Solar powered workshop - take two. - Page 1
Forum section: electronics / projects

author: Kibi
author_rank: Unknown
timestamp: April 28, 2013, 06:46:20 pm
content: Hello everyone.A few months ago I posted about my off grid workshop. The batteries turned out to be a failure, so I had to start from scratch. I have saved up some money and bought some more components. So here we go for the second take.A shopping list had to be devised. One important component is the charge controller. I'd heard good things about Outback products, but then discovered there was a better alternative. Midnite Solar make a Classic charge controller which is a lot more powerful and has pretty much all the features you'd want built in. Cool, I then spent many man hours searching for a better charge controller than the Classic, but failed.The charge controller needs to be well built to ensure reliability and it needs to be future proof. The Classic does this. I'll max it out at 1KW on my 12V system, but with higher voltage battery banks in the future I'll get close to 5KW out of it. What more do I need from a charge controller?I am on a 12V system because I have a 12V Victron inverter that served it's previous life in an ambulance. I also have several other 12V loads, so 12V works for me at the moment.So, lets get started with the install.First in line is a combiner box with surge protection. I went for a Dehn PV designated SPD with replaceable modules and remote status contacts.The fuse holders are 1KV rated with 1KV rated fuses at 15A. The 1KV fuses are expensive. They cost as much as fuses in a good multimeter, which should also be 1KV fuses, but I deem them necessary.The Dehn SPD.FusesI have found an inexpensive IP65 rated DIN rail box made by ABB to mount all of the components of the combiner into.Now, it's time to connect everything up.I had some spare cable lying around. It's the type that a rude boy might use to cobble his sound system together with in his car. It's over rated, but it'll work well and it's free.I wasn't prepared to buy more cable for the run from the combiner to the breaker box when I already had plenty of 25mm² earth cable, so I marked the ends and used that instead.Now we have build a DC disconnect box. Again, ABB came through with a good sized box. It's IP65 rating is not necessary as it will be inside, but it's perfect for the job.Midnite make a really nice DC disconnect box, but it does not have enough DIN ways on a single side to meet my requirements.This box lives inside and contains some staunch DC breakers. You must NEVER use AC rated breakers on DC systems. AC breakers do not have the arc extinguishing abilities that DC breakers do. AC rated breakers from your local Toolstation are remarkably cheaper, but they will make a fire, when opened, quicker that you can light your BBQ.I have a 250A breaker for the inverter, a 100A breaker on the output of the Classic and a 63A breaker to the PV input of the Classic. All of these breaker are disconnecting breakers which makes it convenient for me if I need to switch certain circuits off manually.The disconnect box also houses a 60A DC breaker which is the main breaker for all of my DC loads. Downstream of this breaker are six 600V fuses for each of the DC circuits which include home-brew LED lighting, computer, and security systems. There is also a circuit for the Victron BMV-600 battery monitor and an Arduido MEGA which grabs data out of the BMV-600 and reads some DS18B20 temperature sensors.Arduino with ethernet board for posting to Cosm (now Xively) and a top PCB for connections.I don't have a high capacity crimping tool for the 70mm² cables, so I cut a pocket out of a piece of aluminium stock on the mill. The pocket holds the connector snugly. I then proceeded to beat all seven shades out of the top of the connector with a hammer and nail punch. That connector is not coming off.Things are starting to come together. Power cabling is in as well as the data cabling.All of the breakers are labelled. All of the data connections are presented on the side via panel mounted Neutrik connectors and labelled accordingly.Now that the DC disconnect box is ready, we need to install it and the other bits of equipment.The inverter is mounted above the DC disconnect box. The DC disconnect box now assumes it's vertical position which is the position that the big DC breakers need to be mounted in, to avoid fires.DC disconnect box mounted and the PV inlet cables connected.Inverter DC inlet cables connected.I have modified the bottom tray of the inverter to accommodate Neutrik Powercon mains in and out connectors to aid in easier removal of the cabling if necessary. I have also included an RJ45 connector in order to present the RS485 in a neater fashion.Next up is the Classic charge controller. It's actually made in America, so it's made of metal and the PCB's are conformally coated, you don't see that very often these days!The Classic is mounted and all connections made into it.Everything is mounted, closed up and ready for testing.Now, I did try an experiment a few months ago with some old UPS batteries that I found in a bin. All 96 5Ah batteries were wired up in parallel to make a nice big 12V pack. Managing 96 12V 5Ah batteries in parallel proved to be a bit of a nightmare, so the "Time Bomb" had to go. It's not all bad, I have a use for these packs. Stay tuned for details later on.The original battery bank has now been replaced with four Lucas 355Ah 6V batteries in a 2S, 2P configuration. Two parallel banks is a lot easier on the heart.This bank now gives me twice the capacity of the old one.After the big switch-on, everyone is happy. Power is flowing, data is flowing.The inverter is currently keeping an eye on the batteries until I get the PV's installed. I don't have time to do it right now, but I'll report on further progress.Here are four Renesola 250W poly panels awaiting installation.

