3- WHAT KIND OF SOLAR PANELS SHOULD YOU CHOOSE?

You've determined that going solar is right for you, but you're not an expert on the subject... 
There's a lot to think about, learn, and consider! Now - and preferably before asking for solar quotes - is the time to educate yourself about the many solar panels manufacturers and the various kinds of solar panels.
In this page, I try to provide the necessary background on what you need to know to help you make an informed decision regarding solar panels, when you do go and get quotes.


TO DO LIST
SOLAR IS RIGHT FOR YOU! Now learn about:
The Solar Array/Panels produce Direct Current (DC) electricity, which is converted into Alternating Current (AC) at 110 V by an Inverter and/ or an Optimizer is used to maximize production. DC must be converted to AC so it can be used by the home's appliances and from the outlets in your house. Solar Systems can either be connected to your utility's electricity grid or to a battery for storing and using later. 

Here is a primer on how solar PV  works.

More detail on the entire solar power system can be found here.

So you can think of the Solar Panels as the heart, the Inverter or the Optimizer as the brain, and the mounts for the Solar Panels as the bones. 

Solar Panels

Many types exist, and making solar panels is not always nice for the planet, some are made in much less toxic ways than others. Not all panels are created equal. See below for more information on materials, production warranties, and further below on panel efficiency, and many more useful things.

Mount

Solar panels need to be attached to some kind of mount (think of a solar panel on a mount as the window in the window frame). 
A lot of information concerning mounts can be found here.

- Flat roofs are common in NM, and if you space on your roof, a ballasted mount might make the most sense: your installer won't have to drill into the roof, since the weight of the panels+mount will hold your system in place (see picture to the left);

- Pitched roofs do require holes to mount the rails for the panels, making your choice of provider/installer crucial: ask about workmanship warranty to protect you against leaks years down the road.

- If you don't have roof space, you can consider ground mounted solar panels.

Converting DC into AC

After the panels themselves are two pieces of equipment, inverters and/or power optimizers. Optimizers make sure the maximum DC power is delivered (to account for shading or damage), and the inverter converts DC into AC, and are arguably the next most important piece in your solar power system. To get the best performance from a panel you need Maximum Power Point Tracker (MPPT) and panel monitoring. These can be accomplished in multiple ways, but typically use a string inverter with a power optimizer. What you really need to know is if you need a power optimizer and inverter or if they are built into the panel in some fashion.

3 kinds of inverters

This is getting quite technical, but you will understand much more thanks to this page. And here is video on inverters.
  • Micro-inverters (on the back of each panel, allows MPPT and panel monitoring directly at panel, higher cost)
  • String inverters (most common, inverts all power at one point, may need power optimizer for MPPT)
  • Central inverters (very large string inverter for larger installations)

Power optimizers

  • Power optimizers allow for MPPT and panel monitoring using string inverters
As to whether power optimizers are better than micro-inverters, there is no definitive answer.

Sunpower says their panels do not need a power optimizer as they have another on-panel scheme for this, using their MAXEON technology with diode protection.

Stay on Grid or to go Off-Grid

This is another decision to make...

Although the utility company charges a monthly connection fee, it seems that at this point (early 2016), staying on the grid and waiting for battery costs to decrease and technology to improve is the most cost effective betunless no grid is available where you live.

But if you live in NV for instance, the Utility there is trying to stick it to solar owners with a rate change and loss of net metering (especially ironic given the Tesla battery factory in NV)! So going off-grid in NV when the Tesla factory is at full production making cheap long lived batteries will probably make sense, which will in tun really hurt the utility company.

The batteries will come in different sizes - yet another decision to make, and I'll add more information here as more becomes available, but as of now, Tesla is continuing to work on the 6.4 kWh system and abandoning the 10 kWh system.

The Various Solar Panels Materials

There are three major types of Silicon Cells currently used to create Solar Panels:
  • Mono-crystalline
    • the highest quality of solar cell
    • one can tell if a panel uses Mono-crystalline silicon cells if it appears completely smooth and black
    • cut from a single cell of pure silicon, which allows them to more efficiently convert the sun's energy to electricity
    • efficiency: 14-17%; record25.6%
  • Poly-crystalline:
    • cells are made up of multiple silicon cells fused together
    • typically, these kinds of solar panels appear bluish in color
    • slightly less efficient than Mono-crystalline cells, but more affordable
    • efficiency: 13-15%; record: 21.25%
  • Thin-film
    • to create thin-film panels, manufacturers spray a layer of silicon onto a substrate
    • may appear more flexible than other kinds
    • make up the cheapest and least efficient solar panels
    • efficiency: 5-7%; record21.0% for CdTe & 20.5 % for CIGS solar cells
Often, Solar Panel Manufacturers will produce more than one kind of solar panel, so make sure you know what you are buying.

