Saturday, October 07, 2006
Here are the main elements of the solar-electric system in my house:
- 84 Unisolar SHR-17 shingles (1428 watts), 12 series strings of 7 shingles each
- Outback MX60 maximum power point tracking charge controller
- Outback FX2548 2500 watt, 48 volt inverter
- 8 Rolls-Surrette S-530 deep-cycle solar batteries (530 AH)
Here's a photo of the power panels, inverter, and charge controller in the basement:
Links to the major equipment suppliers and other useful sources of information are on the left. Details about this project and how it was done are in the archives, also on the left.
Saturday, August 12, 2006
So what does it look like a year later? Since August 12, 2005, the charge controller has recorded 1726 kilowatt-hours of solar energy harvested, an average of 4.7 kwh per day. The maximum yield was on June 24, 2006: 10.5 kwh for the day. The minimum was zero, which happened four days last winter when snow covered the roof all day. Here is a chart showing the daily solar yield.
It should be recalled that on some days the charge controller went into float mode, meaning that the batteries were fully charged. More solar energy was available but I had no place to put it. We still haven't connected a dump load to make use of this extra energy, and the possibility of selling back to the grid looks like it will be too much trouble and expense for too little benefit (either to me or the planet).
Of course, there were many days, especially in the winter, when the solar energy was insufficient for my household needs. This chart show the average daily kwh's from solar (from the charge controller's log) and the grid (by reading my electric meter weekly):
The grid totals for July and August of this year are slightly higher because of the heat wave in late July/early August. While I don't use air conditioning, I had to run the dehumidifier almost non-stop during those two weeks to prevent mold, and I was running electric fans as well. The high temperatures also seemed to reduce the efficiency of the solar shingles, as expected. While many of those hot days had abundant sunshine, the roof never produced more than 8.7 kwh on any one day, even though I had plenty of demand for it. For comparison, there were days of similar length and sunshine in May that produced over 10 kwh. I was afraid that maybe one of my shingle strings had become disconnected, but I checked this with my voltmeter and found that all are still working properly.
While the financial savings so far are very minimal compared to the cost of the system, I have enjoyed being relatively blackout-proof--sometimes when I didn't even know it! I know I was able to watch a World Cup game when the grid power was out, and there were two other times when neighbors asked me if my power was out and I said I had no idea. We haven't had any lengthy blackouts like in 2003, yet, but I'm pretty well prepared if we do.
What's next? I'm currently looking into ways to use solar to heat my house. I have had the shrubs on my south wall removed, opening up lots of area for solar collectors. The simplest approach would be to install a solar air heater or two, but I'm considering something more elaborate, perhaps involving thermal storage. I'll post updates here as they happen.
Tuesday, April 25, 2006
In the News
There's also an article I wrote about my project in this month's local Sierra Club newsletter, but it's not available online.
Sunday, March 12, 2006
Late winter update
Here's a chart showing the average daily kilowatt-hours generated by my roof, by month.
Several things to note:
- The July and early August numbers were hampered bad batteries. My first set of batteries was unable to hold a charge, so the solar power had to be used as it was produced--additional sunshine was wasted (and not recorded by the charge controller).
- I do not have a "dump load" connected, and haven't since the system started operating. This means that once the batteries are fully charged and the sun is still shining, no more solar power is produced (basically, the charge controller opens the switch on the wires from the roof to protect the batteries from overcharging). Net metering should solve this problem.
- I have been experimenting with the HBX mode settings on the inverter. HBX allows the system to automatically switch to grid power when the batteries get low, and then back to solar once the batteries have recovered. The Outback inverter lets me define "low" and "recovered" in terms of voltages. If I set these too low, the batteries will discharge too much, shortening their lifespans. If I set them too high, the batteries charge too quickly and the additional solar power available goes to waste (as above). I adjusted the settings higher back in December, hoping to protect the batteries by keeping them in a nearly fully-charged condition most of the time. This also provides me with plenty of backup power in case of a blackout. In February, however, I was caught by surprise by the string of sunny days, and on many of those days I lost quick a bit of potential solar power. I have now lowered the voltage settings to close to where I had them in the summer. Again, net metering should resolve this concern. I'll be able to maintain the batteries at close to full charge most of the time, prolonging their lives and staying prepared for a blackout.
- My 1988-model natural gas furnace was not working well this winter, and got much worse in February. It had a high-wattage fan motor (500-600 watts). In mid-February I replaced it with a new Carrier high-efficiency two-stage furnace. It has a DC fan motor which only uses 80 watts in the low stage (although it runs a higher percentage of the time, so the savings aren't quite that dramatic). In any case, the furnace situation makes it difficult to make much sense out of my energy usage this winter. In December, I had an inefficient old furnace using lots of watts in the cold weather. January was warmer, and I spent the last eleven days in Mexico. When I got back, the furnace was hardly working at all, so I was using electric space heaters a lot (big electricity hogs). Finally, since mid-February I've been enjoying my new furnace. It should save substantially on both electricity and gas use compared to previous winters.
