Adding Solar Panels

[AndyH]

I'm sure your installer has been in the industry for more than 20 years, is in fairly regular contact with the vendor's engineering crews, and has another source of income - that way he has not only the experience and info sources on which to make a valid comparison, but has no financial incentive to replace equipment as often as possible... But I'm probably wrong on all three counts, aren't I? :lol:

Here's a look behind the curtain. In the off-grid world, the charge controller is the interface between the solar panels and the battery bank. One of the most deployed models is the Outback MX60. As you can see here, this device has a two-year limited warranty: http://www.outbackpower.com/pdf/manuals/mx60_pv_mppt.pdf
In the real world, these devices are still in use past 15 years. There have been two subsequent generations of tech since those devices first hit the streets - the latest comes from Midnite Solar and was developed by the principal engineers that created the MX60. The Classic 150 and 200 incorporate improved cooling and component selection and are designed to be in service for more than 20. They have a standard 5 year warranty.

The simple fact is that the industry is evolving at least a quickly as computers did in the 1980s. There's been a strong push for a number of years to streamline manufacturing, improve reliability, and reduce balance of system cost. Some of that can be seen in this 2005 summary from the DOE:
http://www1.eere.energy.gov/solar/pdfs/inverter_II_workshop.pdf And in this on utility-scale equipment: http://energy.sandia.gov/wp/wp-content/gallery/uploads/Inverter_Workshop_FINAL_072811.pdf

This is a reflection of the work being done that led to today's improvements in PV, turbine, and automotive inverter tech - including the 20+ year SMA string inverters, the Enphase units, and the latest charge controllers. It's also why the current Enphase units should last longer than the initial products.

Considering that text books are about five years out of date when they're printed, and that it takes a number of years of field work to publish the first generation of papers on which the next tier summary papers are based, one would be unwise to base a decision today on published docs without becoming aware of the current state of the art And they'd be doubly-unwise to base a decision on hearsay from the internet or an installer that's done nothing more than read the out of date publications. That doesn't make any more sense than deciding not to purchas a generation four hybrid because there were reliability problems with some of the gen 1 cars (and having little awareness of what happened between gen 1 and gen 4).

And finally - back on track! Why would the OP consider expanding the system with a string inverter? The number one reason that drives me is that grid-tied systems MUST disconnect from the grid and shut down when the grid breaks. No grid, no PV, no electricity. One can expand their system with an inverter that sells to the grid while maintaining a battery. While the older segment of their PV system would drop off-line in the event the grid drops, the add-on system would disconnect from the grid, but would continue to generate power and keep the critical circuits in the house energized. This is exactly the reason that people on the East coast are looking for ways to keep their panels working when the grid goes down - one cannot buy fuel for the generator without grid power...

http://www.homepower.com/articles/choosing-inverter
http://www.homepower.com/articles/choosing-battery-based-inverter-0

And with that, I'm going back to assembling my power system - my lightning/surge suppressors have arrived. Cheers.

 

[madbrain]

One can expand their system with an inverter that sells to the grid while maintaining a battery.

Given how much the batteries would cost and their replacement as well, it would be far cheaper to have a natural gas or propane based backup generator for those rare occasions when the grid goes down.

 

[AndyH]

One can expand their system with an inverter that sells to the grid while maintaining a battery.

Given how much the batteries would cost and their replacement as well, it would be far cheaper to have a natural gas or propane based backup generator for those rare occasions when the grid goes down.

Battery cost depends entirely on the energy demand of the 'emergency/critical circuits' powered. My refrigerator uses a bit over 1kWh per day, and CFL or LED lights use almost nothing. As the folks in New Orleans and NYC/NJ learned the hard way, it's hard to get fuel when the power's out in a wide area - at any cost.

We're not living on the old Earth any longer - we can expect more Sandy's and derechos and floods and other 'fun' events. The ability to keep some power alive without needing fuel is likely to be more useful as time goes on.