author: SeanB
author_rank: Super Contributor
timestamp: April 28, 2013, 07:04:41 pm
content: Very nice, just in time for summer as well.

author: croberts
author_rank: Regular Contributor
timestamp: April 28, 2013, 07:05:14 pm
content: Hello KibiWell done! Looks like a great system and I'm so glad to see you using solar energy to power your workshop. With the excellent equipment and that great installation it should serve you for many years to come.

author: SeanB
author_rank: Super Contributor
timestamp: April 28, 2013, 07:12:37 pm
content: I am just using a simple system to do lighting, and it is working out well. Might have saved about $10 so far in power, but the convenience of having light during power failures ( Yey Eishkom) makes up for it. For longer ones I have a small genset and a long cable to put it out of the way.

author: Kibi
author_rank: Unknown
timestamp: April 28, 2013, 08:04:01 pm
content: Quote from: SeanB on April 28, 2013, 07:12:37 pmThanks ChrisThe Classic will last a really long time. I cannot find a better charge controller, 96A battery current should keep any bank happy.The Victron is perfectly fine for now. In a home environment it will be a bit stretched. The Classic will also be a bit stretched on a 12V system too, but with a 48V battery it would supply all the power you'd need.So, with 14 more 250W panels, some more batteries and a 48V 5KVA inverter to go, I'm more than halfway there. I now need to save up for some land on which to build my house.The idea of doing this now is to learn what to expect from a PV system. Nothing is more emotionally crushing if you have a wife and baby to find that your PV system is not working "as advertised".SeanEskom, are they still going?Living in the ZESA days in the 90's, I know all about the importance of some light. ZESA are apparently doing a bit better these days, I don't know if it has anything to do with Kariba being full or they are importing from SA?Did you notice that the one of the DC breakers is made in Lesotho? I didn't even know that water was made there, but apparently, this is the Americans' preferred supplier of DC breakers. Who knew?

author: Joules
author_rank: Contributor
timestamp: April 28, 2013, 08:30:04 pm
content: Nice install Kibi, we also have a solar powered workshop. 750w of panels on the workshop roof, Outback charge controller and two 6v 400a batteries wired in series for 12v. The rack I built has x1 1kw inverter and x2 250w inverters all true sine Studer's. We can power the workshop lathe or mill off the 1kw inverter and run the household network and internet gear off one of the 250w inverters. All portable computing that we use is powered and recharged from the solar. This system has been up and running for in excess of 3yrs. The distribution panel is a very Heath Robinson setup made from an old key cabinet, flattened copper pipe for bus bars and a 500a shunt for monitoring. It's a 500a shunt because thats what I had. Will try to post some pics soon.

author: ddavidebor
author_rank: Super Contributor
timestamp: April 28, 2013, 09:02:03 pm
content: amazing!

author: Kibi
author_rank: Unknown
timestamp: April 28, 2013, 09:06:37 pm
content: Nice one Joules. It'd be nice to see some photo's of your install, no matter how ghetto.It's quite comforting to know that you get all you need out of a 750W array in Great Britain. I have a 1KW array to be installed, but there is a big problem with shading in the afternoon time, so I hope to get all the energy I need in the morning time. I can get full sun until about 1:00pm, so I should be OK.One of those 250W panels gave me 5W whilst it was relaxing nicely in the shade under a pine tree, so I have high hopes.

author: Joules
author_rank: Contributor
timestamp: April 28, 2013, 09:34:04 pm
content: We have a CTEK charger to top the batteries up in winter when the low sun and short days are a problem. But it does mean we mostly have full batteries and a good buffer should we have a power cut. I am limited in the workshop during the winter as it has no heat, but enough solar still to drive all the network gear and things like iPads and the electronics bench. Summer we usually struggle to use the power we generate. We hit our first megawatt of power generated and used a few months backIt's also worth considering a generator too for backup, we have a few as power generation is one of my interests, but you only need a small one really.

