[ecenandu]

Originally Posted by Thad E Ginathom

And what I fear is falling between two stools: spending far more than I need to keep a computer and lights/fan going for several-hour power cuts, but not having enough Kva to power the larger appliances.

The one selected sadly falls in above category. How much is your average monthly power consumption?

[Thad E Ginathom]

I think you could be right. Also, I get a quote from a local dealer which is much higher, saying that they have not included installation and taxes. Installation, yes, on closer examination he is right.

Time for some more phone calls.

My monthly power consumption... I calculated it, I'll have to do so again, but I don't think it is relevant to this purchase, because most of it is high-consumption stuff like ACs. And I know that I cannot go for 5-kva-plus system at all. So I have to see what I can afford, and work from there to what I can connect to it.

Bottom line: It must support the stuff on my desk, about 160 watts. It would be nice if it paid for it too. It is working most hours of the day when I'm at home. say, 12-16. Add a couple of fans and some minimal lighting (currently I am sitting here with 15 watts total LED lamps lighting the room. And a fan, or two. Not much, really. Although more capacity would be nice.

My priority, at this time, is backup time. Solar enhanced. OK: I could spend the money on a bank of batteries! But... I guess, above all, I just like the idea of solar power

[ecenandu]

So here is our first electricity bill.

Electricity consumed for the month of March from the grid - 480 Units.

Solar electricity production - 400 Units.

Electricity exported to the grid - 326 Units.

Solar electricity used by the house - 400 - 326 = 74 Units.

Net consumption - 480-326 = 154 Units.

So say, without solar I have to pay (480 + 74 * 7.5) = 4155 INR

Bill amount with solar 662 INR.

Bill amount without solar approx 4645 INR (including duty,meter charge etc).

Savings because of solar 3983 INR

Please correct me if I have made any mistakes.

[Holyghost]

Originally Posted by ecenandu

So here is our first electricity bill.

Hello ecenadu, If you dont mind could you please PM me a copy of the electricity bill? I never received a proper bill after I installed my solar system. Every month they make some adjustments in the system and asks me to pay Rs. 52 as rent for the meter. My export is always higher than consumption. There is no bill stating the import and export units. They claim their current system cannot bill the net metering system. I would like to confront them with a copy of your bill.

[Thad E Ginathom]

It gets more and more complicated. The guy we have dealt with for years for APC inverter and computer UPS is now a dealer for Luminous (It seems that both APC and Luminous now belong to Schneider)... but he cannot come anywhere near competing with Luminous' online shop. This is a strange relationship for a manufacturer to have with its resellers!

I had had quotes before from a local SuKam dealer (and I think their inverter/PCU is, if not more advanced, at least more configurable) and asked them to give me an updated estimate for 1KVA system inclusive of installation. Their equipment prices are the same as last year, but they are asking 35,000 for supposedly-includes-everything installation, which seems massive to me.

Previously, they had said 10k for the steelwork (for 4 250W panels). Luminous quote 10K flat, all in installation for 1kva, but our APC man says, "yes, but when the technicians arrive they will ask for more." And his includes-all quote for the Luminous 1.5kva system is more on a par with the SuKam guys' quote including the 35K. A bit less: the Luminous inverter is much cheaper than the SuKam PCU.

Questions...

The "PCUs" do much the same thing as the "inverters?" But I have the impression that the inverters are more domestic-grade, whilst the PCUs are heftier and of a more industrial build. Comments?

Overall, what do people think of installation charges? I am very much aware that I do not want this stuff to blow away in anything up to and including Vardha weather! But I am rather shocked by what is being asked for something which amounts to assembly and connection, that I could doubtless do myself. And I have to get a mason to do any masonry and an electrician to any house-wiring connection.

What should the specification and price of the DC panels-->inverter cables be? The run would be around 5-10 metres. I can minimise it by drilling, and can certainly drill even through the terrace, as it will be in an area that extends beyond the house walls. We have done this for one AC, putting PVC pipe extending above the surface so that the hole does not become a drain during rain.

[graaja]

Originally Posted by Thad E Ginathom;4178993
Questions...

