Categories: All About Solar Power, Electric Cars that Run on Sun, Energy Efficiency, Energy Storage, Safety

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05/10/15

  04:49:00 pm, by Jim Jenal - Founder & CEO   , 1451 words  
Categories: All About Solar Power, Solar Economics, Residential Solar, Ranting, Energy Storage

Elon Musk's 3-Biggest Powerwall Whoppers

Elon Musk is a visionary and a showman, but occasionally his enthusiasm for his vision gets way out ahead of reality.  Nowhere was that disconnect more on display than this past week when he made his much talked about announcement of the Tesla Powerwall battery storage system.  While we share the vision for the potential of battery systems (such as the one Enphase Energy is set to release later this year, albeit in a far more understated fashion), when 38,000 people go online to order a product that doesn’t yet exist, it is time to debunk some of the more exorbitant claims made by Musk. 

Here are the three biggest whoppers that Musk made during his Powerwall presentation (video below).

Whopper #3 - Power for an ice storm or other significant grid failure event

Musk touted the “peace of mind” that would come from having the Powerwall, and said, “if there’s a cut in the utilities you’re always gonna have power, particularly if you’re in a place that’s very cold, now you don’t have to worry about being out of power if there’s an ice storm.” (See video at 8:35.)

The Powerwall unit that Musk was talking about that was designed for “daily cycling” was a 7 kWh unit that is priced at $3,000.  The average home in the Run on Sun service area uses 25 kWh/day.  So a single Powerwall unit provides roughly one quarter of the energy demand of an average home.  If your desire for “peace of mind” means running your home for a full day in normal fashion, you will need to purchase 4 Powerwall units (assuming you have the wall space to mount them) and that will cost you $12,000.

Of course, many outages last longer than a day.  The longer you want to stay powered, the more units you will need.

Whopper #2 - Powerwall will work with existing solar systems

Musk insisted that Powerwall has been designed to work with solar systems, “right out of the box."  (See video at 8:25.)

Except… that the Powerwall is designed to fit between existing solar panels and the DC-AC inverter(s) in the system (i.e., on the DC side of the system).  But here’s the thing - the vast majority of inverters are what are known as “grid-tied,” which means if the grid goes down, the inverter shuts off, and stays off until the grid comes back.  If the Powerwall is on the DC side, there is no way for it to “mimic” the grid (which, of course, is on the AC side), and so the inverter will shut off.  While the inverter could certainly be replaced with a hybrid inverter (that can work both independently and tied to the grid) such a replacement is a pricey undertaking and certainly not a plug-and-play installation.

But Musk, like the true showman that he is, saved his biggest Whopper for the end…

Whopper #1 - You can go off grid… for $3,500!

Warming to his subject, Musk really brought down the house with his most outrageous claim of all:

You could actually go, if you want, completely off-grid.  You can take your solar panels, charge the battery packs and that’s all you use.  So it gives you safety, security, and it gives you a complete and affordable solution.  And the cost of this is $3,500."  [Gasps and applause from audience.] (Video at 8:55.)

No.  No you cannot.

Let’s unpack his statement.  There’s two major claims here, neither of which is true.  The first is that you could go completely off-grid, and the second is that it would cost you $3,500.  So let’s start with the easy one to disprove, indeed, we already did above: this won’t cost $3,500.  The Powerwall provides 7 kWh of storage.  The average house uses 25 kWh/day.  If the battery has to run your house for just one day, you would need 4 Powerwall units at a cost of $12,000.  (The 7 kWh unit is the one designed for daily cycling - what you need to go off-grid, and it costs $3,000 - if you could actually purchase one, which you can’t.)

So that’s easy to debunk.  But what about the second, more fundamental question.  Can I use this Powerwall system to go off-grid without changing my middle-class, suburban lifestyle?  For most folks the answer is simply, no.  Here’s why.  When you go off-grid you need to be able to meet all of your energy needs all the time without assistance from your local utility.  To do that, you need a battery system large enough to last you during the longest typical shortfall of available energy (i.e., how many stormy/cloudy days in a row will you see), plus a solar array large enough to charge that battery on sunny days while meeting the household needs.  Turns out, that is quite a lot of both.

