Lessons from solar: taking responsibility

We’ve been off the grid for a few days now. Everything is going quite well. As we’re becoming more acquainted with the ability of our system to provide our electric needs, we’re being very conservative in our usage, and we’re enjoying it. All of us keep an eye on the battery monitor which we usually have displaying the current amp hour rate (net gain or loss), watching to see what each item we turn on uses. Sometimes, one of the children will look at it and say, “Hey, someone has a light on” based on the number displayed.

The challenges associated with being off the grid are exciting and we are embracing them. It requires us to take responsibility for our power consumption, and we find ourselves paying more attention to the weather, whether cloudy or sunshine. This is a good thing and teaches some valuable lessons.

When connected to the utility grid, I believe most people don’t think much about the power they use and don’t equate that with the amount of coal required to generate it (as Anne said last night, most people don’t think about how much of a mountain it takes to support their power needs each day). The power is always there in practically infinite supply, and it really doesn’t cost much. Besides, we don’t see and realize the amount of electricity we use when we flip on light switch, open the hot water tap, boil water on the stove, or vacuum the carpet.

If people were aware of the rate at which their appliances consume electricity, would it lead to more conservation? If you turn on the stove burner and see that it is consuming the equivalent power of 24 100-watt light bulbs, would it make a difference? If you saw that your vacuum cleaner is sucking in power at the rate of 1.4 kilowatt hours, would that matter? A regular refrigerator uses about 2 kilowatt hours a day, every day. How much does a TV left on all day consume? What about a computer? In general, we don’t know and don’t think about it.

When our electricity is derived from the sun via a limited amount of solar panels and components that are not 100% efficient, we pay a whole lot more attention to what we’re using and what we’re gaining. Our inverter consumes 12 watts an hour and is displayed as 0.5 amps on our battery monitor. This is on 24 hours a day. A 12 watt CFL light bulb also uses 0.5 amps. When the refrigerator runs, the usage jumps up to about 7 or 8 amps and settles back to about 5 amps. We watch these things and know what they mean because we are connected to our electricity source and know that we must conserve.

The local lineman for the electric company was interested in our solar setup. I told him the first three things to do when going off the grid were conserve, conserve, conserve. I explained that our goal was to use, on average, 1.5 kilowatt hours per day, an amount that many families use in an hour. He commented that he couldn’t get his kids to conserve, because they have to have their TVs and games and stuff. I guess, they would feel deprived and would resent taking responsibility for the usage (another way to think about conservation). We don’t feel deprived; we are motivated to generate and use what we need, not mindlessly consume. It’s a challenge that we welcome and are excited about.

So far, we’re doing really well. As I said, we’re enjoying the challenge and opportunity to be off the grid. It fits with what we want to do and with our outlook on life and moral commitments (homesteading is a moral commitment, but that’s a topic for another time). Wouldn’t the world be better if fewer people were disconnected from their consumption (whether electricity or in other areas)? That doesn’t necessarily mean being off the grid, just taking responsibility for their usage in more meaningful ways than just paying a monthly bill.

We just threw the switch!

We did it! We are off the grid!! Wow, this is cool!

I wired the battery meter (Bogart Engineering Trimetric 2020 – pictured to the left displaying battery voltage) and connected the power line from the inverter to our house wiring. In the disconnect box outside on the pole, I pulled the house wires loose and wrapped their ends with electrical tape.

The wire from the inverter (Exeltec XP1100) comes through the kitchen floor behind the electric stove (which is unplugged). I connected the neutral wire to the neutral in the outlet and the ground to the ground. Then, based upon a suggestion from Ramiah, I connected both existing hot wires in the outlet and the inverter hot wire to the same terminal. Ramiah suggestion was that I could just flip the breaker for the stove in the box. I was going to reroute the wires to the mains at the top. His suggestion helped clarify how unnecessary and complicated that was going to be. With the 240 volt 50 amp breaker the power would already be connected to both poles inside the box. So, I took his suggestion, and then flipped the switch.

Things are working well. The refrigerator came on right away and ran for about 5 minutes (see my post about our energy efficient refrigerator). The lights work (they’re not on now – it’s not dark enough). The computer works. In fact, at this moment, the power coming from the panels is enough to power the laptop I’m working on (it’s 3:36pm Central Time). Very cool!

We’re all excited!

The batteries are charged & I didn’t even know it

I’ve been keeping an eye on our solar electric system the last few days in order to watch how it’s performing. It’s been overcast every day it seems, and we even had some snow. However, the panels have been outputting power every day for about 9 hours a day. I was looking forward to seeing what kind of numbers we would get on a sunny day.

Today the sun actually shown through. However, I was disappointed and concerned to see an input value of only about 150 watts. Naturally, I wondered what was going on. I noticed that when I turned the photovoltaic array back on after momentarily disconnecting it via the circuit breaker that the power input would peak around 1,000 watts and then rapidly decrease.

