Solar Grid-Tie Systems

[John_Koorn]

Hi All,

I've started this thread as a general discussion on solar grid-tie systems. I'd like people who either have a system installed to comment on what they have, how they are finding it and how well it's working or perhaps it's not working as you expected it to.

Also, people who are thinking of installing a solar grid-tie system can come here for more information or ask questions.

John K.

[John_Koorn]

I'll start off the discussion with the system I recently had installed.

I took advantage of a special offer that was advertised for a 1.6kW system. This system has 8 x 24v 200w panels that are connected to a grid-tie inverter that's capable of handling up to 3kW. According to the specs and my location (near Melbourne, Australia - 37 degrees S, 144 degrees E) I can generate an average of 5.5kWh per day. In the future I could add another 8 panels to double the output before I need to upgrade the inverter.

This system cost around $1,900 fully installed by a qualified SEC (solar electrical contractor). On the day the SEC arrived we discussed the optimum location for the panels and the inverter.
The best location for my panels were on the West roof with a slight North aspect (280 degrees, or 80 degrees West of North) as this location had no shading from trees and plenty of roof space. The down side is that I miss most of the morning sunlight, but I do get a lot more of the afternoon sun directly on the panels.
The inverter was placed on the West wall almost directly under the panels. The inverter is weatherproof so no problems with mounting on an external wall under the eaves. You want to have the inverter as close to the panels as possible to minimize the losses on the DC run from the panels to the inverter. The AC cable then runs from the inverter to the switchboard and meter. This run can be much longer as the AC losses are minimal.

The panels are daisy chained in series to maximize the DC voltage to the inverter. The inverter then converts the DC into 240v AC at 50Hz (for Australia). The inverter will start to work once the DC voltage from the panels reaches approximately 150v and can handle up to approximately 450v.

The inverter has a nice little LCD on it that gives out information such as DC voltage and DC current from the panels and then all of the AC measurements such as AC voltage, current and frequency - with obviously the most important measurement of AC power in watts. It also gives out AC power produced for the day which is nice to know.

Now, I did not have the system installed to make loads of money from the electricity company. I had it installed to make a bit of a dent in the electricity bill. The reason being is that the government recently reduced the feed-in tariff to a measly 8 cents per kWh. So if I did not use any of the power I produce I get a whopping 40 cents per day! And, if i sell my power to them at 8c/kWh, they sell it back to me for 30c/kWh!!! We use an average of about 10kWh/day for a family of 4, but we also have natural gas hot water, cooking and heating.

So the trick to most effectively reduce my power bill with this system is to use the power I am generating straight away and put the least amount of power back into the grid as possible. To do this requires a little common sense power management. It means that if it is a sunny day and I am producing the maximum of 1.6kW I should start turning on appliances to use it up, because I am actually saving 30c/kWh by doing this.

The way this works is that any power I use will come from the nearest source, which is the inverter. If I use more than I produce it comes from the grid at a charge of 30c/kWh. If I use less than I produce the excess goes into the grid and I get a measly 8c/kWh.

So when the sun is out and I'm producing energy the washing machine goes on, then when it's done the dishwasher goes on and then after that maybe the vacuum cleaner. You get the idea. The idea being to try and match the power I am using to the amount of power I am producing. The pool filter timer is set to go on for a couple of hours in the afternoon before the kids get home and switch the TV, computer etc. on. When the sun goes down we try and minimize the power we use to just lights and the bare essentials such as the refrigerator.

Anyway, that's my system and how it works.

John K.

[Tom C]

John,

I have a 4.6 KW grid tied array. the solar panels are kyocera and the inverter is a fronius 6000 watt unit. it is wired at 320 volts to the inverter and then steps down to 120 volts A.C. panels are facing south 183 degrees to be exact at a 30 degree incline. no trees in the siteline, except during the month of winter solstice when the sun dips below some large pines we have adjacent to the property. we also have a feed in tarriff program and it is a lousy rate also. I end up seeing about a 50 dollar reduction on my bill evey month.... we have a family of 5 adults and 4 kids ages 16 to 7 so we use a lot of juice. we also have a well for water, and use natural gas for heating and cooking.

I purchased my system thru a solar lease program with solar city www.solarcity.com it is a 15 year program.... at the end of the 15 I can renew the lease, or tell them to take it off, or tell them I do not want to renew and they can leave it there hmmmm....... what company is going to want 15 year old panels? the cost of the system without federal and state rebates was 27,700.00 u.s. with rebates and tax credits it was 3000.00 u.s. (would have been 6000.00 but with the feed in tarrif program that reduced costs, the state considers me a power plant)

my inverter has a wireless nic card installed and I can monitor it thru a web browser supplied by the company. the company tracks usage and actually maintains the system for me, and repairs anything free of charge, including a blown inverter or if a panel goes south.

if you decide to go with them they have a referral program, let me refer you I can get a bit of a kickback for the sales lead..... just saying I have been very happy with the system.

I would also reccomend this system The Energy Detective (TED) great for monitoring usage, I have 2 friends that use this system one in the city to help monitor his nissan leaf energy usage from the charger, and the other guy uses it on his whole house. I have not purchased mine yet but its on the list.