author: Joules
author_rank: Contributor
timestamp: April 28, 2013, 10:23:11 pm
content: First off is the panels... Six Kyocera 125w panels, I can't believe how much they cost us then and what you can buy now.The frame they are mounted on is made entirely of stainless steel, very heavy but going to stay put as its anchored via 6 load spreading plates inside the workshop loft, and since I built it myself cost less than a commercial frame.This is the rack, middle inverter has been switched on for 3yrs+ and in that time has only been off for a few hours during maintenance. I have been very pleased with these inverters. I decided on different sizes for different loads and switch them in as needed. This really reduces the parasitic loads of running one large inverter. The 1Kw inverter can drive machines in the workshop, or the LCD projector for an evenings film and provides power to my PC's during the summer when working on CAD etc.It also provides us with a loaf of bread a day during the summer as it will happily supply the bread maker.The key cabinet distribution board. The insulated plate is a cut down perspex EXIT sign, the bus bars are flat 22mm water pipe. All the main cables are welding cable of differing sizes as it was the best and cheapest copper cable I could get. No worries over volt drop here. Errrr yeah the crimps are all copper too and made on my hydraulic press. I did a few test ones and cut them open to make sure the bundle was tight and wouldn't slip, so far so good.So that is my urban off grid solar install.

author: RCMR
author_rank: Frequent Contributor
timestamp: April 29, 2013, 06:34:56 am
content: I still don't understand why people insist on using low-voltage DC storage and then push all that power through an inverter (single source of failure) to make their AC.Some years ago I designed (and did some small scale testing) of a system that used a bank of 180V batteries rather than the conventional 48V.The 180V DC was then reticulated to the point where the AC was required and converted to 240VAC by way of a low-cost FET H-bridge operating in PWM mode to deliver a pretty fine 50Hz sine-wave (with RFI filtering of course). These H-bridge DC to AC converters are small enough to build into a regular mains-power outlet.What are the benefits of such a setup?Well it's *far* more scalable than a 48V/Inverter setup. Whenever you want to add another wall-socket you just add one of those small H-bridge DC to AC converters.The efficiency of an H-bridge DC-AC PWM converter is always going to be higher than an inverter so less power is wasted.There is no single point of failure (aside from the battery itself. If an H-bridge fails, the rest still work just fine.It can be made cheaper than an expensive inverter-based system, especially if you also have a spare inverter on standby to guard against failure of the primary one.The I2R losses from your PVA, wind generator or whatever other source of renewable energy you're using are lower -- given that these may be located some distance from your batteries, using a higher-voltage feed at lower currents produces lower losses.If you're a perfectionist, all the distributed DC to AC converters can he sync'd to a crystal controlled "waveform generator" to guarantee frequency accuracy and guarantee that all outlets operate "in phase" with each other.Downsides?In many countries you can't fiddle with more than 50V yourself -- you must have a qualified electrician -- so a 180V batter, charge system and reticulation wiring might not be DIY stuff.Other than that -- you tell me what's wrong with this concept?

author: Harvs
author_rank: Super Contributor
timestamp: April 29, 2013, 07:56:18 am
content: Quote from: RCMR on April 29, 2013, 06:34:56 amYou already hit the nail on the head. In Oz, legally, with the bank at 180VDC, the whole thing becomes off limits to anyone without a licence. Not just performing the wiring, but any battery maintenance as well.

author: Joules
author_rank: Contributor
timestamp: April 29, 2013, 08:16:29 am
content: 12 volt systems are cheaper to build if your on a limited budget. The other big plus is you can use equipment designed for automotive use. So salvaging fuses and other gear becomes simple. If I could have afforded the batteries the system would have been 24v. However as this project grew out from a single panel to test the idea, the first inverter was 12v that is what the system grew up as. You are looking at 5yrs for me to complete that install bit by bit.

author: kripton2035
author_rank: Super Contributor
timestamp: April 29, 2013, 08:45:52 am
content: I'm looking at some sort of synchronized bunch of inverters.if you have a main clock, that all your inverters are synchronized with ityou make lets say 10 inverters of 24v it should make a 240v ac together ?and you have smaller batteries and inverters. you can have one inverter as a spare.does such a (commercial or not) system already exist ?

