A Hybrid system that can switch between using power from Solar panels and the Grid

[Maitland Gill]

A Grid Assisted Uninterruptible Power Supply (UPS) that can use the power from a wall socket as it's alternative power supply.

A Solar system that can provide power to run a device, but automatically switch between using power from a wall socket. This is for when the Solar power is insufficient and could be a cheaper option than spending about $5,000 to install a Grid-Tied system.

There are systems called Plug and Play solar panels, but these sound too risky. I don't want to fry a worker in case the power goes out. Instead, I want to try making a Grid-Assisted system that would automatically switch between Solar and Grid.

I think I have an idea on how it could work:

A Solar panel is connected to a Charge Controller (Solar Controller), which supplies the correct amount of current to a Battery.

An Inverter also connects to the battery and uses its current to produce AC (The higher Voltages and Amps required) for the device. When the battery is fully charged, it can be used as part of a circuit. Because any excess energy will be passed through to another 'Load'.

The charging source needs to provide a Voltage that's greater than the batteries, so the current can effectively flow through it. If the Solar panel doesn't produce enough power, then we'll need a way for the circuit to automatically switch over to the Mains (The Grid) and back again. If the battery drops below 50% of its total charge, it'll become damaged.

To counter this, perhaps the Solar energy could be passed through an Uninterruptible Power Supply (UPS), which may be able to detect whether the battery has 51% of its charge left. At this point, it'll provide an alternative power source, being the wall socket (The Grid).

For the UPS to switch back into using Solar power, it'll need to also detect when the battery has regained a specific amount of its charge (98% for example). This amount would be a balance between how many times it needs to recharge and the loss of efficiency this causes.

A UPS provides emergency power to a load when the first input power source fails. The goal here is to make the battery into the primary source of power and use the Wall Socket as the alternative.

This only works if the cost is less than what it would be if you were to install a Grid Tied system to your Fusebox. In Australia, this would be about $5,000. A typical UPS includes an Inverter, Battery and Charger Controller. However, there are UPS's that use external Batteries. http://www.powerstream.com/inFAQ.htm

When the battery is supplies the electricity, the UPS will need to convert that current into AC with a correct amount of Amps. To do this, the UPS will need a Transformer (I think). http://wikitravel.org/en/Electrical_systems

What would I need for such a system?

I've heard that an AC Transfer Switch can switch between the Inverter and Grid.

Examples of such a system:
1. http://josh.com/Solar/
2. http://www.mro-tek.com/energy_products/charger1.html
3. http://www.jaycar.com.au/products_up..._Flier_JAU.pdf
4. http://avi-products.com/AviSolarInverters.aspx

Forum threads that talk about this topic:
1. http://forums.whirlpool.net.au/archive/1736320
2. http://www.solarpaneltalk.com/showth...d-installation

Website pages I've come across:
1. http://www.wholesalesolar.com/grid-assist.html
2. http://www.solargreen.net.au/blog/gr...ed-electricity
3. http://www.renewablesinternational.n...150/452/72715/
4. http://fylz.com/grid-assisted-electricity
5. MPPT vs PWM: http://enerdrive.com.au/mppt-vs-pwm-solar-controllers/
6. What is a Charge Controller?: http://www.blueskyenergyinc.com/revi...rge_controller
7. AC to DC calculator: http://www.batterystuff.com/kb/tools...-inverter.html
8. About Batteries: http://www.mkbattery.com/content_con...-reference-faq

[Amy@altE]

Samlex America makes a small device that does all of that. http://www.samlexamerica.com/product...l.aspx?pid=101

It has a small solar charge controller, an AC charger, a 1500W inverter, and an auto transfer switch. So it can act as a self powering UPS.

It won't run much, but it will handle a few items.

[Mike90250]

The Xantrex / Schneider XW series does most of that. It acts like a giant UPS for your house (well, it's transfer switches are good for 60Amps, your house is likely wired for 100A or more) It just needs batteries, and will charge them from the grid, when the grid goes down, the relay clicks and you are on inverter power for as long as the batteries last.

You can add PV panels & solar charge controller, or any other method you devise to keep the batteries charged.

[sensij]

Samlex America makes a small device that does all of that. http://www.samlexamerica.com/product...l.aspx?pid=101

It has a small solar charge controller, an AC charger, a 1500W inverter, and an auto transfer switch. So it can act as a self powering UPS.