Tom C

[min2oly]

Last summer my friend and I installed 1kw on my roof, 4 panels using Enphase micro-inverters. Each panel gets its own inverter. AC back to a shut off breaker box then to the city meters. I can monitor each inverter thereby each panel from the intranet. cost for panels and install materials was under $2k, Our bill has been reduced by an average of 75/mo. (estimate since it has not been a year quite yet) more in summer almost nothing Nov - Jan. Our state pays extra $$/Kwh if we buy locally made solar panels. We also just completed our federal taxes and were able to get a 1/3 credit of the 2k. these will pay for themselves very soon.

I still have the 20watt panel via SS SSG charging batteries we use to light up most of our main living spaces.

one side note - I converted all CFL's to LED's this might have put a small dent in the bill as well.

Patrick A

[alfinip2000]

John K,
I've read all about the solar panel setup on this forum.. i figure out that generally this how i can hook up the SG (attactment), my daily need about +-2kwh (planning to start small then scale up) .. need some advice from the model on the attechment based on your experience.. am curious either the capacitor after solar panel has the same effect to the battery via SG with directly from the battery charged by normal DC current.TIA
Cheers,
Alfin

[John_Koorn]

Alfin,

in my experience model 2 is the best method, however I would place a comparator cap dump circuit between the SSG and the secondary battery.

i found that that model 3 will not work for a rotored SSG as it will fall out of tune as the voltage from the panel varies according to the available sunlight. A solid state SG may work in this model but would work better if you placed a solar tracker between the panel and the solid state SG. Even so, I would still place a comparator cap pulser between the solid state SG and the charge battery.

John K.

[alfinip2000]

John K,
I see..ive read intermediate book on cap dump circuit page,is it also the same if i put on my 10 coiler?since it describe only for small SG (CMIAW)...is teslagenx also shipping to indonesia? TIA

[John_Koorn]

Hi Alfin, yes it is the same for the 10 coiler - just have to make it bigger

And yes, Teslagenx ships all over the world.

John K.

[slloyd]

here in canada it is still cost prohibitive (please correct me if i'm wrong) because there is no government kickbacks for initial investment. there is a program for feed in terrifs.. but a lot of red tape to get invovled as it looks. on the other hand, our energy is 5cents/kWH (+another 5cents of hidden fees) for total of 10cents/kwh on average so its not too bad. but still.. the idea intrigues me

one small tid-bit of info.. it is now a code requirement to install DC arc fault interrupts on the feed between panel & inverter because too many house roofs were catching on fire.

question - how did your home insurance react to this install? is your equimpent covered?

[kevin72]

Grid Tie with Battery Backup

John,

Four years ago I had installed a 6kw PV system with battery backup, here in Florida.

State offered rebates made it more affordable to entertain the idea of moving away from the gasoline generator in the event of Hurricane and power loss, which I have experienced plenty. I can tell you by experience that after a week of no power, there is no more gas anywhere locally. After trekking 60 miles for gas to power the home, solar with battery backup was a no brainer.
The system contains 32, 190watt solar panels with 2 outback inverters capable of 7KW, 2 MPPT outback charge controllers, which is all supervise via a “Mate” (think of it as a little computer tracking everything the system is doing and tracking power produced, buying and selling.) I have 8 Fullriver Dc110-12, 12v 110ah, in series and parallel for 48v within 2 banks.
The panels are fixed on the roof to maintain through 200+ mph winds, south facing to gather as much sun as possible.

In addition to the above system, we have installed a hot water solar collector, to provide hot water separate from the PV system. This is stored in an 80 gal tank. Dollar for dollar this hot water system pays for itself quickly with the amount of sun we get down here. Cold showers were a real moral damper when the power went out.

The system works really well in supporting all loads via 110v and not at all for the 220v devices such as central air, electric stove and dryer. If devices were invented to replace those power hungry units, it would be far easier to pull the plug off the grid. The long hot summers here require constant central air. Hence, the cooler months is where we see a significant drop in our bill, once we even received a negative bill, they actually owed us money! But that hasn’t happened since. Changing all light bulbs to LED and CFl also helped a lot, along with energy efficient windows and doors (hurricane rated) and keeping the attic well insulated.

We also get a lot of brown outs which come suddenly and could cause havoc on those using the computers. I also installed dedicated ground outlets on expensive devices and the main PC, this is an important and small investment that many overlook.

All in all I’m happy with the system and my family feels more secure with the seamlessness manner in which it operates.
I’m quite excited about working with the Bedini device to enable me to create an additional battery bank in order to provide additional power during the day as well as at night since replenishing the batteries and floating them takes away from powering other devices in the home. Slowly working my way towards becoming completely off grid is a huge goal. Oddly enough my installer, whom I bumped into recently, has a similar system for 10 years and his batteries were just replaced, I wonder if they could have been saved with the Bedini?

I am seriously considering learning as much as possible, in order to start business reclaiming and rejuvenating batteries here in Florida. I have already saved 2 18v ryobi batteries and 1 12v apc battery that were headed for the landfill. Just think of all those golf cart batteries….. Very exciting!

Feel free to ask any questions or to offer any advice!
Kevin