author: Kibi
author_rank: Unknown
timestamp: April 29, 2013, 08:49:41 am
content: My guess would be that the single point inverter system is a lot easier to integrate into existing wiring and protection systems.High voltage DC breakers are big and expensive.With MPPT charge controllers these days, the distant generation sources can transmit at high voltages to reduce losses. My Classic can accept 150V sources. Other models in the Classic range support up to 250V input.The charge controller, batteries and inverter are usually in close proximity of each other, so losses are negated there.Inverters are not frightfully expensive anymore and good ones are very reliable. As Joules posted earlier, he's got three Studer inverters, none of them have failed after many years of service. My inverter has had a rough life in an ambulance for many years before now.

author: Kibi
author_rank: Unknown
timestamp: April 29, 2013, 08:54:15 am
content: Quote from: kripton2035 on April 29, 2013, 08:45:52 amYes, Victron do this. Their larger inverters can be connected together and they constantly synchronize with each other. If I remember correctly, you can have six inverters in parallel or three pairs of inverters to produce a three phase supply.I am certain that other manufacturers also support this mode of operation.

author: kripton2035
author_rank: Super Contributor
timestamp: April 29, 2013, 12:43:33 pm
content: in fact it's not a bunch of inverters but a bunch of 24v sinus making, then sum them up and you get a 240v sinus.

author: SeanB
author_rank: Super Contributor
timestamp: April 29, 2013, 04:16:33 pm
content: Kripton, you will need to have isolated outputs, otherwise you will only have 24VAC or you will blow up output stages.Kibi, the ones made in the mountain kingdom are Heinemann then, as they had a factory there which was taken over by CBI a while ago IIRC. There still is a local electrical component manufacturing industry here, even if Cadac outsourced all the products to China, as the Iscor/AcelorMittal steel they use was actually cheaper to buy in China than locally, despite the factory literally being down the road and having a truck to collect it.

author: Joules
author_rank: Contributor
timestamp: April 30, 2013, 12:19:25 pm
content: The traditional way of calculating your solar was to add up the loads you wish to power and build a system with enough capacity to provide that load over X days or hours. We built what we could afford and work on an energy budget. During peak summer we can pull upto 2kw a day as long as you know the next day will also be sunny. Ususally we pull about 1kw a day. Our battery bank has a capacity of 4.8kw total, I wouldn't really want to pull more than 50% of that without recharging, but at a push and reducing the battery life span we can draw upto 80% capacity. In winter we struggle to make more than a few hundred watts a day, hence a backup generator and mains charger if it looks like we are heading into our 50%. This is still an on going experiment to see how we can manage with the energy budget we have through out the year. As we get older and electricity gets more expensive I am planning for retirement with a system that can provide us with some home comforts even if we can't afford mains electricity. Sounds grim!!! Well some families live like this already where they can't afford energy and food so have to choose one or the other.

author: croberts
author_rank: Regular Contributor
timestamp: April 30, 2013, 03:17:06 pm
content: Quote from: Joules on April 30, 2013, 12:19:25 pmEight 85W solar panels power my LED home lighting system. My house has a shed roof that slopes facing north and is shaded so I designed adjustable (azimuth and elevation) racks for the panels. The racks are on the ground so I have easy access to point the panels toward the sun twice a day (takes about 10 minutes) and to clean the panels from time to time (birds,dust,pollen-pollen is sticky,etc). I think this has helped our array power output in winter. The racks also allow me to point the panels down when thunderstorms threaten hail. I buried conduit and a hub (a buried bucket with provision for drainage and entry holes for conduit) to run wire pairs to each rack.

author: Kibi
author_rank: Unknown
timestamp: April 30, 2013, 05:56:46 pm
content: Quote from: Joules on April 30, 2013, 12:19:25 pmThis is precisely the point of me doing what I am doing now. I need to figure this solar system out for my needs, nobody else can really tell you what you do and don't need. It's a personal thing. I want to see what I can get with what I've got, modify some habits perhaps and decide what to do from there.Investing in all of this equipment makes sense to me and not just because the energy prices are going up. One day I'll need to retire and electricity is one of the few basic things I'll need. A pension is not going to help you, it will be worth nothing by the time you need it. You hear about elderly people not being able to afford to switch the heating on! It's a terrible way to live.My father's life savings were worth a roll toilet paper and his super duper pension plan amounted to the value a loaf of bread when it matured. I have therefore learned (the hard way) that these sort of investments can reap zero rewards as they are not based on anything substantial. The sun will be around for a fair bit, so I'd like to base some of my investment on that.When I'm old, I'll need energy, shelter and food. I can only trust myself and my family to provide these things. The banks and the government won't give two hoots whether I'm warm or not.