 

[madbrain]

My refrigerator uses a bit over 1kWh per day, and CFL or LED lights use almost nothing. As the folks in New Orleans and NYC/NJ learned the hard way, it's hard to get fuel when the power's out in a wide area - at any cost.

We're not living on the old Earth any longer - we can expect more Sandy's and derechos and floods and other 'fun' events. The ability to keep some power alive without needing fuel is likely to be more useful as time goes on.

Lucky you. My house has about 900W of 24/7 vampire power that I'm still tracking down, between the 40 breakers on the main panel and 2 subpanels.

The 250 recessed lightbulbs (all CFL) are scattered between many different breakers. Most appliances in the house are energy star, certainly all the ones we replaced.

Daily usage with the hot tub and the EV averaged 59 kWh per day in our last billing period. There was so much rain that the 40 PV only provided 22 kWh/day, the other 37 kWh/day had to be purchased from the grid at an average cost of about 22 cents/kWh.

I think during the worst raining week, the PV only generated about 80 kWh. For a week long Sandy type power outage, 7 days at 59 kWh is 413 kWh . Minus 80 kWh from the PV is still 333 kWh. That's a hell of a lot of battery to buy and replace over time. Not to mention, if you are off-grid, how are you ever going generate enough excess energy to charge it all up ? Sounds to me like it would be far better and cheaper to buy a big fuel based generated and have enough fuel for a week ahead of time so there is no issue with purchasing fuel during the outage.

 

[AndyH]

My refrigerator uses a bit over 1kWh per day, and CFL or LED lights use almost nothing. As the folks in New Orleans and NYC/NJ learned the hard way, it's hard to get fuel when the power's out in a wide area - at any cost.

We're not living on the old Earth any longer - we can expect more Sandy's and derechos and floods and other 'fun' events. The ability to keep some power alive without needing fuel is likely to be more useful as time goes on.

Lucky you.

Nothing lucky about it - my Kill-A-Watt meters have been all over the house a couple times over. The current 22" computer monitors use 12W in operation and zero when off (and the cases are cool to the touch), compared with the 10 year old 21" LCDs that use 50W and are nice space heaters.

My house has about 900W of 24/7 vampire power that I'm still tracking down, between the 40 breakers on the main panel and 2 subpanels.

The 250 recessed lightbulbs (all CFL) are scattered between many different breakers. Most appliances in the house are energy star, certainly all the ones we replaced.

Daily usage with the hot tub and the EV averaged 59 kWh per day in our last billing period. There was so much rain that the 40 PV only provided 22 kWh/day, the other 37 kWh/day had to be purchased from the grid at an average cost of about 22 cents/kWh.

I think during the worst raining week, the PV only generated about 80 kWh. For a week long Sandy type power outage, 7 days at 59 kWh is 413 kWh . Minus 80 kWh from the PV is still 333 kWh. That's a hell of a lot of battery to buy and replace over time. Not to mention, if you are off-grid, how are you ever going generate enough excess energy to charge it all up ? Sounds to me like it would be far better and cheaper to buy a big fuel based generated and have enough fuel for a week ahead of time so there is no issue with purchasing fuel during the outage.

900W of vampire loads?! 21.6 kWh of waste? $1700+ each year will pay to run a couple of priority circuits to keep the refrigerator and lights alive along with recharging phones and laptops. Two years of savings will buy a lead acid battery that'll store about 20kWh. A quality flooded lead acid battery kept at or near 100% will likely last 15-20 years. Folks actually cycling them in off-grid service have the same life...

Super-efficient passive solar houses - three bedroom, two bath, ~1700 ft sq - use less than 7kWh per day for normal operations - and that includes supplying potable water and running an office with desktop computers, VoiP phones, high speed internet, file servers and a laser printer. Yes, it'll use more energy for a hot tub and EV.

Efficiency completely changes the requirements.

So does a month-long outage.