For the previous days, I had noticed that the peak power input seemed to occur quite early and was much higher than the average input during the day. It seemed like something was bleeding off the power. So, I started checking my wiring on the panels. Interestingly, the input power was the same whether I had all panels connected or only some. I should mention that the source of my readings is the display on the Xantrex XW60 charge contollor.

Maybe I’m a bit slow, but I began to wonder if maybe the explanation had something to do with the solar charge controller. I couldn’t find anything in the manual, though. So, I called the technical assistance number and spoke with a representative, explaining what I was experiencing. She told me that the charge controller was adjusting the input because my batteries were fully charged or nearly fully charged.

I liked this answer, but it surprised me. I was sure that the batteries were a bit low based upon my voltage readings on them. I guess I was wrong. We’ve not connected the system to our house yet; I wanted it to fully charge the batteries first. Since it appeared that they were fully charged already and we had good sun today, I told the charge controller to equalize the batteries. This means that it purposefully charged them at a high voltage in order to mix the battery acid inside the cells. The reason for doing this was so that I could take specific gravity readings for each cell to use as a baseline for determining battery health in the future.

So, the batteries have been equalized. During the equalize cycle, the input was around 350 watts. When the cycle ended, I watched the input drop to zero watts. Confirmation that the charge controller was indeed adjusting/limiting the input. Very cool.

Only, I really have no way of knowing what kind of realistic input I can expect on cloudy days, now. What I’ve observed the last few days has been the charge controller adjusting the input to float charge the batteries. I guess it will be at least as much as we’ve seen so far, maybe more. Over 3.5 cloudy days, we registered 1.5 Kilowatt hours. Today only added half a kilowatt even with good sunshine and an equalize cycle. The possibilities are looking good, actually.

I’m going to take my specific gravity readings tonight. Then, tomorrow, I hope to complete the wiring so that we can flip the switch and be off the grid by tomorrow night.

We’re harvesting electricity from the sun

Although it’s been cloudy here, I’ve been watching the solar charge controller for evidence that we’re getting power from the panels. I thought there should be some power even with a

few clouds, but there was nothing. Nada. Zip.

I’ve been concerned that something was wrong,

that maybe I wired things incorrectly when tying the panels together, although I was careful when connecting them.

 
This afternoon, the sun actually peaked through the clouds. Still, no power. Hmm. I have a separate panel I want to install on the barn.

So, I put the multitester on it to see if it really was too cloudy.

It was putting out over 20 volts when I pointed it toward the sun.

We definitely ought to be getting power from the array on the roof.

I climbed up on the roof to check the wiring on the panels. I disconnected on string and put the tester on it – over 90 volts. They were working. So, I came back down and opened the combiner box. I pulled the wires from the panels loose and tested them in pairs to be sure that each of the three strings was working properly. They were.

I decided to check the continuity between posts on the bus bars inside the combiner box. That’s when I discovered the problem. They aren’t really bus bar. Each terminal is only connected to the one on the opposite side; they aren’t all connected together. So, my strings of solar panels were not connected together and not connected to the charge controller.

Once I redid the connections inside the combiner box, the solar charge controller began to register power coming in and to charge the batteries. There isn’t a great deal of power at this point. I think I should be seeing more, but it’s hard to tell. It’s still partly cloudy, not direct sun. I’ll keep an eye on it. If it continues to register lower wattage than I believe it should, I’ll check a couple of things to see if it makes a difference.

Anyway, it’s exciting to have power from the sun flowing in to the batteries for the first time.

Solar power: we’re getting closer

Most of the snow melted off the porch roof yesterday. So, today, once I got a few things done inside the house, I worked on installing the rest of the solar panels. This job went quite well and didn’t take too long. Before lunch I started wiring them together. I finished after lunch.

There are 15 panels in all. There are three sets of five panels which are each wired in series. That means they are connected positive to negative. This multiplies the voltage while the current stays the same. So, once five panels with a voltage of 17.4 volts each and an amp rating of 5.75 amps are wired in series, the voltage is 87 volts and the amperage is 5.75 amps.

Each of these three five-panel strings is then wired in parallel – connected positive to positive and negative to negative. Wiring in parallel multiplies the current while the voltage stays the same. So, three strings of 87 volts and 5.75 amps wired together in parallel yields 87 volts with 17.25 amps.

There are of course variations in the voltage and amps coming off of the panels depending on different factors like how direct the sun light is and the temperature of the panels. Increasing the voltage by wiring in series allows smaller gauge wire to be used to bring the power from the panels to the solar charge controller since the wire gauge required is based upon the amperage and the length of the wire.

The solar charge controller I purchased will take the 87 volts (with variations) and convert it to the appropriate voltage for charging my battery bank. The battery bank is nominally 24 volts, but it will be charged closer to 29 volts. The controller is rated to handle up to 150 volts, but I’m happy with 87.

The three strings of series-wired panels are combined in a combiner box. The negative leads are attached to one bus bar, and the positive leads are attached to another bus bar. This combines the positives and the negatives from the panels allowing only one wire for postive and one for negative to be sent into the house to the charge controller.

