How do we know that solar and other forms of distributed generation have arrived? Look no further than your closest utility. With solar panel prices declining over 60 percent just in past few years and with installed capacity booming we now have a coast to coast battle for your rooftop.
The latest wrinkle in this unfolding combat between utilities working to maintain their monopolies and homeowners wanting to save money was Tesla’s announcement of their Power Wall product. Looking to add sales of batteries beyond what they can use in their cars Tesla wants to hang a few on your garage wall to store some of that sun that you are not home to use during the day. This is sure to turn up the heat on utilities even further.
Most utilities have focused their efforts on being able to charge higher interconnect fees. One of the highest profile fights has been in Arizona where, “Solar-rate changes will add about $50 to the average solar customer’s monthly bill, mostly through a new “demand charge” based on their peak power demand during the month.” Considering the average residential electric bill in Arizona was $122 in 2013 a $50 fee would allow the utility to collect 40% of what they earn in revenues for delivering actual power for simply providing a connection to the grid for net metering.
So if you could store some sun while you are away at work and then use it when you arrive home you could offset a lot of your power bill without paying any interconnection charge. So for utilities counting on collecting up to 40% of the average consumers bill from solar users this is a problem.
What is far more interesting to me if if these trends can begin offering commercial users more options to harness distributed generation. To figure out if any of this can have an impact at work as well as at home I designed a thought experiment to test some figures. Some of this may sound pretty far fetched, and if you think I’m way off on the numbers, assumptions, or just nuts please comment and tell me why.
First let’s paint the picture of our office. We have about 250 people in a typical office campus of nearly 80,000 square feet. We use right around the average kWh per square foot for an office and consume 4,000 kWh per day. We currently have a 76 kW solar array on the roof producing about 260 kWh per day. The average employee lives 14 miles from work. We are located north of Atlanta, GA. Our rate per kWh is about $0.11/kWh or $12,375 per month.
Now if we wanted to deregulate ourselves for most of our power we would need to find another 3750 kWh per day. We could install more solar by putting in covered parking. If we use an example from Solaire Generation which covers 22 spaces with 100 panels we can deploy 11 units covering most all of our parking. This would provide space for 1100 panels. We could use the SunPower Maxeon X21 panel which puts out 345 watts per panel for a system total of 380 kW. Using our location’s energy production factor of 1600 as provided by the Department of Energy we can expect to produce 1300 kWh per day.
After starting with a load of 4000 kWh per day we are now down to 2440 kWh of demand. So with seemingly every available square foot covered in solar panels now what? Well since we put in the Solaire Generation unit which includes Electric Vehicle charging stations perhaps we could look to get our employees in to some EV’s.
Not for everyone for sure, but let’s say with a company rebate on top of state and federal programs we can get 150 employees using an EV. Let’s assume some buy Nissan Leaf’s, some BMW’s i3, and some buy the Tesla S. Those cars store between 24 kWh and 85 kWh per vehicle. Using a simple average let us figure we have 50 kWh per vehicle at 150 vehicles for a total of 7500 kWh of power available.
Now of course folks do have to drive to and from work. Using our average round trip commute of 28 miles and an average range of 175 miles for the pool of cars overall we have 84% of the power stored in the car batteries available for use. Let us just use 80% to provide a small margin of error or for some errands on the way home. This leaves 6000 kWh of power available for the office.
We needed a balance of 2440 kWh after the installation of our solar covered parking. So we only need 40% of that 6000 kWh of battery capacity in the cars to power the entire office. My point here is that we could do this and leave folks plenty of range to get home. Remember that we only assumed converting over half of our employees to EV’s, so those with longer than average commutes are not impacted at all and can stay on gasoline.
Now does this make any financial sense? Honestly right now probably not, but let me take the analysis as far as I can here and perhaps we’ll get others far smarter on this topic than me to chime in and correct our assumptions.
We would still have to pay employees for the power we use from their cars. The general rate in our market for residential is about 8 cents/kWh. Since we would be using 2440 kWh per day of their power from home we would be paying out $5,856 a month to employees.
Then of course we have the cost for the solar car park. Using the last 22 projects in California of this size as reference we come to $3.67 per watt, putting our price tag at $1.39 million for the solar array. If we assume no subsidies and credits are involved and use a depreciation schedule of 15 years we arrive at about $7,722 a month in expense for the car park.
So between paying employees for their power and paying for the car park we would be around $13,578 per month vs the $12, 375 per month we pay today. Close but not cheaper. We would also have maintenance on the installation. Importantly I have not factored in the expense of the power management microgrid system needed to make this all work. I am guessing those are niche products that are still pretty pricey today, but I don’t know what those cost and could find no references. If you do know, please opine.
So what is the conclusion of our little thought experiment? Well to power one’s own office park with just solar and some EV cars does indeed seem very feasible today. But if not cheaper does it matter? Why other than costs would companies do this?
I do in fact think this is what many office parks will do over the next 10 years. Why? Because grid power is forever going up. Solar power is dropping fast. EV’s are getting cheaper and more competitive with gasoline every year. This approach to distributed generation would be more sustainable, reliable, and resilient.
This is possible if not terribly practical right now not in some science fiction future. How smart will it look in another five years? My guess? This approach moves from smart and groundbreaking to simply being mainstream in another ten years.