Offgrid Solar Project Phase 3 - Complete

Phase 3 of our on-going offgrid solar project is now complete, a year after starting it. Phase 3a which was getting the new array and pole up was completed back in August. We have now wrapped up phase 3 by mounting a second pole and moving the skid-mounted array to this new pole.

This array is our original two solar panels that we have had for a couple years now and has been moved around on a ground skid from location to location. A couple winters ago we had it on the deck and unfortunately the snow on the roof unloaded onto the panels and crushed the rack and damaged one of the panels. This made us move this array to below the deck which recieved less light but was safer (or so we thought). During a wind storm, the wind picked up the array and ground skid and flipped it into the middle of the garden. Fortunately no further damage occured other than some pulled wires. From that point forward we had to hold the array and ground skid down with ropes and bricks which meant moving it to optimize the light was no longer an option. This is why this array needed to be moved to a permanent, safe location with better light.

Originally the plan for phase 3b was simply to get the second pole in the ground before the winter freeze and leave the array in it's original location for the winter. In early October we were able to get the pole cemented into the ground. As with the first pole, we used a 10 foot pole with a 4 inch diameter. The pole was mounted in a hole that was 4 feet deep, and 2 feet by 2 feet wide. The pole has two holes drilled through it supporting a 3 foot rebar cage that provide additional support as the cement sets up and prevents the pole from turning in the hole in high wind conditions. I dug this hole slightly bigger to allow for easier digging and to avoid a couple large rocks I found on one side of the hole. I ended up using 31 bags of 80 pound cement to fill in the hole for a total of 1.24 tons of cement holding the pole in the ground.

After letting the cement cure for a week, the weather held out and I decided to go ahead and move the array to its new home. I started with determining the ultimate angle of the array which ended up being almost due south. This is different then first array we put in due to the closer proximity to the forest line. After setting the angle and mounting the panel racks, I disconnected the array from its old wiring and moved the panels to the new rack. After attaching them to the new racks, I grounded them to a new grounding rod and then wired this grounding rod to the grounding rod of the other pole to make sure as much ground wire as possible was 'touching ground'.

The final piece was running the conduit and wiring from this new pole to the other pole where the circuit breakers are located. This was a total run of about 22 feet but because it was uphill, I was presented with a few challenges. I made it to the combiner box on the first pole with a total of 1 foot of wire to spare (between 4 cables). That is cutting it a little too close for my comfort, but we made it.

I tested out all four circuits and determined that I was indeed getting power from all four panels individually. It was late in the day when I was testing though and the the new array had already moved into partial shade so I will need to do further testing on sunnier days.

I completed the project by moving some of the dirt from the holes back around the base of the poles, leveling the soil and making it easier to walk around.

We are very happy with results and definately learned a lot through this phase of the project. Our total array now includes 2 205 watt panels producing a maximum of 11 amps each, and 2 125 watt panels producing a maximum of 7.5 amps each. One of the 125 watt panels is damaged and therfore the most I have ever seen it produce was 1 or 2 amps even on the sunniest of days. It is estimated that our maximum amps will be around 30 - 32 amps, but we would be happy with 20 - 25 amps.

So, what is next? Are we finally done? Well, it will take us a while to absorb the new system and see how to best use the power it is producing. We already determined that we can now cook in the crockpot on a sunny day and have all the power come from this new array. The crockpot requires about 22 amps of power which almost perfectly matches our output. We also know that we can run the home office on a sunny day without drawing down the batteries. The real test will be through the winter when our prodution goes down dramatically. We eventually need to increase the size of our battery bank up to an estimated 400 amp-hours from our existing 125 amp-hours, but that can wait until we determine how much storage we really need and how the new array is doing year-round.

Until then, stay tuned for other solar-related projects such as experiments in solar hot water and maybe even a solar-powered bike. Until then, this is Life According To Troy.

