Are the junction boxes on the top of the pan or underneath the pan?
Junction boxes can be mounted on either the top or bottom of the metal roofing pan that has a UNI-SOLAR®
PVL Module bonded to it. Junction boxes should not be exposed to direct sunlight, and are often installed under the
ridge trim.
Are there incentive programs available?
There is a $4.50 per Watt rebate available through the California Energy Commission (CEC) for systems that receive a bill
from the three major investor owned utilities (PG&E, SCE, and SDG&E). This rebate will pay up to half the cost of
a system and also includes other tax incentives. There is also a $750 rebate available from the CEC for batteries. For
more information on local and federal incentives, visit www-solar.mck.ncsu.edu , www.eren.doe.gov , www.nrel.gov, www.dsireusa.org,
or www.energy.ca.gov/renewables .
Can any roof accommodate solar panels?
Solar access is the primary requirement. The orientation, slope, size and shape are also determining factors. Southern
orientation and slopes from flat to 60 degrees can accommodate PV roofing. Presently there are a variety of PV laminates
available from UNI-SOLAR® ranging in size from 4 1/2' (31 watt) to 18' (136 watt).
Wiring for these laminates is either in the ridge cap or the eave soffit. The length of the roofing pan must be at least 3"
longer than the length of the PV laminate. Vents, chimneys, skylights and other roof penetrations, as well as shaded
areas from adjoining buildings or trees must be avoided.
Can I use the standing seam metal roofing in heavy snowfall areas?
Yes, the UNI-SOLAR® standing seam metal roofing products are integrated into the
building and can tolerate extremely heavy snow loads without any damage. In very heavy snow load areas, it is recommended
that homeowners use the structural standing seam product ("Snap-Seam" roofing). A "Snap-Seam" metal roofing pan profile
has as a tighter seam, and there is less chance of water ingress.
Can I walk on the pans and solar material?
It is not recommended. If you must walk on the solar material (the solar laminate is bonded to the metal pan), we
recommend your shoes are clean and soft-soled. The top surface of the modules can be slippery if wet.
Do I need blocking diodes?
Blocking diodes are required to prevent battery energy from leaking into the modules at night when the modules are not
producing any energy. Normally, a voltage regulator will have a built-in blocking diode or "night time disconnect" circuit.
Blocking diodes are commonly used in PV arrays to prevent one string of modules from feeding energy into another string of
modules. If there are special shading problems at the site, the use of blocking diodes within the array can increase
the total amount of energy going into the battery over the course of one day. If there are no special shading problems
at the site, blocking diodes can decrease the total amount of the energy going into the battery over the course of one day
because of the voltage drop across the diodes.
Do I need fuses?
Yes, the NEC requires that each series string of modules be fused. This is true even if there is only one module
in your “string”. Even if it was not an NEC requirement, fusing paralleled strings of modules is a prudent
strategy. It is less expensive to replace a fuse than it is to replace a module that was exposed to excessive current
in an unexpected ground fault situation.
Does the output of my array depend on my location?
The amount of solar radiation received in various cities and regions of the United States has been compiled by the National
Renewable Energy Laboratory(NREL). The most convenient summary of solar radiation and climate data can be accessed at:
www.solstice.crest.org/renewables/solrad
The average solar energy is given in units of solar kWh/m2/day for each month or averaged over a year. The annual
averages are given for some cities below. These values also represent the average number of peak sun hours per day at
each location. To obtain the average daily electrical DC output in Wh, multiply the number of daily peak sun hours with
the number of installed Watts in your array. The annual average DC output is 365 times larger. Depending on your
choice of inverter, the AC energy output from a PV system without battery (i.e. "Line Tie" PV System) is approximately
15% less than the DC output.
In order to optimize performance in the winter, a flat-plate collector facing south should be tilted at a fixed angle equal
to the latitude of your site plus 15 degrees.
Example 1 - If you live in Boston, MA, your average number of peak sun hours is 4.4 hours per day or 1600 hours per year.
If you have a house that uses 6,000 kWh (AC) per year, you need to generate 7,060 kWh (DC) per year when your PV system
operates at 85% efficiency. The number of Watts of solar electric panels you need is 7,060 ÷ 1,600 = 4.4 kW.
Example 2 - In a desert area such as Phoenix, AZ, the average number of peak sun hours is 6.3 hours per day or 2,300 hours
per year. A house that uses 6,000 kWh (AC) per year needs 7,060 kWh (DC), assuming again a PV system efficiency of 85%.
The number of Watts of solar electric panels you need to install is 7,060 ÷ 2,300 = 3 kW.
Example 3 - In Denver, CO, the average number of peak sun hours is 5.3 hours per day or 1,930 hours per year. A south
facing roof with an area of 750 ft2 can accommodate approximately 4 kW of shingles or panels. This system can generate
4 x 1,930 = 7,720 kWh (DC) per year, or with a 85% efficient PV system, about 6,600 kWh (AC) per year.
How can I estimate the size of the solar roof I need?
It takes about 180 ft2 of roof area with solar access per kW of electricity generated.
How can I save more money on my PV roof?
The first step in considering a PV roof is to do an energy audit that will suggest the least expensive conservation measures
that will increase the efficiency of energy used in your building. Energy efficient lighting and appliances, insulation, weather
stripping and insulating windows will quickly pay back the investment in energy savings and reduce the cost of the PV array
necessary to serve your needs. After you have maximized your conservation and efficiency efforts, you should then look for
rebate incentives and tax breaks available in your state. A good PV system designer should be then hired to help you put together
an efficient solar energy system
How do you install the metal roofing?
