supported by a zinc-bromide flow- battery Chris Winter, CTO - - PowerPoint PPT Presentation

Field results from a 340kW PV Array supported by a zinc-bromide flow- battery

Chris Winter, CTO RedFlow Limited

• 340 kW roof-top mounted solar PV array supported by,
• 90 kW / 240 kWh containerised zinc-bromine flow battery

system

• Operational since July 2012

340kW PV Array supported by RedFlow’s 90kW ESS 340kW Unsupported PV Array

Field trial site – Brisbane, Australia

• PV Cost – This has been addressed as costs reach grid parity
• Why? PV panels are mainly 20kg of low-cost components e.g. glass

and aluminium

• PV Intermittency – Is now an increasing issue
• It lowers the value of solar PV, but is location dependent

2 intermittency issues:

• Up to 15-20% PV – Weather-related stability issues on the grid
• From 30-40% PV – Curtailment Issues because of too much

generation at the wrong times

• Energy Storage – represents one part of the solution for these

intermittency issues by changing the shape of the PV output curve to more closely match the customers needs.

Current challenges for Solar PV

• Charge throughout the day then discharge during peak period

(attractive to utilities struggling with too much Solar PV)

• Not ideal for most non-flow battery technologies (as they do not like

to spend 14 hours per day at 0% SOC)

• 50

50 100 150 200 250

5:00 AM 6:00 AM 7:00 AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM 4:00 PM 5:00 PM 6:00 PM 7:00 PM

Grid Output Power (kW) PV Power (kW) M90 Adjusted PV Power (kW) Sunny mid-winter day in Brisbane 146.90 kWh delivered by M90 (Peak Period for University) 289.32 kWh consumed by M90

System: 340kW PV and 90kW / 240kWh ESS Charged at 185A 8:30am-2:30pm Discharged to empty at 350A 2:30pm-5pm

Option 1 – Begin day with empty flow battery

Start Day at 0% SOC

• 50

50 100 150 200 250

5:00 AM 7:00 AM 9:00 AM 11:00 AM 1:00 PM 3:00 PM 5:00 PM 7:00 PM

Grid Output Power (kW)

PV Power (kW) M90 Adjusted PV Power (kW)

PV is not always that cooperative

• The results on an overcast day (below) highlights the need for real-

time communications to optimise end-customer benefits.

• This day began with an empty battery which charged from the PV

and the grid and then discharged into the peak demand period.

System: 340kW PV and 90kW / 240kWh ESS Charged at 185A 8:30am-2:30pm Discharged to empty at 350A 2:30pm-5pm

• Provide a guaranteed level of PV power during the day independent
• f the conditions (attractive in some applications)
• Not ideal for many non-flow battery technologies (as they do not like

to spend 14 hours per day at 0% SOC and the rest at partial SOC)

Option 2 – Begin the day with half-full battery

• 50

50 100 150 200 250

5:00 AM 6:00 AM 7:00 AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM 4:00 PM 5:00 PM 6:00 PM 7:00 PM

Grid Output Power (kW) PV Power (kW) M90 Adjusted PV Power (kW) Overcast mid- winter day in Brisbane ESS fully charged 50kW constant

• utput

Start Day at 70% SOC

Charge and discharge reacting dynamically to solar output System: 340kW PV and 90kW / 240kWh ESS

• There is no fixed ratio between the sizes of PV and energy

storage, but it is application-, cost-, site- and scale-specific

• The aim is to add as little energy storage as possible and

still maximise the value of PV energy

• Utilities e.g. peak reduction requires ~100%
• Solar Supplier e.g. increased value of solar requires <100%
• Off-grid e.g. no other back-up requires >100%

Business case - How much energy storage?

• Flow battery manufacturers partner with third-party System Integrator

(SI) companies to build energy storage systems (ESS) around standard modular flow batteries.

• Why?
• Flow battery manufacturers are usually only experts in the battery

part of an ESS (not PCS, controls etc.)

• Easier to address international markets - 80% of regulations apply

to the PE/PCS part of an ESS, which the SI already has.

• Fortunately, due to the “uniqueness” of flow batteries, the market
• pportunities are growing as is interest from companies with

System Integration capabilities and end-customer demand.

• This business model needs “standard flow batteries” to integrate,

as is the case with lithium-ion or lead-acid batteries.

Business case – “System Integrator” strategy

• Array of modular flow batteries used to build the energy storage

system up to 240kWh maximum capacity

• Uses standard 3 kW(cont.) / 8 kWh flow batteries connected in

an array

• M90 contains:
• 24 flow batteries
• 90kW PCS
• Fan-based cooling
• Remote control

M90 Zinc-bromide flow battery

Zinc-bromide flow batteries operate from empty (0% SOC) – so it can shift more energy per kWh installed

• It is a zinc electroplating machine made out of plastic
• It takes advantage of the high energy Zn-Br reaction and low-cost

plastic manufacturing

• Its cost potential is a function of the raw material cost – just like PV

How a zinc-bromide battery works

• 120kW/300kWh flow battery system.
• Roof-mounted 120kW PV array
• Integration with Johnston Controls

Building Management System

• Commissioning in May 2013, Brisbane,

Australia

Building Integrated flow battery

Chris Winter, CTO RedFlow Limited