paranoia
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Post by paranoia on May 22, 2017 19:39:55 GMT 10
Well tax time is coming up and something that has been on my list for a while is solar. I'm hoping there are a few out there with a bit of knowledge in the matter.
I've experienced both full off grid and grid tie, both have benefits, but I've been wondering about hybrid systems.
What I'm basically after is a grid tie with the ability to power my house for short periods as well as utilise the production of the panels whilst the grid is down. What I was initially thinking was running two inverters side by side with switching capability... but then I discovered 'AC coupling inverters'.
It looks like you can feed into the grid, utilise the solar power whilst grid is down along with small battery storage to compensate for extra use or night time.
Does anyone have any experience with these hybrid systems?
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Deleted
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Post by Deleted on May 22, 2017 23:31:50 GMT 10
Hi, The place to start when looking at going off grid, is to figure out just how much power you need or what you expect to run from your power system, naturally that is going to impact the price. I would suggest you do a list, or energy audit and decide how big your system has to be as a first step.
I keep my ear to the ground on the latest battery news, and word is in the industry is that the Lithium batteries are not as good as the sales men tells us. Flow batteries are ideal but not at current prices, which leaves the good old lead acid. Once you get to the point of knowing how much power you want, ten it is time to look at battery prices....It is normal to consider the possibility of five days of cloud during winter in thinking about battery capacity. I would recommend a 48Volt system as it keeps the amperage less than 12 or 24 volt systems which helps reduce losses in the way of voltage drop. It is important you compare prices to the deep of discharge (DOD) cycle life on the batteries. ..........Some lead acid batteries banks if you were to drain two thirds of their power each night and recharge them the next day they would not last twelve months. While other battery banks if you make them over size and only draw them down only one third per day and recharge them daily, will last ten years or more. So their is a lot to consider and compare in selecting the right batteries to buy.
Now days there are a few combination MPPT solar regulator/charger/grid tie/stand alone unit, that will do it all, and the prices are good compared with buying discrete components. Knowing how much power you want will be the starting point for looking at these. ( I would suggest browsing ebay for an idea of prices and what you can expect).
The options now days is for anything in size from just being able to run a high out put LED globe and phone charger, and feeding the excess power to the grid after the battery is charged, all up costing a couple of hundred dollars. Through to systems running all electric homes including air conditioning and refrigeration costing up around 40K.
I hope this is the sort of information you wanted.
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token
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Post by token on May 23, 2017 19:17:30 GMT 10
I do know a bit about it. But i also know someone who 'might' be able to set you up if your serious. He is my electrician. He lives off grid, and is registered to do such, and is a mate. Very capable and trustworthy. Problem is, he doesnt need the work. Ill chase it for you, but it wont be 40k, not even close! Think a lot lower, and 48 volt too.
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blueshoes
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Post by blueshoes on May 23, 2017 22:40:35 GMT 10
Following with interest
I don't get why all inverters don't just continue to power the house if the grid goes down -and then re-sync and rejoin automatically if it comes back up ...
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paranoia
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Post by paranoia on May 23, 2017 23:56:20 GMT 10
Following with interest I don't get why all inverters don't just continue to power the house if the grid goes down -and then re-sync and rejoin automatically if it comes back up ... I'm no electrical engineer but I'll share my limited understanding.
The function of an inverter is to change the direct current received from the panels into alternating current usable by your appliances. In order for a grid tied inverter to power your appliances during all environments (low sun, high sun) it needs grid to supplement it or feed extra into the grid that isn't needed. To do this the AC needs to be phase matched to the power in the grid (positive and negative switches at the same time).
Most electronics (particularly around power manipulation) are not like computers, they're designed for a very specific function. In order to make a mini-grid or 'island' your inverter you need a different circuit. You either buy two inverters or in these new ones they have more circuits within the same box with a microcontroller to decide when to switch between the two circuits. It's also harder to completely generate the signal from scratch and you need something to smooth out the peaks in usage and the dips in the production from the panels.
You can use batteries for this, but you now need a charging circuit also.
To quote geek: "Now days there are a few combination MPPT solar regulator/charger/grid tie/stand alone unit, that will do it all". If you open the inverter boxes there will be a few different modules/circuits inside to perform the different functions and a microcontroller that switches between everything. These are obviously going to be more expensive and complexity leads to weakness unless you pay big $$$.
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paranoia
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Post by paranoia on May 24, 2017 0:20:44 GMT 10
Hi, The place to start when looking at going off grid, is to figure out just how much power you need or what you expect to run from your power system, naturally that is going to impact the price. I would suggest you do a list, or energy audit and decide how big your system has to be as a first step. I keep my ear to the ground on the latest battery news, and word is in the industry is that the Lithium batteries are not as good as the sales men tells us. Flow batteries are ideal but not at current prices, which leaves the good old lead acid. Once you get to the point of knowing how much power you want, ten it is time to look at battery prices....It is normal to consider the possibility of five days of cloud during winter in thinking about battery capacity. I would recommend a 48Volt system as it keeps the amperage less than 12 or 24 volt systems which helps reduce losses in the way of voltage drop. It is important you compare prices to the deep of discharge (DOD) cycle life on the batteries. ..........Some lead acid batteries banks if you were to drain two thirds of their power each night and recharge them the next day they would not last twelve months. While other battery banks if you make them over size and only draw them down only one third per day and recharge them daily, will last ten years or more. So their is a lot to consider and compare in selecting the right batteries to buy. Now days there are a few combination MPPT solar regulator/charger/grid tie/stand alone unit, that will do it all, and the prices are good compared with buying discrete components. Knowing how much power you want will be the starting point for looking at these. ( I would suggest browsing ebay for an idea of prices and what you can expect). The options now days is for anything in size from just being able to run a high out put LED globe and phone charger, and feeding the excess power to the grid after the battery is charged, all up costing a couple of hundred dollars. Through to systems running all electric homes including air conditioning and refrigeration costing up around 40K. I hope this is the sort of information you wanted.