Offgrid solar project part 3a completed

For those of you following this blog, you know that I have been experimenting over the years with offgrid solar (PV). In phase 1 we had a couple solar panels mounted on a skid outside that was simply hooked to a charge controller and a couple batteries. We used these batteries in a couple mobile inverter carts to power such things as the TV and DVD player. Moving the batteries around quickly became tiresome so we moved onto phase 2. Phase 2 added a transfer switch, pure sine inverter and battery box so that we could run 4 small house circuit without having to move the batteries from the central location. This was a HUGE improvement and allowed the batteries to be continually maintained by the charge controller instead of constantly being moved on and off charging. The problem was lack of charging capacity especially in the winter. We have 2 75amp-hour batteries and due to snow load smashing one of our panels we only had a little over 125 watts (8 amp max). This wasn't bad and was able to power our home office for 11.5 hours but it took about 2 days to recharge. This is where phase 3 came in. Phase 3 started as simply getting a replacement panel for the one that got smashed by the snow load, but due to price drops in solar panels, we were able to pick up 2 Evergreen 205 watt panels for the price of the replacement panel. This meant we needed to mount the two new panels and since the old panels were just on a ground skid that had to be tied down it was decided to permantely mount the old panels also. After siting the best location for the panels, it was decided to mount them behind the garage which unfortunately was about 100 feet from the spot in the basement where the batteries / charge controller / inverter are so this meant a long DC run. Because of the work involved in phase 3, it was decided to divide the project in half and get the new panels mounted and running (phase 3a), before moving and remounting the old panels (phase 3b).

Here are the steps we went through in phase 3a:

1. Since the location of the panels was going to be behind the garage, a long conduit run was needed to go from the basement, through the garage and out into the back yard. During the early months of winter 2010 I started installing 1 1/2 inch conduit from the existing PV combiner box, across the basement ceiling and into the garage. In the garage it crossed the back wall and finally went through the wall the outside where it needed to drop about 8 feet into a buried trench. The inside conduit run was completed in the winter of 2010 including pulling the 2 1/0 cables through into the garage.

2. In the Spring of 2010 final siting was done for the array to make sure that maximum sun was obtained in that spot. After siting at over 16 different spots behind the garage, a final location was determined.

3. I started digging the hole for the support pole in the late Spring of 2010, The pole was hardened steel, 10 feet long with a 4 inch diameter. The requirements for mounting meant I needed a hole 2 feet by 2 feet wide and 4 feet deep. The first 2 feet down was pretty easy going, but then I hit rocks and compacted soil. I even hit a small boulder that ended up being a 75 pound rock that had a 2 foot diameter (this is now part of our ever-growing rock wall).

4. After getting the hole to the proper 4 foot depth, I dug a trench from the garage wall to the hole. I then drilled a hole through the garage wall and dropped the conduit down the wall and into the trench eventually ending in the 4 foot hole. The conduit had to run below grade into the hole so the conduit would be held by the concrete as it turned to go up the pole.

5. Next was building the rebar cage that would surround the pole below grade. This rebar cage was 3 feet tall, by 1 1/2 feet wide and deep. These dimensions allowed the cage to float in the hole without touching the bottom, top or sides of the hole.

6. After building the rebar cage, 2 holes had to be drilled throught the pole to allow rebar to pass through the pole and attach to the cage. These rods served the purpose of first of all supporting the cage above the bottom of the hole before the cement was poured and ultimately to tie the rebar cage and pole together as one unit in the cement preventing the pole from spinning in the ground.

7. With the hole dug and pole prepared, it was time to put the pole in the hole. Fortunately my wife was able to help me carry it out of the basement to the hole where we were able to tip it up into a standing position. After lowering the rebar cage into position and securing it to the pole, I secured the pole into a standing position with rope and stakes.

8. After the pole was standing the hole, it needed to be leveled in all directions. This was done by simply adjusting the tension on the support ropes until it was level.

9. Finally we got to the big task of pouring the cement to secure the pole. Any guess on how much cement we needed to fill a 2 foot by 2 foot by 4 foot hole? Well, it ended up being 29 80 pound bags of concrete (my estimate had been 27 bags from which I rounded to 30 to account for loss).

10. Before the concrete set I quickly tied the conduit the pole so it would set properly aligned.

11. After letting the concrete cure for a week I again sited the PV array, this time from the top of the new pole looking specifically for direction the array should be pointing and the perfered tilt of the array. It was determined that the array should be positioned to 184 degrees (South-SouthWest) and at a tilt of 34 degrees from flat.

12. Knowing the angle of the array, I then attached the pole-mount cap at the correct angle (after remembering that you can't put a magnetic compass on top of a metal pole and get a proper reading). The pole mounts went up rather quickly including the tilt bar and cross-bar supports.

13. Next was the exciting part of actually mounting the panels to the pole. This is always exciting just because you can finally see the final product instead of it just looking like a pole sticking out of the ground. The two Evergreen panels went up fairly quickly and with nice gap in between to allow for air flow.

14. After checking that the panels were indeed producing power (since this is the first time these panels were exposed to the sun), I mounted the outside PV combiner box that finally completed the conduit run all the way from the basement.

