For the last few weeks, we’ve been talking about a fictitious restaurant you’re operating in Brooklyn. In week one, you built the restaurant only to discover that the electrical grid can’t provide you power. In week two, you solved your power problem by purchasing and installing a diesel generator. You were able to turn on the lights and open the restaurant. But, you ran into a problem with the smell of diesel in the restaurant, the generator kicking out black smoke, and some problems with your diesel delivery that forced you to throw out much of your food. In week three, you began thinking about how to generate your own power, and create what’s commonly known as a micro-grid. (Read Seyi’s article to learn a little more about micro-grids.) You thought through wind, biomass, flow of river turbines, and had finally decided on giving solar a try.
This week, we were going to start looking at how to design a solar PV system. We were going to answer the following questions from last 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?
I’m calling an audible. We’ll cover those questions next week. With Hurricane Sandy hitting the east coast last week, it makes more sense to take a detour and talk about our reliance on electricity, how electricity was restored after Sandy, and how your little restaurant located in Brooklyn would have fared through such an ordeal. To set the stage, here is a picture of New York City a couple days after Sandy hit; part of the sky line is lit up, but everything below 39th Street is still in the dark:
Electricity Restoration Post- Sandy
From an electricity point of view, what was the response to Hurricane Sandy? Let’s start with some of the high level facts just so we understand the magnitude of what happened. Hurricane Sandy knocked out electricity to about 8 million people. Katrina only took out about 6 million. As the storm was coming up the coast, electrical linemen were already heading to the East Coast to be there for the aftermath. (The Sunday before Sandy hit, my buddy who is a lineman for ComEd in Illinois was already on his way to Baltimore.) When many people were leaving, he and his fellow linemen were heading into the breach once again to help restore electricity as quickly as possible after the storm. Electric utilities have a Mutual Assistance pact for situations like this, so they can call on the resources of other utilities to help in situations like this. (Mutual Assistance) All told, over 65,000 linemen made their way to the East Coast to help. They came from everywhere. Linemen from SDG&E (San Diego Gas & Electric) and SCE (Southern California Edison) flew on military transport aircraft to the East Coast. Trucks and crews drove up from Alabama and Louisiana, and down from Quebec. Several thousand of them are still there.
Each utility has a set plan for restoring electricity in the case of an outage. It’s fairly standard across all utilities. First, they repair the main lines from the generation plants to the substations. Second, they repair the distribution lines. Those distribution lines that restore electricity to public health and public safety buildings always get repaired first. (So, if you live in the same neighborhood as a hospital, police station, or fire station, you’ll probably get your electricity back much faster.) They continue by going after the distribution lines that will restore the electricity to the most number of customers. They continue down this priority list until all distribution lines have been repaired. Third, and last, the utility will repair service drops or electrical meters that prevent individual customers from receiving electricity from the distribution grid. So, if a tree falls on the wires between your house and the closest utility pole in a large storm, you might be without electricity for a while.
Your Restaurant in the Aftermath
Let’s get back to your restaurant. It’s great to know how utilities are going to restore electricity, but at the end of the day, you care about when you can open your doors again, and if it will happen soon enough for you to be able to save any of the food in your fridge.
(As an aside, I set the restaurant in Brooklyn mainly for two reasons. First, most Americans have some concept of Brooklyn, and can picture a neighbor and its people that could be a part of Brooklyn. Second, this fictitious story is mirroring a real project that I’m working on in a city slight smaller than New York in Nigeria. In that case, the context of Brooklyn also works as a proxy for Lagos, Nigeria. I never imagined anything like Hurricane Sandy would happen in the weeks that I’d be writing this blog. But, I digress.)
So, if you had the full micro-grid set up, how would your restaurant fare? The truth is, you’d probably be doing pretty well, assuming all the equipment remained mostly intact. Let’s check out the components of your micro-grid and see what could have happened.
PV panels are designed to handle very harsh conditions, and local building codes require that the structure that holds them be able to handle the 50 year storm. In a place like Brooklyn, it means designing something that can handle 110 mph winds. (Hurricane Sandy’s winds were less than that by the time it hit the area.) So, your PV panels would still be on the roof. What about projectiles going through a PV panel? They are made of glass after all. That certainly is a possibility, and I have seen a few instances of it occurring. However, PV panels are designed to handle 1 inch diameter hail at 50 mph. Unless it’s a fairly large piece of debris traveling very fast, your PV panels will probably be fine. (Remember, PV panels cannot be turned off even if they are damaged. They will produce electricity whenever they are exposed to light. Be very careful around broken PV panels. They can be very dangerous.)
What about your batteries? It’s really going to depend on where they’re installed. The National Electric Code requires that certain guidelines be followed when installing batteries. My recommendations are to install them at least 3 feet off the ground, and in an area that is protected. (Let’s face it, if there’s more than 3 feet of water coming through your garage, chances are you’re going to have bigger problems than figuring out how to play Angry Birds on your iPad.)
The rest of the equipment is also fairly robust and should make it through most storms without issue. However, it’s always a good idea to inspect all the wires and the remainder of the equipment for damage or other issues.
In this case, you lucked out. Your micro-grid made it through just fine. You have electricity when the rest of your neighborhood is dark. You know you’re eventually going to run out of diesel fuel in a few days, but you have a good design, and you know that the electricity produced by the PV panels will at least keep the critical loads going indefinitely. (We’ll discuss the proper sizing of the battery bank and the PV system over the next couple weeks.) But, that’s a very minor concern right now.
Right now, you’re grateful you can help out your neighbors. You’ve given them a place to charge their phones so they can reach out to their family and tell them they’re okay. You’ve given them a place to sit and have a warm meal as a family for the first time in days. (And, you’ve helped reduce the strain on the grid when they bring it back up because your load is completely off-line. More about this later.)
But, what you’ll remember most is being able to bring the linemen working to restore electricity a hot cup of coffee at the end of their 16-hour shift. You bet you’ll be able to remember that exhausted, grateful smile forever.