Category Archives: energy

How much renewable energy does it take to offset flying a Pilatus PC12?

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The other day, I was talking with someone about the wonders (and the satisfaction) of operating a large renewable energy system at our Tasmanian farm, and how I get to charge up my electric motor glider and go flying on sunshine, and how we’ll replace all the farm machinery that burns diesel with electric vehicles as soon as someone will sell that electric farm machinery to me (all of which is true).

One of our children kindly (and accurately) popped that balloon for me with a single sentence, by saying: ‘Yeah, but you also fly a turbojet aircraft’.

The plane we fly is a most wonderful beast called a Pilatus PC12 NGX. The convenience, speed, capability and sheer reach is just fantastic. I also get huge personal satisfaction from flying it. However, ‘satisfaction’ is not a Carbon offset.

This conversation lead me to pose a question to myself:

Can our solar array create enough renewable electrical energy to completely offset the carbon dioxide emissions involved in flying our aircraft?

I decided to work it out.

I don’t claim to be any sort of saint – the idea is just to see if it is possible to achieve something like ‘Carbon Neutrality’ by offsetting the aircraft Carbon emissions with solar array Carbon savings.

I’ve tried to get the numbers right here (and they make sense to me)… but if I’m getting the sums wrong somehow (or misunderstanding the source data), I’d be very keen to find that out. That’s one of the reasons why I’ve posted it all here… to subject these calculations to the light of day.

Source Data

My annual flying hours in the PC12: 200 (average over the last 3 years)

Average hourly fuel burn for my mission profile: around 250 litres per hour

Carbon Dioxide emitted per litre of Jet-A1 burned: 2.52Kg (source: “COP25: What is the impact of private jets?“)

Solar array size at The Vale: 200 kW

Average energy generated per annum per 1 kW of array size at The Vale: 1340kWh

Thus for a 200kW array we will make about 200 x 1340 = 268,000 kWh annually (Source: LG Solar Output Calculator ; My ‘actuals’ to date are highly consistent with that calculator).

Whether we use it on site for buildings or for electric tractors, or whether we export it, this is all energy that isn’t being generated somewhere else, hence it is net electrical energy we are adding to the total renewable electrical generation of the world.

Our actual export figure right now is above 90%, though that will reduce as we add more electric farm machinery over the coming years – in the process of progressively reducing our diesel burn figure to zero.

Our farm is in Tasmania. This complicates things because the Tasmanian energy grid is already incredibly ‘green’ – see below:

Source: https://www.industry.gov.au/sites/default/files/2020-12/australias-emissions-projections-2020.pdf

However: Tasmania has one substantial inter-connector to Victoria (Basslink) and there is another big one, MariusLink, on the way. Those interconnections allow Tasmania to sell electricity into the Victorian grid. So we’ll use the Victorian grid as our imputed destination.

The current official figure for Carbon Dioxide emission per kWh generated in Victoria is 1.13Kg per kWh (Source: The Victorian Essential Services Commission).

Now we have all the numbers we need. It is time to start doing some maths.

Annual PC12 Aircraft Carbon Dioxide Emission Created

200 hours x 250 litres per hour x 2.52 Kg per litre = 126,000 Kg

Annual 200kW Solar Array Carbon Dioxide Emission Avoided

268,000 kWh x 1.13 Kg = 302,840 Kg (or 2.4 times the PC12 emissions)

Outcome

Assuming the energy destination is the Victorian energy grid, we are offsetting the aircraft Carbon footprint more than twice over! This was a (good) surprise to me.

That said, Victoria has a particularly ‘dirty’ grid. Sigh…coal…sigh.

What happens if we make this harder, by using the global average Carbon intensity value for energy grids instead of the value for Victoria?

The global average figure is far lower than Victoria, at around 0.5Kg per kWh generated (source: https://www.iea.org/reports/global-energy-co2-status-report-2019/emissions ).

Taking 126,000Kg and dividing it by 0.5Kg per kWh, we get a clean energy generation target of 252,000kWh.