Folks who design off-grid systems (very few of which are found in areas like Pasadena), typically design for three (or more) days of self-sufficiency (or autonomy, as they put it).  For our typical, 25 kWh/day home, that would require storage of a minimum of 75 kWh.  But according to Tesla, you can only stack a maximum of nine Powerwall units, which limits you to 63 kWh.  Sometime around noon on that third day without sun, your house will shut down.  Oh, and that much storage will cost you $27,000.

What about the solar array side of the equation?  Let’s start by asking how big an array can you fit on an average house?  House sizes have trended bigger in the past couple of decades, so more recently built houses are an overstatement of the average house out there.  Still, to have a starting point (and to give Musk the benefit of the doubt), let’s assume that our average house is 2,400 square feet (a fair estimate based on US Census data), and that it is optimally designed to maximize solar production: a near perfect square with a true south face, pitched at latitude (34° here in Pasadena), with no shading.  Of course, we still have to give the Fire Marshall the desired setoffs so that gets us to 1,115 square feet of roof space (math available upon request), enough for 62 LG 305 solar modules, but because we need to use a hybrid inverter with fixed string sizes, we will drop that down to 60 solar modules. That yields an 18.3 kW system which at $3.50/Watt would cost a cool $64,000 - and be bigger than our biggest ever residential installation. 

So the Sixty-four Thousand Dollar question becomes: How well will that do on meeting our needs?  Per the CSI calculator, this maximal system will produce roughly 29,000 kWh in Year 1, or an average daily output of 79.5 kWh.  (Less in the winter, of course, when you are most likely to see those cloudy days.)  After providing for my daily needs of 25 kWh, I have 54.5 kWh to spare, not quite enough to fully charge my batteries (which require 63 kWh).  A scenario where I have two cloudy days, followed by one partly sunny day, followed by two more cloudy days could easily leave you in the lurch.  And for this you paid a total of $91,000!  If you live somewhere with poorer weather than what we find in the Run on Sun service area (i.e., pretty much the entire rest of the country!) your performance will be even more dismal.

The true value of storage

The sad part of this whole thing is that battery storage combined with solar is going to be huge, but not for the reasons Musk alluded to in his speech.  The future of utility rates is the shift to time-of-use rate structures - a fact already well and painfully known by our clients in SCE territory, and soon to be seen by everyone.  Time-of-use rates, where utility customers pay more for energy during the peak part of the day, are the only way to match utility costs with customer charges.  (It is the head of the Duck in the famous Duck Curve below.)

The famous duck curve

That “overgeneration” that drives down demand at noon is presently fed back to the grid, where the grid operator has to modify the power mix to accommodate it - in essence, it is wasted.  (Although presently, net metering customers get full retail credit for it - something, that in all likelihood, will soon go away.)

But add storage to the mix, and you shift that overgeneration from the middle of the day, to the evening peak hours, benefiting the time-of-use customer as well as the utility.  It is the way to bring about a peaceful end to the utility-solar wars, and it is the true benefit of storage to solar customers - without oversizing either your solar array or your storage system.

So let’s all get excited over solar with storage, but for the right, and much more cost-effective reasons - and not the nonsensical hype being spewed by that super showman, Elon Musk.

04/20/15

  09:40:00 am, by Laurel Hamilton, Projects Coordinator, Run on Sun   , 374 words  
Categories: All About Solar Power, Solar News, Climate Change, State of Solar

Top 3 Ways Solar = Water Conservation

After 4 years of severe drought and this year’s winter snowpack at a pathetic 8% of typical levels, it’s obvious that California will have to find real solutions as populations rise and the effects of climate change worsen. We rely on the High Sierras’ snowmelt throughout the year for everything from our green lawns and fresh food (throughout the US) to our hydroelectric power.

Governor Jerry Brown’s recent mandate for cutting water use by 25 percent was overdue and necessary, but communities will have to step up conservation efforts in a big way. Ever since the Governor’s big announcement ideas for how best to curb water use have been flowing. So why should PV solar power generation be at the top of the list? What does water conservation have to do with solar?