After installing and wiring the panels, I hooked up the negative and positive battery cables which lead to the disconnect box and from there to the other components of the system. I had them disconnected so that nothing would accidentally become powered inside before I wanted it to. After connecting them, I flipped the circuit breaker for the charge controller, and it woke up ready to be commissioned. Commissioning just meant I needed to verify the battery bank information for the controller.

It was late enough in the afternoon that the sun wasn’t shining directly enough on the panels for them to be producing power. So, I wasn’t able to determine for sure that everything is operational as it should be. I believe I wired them correctly, but I’ve made mistakes on other things before. Hopefully, we’ll have some sunlight tomorrow so that I can verify that things are working correctly and let the sun charge the batteries completely.

There are six tasks left to do before we flip the switch and go off the grid:

1.  Run the 12-2 wire from the inverter through the floor into the kitchen.
2.  Connect the wire from the inverter to the existing wiring in the outlet for the electric stove.
3.  Disconnect the mains from the AC circuit breaker box in our home.
4.  Connect the wire leading to the electric stove outlet to as the mains.
5.  Run the wires and connect the Bogart Engineering Trimetric 2020 battery monitor.
6.  Flip the switch to turn on the inverter.

At that point, we’ll be off the grid and on solar power. Don’t worry, I’ll disconnect the power from the utility company outside at the disconnect box before doing the wiring in the house. I have no desire to let electricity course through my body.

A good day

The cheese arrived today! It’s already been eaten. I remembered to take a picture of the second half of it. Let me tell you,

it was some good cheese! Wow! We all enjoyed it a lot. The children made sure they told me more than once that I should be sure to enter every cheese giveaway that mmpaints has. With cheese this good, they don’t have to tell me. I think we’re going to have to give cheese-making another go. We haven’t made any for a while, and it was never this good. Time to learn a bit more and develop a new skill.

Today’s weather was nice: in the lower 40s with sunshine. We’re under a winter storm warning beginning at 6:00 tomorrow morning and continuing until Saturday afternoon. The forecast says 5 to 9 inches of snow is expected here. We haven’t had that much at once in the whole time we’ve lived here. The children are looking forward to it.

Since the weather was nice, I worked on the water heater installation again. I took the heater out and redid the plumbing. My hunch appears to be correct: Teflon tape doesn’t work well on metal plumbing components. The threads cut the tape and push it mostly out of the way. I put some joint compound on the threads, and there were no more leaks. I cut the CPVC pipe and put in a new coupling. I let it sit for a few hours to make sure the glue was thoroughly dried before turning the water back on. No leaks there either.

So, I put the water heater back in the closet, hooked up the water lines, and routed the vent pipe through the wall. I’ll check it again tomorrow, but I think it will be fine now. This particular water heater connects to a 20 pound propane cylinder, the kind commonly used with LP grills. It can heat the water hot enough to scald you. I’ve got the adjustment for the flame turned down so that the heat in the shower is just about right. If it’s too hot, you just need to open the hot water side a little more. I think it will work out fine for us since our only hot water from it will be for taking showers.

While I was testing the water heater, our cat came home. Now, this may not sound like a big deal, but it was. He was missing for two full days. This is very unlike him; he likes to eat too well to miss a meal. We figured he either got himself stuck someplace (he somehow got under the floor in Dad’s barn earlier in the week) or something got him. We were quite concerned (I hadn’t realized how fond I am of that cat). Thankfully, this afternoon he came walking up the hill to the house. We don’t know where he’d been, but he was quite thirsty and hungry and glad to see us.

Later this afternoon it was too early to do chores and I didn’t want to waste the time and nice weather. So, I decided to install some more solar panels. I figured there was enough time to get two of them put on. Well, the installation went well enough that I was able to bolt four of them on. So, one frame is complete. Six more panels to go on the other frame. I’ll tackle that next week after the snow is melted.

My dad voiced a concern about the panels acting like sails and catching the wind up there. The roof on our mobile home is basically flat, and the pitch on the back porch roof is very shallow. So, the panels stick up in the air a ways. I do believe that if they blow off, they’re taking the porch roof with them. However, I think I’ll go ahead and put some guy wires on the top corners down to the other side of the house in order to provide a little extra insurance against strong winds.

The first solar panels are installed

Why is it that doing any plumbing seems to result in a leak somewhere? On Monday I got everything ready to change out our water heater. This involved taking out the 30-gallon electric water heater and putting in our new on-demand heater. The new one is one that is supposed to be hooked up outside, but where I’m installing it there’s no problem venting it to the outside. That was part of having everything ready – have the vent pipe to go in.

Well, I successfully took out the old one and put in the new one. Only thing was that there were some leaks. Nothing major, just some drips. Still, it worked fine. I could take care of the leaks on Tuesday. And, I endeavored to do so, changing the supply lines from those semi-rigid 3/4 inch regular hot water heater things to some flexible hoses with 1/2” connectors on each end. I also put in a shut off on the incoming line, something that should have been added years ago. Again, the installation went well, but there are a couple of drips.