This is still substantially below the 302,840Kg annualised energy production from the solar array at The Vale. Even on this ‘global average’ Carbon intensity basis, we are (more than) completely offsetting the Carbon footprint of my annual PC12 flying time.

One other thing we can derive from all of this is the ratio between flying-hours-per-year and the needed solar array size (for a solar array in Tasmania, and using the higher bar of 0.5Kg offset per kWh generated):

Dividing 252,000 kWh by 200 hours means 1260 kWh of annual energy production is needed per annual-flying-hour. Given that each kW of array size generates 1340kWh per year (in Tasmania), we need 1260/1340=0.94 kW of solar array size per annual-flying-hour in the aircraft to achieve a full offset of the annual flying time concerned.

To put it another way, we need 94kW of solar array size to offset (on a continuing basis) each 100-hours-per-year of flying time in the aircraft.

Time for a bigger calculation.

How much solar would it take to offset the entire global aviation industry?

According to this source, around 900 million tons of carbon dioxide were emitted annually due to global aviation immediately pre-COVID (assume we wind up ‘back up there’ post COVID… eventually).

So that is 900,000,000t x 1000Kg = 900,000,000,000 Kg of CO2. Yikes.

Dividing by 0.5 means we would need to generate 1,800,000,000,000 kWh of electricity from (new) renewable sources to offset the entire global aviation industry.

We are a small investor in a big project: “Sun Cable” . The first major project for Sun Cable will build around 20 Gigawatts (!) of solar arrays in the wilds of the Northern Territory, and export most of it to Singapore.

Yes, really. If you don’t think big, you don’t get big.

The LG Solar Calculator says one could expect 1940kWh of electricity per kW of solar array in Alice Springs. Multiplying 1940kWh by 20,000,000kW gets us 38,800,000,000 kWh (38,800m kWh) per year.

This is just my back of the envelope approximation, and the real outcome in terms of output energy from Sun Cable could well differ somewhat from that estimation for a whole host of rational technical reasons, including things as obvious as energy loss over long transmission paths, that the project isn’t actually in Alice Springs, etc etc.

So: We’ll de-rate that annual production estimate by an arbitrary 25% to fold in some pessimism and call it a ‘mere’ 29,100,000,000 kWh per annum.

Time for the punchline:

1,800,000,000,000 / 29,100,000,000 = around 60 (these are all huge approximations – so – measure with a micrometer, mark with chalk, cut with an axe)

The punchline (and this was also a surprise to me) is this:

It could take just 60 Sun Cable-sized projects to offset the Carbon emissions of the entire global aviation industry

The world could actually do that. If we can make one, we can make sixty.

The Sun Cable web site says that the initial project for the company is an AUD$30+ billion project (US$21bn at the time of writing).

Sixty of those would be a mere US$1260 billion (US$1.3tn). An impossibly large number to consider? Well, the four largest American companies each have a market cap well above this level.

Apple has enough cash on hand (at the time of writing) to build the first 9 of these mega-projects without even taking out a loan. Remember, too, that these will be highly profitable projects, not donations. They won’t merely mitigate carbon – they’ll (literally) power the world.

We have enough sunlight. We have enough land. What we need is enough ambition.

Deploying the worlds smallest flow battery (The Redflow ZBM2) from small sites up to grid scale

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I delivered a (virtual) talk at a recent (August 2021) battery technology conference in South Africa.

Having taken a look at the recording, I think it has come out as a reasonably clear and cogent summary of the current state of play in terms of the deployment of, and the scaling of, Redflow ZBM2 based energy storage systems.

The talk runs for about half an hour, and you can find it here:

Deploying the worlds smallest flow battery at grid scale

The slide deck that went with it is here:

hackett-redflow-deployment-at-scale-v2Download

The Vale Energy System

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About The Vale

The Vale is a 170 Acre farm in the NorthWest of Tasmania. It is located in a river valley in the shadow of Mount Roland.

Various crops are grown on the property along with the running of sheep and cattle. The property also features a large private runway.

