Issues With PV Cables on Residential Rooftops

Cable management is difficult with rooftop PV installations because the array is coplanar to the roof and it is difficult to see and access the cables once each module is in installed. There are two major issues that occur with these types of installations.

  1. Unprotected PV cables can be damaged by squirrels or other animals that will nest under the array and claw or chew the cables and connectors.
  2. Obstructions under or around the edge of the PV array can hinder drainage and cause leaks into the roof.

To address issue #1, good wire management is one of the best available defenses against squirrels and other nesting creatures. The NEC states that USE-2 (PV wire/cable) must be secured within 24” of a junction box and then every 24” of length. While this is adequate for other installations, roof mounted arrays need better support and protection for the cables. Every 12” to 18” is minimal to prevent drupes in the cable.

The picture below is of a ground mounted array where wire management is easy to achieve. It is exceedingly difficult to achieve this with a coplanar roof mounted PV array. Even with this level of wire management, a squirrel can still chew on the cables; they are still unprotected.

Underneath view

Wire management methods vary depending on the racking manufacturer but none of them fully protect the PV cables from squirrel chewing damage. Here are a few methods.

SnapNRack
SnapNrack uses their open rail system for wire management. The plastic clips secure the cables into the rail trough.

 

Generic cable clips that attach to the module frame.

Generic 1Generic 2

 

Cable ties (zip ties) These are convenient to use but they must be rated for the lifetime of the array.

Cable tiesCable ties

The problem with zip ties is with their strength and usage rating. The typical black zip tie may not have a sufficient rating for the lifetime of the PV module.

Extreme UV

Another code requirement is the minimum bending radius of USE-2 and listed PV wire. USE-2 has a minimum radius of 5x the diameter of the cable; that is about the curve of a large cup. PV wire usually requires a minimum radius of 8x the diameter of the wire; that is about the curve radius of a good hamburger.

Another method of protecting the PV array cables from damage is to screen the exterior of the array to prevent entry. There are several products on the market but I have heard stories where squirrels still found a way inside the PV array.

Array screen 1Array screen 2

To address issue #2, obstructions under or around the PV array can cause water to enter the roof. The screening could cause a problem if leaf debris reaches the top of the PV array. If leaf debris is not an issue, the screen may be a good solution.

Any time there is a possibility of leaf debris reaching the upper portion of the PV array, it is imperative that there are no obstructing debris from being washed asway. If leaf debris is present, it may be best to keep the array high above the roof and use the best wire management techniques without screens.

nest under PV array
Nest under a PV module
IMG_7291
Wires chewed by a squirrel

 

 

 

 

 

 

 

 

If there is not a possibility of leaf debris reaching the PV array, screening is the best method to prevent nesting creatures from getting inside the array and damaging the cables and connectors.

Kelly Provence
IREC Certified Master PV Trainer
Solairgen School of Solar Technology
800-262-7560
www.solairgen.com

Styrofoam packing

Shouldn’t Packaging of Renewable Components be Renewable Too?

As far as pure energy goes, it doesn’t get better than solar energy. Photovoltaic (PV) energy technologies are improving and growing at an impressive rate. This industry hopes to be a major source of electrical energy on Earth in the not-too-distant future. At the rate it is growing, that will probably happen within 10 to 20 years. That sounds great but there is a dark side to the PV industry’s growth and it is in the way materials are facilitated to the complete installation of a PV system.

Before I talk about this environmental dark side of the solar PV industry it is worth noting its bright clean side. If all the energy required to manufacture and facilitate the installation of the PV system was derived from fossil fuels, it would take only two years of operation to offset that non-renewable fossil-fuel energy. As renewable energies become more dominant that figure will become shorter. Ultimately the process of offsetting the non-renewable, fossil-fuel energy required to manufacture and implement a PV system could be close to zero. Unfortunately, there is still an environmental dark side that has not been offset. This has to do with the negative effects of the front end and back end of product manufacturing, mining and packaging.

On the front end, mining is necessary to get the raw materials to manufacture PV cells, PV modules, inverters, batteries, support structures and electrical conductors. It is possible to reduce the effects of mining by using materials that are more plentiful in the Earth’s crust but there will always be a requirement for mining. It is also possible to recycle materials that are currently reaching the end of their useful life. The obstacle here is usually financial since it is often lower cost to mine for new raw materials than to recycle them from previously manufactured products containing these same raw materials. Interestingly, even if it takes less energy to recycle a material, it may be more difficult and more expensive to completely facilitate the recycling process. When recycling is disadvantaged by these economics, tax incentives or subsidies should be put in place to make recycling more lucrative. The back end of manufacturing is packaging.

