Catch Some Rays

Although I spend most of my time hooking up residential and small commercial solar, I decided my RV needed to be solar powered.  A good friend gave me some Evergreen 110 watt panels.  As they were  damaged and needed rewiring, I decided to wire them in their 24 V configuration.  As my RV has a 12 VDC household system, the batteries were already wired in a 12 VDC configuration.

I used a Solar Boost 50 battery charge controller from Solar Depot to manage the battery charging and a Xantrex inverter to run the lights, computers, printers, TV, Satellite dish and DVR.  

I installed the modules on the roof.  RVs with a  rubber roof are easier than I thought.  If you look closely, you can see where the ribs run across the top.  I found the ribs and verified them with a stud finder.  I bolted down 4 feet with (8) 2" lag bolts and a lot of Rubber goop sealant.  I ran the cables across the top parallel to the length of the rig.  I was able to run the wires down the refrigerator vent with no problems.

I mounted aluminum crossbars and 3 modules, making sure they were far enough back from the front of the rig to minimize uplift.  

We are now on solar for everything but the refrigerator and microwave.

This was a good project but took longer than a residential installation due to a number of trips to Home Depot, Solar Depot, Lowes and the local Marine supply store.  Marine supply stores are a great resource for hardware required for 12 and 24 volt battery systems.

Posted by Dennis Epp www.heritagesolar.com at 06:20 PM | Permalink | Comments (0) | TrackBacks (0)

Most Solar Inverters require that every string must have the same number of modules and must be on the same plane.

Let's explore this.

For the most part, the Maximum Power Point Tracking algorithm on most inverters chooses the best voltage and the best amps to get  P = E x I....or Power in Watts equals (E) voltage x (I) current.

If the strings aren't balanced (same number of modules per string), one string has a higher voltage than the other string. This results in the inverter trying to pick the best voltage and best amperage for the system.  The result is that any extra modules (6 in a string vs. 7 in a string) tend to lose their value.

So, if you buy this, strings must be balanced.

Fronius has an excellent white paper devoted to balanced strings on different planes.

Non-Optimal-Conditions 

If you go into the field and test modules, you will find that their voltage tends to be very similar regardless of azimuth.  The resulting conclusion, therefore, is that the voltage (constant)  x current which the inverter can't distinguish = power.  The Fronius white paper shows that modules can be placed on different planes, as long as the strings have the same number of modules per string. 

Posted by Dennis Epp www.heritagesolar.com at 08:09 PM | Permalink | Comments (0) | TrackBacks (0)

Solar modules are rated using STC, Standard Test Conditions, and PTC, PV Utility Scale Application Test Conditions.

Most module manufacturers include their STC rating right in their part number.

For example, a BP SX3195 has an STC rating of 195.  But BP also states in their literature that it has a +-9% tolerance.

What BP is saying is their 195 module may be a 195 -9% = 177.4 watt module.

Would you pay that much for a 177.4 module.  Of course not.  That is why they don't advertise it as a 177.4 watt module.

An interesting fact is that BP can't sell their +-9 modules under the German incentive programs or even under the California New Solar Homes Program.  Since they can't sell them in some of the best markets, they are dumping them in markets with deceptive marketing. 

Buyer Beware.  Check your tolerances so you know what you are really buying.

Posted by Dennis Epp www.heritagesolar.com at 02:00 PM | Permalink | Comments (0) | TrackBacks (0)

I had someone ask a question about how solar modules perform when they get hot.  Solar modules are less efficient when they are hot.  Every module has a temperature coefficient of Power Max (Pmax).  The CEC supplied a list of modules and their Temperature Coefficients.  Here are a few examples.

Module                                %/K 

Sanyo HIP-195BA3                -0.317

Sunpower SPR-205-BLK-U        -0.387

SolarWorld SW 175 mono/P    -0.47

Mitsubishi PV-MF170EB4        -0.471

Kyocera KC200GT                -0.48

Evergreen ES-195-SL            -0.486

Kyocera KD210GX-LP            -0.49

Sharp ND-208U2                   -0.495

What does this mean.

Well if Pmax is at 25 degrees C and a really hot hot roof gets up to 90 degrees C, then there is a 55 degrees C....Or degree K (Kelvin) differential.