The hot water works fine, but I have to redo some of the connections. On the metal pipe pieces, I used Teflon tape on the threads. I think I should have used joint compound. In fact, I will. The threads seem to cut the tape and render it practically useless which allows water to seep out around the threads. I replaced a section of 1/2” CPVC and it leaks around the coupling I put in to tie it to the existing line. So, I have to cut it and redo. Hopefully, I can get it all taken care of tomorrow since there were other things to do today. 

A good friend came over with his family today to help me with solar panel installation. It was a nice day for it. I even had to take off my jacket for a while. We worked and accomplished a lot while our children played here and there (they get along great) and the mommas talked and enjoyed themselves inside.

We secured the frames to the porch roof first. We had to make the 2x4 rails the feet of the frames attach to and pivot upon. This wasn’t difficult. These rails are securely attached to the 2x4 purlins of the porch roof with lag screws. Once we got the frames installed, I did some calculations for drilling holes for the adjustable legs. The frames are adjustable for the different seasons to maximize the amount of energy harvested. In this area, we are at 37 degrees latitude, meaning that 37 degrees is the fixed mounting angle. They can be adjusted 15 degrees either way to face the sun at the winter and summer solstices. The calculations I did (using an online resource) was to determine where to drill the holes for the adjustment settings.

Once the frames were installed, we started installing the solar panels. We got the five 50 watt panels on but not the 100 watt panels (ten of them). We had to drill holes that matched the frames on the panels. I already had holes drilled, but they didn’t match. Their placement was based upon the measurements from the website where I ordered the panels and an assumption that since they are supposed to be half the size of the 100 watt panels the mounting holes would correspond to the larger panels. Not so.

That didn’t take long, though, but by the time we had the fifth panel attached, it was time to put tools away and wrap things up. You’ll notice from the photos that one of these five panels is different than the others. I’m not happy about this, but I think it will work fine. They were all five supposed to be the same, but for some reason a different 50 watt panel was substituted for one of them. The specs on it are close enough to the other panels that there shouldn’t be any problem.

Anyway, it was a pretty good day. We’re getting closer to actually being off the grid.

Solar power: more installation

Well, I changed what I installed previously. I was going to have components on two walls, but as I looked at it and figured things, I decided it would work better to put it all on one wall. So, I moved the two components I put up last week and added some more.

Last week I bought some wire and other supplies from Richardson Electrical and Plumbing Supply in Glasgow, Kentucky. There were a couple more items I needed that I bought at LS Supply, and there are a couple more I need to get. Even when I figure ahead of time, it always seems that I forget or overlook a few things.

I set the disconnect box and charge controller first. Then, I mounted the inverter. The directions for it said that the preferred method was to mount it fan down. That also works best for running conduit straight from the disconnect box to the inverter. I had some heavy gauge cables I was going to use for the previous 3,000 watt inverter (which I just sold on Ebay for about $40 more than I paid, including shipping). These were too big for the new inverter. I was able to use 6 gauge wire, according to the Exeltech specifications.

I am still waiting to receive the Iota DLS 27-40 charger that I ordered. It will mount to the left of the disconnect box. I’ll run 6 gauge wires from it into the box and connect them to where the positive and negative battery cables are connected.

I’m endeavoring to keep the wires neat inside the box. I’ve routed them carefully and zip-tied them together. Since the 2-inch conduit for the battery cables isn’t connected to the battery box, I was able to route the wires for the battery meter out through it. I also ran the wire for the battery temperature sensor through the disconnect box and out the 2-inch conduit on the bottom. This is preferable to running it outside the box.

One of the options I’m building into the system is a panel for 12 volt applications. I don’t know what I’ll use it for yet, but I want the option. Since the battery bank is 24 volt, I have a step-down converter that will output 12 volts to a Square-D QO breaker box (the QO line is rated for AC and DC). I’ll be able to wire off of the breakers in this box to outlets I can install in the house to run 12-volt fans, appliances, or lights as desired.

I rewired the battery bank. Previously, I wired it into two banks of six batteries each at 12 volts in order to put a 12-volt charger on the batteries. It’s now wired to be 24 volts. I temporarily connected it to the box to check the inverter. It worked!

I’m going to run wires out to the combiner box I made, which I’ll mount just outside the wall where these components are mounted. Then, once I mount the panels on the roof, I’ll just have to wire them into the combiner box for the batteries to be charged by the sun.

From the inverter, I still have to run a wire to hook into the AC panel in the house. This will be a short section that will go under the storage room where the components are and up through the floor into the kitchen behind where the electric stove is sitting. In a junction box, I’ll tie the lines from the inverter to the wires for powering the electric stove. In the AC breaker box, I’ll disconnect the main lines coming in from the power company (the power will be disconnected outside at the disconnect breaker during all of this) and attach the wires that were previously for the electric stove. We won’t have 200 amp service, but it will be sufficient to run our refrigerator, lights, computer, sewing machine, washer, and other loads.

