 

Deep cycle batteries are manufactured to be able to discharge most of their stored energy hundreds of times 

without damage. Shallow cycle (car batteries) are made to discharge only 10 to 20% of their energy (starting 

the car) each cycle. Deep discharging a shallow cycle battery even twenty to thirty times

not ruin it.

 We recommend that you use only deep cycle batteries with P.V. systems: 6 volt golf cart batteries are a true 

deep cycle battery with good availability. Nickel-Cadmium, mine car batteries and gel cells are also acceptable.  

If alternating current (120V. grid power) equipment, lighting or appliances are to be used a device called an 

inverter is required. Inverters convert the D.C. electricity from modules or batteries to A.C. electricity through 

electronic wizardry. Inverters are available from 100 to thousands of watts. Good inverters that waste a 

minimum of power cost about 1.00 per watt. Beware of cheap inverters, some of them can use up to 50 watts 

of power in the standby mode alone. A well made modified sine wave inverter is acceptable in most 

applications.

Powering remote homes can cost from five hundred to thirty thousand dollars depending on size and powering

requirements. Since the load of every house is different, the following can assist you in engineering a system to

fit your needs.

First, we do not design electrical systems by the size of the home or the number of

Electrical usage varies over a wide range depending living  

electricity as another.

We size photovoltaic systems based on your estimate of your electrical usage. The more accurate the estimate,

the better a system will fit your needs. You must know how much electricity each light, appliance or motor uses

and then estimate how much it will be used each day (24 hour period). All electrical devices are rated in watts,

like a 100 watt light bulb. If a motor or appliance has a nameplate that only gives volts and amps, the watts can

be calculated by multiplying the rated volts times the amps. The example sizing worksheet on the following page

should help you size a system. We will be happy to help you design a system ( for a small fee,) but you must    

estimate your electrical consumption for the system size to be accurate.

Conservation plays a big part in photovoltaic systems. The more you can conserve, the more you will save in

system design. More energy efficient lights and appliances almost always pay for themselves, even if they cost

more to begin with. It is almost always foolish to use photovoltaic modules for solar home heating systems,

hot water heating, and appliances for cooking. Refrigerators can be powered by solar electricity, but many

 people use propane refrigerators due to the high cost of super efficient refrigerators and the long pay back

 time.

The following page has a list of the average electrical usage of many common appliances. Remember, this is an

average usage and the consumption of electrical appliances can vary over a wide range. You should always use

the actual appliance wattage whenever possible.

A 20 WATT FLUORESCENT LIGHT IS EQUAL

COPYRIGHT 2001-2007 SCHWARK ELECTRICAL INC.
ALL RIGHTS RESERVED ERIC L. SCHWARK