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Solar Terms and Acronyms

Here are some solar terms and what they mean

If you come across any other terms let me know and I'll add them. Also see http://en.wikipedia.org/wiki/Solar_cell

Solar- this is the Sun

Solar cell- One single 3 to 4 inch cell of a solar panel. It usally only make 1.5 volts at .5 ampers. But connected in series with many cells it can make a panel with a lot of power. There are many types of cells. See wkipedia above for details.

Solar Panel- This is one panels that is about 2 foot by 3 feet with many cells on it all connected in series. A typical panel is 12 volts at 4 amps. There are many types and variations but this is typical. A solar panel cost about $4 a watt in 2008-2009. The prices have been going down very slowing since they were first made comercially in 1954 by Bell Labs.  Panels were 5 % efficient in 1954 and are now 10-22 % efficient depending on type and material. The theoretical limit is about 32% but some very efficient panels don't last as long. The real progress is $ per watt.

 Solar array- This is a group of panels connected togehter to make a higher voltage. An example is 4 panels of 12 volts each connected together in series to make 48 volts.

STC- Standard Test Conditions. This is how panels are tested and rated so you can compare. Your results will vary since your location will vary.

VOLTS- This is a basic electricity measurment of the potential of energy. In a solar panel it is normally DC voltage and in your home it would be AC volage. Most panels are 12 volts DC , most homes have 120 volt 60 hertz AC outlets with a higher 240 volts for an electric dryer or stove. In Europe they use 230 volts AC at 50 hertz.

AMPERAGE- This is the amount of flow in an electric circuit. Most single panels of Solar PV are about 12 volts DC at 4 amps. A home outlet is 120 volts limited to 15, 20 amps or even 30 amps.

KwH- Kilowatt Hour. This is how you get billed for electric use by your power company. 1 KwH is 1,000 watts used for 1 hour. It's basic math. Also if you used 100 watts for 10 hours that is also 1 KwH.

PV- "photovoltaic" comes from the Greek φώς (phos) meaning "light", and "voltaic", meaning electric

Inverter- This changes Solar panel PV power that is DC direct Current into AC Alternating current. They cost about $1 a watt in 2009 and have 10 year warrenties. Most are efficient at 95% or better.   A new design by enPhase uses a small inverter on each panel. Panels must be 100-300 watts and you can connect up to 4 together, they produce AC right from the small inverter so all wires must be in conduit.  Most inverters convert DC to 240 volts AC. A few like my advanced Energy make 120 volts AC.

Inverters and Batteries- Most grid tied systems don't have any batteries. A few offer that option like Outback. If power goes out and you don't have batteries your solar system shuts down so it won't put power out on the line. If it has battery back up it opens the street side AC line and runs a few connections in your home. If power comes back on it will sense that and connect back after it is stable for 1 or more minutes.

OFF GRID and ON GRID-  A few people live far away from power lines and are 100% off GRID. They always need batteries for nights and cloudy days. They have to monitor their power use and never run low. This is more expensive than a GRID tied system becuase of the battery cost and losses during charging and converting to and from DC and AC. Most batteries are old lead acid types and require maintenance and balancing.  

Connections- The panels are connected with quick connectors on most new panels, older ones have wire junction boxes.  These are water tight and keyed for positive to negative inter connections. This makes it fast and easy. At the inverter they need to have connections to the main power connections that may be standard electric cal connections or a keyed quick connect. All of the AC connections are standard electrician connections.

 FUSES- These are devises made to open if the AC or DC is over a safe limit. Fuses for AC and DC are very different. Be sure to use the correct fuse at the right value. These are very important for Safety ! An AC fuse doesn't require a large gap to be open, a DC fuse needs a large gap so the DC power will not jump and arc across the open. Get the right type for each voltage , AC or DC and the correct amperage. Be safe.