Managing PV Wire

Solving the Problem of PV Array Wire (or Cable) Management

Wires covered with wireThis is the one part of installing a PV array that never seems to get easier although racking manufacturers are doing their best to help. There are three objectives to managing these PV cables: 1. Secure them in a manner that is code compliant.  2. Protect the cables from damage. 3. Minimize visibility or secure them attractively. The objective is to select a method that does all three with minimum effort and cost.

Let’s start with #1. The NEC states that USE-2 (PV wire/cable) must be secured within 12” of a junction box and then every 48” of length. While it is easy to achieve the 48” support requirement, it is not as easy to meet the 12” of a junction box requirement, especially from the PV module junction box. This requirement is often overlooked by inspectors if the cables appear to be well secured. The picture below shows how this 12” requirement is achieved and how it is not.

12 inch cable

Secured within 12” with cable clips

18 inch zipties

Secured 18” with zip-ties to rails

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 radius of 8x the diameter of the wire; that is about the curve radius of a good hamburger.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.

There is also an NEC requirement for the work to be in a “neat and workmanlike manner”. This gives the inspector a lot of leeway. Chances are good that if an electrical installation is sloppy, it also has some installation errors.

For ground mounted PV arrays, protecting PV conductors from unauthorized personnel is also required. This can be done with a fence, adequate height (8’ minimum) of the cables above ground or a type of screen fastened to the PV array modules. (see images on next page)

Wires covered with wire   Larger panel wire covered with wire

By protecting the cables from unauthorized access, they are also easier to secure.

Code compliance usually addresses #2 and #3 objectives. The best way to meet these objectives is to use the racking manufacturer’s wire management system and supplement it with some generic products like wire clips that attach to the module frame and UV rated zip ties. Pictured below are two manufacturer designed products and features for wire management.

SnapNRack photo

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

ironRidge photo

IronRidge provides cable management clips that are secured into the top rail.

It is always a good idea to use the most common PV module frame mounted cable clips as a supplemental wire management system. One wire management system is never fully adequate for the various conditions that occur on site.

When using zip ties to supplement the wire management system, consider the life of the plastic tie. It needs to be UV and hard-use rated.

UV photo

The primary problem with wire management comes from lack of planning. By simply visualizing how wire management is to be handled prior to starting the job will go a long way toward making it a simpler process instead of a source of aggravation.

 

Kelly Provence
Solairgen
www.solairgen.com

 

The Importance of Optimum PV Array Size for Solar PV Systems

Residential Solar PV Ground Mount SystemThe question of optimum PV array size is the first question to be answered when designing the PV system. There are several factors that have to be considered to arrive at the best size. The customer budget, the available area for the array and the purpose of the PV array are always primary considerations. The budget is usually the most flexible since the system can be financed. The second may be difficult to get around if the location options are limited and restrictive. The third part is where most mistakes are made. There are generally two types of systems, (1) stand-alone and (2) utility grid interactive.

The stand-alone system must be designed to serve the electrical loads throughout the year. The PV array is usually sized to serve the loads in the month with the highest ratio of electrical load demand verses available solar energy. As long as the electrical load demand is known and the solar resource is known, the calculation is made for each month of the year (Avg. daily loads kWh ÷ Avg daily insolation ÷ Power conversion efficiency % = ratio) The ratio is the exact size of the PV array necessary to offset 100% of the energy consumed in that critical design month. The hard part is usually determining the kWh of electrical consumption.

The stand-alone system can be off-grid with generator backup or grid supported. If it is grid supported a portion of the house electrical loads are served by the stand-alone system. The PV array is sized for the stand-alone portion of the house.

The graph below show a typical PV system output capacity compared to the electrical consumption for each month of the year. The PV array is exaggerated in size to cover the worst ratio months of the year.