[I

The "PCUs" do much the same thing as the "inverters?"[/i] But I have the impression that the inverters are more domestic-grade, whilst the PCUs are heftier and of a more industrial build. Comments?

Overall, what do people think of installation charges? I am very much aware that I do not want this stuff to blow away in anything up to and including Vardha weather! But I am rather shocked by what is being asked for something which amounts to assembly and connection, that I could doubtless do myself. And I have to get a mason to do any masonry and an electrician to any house-wiring connection.

What should the specification and price of the DC panels-->inverter cables be? The run would be around 5-10 metres. I can minimise it by drilling, and can certainly drill even through the terrace, as it will be in an area that extends beyond the house walls. We have done this for one AC, putting PVC pipe extending above the surface so that the hole does not become a drain during rain.

1. Yes. The PCUs are much more than an inverter. They implement power priority logic between Solar, Grid and Battery - Solar -> Grid -> Battery, Solar -> Battery -> Grid etc. In the Solar -> Grid -> Battery, when there is sunlight, the output of the inverter is driven by the panels. When sunlight is not present, the output is switched to grid, and if grid fails, the output runs from battery. In Solar -> Battery -> Grid, when there is sunlight, output us powered from panels.

In the absence of sunlight, output is powered by battery, and when the battery goes below a set threshold (like 50%), output switches to grid. If grid fails, the remaining charge in the battery is used. PCUs also can combine power. For example, if it is cloudy and the panels are generating say 500W and the load is at 1kW, the PCU will take 500W from the pannels and the remaining from battery.

And PCUs are built to a higher tolerance as they have to run 24x7 (like an online UPS), whereas an inverter runs only during power failure.

2. 35K installation excluding mason work and electrician is very high.

3. This depends on the voltage rating of the system like 24V, 48V, 96V etc. As the voltage rating increases, the current reduces and hence the size of the wire. So, the actual size of the wire has to be selected based on the system voltage.

[Thad E Ginathom]

Originally Posted by graaja

3. This depends on the voltage rating of the system ...

Sorry, I forgot to mention that the Luminous inverter system is 12v; the SuKam PCU is 24v.


--- We seem to be extravagant on electricity*, with bills running to around 1 lakh per year! Bear in mind that, although we are just two in number, we are both retired and so our house has 24-hour occupancy seven days a week apart from concert/shop trips and very occasional travel.

If I had 5-10 lakh to spend, we could probably reduce that EB bill very substantially. One small AC machine running overnight. And whilst my wife keeps "normal" hours, my "overnight" includes quite a lot of morning-sunshine hours.

But this would be an on-grid system, and thus, would not cover the power-cut hours.

By the way, I read recently that the Tamil Nadu EB has, due to supply shortage, a waiting list of at least six months for bi-directional meters.

*I have an errant fridge. The thermostat is dead, so it is now running all the time. It is only small, but yes, this is burning (or freezing!) money. It is a a Liebhher fridge that I brought from UK, and the local guy cannot fix it.Trouble is that I built the kitchen around the small fridge and I need to get a proper skilled carpenter, and a mason, to make room for a new fridge/freezer.

[graaja]

Originally Posted by Thad E Ginathom

Sorry, I forgot to mention that the Luminous inverter system is 12v; the SuKam PCU is 24v.

--- We seem to be extravagant on electricity*, with bills running to around 1 lakh per year! Bear in mind that, although we are just two in number, we are both retired and so our house has 24-hour occupancy seven days a week apart from concert/shop trips and very occasional travel.

If I had 5-10 lakh to spend, we could probably reduce that EB bill very substantially. One small AC machine running overnight. And whilst my wife keeps "normal" hours, my "overnight" includes quite a lot of morning-sunshine hours.

But this would be an on-grid system, and thus, would not cover the power-cut hours.

By the way, I read recently that the Tamil Nadu EB has, due to supply shortage, a waiting list of at least six months for bi-directional meters.