This link also contains interesting information: www.california-solar.org/news/solar-tips/choosing-the-best-solar-panels/

For interesting information regarding PV physics and efficiency, you can visit: physics.ucsd.edu/do-the-math/2011/09/dont-be-a-pv-efficiency-snob/

Also, technology is always changing, and the pervoskite technology may be available in several years, making panels even cheaper, but I wouldn't wait, given the current Tax Credits incentives, which will/may not be available anymore in the future.

Manufacturers of PV Solar Panels are Rated by the Silicon Valley Toxics Coalition

If you are installing Solar Panels because you want to help the environment by reducing your use of coal and other harmful energy sources, then you should also make sure that you purchase solar panels manufactured with the environment, workers, and the communities in mind.

The Silicon Valley Toxics Coalition (SVTC) believes that there is still time to ensure that the PV sector is safe for the environment, workers, and communities. And believes we need to take action now to reduce the use of toxic chemicals in PV, develop responsible recycling systems, and protect workers throughout the global PV supply chain.

Per the SVTC, currently the best solar panel manufacturers to go with (in order of rating) are:
The Scorecard is a resource for consumers, institutional purchasers, investors, installers, and anyone who wants to purchase PV modules from responsible product stewards. The Scorecard reveals how companies perform on SVTC’s sustainability and social justice benchmarks to ensure that the PV manufacturers protect workers, communities, and the environment. The PV industry’s continued growth makes it critical that action be taken now to reduce the use of toxic chemicals, develop responsible recycling systems, and protect workers throughout global PV supply chains.

Rated are:
  • Extended Producer Responsability (EPR)
  • Emissions Transparency
  • Chemical Reduction Plan
  • Worker Rights, Health & Safety
  • Supply Chains
  • Conflict Materials
  • Module Toxicity
  • High Value Recycling
  • Prison Labor
  • Biodiversity
  • Water
  • Energy Use & Green House Gases
For description of the above titles, and for more information, click on the icon for the 2015 report:

All reports can be found by following the links:

The scores for the best manufacturers are summarized in the following for 2013, 2014 & 2015.

Other Very Useful Things to Know about Solar Panels (mono & poly-crystalline Silicon)

Position of the circuit linking the various Silicon cells

All conventional poly-crystalline and mono-crystalline Si solar panels are designed with the circuitry facing the sun and the elements. SunPower, however, designed the circuitry to be underneath the cell, as illustrated below.
The 2 vertical silver lines are thin conductive ink 'collectors'. They are present on both sides of the cell and are subject to micro-cracking. Moreover, on the top of the cell, they block the sun.
The darker cells are SunPower cells, made of a higher grade mono-crystalline much darker (blacker) Silicon. They have a full copper foil base, and soldered cell connections with strain relief, as illustrated by the image with a red border.
The design feature of the circuitry made me realize that SunPower really works hard to provide smartly designed high quality products.

Production Warranties

Solar panels degrade as time goes by and as the Sun and the elements hit them.
Solar panel manufacturers warranty the expected degradation of their solar panels.
The graph below shows the warranties for 3 manufacturers only: SunPower, Trina & SunTech.
The higher the production stays overtime, the more the system will produce over its lifetime. 
Comparing the first 25 years of the 3 systems, if they are rated to produce 5,000 kWh/year the first year, they will have produced, over the span of 25 years:
- SunPower: 114,500 kWh;
- Trina: 111,375 kWh (or 97.2% of what SunPower warranties).
- SunTech: 108,625 kWh (or 94.8% of what SunPower warranties).

What happens after the 25 years is another important issue and will be discussed in the next paragraph.

Life expectancy

Since we're talking 25+ years in the future, solar panel manufacturers do not want to make promises they cannot keep and/or don't have enough data to know how their panels will stand the test of time.

Indeed, except for SunPower and SolarWorld who are respectively 31 and 28 years old; Trina, REC and Yingli are respectively 19, 19 and 18 years old, younger than any of their warranties.

SunPower defines the useful life of their panels as 99% of modules producing at least 70% of their original rated power output, and they expect its panels to have a useful life of more than 40 years.

There is a possibility that the other/conventional panels do well in time also, but I have requested that information from solar providers with no success. Does the energy production of these conventional panels continually decrease over time, could there be a sharp change in slope of the production of these panels, making them useless after 30 years?

To me, since I consider the investment of going solar to be very important, and since the investment is paid off anywhere between 13 and 21 years depending on future costs of electricity, it is only logical to think that after these 21 years, I get a return for as long as possible

Efficiency & Associated Cost

In this paragraph, I want to point out some common misconceptions regarding efficiency and associated price/cost of panels.

Earlier, I pointed out that various efficiencies of solar panels. The record efficiency is currently 25.6%.