The Vale, Tasmania

We wanted to future-proof the property in terms of electrical energy self-sufficiency by building a large renewable energy system.

Here is what we built…

System Components

  • Three phase grid feed via a 500KVA transformer (configured for up to 200kWp export)
  • 200 Kilowatt Peak (kWp) ground-mounted solar array using LG 375W panels on Clenergy ground mount systems into 8 x 25kWp Fronius Symo AC Inverters
  • Provision for future on-site generator
  • 144 kW / 180 KVA Victron Energy Inverter/Charger array (12 x Victron Quattro 48/15000)
  • 280 kWh of Flow Battery energy storage (28 x 10kWh Redflow ZBM2 zinc-bromide energy storage modules)
  • Victron Cerbo GX system controller interfaced to 3 x Redflow Battery Management System units
  • Underground sub-main distribution system servicing multiple houses, farm buildings and an aircraft hangar across the entire farm
  • Underground site-wide single-mode optical fibre network serving site-wide indoor and outdoor WiFi access points and networked access control and building management systems

A shout-out to DMS Energy in Spreyton, Tasmania. I designed the system with them, and they built it all extremely well. The installation looks great and it works brilliantly.

Here is a gallery of images from the energy system

DCIM\100MEDIA\DJI_0035.JPG
The Vale Energy System

Flow Batteries

The system stores surplus energy in Redflow Zinc-Bromide flow batteries. These are a product that I have had a lot to do with over a long period (including as an investor in the company and as the the architect of the Redflow Battery Management System).

These batteries have a lot of advantages, compared to using Lithium batteries, for stationary energy storage applications such as this one.

You can read more about them on the Redflow site and also in various other blog posts here.

System Performance and Future Plans

Tasmania is interesting as a solar power deployment area, because it has the distinction (due to being a long way south!) of being the best place in Australia for solar production in summer, and the worst place in the country for solar production in winter!

This was a key driver for the decision to deploy a relatively large solar array, with the aim of obtaining adequate overall performance in the winter months.

The large solar array is also a renewable transport fuel station!

We already run one Tesla Model S sedan, a Polaris ‘Ranger’ electric ATV, and an electric aircraft on the property.

Our plan is to progressively eliminate the use of diesel on the property entirely, by running electric 4WD vehicles, electric tractors, and electric excavators as they become available on the Australian market. The beauty of the large on-site solar array is that all of these vehicles can be charging directly from on-site solar generation when they are not being driven.

During this winter, we’ve observed that we typically manage to half-fill the battery array, and that it then lasts about half the night before grid energy is required.

That’s why we are now in the midst of doubling the size of the solar array. Once we have done so, we will have a system that (even in mid winter) can supply all of the on-site energy demands of the property on most days, without drawing any grid energy at all.

Of course, in summer, we’ll be exporting plenty of energy (and being paid to do so). Even with the relatively small feed-in tariff offered in Tasmania, the system generates a reasonable commercial return on the solar array investment in non-winter months.

Here are some (summer time) screen shots from the on-site control system and from the outstanding Victron VRM site data logging portal.

System Monitoring Example

On the image from the on-site Cerbo GX controller, you can see a point in time where the solar array was producing more than 90W, the battery array was mostly full and starting to roll back its charging rate, and plenty of that solar energy was also being exported to the grid.

The ‘System Overview’ and ‘Consumption’ charts show the outcome of all that sunshine…with the battery ending the day pretty much full, the site ran all night on ‘time shifted sunshine’ and started the following day half full, ready to be filled up once more.

We exported plenty of green energy to our neighbours and we used practically no inward grid energy at all.

Once we have doubled up the solar array size, we are looking forward to achieving a similar outcome on most winter days, not just during summer, along with exporting even more surplus green energy into the grid.

Once we have transitioned all the on-site vehicles to electric, our total export energy will diminish somewhat, but it will be more than offset by a $0.00 diesel fuel bill (and by zero CO2 and Diesel particulate emission from our on-site activities).

On-site Energy Efficiency

One thing that matters a great deal is to do the best you can in terms of energy consumption, not just energy generation and storage. To state the obvious: The less energy you need to use, the longer your battery lasts overnight.

