Thoughts on Solar

The great website, Solar Charged Driving, features a wealth of information about the synergy between solar power and electric vehicles - whether fully electric (EVs) like the Nissan Leaf or plug-in hybrids (PHEVs) like the Chevy Volt.  We have been following the site for quite awhile and have learned a lot about upcoming vehicles and the issues associated with their development (such as the debate over adding sound generators so that blind people will know they are moving). If you are interested in EVs and particularly fueling them via solar power, this website is a must read (and their RSS feed makes it easy to follow their posts).

So we were thrilled when the Founder & Editor of SolarChargedDriving.com, Christof Demont-Heinrich, contacted us for an interview about our efforts to cross-market solar power systems with this next generation of EVs.  The result is a wonderful article that is now up on the web, aptly titled: “He wants your next car to Run on Sun.”  So true!  Please check it out, and if you like what you see, please add a comment and share it with your social network.

In the residential solar marketplace there are two technology choices for inverters - conventional string inverters like those made by industry leader SMA - and micro-inverters - like those made by Enphase Energy.  A solar PV system using a string inverter typically has only one inverter for the array and one or more series strings of PV panels are wired to the inverter.  String inverters are large, typically heavy boxes that are mounted on the wall.  For example, here is a picture of an SMA 4000US inverter mounted on the north wall of our customer’s garage:

(Interestingly, you see no conduit coming into or out of this inverter because we were able to bring all the conduit into the back of the disconnect through the garage wall, leaving a very clean installation.)

The string inverter requires all of the panels to be closely matched with preferably identical pitch and azimuth.  The inverter handles a great deal of power which means that it gets hot.  If exposed to summer sunlight, it gets even hotter.  String inverters, like this one, typically have electric fans to provide additional cooling - but that creates another possible failure point for the inverter.  String inverters come with ten year warranties.

The micro-inverter is a very different approach.

Micro-inverters, like these from Enphase, mount underneath the solar panels, so there is no large box to mount on a wall.  Since there is one micro-inverter per solar panel there are no mismatches, portions of the array can have different orientations without difficulty, and most importantly, the problem of shading is greatly reduced.  Those advantages come at a price - a micro-inverter system will typically cost 10-15% more than a string inverter system.

The question is - in the real world, is it worth that cost?

At Run on Sun we are starting to see some answers to that all-important question - and the answer is YES!  We have been monitoring three of our Enphase installations and compiling our data to see how the actual energy produced tracks with the predictions that we made based on the CSI calculator and our Solar Pathfinder analyses at these sites.  (In other words, the same prediction that the utilities make in calculating your rebate.)  Here’s what we have seen so far:

For the three systems combined, we are seeing nearly a 17% improvement in energy yield overall - with a peak exceeding more than 50% improvement.  While these results are still preliminary - after all, the oldest of these systems has only been in place for 8 months and none of them has yet gone through a summer season - we are very encouraged by our data so far.

Bottom line - if you need to maximize your system’s yield and/or are constrained at your site due to substantial shading issues, a micro-inverter system could well be the best choice for you.  At Run on Sun, we can help you evaluate the trade-offs and whichever way you decide to go, provide you with the best possible solar PV system.  Oh, and did I mention, all of our principals are NABCEP Certified Solar PV Installers?

If you spend anytime at all reading information about solar energy on the Internet you will have come across one of those ads:

“Do it Yourself Solar!”
“Build Solar Panels at Home!" 
“Go Green and Save Green!”

and on and on. Sounds enticing - after all, who wouldn’t like to green up their life while saving money? But the scammers have you squarely in their sights and their do-it-yourself kits are a ripoff of your hard earned money.

At a minimum, there are at least three good reasons why solar is not a DIY project: 1) DC isn’t AC, 2) Safety, and 3) Utilities.

Let’s look at each one of these in turn.

DC isn’t AC - Solar panels produce direct current (DC), just like your car battery.  But the energy in your home is alternating current (AC) which reverses polarity 60 times a second.  Now a very few of the loads in your home won’t care - an incandescent light bulb will burn just fine with either AC or DC.  But your air conditioning system won’t.  Nor will your TV, your computer, your refrigerator, or nearly anything else that you own.  All of them are designed to operate on AC and running them on DC will either damage them, or do nothing at all.  Yet those are the things that drive your utility bill.  A $200, DIY solar panel (assuming for the sake of argument that such a thing can even be built) will do nothing to lower those bills.  So right off the bat, the huge $$$ savings promised are just that - a “pie-crust” promise - easily made, easily broken.