And in the lemonade-out-of-lemons category: Last year, there were only three trees which could cast shadows on my solar shingles. This would only happen in the early morning or the dead of winter, but still they were cutting into my solar power. For better or worse (actually both), all three trees were emerald ashes, and had been infected by the emerald ash borer. As you can see from this picture from April 2005, the trees were already dead:
As a safety measure, the city came through the neighborhood in December and cut down all the ash trees. So now, it's all sun, all the time.
And yes, that second photo was taken today, March 12, 2006, technically still winter in Michigan. I was wearing shorts and a T-shirt when I took it. Sixty-three degrees! (It feels warmer than that.)
Friday, March 10, 2006
Inverter for sale?--grid-tie possibilities
I looked up the details of the Michigan net metering agreement, which can be found on page 237 of a lengthy PDF file from DTE (Standard Rider No. 16). I also called Outback to see if the new inverters are interchangeable with my current FX2548. They said that they were; furthermore, they can upgrade my FX2548 in about ten days for $350. A better option, if I can find a buyer, would be to buy one of the new inverters and sell my old one. The current price for an FX2348 is $1493, while the grid-tie-capable version is only a few dollars more. So, if I can sell my current inverter for $1300 or so, both the buyer and I can save a couple hundred bucks.
So--any readers out there planning an off-grid system who might need an almost new 48V, 2500W inverter? If you're nearby, stop over and I'll throw in a bunch of wire and other goodies you may need for your project!
(Note: I'm not sure if the FX2348 is the same inverter as I have. Mine was listed as an FX2548--either they modified the design to a slightly lower power output, or they determined that the 2500W rated output was a bit optimistic. I don't think I've ever pushed mine to anything close to 2500W.)
Monday, January 02, 2006
2005 solar summary
The first big snow was on Thanksgiving. I finally ran out and bought a roof rake, which I used for the first time that day. I have to use a ladder to be able to reach the top-most shingles. Raking the snow off of the solar shingles takes about 15 minutes, and I did it about five times in December. There were three days in December when the roof remained covered with snow all day--those were the only days without any solar power generated.
Here's the daily kw-h outputs from the time we first turned the system on through the end of the year:
The data come from the MX-60 charge controller. Some of the numbers for the summer month are below the actual solar power available, since on several days the batteries were fully charged while the sun continued to shine, and the system remained in float mode, unable to use most of the power available. This coming summer I intend to have the dehumidifier hooked up as a dump load, which should mean that I'll be using almost all of the available sunshine. In the long run, replacing my inverter with a grid-tie model is still an option, especially if grid prices skyrocket.
Back in August I haphazardly began reading my electrical meter to see how much grid power I'm using (the monthly power bills, which frequently use estimated readings, don't provide nearly enough detail to track my power use). For the last couple of months I have been more organized, checking the meter every Saturday. The chart below shows my weekly power use, both solar and grid. Until the start of November, the grid numbers are approximate. The dates are the Saturdays that I took the meter readings, and the totals are for the week ending that day. (I couldn't figure out how to get Excel to make the bars wider.) I should also note that the solar numbers are from the charge controller, and therefore ignore the inefficiencies of the charge controller, batteries, or inverter. Unfortunately, the FX2548 inverter does not track its performance the way the charge controller does.
Hopefully December will go down as the worst month of my first solar year--January and February will certainly be the biggest challengers. I'll continue to track the performance and post summaries here.
Saturday, November 19, 2005
Finally, they read my meter
We had two very dark, rainy days this week, which were the lowest kwh my system has had so far-about 0.4 kwh each day. Today was sunny, so I got 4.1 kwh. Nothing like the 9+ I was getting in August, but still not bad for a short day with the sun at low angles.
Here's a chart showing about 4.5 months of solar production:
Friday, October 14, 2005
Cal Poly San Luis Obispo:
Concordia University (Montreal):
University of Colorado:
Designed to be produced as manufactured housing, with a target cost between $50,000 and $100,000.
Florida International University:
Universidad Politecnica de Madrid:
University of Maryland:
University of Massachusetts, Dartmouth:
House will be donated to Habitat for Humanity after competition.
University of Michigan:
University of Missouri, Rolla:
New York Institute of Technology:
Uses a hydrogen fuel cell instead of batteries.
Universidad de Puerto Rico:
Rhode Island School of Design:
University of Texas:
Washington State University:
There's a lot more about these houses here, including links to the web sites for each house/project. I've been hoping that the U of M would win this, but the competition looks fierce (and I'm afraid they finish dead last in the sketches provided for the overview, although Pittsburgh's is pretty lame as well--photos of models always look tacky). From a purely aesthetic viewpoint, I like the Concordia, Cornell, Madrid, Massachusetts, Missouri-Rolla and Puerto Rico designs best. While the need to transport the houses is a positive in terms of possible conversion to mass production, it does have the downside that it prevents any use of earth sheltering. A few of the houses are intended to be hooked up to ground-source heat pumps once they reach their permanent locations.
Saturday, October 08, 2005
Solar Tour October 8
Monday, September 26, 2005
There will be other tours around Michigan on October 1 and October 8.
Simplified battery watering
Special caps replace the original battery caps. Each cap has a float which cuts off the flow of water when the cell is full. The manifold distributes the water to the three cells in each battery.
The battery manifolds are connected together with rubber tubing. Each manifold has three connectors. The unused connectors are capped off.