    1. As noted previously in “Thirsty? Think Solar!“… compared to other energy sources, photovolataic solar energy systems have the lowest life cycle water use.  Increasing the amount of electricity generated by PV directly reduces our water demand
    2. Once a big player in California energy production, hydropower dropped from 12 percent in 2013 to just 6 percent in 2014 due to the extreme drought conditions. But solar has stepped in to fill that gap, with production more than doubling to provide 5 percent of California’s power in 2014—and that figure doesn’t even count rooftop solar! According to the Energy Information Administration, solar PV and concentrating solar power together offset 83 percent of the total hydropower decline.
    3. With drought comes a severe shortage of rainy days. Anyone with solar panels knows the joys of monitoring your energy output on a sunny day and the much sadder numbers that result on a gray day. As the drought persists, California’s sunshine provides an endless resource that should be tapped.

Solar is an increasingly important solution to water scarcity as well as energy security. With no sign of a solar slowdown in California—we are the first state to get 5% of its energy from solar—strong generation records are likely in coming years. While solar has been included in some communities’ plans to reduce water use (such as in the Los Angeles “pLAn“), many people are unaware of this solution. Communities, individuals and businesses installing rooftop solar can make a real positive difference for California’s dire water situation.

03/28/15

  04:00:00 pm, by Jim Jenal - Founder & CEO   , 361 words  
Categories: All About Solar Power, Residential Solar, Ranting

Who has the Edge? 3 Reasons to Pick Enphase over SolarEdge

SolarEdge has gotten a fair amount of buzz this week thanks to their IPO, but it made us think that maybe it was time to revisit the question—who really has the edge: DC-to-DC “optimizers” like SolarEdge or Enphase microinverters?

Enphase Microinverter Which would you choose? Solar Edge Optimizer
 Enphase Microinverter    SolarEdge Optimizer

 

In our view this is a bit of a “no-brainer” and it really comes down to the following three reasons:

Reason #3 - Integrated Grounding — In every solar array, all metal surfaces have to be grounded for safety.  Enphase microinverters now feature integrated grounding, which eliminates the need for a separate equipment grounding conductor.  SolarEdge does not have this feature and, depending on the jurisdiction, may require the use of a dedicated copper conductor to be run from one unit to the next.  This increases both labor costs as well as part costs (copper is expensive these days!).  Far better to have that grounding built-in at the factory than assembled on the roof.

Reason #2 - Easier Installation — Beyond the need for that equipment grounding conductor, the SolarEdge system requires the installer to not only mount the optimizers on the roof beneath each panel, but it also requires the installer to mount one or more heavy (51 to 88 pound) inverter(s) on the wall.  In contrast, Enphase combines everything into one unit, so there are no heavy inverters to mount to the side of the client’s house.

Reason #1 - Greater Reliability —The number one reason for us at Run on Sun is the greater reliability you get from using Enphase.  Frankly, the SolarEdge approach combines the worst of both alternative approaches (i.e., string inverters versus microinverters).  You are still putting power electronics in the demanding environment of a roof, AND you have combined that with a single point of failure with the inverter back on the ground!  When you use Enphase microinverters you eliminate that single point of failure and you are going with the industry leader in creating reliable, roof-mounted power systems.

Put all of that together, and we think Enphase microinverters provide the greatest value to our clients, which is why we feature them in all of our solar power systems, despite the occassional “buzz” other approaches might generate.

03/20/15

  08:32:00 am, by Laurel Hamilton, Projects Coordinator, Run on Sun   , 420 words  
Categories: All About Solar Power, Energy Efficiency, Energy Storage, Solar Policy

50% Renewables by 2030...How Will California Do It?? - Part 1

California has a long-standing reputation as a clean energy trendsetter. The state leads the nation in solar energy usage, energy efficiency overall, cleaner cars and energy storage. Currently on track to reach our goal of one third energy derived from renewable sources by 2020…Governor Jerry Brown kicked it up a notch in January by proposing California achieve an unprecedented 50 percent energy from renewable sources by 2030.

How will California accomplish such an ambitious target? This is the first in a series of blogs in which Run on Sun will addresss the challenges and possible solutions to reaching 50% by 2030 as opportunities unveil.