Thanks for weighing in.
I have absolutely no intention of 'going off grid' completely, I've been there done that and its not worth the hassle if you have grid available in my opinion.
I definitely agree with your assessment on lithium batteries, they seem scoped for weight & energy density, both useless parameters for the application of house battery. I'm yet to see a solution outperform led-acid for the price, yes there's venting, yes they're heavy... both are easily overcome in a home situation.
To my system specifically, 5 days is WAYYY overkill for what I have in mind. My initial intention for solar was to reduce my power bills, I had 2kw simple grid tie on my last house and was very happy with the results. The ability for the inverter to power disconnected from the grid, giving me the option to keep the fridge/freezer running and the water pressure pump functioning is all I really need to keep going. I'm considering the possibility of adding a very small battery (no bigger than 5kwh) backup system to increase overall system stability.
In order for the battery storage to be viable it needs to be price competitive to the installation of medium sized backup generator. It might end up the appropriate system for me is a grid tie system + generator, but all options need to be explored/costed before I make the move.
Do you have any experience with these MPPT system inverters? I'm always sceptical of things such as inverters performing multiple functions and putting all your eggs in one basket. I mentioned the off grid system we had for a while, it the early days we had problems with inverters and ended up with multiple smaller inverters, charge controllers, timers ect...
What I'm really trying to work out with this thread is; Is a hybrid grid/bank system viable & reliable? or are you better off having two separate systems with switching capability?
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paranoia
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Email: para@ausprep.org
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Post by paranoia on May 24, 2017 0:22:36 GMT 10
I do know a bit about it. But i also know someone who 'might' be able to set you up if your serious. He is my electrician. He lives off grid, and is registered to do such, and is a mate. Very capable and trustworthy. Problem is, he doesnt need the work. Ill chase it for you, but it wont be 40k, not even close! Think a lot lower, and 48 volt too. Thanks for the referral, I'll talk to you in PM.
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token
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Post by token on May 24, 2017 7:37:45 GMT 10
Following with interest I don't get why all inverters don't just continue to power the house if the grid goes down -and then re-sync and rejoin automatically if it comes back up ... There are various different inverters. Grid tied inverters generally need to register 'mains' power to work. Add a battery to trick it and viola. Add an adapter to route the excess power to a battery bank instead of the grid and store your excess energy. Then add a switch to your box and manually flick it on when the sun goes down to draw from your BB. That way you only pay your connection fee each month IF you have enough panels, batteries and an inverter size to suit, and live within your power means. One hybrid back to grid system now turned into full off grid.
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Deleted
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Post by Deleted on May 26, 2017 15:57:40 GMT 10
Hi Guys, I see there are some questions being raised, about understanding various inverters.
When you have an inverter that connects to a battery which is DC, it switches the power on and off very fast to make AC (Alternating Current) power, the same as we get from our normal power points. There are two types of these inverters; ones that make a sin wave output and ones that produce what is called a modified sine wave output. The sine wave inverters cost more, but anything that runs on normal 230VAC will run very well off them. The modified sin wave inverters are cheaper and maybe by there simplicity a little more robust, but some appliances don't like running from them and they may make buzzing sounds in your TV sound systems and radios. Both the sine wave and modified sine wave inverters as I mentioned have to switch the power on and off to make AC and that means they generally have a quartz crystal oscillator circuit (a bit of electronics to act as a fast timer) that gives them the signals to switch on and off.
Because the power grid is gets its power from mostly spinning generators as the load increases they get harder to turn and that causes their speed to drop and results in a frequency drop just a tiny amount, after that happens then the engine/prime mover governor reacts to the drop in frequency and speeds things up and back to fifty cycles per second again. Meaning the power grid fifty Hz is not always exactly 50Hz. Since inverters with their own clock circuits don't alter the speed of their clocks from fifty cycles per second, if they were connected to the grid power then at some point the inverter would be putting out positive when the grid would have wanted it to being putting out negative and in a fight with the National power grid your inverter normally looses... RIP inverter!
The grid connected inverters solve the problem by using the grid power to provide the timing signals to tell it's electronics when to switch on and off. But that means when the grid fails the inverter stops working since they no longer get the timing signal from the failed power grid.
The type of inverter that can be grid connected and work when the grid fails is actually a box with both inverters inside it, they use relays to switch from one to the other as required. By selling them as a package the manufacturer can offer them generally at a lower price than you could purchase individual items for.
I mentioned in my last posting on this that the flow batteries Zinc Bromide were showing promise but presently too expensive, it not turns out that they have to be drained flat every two weeks to stop dendrite formation..... A small fact that has not appeared in any of their promotional information. So the old lead acid seem still a good buy. If your not going to cycle the batteries on a daily basis there are some good cheap battery banks on ebay that would give good standby service life.
There should be a number of Hybrid inverter charges on ebay that do both functions of the inverters while acting as an Uninterruptible Power Supply (U.P.S.) as well as a battery charger. a 4kw Hybrid for $1520 make MPP Solar...... sine wave output.... designed for 48Volt battery bank.
happy prepping
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blueshoes
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Post by blueshoes on May 26, 2017 23:55:20 GMT 10
Dunno why it didnt make sense the other five times someone explained it but the penny finally dropped - thankyou @geek
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