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 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

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

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

Residential Solar: Which is Best – Ownership or Community Solar?

Solar Farm in Florida

Residential Solar: Ownership or Community Solar

Which is best for you? It really depends on you, your house and your utility. Consider the factors involved in placing a system on your home:

1. Is there room on the roof or ground for the PV array? The average 2000ft² home uses about 60kWh to 80kWh per day. To offset half of that energy a PV array would need to be 8kW to 10kW, and it would occupy an area of 600ft² to 800ft² on the ground, or it would require a roof area of 800ft² to 1000ft² due to required margins and offsets.

2. Will the PV array be a visual detriment to the home? It is possible to have the array visible and attractive with proper selection of materials, but a Homeowners’ Association could be a problem if the array is visible from the street.

3. Will it be financially beneficial? The matter of cost and return on investment (ROI). The federal tax credit provides a 30% reduction on total system cost. If you cannot take this credit, the value is diminished. If you live in a location where other incentives are in place, be sure that you qualify for those incentives.

4. The last factor is your personal reasons for owning a system. Seeing the array on your property, and knowing you’re saving energy and money on your energy bill is an important factor. Backup power is also an important motivator for owning a system, but if power is rarely lost in your area, a fuel generator may be a better option.

Consider these factors that would make community solar a good option:

The alternative to owning a system outright may be Community Solar programs. These programs are not available in all locations but their availability is growing quickly. Community solar farms are usually owned by the utility company. The customer can buy power from this farm through a program offered by the utility.

1. If locating an array on your home or property is a problem due to space or curb appeal restrictions, this may be a good alternative. These systems are huge and usually located within a few miles from your home. If it is a true community solar farm, there will be an area where you and your family can visit to learn about its function and performance.

2. The performance of the PV system will be maximized regarding the solar resource and the financial return on investment by the utility. This will provide the lowest cost for solar electric generation passed on to the utility customer.

The future of residential solar will be a mix of individually owned PV systems with energy storage, and community solar farms. Both will enhance the viability of the grid and reduce costs of electricity during the lifespan of the PV system. You should be able to pick the one that best fits your lifestyle and goals.

Kelly Provence CEO

Solairgen

PV-House-1-2 a

Converting Solar to Usable Energy

Photonic energy is a wave particle that travels at a speed of approximately 300,000 kilometers per second (186,000 miles per second). Almost everything reacts to this energy when contacted by it. The most common reaction is conversion to heat. Plants convert sunlight to chemical energy (complex sugar). The sugar is stored and used by the plant to live and grow.

Humans have also learned how to convert the solar energy to usable energy. We convert solar energy directly into two types of energy for use.

  1. Solar thermal (heat energy) is used for hot water and steam for power generation.
  2. Photovoltaic (solar electric) energy is converted from the visible light spectrum to power electrical appliances.

Solar Thermal Energy:

Solar Thermal energy can be used instantly and it can also be stored as hot water or oil in an insulated container. The storage is usually for no more than a day. This is the most efficient conversion of solar energy to usable energy although it may not be the most cost efficient method. Small-scale solar thermal systems require expensive equipment to capture solar energy, convert it to thermal energy and then store it for later use. The net conversion efficiency is around 30% for the average home.

  • The cost can be amortized over the lifetime of the system (15 – 20 years). Compared to heating water with electricity, the system reduced energy costs during the system lifetime. Compared to heating water with NG, the system may not reduce energy costs during the system lifetime.

Photovoltaic Energy:

Photovoltaic energy (PV) is used instantly since electricity travels close to the speed of light, although it can be converted and stored as chemical energy. Chemical energy storage such as electrolyte batteries or hydrogen provide 24-hour usage of solar electric energy. It also adds cost to the solar electric energy system. The net conversion efficiency of the average PV system without energy storage is around 13% to 16%. Energy storage will reduce that efficiency to 10% to 14%. Off-grid system net conversion efficiency is under 10%.