Graph 1

Grid interactive systems must consider how much power can be fed into the electrical system and remain compliant with the utility interconnection agreement and the best power offset value. The most common interconnection agreement is Net Metering for the billing cycle. It is typically set to offset up to 100% of consumption with solar PV generation during the monthly billing cycle. Energy generation in excess of 100% is usually compensated at avoided cost, about 1/3rd the rate of retail. The obvious objective here is to not generate more than is consumed for each month of the year. The challenge is to project generation and compare it to consumption throughout the year.

The months that usually control the PV array size are in the spring and fall. We consume less energy during these periods because of the reduced need for heating and cooling. Coincidentally, these are usually the best two periods for solar PV generation because of clear skies and lower temperatures, April and May are typically the best generation months.

The graph below shows the typical electrical usage for residential customers. The PV system that is designed to offset 60% of the annual electrical consumption is generating 100% of that consumption during the month of April.

Graph 2

A third type of system is a self-consumption type system that requires energy storage and is designed to connect to the grid but not sell into the grid. The PV array size usually follows the same rules as the interactive guideline above, but it can be more complicated and requires a smart control system with consumption and generation metering to keep everything in check.

It is OK to oversize a stand-alone system but with interactive systems keep an eye on the low-consumption vs. high generation months.

Kelly Provence
Solairgen
www.solairgen.com

706-867-0678
info@solairgen.com

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

Jobs in the Solar PV Industry

Image of Solar Installer on Roof of a Virginia HomeThe solar workforce in the U.S. has grown by over 160% since 2010 for a little over 93,000 to well over 250,000. Solar accounts for less than 2% of all electrical energy generation in the U.S. However, the solar industry employs twice as many workers as the coal industry, almost five times as many as nuclear power, and about the same number as the natural gas industry.

The largest sector of jobs is in installation of the PV equipment and systems at 51%. The second largest sector is in manufacturing of equipment and materials at 16%. Project development is third at 14%, sales and distribution is fourth at 12%, and the remaining jobs are in various sectors at 7%.

These figures indicate that the best job opportunities will be in the installation sector and that would be correct. This will require a certain amount of training to make yourself attractive to an employer and the solar industry in general. The most difficult positions for employers to fill are, (1) Sales Professionals, (2) Electricians and (3) Installers. If it is possible to get retrained to fill the roll of one of these professional groups, your prospects for employment are very good.

It may also be possible that your present skill will be attractive to an employer in this industry. Every solar contractor or developer needs workers who possess a variety of skill sets. Aside from developing skills listed in the previous paragraph, here are some job skills that are always be required by some of the personal within each company:

  1. An understanding of IP and computer communication are necessary skills since all solar electronic equipment is now built to communicate within its own network and with the internet.
  2. A proficient understanding of computer programs and the ability to bridge computational and drawing programs with DOE and Google type programs is essential to most solar companies.
  3. Writing and editing skills are always necessary when communication with other people and groups is common; this is an undervalued skill that can can make a big difference in the success of a company.

The best way to get into this industry as an employee or as a contractor is to first look at the skills you now possess and see where you would fit in. The next step is to get enough training with solar sales and design to get you started and continue training as you move up the ladder to success.

Kelly Provence
IREC Certified Master PV Trainer
NABCEP Certified Professional PV Installer
Master Electrician

Solairgen School of Solar Training

The Good and Bad of Net Energy Metering

MeterRealities in Net Energy Metering (NEM)

The term net metering has several definitions and interpretations. There is one most of us agree on as the standard model – the owner of a solar PV system may offset up to 100% of their electrical energy usage during the course of any one-month period at the retail rate. This is the one that solar contractors and customers like but it is also the one that utilities would like to see go away. There can be some drawbacks for the customer under this NEM.

Monthly metering fees are usually added, monthly processing fees are sometimes added, some utilities require the customer to shift to time of use (TOU) metering under NEM agreements and occasionally the utility will raise the base rate for customers with NEM agreements. The actual rate offset by the PV system is usually less than it appears when these other costs are factored in. Producing energy above the NEM point would be compensated at a lower rate called the “avoided cost rate” or “possible not allowed”.