It won't run much, but it will handle a few items.

Neat product from Meanwell. I'd have to look more closely at the battery capacity, but it appears to compete favorably with something like SMA's SPS, which only supplies power when the sun is out. For those who refuse to consider a generator, but want to access power from their grid-tied panels in the event of a grid failure, something like this could fit more easily into a budget than other options. Not compatible with a SolarEdge or Enphase system, though.

[SunEagle]

Samlex America makes a small device that does all of that. http://www.samlexamerica.com/product...l.aspx?pid=101

It has a small solar charge controller, an AC charger, a 1500W inverter, and an auto transfer switch. So it can act as a self powering UPS.

It won't run much, but it will handle a few items.

Interesting item. Although it is just a big UPS system with external batteries that can be dedicated to a single or a couple of small electric loads.

I didn't see a cost but it might be worth while as a small backup system for a "critical load" if it is matched to a decent battery system. At least you could use good Deep Cycle batteries instead of the normal AGM batteries found inside most UPS boxes.

[Amy@altE]

Interesting item. Although it is just a big UPS system with external batteries that can be dedicated to a single or a couple of small electric loads.

I didn't see a cost but it might be worth while as a small backup system for a "critical load" if it is matched to a decent battery system. At least you could use good Deep Cycle batteries instead of the normal AGM batteries found inside most UPS boxes.

$765. As you said, I like that it gives you the freedom to use a quality battery of your choice for a UPS. It is small, the solar charge controller is just PWM 12V 30A, but it's a cool product. We don't sell many of them at all, but if you are trying to build your own UPS, the price is about right. Charge controller $120 + inverter $500 + auto transfer switch $190 = $810.

[SunEagle]

$765. As you said, I like that it gives you the freedom to use a quality battery of your choice for a UPS. It is small, the solar charge controller is just PWM 12V 30A, but it's a cool product. We don't sell many of them at all, but if you are trying to build your own UPS, the price is about right. Charge controller $120 + inverter $500 + auto transfer switch $190 = $810.

I did not read the technical data but is there a way to disable the "charging" feature and just use the "transfer switch" component if you already had a good solar MPPT CC for your battery system?

The idea of a pure sine wave inverter with instant transfer between grid and battery is very appealing but with only 30A CC capacity you would be limited to the size of the battery system.

[Amy@altE]

I did not read the technical data but is there a way to disable the "charging" feature and just use the "transfer switch" component if you already had a good solar MPPT CC for your battery system?

The idea of a pure sine wave inverter with instant transfer between grid and battery is very appealing but with only 30A CC capacity you would be limited to the size of the battery system.

Agreed, which is why we don't sell a lot of them. They've got others without the charge controller built in, but this one has a lot of configurability that I like, it can set priority on using grid or battery. Just not connecting the solar to that connection and using an external one will accomplish that.

They've got the ST-1500-112 with Pure sine wave and 25A transfer switch for $615. http://samlexamerica.com/documents/p...414%20Lrez.pdf . It meets UL Standard UL-458 (pending listing), so it is designed for mobile use, not home.

[tasman]

If you have a grid connect system, wouldn't it be easier to use a 240v battery charger during the day for your battery pack and at night, switch over to battery power via an inverter. Pretty cheap and it would overcome the hassle of spending more money. That way you get the return income from the grid and no bills.

I know someone who does that, they had an electrician connect a generator to the house for when they had grid power failures, which are often where they live. When they got their grid connect system, the same electrician came and wired their inverter to the generator power board, now they charge their batteries during the day from a power point and at night, switch to battery.

Seems to work really well for them, except they have had the power company arrive to check their grid system because of their lack of power use a couple of times and accepted that they only switched to the generator during grid power failures. The dumb power company electricians didn't have a clue about the wired inverter and thought it was part of the generator system. If you have a grid connect system, wouldn't it be easier to use a 240v battery charger during the day for your battery pack and at night, switch over to battery power via an inverter. Pretty cheap and it would overcome the hassle of spending more money. That way you get the return income from the grid and no bills.

I know someone who does that, they had an electrician connect a generator to the house for when they had grid power failures, which are often where they live. When they got their grid connect system, the same electrician came and wired their inverter to the generator power board, now they charge their batteries during the day from a power point and at night, switch to battery.