A hand pump is connected to the manifolds with a simple connector, and the other end goes in the bottle of distilled water. When the pumping gets hard, the batteries are full.
Six weeks, six kilowatt-hours
September 25, six weeks later:
Monday, September 12, 2005
Click here for larger version.
Tuesday, September 06, 2005
Friday, September 02, 2005
Winverter is available from RightHand Engineering for Outback and Xantrex equipment.
Thursday, September 01, 2005
Two months of solar
- The first week or so I didn't have a functioning "Mate" controller, so I couldn't get the inverter to run in HBX mode, which allows for automatic switching to the grid when the battery voltage drops below a certain point. Since I was using the crummy old batteries at this point, I was restricted largely to using solar only when I was home and the sun was shining. That's why there are four approx. 1 kwh days in early July.
- The high daily value for the two months was 10.2 kwh. This was the result of not only the extended high-angle sunshine available in early July, but also because the shingles put out more than their rated 17 watts each when they are new.
- The new batteries were connected on August 12.
- This shouldn't be taken as a direct measure of how much solar power was available each day. If the batteries were fully charged and not many loads were running, the amperage will drop to a trickle or stop altogether, even in full sunlight. Once we figure out the dump load, there should be less wasted power.
- The average daily power before 8/12 was 5.47 kwh; after 8/12 it was 6.65 kwh. This occurred even though the days are getting shorter and the shingles newness is wearing off. (I think we've had more cloudy and rainy days, too.) This shows that I needed adequate battery capacity to take fuller advantage of the solar power available. With the old batteries, I was generally unable to use any solar power at night--the batteries discharged quickly, and that was it. With the new batteries, I can power the house all evening and through the night, leaving the batteries ready to receive more charge the next day.
Tuesday, August 30, 2005
Monday, August 29, 2005
Solar air heating?
ClearDome Solar offers several products to convert sun power efficiently into home heating. Check out their external forced-air heaters, solar heating drapes and radiant panels at their Amazon sales page. Let me know if you've heard or read anything about these systems.
Friday, August 26, 2005
Come check it out!
Wednesday, August 24, 2005
Sunday, August 21, 2005
94% Grid Free!
Sunday, August 21, 2005, 2:30 PM:
So my electric meter went from 01347 to 01350 kilowatt-hours in one week--3 kwh. Typically, I would use about 50 kwh in a week. The charge controller's log shows that 47 kwh were generated by the solar shingles. So, for the past week, I got 47/50 of my electricity from the sun: 94%.
Unfortunately, the Mate controller doesn't provide an easy way to track the actual AC out energy used, which would more accurately compare to the electric meter. It does provide a crude graphical indication of instantaneous AC out, but it doesn't integrate it over time like the charge controller does for solar power. Rick and I are looking into various ways to track the system performance.
We still don't have the dump load figured out, so I've been controlling the dehumidifier manually, trying to get it to run at the right times so it won't bring the battery voltage too low. The 3 kwh on the meter are a measure of the degree to which I failed.
It's a very nice, sun-shiny day today. I've been tracking the solar kwh's throughout the day--I'm hoping for a new record!
Tuesday, August 16, 2005
Here's what it looked like Monday about 5 pm, and still looks like (3:30 pm Tuesday):
So, I used just under 1 kwh of grid power on Monday, and none at all between 5 pm Monday and 3:30 Tuesday. Getting the dump load setup configured should allow me to run the dehumidifier as much as possible without accidentally drawing grid power.
Monday, August 15, 2005
The Alternative Energy Store gave me a below-listed-price deal on the first 80 shingles, but dragged their feet on giving me an estimate on a pre-assembled Outback Power Panel (I ended up buying all of the components separately). Affordable Solar had the lowest prices, but they messed up on two orders, putting the wrong stuff in the boxes.
Sunday, August 14, 2005
Dump load versus grid tie
Michigan didn't pass a net-metering bill until a couple of months ago, after I had ordered my equipment. I don't know how it will be implemented by DTE, or when, and the inverter I have is not designed to sell to the grid. If the law had been in place when I started, I might have gone with a different inverter (Outback actually now makes a battery/grid-tie inverter similar to mine). But I don't think there will be too many times when I have so much extra power that I can't benefit from it--make the basement a little drier in the summer, the house a little warmer in the winter.
For now I'm using the grid as backup to my solar. After I've operated the system for a year or so, I may find that I can make it without the grid at all--in which case I can save the basic monthly connection fee.
The most cost-effective solar electric installations are the grid-tie ones without batteries. Basically all you need are panels and a grid-tie inverter. But you get no blackout protection, since the utilities require that your system shut down when the power is out (to protect line workers, I think).
I based a lot of my decisions based on what I really wanted, not on the economics. The most cost-effective thing to do would have been to take the simple conservation measures (insulation, compact fluorescent bulbs, Energy Star appliances, switching off phantom loads) and staying with the grid. However, if the energy crisis kicks in in earnest in the next couple of years, I may still come out ahead, having bought my solar equipment at what may in retrospect look like low prices, and not paying sky-high electric bills. If not, I've still got a cool blackout-proof self-powered house for about the cost of a new car.