55 degrees C x -0.317 equals 17.4% power loss for Sanyo HIP-195BA3s at high temperature

55 degrees C x -0.495 equals 27.2% power loss for Sharp ND-208U2s at high temperature

That is a 9.8 percent difference in power loss at high temperature.  Generally, high temperature would occur when the sun is at it's most intense and power losses would be most significant.

All systems are not created equally.  It really doesn't matter how big the system is in kilowatts (kW).  What is much more important is how much power it produces in kWhs over time. 

Posted by Dennis Epp www.heritagesolar.com at 01:44 PM | Permalink | Comments (0) | TrackBacks (0)

If you use a lot of electricity and have a little extra land, a solar ground mount is the way to go.  One of the important issues when installing ground mounts is what is known in the industry as "flyaways".  Basically, if you are going to install a ground mount system with a potential uplift of 50 lbs/sq.ft., you want to ensure that your expensive solar array doesn't leave the vicinity when the next Santa Ana wind comes along.  We prefer using around 3 bags of concrete per hole and schedule 40 pipe.

We have seen installations that used smaller pipe with a wall thickness less than schedule 40.  Over time, the thin walled pipe will relax due to thermal expansion and contraction.  Once the pipe relaxes and the fitting hardware fails, the potential for a flyaway is very real. Corrosion may also be a problem with thin walled pipe.  Remember that your installation needs to last at least 50 years to get the full value out of the solar array.

Once the pipe is installed, the anodized aluminum rails can be mounted with stainless steel hardware and the solar modules can be installed.

Remember to ask your contractor if the ground mount system they are installing has been engineered.  Using thin walled fence posts on your array is a really bad idea. 

Posted by Dennis Epp www.heritagesolar.com at 05:09 AM | Permalink | Comments (0) | TrackBacks (0)

Buyer Beware.  The solar industry has been attracting a lot of attention these days.  There is a lot of buzz in the investment community and we have seen a lot of eco entrepenuers joining the ranks of the solar experts. 

It is important for consumers to be very careful when hiring a contractor to install solar.  In the State of California, it is illegal to solicit, sell, write contracts or install solar without a Contractors License.  Notice that I didn't just say install.

If a Contractor advertises, the Contractor's license number must be on all advertising materials and contracts, including business cards.  This includes website pages.

If a Contractor goes to a persons home to solicit or sell solar, they must have a license. If a Contractor hires a salesperson, that salesperson must be registered with the California State License Board (CSLB).

I noticed a company the other day that is advertising heavily in the San Diego area.  I believe they had a green lizard on their advertisement.  The company does not list their Contractors license on any of their advertising or on their website.  A quick check with the CSLB shows that they are probably operating without a license.

What does this mean to you.  

If they get caught, they could be jailed for 6 months and pay a $15,000 fine.  Most likely, they will go out of business and your 10 year warranty will be worthless.

If they don't have a license, they won't be bonded, won't have workers compensation and won't have general liability insurance.  If one of their workers falls off the roof, you will be the one paying for the medical bills.  

If you want to check a contractors license, go to this site:

CSLB License Check

Be careful when hiring a solar contractor 

Posted by Dennis Epp www.heritagesolar.com at 03:33 AM | Permalink | Comments (0) | TrackBacks (0)

I get asked about the Federal Solar Tax credits for 2008.  The best guide I have found was published by SEIA.  Here is the Link:

SEIA Federal Tax Credit Guide 

Posted by Dennis Epp www.heritagesolar.com at 04:34 PM | Permalink | Comments (0) | TrackBacks (0)

I was thinking the other day about Steve Goodman and his lyrics for the perfect country song:

Well, I was drunk the day my Mom got outta prison.
And I went to pick her up in the rain.
But, before I could get to the station in my pickup truck
She got runned over by a damned old train.

Now what does this have to do with investing:

Nothing whatsoever.

Everywhere you turn, however, there is bad news.  I took a look at my IRA the other day and I can say that the stock market isn't looking like a very good place to invest these days.  I was looking at real estate and it didn't look very good either.  The bank is willing to charge a monthly fee to keep my money there.  I suppose I could get a CD and march along with inflation.

