Battery Backup for Grid-Tied PV Systems

Battery Backup for Grid-Tied PV Systems

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This webinar will be available afterwards at www.solarpowerworldonline.com & email

Q&A at the end of the presentation

Hashtag for this webinar: #SolarWebinar

Before We Start

http://www.solarpowerengineering.com/

Moderator

Kathie ZippSolar Power World

Presenter

Doug PrattSimpleRay Solar


www.simpleray.com 800.952.3235 705 Raymond Ave, Suite 220, St. Paul, MN 55114

A presentation for solar industry professionalsPresented by Doug Pratt, and SimpleRay Solar

SMA Sunny Island System Large(!)Outback System


But first, a moment of thanks for northern California growers… …no, not for that.

Thru the 1980’s more than half the PV sold in the U.S. ended up between Santa Rosa, CA and the Oregon border.

Back when PV was > $10/watt, it was growers who embraced and financed the birth of the solar industry.www.simpleray.com 800.952.3235

705 Raymond Ave, Suite 220, St. Paul, MN 55114


☼ Before ~1995 all PV systems were battery-based. There was no grid-tie.

☼ So the first grid-tie inverters from Trace Engineering were battery-based.

☼ Direct grid-tie is simpler, cheaper, and more efficient, so it became dominant.

☼ Think of electron flow from a PV array like water flow. Either put it someplace, or shut it off.Household loads, the utility grid, or batteries are all places to put electrons.

☼ Eventually we learned how to treatthe utility grid as if it was a battery,and direct grid-tie was born.

☼ But you always need either the grid or batteries to accept excess, or supply additional electrons as needed.


In this example the house can run on Utility Grid, OR it can run on batteries.


☼ What’s usually the first question about battery backup? What’s it going to cost? Additional retail cost to add backup to a std. direct grid-tie system (materials, labor, & markup) … $6-8k minimum.

☼ So, is backup for everyone?

☼ Who really needs it? Batteries are for folks who need instant, reliable backup. Think data and medical.

☼ Your average residential client is better (& cheaper) served with a generator and a large tank of propane … $3-5k.

For everyone else it’s convenience & bragging rights.

☼ For clients who insist on backing up EVERYTHING, generators are the best choice.Battery backup systems are only for “critical” loads.


No swimming pools, or lights on the tennis court. A/C is negotiable. Fridge, freezer, furnace, water, a couple lights and the security system.


☼ Does the customer already HAVE a grid-tie PV system installed? Or have you already sold them a conventional grid-tie system?

☼ There’s two paths to battery backup, HAVE’s or HAVE NOT’s.

☼ Got a customer who’s passed the $$ test for battery backup?

You’ll want an ADD-ON system such as Sunny Island or Magnum. An ADD-ON system will support conventional grid-tie inverters,and fool them into thinking the grid is still up.

☼ But then, have convenience & bragging rights ever failed as a sales tool?

☼ Magnum is lower cost, will work with any grid-tie inverter brand.

☼ Sunny Island will work with any brand, but works better with Sunny Boy. Sunny Island systems will do split- or 3-phase. ☼ Sub-pumps are usually the most challenging load.

Up to 3/4hp, no problem. 1hp & larger… let’s talk first.


Solar Module Array 1 (12) Sharp ND-U235Q1, 235-watt modules.

Wired as a single series string.

+- - + - ++- - - +

Solar Module Specs:

Sharp ND-U235Q1Pm = 235wVoc = 37.2vdcVpm = 30.1vdcIsc = 8.59AIpm = 7.81ASeries Fuse: 15A

PV Source CircuitsIsc of 8.60 x 1.56 = 13.4A

Ampacity required.Typical wire type: 10ga CU wire,

USE-2 in free air, or THHN-2/THWN-2 in conduit. Positive, Negative and Ground

+

G

H

Sunny Boy2500HF-US

–

N

H

Integrated PV Combiner &

600VDC Disconnect

15A fuses supplied.