I think that reads 01347. In any case, I'll try to check it each day or two and see if I've used any grid power. The system is currently configured (at least I hope I did it right!) to run off of the batteries until they get down to 46.4 volts, which is approximately 50% charge for the eight nominally 6-volt batteries in series, according to the manufacturer. At that point, the inverter will automatically switch to grid power until the battery charge has recovered somewhat. Given what I've seen from this weekend, it shouldn't have to switch to grid power any time soon!
Saturday, August 13, 2005
Almost Finished! And I mean it this time!!!
He brought it over Thursday evening, and we finished hooking it up last night (Friday). Quarter-inch plywood, reinforced where necessary, coated on the inside with an acid-resistant epoxy, and on the outside with white semi-gloss latex paint. The top slants towards the back to guide hydrogen gas to the vent at the back. Properly venting the hydrogen generated when the batteries are heavily charged (like during equalization) is the primary reason for a battery box. Protecting against accidental contact with battery acid or dropping something metal across battery terminals are other reasons why a battery box is needed. If I had been able to stay with the sealed batteries, a full box probably wouldn't have been needed, but a protective cover would have (ultimately up to the electrical inspector, who I'll be ready to call in another week or two, hopefully).
Rick put some nifty battery dividers in the bottom of the box:
The batteries in the box.
The exhaust vent can be seen in the back left of the box, and the holes where the cables come through in the upper right of the back:
At the bottom of the picture below is the fresh air intake for ventilating the battery box. A small 12-volt fan is in the fitting where the tubing enters the box. The fan is controlled by the inverter, and runs when the batteries are overcharged (60 volts on the nominal 48-volt system). This should only happen during battery equalization, a process run every few months to keep the batteries working properly. For normal operation, gravity should suffice to ventilate the box of any hydrogen generated.
The exhaust vent from the box:
Of course, the vents have to go outside, so Rick drilled a couple of holes in the back of my house (this was about 10:30 pm last night):
This is what it looks like from the inside:
By the light of day, we see the vents in place. Rick intends to add a downward elbow on the intake (left) to keep rain out. A small ventcover is already in place. For the exhaust, he thought it was not a good idea to use a down elbow, since that could cause hydrogen to be trapped. Instead, he just cut the end at an angle. He'll add some window screen to keep the critters out.
All of the connections to the box can be seen in the photo below. at the bottom, you see the air intake, the wires powering the 12-volt intake fan. The big black cables are the main battery cables, connecting the batteries to the Outback PS2DC box, which connects them (through breakers) to both the solar array and the inverter. The small black wires connect to a remote temperature sensor attached to one of the batteries inside the box. Maximum charging voltage varies with temperature, so the temperature sensor tells the rest of the system how hot (or cold) the batteries are. At the top, the exhaust pipe can be seen coming out of the back of the box and turning up behind the intake pipe.
With everything in place and connected, we can close the lid and let the batteries go to work!
We started running on them last evening while we were still finishing up--the power to drill the vent holes came from the batteries through the inverter, as well as all the lights. They ran the house without any complaint all through the night and well into a rainy morning, dropping only a tiny bit of voltage while I ran the dishwasher, washing machine, dehumidifier, and other things. This afternoon the sun has come out, so the batteries are being treated to their first taste of beautiful solar power!
Still to do: Finish covering up the shingle wires in the attic, and figure out a way to use a dump load. A dump load is a place to use excess solar power when the batteries are fully charged and the sun continues to shine. The ideal dump load is something that provides a needed service but doesn't really have to run at any particular time. My intention has been to use the dehumidifier in the summer and an electric space heater in the winter as my dump loads. But I asked Rick to look into the possibility of using X-10 home automation technology to control the dump load. X-10 sends signals through the house wiring to turn on and off lights and appliances. Radio Shack and others sell the equipment, including a variety of controllers--wall switches, remote controls, and computer interfaces. The Outback solar equipment has a means of generating a signal when dump-load conditions are met. If we can figure out how to turn this into an X-10 signal, I can then use any appliance or combination of appliances as the dump load by setting them to the appropriate X-10 channel.
One very interesting possibility for a dump load a few years from now might be a plug-in hybrid electric vehicle, or PHEV. This could make driving a car, at least for short distances, almost completely renewable--if you have a good source of renewable electricity handy. Which I do, on my roof!
Monday, August 01, 2005
New batteries arrive
A little bit of battery electrolyte was spilled in getting the batteries off of the truck (no loading dock, no forklift--just a scrawny teenager and a middle-age guy with a bad back). I cleaned them off carefully before we moved them to the basement. I called Rolls-Surrette to ask how best to recover the lost electrolyte. They said I should go the the auto parts store and buy some 1.265 sulfuric acid--same as they use in the battery. I'll restore all the cells to their full level once the batteries are in place (in the battery box that Rick is building for me). After they're refilled, I will only add distilled water as needed--the acid itself doesn't evaporate.
I'm not sure why Rolls ships the batteries wet. It would seem both safer and easier to ship them dry, and add the electrolyte on site. The batteries are heavy enough dry!