All the houses on the farm are heated/cooled using heat pumps.

This is the most efficient way to do it, by far. It is often poorly understood just how much more efficient a heat pump is, compared to any other way to cool or heat something.

That’s simply because a heap pump doesn’t create the heat – rather, it moves heat energy in the outside environment into the house (or vice versa, to cool it). Typical values for the Coefficient of Performance (COP) – the ‘multiplier effect’ between kilowatts to run a heat pump and kilowatts of heat energy that can be moved – are of the order of 3-4 times. That literally means that 3-4 times as many kilowatts of heating or cooling are created than the number of kilowatts of energy put into the device to do it. By contrast, heating using an electrical ‘element’ has a COP of 1, meaning there is literally no multiplier effect at all.

Because we’re in Tasmania, and it does get cold in winter, we have put in a wonderful indulgence in the form of a Spa pool. These obviously need a fair bit of energy to keep the pool water hot, and we have done two things to minimise that energy draw.

First, we have used a Spa heat pump to do the hot water heating, which accesses that fantastic multiplier effect mentioned above. It means we are heating the water by just moving heat energy out of the surrounding air and into that water.

Second, we have installed an optional monitoring and control device so we can access the Spa and remotely control it. We can turn the heating off when we are leaving home, and we can then remotely turn the heating back on when we are heading back, so it is nice and hot when we arrive.

We have a third heat pump at our home, the one that heats our hot water. We are using a Sanden Heat Pump based hot water system that (also) performs really well.

On-site Energy Monitoring and Control

The key to optimising energy usage is to be able to actually measure it.

The Victron Energy Cerbo GX at the heart of the energy system monitors all aspects of our renewable power plant in detail (and uploads them for easy review to the no-extra-cost Victron Energy VRM portal). This gives us fantastic (and super detailed) visibility into energy generation, storage, and consumption on site.

However, we have a lot of separate buildings on the farm, and the key to understanding and optimising energy draw is to get deeper insight into which buildings are using energy and when.

To that end, we have installed many Carlo Gavazzi EM24 ethernet interfaced energy meters all around the site-wide underground power network. At each delivery point into a building, there is an ethernet-attached meter installed, so that energy usage can be narrowed down to each of these buildings with ease.

I am currently working on the design of an appropriate monitoring system that will draw this data in and use it to provide me with detailed analytics of where our energy is going on a per-building basis (and when!).

In terms of control we have deployed KNX based sensor and control devices in a variety of places around the property, and we plan to deploy much more of it. Over time, we’ll be able to dynamically control and optimise energy consumption in a variety of useful ways.

KNX is a whole separate story, but – in brief – its an extremely good way to implement building automation using a 30+ year old standardised protocol with full backwards compatibility for older devices and with support from over 500 hardware manufacturers. It allows for the successful deployment of totally ‘mix and match’ multi-vendor collection of the best devices for each desired building automation monitoring or control task.

We are continuing to learn as we go.

With the upcoming enhancements in site monitoring and control, we expect to deepen our understanding of where energy is being used, to (in turn) allow us to further optimise that usage, using techniques as simple as moving various high energy demands to run ‘under the solar curve’ wherever possible. These are the times when on-site energy usage is essentially ‘free’ (avoiding the ‘energy round trip’ via the battery, and leaving more battery capacity for energy demands that cannot be time-shifted overnight)

Summary

Overall, this system is performing extremely well, and we are extremely pleased with it.

When we have added even more solar, it will do even better.

The #1 tip – even in Tasmania – is clear: Just Add More Solar 🙂

The other big tip is to move your transport energy usage to electric.

The more electric vehicles we can deploy here over time (farm machinery as well as conventional cars), the better.

We’ll charge them (in the main) directly ‘under the solar curve’ and achieve a huge win-win in terms of both energy usage and carbon intensity.

As we keep learning and keep improving the monitoring and control systems… it will only get better from here.