Seems to work really well for them, except they have had the power company arrive to check their grid system because of their lack of power use a couple of times and accepted that they only switched to the generator during grid power failures. The dumb power company electricians didn't have a clue about the wired inverter and thought it was part of the generator system.

[russ]

Seems to work really well for them, except they have had the power company arrive to check their grid system because of their lack of power use a couple of times and accepted that they only switched to the generator during grid power failures. The dumb power company electricians didn't have a clue about the wired inverter and thought it was part of the generator system.

Really a bit stupid - if the power company ever figures out what is going on they have every right to pull the plug.

Do things right and don't cheat!

Your friends are the dumb ones.

[SunEagle]

Really a bit stupid - if the power company ever figures out what is going on they have every right to pull the plug.

Do things right and don't cheat!

Your friends are the dumb ones.

Not only are his friends looking for trouble, they are actually spending more money using batteries (the most costly) to supply their power instead of either that generator or the grid.

Maybe they will figure it out when they have to replace that battery bank.

[tasman]

Not only are his friends looking for trouble, they are actually spending more money using batteries (the most costly) to supply their power instead of either that generator or the grid.

Maybe they will figure it out when they have to replace that battery bank.

Not dumb or illegal, they are not contracted to have to use grid power, I've read it and it's about them supplying energy to the grid. They are getting an income from it, which according to them will pay off their system within the next couple of years, as they've had it for a couple of years now. Of course the power company may cut off their power, but according to the laws they have to provide a connection to anyone who pays their bills. Can't uinderstand why so many support the rich corporate world of using the law to their advantage to rip everyone off, but frown on those who use it to give the corporate world some of their own medicine.

Their batteries are lifepo4, should last decades considering they rarely get below 70%. We have very expensive electricity down here, so It's logical to use the generator on veggie oil which they source from local takeaways for their workshop requirements. They have very few times when they have no sun for more than a couple of days, so it's a long term guarantee of energy supply with excellent back ups and energy security.

They control their entire energy system through an old 256meg RAM x 10gig laptop running linux, the bloke designed and build the program himself, way out of my understanding but it works and controls lights and energy use around the home, very efficiently.

Why run a generator which requires lots of maintenance, wears out, emits lots of pollution and noise, or the grid where you have to pay for your energy when you already have it free. Doing the right thing is providing a secure reliable and cheap energy system for your families future, not supporting rip off profit making ideological elites and increasing their profit margins and bank balances at the expense of everyone elses life style. If people did the right thing, these rich morons would make just enough to have good lives, then reduce their profit margins and aid the huge amount of people struggling to survive in this rip of age of idelogical elitism.

This is the 21st century, not the 19th, just the same with everything, if you stick with past approaches, you end up with past outcomes.

[pleppik]

If you have a grid connect system, wouldn't it be easier to use a 240v battery charger during the day for your battery pack and at night, switch over to battery power via an inverter. Pretty cheap and it would overcome the hassle of spending more money. That way you get the return income from the grid and no bills.

I know someone who does that, they had an electrician connect a generator to the house for when they had grid power failures, which are often where they live. When they got their grid connect system, the same electrician came and wired their inverter to the generator power board, now they charge their batteries during the day from a power point and at night, switch to battery.

Seems to work really well for them, except they have had the power company arrive to check their grid system because of their lack of power use a couple of times and accepted that they only switched to the generator during grid power failures. The dumb power company electricians didn't have a clue about the wired inverter and thought it was part of the generator system. If you have a grid connect system, wouldn't it be easier to use a 240v battery charger during the day for your battery pack and at night, switch over to battery power via an inverter. Pretty cheap and it would overcome the hassle of spending more money. That way you get the return income from the grid and no bills.

I know someone who does that, they had an electrician connect a generator to the house for when they had grid power failures, which are often where they live. When they got their grid connect system, the same electrician came and wired their inverter to the generator power board, now they charge their batteries during the day from a power point and at night, switch to battery.

Let me see if I'm following this: they have a generator, plus grid-tied solar panels, plus batteries. During the day the solar power feeds AC to the grid, and the batteries are charged during the daytime using AC from the grid. At night the inverter runs off the batteries, or you switch to the generator when the grid goes down.

This seems terribly complicated to me, and I'm not clear what the benefit is. You don't say where this system is located, so I suppose if grid power is super-expensive it might make sense. But if grid power is that expensive and you've got batteries and a generator and solar panels, why not just go off-grid?