I'm excited about the new batteries. The system really doesn't work well at all with very-low capacity batteries. My electric bill for the last month was actually HIGHER than last year! (Yes, that was depressing.) But I was trying to see how much power I could get out of the shingles, so I turned lots of things on. Then, when the sun went behind a cloud, the batteries quickly discharged and the system switched to the grid. It also provided basically zero power for night-time loads. In addition, some extra power was used in doing the project--power tools, lights and fans in the attic, etc. The new batteries should enable me to match the solar energy with the loads properly--I hope I can get at least one zero-kilowatt electric bill before winter arrives.
Thursday, July 14, 2005
(See below* for explanation)
Unfortunately, because of the low capacity of my soon-to-be-replaced cheapo batteries, and because I didn't receive a functioning Outback Mate Controller until last Friday (7/8), I haven't been able to take full advantage of this large amount of power. Here are the daily kilowatt-hour totals for July so far:
Fri. 7/1 6.2 kw-h
Sat. 7/2 8.3
Sun. 7/3 9.1
Mon. 7/4 7.3
Tue. 7/5 1.3
Wed. 7/6 1.0
Thu. 7/7 1.0
Fri. 7/8 1.0 (Mate installed late in day)
Sat. 7/9 8.0
Sun. 7/10 10.2
Mon. 7/11 3.5
Tue. 7/12 3.2
Wed. 7/13 4.0
Another reason I'm not able to use the full amount of energy available is that I don't have a "dump load" set up yet. I plan to use the dehumidifier as my summer dump load--whenever the batteries are fully charged and the sun is still shining, the dehumidifier will run. On weekends, I have been able to run large loads while the sun is shining--dehumidifier, box fan, dishwasher, washing machine, rice cooker, etc. That's why the weekend totals are higher (it has been pretty uniformly sunny or partly sunny all month long).
* Explanation of charge controller display:
IN 54 V, 37.3 A: The maximum power point tracking MX60 is showing 54 volts to the solar shingle array and receiving 37.8 amperes of current.
OUT 52.8 V, 38.1 A: This is the voltage and current being used to charge the batteries.
WATTS 2011: The current power output of the shingles, equal to the voltage times the current (either IN or OUT, ignoring small internal losses in the charge controller).
AUX OFF: The auxiliary output is off.
kWHrs 3.2: Total number of kilowatt hours passing through the charge controller so far today.
MPPT: Maximum power point tracking. Means that the charge controller is presenting the optimum voltage to the solar array which will produce the most power. The charge controller periodically sweeps through a range of voltages, multiplies the voltage times the current, and finds the largest product. This is the MPPT voltage. This can change depending on the amount or angle of sunlight, the temperature, and other factors. MPPT charge controllers like my Outback MX60 are supposed to yield as much as 30% more power from a solar array than the less-expensive charge controllers which serve mostly to prevent overcharging the batteries (the MX60 also prevents overcharging).
Sunday, July 10, 2005
In case you can't tell what that is up in the sky, here's a closeup:
Sunday, July 03, 2005
Good News and Bad News
Which leads to the bad news. My batteries appear to be pretty bad. They were probably bad when I bought them, although overcharging them the first day the system was hooked up probably didn't help (although they shouldn't have overcharged so quickly if they were good). Basically, they have extremely limited capacity. They were fully charged last evening, but were unable to power the house through the night running only minimal loads--the refrigerator, the TiVo, a few battery chargers and a couple of clocks--probably around 100 watts on average through the night. This obviously won't work as the days get shorter and the nights longer, and I'm running more lights, the furnace, the TV, and other things off of them. Right now the system basically works when the sun is shining--the batteries are balancing out the load, but unable to store much power at all.
So new batteries are now on the agenda. I had hoped to get by with my $20 a piece sealed batteries, but that was a gamble that didn't pay off. I'll probably go with 8 Rolls-Surrette S-460 batteries, giving me 460 amp-hour capacity, or around two to three days of normal use without sun. Should make it through the night, anyway! This will add another $1600 or so to the cost of the project, but I'm already pretty numb to the costs. I'll be tallying those up soon and sharing them here--it's not going to be pretty, I'm afraid.
The other bad news is only temporary. Outback had promised to send me a new Mate controller via two-day air; instead they sent it via two-day ground--waiting two days to send it by UPS ground that is, so it will be here on July 8 instead of last Thursday.
So, right now I can run all sorts of stuff off of my solar roof, as long as the sun is shining! Good batteries and a functioning Mate controller will give me much greater flexibility. Stay tuned!
Thursday, June 30, 2005
Connecting the wires
The stripped ends of the wires are inserted into the inner metal sleeve of the splice, which is then crimped down on the wire to hold it securely in place and to provide the electrical connection. When both ends are connected, a heat gun is used to shrink the plastic cover securely around the metal and the wires, keeping dirt and moisture out.
I've made 100 of these connections between the shingles and to connect the shingle strings to the wires which eventually lead to the basement and the charge controller.
I got a few of them wrong, as we discovered last night. I'll fix them tonight. I'm also expecting to receive a replacement "Mate" from Outback. The Mate is the computer which communicates with and controls the inverter and the charge controller, monitoring the system. The one I had purchased apparently has a defective clock. I called Outback's customer service on Tuesday, and by telling me to push a few buttons they were able to confirm that the Mate was defective. They said they would send me a new one right away--hopefully it will be there when I get home. One the remaining connections are fixed, the system should be fully operational, with only a bit of final conduit work and other niceties left. Once these are done, we can call the inspector and hopefully get a final sign-off on the project!
