Solar Panels?

4 Solar panels and salespeople that want sales

• So I find myself with 4 185 W Solar panels AND 4 enphase M190 Micro inverters (that onboard connect to each panel). The system from what I can tell is "made" for a grid connected solar system. Which is great but NOT what I want/need (Also I am too far from a station to qualify for microfit in Ontario). SO, I have been trying to make a solar island/charge station to at least provide a partial off-grid solution. Problem: Solar energy businesses seem to be the "new" tin-men and I am sick of "we will come give you a quote" which always ends up being $10K plus and is really just their own system installed with my four panels added on as an after thought. THEN doing research really just leads to either lists of equipment or really high level stuff like Solar->Charge Control->battery->inverter->save so not really helpful! I am handy enough and know enough to do it myself. Except some very simple "WHAT do I need equipment wise to make this come together. As stated I want to make a sort of island station in our house to run whatever we can from the station so it is not a "help me replace hydro" question. So Questions 1) In the non-grid tied world, CAN I use these micro inverters? if not so be it I can always e-bay them. If I can how would it look? I can see doing Panel->Micro Inverters->Battery charger->battery->INVERTER!->Power... but um that seems stupid(or tell me different?) 2) Regardless; How many batteries should I get? 3) Inverter and charger recommendations? Other info that might help in my quest: I would like to add panels in time at least up to 8. I can literally disconnect my house from the grid and plug in using a 240 North American plug to power my whole house and have had to with our back up genny this intrigues me. I have LOTS of places to put the panels and would even one day like to add a tracker

• Answer:

  1. As a general rule, you can't use the micro-inverters if the grid is down (or you're disconnected from it). Be aware that I'm not familiar with the M190s and this isn't a 100% rule. Generally component sizing and anti-islanding behavior prevents using them without a grid: imagine the powerline in the neighborhood gets cut and your inverters keep feeding power back into the grid, keeping it hot -- the serviceperson is going to get a shock from a line they thought was dead, etc. Grid-tie microinverters like you have are supposed to detect grid disconnection and take themselves offline if there's no grid power. Off-grid (and some stand-alone grid-tie) inverters do not do this, and that's what you want. 2. Battery sizing is absolutely impossible to do without knowing what you need to run and how long you need to run them for. Running a TV overnight is entirely different from running a refrigerator + lights + computer + fans + well pump for a week because it's really rainy out. There are a lot of online calculators that will walk you through "loads I want to run + for how long worst-case" sorts of steps. The number of watts of panel you have will limit your total loading (you can't use more power in a year than you produce), but the number of batteries will determine how long you can ride out dark times. Let's say you have 300 W of load on all the time and need to be able to survive a week of no charging: 300 W * 24 h == 7200 Wh. Let's say you use some 12 V batteries: 7200 Wh / 12 V == 600 Ah. For reference, a typical car battery (not what I'd use) is about 40 Ah. 3. I work for a company that makes some of the involved hardware, so I can't ethically make recommendations. Remember that, with power electronics, you generally get what you pay for up to some "knee" in the cost curve. (Think: Lada vs. Honda vs. Bentley.) Avoid going cheap cheap if you can't stand the system breaking when you need it. You're also going to need to buy some "BOS" (balance of sale) stuff: circuit breakers, switches, conduit and boxes, etc. Wiring up a system safely and to code takes a good bit of research, but lots of people have done it before you. If this sounds like there's a lot of research and experience and some math involved, it's because there is. I'm very sorry that you've only experienced the charlatans so far. If you don't want to / can't do all this figuring, you need a professional and I highly recommend talking to people on some off-grid solar power fora. Off-grid solar people are generally about 95% less profit-motivated than the hot-new-industry grid-tie solar people. They're often green energy evangelists who were doing this before it was popular. You may be able to get free help on fora if you're willing to wade through the wastrels; you may also find the names of some companies that people trust to do good, honest work. Optional #4: adding panels later to increase your power input isn't hard. You can run (almost all) charge controllers in parallel. (That is, 6 panels on one charge controller wired to the battery bank, 6 different panels on another charge controller wired to the same bank, etc.) The battery input voltage is so resistant to change moment-to-moment that each charger has no idea the others are out there also charging the battery. It may be cheaper for you to buy one bigger charge controller capable of doing 8 panels now, or it may be cheaper for you to buy a small one now and a second small one later. Similarly, adding batteries isn't hard. Getting more inverter capacity, however, is. Size your loads up-front! Optional #5: Trackers are generally a mug's game. Unless you're space-limited or playing games with your electric rate plan, just putting more panels down is more efficient than a tracker system. (When panels were very expensive per watt, this was less true.)