Photo Voltaics (PV)

Two ways to gather energy from the sun

-Thermal Solar

-Photovoltaics

“Photovoltaics”—derives from the Greek “Phos” meaning light, and “Voltaic” meaning electricity.

*Solar energy has been used as far back as 7th century B.C.

*It first entered the U.S. in 1954 with only a 4% efficiency in silicon photovoltaic cells.

*In 2001 three countries were very dedicated to this form of energy.

*These three countries supplied 85% of PV energy, the U.S. is only responsible for 15%.

The basic principle behind the technology is light energy in the form of photon particles are captured by energy absorbing materials like silicone.

Once captured, negatively charged electrons split away from the atom and flow in one direction, the corresponding positively charged energy is directed in the opposite direction.

they are:

• Monocrystalline panels • Polycrystalline panels • Thin film panels • Hybrid panels (which are

monocrystalline with an embedded layer of thin film)

Monocrystalline panels get their name from the fact that the silicon wafer used to make is cut from a single crystal of silicon.

High degree of purity Sliced very thinly to make wafers.

- highest efficiency of any cells on the market under

- high efficiency means smallest footprint for their output, so you can

- maximize power output when roof space is limited.

These cells are cut from an ingot of melted and re-crystallised silicon

end to be slightly less efficient for the same size cell.

cost less

Polycrystalline cells are slightly less efficient than monocrystalline cells

more roof space to produce the same output capacity.

Thin film silicon cells are made up of silicon atoms in a thin layer

absorb light more readily than crystalline so cells can be thinner.

For this reason, amorphous silicon is also known as

‘thin film’ photovoltaic (PV) technology.

Thin film offers the best shade tolerance of any solar technology.

When compared with other types of panels, thin film performs best under hotter.

1977-Jimmy Carter installs Photovoltaics on the White House

President Reagan had them removed

1985-20% EfficiencyTo day-42% Efficiency

Helping the EnvironmentLocal & Federal Tax IncentivesPotential To Earn MoneyUtility Rebates Based on Installed KW

*The Regions Climate

*Desired amount of Supplemental Energy

*Funding For Initial Cost of System

*Eligibility For Incentives

*Site Restrictions

*Community Restrictions

*Local Utility Buyback Rates

*A 5KW system can potentially supply a conventional home with power in a climate with average solar gains

*A 2KW system can potentially supply a energy efficient home with power in a climate with average solar gains

*Partial supplementary energy is also a good choice.

In 2008, the installed cost of a residential PV system in the United States ranged $8 to $10 per installed watt before government or utility incentives.

*A 2 KW system fully installed could cost on average between $16,000 to $20,000.

*A 5 KW system fully installed could cost on average between $30,000 to $40,000.

*Utility rebates on average are between $300 to $400 per KW installed.

*The Renewable Energy and Job Creation Act will give a 30% tax reduction on cost of system.

*An average home with a 5-kW system in southern Arizona

*Energy from the PV system = (5-kW) x (2100kWh/kW-year) = 10,500 kWh/year

*Energy Bill Savings per year = (10,500 kWh) x ($0.10/kWh-buy back) = $1,050/year

*Payback of system with no incentives = $30,000 initial cost/$1,050 = 28.6 years

Does the Pacific Northwest Have Good Solar Potential?

The Answers is…….

Yes

Even west of the Cascades*Oregon’s Willamette Valley receives

as much solar energy annually as the U.S. average –

as much over the course of the year

as southern France and more than Germany

Solar potential, not every building site will be suitable for a solar installation. The first

Some questions you should ask are:

* Is the installation site free from shading by nearby trees, buildings or other obstructions?

*Can the PV system be oriented for good performance?

* Does the roof or property have enough area to accommodate the solar array?

*If the array will be roof-mounted, what kind of roof is it and what is its condition?

*Solar modules are usually mounted on roofs. If roof area is not available, PV modules can be pole-mounted, ground-mounted, wall-mounted or installed as part of a shade structure

*Photovoltaic arrays are adversely affected by shading.

*A well-designed PV system needs clear and unobstructed access to the sun’s rays from about 9 a.m. to 3 p.m., throughout the year.

*Even small shadows, such as the shadow of a single branch of a leafless tree can significantly reduce the power output of a solar module.

*Shading from the building itself – due to vents, attic fans, skylights, gables or overhangs – must also be avoided.

*In northern latitudes, by conventional wisdom PV modules are ideally oriented towards true south.

*Deviations between magnetic and true south, referred to as magnetic declination, vary by location.

*Orientation of a roof does not need to be perfect.

*Solar modules produce 95 percent of their full power when within 20 degrees of the sun’s direction.

*Roofs that face east or west may also be acceptable.

*Optimum orientation can be influenced by typical local weather patterns.

*Western Washington and Oregon frequently have a marine layer of fog that burns off by late morning and so have better solar resource after noon than before noon.

*West of the Cascades, the maximum power is generated with a southwest orientation.

Broadly classified by answers to the following questions:

Will it be connected to the utility’s transmission grid?

Will it produce alternating current (AC) or direct current (DC) electricity, or both?

Will it have battery back-up?Will it have back-up by a diesel, gasoline

or propane generator set?

*Most new PV systems being installed in the United States are grid-connected residential systems without battery back-up.

*Many grid-connected AC systems are also being installed in commercial or public facilities.

*Two types:

• Grid-connected AC system with no battery or generator back-up.

• Grid-connected AC system with battery back-up.

Solar Modules*The heart of a photovoltaic system is the solar module. Many photovoltaic cells are wired together by the manufacturer to produce a solar module.

*When installed at a site, solar modules are wired together in series to form strings. Strings of modules are connected in parallel to form an array.

Rated Power *Grid-connected residential PV systems use modules with rated power output ranging from 100-300 watts. *Rated power is the maximum power the panel can produce with 1,000 watts of sunlight per square meter at a module temperature of 25oC or 77oF in still air. *Actual power output will almost always be less.

PV System Voltage *Modern systems without batteries are typically wired to provide from 235V to 600V.

*In battery-based systems, the trend is also toward use of higher array voltages, although many charge controllers still require lower voltages of 12V, 24V or 48V to match the voltage of the battery string.

M stands for Max GOooooooo Max

*Solar heaters, or solar thermal systems, provide environmentally friendly heat for household water, space heating, and swimming pools.

*The systems collect the sun’s energy to heat air or a fluid. The air or fluid then transfers solar heat directly or indirectly to your home, water, or pool.

Size of system

*20 square feet (2 square meters) of collector area

for each of the first two family members. For every additional person, add 8 square feet (0.7 square meters) if you live in the Sun Belt area of the United States, or 12 to 14 square feet (1.1 to 1.3 square meters) if you live in the northern United States.

Size of TankFor active systems, the size of the solar storage tank increases with the size of the collector—typically 1.5 gallons per square foot of collector.

A small, 66-gallon system is usually big enough for one to three people; a medium-size, 80-gallon system works well for a three- or four-person household; and a large, 120-gallon system is appropriate for four to six people.

Integral collector-storage passive systems

These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs.

Thermosyphon systemsWater flows through the system when warm

water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank.

Integral collector-storage systemsAlso known as ICS or batch systems,

one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water.

Should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather.

Evacuated-tube solar collectorsThey feature parallel rows of transparent

glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin's coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications

Flat-plate collectorGlazed flat-plate collectors are insulated,

weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers.

Requirements *Need a substantial structural base

*A structure must be a minimum distance from the base of tower of 1.5 times the height of the tower.

*Does not work well when the wind doesn't blow

*They make noise.

*Can harm birds. (But so do cats)

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