Prius backup:
http://priups.com/riddle/answer-1.htm

Midnight Special backup:
http://homepower.com/files/webextras/midnight.pdf

 

[madbrain]

900W of vampire loads?! 21.6 kWh of waste?

Yes, I know it sounds insane, and yet that is what the meter shows in the middle of the night with all the lights off, nothing running. The PG&E smartmeter hourly stats also report between 0.9 and 1 kWh consumption for every hour when we are asleep.

I have used my kill a watt quite a bit to narrow it down. Also have been turning breakers off one at a time to see what uses the most. Long process with the 40 breakers.
Some of the biggest users I identified so far :
- each of the two Carrier infinity AC systems uses 40W when idle . There is a total of 10 thermostats for all the zones
- my Brother MFC 9840W networked laser printer uses 40W idle
- my Kenmore induction cooktop uses 50W idle. It probably uses more energy sitting around than for cooking ! It's 220V/50A hardwired and there is no power switch. Only way to turn off the load is at the breaker.
- the Dish DVR uses 60W 24/7 . . 95% of the time it's actually idle. But it needs to be left on to record. It is not a smart machine.
- various networking equipment - cable modem, wireless router, switches, VoIP adapter - uses 60W . Not really idle, but it does run 24/7

That's about 300W of vampire, I am still trying to identify the source of the other 600W of vampire. It is a long process. I have already put x10 switches on many things to turn off things like our 6 amps, all the power bricks for hard drives and other devices that don't need to be on 24/7, etc. And still this is the best I have achieved.
Computers are always in suspend or hibernate mode, we don't leave anything on.

There is one big GE monogram built-in fridge and a GE built wine cooler which are not energy star. They cycle on and off, and are not included in the 900W reading. They are nice but over 10 years old and GE can't even give me the specs on power usage. They give me an annual cost in $ but no in kWh, which doesn't help at all. They would probably cost over $5000 to replace with comparable quality, so I won't do it unless they die. We also have an energy star freezer and another wine cooler which is energy star.

$1700+ each year will pay to run a couple of priority circuits to keep the refrigerator and lights alive along with recharging phones and laptops.

We won't have $1700 of remaining annual electric bills from the grid now with the 40 solar PV. Hard to say exactly what consumption will be exactly with the 12 extra panels, and the EV having been added both in october. December just happened to be month with the lowest solar production I ever had, and unfortunately it coincided with the highest usage. And it was the last month, just before PG&E does the true-up - not good.

Super-efficient passive solar houses - three bedroom, two bath, ~1700 ft sq - use less than 7kWh per day for normal operations - and that includes supplying potable water and running an office with desktop computers, VoiP phones, high speed internet, file servers and a laser printer. Yes, it'll use more energy for a hot tub and EV.

The house is over 4600 sq ft though, not really comparable. There is a lot of HT equipment. A lot of amps to power the 32 built in ceiling and outdoor speakers. But as I mentioned, we don't keep them on all the time.

Efficiency completely changes the requirements.

I agree, and I am certainly trying to do more. Turning off the hot tub last week dropped usage by about 15 kWh each day. Too bad it takes 8 hours to heat it all the way from cold water. I did a bit more EV charging at work also, about 3.5 kWh per day on L1. I actually ended up with two days of negative grid usage (-0.8 and -2 kWh) .

So does a month-long outage.

Yeah, I cannot imagine going through that.

Prius backup:
http://priups.com/riddle/answer-1.htm

Interesting.

 

[camasleaf]

I finally calculated that I saved enough on gas, that I can start installing a solar panel system.

- first step done: ordered one pallet of JA285 from Sunelec. 22x285W panels at $165.3 each panel. $589 to ship ..., gas is expensive.
- next step is to decide on a mounting system on the composite roof shingles

- since one goal is to be able to run off the grid I will start looking at inverter once I see how many panels I can fit on the south side of the roof. The rest of the panels will go on the est and west with micro inverters.

Let the fun in the sun begin .