author: croberts
author_rank: Regular Contributor
timestamp: April 30, 2013, 06:12:22 pm
content: Well said Kibi and I 100% agree. The investment you've made is a sound one. Solar energy does work and can be made to work on a daily basis by adjusting habits. That doesn't have to mean hardship. Quite the opposite. The LED light we have now that comes from solar energy is much better than we had before, the touch switches we have now are better than the old toggle switches, and the lights remember to turn themselves off. Everything is better because we were willing to make a change.

author: Kibi
author_rank: Unknown
timestamp: April 30, 2013, 09:50:18 pm
content: I have got one 250W panel up this evening. It's night time now, so no generation, but tomorrow should be sunny.I switched the mains electricity off and the inverter is now running off the battery which was fully charged and floating via the inverter over the past two days.My Cosm feed has battery information on it if anyone is interested. I have not figured Modbus out yet, so there is no data on the charge controller as of yet.There are also some glitches that have started to appear on the graphs, I'm not sure what that's about, but the data is there.www.cosm.com/feeds/116608

author: Kibi
author_rank: Unknown
timestamp: May 03, 2013, 10:28:00 pm
content: Just a quick update.I have installed two panels so far. The are installed on Renusol flat roof mounting "bins". This is where the old battery packs came into good use. I have used them as ballast to weigh the Renusol bins down. The Renusol datasheet specifies 68Kg of ballast. Four of those battery packs is 72Kg and they are on a rubber roof which provides even more traction.The first panel had been up for less than 24 hours and a bird had already crapped on it. The second one lasted just over a day before being crapped on. There is no sign of any mess on the rest of the roof (ever), just the panels. How do the birds know?This work was done in the early evening when my site is unfortunately in shade.I should have time to put the other two up this weekend.

author: Kibi
author_rank: Unknown
timestamp: May 06, 2013, 05:47:57 pm
content: I have now completed the install. All four panels are up.All of the panels are tied to a dedicated earth rod via one of these cables. The second cable provides a ground reference for the SPD and also ties the charge controller to ground.

author: SeanB
author_rank: Super Contributor
timestamp: May 06, 2013, 06:01:34 pm
content: Nice work, good to use the grease on the earth rod as well, if you were higher and more exposed you would need a few more rods, but as there are trees higher than you all that has to do is dissipate static charge.

author: Kibi
author_rank: Unknown
timestamp: May 06, 2013, 06:10:42 pm
content: As soon as I find out where I lost my self amalgamating tape, that will go on too.Lightning shouldn't be too much of a problem, they don't make much of it around here, but it does happen. Besides, as you say, there are lots of trees.

author: SeanB
author_rank: Super Contributor
timestamp: May 06, 2013, 06:37:20 pm
content: Self amalgamating is good, otherwise a regular roll of 3M tape and a cable tie work well. Should last a few years in the shade. Just take a bag of rock salt ( you should get that on sale now in the UK) and work it into the soil directly around the electrode, and it will dramatically reduce ground resistance ( as well as make it rust a little faster and kill all the weeds in the direct vicinity for a years or two) for the system

author: Kibi
author_rank: Unknown
timestamp: May 06, 2013, 06:56:00 pm
content: I also forgot to mention that I have run the alarm cable through all of the panels then ending at the door contact.

author: croberts
author_rank: Regular Contributor
timestamp: May 06, 2013, 07:20:09 pm
content: Hello KibiThe installation looks great. I got some of my solar racks a bit too close to each other and in winter I get a tiny bit of self shading. I've attached a png of a quick drawing I did for your set up (I had to do some guessing on dimensions and sun elevation is for London) that might help you with that issue.

author: Kibi
author_rank: Unknown
timestamp: May 06, 2013, 07:30:21 pm
content: That's brilliant, thanks for that!This thought did occur to me, but only for a brief moment. As the "bins" are not fixed down, they can be moved about. They are about 75cm apart at the moment, but in the autumn I can check to see that the rear ones are not being shaded, assuming the sun shines at some point in winter.