Before I get the solar up and going, I think I ought to install the propane on-demand water heater I have still in the box. I don’t like cold showers, and our system certainly won’t power an electric water heater.

Solar power: the first components installed

Last week I received a few more of the components for our solar power system. There are only two more components I have yet to receive. They’ve been ordered and should arrive soon. I’ve made one change in the plans: we’re not going to use two inverters. I already purchased a 3,000 watt inverter off of Ebay and was going to buy a 600 watt inverter also. Well, somehow my order for the 600 watt Samlex inverter got ‘misplaced’ during the holidays. That was actually a good thing because I had pretty much decided not to get it. So, I cancelled the order.

I realized that I do not have a need for a 3,000 watt inverter. There won’t be enough times that I need enough power from the system to justify having an inverter of that size. So, I’ve listed it on Ebay to sell it, hopefully getting my money back out of it. I also had decided that I wanted a different Samlex inverter/charger. This unit would provide AC power and allow charging of the battery bank from a generator during extended periods of cloudy weather. It was in favor of this unit that I cancelled the order for the 600 watt inverter. Then, I found out that the inverter/charger I wanted was no longer available. Samlex discontinued that model because they were coming out with a new one sometime this spring or summer.

This situation prompted me to consider other choices. I was interested in the Xantrex Trace series of inverter/chargers. I really like their power saving feature where the inverter can be put into sleep mode, during which it consumes very little power while sending out a pulse every few seconds to check for any loads. If there’s a load, it powers up. The only thing I wasn’t sure about was that it is a modified sine wave inverter.

There are many inverters out there which are modified sine wave, and people run all kinds of things with them. There are a few things that can have problems with modified sine wave. For instance, certain electronic devices don’t like it and some motors can run hotter and less efficiently with them. As I considered the pros and cons (the pros mainly being price), I finally decided that we would be best served with a relatively small true sine wave inverter.

At this point, I was ready to order a 1,000 or 1,500 watt Samlex inverter which would provide all the AC power we would need 99% of the time. But, I didn’t like their no-load power consumption, and I wasn’t completely sure about the quality and longevity of an ‘inexpensive’ inverter.

Anyway, I ended up ordering an Exeltech XP1100 true sine wave inverter with a power saving option. These are American made and of good quality. I’m pretty confident that it will do all we want and need very reliably. It did cost a bit more than a cheaper model, but if it lasts longer it will be worth it. I also ordered a battery charger since the Exeltech is only an inverter. Iota has a nice model (DLS 27-40) which I’d been considering. So, since it may well be necessary at times, I ordered it. These are the two components I’m waiting on.

This afternoon I went to a local electrical supply store to buy some wire and other supplies I need for installing everything. I started the installation by getting the knockouts ready on the disconnect box. Then, I attached it and the solar charge controller to the wall. When other projects allow, I’ll start wiring the inside components and will then mount the solar panels and connect them. At that time, we’ll be just about ready to throw the switch on our alternative energy system.

In the first photo, you can see the first two components on the wall. I’m installing it in the corner of the small storage room I built on to our mobile home a few years ago. The battery box is on the floor below the solar charge controller and disconnect box.

The photo at the left is a closer view with the cover off the box. The battery cables will enter from the bottom. The conduit to the left will route the wires to the inverter. The Xantrex XW-MPPT60-150 solar charge controller is on top. This controller has some very nice features and should help harvest as much energy as possible from our solar array.

Inside the disconnect box are breakers. These are for the PV array input, the solar charge controller output, and one for a separate DC only distribution box for any DC loads that we may wish to run in the future. There will be a larger breaker installed for the inverter in the empty slot above the other breakers. You can also see the shunt I installed inside the box. This will allow for accurate battery monitoring with the Trimetric 2020 battery monitor that I bought and will install.

I bought a weather tight junction box and two bus bars today. I installed the bus bars inside the junction box (photo at right) for attaching the positive and negative leads from the solar panels to. I didn’t want to use wire nuts. The negative leads will be on the bar to the left and the positive leads will attach to the bar on the right. The positive and negative wires going to the house will also attach to the bars. This will allow me to combine the three sets of panels I’ll have wired in series in one neat, clean box. I think it will work well.

I think we’ll end up with a very nice system. It’s cost more than I intended – it’s easy to spend a lot of money on solar power. We wouldn’t be putting this system together if it wasn’t for taking an early disbursement of my retirement money (I don’t believe it would be there by the time I reach retirement age if I left it along) to fund our house building. Lest you think we had a great sum of money to withdrawal, let me assure you that we didn’t. It ought to be enough to finish the house, including a solar power system, without extravagant spending. My conviction is that it is better to have that money in something tangible, like a house, than to leave it subject to unstable market forces.