The Redflow Gen3 ZBM

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The Redflow Zinc-Bromine Module (ZBM) is the smallest commercially available hybrid zinc-bromine flow battery in the world. The size of these 10kWh energy storage modules means they can be deployed in applications, such as telco tower sites, that were previously impossible to address with flow batteries, yet they can also scale to grid-level energy storage.

The Redflow ZBM is a convention-breaking energy storage machine. It can be thought of as a miniature, reversible, zinc electroplating machine made largely of recyclable plastic. The innovative Redflow battery design uses abundant and relatively cheap minerals in its electrolyte formulation. These attributes gives the product strong environmental credentials. 

I recently spent some time at Redflow’s Brisbane headquarters taking a close look at the new Redflow Gen3 energy storage module. It is impressive to see just how far the Gen3 project has progressed in recent months and to appreciate the level of innovation it embodies.

Redflow has developed and optimised the design of its Gen3 battery in various stages during  the past five years, incorporating knowledge and optimisations based on field deployment of the Gen2.5 product. The Gen3 battery utilises the advanced manufacturing capability developed by the company in its own dedicated factory and delivers a streamlined product designed for reliable and high volume production.

The Gen3 ZBM is slightly smaller, and yet delivers the same baseline performance specifications as the Gen2.5 module. Gen3 is designed to be an easy, drop-in replacement for the previous model in any customer application.

Redflow initiated Gen3 customer trials at the end of 2020 and also undertook further lab testing of key components and complete new Gen3 batteries. This has led to further design advances in Gen3 flow distribution, management of shunt currents and software optimisation. The current expectation is that Gen3 will be introduced into production around the end of 2021.

This is what a Redflow Gen3 ZBM looks like:

Redflow Gen3 ZBM

It is time to take a look under the hood… and the more you look, the more improvements become evident.

This is a photo of some Gen2.5 batteries, for comparison, sitting beside a Gen3 battery undergoing testing at Redflow:

Gen3 battery beside some Gen2.5 modules

There are many improvements in Gen3, all designed to reduce parts count and cost while also making the product easier to manufacture.

Single Stack vs Dual Stacks

The key Gen3 improvements are related to the “heart” the device, the electrode stack.

This unique battery stack design, materials set and manufacturing system are where the majority of the Intellectual Property, Patents and Know-How developed by Redflow over the past 10 years resides. The new Gen3 stack represents a major step forward for the company in all of these respects.

This new product implements a single 10kWh stack at the top of the Gen3, replacing a pair of 5kWh stacks on the Gen2.5 model. Having just one stack instead of two delivers an obvious long-term reliability benefit.

That single stack also lowers production cost and reduces complexity in physical, chemical, and electrical terms. Redflow has also revised the internal construction of the new stack, including the fluid flow paths and the stack surface itself, for simpler and faster manufacture.

Gen3 Stack electrode plate layers ready for final assembly

This single stack design eliminates the need to wire the two stacks together in parallel with an adaptor plate on the front of the stack, reducing parts count and complexity.

Moving to one stack also removes the requirement to bind the two stacks tightly together with large metal plates and long bolts. The Gen2.5 requires these relatively costly structures to maintain a consistent electrolyte fluid seal and to manage consistent electrolyte flow across both stacks. In Gen3, none of that is needed

The single new stack is simply strapped on to the top of the battery tanks, making it easier to replace the stack in the future, if required.

Because the stack is also a major cost item in the ZBM bill of materials and is also a critical path item in manufacturing time, the single stack delivers obvious and profound implications in terms of increased peak factory production rate and decreased overall production cost.

New Electronics Module (MMS)

The Module Management System (MMS) – the electronics box on the front of the battery stack – contains power-handling and control electronics which are run by an on-board device management computer.

The Gen3 MMS has been totally redesigned, delivering both short and long-term benefits.

The Gen2.5 battery MMS contains several separate circuit boards, due to more than a decade of incremental development. Gen3 puts them all on a single, redesigned, higher performance board.

The Gen3 battery MMS also has battery terminals on the front of the unit, rather than ‘behind’ the MMS, which makes electrical interfacing a lot easier.