Saturday, June 25, 2005
We got very close, but ran out of a few key supplies and time. We did get the system running in a reduced fashion, which was very rewarding in itself--we know the stuff works!
Rick spent most of the night working on the larger-scale wiring--the wires and conduit which tie the twelve series strings of shingles into the two big 4-gauge wires which take the power to the basement and ultimately the house. Here he is sorting out the wires for three of the strings:
The 84 shingles were laid out in 21 rows, four across. Alternate rows were slightly offset, which meant that the wires in the attic were offset as well. The wires were arranged in 8 plastic "raceways," grouped in four pairs. Each raceway pair contains the wires for 21 shingles--11 in one raceway and 10 in the other. Electrically, however, the shingles are grouped in sevens. To make this work, we linked the bottom seven shingles in each raceway together, and then the top four in one raceway with the top three in its adjacent raceway, yielding three series strings from each pair of raceways. The wires from the three strings were combined into two lengths of flexible conduit:
This conduit ties to a junction box, which serves to funnel the wire into rigid conduit which runs to the combiner box (above). The junction box also allows the series string formed by four shingles on one side and three on the other to be tied together--note the black wire which loops from one conduit run to the other.
While Rick was doing this macro wiring, I spent much of the night doing the micro wiring--splicing the individual shingles together, and then splicing them into Rick's macro wiring. Unisolar's instructions call for using heat-shrink butt-end splices. This is an excellent way of joining two wires electrically, according to Rick, but it's also a pain in the butt (and the knees and the neck, etc.) to do in tight, poorly lit spaces. Here I am in one of my many stress positions:
No, it's not as comfortable as it looks. Here's what I was doing with my face ten inches from the underside of the roof: First, I would find the two wires I needed to join, and make sure the ends were properly stripped (about 1/4 inch). I had a wirecutter/stripper tool resting on my belly which I used when the wires needed cutting or stripping. Next, I would grab one of the little butt splices and insert one of the wires into one end. I would then grab the crimping tool, also resting on my belly, and crimp the wire securely into the splice. I would then insert the other wire in the other end of the splice and crimp it. I got pretty good at this after a while, but then started to regress as it got to be 5 in the morning and I could no longer see or think straight. We had exactly enough splices IF I didn't screw any up. But I did, starting with the second one, and ended up maybe 15 splices short. I also managed at some point in the night to join two wires which shouldn't have been joined, which I'll need to fix later.
Nevertheless, between Rick's macro wiring and my micro wiring, we were able to get 5 of the eventual 12 series strings fully connected to the system. This meant we were able to power up the system and see what we're getting.
Here's a view of the Mate system controller's display at about 10:30 this morning, when the roof was getting pretty good sun:
67 volts in, 5.9 amps, for a total of 380 watts. This means we would have about 912 watts if all 12 series strings were online. The rated power for the array is 1428 watts (17 times 84), which would only happen when the sun's rays were directly perpendicular to the roof (which I'll get close to during the summer, but not at 10:30). So it appears that the shingles are performing pretty much as promised!
Unfortunately, about 11:30 this morning I started to hear gurgling noises from the batteries, meaning they were probably being overcharged (Rick and I must have entered the wrong settings on the charge controller, something we probably shouldn't have been doing at 7 in the morning with no sleep). I immediately flipped the switch connecting the solar array to the charge controller off. Hopefully the batteries haven't been damaged. Since they are used, the batteries are the weak link in the system--I was thinking I might need to upgrade them at some point. Hopefully that point isn't now!
I went out and bought the additional butt splices I need, and will head up to the attic and finish the micro wiring some evening in the near future (not tonight, though--I need some sleep!). I'll wait to hear from Rick (during or after his vacation) before I try to turn the system on again, so for now I've got an almost complete, almost working solar-power system, but I'm still running off the grid (and my two 12-V Evergreen solar panels I bought last year).
Friday, June 24, 2005
Starting the attic wiring
The combiner box contains the 4-amp breakers I had to special order from Virginia, and which arrived on Wednesday six weeks after I ordered them (as promised). The breakers guarantee that if one of the shingle series strings produces too much current, the breaker will trip and protect the rest of the system down the line.
Tuesday, June 21, 2005
One function working!
Friday, June 17, 2005
Solar shingles installed!
At 7:30 in the morning, the house didn't know what was about to hit it...
Although the stacks of roofing materials on the back side might have been a clue.
Once the team arrived--Rick, Lee and Zach--they went quickly to work stripping the old roof from the south side of the house.
Soon, the roof was stripped bare.
Hidden defects, including a rotten fascia board, had been exposed.
By the time the crew left for lunch, these had all been repaired.
Putting down the ice-guard underlayment on the bottom part of the roof was next.
Followed by the Elk Versashield fire-resistant underlayment recommended by Uni-solar for use under the solar shingles.
Ordinary asphalt shingles were installed starting at the bottom.
Holes were drilled in the top half, using a template. The holes were for the wires from the Uni-solar shingles to pass through into the attic. A 3/8-inch length of 1/2 inch PVC conduit lines each hole.