Homemade solar panel mounting frames

We hadn’t planned on going off the grid while we live in our current home. As I said before, going off the grid was a future endeavor. Moving the time for doing so up, I still hesitated to install it for our mobile home because that would require it to be disassembled and moved to the new house later. However, we decided to go ahead now. So, I’ll be moving it whenever the house is finished.

As I considered how to set up and install a system, I had wanted to build a metal framework to mount the panels on. However, I decided later to build the framework out of wood for now and construct a metal framework later for the new house. I do want the panels to be adjustable on one axis to face the sun more directly in the seasons rather than to be a fixed mount. They need to be laid back during summer and raised closer to vertical in the winter – a thirty degree swing of movement.

For the current framework, I’m using 2x4s and 1x4s. I designed and have built two frames. The first one (photo at the left) will hold six 100 watt panels, and the second one (photo on the right) will hold four 100 watt panels and five 50 watt panels. The 50 watt panels are half the size of the 100 watt panels and will be installed on the left of the framework (one sticks out to the left of the others).

Both panel mounting frames will be attached securely to the roof of our back porch which faces south. To adjust the tilt of the panels, I will have to physically go up on the roof. I plan on having five set positions for them to adjust the tilt every month and a half. It would be nice to have a mechanical means of adjusting them so that I didn’t have to climb up on the roof and do it manually, but I’m still working on a design for that. Hopefully, I’ll incorporate it into the more permanent mounting frame on the new house. As it is, the porch on this home is not very high.

In the photo to the right, you can see the part of the framework that allows the tilt to be adjusted. There will be rails on the roof on which the feet will run with set points for the different angles desired. When in position, these feet will be bolted to the rails. The feet on the front, bottom of the frameworks will pivot on a bolt through another rail bolted securely to the porch roof. To change the angle of the panels, I will have to take out the securing bolts on the rear feet, lift the frame a little, slide the adjusting feet to the desired position, and reinsert the bolts through the feet.

Off-grid solar power system specifics (technical details)

The basic components of our solar electric system are:

• 1250 watts of solar panels (10 100-watt panels and 5 50-watt panels)
• 12 6-volt 225 amp hour batteries
• 60 amp MPPT solar charge controller (Xantrex XW-60)
• 3,000 watt true sine wave inverter (Aims Power)
• 600 watt true sine wave inverter (Samlex)

I bought the panels and batteries from Sun Electronics in Florida. The panels are Sun-100 and Sun-50, panels that the company has assembled for them from other panel manufacturer’s parts. These are not top of the line panels, but I didn’t pay the $3 to $5 per watt price of top of the line panels. I bought these because they were on sale ($1.74 per watt – they now have other sizes on sale for the same price), fit within my budget, and their specifications were appropriate for my application. They look fine and test fine on my digital multi-meter. Maybe they won’t last as long as other name brand panels, but they seem like a good place to start.

The batteries are 6-volt golf cart batteries, a common deep-cycle lead acid battery for solar applications, especially new systems. They are relatively cheap and should provide several years of service if treated properly. One of the things I didn’t realize when I first ordered the panels and batteries is how the solar array needs to be sized to the battery bank. You can have too large of a battery bank for the number of panels which isn’t good for the batteries. I actually was on the bottom edge with my amount of PV (photovoltaic) watts with our original number of panels (10 100-watt). 

I ended up ordering more panels, 5 50-watt panels, after having received the first 10 100-watt panels for three reasons: they didn’t have any more of the 100 watt panels matching what I already received, I wanted to size the PV array more appropriately to our battery bank size, and it allows a little more available power generation for the system. As I mentioned in a previous post, conservation is the first three things you should do in setting up an off-grid system. In sizing your system, you need to be able to compute your reasonable and realistic electricity usage. This is where a Kill-A-Watt meter comes in very handy (as of 12/30/09, Newegg has it on sale for $19.99 with free shipping if you use promo code EMCMNPM27).

For our usage we’ve figured on the following daily consumption (rounding up each in order to over-figure rather than under-figure):

• 300 watts for refrigerator
• 300 watts for lights
• 300 watts for computer/tv/dvd player
• 200 watts for washing machine
• 100 - 300 watts for miscellaneous usage

That gives a total of 1.2 to 1.4 kilowatt hours per day. We can and probably will use less because these numbers are figured high on purpose based upon our current usage. There will be times when there is limited sun during a given week because of cloud cover, meaning there will be less electricity available for use. Extended periods of cloudy weather would probably require a generator or other power source to charge the batteries. If we weren’t trying to run a refrigerator, we could just live without electricity during such times until the sun returned to recharge the batteries. So, we’ll be getting a small generator as a backup to keep the batteries healthy – discharging batteries too low is greatly limits their lifetime.