[SunEagle]

Not dumb or illegal, they are not contracted to have to use grid power, I've read it and it's about them supplying energy to the grid. They are getting an income from it, which according to them will pay off their system within the next couple of years, as they've had it for a couple of years now. Of course the power company may cut off their power, but according to the laws they have to provide a connection to anyone who pays their bills. Can't uinderstand why so many support the rich corporate world of using the law to their advantage to rip everyone off, but frown on those who use it to give the corporate world some of their own medicine.

Their batteries are lifepo4, should last decades considering they rarely get below 70%. We have very expensive electricity down here, so It's logical to use the generator on veggie oil which they source from local takeaways for their workshop requirements. They have very few times when they have no sun for more than a couple of days, so it's a long term guarantee of energy supply with excellent back ups and energy security.

They control their entire energy system through an old 256meg RAM x 10gig laptop running linux, the bloke designed and build the program himself, way out of my understanding but it works and controls lights and energy use around the home, very efficiently.

Why run a generator which requires lots of maintenance, wears out, emits lots of pollution and noise, or the grid where you have to pay for your energy when you already have it free. Doing the right thing is providing a secure reliable and cheap energy system for your families future, not supporting rip off profit making ideological elites and increasing their profit margins and bank balances at the expense of everyone elses life style. If people did the right thing, these rich morons would make just enough to have good lives, then reduce their profit margins and aid the huge amount of people struggling to survive in this rip of age of idelogical elitism.

This is the 21st century, not the 19th, just the same with everything, if you stick with past approaches, you end up with past outcomes.

Yes this is the 21st century. What I am saying is your estimation that is costs less to generate power with batteries then purchasing it from the greedy power company is wrong unless where you live the electric rates are more than $1/kWh.

So do the math and add up what it cost to purchase the solar panels, batteries, chargers, inverter, wires, fuses, etc. and then estimate the lifetime (about 7 to 9 years but not decades) kWh generation from those batteries. Divide that kWh generation value into what was spent and you will end up with a figure over $1/kWh.

Just about anywhere in the world you will be paying more to generate from batteries then buying from the Utility. Even with the cost of fuel being high, using a generator efficiently will end up costing less to generate a kWh then using batteries.

Also think about using that great software your friend designed that will help you efficiently use the power you purchase. That will save money without the need to purchase batteries.

[Maitland Gill]

The Xantrex / Schneider XW series does most of that. It acts like a giant UPS for your house (well, it's transfer switches are good for 60Amps, your house is likely wired for 100A or more) It just needs batteries, and will charge them from the grid, when the grid goes down, the relay clicks and you are on inverter power for as long as the batteries last.

You can add PV panels & solar charge controller, or any other method you devise to keep the batteries charged.

Being able to produce our own electricity, allows us to reduce our power bill. The amount we save from this, can be used to expand our system. So the sooner we can start doing this, the faster we can become self-sufficient. Rather than wait until we can afford to install an Inverter to our Fusebox, what if we used a Grid-Assisted Uninterruptible power Supply (UPS), that can automatically switch to using power from a wall socket (The Grid). This is for when the Solar panels don't provide enough current and require an alternative power supply.

When you're ready to make changes to the Fusebox, the equipment that makes up a UPS can be used to supply power to the entire house. In Australia, the cost of replacing a switchboard is about $700. New circuits and having to rewire cables could bring this up to $5,000 [Home Improvement Pages - How much does it cost to replace a switchboard].

So I need to find a product (Inverter/Charger) that can:

1. Detect the amount of charge within a battery and switch over to an alternative power supply (The Grid through a wall socket) when the battery has been half depleted (Or drains to a level of you're choosing).

2. While the power from the house is being utilized (The grid), the device continues to power the product while also using Solar (When available) to recharge the batteries.

3. When the battery regains a percentage of it's charge, the device needs to switch back to using Solar as it's primary input source. This way, even if the Solar panels don't generate as much power as what's being consumed, the energy that had accumulated during the day, can still be used to run the appliance for a while.

4. The device will need to convert the DC to 240 Volts AC.

5. There needs to be a way in which an AS/NZS 3112 (Type I) can draw AC current from the output.

I know my demands are complex, but it seems so much more convenient than having to install a Grid-tier system to you're Fusebox.
For smaller applications (Bar fridge, Air-conditioner), the cost and reliability of such a system would help make Solar more accessible.