Solar PV Panels and a Micro-Grid

So it’s back to your restaurant again.  Things are going well.  Since you installed the generator last week, you have the electricity you need to run your restaurant.  The smell isn’t great, but you hope it’s not causing too many clients to stay away.  And sometimes, your generator runs out of diesel.  You have to throw out everything in the fridge and restock.  So, really, it’s not going that well.  But, at least you’re open some of the time, and some clients don’t mind the smell.

But, there has to be a better alternative than this.  Besides a generator, there has to be other ways to generator your own electricity.  So you start thinking through a few different solutions on your way to the restaurant one morning.

What about wind?  You’ve heard that they’re starting to have some small wind turbines that you could install and generate some electricity that way.  Maybe if you install a small wind turbine on the roof of the restaurant.  Could that work?  The wind turbine produces most of its electricity overnight (that’s when the wind blows), and you use most of your electricity during the day.  So, it’s not a great fit, but it might still be an option.  You keep thinking as you’re driving until you get to the restaurant, and then you notice a problem with you solution:

It’s staring you in the face in bright beige – you have a two story building to the east, and a two story building to the west.  The wind isn’t going to blow very well across the roof of your restaurant with these two buildings there.

What about micro-hydro?  You hear they’re making great strides in the efficiency of run-of-river turbines.  Now, if only there was a river running next to your restaurant; you’d have this thing licked…

Bio-fuels!  Of course!  You could retrofit your generator to accept bio-fuels, and make your own bio-fuel from the kitchen waste.  Two years of night school to get a chemical engineering degree, and you’ll be ready to go!

What about a solar electric system?  It dawns on you as you close the blinds to shade your clients from the noon sun.  It seems like it’s fairly sunny, so you should be able to generate some good electricity.  And, you’d be generating electricity during the middle of the day.  That’s when the restaurant is open, and when you’re using the most electricity.  But, just how much electricity could a solar electricity system generate?

But, how do you keep the fridge running when the sun isn’t out and the diesel generator is out of fuel?  You remember hearing about some guy out in the woods having a solar electric system with a battery back-up.  That might work, but could you still use the generator if you had too?  What about the electrical grid?  If they figured out how to get you more reliable power, could you be connected to that one too?

(It’s time for a little confession on my part.  I knew part of the solution would involve a solar electric system and a battery back-up.  My back-ground is in commercial scale solar electric system design and construction.   Besides, it just makes sense.)

So, here are some of the facts around solar electric systems.  First, a solar electric system is typically referred to as a PV system.  (PV stands for photo-voltaic.  Photo means light, and voltaic is for voltage, or electricity.)  Second, PV systems have been around since the first function PV cell was made by Bell labs in 1954.  There were first used to power satellites, and as the costs came down they found some applications here on earth.  The first grid connected PV system was installed in the late 1970s.  The basic technology has been around for a long time, and has been proven on thousands of installations worldwide.

The establishment of a micro-grid complete with a PV system, a battery bank, and a diesel generator for supplemental electricity is the right approach for this project.  It’s also an approach that can and has been used all over the world.  The MIT Tech Review put out this article earlier this week:

There are some significant challenges with everything they’re trying to achieve with their micro-grids.  I’m facing these same challenges with the design I’m working through here.  If I had a hard time finding qualified people in the U.S. to maintain commercial PV systems, how am I ever going to find qualified people to maintain a more complex system (with the PV, the battery bank, and the generator) over the long term?  It’s definitely influenced the equipment that I’m spec’ing in (it has to be very easy to service), and the monitoring that I’m designing in (I’ll be able to remotely monitor and control the PV system and the battery bank).  Now, I just have to figure the language barrier and the 7 hour time difference, and it’ll be smooth sailing.  Stay tuned – I’ll have an entire blog post just discussing some of the non-technical challenges that are arising during the course of the project.

So a few things to ponder for next week:

-        How do you size a PV system?

-        What do I need to know so I don’t run out of electricity?

-        How will I get this micro-grid to play nicely with the electrical grid?

Some answers, some challenges, and more questions to come next week.  Stay tuned!

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