Almost every manufactured product is packaged before being sent into the marketplace.

PV modules are packaged on wooded pallets with plastic separators. They are often wrapped in stretch plastic or they are packaged in pairs with cardboard. Plastic is a forever-material that is almost completely non-recyclable. Wood and cardboard-based packaging is much more recyclable. Its recycling should be encouraged though tax incentives or subsidies.

  • Inverters are packaged in cardboard and protected internally with either Styrofoam, polystyrene or corrugated fiberboard. Styrofoam and polystyrene are forever-materials that are non-recyclable and should not be used. Paper based products like cardboard should be used instead.
  • Batteries are typically packaged the same way as inverters but primarily with cardboard.
  • Small balance-of-system components (BOS) are shipped in cardboard, plastic and they use bubble wrap and foam peanuts to secure the items during shipment.

Inverter packaging

Packaging PV products with forever-products that are non-renewable and non-biodegradable is completely unacceptable. The purchaser of these products has a lot of influence over how these products a packaged; the best action is an email or phone call to the sales associate for the manufacturer as well as to the distributor of the products. Solar PV is a renewable product industry, we need to remove non-renewable, non-biodegradable products from the packaging process.

Kelly Provence
Solairgen, Inc.
IREC and NABCEP Certified PV Trainer
www.solairgen.com
706-867-0678
800-262-7560

On Grid Solar Farm

Working with Electric Utilities

Balancing the Needs of PV Customers with Utilities

Solar contractors and solar customers often find themselves on the adversarial side of utilities when interconnecting PV systems to the electrical grid. Most of the time this is due to a lack of seeing the other’s side and/or understanding of the other’s position.

Let’s first look at the utility’s position regarding PV systems. Many utilities offer incentives or encourage their residential customers to have PV systems installed on their properties. The reason for this is almost always for the purpose of appeasing the wishes of their customers. This an effort of goodwill because they know that electrical customers like the idea of energy coming from a clean renewable source and most of them also like the idea of owning their own energy. The benefit to the utility is not financial unless the PV system energy reduces load demand during periods when the cost to generate that power from other sources is high.

With residential customers, those periods are mostly in the afternoon and evening and then again in the morning as the sun starts to rise. This being the case, the PV systems with smart energy storage are the only systems that could financially benefit the utility as well as the owner of the system. They store the energy produced during the middle of the day and then feed it into the home and grid during the peak load periods.

With commercial customers the situation is different. The peak load period may be during the normal business hors of the day or 24 hours a day. These customers with PV systems may be shaving loads throughout the day or they may need to shift loads to a time of day other than the solar hours of the day. For the utility to benefit financially, a load demand study must be made for the specific customer. These customers with PV systems will also need energy storage for load shifting, peak load demand reduction and to provide consistent load support during climatic events that vary frequently during the day. The truth is that PV systems without smart energy storage do not save the utility money.

The exception to this would be with smart inverter technology that is controlled by the utility. California and Hawaii are both working through this process and it will become a more universal option in the very near future. However, these smart inverters and smart energy storage systems don’t address another issue for the utility. They understand how to regulate and shift energy supply with the energy sources they now have, the difficult task is how do they do this with customer-based power systems; the customer has far too much independence for their comfort. Customers would need to become liable to the utility for failure problems or let the utility have operational control of the system performance and operation.

Now let’s look at the customer’s position. The customer doesn’t have a choice when shopping for a utility; moving to another location is the only option if you don’t like the utility in your area. This is often a source of discontent for the customer. Customers depend heavily on electrical power for almost every appliance in the home and business. Natural gas, propane and fuel oil for heat are the exceptions.
Electricity seems expensive because we use so much of it; in fact, it is pretty cheap. In order to generate all your own electrical energy on-site, the cost will be excessive. In order to meet the cost per kWh from the utility, the PV system cost needs to be amortized over a 25-year period. Most residential customers do not appreciate how difficult it is to provide constant electrical power and how reasonable the price actually is. Commercial customers are more aware of this yet they would still like to be more independent for the utility if it is possible.

