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Solar PhotoVoltaics (PV)

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Solar PhotoVoltaics (PV)

Solar photovoltaics (PV) systems turn sunlight into an electrical current. This power can be stored in batteries, used as Direct Current (DC) or converted to Alternating Current (AC) for household or industrial use, or feed directly into the electrical grid.

A system generally consists of an array of solar modules (panels), bracket support system, a charge controller, a possible battery bank system , a DC (direct current) load centre, a fuse or breaker system, an inverter and an AC load centre. As production of panels and their associated electronics has rapidly expanded, the cost per unit has been declining. With the incentives now offered by many regional forms of government, implementing a P.V. system can not only benefit the environment but can also benefit your bank account.

Let's take a look at some of the parts of a system.

PV Household

 

In this system, the solar array charges a battery bank which then provides power to an AC-DC Inverter. The inverter shown, connects to two power panels. One panel is used just for critical loads in the house (furnace ignition, freezer, fridge). The other connection, goes through a disconnect switch and into the electrical box for the house. This provides power to the house and may feed excess power into the local electrical grid if permitted. The disconnect switch ensures there is no power sent out onto the grid when the grid is down. Otherwise, personnel working on the grid could be in for a shock!

Solar Module or Array - produces DC current when the sun shines

Over current Protection - usually fuses - disconnects the array should there be a short.

Charge Controller - manages the current flowing to the batteries and any DC load. Ensures the maximum power is obtained from the solar modules.

Batteries - store the power for when it's required.

DC-AC Inverter - converts DC power to standard household AC current. May have features to cut power with grid fails, or to supply power to several separate load centers.

Household Electric Meter - may run forwards and backwards if "Net Metering" is permitted. With Net Metering, excess power can be "stored" on the grid till required.

Traditional Solar Module

GE 200 Watt

Usually made from silicone wafers, a module is rated in both WATTS and voltage. The peak wattage of each module is added together to determine the total output of the array. The voltage output becomes important when considering the distance required to connect to the DC load (controller/batteries) and the voltage that can be handled by the inverter.

 

The G.E. 200 watt module to the right, has the following features...

Features

  • 54 poly-crystalline cells connected in series
  • Peak power of 200 watts at 26.3 volts
  • Designed for optimum use in residential and commercial grid-tied applications
  • 25-year limited warranty on power output, 5-year limited warranty on materials and workmanship*
  • Pre-wired junction box with MC Connectors
  • Output power tolerance of +/- 5%
  • Robust, clear anodized aluminum frame with pre-drilled holes for quick installation

Solar PV Technology Advances

Nanotechnology & Thin Film

First Solar successfully manufactures a thin film solar panel and sells exclusively to large scale installations. Their price per watt for modules in 2007 was approximately $2.00 which they hope to reduce to just $1.00 per watt in 2008.

INNOVALIGHT is just one of several companies developing a thin film version of silicon, vs. the silicon wafer. A thin film solar PV system, reduces overall silicon use, from 15 grams per watt of electricity, down to just 0.04 grams. Using nanotechnology, Innovalight is working to produce an "ink" like version of silicon that can be printed on material using inkjet technology. This process could reduce the cost per watt by a factor of 10. They hope to have full production in place by end of 2009 and be producing 100 megawatts at a unimaginably cheap price of 30 cents per watt.

Miasolé manufactures a thin-film photovoltaic cell that consists of an ultra-thin layer of photo active material (copper indium gallium diselenide, or CIGS) on a stainless steel foil only 50 microns thick. It can easily be used in PV modules or incorporated into building materials like membrane roofing. Each production run, produces several square miles of solar foil! Estimates of cost per watt INSTALLED, average $2.00. A traditional Silicon Module system can cost $10 per watt installed.

Concentrators

Solar sunflower by Energy Innovations

Energy Innovators have combined the world's most efficient solar cell, with custom designed lenses, to provide more energy per watt installed than traditional PV panels and do it at a substantial discount. The Sunflower is scheduled to be available to commercial customers in 2008.

Starsolar light refection

StarSolar, a 2007 start-up company, plans to trap the sunlight inside the solar cell, thus greatly increasing the absorption and energy produced.

 

 

Balance Of System Componets Trace charge controller

 

Controllers/Charge Regulators

Charge regulators control the amount of charge that is sent to the battery bank, to protect it from overcharging and completely discharging. Some controllers include a maximum power point tracker (MPPT) for PV modules, in order to get the maximum amount of power out of the array. An MPPT controller can get 10% more power out of your array in the summer and 30% more power in winter. These gains are generally higher for panels with high voltage peak (Vp) values.

 

Inverters

Balance of System

Converts DC power into AC power. About 10% of the energy is lost in the conversion process. The input voltages range from 12, 24, 48 and up. Smaller units (under 1000 watts) may have only one input voltage and may produce a modified sine wave. AC produced using a modified sine wave may not power sensitive electronic equipment such as computers or laser printers. Higher end inverters usually produce a true sine wave version of AC. Higher end inverters also come with a range of additional features including remote meters, automatic generator start-up, built-in charge controllers, etc. Inverters are also designed specifically for GRID connection or for off-grid use. Grid connection inverters have the ability to synchronize with the utility (grid) power and will have automatic shut-off should the grid power be interrupted. This picture shows my Sunny Boy 4kW Grid-tie inverter with an automatic DC Disconnect. The box to the left is a Midnight Solar Combiner Box. It holds the 600 vDC fuses for each string of solar panels and combines all stings together to feed the inverter.

See a home Solar Panel Installation here: Solar Panel Installation

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