01Apr

New Projects at the Solar Shed

I wrote the material below quite a while back and it somehow fell through the cracks.  I have since gone through a couple of variants of a Zero Export Grid Tie system, including a new one this past weekend…and the power company’s meter hasn’t budged since!  Read this to get up to speed and there will be more on the latest changes.

The season is changing and so are the solar connections at the Solar Shed.

Grid Tie can be the cheapest way to get into solar and can even turn a profit for you in some places. In other places, the system is rigged.

A much cheaper way to do Grid Tie is a Zero Export Grid Tie (ZEGT) system, using solar power mixed with grid power to run your loads, but not to back feed into the grid. I call this “house tie solar.”

Why is this even a “thing”? Why not just grid tie, using the grid as a virtual battery? Straight grid tie with net metering is a great deal where you can get it. Daryl, in Texas, has a great deal on grid tie and his huge system actually makes him an income stream. A lot of places you can’t get it, though. A lot of places where you could get it have changed the deal. Bruce, in Pennsylvania, ran into this. He’s the one who reminded me of ZEGT.

Let’s say you live in Alabama. I think a recent article said they have $50/month tie fee and it is going up! Here in Scenic West Bogia Heights, Florida, that’s sort of the same sort of deal, but ours is higher if you can even work it out. You pay for a bunch of extra metering equipment and an electrician to install it. Your solar system has to be signed off by a certified tech. Then, on a monthly basis you have your basic $40 connection fee and a $60 solar fee. That a hundred bucks of power bill before anybody gets any power.

Turn on the juice and all the power that you make and don’t use at the time goes to the power company for less than 4 cents. At night, you get to buy your own power back for 13 cents. I am no math genius, but I think under these conditions it will cost you more to have solar power than to go without. Maybe we should run some numbers on this.

Let’s say you use 1500kwh per month. You build a grid tie power system that can supply 1500kwh per month. At 13 cents that’s $195 from the power company. Now let’s figure that the a/c and fridge and the miscellaneous loads (like the clock you can’t set on the DVD player) will use 500kwh in real time, reducing the intake from the power company to 1000kwh, which at 13 cents is $130. 1000kwh of your excess daytime power went to the grid at 4 cents per kwh. You get a credit of $40 off the $130 net grid import, so you have to pay $90 for your power. You also have to pay another $100 for the meter and solar fees. That makes your bill $190 with your grid tie connection. Without it, your bill would have been $195 plus the $40 meter fee, or $235. Ok, so you did save $45. Did I mention that West Bogia Power and Light also requires that you buy a multimillion dollar insurance policy to indemnify them should your dinky little power system damage their grid! The average squirrel can cause more damage to their system than a proper grid tie system can! Hold on, now, I have a solution or two for you.

First of all, and this costs little or nothing, change your ways. If you use more of that solar power before it leaves the house, then they don’t pay you 4 cents and charge you 13 on the power that goes out and comes back. If somebody is home during the day, do the laundry and baking then, instead of in the evening. Set the thermostat for more run time during the day instead of at night. If no one is home during the day, is someone close enough to come home and start the dryer? If nobody can make it home during the day, start a crockpot meal before you leave for work and set a water heater timer to heat during the day. Look into smart appliances that can be controlled with a phone app while you are away!

Having shifted your loads a bit, you are now burning 1000kwh of solar and 500kwh from the grid. You are also selling 500kwh to the grid. That comes to 500 x 13cents to buy, 500 x 4 cents to sell for credit or $65-20= $45. Now add in the various fees and the bill comes in at $145.

Let’s review. Your bill without solar would be $230. Your bill with the first grid tie example would be $195. Changing the routine a bit the bill with solar is $145. OK, I think we are getting somewhere. What else can we do?

The availability of ZEGT can help get new prospects into solar and can help get folks who have had the rules changed on them get back into a profitable state.

Let’s go back to our example, only now no power is backfed to the grid. We CAN make 1500kwh, but we still only use 1000kwh during daylight hours. We discard the excess capacity because we are not exporting to the grid.

As with the previous example, we are importing only 500kwh from the grid. Again, that’s $65 for power, no credit for exported power, $40 for the meter fee and NO SOLAR CONNECTION FEE. That makes the bill $105!