An important factor to both residential and commercial PV system customers is the return on investment. The customer wants the highest price for the kWh generated from their PV energy and they feel justified because they are generating clean energy and contributing to the reduction of conventional fuel sources with known hazards to our environment. This actually makes sense when looking long range. If the utility can absorb some of the cost of integrating PV energy into the grid, the industry will continue to grow and reduce initial coasts and therefore operating cost. Eventually the cost of PV systems with smart energy storage will be cheaper than any other energy source. It is rational to expect a public utility or a customer owned utility to invest in solar for the future by offering premium rates for the solar kWh. The problem with this position is that the rate to the customer will need to decrease over time with greater solar penetration, otherwise the investment from the utility will not have a positive return and the cost of electricity will have to go up. This is a difficult point to make to customers; someone needs to educate the electrical customer on how this will work to their advantage. The salesman for the solar contractor is unlikely do it and the customer will be much less likely to trust that information coming from the utility itself.

Effective open communication between the solar customer, the solar contractor and the electric utility is essential. Avoid adversarial positions and look for positions that benefits each entity.

 

Kelly Provence
Solairgen School of Solar Technology

 

The Best Methods for Energy Efficient Solar Homes

Solairgen-Installation475x317Your home’s overall energy efficiency is not as exciting to think about as a solar PV system, but it is much more important in most cases. Solar PV systems are getting more affordable, but that doesn’t help much if the overall energy consumption is higher than it needs to be. An energy efficient home will require about half the PV system size as a home that is not energy efficient. There are several low cost improvements that can improve energy efficiency; there are also many improvements that require an investment but provide good return on the investment.

The division of energy consumption in a home looks similar to the following pie chart taken from the Energy Industry Administration report.

Pie Chart of Typical Energy Usage for
Legend for EE Pie Chart

Appliances, electronics and lighting make up 40% of the home’s energy consumption. The lowest cost improvement is changing the energy user’s behavior, e.g., turn off lights and appliances when not in use. Replacing old appliances with higher efficiency ones as they require replacement, such as LED bulbs in long-hour-use fixtures.

Water heating costs can be reduced by several methods; the lowest cost methods are listed first. Insulate the hot water pipes from the water heater to the point of reduced access to the pipe. Buy and install an insulated jacket for the water heater. If your water heater fails and needs replacing, replace it with a high efficiency one. There are models that use a heat pump as the primary source of heat generation with heat coils as backup. Another, but more expensive option is to install a gas tankless water heater.

Heating and cooling together account for about 40% of the home’s annual energy usage. The best savings for the investment is to simply seal all cracks from the exterior to the interior of the home. This would be at the foundation, around doors and windows, and fixtures and access-ways to the attic. The next best investment is to improve the quality of insulation in the attic. The best insulation improvement is to have spray-foam insulation installed in the rafters and vertical walls of the attic. If there is a basement, the walls should be spray-foam insulated as well. Replacing blown-in insulation with spray-foam insulation can reduce heating and cooling costs by up to 50%. That would reduce the home’s total energy consumption by 20%.

It takes some effort and some investment to make the home energy efficient but it will not be nearly as expensive as trying to offset that portion of inefficient energy usage with a solar PV system. A 2000ft² consumes about 1800kWh/month. With an investment in spray-foam insulation, water heating insulation and replacing old appliances with high efficiency ones, it is easy to reduce the home’s energy consumption by 30% to 40% and spend less than $6000. That is about ½ the cost of a PV system to offset the same amount of energy.

Reduce energy consumption first through energy efficiency and then look at offsetting the remainder with a PV system. You may even have some money leftover to include energy storage with the PV system.

 

Kelly Provence
Solairgen
www.solairgen.com

Image of a Poor Solar PV Installation

How to Prevent a Substandard Solar PV Installation

No one wants a poor PV system installation, but it happens from time to time. The good news is it’s 100% preventable but you should first understand the causes of a bad installation, and then learn how to prevent it. We tell you how.

Problem #1: The installer is unskilled and unknowledgeable about the correct installation process, but how do you determine that?

Solution: Screen the installer. Ask for references and evidence of their experience such as pictures, invoices, permits and inspection reports.  Ask how much training they received, and where they received it. You can even ask to see their graduation certificates. Inquire about industry certifications (NABCEP) and whether they have a contractor’s license.