Inside the attic, the holes are temporarily covered by the channel portion of some electrical raceway.
Rick had to work in some tight quarters to install the raceway. Fortunately, it was not hot in the attic.
Once the raceway was in place, 1/2 inch holes were drilled through it to allow the wires to pass. (The PVC conduit lining the holes was placed after these holes were drilled.)
The spacing of the solar shingles was carefully determined (Uni-solar has fairly elaborate instructions for doing this).
The solar shingles are nailed in place!
As the shingles are installed on top, wires begin to appear in the attic.
After the first couple of rows, installing the shingles went relatively quickly.
The details of laying a solar shingle: First, short the wire leads by twisting them together (the short-circuit current from each shingle is small enough that this isn't a problem).
Next, feed the wires through the hole.
Line up the shingle.
And lay it into place, making sure the wires go all the way through.
Fourteen of the 21 rows of solar shingles in place.
Most of the holes have wires coming through them now!
Placing the last row of solar shingles.
And the last shingle!
The remainder of the roof was covered with conventional shingles, the roof cap was installed, and Rick and Lee did a few additional repairs and finishing touches, finally finishing after 9 pm. The weather was nearly perfect throughout.
Friday, June 10, 2005
Getting close to the end!
First, I forgot to mention that the system components had to be inspected. My cat Ragu inspected the inverter,
while Marcos checked out the solar shingles.
After the major system components were installed, Rick did a lot of work with the AC wiring. I currently don't have any 220-volt loads. If I did, they would have to run directly off of the grid, since I only bought one 120-V inverter. So Rick put the 220 breakers into the original power panel, and split the 110 breakers between the auxiliary panel that was installed when the house was added on to (before I bought it--center of picture below), and the new AC panel that is part of the Outback system.
Rick also replaced the service-entry cable, since the old one had cracked insulation which was letting water in (never a good thing in electrical systems!).
This week, Rick worked on the DC side. Using 880 pumps on a crimping tool he borrowed from McNaughton-McKay Electrical, he attached lugs to the battery cables:
He also ran the 4ga DC wires through the conduit from the basement to the attic.
The basement wiring is now just about complete.
Next week, probably Thursday, we will strip the old roof (south-facing side only) and install a new one comprised of 84 Unisolar PV shingles and enough ordinary shingles to cover the rest. We will be using Elk Versashield underlayment under the solar shingles as recommended by Unisolar.
Once the shingles are in place, we'll have to wire them up in the attic and connect them to the rest of the system. I'm still waiting on some 4-amp DC breakers I ordered from Virginia; hopefully they will arrive before we're finished with everything else. After that, we should be able to turn the system on!
Once we're done, I'll tally up all of the materials and costs of the project. (Guess what--it's costing me more than I estimated!) After that will come what should be the most fun part of this web site--tracking the performance of the system.
Wednesday, April 20, 2005
Making progress, slowly, surely, expensively
However, it does raise other issues. First, I have already bought 80 shingles, and 80 isn't divisible by 7. So I had to find four more shingles so I can have twelve strings of seven. Unfortunately, the shingles are in very short supply right now. A store in Phoenix was able to locate four for me, but at a premium--I paid $150 per shingle, as opposed to about $105 that I paid for the first 80. Also, the wiring in the attic will be a bit more complicated because the 84 shingles won't be organized quite as simply as 80 would have been. But we'll work that out. I've ordered most of the rest of the equipment we'll need to wire the thing up. We're hoping to do the shingle installation in mid-May, with most of the other work done before that. Hopefully I'll be running my house on solar power by Memorial Day.
Monday, April 04, 2005
The Most Important Step
Still, most of the savings came from reducing my usage--replacing most of my incandescent light bulbs with compact fluorescents, turning lights off more diligently, and putting "phantom loads" on switchable power strips. "Phantom loads" are electical devices which are on even when they're off, like a clock on a microwave or VCR, or anything with a remote. These thing frequently draw three to five watts each, which adds up to a lot of electricity over the course of a month. Putting them on power strips allows you to easily shut them all the way off.
There are several other easy steps that can be taken to save power, and almost all of them are cheaper than buying more solar panels and batteries.
Once I get my PV system up and running, I'm going to go back and look for more ways to cut my energy use. A new furnace is probably the most obvious choice--the new high-efficiency gas furnaces will save me both gas AND electricity, since the generally have higher-efficiency blower motors than does the 1988 dinosaur in my basement. However, I may investigate something more elaborate, like solar-assisted radiant heating, or maybe incorporating a wood stove or through-the-wall solar, or a ground-source heat pump.
Wednesday, March 30, 2005
Saturday, March 26, 2005
After we got back, Rick started drilling the holes for the mounting plate:
A short while later, the plate was in place:
Next, we attached the inverter
the AC disconnect box,
and the DC disconnect box.
Unfortunately, the mounting plate is laid out so that the AC is on the left and the DC on the right, which is exactly opposite from what my basement layout calls for. The AC power center is at the right side of the wall, and the DC wires from the solar shingles will be coming from the left. All it really means is just a few extra feet of wire and conduit, and Rick has already figured out how he'll arrange it.
