Monday, June 22, 2009

Solar Power (long post)

(Click on any image to make it bigger)

Even as a kid I have always been interested in Solar power. When I was 12 or 13 my parents gave me one of those electrical kits with the little springs that you could wire up and make all kinds of neat things. You could make a tiny AM radio that used an earphone and power it off of the solar cells. That was enough to keep me interested for life.
Over the years I ran the numbers several times to see if we could go solar. First when Katrina and I bought our house in Duvall, WA. Then again before we moved into our Puerto Rican house. The cost just couldn't be justified, not even close. Then just a few months ago I see a flyer on a co-workers desk. It was for training for solar panel systems and installation. We got to talking and he tells me there is a 75% tax credit for installing solar power and he was taking the class to become a licensed installer. Unfortunately I am not a licensed PE. In my 20+ years as an electrical engineer in the states it was never asked of me nor did I ask it of the many people I interviewed. Just another bit of PR BS that prevented me from taking the class or getting certified. None the less I wasn’t going to let that stop me especially since Elvin was licensed and taking the class. I borrowed his class book and did a lot of research on the Internet. I basically found everything I needed in his book and on the Internet. I did spend a lot of time researching everything.
But before I started looking at the technical stuff I tried to understand that “Tax Credit” requirements. This proved to be the hardest part of the whole process. It was all in Spanish so that didn’t help! Depending on the person I went to for translation I got a different meaning! Sometimes they couldn’t give me a translation!

We did our best reading the law (Ley 248) and made many phone calls (never got the same answer). Basically there was 5 million dollars set aside for fiscal year 2007-2008 for 75% tax credits for homeowners. Then 50% for 2008-2009, then 25% for 2010. Things lined up as they did for us to be on the edge for us receiving the 75%. The 5 million was spoken for and we probably just missed it! We ran the numbers. With the government paying for 75% it was a no brainer. But 50%? Maybe. With 50% it becomes a cool fun project for me that might pay for its self if oil goes back to $150 a barrel. Costs: If I had someone design and install the system it would have cost $30K. We did it for about half of that. Then figure in the tax credits and the system could cost 4 to 8K. The panels account for less than half of the system. The inverter, batteries, charge controller, and mounting HW accounts for the rest.

The first step was to find out how much electricity we actually used for the year. On average we used 7 KWH a day but that dropped to less than 6 after we got a new refrigerator. This also includes using the 5HP scuba compressor, something we have to switch over to a 8HP gasoline engine because the inverter cant power it. Since our electrical usage was less than 6 KWH a day that was the place to start the design. It would have been more economical to stay on the grid but we wanted to be off-grid. First decision done. Then I had to find out how much solar radiation we get. I am still not sure about this. I found information showing 5 to 5.5 solar hours a day for our location. The only problem I have with that estimate is how do they know how many clouds we get? 3 miles behind our house in mountains they have clouds most of the day. 5 miles to the South West and its desert. I ran the numbers using 5. I also wanted enough panels so if it was cloudy for a week we would still have enough energy to run the refrigerator and a few lights and a couple of hours of tv. That’s about 2.5 KWH a day. I was told to expect about 20% output with thick clouds. 2000 Watts of panels for 5 hours a day is 10KWH * 20% is 2KWH. That’s close.

I searched for companies on the internet and locally that sell solar stuff. I really wanted to buy locally but the prices these guys were charging here were insane, 25% - 40% more than the internet and they didn't have most things in stock! I found a company that had good ratings with the BBB and they had good prices. They gave us really good prices and service. Not everything went perfect but I would definitely recommend them and use them again. They are now selling a pallet of panels (200Wx28pc) for $2.86 a watt. I think I kinda pushed Elvin into really making this happen. By us ordering together we split the shipping and we were able to use a whole pallet of panels. Our order was so large we got another discount. With the 75% tax credit ready to run out this was our best chance to do this. I made the calls, got the quotes, and got the ball rolling while Elvin took the class, took the test, and got certified. Without him I wouldn’t have been able to do this.

I found that our best deal was a pallet of Evergreen Solar 205W panels. I needed 10 and Elvin could use the other 18 (I think he only wanted 16 but he took the 18). With this decided I needed to figure out which inverter to use. I picked the Xantrex 4548 on/off grid inverter. I looked at many others and went back and forth. I am glad I bought the Xantrex. Since I went with the Xantrex inverter I also picked the Xantrex charge controller.
This stack of 10 panels may produce all the electricity Katrina and I will use at home for the rest of our lives.
The batteries I selected were Deka 8L16 6V 370AH@1/20C. These things weigh more than Katrina! We got eight of them for a bank capacity of 48V*370AH= about 18KWH. The less you use them the longer they last. The power we use from 5pm to 7AM is 3 – 4 KWH, about 20 to 25% of the battery capacity. You never want to go below 50% capacity because you reduce the battery life.

