The use of batteries

System

Hi guys,

I'm trying to understand what the solar generation work, I'm new.
I'm an electrical engineer (jr) so it was very obvious to me, that's what I thought.
Solar Panels + charger + batteries + inverter and the controller: free electricity
But now I saw some videos on youtube where they use only two elements: Solar panels and the inverter witch is connected to the main electricity counter. This way we don't need any bateries, the controller and the rest. It is very simple, less expensive.

So my question is what is the advantages and disadvantages of 1st method vs the other? Do I miss anything?
What is the reason to store the energy to the batteries when we can sell/buy the electricity?

Thank you

peterako

Re: The use of batteries

Hi there,

First there is off grid. You need battery's, charging needs energy so you are loosing some energy here plus battery's are expensive.

second there is on grid you feed back to the grid to compensate your e-bill. but when there is a power cut your system is switched off it is a slave from the grid. the grid is always master.
To avoid this there is on grid plus battery backup.

i hoop this helps to explain.
Greetings from Greece

BB.

Re: The use of batteries

The second method is called Utility Interactive or Grid Tied Inverter...

The GT Inverter takes all of the power the solar panels can generate (depending on sun, position, weather) and pumps it out, typically, as 240 VAC60Hz (for north America) power into the home/business AC wiring.

If the home is using more power than the GT inverter generates, then the utility line makes up the difference.

If the GT Inverter produces more power than the home needs, then the extra power is pushed out to the utility...

The Grid Tied Inverter acts like a "generator" and the utility acts like an AC "battery". The GT Inverter follows the voltage/frequency of the AC Mains. And turns off if voltage/frequency is out of range (and waits 5 minutes before trying to "reconnect").

In the US, many states have passed laws that require the utility kWatt*Hour meter to run forwards and backwards... This is called Net Metering... I either pay for the power I use at the end of the month, or I get a credit in my bill that I can use any time over the next 1 year period. At the end of 1 year, if there is "extra money" in my account, it is set to "Zero" (I cannot make money selling power at retail price to the utility). There are many rate/metering plans in the US--some are very good (for the consumer) and some are not (treat the Solar GT customer just like any other utility power source and pay only about 25-50% of retail power rate to the "consumer").

The GT system is a really nice system... No cost of batteries, and no extra power losses for voltage conversion.

Overall, the GT system is ~77% efficient (solar panel to GT Inverter to AC power). An Off-Grid system is ~52% efficient (solar panel to charge controller to battery to AC inverter to AC power).

However, if you have an AC Mains (Utility) Power Failure, the GT Inverter turns off for safety (do not electrocute the Utility Lineman or try an power the rest of the homes in the neighborhood).

There is also a Hybrid type system... Does both Off-Grid (battery backup) and Grid Tied power. Runs like Grid Tied system when the AC Mains/Utility power is working (more efficient). If AC Mains fail, switches over (internal transfer switch) into an Off-Grid system (emergency backup). You can read about Xantrex's hybrid system on their website.

To give you an idea of the costs for power using the different systems (in the US, very rough estimates, before state/US rebates and tax credits which can reduce costs by ~30%-50%--depending on state/local region):

Utility Power: $0.10-$0.30 per kWhr
Grid Tied Solar: $0.20-$0.30 per kWhr
Off Grid Solar: $1.00-$2.00 per kWhr

Questions?

-Bill

System2

Re: The use of batteries

Thank you for the reply Bill and peterako.

It is very interesting what you are saying. 77%!!!! compare to 52% it's crazy.
Seriously, I don't see any real advantage of installing a off-grid system.

Being honest with you here in Quebec (Canada) they are very reliable with electricity distribution. We almost never get off power.
Other thing the electricity cost is the cheapest in the world: 5.6-9 cents per kWh.
But since we have a very cold winter we use a huge amount of energy in heating and even if it is cheap at the end the bill is impressive. 1500$ / year.
Just to give you an idea I pay 40$/month in the summer and about 200$/month during the winter.
So it is two different realities here and in the US.
I have to sit down and analyze the costs of a solar system.
The solar panels are very expensive. I heard they made new ones 1$/W. Can't wait them being available on the market.
There is some DVD available (earth4energy) witch shows you how to make your own panels, but I'm not sure if they are worth to buy.

Thank you

BB.

Re: The use of batteries

earth4enegy is, at best, probably a waste of money. At worse, a multilevel marketing scam.

$1 per watt solar panels... Not yet. In the US you can find panels for $3-$5 per watt... A Solar Grid Tied system is probably around $8 per watt installed (including permits).

Money wise--Conservation and energy efficient appliances are the way to go. Perhaps, in your area a ground sourced heat pump (wells or buried pipe in ground for heat exchanger) may save some money (at the expense of a very costly install).

I keep looking at the Heat Recovery Ventilators--my wife really likes fresh air--and hot/cold weather get uncomfortable/expensive to waste the conditioned air.

I agree with you about Grid Tied Solar as being the better option for most people... The last time we had a power failure that lasted more than 24 hours was fifty years ago. I just have a small/quiet 1,600 watt generator for the rare (I hope) emergency power needs.

-Bill

Windsun

Re: The use of batteries

pitskalov wrote: »

Thank you for the reply Bill and peterako.

It is very interesting what you are saying. 77%!!!! compare to 52% it's crazy.
Seriously, I don't see any real advantage of installing a off-grid system.

If you have no grid power available, then you don't have much choice unless you want to run a generator full time.

The $1 a watt solar panels are still a myth - and even there, the $1/watt figure was for mass production costs of just the cells/film - not the frames etc., and not the selling price.

BB.

Re: The use of batteries

I should also add that Shipping and Handling is not cheap either. $1,000 thin "glass" in metal frame at a good price 1/2 way across the country may not compare to a local supplier with a (somewhat more expensive) panel in stock that you can put in the back of your truck/van.

Long distance shipping costs (for larger panels) may not become practical unless you are buying multiple units (WindSun makes their living at this--just an uninformed opinion from me).

-Bill

peterako

Re: The use of batteries

In my case i have voltage lines above my ground and below but for connecting me the power company has the problem that the two lines are running 100%.
So for me i had to pay for high voltage lines, transformer and low voltage lines.:grr ( yes i am living in grazy Greece )Plus here in Greece you pay also the city tax in your energy bill. and by law i can not pay my city tax:D . because i am off grid in my new house. this summer i double my battery bank plus i put more solar panels and i have a normal house running off grid.

Greetings from Greece