So 2016 happened. You may have noticed that I decided to sit out the second half of the year with blog posts and my newsletter, opting instead to send you news article of interest. And boy was the news interesting!
Now I’m back. And I’d like to inform you that I’ve joined the New World Order!
We’ve had a busy second half of 2016. In-between the cycling holiday in France, the Dimensional Funds conference in New York City, the custodian switch to TD Ameritrade and the election of Donald Trump, we installed solar panels, batteries and lots and lots of cable. We’ve been running the home-office on sunlight since October 10th, 2016. (Well, until the winter solstice when we’ve had to plug into the grid for a few hours each day due to lack of sunlight)
As a Registered Investment Advisory firm, Next Investments is required to have a disaster recovery plan. All of our data is stored in the cloud and protected by two-factor authentication and 128 bit encryption. So yes, technically if disaster struck, we could just go anywhere and continue to work. But wouldn’t it be really cool if, while everyone else was without power, or running on loud, gas-guzzling generators, we could remain at our desks and work as normal?
I didn’t realize that these systems were so complicated though. The diagram at the right shows a sample system. (Click on the diagram to enlarge)
It turns out that configuring a solar power system is not as simple as just setting up a panel and plugging in your electronics. I needed to learn a lot.
I had to figure out how much electricity I needed to run my home-office and then figure out how many solar panels I needed. Do you know Ohm’s Law? Neither did I! On the back of all electronic products is some basic power info which may or may not include, watts, volts and amps. Depending on what information is provided, you can use a version of Ohm’s law to calculate the other numbers. Since everything I wanted to plug in was 12 volts, I only needed to know amps and watts. Specifically I needed to know amp-hours and watt-hours. (I’ll get to why later)
I used a little trick to narrow things down even more. I knew that most heavy-duty extension cords have a 13 amp max, (One of mine had a little tag on it saying this) so I knew that anything that used more than 13 amps was not going to work. (like a refrigerator) So watts was going to be the deciding factor for the size of my solar power system.
If the electrical info on the device I want to plug in showed watts, that’s great. But in order to find watts if only amps were given, I could calculate as follows. volts x amps = watts. The back of my computer showed 1.3 amps, so to find out how many watts it uses, I calculated 12 volts x 1.3 amps = 15.6 watts.
Adding up everything I needed to run my office came to about 110 watts.
Solar panels lose about 30% in efficiency when they convert the sun’s power to electricity. A panel rated at 100 watts really only produces about 70 watts. The cables used to connect your panel to your batteries also rob you of some electricity.
I needed 110 watts, so I purchased two, Renogy Solar 100 watt panels to generate about 130 watts. More than I needed. I would have a little room to grow!
Obviously you need to put your panels in the sunlight where there is nothing blocking the view in order to gather power from the sun. Luckily our building has easy roof access, (after I bought a 32 foot ladder) so putting the panels on the roof was an option.
Do you know that the sun moves? Specifically do you know that the sun moves a little differently every day? Yes, you do! That’s what gives us the seasons! So in order to get the most light on my panels, I needed to figure out what direction to face them and what angle to tilt them so that they faced the sun. Ugh!
Luckily there are many websites and phone apps that can help out. I downloaded an app onto my smartphone and faced my panels due south (not magnetic south!) and tilted them at an average angle that would gather the most sunlight for the season. (Current winter angle is 57.4 degrees) I will need to adjust the angle four times-a-year. In the summer, they will lay almost flat facing up at a 10.2 degree angle. Today, in the winter, they are almost vertical. Luckily, they always need to point south.
This was not so easy to figure out either. The length was easy to figure, (how tall is the building) but have you ever heard of an MC4 connector? Do you know what gauge the cable should be in order to carry the required amount of electricity without melting?
Neither did I.
In the end, I bought two 50 foot lengths of 10 AWG PV cable with MC4 solar panel connectors. Why two lengths, I have no idea why. I’m assuming positive and negative.
I also needed to learn that panels connected in serial double the volts and ones connected in parallel double the watts. I didn’t need 24 volts, (That would fry my computer) so I hooked up the two 100 watt panels together in parallel to achieve about 130 watts.
Are you following so far? This is almost as hard as studying for the CFP exam!
Moving on…A solar power system needs batteries for those times when the sun is not shining. In order to keep your batteries from exploding when they are fully charged, you need something called a charge controller. Who knew batteries could explode? (I’m looking at you Samsung)
A charge controller makes the battery charging act like a football stadium. Right before the game, the seats tend to fill up pretty fast. But soon, the seats start to fill slower and slower as everyone has already arrived. Then at some point, they stop filling altogether. (like when the NY Giants are losing so badly that people stay home) When the batteries are fully charged, the controller cuts the power to them so they won’t blow up. Genius!
This is where the watt-hours come in. If we need a battery that can run my office for an eight-hour work day during a snow storm when the sun isn’t shining, we need to figure out how big and/or how many batteries we need.
Solar batteries are just lead-acid car or boat batteries. They are designated in amp-hours (AH) or watt-hours (WH). If we know one, we can calculate the other by using the same formula from above. In my case, if i want my 110 watt desk to be powered for eight hours, I would calculate as follows. 110 watts x 8 hours = 880 watt hours. Then using the modified Ohm’s Law formula, 880 WH / 12 V = 73 AH. So I would need a 73 amp-hour battery. That’s a big battery!
I decided to go with two, 35 amp-hour batteries which would give me about 420 WH each or 820 WH total. In the absence of sunlight, and after subtracting more inefficiencies when the power is converted from DC to AC, these batteries would run my system for about 6 hours. Under ideal light conditions, the panels would actually produce more power than I needed, thus charging the batteries for a rainy day.
The sun is not cooperative! besides not shining all the time, (except in San Diego) it shines with DC power! My electronics run on AC power. So to convert from DC to AC, I needed a power inverter.
This is a little more straightforward. since I would be using about 110 watts, I could get by with a small 300 watt inverter and have room to grow.
The Final System
In the end, I cheated. I bought a ready-made solar generator from Goal Zero called the Yeti 400. It’s a charge controller, a battery (35 AH) and a 300 watt AC inverter all in a nice portable package. I chained the second 35 AH battery to it using the Anderson Powerpole connectors. (More stuff to learn)
This system not only looks better than all the components hooked together with bare wires, but it’s portable! (I took it camping with my son in August. It powered a fan, an LED light and a laptop on which we watched zombie movies every night and never ran out of power)
I wish I could have received CFP continuing education credit from all the research I did for my solar power system. In the end, I learned something new though. I also now have a solid disaster recovery plan for my business and a portable zombie camping cinematic experience. It’s a pretty cool New World Order.
Tom Wright & Next Investments © 2017