As an example here, I compare 2 SunPower panels, one which is 21% efficient (X-Series) and the other which is 20% efficient (E-Series).

https://sites.google.com/site/santafesolarresearch/what-panel-to-choose/SunPower%20E-series%20vs%20X-series.jpg?attredirects=0

You may think that there is not much difference between a 20% efficiency panel and a 21% efficiency panel. In fact, you might say that it is 1%.
That is true, but when it comes to energy production, keep in mind that a 21% efficient panel will produce not 1% more than a 20% efficient panel, but 1% of 20% more, i.e. 1/20=5% (for systems of the exact same size):
20% (E-panels) <=> $10,000 => 2100 kW/m2/year * 0.20 = 420 kW/m2/year produced
21% (X-panels) <=>     ???     => 2100 kW/m2/year * 0.21 = 441 kW/m2/year produced
So for the 1% you get 21 more kW/m2/year, or 5% more (21/420 = 5%), so you should expect to pay at least 5% more for the X-panels: 0.21 x $10,000 / 0.20 =  $10,500.
A 5% added production is substantial over decades, it ends up justifying a higher cost, especially with rate hikes and inflation!

Just to make the point, the difference in power production going from 20% to 21.5% is not 1.5%, but 7.5% (1.5/20 =7/5%)!

Efficiency also drops over the lifetime of the panel, leading to a year decrease in the amount of electricity being generated, typical panels lose about 0.7% of there production/year, Sunpower loses about 0.4%/year. Thus over the 25 years of life that is a 16% decrease in the power output of your system (9.5% for Sunpower).

Also, typical polycrystalline systems lose 1-3% of their initial energy production in the first few days due to an oxidation reaction on the boron doped silicon. This is accounted for by the manufacturer ahead of time in the wattage rating of the panel. See above.

Cost per watt may yet drop further once Solar City's Gigafactory comes on-line (oddly in Buffalo, NY), but predicting the future is tough business. Why wait for what could be when it makes sense now?

Balancing Energy Production

Solar cells (the square-ish, six-sided panes) in a solar panel work in series, thus one passes the electricity to the nextJust as a string of x-mas lights will stop working past a burnt out light bulb, when one of the cells of a conventional solar panel is covered, the following cells do not produce, and do not transfer the generated power along the panel. This can result in large power losses, up to 45% drop in power just by covering 9% of a panel. This is where a power optimizer can help alleviate some of that loss, or other built in features. Thus it is important to know how your panel will respond to a leaf or bird dropping, and what type of protection is available or already built in!

SunPower panels use another smart design feature described in this video, which allows for all but the shaded or covered cells to produce, and keep the power output up without a power optimizer.

Angle Sensitivity to the Sun

The angle at which your solar panels are to be installed depends on your latitude and is tricky to determine. This page explains it very wellOf course, a solar panel on a 2-axis tracker will perform best, at 100% of the optimum. 

If it is fixed, it will perform at 71% of its optimum. Adjusting in the Summer and in the Winter will raise the performance to 75.2%.

As an example, assuming a fixed installation, for Albuquerque, NM, which has a latitude of 35°, the full year angle will be 29.7°, and the performance 71%.
  • Case 1: a ground mounted installation will work for you if you:
    • have a lot of land,
    • don't mind installing your panels in your yard.
  • Case 2: a ballasted roof mount installation will work for you if you:
    • have a flat roof,
    • have some land but would rather maximize your space by installing them on your roof,
    • don't want to drill in your roof to avoid leaks but NM encounters really strong winds. 
Case 1 is the favorite case of solar providers.
Case 2 requires finding a solar panel which is not as sensitive to the direction of the sun rays would really help, since you could install your panels at 10° and not have to worry about wind

A solar panel less sensitive to angle will give you more production since it will start producing electricity earlier in the day and stop producing later in the day.

After some research on the subject, I found out that SunPower panels lose 3% in production going from 30° to 10°, while Trina/polycrystaline panels lose 7%.

Recycling Solar Panels

Solar Panels are mostly glass, with small amounts of other elements bonded to the glass. 
Most panels pass the Toxicity Characteristics Leach Procedure test (TCLP) test. They are therefore classified as non-hazardous and are not regulated.

However, Solar Energy Industries Association (SEIA) members are currently engaged in developing collection and recycling processes for the solar industry.

But, since end-of-life panels do not produce a viable waste stream, at this point in time, the viability of a recycling program depends on a sufficient waste stream.

Carbon Footprint of Solar Panels

Do Solar Panels need more energy to produce than what they would produce in their entire life? Nope.

X-Series, E-Series, conventional and thin film comparison: us.sunpower.com/solar-panels-technology/facts/ 
Reliability, Production, Efficiency of SunPower solar panels: click here