  • PV systems amortized over 5 to 10 years usually provide a positive return on investment. Over the life of the PV system (25 years), the return is 2x to 5x of the system cost. With energy storage added to the system cost, the lifetime return is 1.5x to 3x of the system cost.

Capacity Limiters for Photovoltaic Energy:

Peak solar hours occur during the six mid-day hours; this is when 80% to 90% of the photon energy is converted to electrical energy. This can be a problem for utilities if electrical energy is consumed during other hours of the day. Utility companies must balance the electrical power grid and provide stable voltage to their customers. A limited amount of solar electric energy can be fed into the electrical grid without causing voltage rise and collapse (around 10% of the electrical load). Increasing the capacity far beyond the 10% limit requires converting the electrical energy to another form of storable energy. Energy storage is necessary to extend the usage of solar electric energy.

  • Chemical energy storage (the electrolyte battery) is the most common method where electrical energy can easily be converter to and from chemical energy. The conversion efficiency is around 90% efficient. The cost of chemical energy storage is high, although several types of batteries are now on the market and prices are dropping. Charging the batteries requires hours for most technologies, although some technologies are faster than others. Residential systems are typically used for backup power when the utility power is lost. Commercial systems will use energy storage mostly for load stability and rate cost.
  • Hydrogen energy storage (fuel cells) is a growing technology where electrical energy is used to separate hydrogen from a molecule such as water. The conversion efficiency ranges between 60% to 90% depending on the method. The net efficiency is reduced much further if the hydrogen gas is concentrated for storage. Compressed hydrogen is very portable and lightweight. Non-compressed hydrogen would require massive storage space and would be impractical as a stand-alone system.
  • A couple of other methods of energy storage are flywheels and capacitor banks but neither have proven to be as feasible as chemical batteries or fuel cells.

Solar Electric Systems:

Solar electric systems produce around 1% of the U.S electrical energy generation; some areas of the U.S are experiencing close to 10%. Here is what is being done to satisfy electric grid stability as solar electric grows in capacity:

  • Correcting power factor problems: Most areas of the electrical power grid experience a lagging current because of inductive electrical loads. Solar electric inverters can correct some of that with their capacitors (capacitive loads).
  • Peak demand: When too many heavy electrical loads occur at one time, the electrical load demand is high, and very difficult and sometimes expensive to generate and manage. Distributed solar electric generation sites provide onsite power and reduce the peak load demand. Since rain and heavy cloud coverage reduce this capacity, energy storage can be installed to work with the solar electric system to produce power on-demand.
  • Load and cost management: Solar electric systems can be directed to produce energy during specific daylight hours when load demand is highest and/or when electrical rates are highest. Combining this with energy storage will increase the return on investment for the system owner.
  • Micro-grids and emergency power: Some solar electric systems with energy storage will be designed with extra storage capacity. These systems can operate and produce electrical power for several days or longer.

The applications identified above will allow solar electric system capacity to grow without limits.

Kelly Provence
Solairgen
www.solairgen.com

CS-Installers-on-Roof

Is Renewable Energy an Oxymoron?

In short, yes it is. Energy changes form, but it does not renew itself and an outside force cannot renew it, although it can draw energy from an outside source.

On the other hand, everything is energy and as far as we know, there is no less of anything now than there ever has been. Matter and energy are part of the same equation; energy changes form but it doesn’t cease to exist. In that respect, all energy is renewable.

What is usually termed renewable energy is energy that uses a fuel source that appears to be endless, continuous, and for the most part not found in storable state.

Fossil fuel energy comes from ancient carbon stores and nuclear energy comes from radioactive heavy metal deposits; neither of these energy sources can be replenished for our use.

Solar energy is the most abundant of the renewable energy sources. It takes about two years for a solar photovoltaic (PV) energy system to produce as much energy as was consumed to manufacture it. Photon energy is abundant but not concentrated; this requires massive area coverage. In locations where a large amount of energy is consumed, the real estate required for the PV arrays can be a serious cost factor. Using some type of building integrated PV array attachment seems to make the most sense. One major problem with solar PV energy is that is must be stored in order to displace conventional steam producing energy sources. Over all, PV energy is the most renewable source of energy we have.