The Gen3 design eliminates the separate “Energy Extraction Device” (EED) sold with Gen2.5 batteries by building that functionality into the MMS as a software-controlled element.

The new MMS costs much less to make and is far more powerful in terms of CPU and I/O capability.

Advanced current flow management and software-driven bidirectional DC/DC conversion circuitry allows for the development of improved MMS firmware to deliver new software-driven current control and voltage control features, along with other planned improvements. These will be rolled out to customers through in-field software updates via the Redflow Battery Management System (BMS).

Other improvements in the new MMS Include the use of solid-state circuit-switching hardware based on Field-Effect Transistors (FETs) to connect, disconnect and mediate energy flow into each ZBM, versus the use of three physical ‘Contactors’ inside the Gen2.5 MMS. This eliminates some expensive moving parts from the MMS by replacing them with devices that are not only faster but that have an essentially unlimited cycle life in this application.

Redesigned electrolyte tanks, pumps, and cooling structure

The ZBM has two electrolyte tanks, each with its own pump. The Gen2.5 uses a nested, ‘tank within a tank” arrangement that, while elegant, is quite complex and expensive to make. Gen2.5 tanks are also constructed with many sharp corners and a complex side-wall design, making high volume manufacturing even more challenging.

The new Gen3 tanks are quite different. This is a picture of the new tanks with pumps without any other parts installed. You can see that there is a new plastic formulation and that they feature distinctly rounded corners:

tank

This is all designed to optimise the tank for volume production. This design is easier to build and has an increased tolerance for variation between tanks during the manufacturing process. The new tanks are also arranged as a simple left-right pair – much simpler than  the Gen2.5 nested tank structure, further improving ease of assembly.

The pumps have also changed. For historical reasons, the Gen2.5 pumps are actually 140 volt DC pumps that require a custom-designed voltage uplift circuit inside the MMS to drive them. The Gen3 pumps are 24 Volt DC pumps that can be more easily and efficiently driven from the MMS.

As part of the new Gen3 design, Redflow is also introducing a new cooling system using a new set of Filtering Polymeric Fibrous materials which will improve battery performance.

All up, the new tank cooling system and pump set represent a major improvement, designed, like the rest of Gen3, for repeatable high-volume manufacture at a lower production cost.

Purpose-built electrolyte ‘bund’

In many markets, energy storage devices that use fluid electrolyte in field deployments need to include a ‘bund’ – somewhere to catch and hold electrolyte fluid in the unlikely event of a fluid leak.

For the Gen3 battery Redflow has a new purpose-built bund. This is the plastic enclosure extending to about halfway up the battery on all sides, that is visible in the lab test photo above.

The intention is to ship Gen3 batteries with this bund included, saving installers the need to arrange and install a separate bund.

Gen3 Summary: Greater reliability, lower cost, faster production

The Gen3 module marks a major transition for Redflow.

Gen3 is designed for volume manufacture, with a design emphasis on fewer parts, greater ease of manufacture, and more compatibility with automated production techniques. By intent, this all leads to a lower production cost and greater long-term reliability.

These improvements benefit both Redflow and its customers as the company moves to ramp production volumes to meet the rapidly expanding global demand for scalable, sustainable and reliable energy storage.

Pod Z: The Redflow Grid-Scale HVDC Energy Pod

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Simon Hackett, Redflow System Integration Architect

introducing Pod Z

Redflow is in the midst of building a new “Pod” based energy storage architecture, with the first customer for that deployment also being its largest customer to date.

The story below includes a link to a short video about the new architecture Redflow has designed to support entry into the Grid-Scale energy storage market:

https://redflow.com/redflow-enters-a-high-capacity-high-voltage-grid-scale-future-with-energy-pod-z-energy-storage-modules/
Redflow Pod Z grid-scale architecture using Trumpf HVDC modules

When we made that video, we hadn’t formally announced our partnership with TRUMPF Hüttinger, the company we’re working with to deliver this scalable architecture. A few days later, we were able to make that announcement:

https://redflow.com/redflow-trumpf-pod-z-grid-level-energy-storage-deployments/

How Does Pod Z Work?