Let’s try that in the example before changing our ways with power consumption. I believe we were using 500kwh of solar, dropping what we buy from 1500 to 1000kwh. That’s $130 for the power you buy, plus the $40 meter fee, for a total of $170 as opposed to the $195 you were billed when the power company was “buying” your excess power!

As usual, your mileage may vary. Your power company may charge more or less, pay more or less and have different requirements and fee structures. Zero Export may or may not be for you. A lot of you have banged on the calculator and are now wondering what it is going to take to build your new ZEGT system or convert your existing GT system.

If you have an existing GT system, RTFM. That’s right, read the fine manual for your GT inverter. Many, especially those made in the last few years, have this capability built in if you add a device to monitor the power line and report back to the inverter. These go by various names, often coming in the form of a power meter or electricity meter, originally intended to just let you monitor your system. Two current transformers slip over the grid lines coming into your breaker box. They connect to the “meter”. The meter has an RS485 (or other communications standard) that connects with the GT inverter. A few changes are selected from the inverter’s menu and now the inverter knows when the solar power need to get in and out of the mix to match the consumption, when possible, but not overdo things and send power out. Hence, you can tell your power company to pull the extra meter and discontinue grid tie.

If you do not find anything on export limiting in your manual, check out a company called ELGRIS. They have an export limiter that they claim works on a lot of GTI models and may have one for yours.

Now for new solar users, hold on. There are reputedly some inexpensive modules that will do the trick and installation is pretty easy. I say reputedly because I have not personally tried it, but I have heard good things. I have ordered two units and will quickly get them installed on my minigrid for testing the ZE claims. If that goes well, then I’ll go live with them and report results, like whether or not the power company busts me for backfeeding. Tom got a visit from the power company within 2 hours of inadvertently backfeeding his system, so going up against West Bogia Power and Light with these new gizmos is a really good test.

I’ll let you know.

–Neal

08Feb

Why Me?

Kris Kristofferson had a big hit with a song on that theme. Instead of moaning about why things had gone so wrong, though, he was wondering why good things had happened when he felt he didn’t deserve them.

Well, things can go wrong in your solar power system, just like anything else, and you’ll have to get off your wallet to fix them.  You can ask, “Why me?”, but if you are just feeling sorry for yourself it’ll likely happen again.  If you ask “Why me?” constructively, that is to say, analyze what you might have done differently, you might end up with a better and stronger system that won’t have such a failure in the future.

Here at the Solar Shed, I have all kinds of experiments running.  Many are temporary, but sometimes stick around longer than expected.  If I get sloppy on these temporary rigs, then it can get expensive.  Also, different circumstances seem to offer different “learning experiences”.

Example 1–Do you know what the schematic symbol is for an antenna?  Visualize an upside down wire coat hanger and you have a pretty good idea.  If you have 3 solar modules in series, you can twist all the wires together and have the pair for the downline together or you can have them take the shortest path, with ends up with a more or less triangular circuit…just like the antenna symbol.  Now, a loop antenna is directional, so if lightning hits the tree over yonder, the induced current from the blast may be out of phase and not bother your system a bit.  OR it may be 90 degrees around and channel the hit right into your system, which can get expensive.  Trust me, I know this to be true.  Keep your wiring tight and not looped.

Example 2–If you do not have a surge arrestor on your system, you should not complain about a surge getting in and causing havoc.  In the spring time, we have some really nasty lightning storms around here.  I mean, go hide under-the-bed-with-the-cat-bad storms.  In a case of Example One and Example Two combined, you may discover interesting things.  For one, a charge controller might NOT be injured by lightning, but because it operates slowly it can pass it along to your inverter.  The inverter monitors its output and adjusts according to the input with which it has to work, but this adjustment is not lightning fast, so you can get some really interesting effects.  One brand of inverter I had online would blow its display board.  It was the weakest link and it took the hit, saving everything else.  It would run just fine without the board, but I had spares.  After a couple of times of this, I was out of spares and decided to run without display.  I had other meters.  I did, however, lash up an output surge arrestor.  Good thing.  The next storm did not kill the inverter, but it wiped out the feedback loop, so it got the urge to keep making lots of voltage…lots more than is considered socially acceptable.  Fortunately, I had put in that output surge arrestor and only it went up in smoke.  Otherwise, everything in the house on that circuit would have been destroyed.  The saddest part of the story is that my new 48v system, not yet online, lost its big 12kw inverter.  Have you priced a 12kw inverter?  They cost a lot more than surge arrestors!  I think the system packages that Sun Electronics sells pretty much have arrestors in the kit, but ask.  If building a system a la carte, install surge arrestors!