We can figure the necessary battery size for our system based upon our general usage (let’s round it up to 1.5 Kwh). When figuring usage, watts for different voltages are equivalent, but amps are not. There’s a simple formula: volts time amps equals watts. That means at 120 volts (standard AC) 12.5 amps equals 1,500 watts (120 x 12.5 = 1,500). However, at 24 volts (the voltage of our battery bank), 1.5 kilowatts requires more amps: 24 volts times 62.5 amps equals 1,500 watts (24 x 62.5 = 1,500). If I made my calculations based upon amps, I’ be way off. When figuring battery usage, we need to be sure and use the right numbers.

So, our daily usage at 1.5 kilowatt hours requires 62.5 amp hours from the batteries. A standard three day reserve would require 187.5 amp hours. For battery health and life, it is best to not cycle it too deeply. I don’t want to use more than 20% of the battery’s capacity on a regular basis. Fifty percent is the maximum level of discharge, and I prefer not to discharge it that low. At 62.5 amp hours per day, the daily cycle of the battery will be about 10%. We could go 2.5 days without sun without going below 80% state of charge on the batteries. At 50%, we have about a 5 day reserve.

The thing that needs to be figured into all of this is the inefficiencies within the system. All of the components are not 100% efficient. For instance, it’s generally figured that batteries are only 80% efficient. At that rate, our usage figures out to just over 4 days reserve. These numbers give us a good estimate of the capabilities of our storage as it relates to usage. We’ll also have a battery monitor that will give us information regarding the battery’s state of charge and other pertinent information.

There are other inefficiencies in the system to be figured, too. One of those is the inverter. My numbers above haven’t considered the amount of power the inverter will consume just by being on. In fact, the reason we’ll have two inverters is because the smaller one will consume less power than the larger one while supplying the power we need in our home 90% of the time. I originally bought the larger one off of Ebay for about half price of new. Later, I realized that it would draw up to 576 watts per day (probably less, but, again, it’s better to figure on the upper end). The smaller 600 watt inverter will consume 250 or less watts per day.

Okay, you don’t have to do all of these computations in order to set up a system. For me they’re important in sizing our system. A lot of people start out small and build on to their system over time. This allows them to figure out what works as they build. This is a good way to learn. There are also a lot of online resources to help you learn about solar power systems. I’ve found some great information on the Northern Arizona Wind and Sun discussion forum. A little searching will reveal a lot more information if you have the time and desire.

A nice resource for figuring how much power you can expect to realize from a solar electric system is the site PVwatts. You can input location information and PV array specifics to figure how much electricity  you can realistically generate for usage. Their numbers are based upon statistics collected over 20 years. If you want to compute for an off-grid setup, put 0.52 in the “DC to AC Derate Factor” to account for the inefficiencies in the system. I know this sounds like a large amount to derate it, but it is recommended by those with experience in order to give you realistic figures to work with. This number accounts for panel, battery, and inverter efficiencies which are less than 100% each.

So, our system will have a 1,250 watt PV array feeding a 24-volt 675 amp hour battery bank connected to an inverter that will output clean AC power for our household use. We could have designed and put together a smaller system, but we had the opportunity to make it this size at this time. As I put this together (it’s still being put together), I worked with a self-imposed budget of $5,000 (money taken out of a 403b account budgeted for building our house – the solar power system is part of the house project). In some ways that was an ambitious number, but not completely unrealistic. Our total will actually come out to about $7,000, but the federal government offers a 30% tax credit for installing a system. After that credit (yes, I’ll take it), we will fit within our $5,000 budget (I had hoped to fit within it prior to the tax credit).

We figured as long as we were able to, we ought to make the system larger than smaller. Generally, usage ends up being greater rather than smaller. At our system’s size, during the shortest month (December) we can still realistically expect to generate enough power to consume 1.5 kilowatt hours a day (based upon PVwatts calculations). During the peak months (May, June, & July) while we have plenty of sunshine, we’ll be able to go hog wild and use up to 4 kilowatt hours a day! Ya’ll come over for the party!

Making a refrigerator out of a chest freezer

Over a year ago, I read about an individual living off the grid somewhere in Australia who converted a chest freezer into a refrigerator. His experience showed him that he could run it as a refrigerator on about 0.1 kilowatt a day. His results were affected by the type of chest freezer he bought for the purpose, one that is rated highly for its efficiency (I believe it has more insulation than regular models). Being a chest freezer with the lid on top, the cold air doesn’t “fall out” every time it’s opened, helping the compressor to need to work less to cool things back down.

The basic concept for converting a freezer into a refrigerator is quite simple. You have to override the compressor since the one in a freezer is meant to cool things on the inside down to near zero degrees (Fahrenheit). In the article I read, the individual included plans for building an external thermostat to override the freezer’s thermostat. That seemed a bit complicated, but I then found I could buy an external thermostat designed to do the same thing.

Northern Brewer has a couple different ones that they sell. Generally, these allow homebrewers to use a freezer to set the appropriate temperature for fermenting lager and to chill their kegs of beer. So, I purchased one of the models they sell (I actually have two of them now so that I can convert another freezer into a refrigerator if necessary).