If they can’t or won’t provide any of the above information, don’t contract with them no matter what they promise you. A reputable installer will be eager to provide their credentials.

Problem #2: A skilled and experienced installer wants to install a brand-new product that is not fully understood or tested in the industry. It is not uncommon in this industry for changes in PV products to outpace the contractor’s full understanding of them. Don’t be the guinea pig.

Solution: Insist on tried-and-true system components unless it’s just an improvement over a product that has been around a while. It’s best to see how those brand new products hold up during beta testing. Find out by going to the internet and doing some independent research. Don’t be afraid to tell your installer what you learned and that you prefer another product.

Problem #3: The contract price is too low for the contractor to make a profit. Incorrect bidding is common when a contractor is inexperienced, but underbidding occurs occasionally even for experienced installers.

Solution: It is best to find out the going price for the installation prior to accepting a bid. If you don’t know the going price, get more than one bid and then compare. Most companies will give you a generic bid without a problem.

Some Advice: If the installer you select has underbid the installation, it may save you money in the long run to offer a fair, renegotiated price. Some contractors are very honorable and will do the same good job even if they lose money, but some will not and that may cost you more down the road. And remember, a deal too good to be true is usually exactly that, untrue.

In summary, the real responsibility is on you, the customer. Take a day or two to learn about the PV products, the installation process and who the good contractors are. There are many organizations out there to help you. Here are a few links to get you started: American Solar Energy Society, Solar Energy Industries Association, NABCEP, IREC, and The Solar Foundation.

Finding skilled, experienced solar PV installers isn’t difficult, and eliminates the frustrating and very expensive future problems of a bad, or failed, solar PV installation.

Kelly Provence
IREC Certified Master Trainer
Solairgen School of Solar Technology

The Solar PV Eclipse of 2017

Nat Geo Solar Eclipse Photo

How will the U.S. solar eclipse of August 21, 2017 be different from the eclipse that will occur in April of 2024? (Hint, this is not an astrophysics, geography or geometry question, but just to briefly answer these science categories, the path of the August 21, 2017 eclipse will be a slight northerly arc from Oregon to South Carolina and cover a swath about 80 miles wide; the 2024 eclipse path will be from Texas to Maine with a slight westerly arc, and cover a swath of about 70 miles wide.)

The difference between the two eclipses I’m referring to has to do with their effect on solar power PV (photovoltaic) systems. The effect of this year’s eclipse will be negligible mainly because the level of solar penetration – the amount of solar power being put into the electrical grid – is not that great.

However, the level of solar power connected to the grid will be significantly greater in 2024. If we had the same level of solar PV penetration now as we will have in 2024, the eclipse could create instability in the grid because of voltage collapse along its path. Interestingly, we will have a different type of solar generation system when the 2024 eclipse occurs. Energy storage with smart power monitors and utility controllable inverters will be the standard in 2024.

Fortunately, there will be no noticeable difference in the effects to grid stability. Without energy storage and smart inverters that continually communicate with the utility, the effects of the eclipse would definitely be felt when the next eclipse occurs in the U.S., but we will sail through it as we would hope to, with our solar-safe glasses, a lawn chair and no worries about its effects on solar electric systems.

Enjoy the experience

Kelly Provence
Solairgen School of Solar Training Technology
IREC Certified Master PV Trainer
NABCEP Certified Professional PV Installer

Solar Power World and “State of Solar” for U.S. 2015

Crash course in U.S. solar

We like to share good information about solar from other sources and this is a great article with good information about the solar market in the U.S. today. Residential and commercial solar installations have increased as costs have gone down, and the number of solar panel installations has increased dramatically as a result. It’s a good time to get into the market.

Atlanta-Buildings2a

SolarWindow Enters into Third Phase…

SolarWindow Enters into Third Phase of Technology Development Agreement with U.S. Department of Energy’s National Renewable Energy Lab (NREL)