People ask me about solar as an investment almost every day.  The last time I ran the numbers, I was seeing an internal rate of return of 13% to 15%.  Wow.

When looking for an investment, it is sometimes wise to see where the smart money and the big money are going.  Many of our clients aren't very green when it comes to the environment but they know green when they see it.

Posted by Dennis Epp www.heritagesolar.com at 04:20 PM | Permalink | Comments (0) | TrackBacks (0)

We recently installed a solar array using WEEB grounding clips from Wiley Electronics.  While these clips are ETL Listed. appear to have superior galvanic properties and far superior electrical characteristics, they were rejected by the inspector.

The Wiley WEEB grounding clip, shown below, grounds the module frame to the aluminum rails. 

The inspector wanted to use the GBL4-DBT lug.  

 Notice the Stainless steel screw used to hold the lug to the module frame.

There was no course of action but to tear the array down and install the copper wire preferred by this inspector.  An email to Wiley resulted in the following comments:

Hi Dennis,

I am sorry to hear about your inspection problems.  We are always trying to talk to these guys and educate them, but it is a difficult task. Sometimes allowing them to comment and buy into the design before installing helps.

If you do want to push the inspector a bit more, I would ask why he thinks the lug method is any better.  It is not code compliant for several reasons.  First with the lug, all the current must go through the stainless steel screw.  Stainless steel is not allowed as a conductor according to the code.  It would be possible to have the screw listed together with the lug to UL467, but to my knowledge no manufacturers have done so.  A subtle point here is that the manufacturer of the lug is not providing the screw, the distributor is.

Furthermore, our own lab tests have shown that if they have the lug/screw listed, it could only be used with a 10 AWG copper wire, nothing larger, because of the high resistance of stainless steel.  Note that the WEEB is able to carry much more current because it is very thin and in good thermal contact with a big chunk of aluminum.  Most inspectors require a 6 AWG and this is also a change to the 2008 NEC.  In general most of these inspectors are well intentioned, just not very technical and uninformed. 

With regard to your electrochemical comments, I am attaching a portion of proposed changes to UL1703 by UL.  The potential difference between stainless steel and aluminum is 0.55, while it is recommended that this be 0.6 or below.  Of course, the lug method also generally uses
stainless steel although since it is not listed you don't really know what type of stainless steel.

We have a lot of info about the WEEB on our web site.  If you have any
further questions, please just let us know.

It appears that the inspector in this case was well intentioned but did not properly apply a little common sense, to the detriment of the solar customer.  

Posted by Dennis Epp www.heritagesolar.com at 03:21 PM | Permalink | Comments (0) | TrackBacks (0)

In the past several weeks, I have had a number of people inquire about self installation. Our company occasionally sells a self installation package but there is a pretty steep learning curve. Most solar packages purchased from our company and/or the internet are not complete packages.

The packages generally include the major components:
Aluminum Racking
Stainless steel hardware
Solar Modules
Inverters
Some excess USE wire with a couple of connectors on the end

What they don't include
Copper Ground wire...Grounding clips are becoming popular but are often rejected by inspectors
Tin plated copper ground lugs with stainless hardware
Ground rods as required
J-boxes
Conduit
THWN-2 Wire in various required gauges
Conduit
60 Amp AC disconnect
240 VAC 2-Pole Breakers

Some of this can occasionally be found at a local hardware store. More often, you will need to get this specialty hardware from an electrical supply.

If your Electrical Service is undersized, you may need a service upgrade or may need to have certified electrician install a service tap. You should not attempt this without proper training and experience.

Another issue is working with DC. Many of these solar systems are wired in strings that range from 450 VDC to 600 VDC. Extreme care should be used when working with these voltages.

The last issue is one of total system cost. While a self install will allow you to save some money on installation, if you are lucky, it will actually cost more money in a number of areas.

You will not get a 10 year warranty from the installation company (you)

Your California Rebate will be Federally taxed

You will have to buy your solar modules at above volume distributor prices.

If you have good mechanical and electrical skills, you may be able to complete a self installation.  Discuss this option with a solar professional and, as an option, pay for some design, installation and paperwork guidance.

Posted by Dennis Epp www.heritagesolar.com at 02:41 PM | Permalink | Comments (0) | TrackBacks (0)