The average size of the installed PV system offsets at least 50% of the total energy consumed and sends at least 50% of that energy into the grid during midday hours. Without a NEM agreement, the digital meter will charge the customer for the energy sent back into the grid. Even though 50% of the usage is offset at the retail rate, the other 50% will be charged to the customer and the cost of the system will never be recovered.

There are other options but they are not necessarily optimum. Ideally all energy produced by a customer’s PV system should offset load demand and should not flow out into the grid. This can be achieved in one or more ways.

The simplest way is to design the PV system small enough so that the premises consumes all the energy produced. This is easier for a business to do because most of the energy is consumed during the day when the PV system is operating. A typical residence consumes most of its energy during the morning and evening hours (non-solar hours). Because of this, the PV system size should be restricted to offset only around 20% of the total energy consumed; a NEM agreement would not be needed and the monthly fee would be avoided.

Another option is to design the PV system with energy storage. The nice part of energy storage is having some electrical power during an electrical outage. The bad part is that it adds between 50% to 100% more cost to the PV system. The system functions as stand-alone with support from the utility and does not sell any energy to the utility so the NEM agreement and monthly fee is avoided. The big drawback to this type of system operation is that it restricts PV production during midday to prevent overcharge of the batteries.

Smart energy storage systems provide key benefits to NEM. These systems require a battery type that can be left in a partial state of discharge for prolonged periods without causing internal damage to the battery. The systems meter usage and production; energy produced during midday can be temporarily stored and released during the highest TOU rate periods of the day (afternoon and evening). Some smart energy storage systems can prevent the system from selling into the grid; in that case there is no need to participate in an NEM agreement with the utility and the monthly fees can be avoided. Smart energy storage PV systems will cost 100% more than an interactive PV system without energy storage.

Net metering values need to be calculated for each customer, and the effects and benefits will be different for every one of them. There are no one-size fits-all with PV systems and NEM.

Kelly Provence
Solairgen School of Solar Energy
www.solairgen.com

 

Solar Shingle

The Future of Solar PV Shingles

Solar shingles seem like the most logical application for the future of solar PV systems, serving two purposes – a roof and a solar PV system – by simply integrating the shingles into photovoltaic roofing. There are problems with the solar shingle system, slowing its mainstream marketability, but may work if the following obstacles can be overcome:

(1) The cost of solar shingles is not competitive with conventional solar electric PV modules. Costs might balance with high penetration into the photovoltaic industry, but that takes time.

(2) The physical constraints of solar electric roofing shingles do not allow for custom fitting to varying roof dimensions. This is an obstacle that is difficult and expensive to overcome.

(3) The solar roofing contractor’s training is limited to the narrow market of solar shingle manufacturers. The manufacturers will not train contractors in areas where sales are not profitable, so the solar shingle market restricts customers’ choices and is controlled exclusively by the manufacturer.

(4) Roof warranties can only be fulfilled by the solar roofing manufacturer and its own factory-trained solar roofers. Repairs may be delayed if there is not a trained contractor in the customer’s area. Roof damage not covered by the solar roofing manufacturer would be difficult or impossible to have repaired by conventional roofers who are not trained to work with solar shingles.

I would like to see this product succeed in the market, but no manufacturer has made a successful long-term run with residential solar roofing to date, and some who are attempting it have yet to make a profit in the photovoltaic industry.

Mainstream success of solar shingle roofing may happen, but it doesn’t appear to be coming in the near future.

 

Kelly Provence
NABCEP Certified Professional PV Installer
IREC Certified Master PV Trainer
Solairgen, Inc.
706-867-0678
info@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

Solar Training Education and Learning Text

Training for Changes in the Solar PV Industry

Why We Keep Up with Industry Changes

There is no argument that the only constant in the world seems to be change. This is even truer for the solar industry as changes in the solar market happen fast. The only constant appears to be the solar resource itself, our sun.

Training courses must be updated regularly to meet those industry changes and to prepare students who are either just entering the solar business or professionals who are currently working in it. Solairgen is constantly editing its courses for these changes. When necessary, we’ve been known to completely rewrite courses to address industry changes due to product innovations, code changes, regulated utility interconnection requirements, and rapid industry growth.