Safety - Quality solar panels sold in the United States are approved by Underwriters Laboratory (i.e., “UL Approved") for safety.  Since even a single solar panel can generate dangerous amounts of electricity, that approval provides peace of mind that the solar panels sitting on your roof will operate safely for the 25 years that you will own them.  Can the same be said for a DIY solar panel?  What if the unthinkable happens and your DIY solar panel malfunctions and starts a fire.  Will your homeowner’s insurance cover the loss after they learn that you placed solar panels on your roof that weren’t UL approved?  Is that a risk you want to take?

Utilities - If you are looking to lower your utility costs, you will need to connect your DIY system to the utility grid.  Before you can legally do that, your system has to have an inverter that meets not only UL approval but also the IEEE standard to prevent “islanding”.  The “anti-islanding” feature of a modern inverter is extremely important - here’s why.  A residential grid-tied solar power system is a small power plant connected remotely from the utility’s other power plants.  If a power line goes down, the utility will dispatch a crew to repair the break.  Before doing so, they will isolate that portion of the grid so that the lines are de-energized, allowing the workers to handle them safely.  But wait - they cannot isolate your mini power plant down the street which is acting as a power-generating island all unto itself.  That means the downed power line is still hot - and deadly.  To prevent such situations, “anti-islanding” technology is built into every grid-tied inverter sold in the U.S.  Building such an inverter is definitely not a DIY project, unless you are an electrical engineer.

Funny, but those ads never seem to talk about any of this.

Sure, we have a vested interest - we are in the business of installing high-quality, safe and reliable solar power systems.  But we aren’t worried here about losing a few sales.  Rather, we are worried about solar getting a bad reputation from hucksters and scammers souring people who were excited about the possibility of going solar, but got mislead and wasted their money and their time.

We believe - and have blogged about - the absolute right of consumers to be treated ethically by the solar industry.  We will continue to write about risks to that ethical standard, whether from conventional installers doing shoddy work (see here) or from rip-off artists and scammers like these.

The last two of the eight Rights in the Solar Bill of Rights once again focus on the rights of consumers.  Here is number Seven:

7.      Americans have the right to buy solar electricity from their utility.

As utilities operate under Renewable Portfolio Standards they are required to purchase increasing amounts of renewable energy.  Utility customers should be allowed to purchase the renewable energy of their choosing, thereby voting with their dollars for the energy source that they prefer.

Some utilities, such as Pasadena Water & Power, have a “Green Energy” option that allows customers to purchase some or all of their electricity from renewables, but it does not allow them to choose solar specifically (and right now that appears to be all wind power).  By allowing consumers a choice, utilities would receive a premium for providing solar energy which can then be used to fund incentives for adding solar, thereby increasing the supply.  It would also let consumers proclaim their desire to avoid using coal-fired electricity.

The next Rights set forth in SEIA’s Solar Bill of Rights, concern those rights specific to the solar industry itself.  
In particular:

4. The solar industry has the right to a fair competitive environment.

5. The solar industry has the right to equal access to public lands.

6. The solar industry has the right to interconnect and build new transmission lines.

Let’s take these one at a time…

What does it mean for the solar industry to have a “fair competitive environment” in which to operate?  After all, isn’t solar already heavily subsidized through rebates and tax credits?  It is true that over the past few years, particularly in California, we have seen more favorable treatment for solar than in the past.  And yet, these subsidies are but a tiny fraction of the billions of dollars that the fossil fuel industries have received for decades.

According to Scientific American (citing a study by the Environmental Law Institute and the Woodrow Wilson International Center for Scholars), between 2002 and 2008, the fossil fuel industry received approximately $72 billion.  In contrast, all renewables received just $29 billion, but more than half of that - $16.8 billion - went to pay for ethanol from corn, a poor environmental choice.  Solar’s share?  Less than $1 billion.

A similar concern arises over access to public lands.  For years, fossil fuel producers have had nearly unfettered access to federal lands with the government getting a very poor return on its investment.  (For example, see this listing of Bush-era actions to open up public lands to the fossil fuel industry.)  For utility scale solar to succeed, access to public lands in an environmentally sensitive way is crucial.

Likewise, to get clean solar energy to the demand centers around the country that need it, the solar industry and others will need to construct, and interconnect into, new, smarter transmission systems.  These too will need access to public lands to make them affordable.

These rights will go a long way to leveling the playing field for the solar industry and hasten the day when a substantial percentage of the nation’s energy can be supplied by clean solar power systems.