G

N

H

H

Inverter Specs:

SMA Sunny Boy 2500HF-USAC Volts 240vacMax AC Amps 10.4AMPPT Window 220-480vdcMax DC Volts 600vdcMax DC Amps 15.0ACEC Rating 96.5%

Utility Grid

120/240 vac

House Main AC Panel

AC DisconnectLockable, Visible

30 amp(Not required by NEC, may be

required by local utility company or local AHJ)

20A, 2-pole circuit breaker(Best practice places inverter

input breaker(s) at opposite end of busbar from main breaker.)

Note: Sum of input breakers may not exceed 120% of busbar capacity

#8 AWG (CU) system grounding

electrode conductor.

AC Output CircuitInv Max Amps of 10.4 x 1.25 = 13.0A

Ampacity required.L1, L2, Neutral & Ground

(Best practice limits voltage drop to 1.5% at inverter max amps output)

Battery Cables & Interconnects, #2/0 awg CU

Magnum 175A Mini-Panel

AC/DC Center

Factory-suppliedconnection cable

30A 30A

on

off

30A30A

Output Input

NEUTRAL INNEUTRAL O

UT

MagnaSineMS4448PAE

Inverter/Chargerw/built-in 30A

Auto Transfer SwitchOn 175A Magnum Mini-Panel

AC IN

PUT

(Utili

ty o

r Gen

erat

or)

GRO

UND

DC

Nega

tive

DC

Posit

ive

L1 L2L1 L2 NN

AC O

UTPU

T

+-

175A

Inverting DC 54.5v 25A

Magnum Digital Display

In-line 2A Fuse

8DBa

ttery

8DBa

ttery

8DBa

ttery

8DBa

ttery

Battery PackFour 8D sealed batteries. 48-volt, 245-Amphours

Critical Loads Sub-Panel

To Supported Loads To Supported Loads


☼ Add-On kits will work with new or existing conventional grid-tie systems.

☼ Any brand of conventional grid-tie inverter is okay.

Magnum Single Add-On Kit Magnum Dual Add-On Kit Delivers up to 4,400 watts. Limited to ~4,000 watts of PV. Will start ½ or ¾ hpsub-pumps. $5.3k.

Delivers up to 8,800 watts. Limited to ~8,000 watts of PV. Will start 1.5 hp or smaller sub-pumps. $7.4k.

Sunny Island Single Add-On Kit Sunny Island Dual Add-On Kit Delivers up to 6,000 watts. Limited to ~8,000 watts of PV. Will start ½ or ¾ hpsub-pumps. $8.6k.

Delivers up to 12,000 watts. Handles up to ~ 15,000 watts of PV. Will start 2.0 hp or smaller sub-pumps. $13.5k.

☼ These kits require the dealer to install a new “Critical Loads” AC breaker panel. Breaker panel is locally-supplied. Prices quoted are ~ dealer wholesale cost.

☼ Kits all include inverter, AC/DC power center with appropriate breakers, DC cabling, 9.5kWh sealed battery pack, & battery boxes.

☼ Existing grid-tie system requires no alterations.

• www.simpleray.com 800.952.3235 • 705 Raymond Ave, Suite 220, St. Paul, MN 55114


☼ HAVE NOT systems are starting with a blank slate. No PV, & client wants backup.


☼ Direct battery-based inverter systems are usually less costly than Add-On systems.

☼ Outback, Schneider, & Sunny Island inverters are battery-based, & grid-tie capable. Not all Outback models have grid-tie software, must have a G in the model #.

☼ Direct battery-based systems can be either off-grid or grid-tied. There are many battery-based off-grid inverters.

There are a few that grid-tie.


☼ All Battery-Based systems use a Charge Controller between PV array and battery.


☼ We program the Charge Controller to get the batteries up to 56 volts.

☼ We program the Inverter to hold the batteries at no more than 53 volts. The inverter grabs any excess electrons, turns them into AC, shoves them out to the grid. Normally, this internal transfer switch is closed. If Grid fails, switch opens (~ 30 milliseconds). Utility Grid is cut off, but Supported Loads still get power thanks to PV input & stored battery energy.