50% by 2030: Part 1 - Maximize Urban Spaces

SoCal's Ivanpah Solar Electric Generating System

Ivanpah Solar Electric Generating Station

While rooftop solar is great for offsetting the usage of those fortunate enough to be able to invest in an array, most people tend to think utility-scale solar requires wide open spaces only available in remote parts of our state. The best example being Ivanpah, the world’s largest solar power plant - generating 345 megawatts on five square miles near the Cali/Nevada border. However, growing to 50% renewables using vast spreads of desert solar arrays has the potential to harm ecosystems. Far away solar farms also incur enormous infrastructure costs just to transport the power from the source to your toaster.

Fortunately a new study provides evidence that we needn’t look further than our urban back yards to find sufficient space for solar. Stanford researchers published their findings in the March edition of Nature Climate Change:

We tested the hypothesis that land, energy and environmental compatibility can be achieved with small- and utility-scale solar energy within existing developed areas in the state of California.  We found that the quantity of accessible energy potentially produced from photovoltaic (PV) and concentrating solar power (CSP) within the built environment exceeds current statewide demand. 

Westridge School

Urban solar installed at Westridge School by Run on Sun

The urban landscapes we design are already great at capturing the sun’s rays, as evidenced by the heat island effect. It turns out we have the capacity to develop enough solar power to meet three to five times California’s demand just by utilizing urban flat spaces such as carports and rooftops. Obviously developing small and utility-scale solar in our built environment greatly improves efficiency and cuts infrastructure costs by generating power directly where it is used.

As the study’s authors note, it’s important to remember there will always be trade-offs. It’s not an all-or-nothing, urban-or-rural question but looking more closely at the opportunities for solar in our urban backyards should be a priority.

03/09/15

  05:43:00 pm, by Laurel Hamilton, Projects Coordinator, Run on Sun   , 381 words  
Categories: All About Solar Power, Solar News, Climate Change

Solar Impulse Launches Zero-Fuel Flight Around the World

http://info.solarimpulse.com/uploads/thumbs/860x576/2015_02_26_Solar_Impulse_2_RTW_First_Test_Flight_AbuDhabi_Revillard__09.jpgSolar Impulse is the first airplane to fly day and night on solar power alone. To be clear folks, that means 22,000 miles without a single drop of fuel.

Run on Sun has been following the exciting developments of Solar Impulse since it’s prototype began its groundbreaking test flight across America in 2013.

After the lessons learned from the American flight, an upgraded Solar Impulse 2 was developed with a wingspan wider than a Boeing 747, more than 17,000 solar cells and 1,300 pounds of batteries. Amazingly, the aircraft still weighs no more than an average car!

Finally, this  morning, on March 9th, 2015, Solar Impulse 2 and her team were ready to embark on their record-breaking aeronautical journey around the world. The first leg officially departed from Abu Dhabi at 7:12AM UTC+4. Landing in Muscat, Oman at 20:13PM UC+4 pilots Bertrand Piccard and Andre Borschberg rested for a few hours before continuing onward to Ahmedabad, India.

With a top speed of 50 mph, the entire circuit is planned to take four or five months before returning safely back to Abu Dhabi. You can follow their flight online as well as chat with the mission control center and view cockpit measurements like solar battery storage and pilot heart rate!

Solar Impulse is not only about accomplishing the first round-the-world solar flight. Behind the development of this technological feat lies a very powerful message. Piccard and Borschberg are using each landing as an opportunity to reach out to governments, NGOs, education centers, and the broader public to share what is possible with clean technologies.

“We shouldn’t be listing targets, but rather solutions – ways of meeting those targets. Because these solutions exist. Our society could already cut energy consumption in half by replacing old, outdated, polluting technology with clean technologies. Couldn’t we, all together, persuade governments to modify the legal framework so as to encourage the replacement of polluting technologies by cleantechs? That would at least make debates constructive and international climate conferences interesting.” - Bertrand Piccard

In conjunction with Solar Impulse’s round-the-world flight, the pilots started an online campaign called “Future is Clean”. In December 2015, they will share the largest collective voice in favor of clean technologies with global leaders at COP21, the United Nations Climate Change Conference in Paris. You can add your pledge and share with your networks at www.futureisclean.org.

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Jim Jenal is the Founder & CEO of Run on Sun, Pasadena's premier installer and integrator of top-of-the-line solar power installations.
In addition, Run on Sun offers solar consulting services, working with consumers, utilities and municipalities to help them make solar power affordable and reliable.

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