20KWH of storage! Arh Arh Arh. 8 6V batteries in series. All housed in a nice plastic shed Katrina found at Home Depot. If there was an eclipse for two days and we didn’t conserve we would be close to the 50% limit but since that won’t happen I expect to get 20% (2KWH) output on the cloudy days. With a little conservation I would expect we could go 5 days without hitting the 50%. More conservation and we can go longer. I looked at circuit boxes for all the breakers and connections for the system. Xantrex wanted something like $1500 for their box. I had the bright idea I would make my own for just a few hundred. I found an e-panel from Midnite solar and it only cost $700. I started looking into the documentation for it and started pricing parts for my panel. Katrina pushed me to spend the few hundred dollars extra and get the Midnite solar e-panel box. I am glad I did. It would have taken me forever to build that box.

This is the Midnite Solar E-panel with the Xantrex charge controller attached. Everything is all wired up.

I also went with the Midnite solar Combiner box. This box is on the roof and combines all the panel arrays.

Mounting the panels:
This was physically the hardest part of the whole process. We researched all the commercial systems available. I haven’t seen any in person but I thought they were weak and they also cost way too much. We decided to make our own. Whatever we did it needed to withstand a strong hurricane. I also didn’t want to drill to many holes in the roof. I wanted to go with Aluminum but after checking some out I didn’t feel it would be strong enough. We looked at 1/16” 2x2 and doubled them up to try and see what 1/8” would be. They sagged under my weight and I was not jumping on them. I then looked at some 16 gauge 3x3 Galvanized Steel. I jumped up and down on it and it didn’t bend very much at all. No need to get the 14 or 12 gauge, this stuff is strong.

Elvin went with 1/8” 2x2 Al and it should be strong enough. I had a design in mind but at the last minute changed it to match Elvin’s. The angle of our panels can be changed. This is important if a storm is coming. We can lay the panels almost flat. It was also our idea to lay them flat in the summer to improve on the collection of solar energy but as I built my first frame I saw shadows on where the panels would be. Even a small shadow can reduce the output by 50%. I am going to leave my panels at 17 degrees unless a storm is coming. Elvin built two sets of legs he can change out so he won’t have shadows. After a year let’s see if he is still changing them :)

Here is the bulk of the system all wired up and ready to go. It was a lot of work and I had to miss a few good days of SCUBA diving to get it all done. Just look at the mess below. That mess got smaller as I used more and more of the supplies.

This is all the technical stuff. It's not really that complicated once you have all the information.

We have harvested 8 to 9 KWH a day. The peak output was 2150 Watts. We are not using 8KWH a day. Most of that extra power just gets waisted. Battery charging is very inefficient. Getting 90% of the charge is somewhat efficient but the rest of the charge isn't. Once the system has run for a few months I'll know if we really have extra power to waste. If we have a few extra KWH I might think of using it to heat some water in the day. I do want to keep night usage at a minimum to make the batteries last longer.


Anonymous said...

Jeff and Katrina,

Thanks for the much anticipated update and congratulations on achieving your goal! Pictures look great! Its pretty amazing that you saved so much by doing it yourselves. You should be working for NASA on solar arrays, LOL!

Just today I was listening to NPR and they featured this group called "One Block Off The Grid", here is their website:

They mentioned that prices of solar power items in the US have come down more than 50% because of lack of demand due to the recession. We plan to subscribe to their mailing list and perhaps attend their training sessions if they offer them in DC.

It doesn't sound like you are using your AC at all, do you feel you even need it? We grew up without it. Also, have you changed your light bulbs to fluorescent? We have always done that in our homes and we always see a great reduction in power consumption. What do you use for water heating now?, do you feel you even need a water heater? That is another thing that we did not have for a while until my dad found this electrical heaters he installed right on the shower heads. The water was just warm off the shower, but good enough. It seems that living in the tropics can be very uncomplicated because the weather is so nice. Of course there is plenty of sun.

BTW, I know in PR they pay a lot of attention to whether you are a PE or not. The "Colegio de Ingenieros" has always encouraged this, dunno exactly why. I graduated and moved to mainland without ever taking the test -- have never needed it here either.

I wish you the best luck dealing with the government for the tax credit stuff.



Anonymous said...

We havent used the AC. It is hot but if I win the fight I can turn on the ceiling fan at night and that works fine for me. Katrina still sleeps with a blanket.

Most of lights are fluorescent. There are a few we still need to change.

We use an instant on propane hot water system. The little electric heaters on the shower heads was not engough for us.


Mike said...

Awesome looking job. I'm impressed, and only hope my efforts come out as well. I tend to start off well, and then get sloppy. Can't afford to make a mistake with >17Kw under my assets.

Anonymous said...

Mike - That's what you need a partner for! Sometimes things that work look like crap and vice versa. Jeff did a wonderful job, but there were some heated discussions about where to run conduit and where to arrange boxes etc. Some things that matter to one person don't matter to the other and having someone else to look at it helped. Jeff also had Elvin, a friend who also installed a system to work with. So we have a clean, simple looking, easy to paint the roof and walls around system. I did all the house painting so making sure the conduit lifts off the clamps so I can paint was a consideration Jeff never thought of. You also need some space for fingers to install bolts etc to attach the panels. Things you don't consider until you have made the mistake! We are pleased and self sufficient! Hoorah! katrina

Anonymous said...

very cool. But although florescent lights use less power, they are TOXIC made with mercury. Keep that in mind :)

Anonymous said...

CONGRATS to you guys. Very cool thing you did

cara said...

I think it looks amazing. I'm not sure I would have had the patience that you had though!