Now we’ve made that announcement, I can explain how this nifty stuff works.

Here’s a photo of a Redflow Pod Z with some of the covers taken off:

Redflow Pod Z internal elements

On the left is the battery cabinet with one of four covers removed. This cube-shaped cabinet holds 16 x ZBM2 storage modules, 8 to a side.

Ventilation paths run inward at the base of each pod. Air flow then rises via a ‘cold aisle’ in the middle of the pod, proceeds through each ZBM2, and exits as warmer air via fans installed behind each cover door.

While the Redflow modules you can see here are the existing Redflow ‘Gen2.5’ devices, the upcoming Redflow Gen3 modules will also be a perfect fit, in both physical and electronic terms (and they are designed to be).

To the right is the electronics cabinet for the pod. Inside that cabinet, at the lower right, is a cluster of six Trumpf DC1010 units with a Trumpf System Controller.

The DC1010 module achieves something quite special. It is a bidirectional DC/DC converter that can shift voltage up to a very high ratio (around 15:1).

These modules are clustered together and driven in a unified manner via the the system controller.

On the the low-voltage side, these modules interface to a standard 48V telco standard voltage bus (compatible with Redflow ZBM2 modules).

In fact, beyond merely being ‘compatible’ with Redflow ZBM2’s – the Trumpf product has been specifically designed for flow batteries!

This product line has been created by Trumpf in response to the rising demand for the use of flow batteries in large energy systems.

Flow batteries are long duration, 100% depth-of-discharge, durable and high-temperature-tolerant workhorses. They compliment, rather than conflict, with the use of shorter-duration/higher-peak-output capability Lithium batteries.

Trumpf have developed this product line at a time and in a manner that is an ideal complement to Redflow energy storage modules, and that paves the way to create grid-scale hybrid deployments that include flow batteries.

Flow battery support in the DC1010 includes a capability to have the low voltage DC bus operating all the way down to zero volts. The units then support smoothly raising the voltage of a flow battery back up to its normal operating voltage range, smoothly ramping a current-limited/current-controlled energy supply to the modules, as part of commencing the next charge cycle.

The DC1010 modules are each rated at 200 Amps continuous on the low voltage bus, meaning that this cluster of six units can support up to 1200A on that bus.

In the first Pod Z configuration, Redflow has rated each pod at a nominal continuous energy throughput of 50kW.

The low voltage bus comes together on the left hand wall of the control cabinet. On that wall is a pair of DC bus-bars sandwiched around insulation layers, with built in ‘comb’ connectors that allow the battery circuit breakers to bolt straight on to the bus-bar.

A set of 48V bus cabling (visible on the left hand wall) fans out from the bus-bar to all 16 batteries on the left, and additional cables run down to the DC1010 cluster at the lower right.

On the high voltage side, the DC1010 units support a (software selectable) interface voltage in the 765-900 Volt range.

On the lower part of the rear wall, you can see the output side cables for the high voltage side. Those (small!!) wires run at circa 800 volts and come together to the high voltage interface terminals. At a 50kW power level, across six DC1010 units, at (say) 800V, the current being carried from each of the cluster modules is a mere 10 amps (50,000 / 6 / 800). This is why those wires are so small – because they really don’t need to be larger.

This is one half of the key to grid scale battery deployments. That high DC voltage means the total cable size – even for a DC bus visiting many Pods in parallel in a single site – really isn’t all that large.

The other half of how this architecture supports high scale deployments is the way that voltage management happens on that high voltage DC bus. We are operating these modules in a mode that Trumpf call ‘Voltage Static Mode’.

In this mode, the DC1010 cluster converts the variable ‘48V rail’ DC voltage into a fixed voltage outcome on the high voltage side. All the pods are programmed to have the same HVDC voltage when idle, and they are just wired together in parallel.

To connect the DC pods to an AC energy grid, third party AC inverter/chargers are used.