*I have an errant fridge. The thermostat is dead, so it is now running all the time. It is only small, but yes, this is burning (or freezing!) money. It is a a Liebhher fridge that I brought from UK, and the local guy cannot fix it.Trouble is that I built the kitchen around the small fridge and I need to get a proper skilled carpenter, and a mason, to make room for a new fridge/freezer.

I just talked to the installer who did my off-grid hybrid system, and he was telling me on-grid systems do not come at 12V or 24V. Only off-grid battery backed up systems come in this voltage rating. Usually on-grid systems are rated at a higher voltage like 120V to keep the cable sizes manageable. Can you check the system specification and confirm?

The cable size would be huge for a 12V system rated at 1kW. The currents would be around 60A to 70A, and even a 50mm2 cable will have 5% loss.

You need to take a two pronged attack to manage the high electricity bills - reduce consumption by using efficient electric equipment, and then substitute with solar. I did this in my house and it really helped. I replaced all the flourescent tube lights with LEDs, changed filament bulbs to CFLs, used inverter AC and fridge that are very effient etc. By careful selection of electrical appliances, you can definitely cut the bill by 30 to 40%. Probably the errant fridge is contributing to 20% of the power usage. That should be your first target

EDIT: A nice tool to calculate cable size.

Cable Size Calculator

[ecenandu]

Originally Posted by graaja

I just talked to the installer who did my off-grid hybrid system,

Could you provide more details on your setup, my uncle is planning to go this route, off grid.

[graaja]

Originally Posted by ecenandu

Could you provide more details on your setup, my uncle is planning to go this route, off grid.

I have a 3.3kW setup with the following.

1. 3.3kW panels wired into three strings of 1.1kW each.
2. MROTek 3kW PCU (I think MROTek closed their solar inverter division)
3. 96V / 200AH battery bank. 16 numbers of 12V/100AH batteries wired as two banks of 8 series connected batteries.

The PCU has Solar -> Battery -> Grid priority, with a battery cutoff programmed for 50% capacity.

All the loads except heavy duty loads (AC, borewell, pump, oven, rice cooker etc) are connected to the PCU.

I have a monitoring system that logs kWH consumption from inverter, kWH drawn from grid, and kWH generation from the panels to the cloud and I get daily, weekly and monthly reports on these three parameters.

The key to getting a good setup is to choose the right battery bank capacity and choosing the right PCU. I tried three different PCUs including MROTek and finalized it. There was one PCU which had a very high quiscent power of 250W, and the PCU itself was using half of the generated units!

[Thad E Ginathom]

Originally Posted by graaja

I just talked to the installer who did my off-grid hybrid system, and he was telling me on-grid systems do not come at 12V or 24V. Only off-grid battery backed up systems come in this voltage rating. Usually on-grid systems are rated at a higher voltage like 120V to keep the cable sizes manageable. Can you check the system specification and confirm?

I think I am being confusing by not making it clear whether I am talking about panel or battery voltage. In both cases, I think that the panels will be providing 24 volts. (In my dreams, at least!... nominal voltage). 4*250W gives the (nominal) I,000W. Wired in parallel?

The on-grid system is only in my dreams. The current system should certainly provide some units of electricity that would otherwise come from the grid (this is a very sunny place!) but that is a bonus to the back capability. So: off-grid for now.

[Holyghost]

The voltages depend on the regulator technology used in the inverter. Basically, the mppt and pwm. MPPT provides maximum efficiency with higher input voltages, hence the panels are wired in series to get higher voltages. They claim MPPT to be 30% more efficient than pwm.

PWM is a cheaper technology and to keep the costs low, they use low voltage circuits.
For off-grid as well as grid-tie inverters, you can buy inverters based on pwm and mppt controllers. High capacity offgrid inverters are always MPPT. Similarly, you can buy PWM based grid-tie inverters which are cheaper, but they are difficult to find for lower capacity setups here. I do see a lot of them in aliexpress.

[ecenandu]

Originally Posted by graaja

I have a monitoring system that logs kWH consumption from inverter, kWH drawn from grid, and kWH generation from the panels to the cloud and I get daily, weekly and monthly reports on these three parameters.

Do you mind sharing the above data, if it is okay with you.

How long you been using the system.