Here are the most recent changes to our training curriculum:

PV301 NABCEP Associate Installer Credential Exam Prep:
Recently we added a NABCEP Associate Credential exam prep course to follow our PV201 Introduction to PV Design and Installation online course.  PV301 is free to our PV201 students and costs just $185 for anyone who has not taken PV201, but has met the training prerequisite to sit for the Associate Credential exam but needs exam prep study material.

PV202 Solar PV Technical Design
Our online PV202 course now focuses on the technical design aspects of residential, commercial and energy storage systems. It is the next step for designers and installers after completing PV201.

PV210 PV Sales and Cost Analysis
We have introduced a new course, PV210 PV Sales and Cost Analysis that focuses on training students to focus on the marketing aspects of solar: identifying the solar customer and their energy needs, system costs and financing methods, the value of the investment, environmental impacts and proposal writing.

PV221 – PV224 Advanced Online Series
The advanced training workshop and advanced online series have been updated to address new solar products and changes to the NEC codes. These courses include PV221 PV System and the NEC, PV222 Interactive PV System Configuration, PV223 PV Maintenance and Troubleshooting and PV224 Energy Storage PV System Configuration.

Solar is growing faster than any other energy industry so change means growth, and we believe you will enjoy being a part of it. The changes happening today are exciting innovations that make the solar industry stronger and our training produces strong professionals in the field.

Kelly Provence
IREC Certified Master PV Trainer
Solairgen School of Solar Training

Lineman in Ice Conditions

Better Utility Customers

Understanding the Effort to Provide Energy Makes for a Better Utility Customer

One thought always present in my mind during power outages is the electrical utility linemen who are working long days, often in extreme weather conditions, to get the power back on. They possess a level of dedication and commitment that goes beyond the ordinary. When the lines go down the electrical workers step up and work heroically until everyone has power again. I for one salute them all for that effort.

I enjoy the fact that I have my own PV system power when the utility power fails, but then there is the daily chore of checking and maintaining the energy storage system and backup generator. I’m always relieved when the utility power returns. I know how time-consuming it can be to generate and maintain electrical power even for one home and business.

Those like me, who own grid-connected PV systems with energy storage, have a slightly different perspective about energy. The PV system with energy storage is a luxury that is rarely used because power outages are rare in most parts of the U.S. When the grid goes down for several days, the true time and commitment cost of energy becomes obvious, especially if cloud cover blocks the sun.

People with PV systems who live off-grid know the time and commitment required every day. The daily chores include a fair amount of attention to maintaining the energy source(s) such as their PV system, energy storage and/or backup generator.

Then there are those who own a fuel generator as a backup source of power. If the power is off for a week, they face the same problem as the person with the PV system with energy storage. The exception is that they do not have the high upfront cost; most of their cost comes from the fuel necessary to keep that generator running and it does get expensive in the long term.

People who own a PV system without energy storage have their own perspective; they produce their own energy but only when the grid is up and within the limits of the utility interconnection agreement. They have no independence regarding energy, but they do appreciate the demands of generating it. When the grid goes down, they are totally dependent on the utility personnel to bring power back online.

Finally, those who have no self-generation sources are basically in the same boat as those with an interactive PV system but generally have less understanding about the true time and commitment costs of energy generation.

People with their own backup energy systems often have a better understanding and appreciation for the true “costs” of energy. I fall into the category of those who own PV systems with energy storage and I also possess a fuel generator to back up the solar. I prefer not to run the generator for several reasons but I’m glad to have it when the power is out and cloud cover blocks the sun for several days.

I am in the solar energy industry, and a staunch solar energy advocate, but I have the highest respect for electrical utility companies and especially for the linemen who push themselves to their limits for us during power outages caused by the vast and uncontrollable power of nature.

Kelly Provence
Certified Master PV Trainer
SOLAIRGEN
School of Solar Training
ww.solairgen.com

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