Standing Seam metal roofing products have been designed to be installed by a licensed metal roofing installer. Usually,
the installer will bring all other components for the metal roof installation. These include clips, trim pieces, screws,
sealant, etc. Typically, the metal roofing system is a structural product that is installed over purlins, or over a
roof deck. The wind load ratings exceed 90mph for all products and can be as 160mph if mounted on a solid deck or purlins
that are no more then 3 feet (1 meter) apart.
How do you install the solar shingles?
An installation manual is included with the purchase of all solar roofing products. In general, a roofing contractor
will begin by following conventional roofing installation procedures, until the solar shingle installation. Using a template
provided by United Solar Ovonic, the roofer will then mark and drill holes for the solar shingle wiring to be pulled through
the roof. After the solar shingles are installed to match the course of the conventional shingles, an electrical system installer
will wire the solar shingles together in the space below the roof, and then wire the array of shingles to the combiner box.
The electrical contractor will take the wires from the combiner box and run them down to the power conditioning equipment
(charge controller, meters, system disconnect switches, fuses, inverter) and then connect this equipment to the batteries
and/or AC Service Panel(s).
How many kW of solar electric roofing will I need?
An ideal system provides exactly the amount of energy needed on an annual basis. With a PV system operating at 85% efficiency,
a typical home can manage 50-100% of their energy needs with a 2.5 to 7 kW(DC) PV system.
How much energy do I need?
If you are connected to a utility you will be able to look at your bill and find out how many kWh you use per day, per
month and per year. If you are constructing a new building you will have to estimate your demand based on the size of the
home and the efficiency of the appliances you purchase.
What are the voltages of the different size metal roofing modules?
The smaller PVL modules provide operating voltage of 16.5V, while the larger modules provide operating voltage of 30-33V.
The modules can be connected in series up to 600V open circuit.
What components make up a complete system?
Combiner boxes to combine the wires coming from different modules. Inverters to change direct current to alternating house
current. If storage is desired, charge controllers and batteries will be necessary. You will also need both DC &
AC system disconnects.
What charge controller do I use?
Any number of controllers can be used. The most important things to consider when buying a controller are; system
voltage, maximum array amps and controller features. The controller must be able to handle the nominal system voltage
as well as the array short circuit current. It is also important that the system owner review the features available
on the many controllers available today. Many controllers have pulse-width-modulation control, metering to assist the
owner in understanding the system, and low voltage disconnects to protect the batteries from excessive discharge, etc.
What is a combiner box?
A combiner box is an electrical box (NEMA1 for indoor locations, NEMA 3R for wet locations and NEMA 4X for outdoor locations)
where the positive and negative wires from strings of modules can be combined, or paralleled together. The combiner
box will have 4 to 12 input spaces and 2 large output lugs for a single positive and single negative wire to be connected
and then run down to the balance of system components (inverters and batteries). Frequently the combiner box will include
fuses. Many combiner boxes for high voltage systems will also include diodes and associated heat sinks.
What is an inverter?
An inverter converts the direct current (DC) output from the PV array to alternating current (AC) output required for the
home. Depending on your choice of inverter, the AC energy output can be approximately 6-10% less than the DC output.
The inversion efficiency for this inverter is considered to be 90-94% efficient.
What kind of solar system do I need?
There are five different types of solar electric installations.
Low Voltage Direct Current (DC) System : For a small cabin without grid connection and low demand for electricity,
a low voltage direct current (DC) system makes the most sense. This system includes a solar array under 1 kW, charge controller
and a small battery pack.
Independent Alternating Current (AC) System: For a home without grid connection, an independent alternating current (AC)
system requires a larger array, over 1 kW, a charge controller, a large battery pack and an inverter, which changes DC generated
by the photovoltaics to 110V or 220V AC house electricity to run standard household appliances.
Net-metered system: The most inexpensive grid-connected system is a net-metered system without batteries. This system includes
an array large enough to satisfy most of the electric needs of the house and an inverter that synchronizes with the utility
and can run the utility meter backwards when your solar array produces more electrical energy than you are using in your house.
Battery Pack: If there is concern about rolling blackouts, a small inexpensive battery pack may be added to a grid-connected
system and only used in the case of a utility outage.
Backup System: If there is concern for long utility outages on a grid-connected system, then you may want to use the utility
as a backup battery charger and put in a system similar to an independent AC system with a large battery pack.
What size fuses do I use and where do I put them?
All the PVL products require an 8-Amp fuse. Other UNI-SOLAR® modules have
different size fuses. Fuses can be located in the module junction box (in line fuse and fuse holder) or they can be
located in a combiner box where array strings can be parallel connected together.
What's the highest voltage system I can create?
Presently, the highest voltage system that can be put together using UNI-SOLAR®
modules is 600 volts. This means that you can connect up to twenty-two PVL-68 or eleven PVL-136 modules in series.
What will my solar electric system cost?
The installed cost for small systems (less than 5 kW) without batteries runs between $ 8 and $12 per Watt. For larger systems
(over 10 kW) without batteries the installed cost is between $6 to $10 per Watt. Depending on how many hours one needs to
use the battery, the battery size is determined. This can increase the cost of the system by $1.50-$3.00 per Watt.
For a small battery pack $1.50 per Watt should be added. For a large battery pack $3 per Watt or more should be added.