Wind energy is not as abundant as solar energy but it is more concentrated. Wind energy systems require less area than PV systems but they required dedicated real estate; they cannot be integrated with existing buildings, however they can be integrated with the existing flora and fauna. It only takes about one year for a wind energy system to produce as much energy as was consumed to manufacture it.

Wind is a result of solar convection due to the earth’s rotation, local terrain and air temperature; this being the case, wind energy is variable with regard to location, time of day and time of year. Energy storage is necessary if wind energy is to displace conventional steam producing energy sources. Wind energy is probably the second most renewable energy source we have.

Hydroelectric energy that uses dams is limited to existing rivers and bodies of water. This type of energy currently provides about 20% of the world electrical power. The advantages of using hydroelectric energy are, flood control, potential energy storage, and recreation areas are created; these power plants create many economic benefits besides generating electricity from a renewable energy source. The disadvantage is mostly the effects on the ecology of the river system. The long life of hydroelectric generators makes them an excellent renewable energy source.

Biomass steam generators are quickly becoming a replacement option to coal steam generators. The limit to this renewable energy source is available land and water resource; otherwise, it has the on-demand energy delivery like coal but has a carbon-negative footprint.

Geothermal energy derives its energy from the internal heat of the earth and is an excellent source of renewable energy. The limitation for now is that it is only available in locations where the earth’s mantle is proximate to the Earth’s surface.

Renewable energy and clean energy are dissimilar with regard to the energy source. Nuclear energy is considered very clean since the emissions are produced only from construction and maintenance of the facility. The chart below shows the proportion of energy generated to CO₂ emissions for each generators lifecycle.

Courtesy of www.nei.org

The question of whether renewable energy is an oxymoron is a good one. As with most commonly used terms or phrases, it is dependent on a particular perspective. In my own definition of renewable energy, I consider the lifecycle of the energy generated verses the lifecycle of the energy source; the former must be greater than the latter.

If nature can renew the energy source in a period equal to or les than the period in which we consume the energy, consider it renewable.

Start your solar training classes to learn more about renewable energy. Learn more about Solairgen School of Solar Technology

Solar PV Panels on Cedar Home

Grid-tie Inverters and Generators

Grid-Tied PV Systems and Generators

The question keeps coming up; “Will a generator keep the grid interactive, non-battery based PV array operating during utility power
outages?” In theory, it seems like a logical idea since the generator operates at 240 volt 60 Hz and this is what the inverter is looking for in order to
continue operating.

The problem is, the generator cannot absorb the excess energy from the PV inverter output, nor can the generator react quickly enough
to the fluctuating output of the PV inverter. With a grid connection there is a certain amount of buoyancy or capacitance in the grid to allow for varying electrical energy.

A second problem is how the generator will react to another AC source; it may shut down or it may be damaged by the other AC source.

The solution is the same as it has been since the start of PV energy systems, battery storage. There are many new product advancements in
battery storage or energy storage and the future looks bright. For now, the best solution for backup power during a utility outage is one of two options:

  1. An AC generator can be set up as backup power with a transfer switch that senses the loss of utility  power. If a grid interactive, non-battery based PV array is operating when utility power is down, it will go into a standby status until the utility power returns to normal.
  2. Another option is to use a battery based, grid interactive PV system that can provide backup power during utility outages; a generator can be tied in with the battery-based inverter to help charge the batteries during extended cloud cover and rainy conditions.

If option #2 is your preference, you will find that battery based inverters are quite different from utility interactive inverters. If you presently have an SMA utility interactive inverter, you can add the SMA Island battery based inverter to the system and have the best of both worlds.

For other utility, non-battery based interactive inverters, you either need to change out the inverter to one that is battery based with the utility interactive feature or just use the generator as the backup.

Kelly Provence
IREC/ISPQ Certified Master PV Trainer
Solairgen
https://www.solairgen.com/
706-867-0678