SuKam also offers similar solution as an add on, but they quoted 30K INR for that.

Originally Posted by Holyghost

The voltages depend on the regulator technology used in the inverter. Basically, the mppt and pwm.

Buddy, any inroads made to solve the KSEB bill situation?

[graaja]

Originally Posted by ecenandu

Do you mind sharing the above data, if it is okay with you.

How long you been using the system.

SuKam also offers similar solution as an add on, but they quoted 30K INR for that.

I have been using the solar system for the past 4 years.

I put together the monitoring system myself.

I bought two energy meters that have ModBus interface and connected one of these to the grid input and another to the inverter output. For measuring panel output, I made a circuit of my own using a microcontroller which measures panel voltage, current and calculates power and energy and outputs all these values through ModBus interface.

A couple of friends of mine run an IoT company and they manufacture a ModBus to GPRS gateway that reads data from ModBus slave devices and pushes to their server. I connected the two energy meters and my panel output measuring circuit to this gateway. They also have a front end that shows all the parameters in graphs and also send reports by email. As they are very close friends, I haven't paid anything for the product and the service. I can share the product details through PM. I think the cost would work out similar to what SuKam charges.

Originally Posted by Thad E Ginathom

I think I am being confusing by not making it clear whether I am talking about panel or battery voltage. In both cases, I think that the panels will be providing 24 volts. (In my dreams, at least!... nominal voltage). 4*250W gives the (nominal) I,000W. Wired in parallel?

The on-grid system is only in my dreams. The current system should certainly provide some units of electricity that would otherwise come from the grid (this is a very sunny place!) but that is a bonus to the back capability. So: off-grid for now.

For the Inverter: It is better to go for 24V battery voltage (48V is still better). That will keep the battery current in the 40A-50A range. A 12V system will result in 80A-100A battery current and is not recommended. The general rule is: higher the battery voltage, the lower will be the battery current and hence a higher system efficiency.

For the Panels: 4x250W panels can be wired in parallel to provide a 24V system with 40A to 50A current. Preferably, two parallel arrays of 2x250W in series will result in a 48V system that will result in half the current and will increase the efficiency.

So, list down all the available options for charge controllers and inverters and choose the higher voltage rating for both the panels and battery.

[Thad E Ginathom]

Hmmm... After all that I have said, I went to bed last night thinking why shouldn't I go for an on-grid system, with the aim of a major reduction in electricity bills?

I am pathetically useless with numbers, and what I said previously about our consumption was wrong. Dyscalculia, it is the numeric form of dyslexia. Seriously, I don't have a problem with words, but have always had real difficulty with numbers! But that's another story. And when I think of EB bills, I tend to forget that cover two months not one.

This is my EB history as available at the TNEB site:

Bill date--------Units-----Amount
28/02/2017----1440----7984
28/12/2016----1380----7588
27/10/2016----1500----8380
24/08/2016----1340----7324
24/06/2016----1870---10980
25/04/2016----1320----7542
27/02/2016----760 -----3846
31/12/2015----830 -----4308
29/10/2015----1440----8334
28/08/2015----1470----8994
29/06/2015----1400----8070
28/04/2015----1400----8070

It would not be possible for me to go zero-bill: I doubt I could ever afford a three-phase system! Mostly, out of three AC machines, we use one at a time, although there would be overlap: that is one hall 2-ton, and one bedroom 1-ton-inverter. Certainly I have run both of one phase, when supply problems have existed. I'm not sure that is "legal" though?

I would certainly end up with seriously unbalanced use of the phases. Theoretically horrible, but in practice I guess it doesn't matter.

Now I must revisit the posts of you guys with grid-tied systems

You need to take a two pronged attack to manage the high electricity bills - reduce consumption by using efficient electric equipment,

Second round! Have replaced most lights with CFL, and am now going for LED. The days of the errant fridge are numbered... as soon as I can get the work done to fit in a new one. We have a second fridge which also must go. The only "good" reason for it is that it is outside, and the maid puts stuff in it when we are out or asleep. Hmmm... a thermacol box has amazingly low running costs!