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Steel Building Erectors Article: FIELD TECHNIQUES: The Solar Equation
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ERECTORS ARTICLES - FIELD TECHNIQUES: The Solar Equation

The Solar Equation
AVAILABLE SOLAR TECHNOLOGY + ROI = RESULTS

AS THE METAL roofing industry continues to further promote the use of integrated solar options, metal roofing installers may run into many challenges. There are four steps that may help sell a solar roof system: first is to learn how the systems work and understand the terminology, such as solar efficiency, de-rates and thin film versus glass; second, learn the financial model; third, align your company with tan electrical partner; and, finally, track results in real time

Clients want solar to achieve a triple bottom line impact: people (societal benefit), planet (environmental benefit) and profit (financial benefit). The following basic information will help contractors, distributors and installers prepare for a successful solar roof presentation and installation.

PRACTICAL EXAMPLES
First, identify what type of structure you are dealing with. Building factors to take into consideration include building height, roofing system, exposure (south/southwest is ideal) and shading potential. For electrical service, consider usage and voltage. Finally, consider cost of energy and possible incentives for utility considerations. A good resource for this can be found online at www.dsireusa.org.

Solar energy is measured in watts. A kilowatt equals 1,000 watts. Kilowatts are measured by the hour and expressed as kilowatt-hours (kWh), or 1,000 watts acting over a period of 1 hour. Finally, a megawatt is 1,000 kilowatts and a megawatt-hour is one megawatt acting over a period of one hour.

The system size depends on how much roof area is available. Here is an example of a simple approach when using 20 standing seam panels that are 20 feet in length and have a south/southwest exposure.

    > Each photovoltaic laminate thin-film panel produces 144 watts - 20 (x) 144 watts = 2,990 watts of DC power
    > 2,880 watts divided by 1,000 = a 2.8-kilowatt system

Depending where your project is located, you will need to figure out your solar radiance, which is how much average solar energy production the system will achieve. As an example, the average solar radiance for eastern Pennsylvania is 4.4 hours.

    > (2.8 kilowatts x 4.4 solar radiance multiplier) = 12,672 watts daily average or 12.6 kilowatts
    > 12.6 kilowatts x 365 = 4,625 kilowatt annual energy production of DC power

Solar systems are sold by direct current (DC) power. Incentives are calculated in DC, as well. To convert the DC to alternating current (AC), you need to use an inverter, which needs to be sized properly to meet the system requirements. For the size above you would use a 2,800-watt inverter.

BUILDING FACTORS TO TAKE INTO CONSIDERATION INCLUDE BUILDING HEIGHT, ROOFING SYSTEM, EXPOSURE (SOUTH/SOUTHWEST IS IDEAL) AND SHADING POTENTIAL.

Converting to AC energy production:

    > A de-rate factor is calculated for wire loss and conversion loss going from DC to AC; 80 percent de-rate factors are commonly used.
    > 2.8 kilowatts x 80 percent = 2.3 kilowatts x 4.4 = 10.1 kilowatts AC production = 3,700 kilowatts of AC annual production.

When selling solar, the panel's solar efficiency often is the subject of questions. Solar efficiency is a ratio of capacity versus space, not an efficiency of production or ability to produce electricity efficiently.

Solar efficiency is a power density ratio that's calculated in a controlled lab; it's expressed as a percentage. On a sunny day when the sun's rays shine through a clear atmosphere and perpendicular to the Earth's surface (e.g. at noon on the equator on the equinox): Defined as 1,000 watts of sunlight per square meter of panel. Solar panel power efficiency ratings are almost always the power they would produce in these conditions when operating at a temperature of 25 C and at the maximum power voltage. For example, a solar panel that is 15 percent efficient takes in 150 watts per square meter.

NET METERING ENABLES CUSTOMERS TO USE THEIR OWN GENERATION TO OFFSET THEIR CONSUMPTION OVER A BILLING PERIOD BY ALLOWING THEIR ELECTRIC METERS TO TURN BACKWARDS WHEN THEY GENERATE ELECTRICITY IN EXCESS OF THEIR DEMAND.

FINANCIAL MODEL
Selling a solar roof system is 85 percent financial sale and 15 percent technical; the numbers have to add up and make sense. Here are a few questions you may encounter when discussing solar:
    > "What's my return on investment in terms of years?" The answer to this will vary, based on region, installed cost per watt and available incentives.
    > "Will the appreciation in property value affect our tax assessment?" If a property owner installs an active solar energy system, the system will not be assessed on the current property. Any other improvements constructed to support the system--for example, a new patio or carport--are not included in the exclusion and will be assessed at current market value as of the lien date or date of completion of the new construction. When the property undergoes a change in ownership, however, the active solar energy system becomes assessable along with everything else on the property.
    > "What are the first-year utility savings, average monthly utility savings, average annual utility savings and 25-year utility savings?" You'll need to know the system sizing and the annual energy consumption of the property.
    > Will I be able to sell my power to the grid-also known as net metering? Net metering programs serve as an important incentive for consumer investment in renewable energy generation. Net metering enables customers to use their own generation to offset their consumption during a billing period by allowing their electric meters to turn backwards when they generate electricity in excess of their demand. Currently, net metering is offered in more than 35 states. (See map above.)
    > Are solar Renewable Energy Credits available? Visit www.srectrade.com to check.

Be sure to align yourself with a good electrician, as well as a good solar supplier. A solar layout and permit package, which will be supplied by the solar roof manufacturer, is necessary. This will be used for the utility company, building inspectors and code officials. Be sure to make demands on your supplier to have a technical representative on the project site for your first install, which is common practice.

Finally, be able to track the output in real time. Put your money where your design is and make sure your system can be monitored using a Web-based dashboard. The dashboard brings the system to life and you hook up the system through the inverter's data monitoring card with an Internet connection. This gives the owners something to look at, send to their friends or put in the lobby of their building tracking everything from energy output daily, weekly and monthly to carbon offsets, and even barrels of oil and gallons of gas offset.

Solar roof systems are complex, but if you take the time to understand the basics it may lead you to your first install, thereby earning profit, expanding your business and helping the environment.

Brian Partyka is the chair of the Sustainability Council and a board member of the Metal Construction Association, Glenview, Ill. He has been training contractors about the benefits of solar roof systems since 1999. He also is president and partner of Ivyland, PA.-based Drexel Metals LLC.








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