02 Mar 2016
SolarWindow Technologies, Inc., the leading developer of first-of-its-kind transparent electricity-generating coatings for glass and flexible plastics, announced that it has entered into Phase III of its Cooperative Research and Development Agreement (CRADA) with the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL). The primary development goal of the Agreement is the commercialization of SolarWindow products.
NREL is recognized as one of the most respected and advanced solar-photovoltaic research institutions in the world. NREL scientists have been working side-by-side with SolarWindow Principal Scientist, Dr. Scott R. Hammond during the development of SolarWindow transparent electricity-generating coatings. SolarWindow is initially targeting the five million tall towers and commercial buildings in the United States, which consume almost 40% of the electrical energy generated.
“The prospect of skyscrapers generating electricity from see-through window products is very exciting,” said Dr. Maikel van Hest, a Senior Scientist in the Thin Film and Processing Group within the National Center for Photovoltaics at NREL. “Through our CRADA, we have been able to develop and test this technology using some of the world’s most advanced state of the art equipment. As a result, SolarWindow and NREL have advanced the technology by enhancing scale, efficiency and reliability.”
Under the terms of the Agreement, SolarWindow and NREL will continue to work jointly to enhance product performance, increase scale, and improve reliability; and develop new features and obtain important performance certifications required for a commercial rollout.
In addition, the team will focus on various SolarWindow product-specific goals, including:
  • Large scale window fabrication
  • Interconnection development for easy ‘plug-n-play’ on-site installation
  • Advanced performance measurement and modeling of SolarWindow when installed in various building types and geographies
  • SolarWindow performance under varying artificial and natural light conditions
  • SolarWindow can provide a one-year financial payback while producing 50-times greater energy than rooftop solar when modeled for a 50-story building, according to the company’s independent validation. For the same building, SolarWindow shows 15-times the environmental benefit of rooftop solar by avoiding 2.2 million miles of equivalent carbon dioxide emissions produced by vehicles, according to the company’s independently validated Power & Financial Model.
“With this CRADA extension in place, we’re one step closer to launching what is possibly the single greatest breakthrough technology in clean energy to help us overcome our dependence on fossil fuels,” said John A. Conklin, President and CEO of SolarWindow. “Keeping in mind that commercial buildings consume almost 40 percent of America’s electricity, our goal is to put a solid dent in reducing carbon emissions and offsetting a building carbon footprint while providing customers with clean electricity-generating solutions that make economic sense.”
SolarWindow Technologies, Inc.

NABCEP Profile Interview

Kelly Provence is one of a very small number of people who holds three NABCEP Certifications: PV Solar Installer, Solar Thermal Installer and PV Technical Sales. Kelly is the owner of Solairgen School of Solar Technology located in Dahlonega, Georgia. Solairgen is a training company which offers a complete program for electric solar panel installers and PV technical salespeople. Kelly is also an IREC/ISPQ Certified Master Trainer and a licensed master electrician.

In a personal interview, Kelly said, “I have always been an environmentalist, so in the late 1990s I felt it was time to take a serious look at my own ecological values, so I began incorporating PV installations into my electrical business.

“In 2002, I began focusing my efforts solely on PV, installing mainly off-grid and battery back-up systems. I branched out into solar thermal installations from there and sought certification in that area. Getting my NABCEP PV and Solar Thermal Installer certifications definitely opened doors for me; I received multiple job offers because of my NABCEP Certifications.

“After three years volunteering as a Director with the Georgia Solar Energy Association (GSEA), lobbying state and federal politicians on environmental issues, I realized there was a need for competent installation training, and there was no training facility in Georgia.

“It became clear that the solar installation industry needed a way to recognize experienced installers, and I shared NABCEP’s core purpose of maintaining high industry standards. I sat for my first certification, NABCEP PV Installer exam, and since then I have consistently advocated for NABCEP Certifications to all my students.

“In 2005 I transitioned the company to solar training exclusively, and it’s now my full time occupation. Approximately 50% of the people installing in the state have taken Solairgen training, and many of them have gone on to become NABCEP certified professionals. Today, many entities in the state, such as Georgia Electrical Membership Companies (EMCs), recommend or require installations to be performed by NABCEP certified contractors.

“My NABCEP Certifications tell customers I have achieved high-level skills, and lets them know I didn’t get into this yesterday. NABCEP Certification distinguishes individuals within the industry.

“I went for the PV Technical Sales Rep certification because students needed to be confident I have expertise in the subject I’m teaching, and I needed to know what the test was like.

“My customers respond positively because they understand NABCEP is the best example of self-regulation within the industry. I support it 100%. My students know what NABCEP Certification means to their careers; most are on track to become NABCEP Certified Installers or PV Technical Sales Reps.

“I will definitely be re-certifying when the time to do so comes up.”