Example 3–Nothing bad happened, here, because I was prepared.  Lots of gear has fans in it.  All of my charge controllers have them and the Sun King 5548 inverter that I built in the shell of my deceased 12kw inverter recently had one of its fans start getting noisy.  There is a manual fan in the top of the case that I use a lot in hot weather and another fan operated by a thermostat on the transformer.  That one never runs as I am running 5500 watts on a 12,000 watt transformer.  Right down on the driver board, there is a small fan that runs based on the heatsink temperature.  This one is pretty important and it would rumble and howl when it started up.  In this inverter’s design, heat won’t cause it to blow up, but it will shut down until it is comfy again.  Having the lights and a/c blinking on and off on a warm day is really annoying.  Folks, when your fans start talking you need to listen.  I have a drawer full of fans for just such occasions.  I bought two extra when I built the inverter and I have several more dissected from old PC power supplies by an 11 year old who likes to take things apart.  Never throw away working fans!  If you buy replacement fans, TRY to get ball bearing fans.  They cost more than fans with sleeve bushings, but they last WAY longer.  The specs, like voltage, current and airflow (CFM) are usually printed on the hub of the old fan.  Listen to your fans.  They mean it!

Example 4— Pay attention to the meters.  I recently pulled a set of 2 year old batteries from the system.  Why me?  I have batteries 5 years old that are just fine!  Interestingly, it wasn’t just one battery with a bad cell.  I was hoping to use some of that set in other 12 and 24v systems around the farm, but No-o-o-o-o, they were all bad.  Curious.  Well, it seems I had two charge controllers that had a bad firmware revision and may have had some damage from all those lightning episodes.  Since they run less than half the power for the whole system and otherwise seem well-behaved, I ignored the high-ish afternoon voltages, thinking they were supposed to go that high as part of their multistage charging act.  Nope, they were cooking the batteries.  Pay attention to the meters.  They are there to tell you stuff!

Example 5–Unless you have sealed batteries or some of those fancy Lithium packs, then there’s a good chance you will need to add water to your batteries from time to time.  How often depends on how hard and how deep they are cycled.  If you pretty much use up the battery at night and have enough solar to charge it hard, you will probably go through a good bit of water.  Once a month is probably good for most folks, but that previously mentioned set that died young was going through gallons every two weeks.  Keep the water above the plates and use only distilled water.  It is only a buck at the grocery store or WalMart.

Example 6–Keep your terminals tight and clean.  Terminals just get loose and need to be tightened.  Otherwise, they can run hot and waste power or even burn off the lugs of your battery or inverter.  Just today, I opened the cover of a charge controller to get to the temperature sensor wire and while I was in there I decided to check the terminals.  Two were not loose enough to cause harm, yet, but needed to be snugged up, just the same.  On your batteries, you can add the threat of acid corrosion.  Don’t let that green stuff build up.  Clean it up and coat with grease for protection.

Example 7–Pay attention to the heat.  I haven’t had any problem from this, but it got uncomfortable in the Solar Shed’s control room/man cave last summer.  There was no ceiling, then, and the backside of a solar panel is hot.  The IR thermometer showed 140-150 degrees and the room was routinely over 110, even with the door left open.  This had its own issues, like random animals showing up on the couch.  The a/c I had didn’t even stand a chance.  There is now a ceiling and insulation, so much of that issue is handled.  I will be adding a vent fan and, budget permitting, a mini-split heat pump.  Mostly the heat pump will be for me.  A check of the spec sheets on all the gear indicated we were well under the too-hot mark.  If you don’t have temp specs, you can check the equipment itself.  Lick a finger and touch it to a transistor.  If it doesn’t sizzle, you are good.  If it sizzles, you are close to the limit.  If you don’t get back all of the finger, then it is too hot and you need to cool things down.

–Neal