☼ All battery-based, grid-tied inverter brands use this system. (Outback, Xantrex, Sunny Island)


Battery Backup for Grid-Tied PV Systems☼ The internal transfer switch is a bottleneck. At 60A capacity, we can’t (usually) backup the whole house.

So pick your “critical” loads, and run them off the “Critical Loads” breaker panel on the Inverter’s AC output.

☼ For those clients who insist on running EVERYTHING... ...a 15-20kW generator & a large tank of propane are a better (cheaper) solution.

☼ Available Direct Grid-Tied, Battery-Based Inverters Overview: ☼ Modest Systems:

Outback Single GFX Delivers up to 3,600 watts @ 120vac. 60A transfer sw. Will start ½ or ¾ hp sub-pumps (w/ optional transformer for 240vac).Available pre-assembled.

Outback Dual GFX Delivers up to 7,200 watts @ 120/240vac. 60A transfer sw. Will start ¾ or 1 hp sub-pumps. Available pre-assembled.


☼ A max of 2 Outback GFX inverters per grid-tied AC system.


Off-Grid, up to 10 FX inverters can be used in a single system.

☼ Larger Systems:

Outback GS (Radian)

Delivers up to 8,000 watts @ 120/240vac. 60A transfer sw. Will start up to 1.5 hp sub-pumps. Up to 10 inverters per system! No pre-assembly. More power, less wallspace.

Schneider (Xantrex) XW Series

4.5 or 6.0kW units @ 120/240vac. 60A transfer sw. Will start 1.5 hp & larger sub-pumps. Up to 4 inverters per system. No pre-assembly.



☼ 3-Phase Systems?

Possible w/ 3 Sunny Islands (18kW). But $$$!!

Up to 12 Sunny Islands possible with SMA Multi-Cluster (72kW). $$$$$!!

So we CAN do battery-based 3-phase, but it’s large and very expensive!

A backup generator is probably a better choice.


Battery Backup for Grid-Tied PV Systems☼ Battery Choices for Backup

☼ Going Big Isn’t Smart 1-2 days of critical loads battery capacity is prudent. More than 2 days is foolish.

Batteries are expensive, and becoming more so. Used or not, they need regular replacement. 7-10 yrs. typically. 12-15 yrs. for top-of-the-line. A generator & large tank of propane costs less for longer outages.

Most outages are less than 4 hours.

☼ What Kind of Batteries? Lead-Acid or Lithium-Ion?

Lithium-Ion is perfect when you need light weight & small size. But it’s still 4-5 times more expensive than lead-acid.

So it’s Lead-Acid. But wet-cell or sealed? And if sealed, AGM or Gel types?All lead-acid batteries need exercise to stay healthy. Sealed batteries, particularly AGM types, have their chemistry tweaked to tolerate inactivity. Wet-cell batteries suffer a short ugly life when put in backup service. Four 8D-size AGM batteries w/ 9.5kWh of useable storage works well for most systems.


Battery Backup for Grid-Tied PV Systems☼ Review

☼ Cost: $6-8k minimum. Can easily be more, depending on system size.☼ Add-on packages are an easy upgrade for existing grid-tie systems.

☼ Add-on packages are easiest way to add backup to new grid-tie systems.☼ Add-on PV size limited to ~ 8kW w/Magnum, or 15kW w/ Sunny Island.

☼ All new system? Direct grid-tie, battery-based systems are lowest cost.☼ Direct battery-based systems range 4kW to 80kW.

☼ 1-2 days of battery capacity is plenty. Use a backup generator for more days.☼ 3-Phase battery backup possible, but expensive. Think remote islands or eco-resorts. These are typically off-grid systems.

☼ Please feel free to call us for advice, support, and design services.

☼ Not ALL the client’s PV has to be backed up. We can drop an inverter or two.

Questions?Solar Power WorldKathie [email protected] Phone: 440.234.4531Twitter: @SolarKathieZ

SimpleRay SolarDoug [email protected] Phone: 800.952.3235 ext.260

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