We were also able to run conduit from the basement to the attic inside an interior wall which separates two bedroom closets. Rick drilled holes in the first floor and the attic floor. I pushed the conduit up from the hole in the basement and Rick grabbed it in the attic and secured it. All of the shingle wiring in the attic will eventually lead to two wires carrying about 72 volts DC. These wires will feed through the conduit we ran today, and tie into the DC disconnect box on the panel, which will then link them through the charge controller to the batteries. The batteries will be connected back through the DC box to the inverter, which will be connected to the house wiring through the load center, and to the grid power as well.
The project is already showing that Kermit was right--it isn't easy being green! While going to solar power would seem pretty green, I've already had to bend a few of my principles. For starters, I normally prefer to avoid big-box stores like Home Depot in favor of local hardware stores, but it is unlikely that any local hardware store would have had all the stuff we needed, and it would have added on to this already very expensive project. Secondly, the conduit we bought is all PVC, which like pretty much every product made with chlorine is an environmental hazard both to make and to dispose of. Rick explained the trade-offs to me with PVC's competitor, metal conduit, which isn't perfect either, and is harder to work with. Rick's green credentials are excellent, so I went with his recommendation to use the PVC. Third, I am "financing" this project using 0% credit-card offers from Chase and Citi. I'd like to think that I'm sticking it to these evil corporations by borrowing their money interest-free, but in reality I'm probably sticking it to their less-fortunate customers who don't own houses or otherwise have my credit rating. The alternatives, however, were either waiting a while longer to do the solar project (continuing to pay DTE for coal- and nuclear-generated electricity), or cashing in several CD's at my credit union. Finally, I'd prefer to buy stuff that's made and sold locally, but I ended up buying all of the solar equipment from internet stores--in Massachusetts, New Mexico, and Arizona. My excuse there is pretty good--there's no store anywhere near here that sells any of this stuff. And both Outback and Uni-solar are American companies, and all of the Outback equipment is American made (the Uni-solar shingles are assembled in Mexico, even though the company's main factory is in Auburn Hills, Michigan, just 50 miles from here).
Monday, March 21, 2005
80 Uni-Solar SHR-17 solar shingles, purchased from the Alternative Energy Store, Worcester, MA: $8685, including shipping.
From the Solar Panel Store, New Castle, CO:
- Outback FX2548 Inverter, 49-volt DC to 120-volt AC, 2500 watt max. output: $1640
- Outback FXA Adapter Kit: $109.65
- Outback PS2MP mounting plate: $103.20
- Outback HUB-4 Communications Manager: $165.75
- Outback RTS Remote Temperature Sensor: $24.65
- Shipping for all above items: $70.20
- Outback MX60 Maximum Power Point Tracking Charge Controller: $499
- Outback PS2AC-50D AC disconnect box: $305
- Outback PS2DC-100 DC disconnect box: $260
- Outback Mate Remote Monitor and Control: $235
- Shipping for above items: $78.97
The batteries cost me $300.
Here's all of the Outback equipment in the boxes...
And here it is unpacked:
On the left is the charge controller; third from the left is the inverter. The two big boxes are the disconnect boxes (AC and DC), and the mounting plate is shown behind.
Monday, March 14, 2005
Remaining Solar Equipment Ordered
P-V Shingles in Action
So I bought them all (he actually sold me all 18 for $300); they should perform at least adequately for my 48-volt system (I'll use the 16 best ones and keep the others as spares). I had to make two trips to Whitmore Lake to haul them all back--they weigh 70 pounds each and I didn't think my VW would handle them all at once. I lugged them all to the basement, checked their voltage with my multi-meter, and started charging the ones that were low. Here are some photos of the batteries:
Friday, March 11, 2005
Ordering the Equipment!
The wires from the shingles will run through conduit from my attic to my basement, where they will connect with an Outback MX60 charge controller.
The charge controller regulates the voltage to the batteries, enabling quick charging and protecting them from overcharging. The MX60 allows for input voltages substantially higher than the battery voltage--the 72 volts from the shingles will be charging a 48-volt battery bank.
The batteries will power an inverter, the Outback FX2548, which converts 48-v DC power into 120-v AC. This will then be connected to my household breaker panel, providing power to my household outlets. The inverter will also be connected to the grid so that when the batteries are low I will be able to switch to grid power. When this happens, the inverter doubles as a battery charger, allowing me to recharge the batteries while running my house from the grid. Hopefully this won't be necessary too often--probably just a few long, cold winter nights each year.
The Alternative Energy Store is putting together a bid for me to combine all of the various Outback devices--charge controller, inverter, system monitor and control, and a variety of connectors, breakers and disconnects--onto a single pre-assembled panel. Whether I go with this method or order the parts separately will depend on the relative cost and the advice of my electrical specialist, Rick.
Batteries are my biggest remaining wildcard. Batteries are expensive, heavy, and require periodic maintenance (unless you go for much more expensive). I'm torn between buying lots of batteries, enough to get me through five days without sun, or economizing and relying on the grid when the going gets cloudy. I'm going to check with a few people to see if I can get a good deal on some slightly-used batteries.
Anyway, I'll be posting photos and updates on my progress on this blog from time to time. If you have questions, you can leave comments here or e-mail me.