The external thermostat is plugged into an electrical outlet, and the freezer is plugged into the thermostat. A temperature probe connected to the thermostat is placed inside the freezer, and the desired temperature is set on the thermostat. I set ours at 38 degrees. The unit has a 3.5 degree temperature differential. The set point on the thermostat is adjustable from 20 degrees to 80 degrees (Fahrenheit). When the internal temperature drops below the set point, the power to the freezer is disconnected, stopping the compressor. When it rises above the set point, the compressor is once again powered.

It works quite well. The temperature inside the freezer stays regulated at refrigerator temperature. We’ve set up a 14 cubic foot freezer as our refrigerator. There’s as much or more room for food storage inside than our previous 20+ cubic foot conventional refrigerator. Before switching to using it, I measured its power consumption over six days. During that time it averaged only 9 watts and hour. Our regular refrigerator used over 80 watts an hour.

There is no freezer in the refrigerator, of course. On solar power we will not have a freezer because of the amount of power required (both of our freezers average 55 watts an hour). So, we are adjusting to the limitation. However, the ability to have refrigeration even on solar is a definite blessing.

The main issue we’ve discovered with using a chest freezer as a refrigerator is water that condenses on the inside and then pools on the bottom. It’s a good idea to put some silicone caulk around the bottom edge of the walls to keep the water from starting rust there. I’ve read of others putting a small channel along the inside edge about a foot down from the top which directs the water to a single collection point or through the freezer drain.

Going off the grid

One of our goals is to disconnect from the power grid. Using electricity from the power companies is easy and convenient. It’s readily available here at our place and is relatively inexpensive. However, the generation of electricity for the electric grid has definite environmental, health, and economic impacts on different areas of the country. My consumption of grid-tied electricity affects other people whether I realize it or not.

We’ve talked about and considered having a solar electric system for our home. It’s been a goal reserved for the future, something to pursue when we could afford it several years down the road. Putting together and installing an off-grid solar electric system usually does not make economic sense unless you don’t have electric service readily available to your home, because the time required to recoup your costs can take up to 50 years. If you’re off the beaten path, it can cost you thousands of dollars for the utility company to stretch wires to your home. In that case, it makes economic sense to spend thousands of dollars to put in a solar electric system.

Recently, we’ve moved up the date for achieving our goal of going off grid. Part of our motivation has come from some friends of ours whose children have been affected by pollution from the use of coal. Rather than make a strictly economic decision about electricity, we’re making what we consider to be a moral choice in pursuing our goal at this time. It also fits within our efforts toward greater independence from “the system.”

We’ve been making preparations to go off grid during the last few years, of course, primarily through conservation of our use of electricity. We turn off lights when they aren’t needed. We disconnect the water heater at the circuit breaker during the day, turning it on 30 minutes or so before taking a shower and then turning it off afterwards (I’ll soon be installing an on-demand propane water heater to supply hot water for showers – the only thing we currently use it for). We’ve stopped using our electric cook stove, using our wood cook stove instead (we have another small wood cook stove that I’m going to set up on the back porch to use when it gets warmer this spring/summer).

In order to disconnect from the electric grid, I’ve done a lot of research recently and have ordered solar panels, batteries, a charge controller, inverter, cables, etc. – all of the things we’ll need (if I’ve figured correctly) to set up our own solar electric system. I’m in the process of installing the system right now.

I’m putting our system together and installing it myself. I’ve learned a lot in the last two months about what’s needed for an off-grid system and how to put it together. There’s a lot more I’m sure I don’t know, but hopefully there isn’t too much critical knowledge that I don’t have yet (or that I will be ignorant of before I’ve got it all set up and going). There are a lot of online resources available and a lot of reputable companies with great knowledge selling solar supplies. I am, of course, willing to share my little bit of knowledge with others, too.

This is a photo of the batteries in the battery box. Currently, they are wired in two 12-volt strings (three paralleled sets of two 6 volt batteries in series) in order to put a 12 volt charger on them until the panels are up and going. Once the panels are up, the battery bank will be 24 volt (three paralleled 4-battery series). I’ll post more photos and description of the installation later.

When it’s all said and done, we’ll have 1,250 watts of solar panels charging a 24 volt battery bank with 675 amp hours capacity. We’ll have 600 watt and 3,000 watt pure sine wave inverters (the larger one for only when needed, like for running any power tools for short duration). Our refrigerator, which I’ll post about later, is a 14 cubic foot chest freezer with an external thermostat that keeps the temperature at 38 degrees while using 10 watts per hour. We’ll be using less than 1.5 kilowatt hours per day during the winter months with the option to use more during the summer.

The first, second, and third things to do when setting up an off-grid system is to conserve, conserve, conserve. We bought a Kill-A-Watt meter a few months ago which allows us to measure the electrical usage of different appliances in order to gauge how much power we actually need. There are a lot of things which use a lot of power but really are not needed (incandescent light bulbs, for instance).

More to follow. . .