15. Wiring was the next, and in my opinion, the most fun step (ok call me a geek). I attached a grounding wire on each panel and fed it into the combiner box and then continued it down to a grounding rod that was pounded into the ground. The PV wiring was fed down through the support channels and into the combiner box where it was wired together through a couple 20 amp DC fused to the 1/0 cable that leads back to the basement. In my configuration, each panel is wired to a seperate fuse allowing shading on one panel not to affect the other panel. I also added a couple 15 amp fuses in the box that will be used in phase 3b when the old panels need to be wired. I left a little bit of extra PV wire to allow for the tilting the array up and down in the summer and winter in order to optimize the solar angle.

16. The final wiring step was to connect the 1/0 cables in the basement to the combiner box in the basement to complete the ciruit and allow the power from the new panels to flow into the circuit. After doing a complete electrical check and retightening all connection I flipped the breakers and let the power flow. A quick check indicated that everything seemed to be working normally.

The system hasn't yet been through all it's paces yet since the batteries were fairly near full, but all indications are that it is producing the power it should.

I learned a ton by doing this and I do want to thank my wife for being so supportive through the million trips to the hardware store for yet another part.

Phase 3b which is mounting the old PV array on a pole mount and wiring it into the new outside combiner box. I hope to start this this summer and fall with the goal of at least getting the pole in the ground before winter. There really isn't a hurry on this though since the old array is still producing on the ground skid, just not as much as could be.

Until then...this is just Life according to Troy

Our PV system

On April 21, 2010 our little PV system had completed generating 9 Megawatts of power since we commissioned on May 18, 2007. That is in a little less than 3 years.

Experiments in off-grid solar – Phase 2

It took me awhile, but I finally got back to my off-grid solar project. Phase 1, which was the initial build, proved very successful with the ability to keep the three batteries we have (two 75 ah batteries and one 35 ah batteries) charged and usable. We used these batteries in two portable charger carts each with a 1000 watt modified sine wave inverter to run the TV/DVD player as well as miscellaneous other uses through out the house/yard. The biggest downside to Phase 1 was that because we always had to bring the batteries/inverter to the power source, I was forced to lug the batteries around which got old pretty fast. This is the problem phase 2 would solve.

The goal of Phase 2
Phase 2 of the experiment was to add a sine wave inverter that would allow utility-grade electricity to flow through the house wiring through a small transfer switch. By doing this we would centralize our off-grid system components in the basement while still getting power where we wanted it.

Steps involved
The first step which happened earlier this year was to install a transfer switch allowing us to control 4 circuits in the house from the off-grid solar. Due to the small size of the batteries and scope of this project, we needed to run small loads so things like the well-pump were immediately excluded. It was decided to try to run the office (lights and plugs), the basement (lights and plugs), as well as a plug or two in the kitchen. We knew that we would not have enough power to run all of these at once, or even one of these circuits 24/7, but it gave us an obtainable goal to shoot for in future phases of this project. By selecting these four circuits we also gained the ability to have at least one outlet on every floor of the house that could be powered off-grid. This step was successfully completed and unit tested successfully in the spring of 2009.

The next step was the inverter selection. There are quite a few choices of off-grid inverters out there, but not a lot on the low end, and at this point I didn’t want to break the bank on a largely oversized inverter that we rarely used. I initially selected the Xantrex ProWatt 2000 SW which was a 2000 watt pure sine wave inverter that was fairly new to the market but was getting really good reviews. It had two GFCI outlets as output so I figured I could plug the transfer switch into one of the outlets and be good to go. Well, here I learned another lesson of low-end inverters. The ones that only have GFCI outlets (i.e. the ones that are really portable), cannot be tied into your house wiring because they are grounded and wired wrong. They don’t ground neutral to ground which is required in house wiring and therefore every time I tried to flip the transfer switch, I tripped the GFCI outlet breaker. Well, that sent me back online searching for a different inverter that I could use. I ended up the older technology Xantrex Prosign 1800 inverter that allowed for hardwiring the AC output and did ground neutral to ground thus being compatible with the house wiring. A quick unit test to prove that the inverter would work the way it should was performed in the fall of 2009.

Now that we knew all the major components, layout of these components became an issue. It quickly became clear that the batteries would have to be moved from on top of the table to on the floor in a box which meant building a battery box. In phase one, the two 75 ah batteries were being use separately even though they were the same age. This worked well with the portable carts, but now that the batteries were going to stay in the basement it made more sense to tie them together to increase the one time capacity to 150 ah. To allow for future expansion, I build the box to allow for four batteries, plus a smaller fifth battery. Since I also wanted the ability to isolate the batteries from the rest of the system, I included in the design a battery switch which not only allows for cutting the batteries off from the rest of the system, but also allowed for multiple battery banks. I didn’t see a need for multiple battery banks at this stage but I figured I could plug the smaller pump battery into the second slot on the switch to keep it charged but separated from the primary bank. The box was made of scrap wood I had in the shop and was completed in the fall of 2009.

After completing the battery box, it was time to move on to the wiring and rewiring of the system. In phase one the system consisted of a PV combiner box, a small breaker box and the charge controller. The PV combiner box and charge controller would remain, but the small breaker box had to be replaced with a larger breaker box to house all the expanded wiring and connections as well as the large breaker needed for the inverter. For this task, I opted for a Midnight Solar DC breaker box since it had just enough room to accommodate everything I needed including the 250 amp inverter breaker, 5 slots for other breakers (of which I only needed 4), and a DC shunt for all negative DC connections. Everything fit nicely in the breaker box although the 4/0 cables I needed for the inverter and from the battery box did prove a little challenging bend through the conduit. I was able to reuse the PV and battery breakers I had from phase 1 and added a ground fault protection breaker as well. The wiring for the batteries and charge controller was completed first and brought online late in the fall of 2009.

The last step was the installation of the inverter itself. With the breaker box set, the inverter went up fairly smoothly although because of the lack of flexibility in the 4/0 cables, the placement of the inverter had to be tweaked a couple times (thanks to my wonderful wife for understanding why we needed to “move it again!”). Once the DC wiring was completed, the AC wiring went really quickly especially since the wires were so much easier to deal with then the monster 4/0 cables on the DC side. This wiring was completed in November of 2009.

Completion
After double checking all the connections, we powered up the inverter for the first time and allowed it to run the internet modem / router as well as one laptop computer for a couple hours. There were no issues found and it all seemed to be working. We have since, plugged in the fridge to the inverter just to see how long it would run on the batteries, and we got 11.5 hours of run time off of it which isn’t too bad. The fridge is not a device we would normally run off-grid on this system but it was a good heavy load to really give the system a solid test.

Next Steps
So, where do we go from here? We first need to see how much we can use the off-grid system as is. The ideal hope would be that we could run the office 2 days a week. That may be a little unrealistic in the winter with the low amount of sun, but we will take what we can get and see how well we do.

Thoughts on Phase 3
Of course in this on-going experiment as soon as the build for one phase ends we need to be thinking about the next phase. Currently we are thinking phase 3 will be to increase our charge capacity and to move the PV array to a more optimum location. During the ice storm last year, one of the two PV panels we have was damaged and is producing at 1/10th rated capacity, so we are really running off of one PV panel at this point. The goal of phase 3 at this point would be to replace the broken PV panel and add two additional panels bringing the total to four operational panels. Since most of this work is outside work and it is currently only 30+ degrees outside, this phase will have to wait until spring at earliest.

Enjoy those local strawberries into the fall

So did everyone go out and get some local strawberries? Here in New England they are really plentiful and juicy because of all the rain. Our personal crop of strawberries is doing very well since we have already had two pickings of berries. Today we went out to a local farm (Lanni’s Orchard) to get some additional berries and came home with 25 pounds of berries. When we first started picking we didn’t think we were going to get much, but let’s put it this way, we didn’t even make it completely down two rows before we had to stop because our flats were overflowing. Not only were there a lot of berries, but they were big. We went to Lanni’s Orchard last year also and had good luck, so I can definitely tell you that it is a good local place to get berries if you are near Fitchburg, MA.

So, what do we do with 25 pounds of strawberries (plus a pound from our own garden)? Well, we eat them of course. Strawberries, like most things in nature, have a season, and you have to enjoy it while it is here. That being said, you can only eat so many strawberries during the month or so that they are truly in season, so what is one to do the rest of the year? Well, we save our fresh strawberries by canning up some wonderful strawberry jam. From the strawberries we picked we were able to can up 21 jars of fresh strawberry jam which we will be able to enjoy into the fall and winter. We also are dehydrating lots of them so they can be saved and reused pretty much anytime in the next 6 to 10 months . Dehydrated strawberries are so sweet and a wonderful treat to be eaten by itself as a snack or as a topping to yogurt, cereal or even a salad.

So, get out there and get those local strawberries while they are still in season, and if you already have, make sure to save some for those fall and winter months ahead by canning, dehydrating or freezing some. Believe me, come fall when you are still eating sweet local strawberries, you will thank me. Then again, this is just life according to Troy.