When those inverter/chargers wish to discharge or charge from the overall Pod array, they simply ‘pull’ or ‘push’ against that DC voltage. If the inverters try to discharge, they naturally draw the DC voltage down in the process. The external draw-down on the DC rail acts as an automatic signal to the DC1010’s to start to deliver output energy. The amount of energy they deliver is proportional to the voltage shift that the inverter/charger initiates on the DC bus.

In the reverse direction (array charging), the inverter/charger drives the DC voltage up, and the DC1010’s respond to this by moving energy from the DC rail into the Pods. Again, the amount of current that flows is controlled via the voltage shift that the inverter/charger initiates.

Here is a diagram showing this result, just to make it clear (taken from the Trumpf system documentation):

The deep point of this operating mode is that each pod acts like an ‘ideal’ battery on the HVDC side, that:

  • always sits at the ‘perfect’ voltage, waiting for work to do
  • can be wired to an arbitrary number of similar pods
  • can be wired to, and commanded by, inverter/chargers

… all using the chosen DC link voltage – and shifting of that voltage – as a command mechanism that requires no software interface and no real-time cluster synchronisation for it to work.

In the initial deployment site there will be twelve pods sitting in rows on concrete plinths, delivering 600kW throughput via 12×16 module pods, for a total of 192 Redflow ZBM2 modules on site:

Deployment arrangement using 12 x Pod Z modules

Meantime, back inside each Pod Z, the Redflow ZBM2 modules are coordinated and controlled by Redflow’s purpose designed BMS, operating in a cluster-friendly ‘Slave’ operating mode.

Each Pod Z’s BMS:

  • Drives the Redflow ZBM2 module operating cycle internally in each pod, including coordinated maintenance cycles for batteries at appropriate times
  • Actively controls the operation of the Trumpf equipment cluster using a newly developed Trumpf operating module in the BMS. This code sends continuous updates via MODBUS-TCP to the Trumpf cluster, keeping it informed about the present operating limits of that particular cluster of ZBM2 modules. The key parameters sent are the maximum charge capability, maximum discharge capability, and the target charge voltage for the ZBM2 cluster.
  • The BMS provides secure remote management access to the Trumpf system controller and manages the high level configuration of the pod (including setting the HVDC operating voltage and current limits in Voltage Static Mode).
  • The BMS also watches over the Trumpf cluster, monitoring and logging operating parameters including voltage, current, and three temperature measurement points inside each DC1010 cluster member

With each Pod Z being fully managed by its internal BMS, all that remains is to aggregate the status of all Pods together, for the benefit of, and the coordination of, the on-site inverter/chargers and on-site Microgrid controller.

A Redflow BMS operating in in ‘Master’ mode is interfaced over ethernet to all the downstream Slave BMS in each Pod Z that it watches over.

The Master BMS passes overall status data to the on-site microgrid controller. This includes System State of Charge, overall site charging and current discharging capacity, temperature, and state of health. This information is provided via industry standard CANBus ‘Smart Battery’ protocol, MODBUS-TCP, and/or JSON queries to the Master BMS.

Summary

The Redflow Pod Z architecture has been designed with, and around, the Trumpf ‘TruConvert’ DCDC power system architecture.

The combination creates a powerful, integrated high voltage energy storage system that can be scaled to an essentially unlimited extent.

The interface mechanisms being used allow the high energy, high voltage Pods to be parallel-wired without complex or difficult real-time synchronisation or balancing mechanisms. Instead, the software-mediated Trumpf cluster creates a ‘perfect’ battery voltage for every Pod, driving the simplest possible integration path for high scale site designers.

The Redflow BMS acts as a per-Pod orchestrator for the Redflow ZBM2 modules downstream, and as a coordination and control point for the Trumpf DCDC converters in each Pod, and passes aggregated energy storage status data upstream to the on-site master Microgrid controller.

This architecture plays to the strengths of all of the components concerned. It is is designed for reliability, redundancy, and scale.

Life, the universe, and Redflow

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Today Redflow announced the appointment of John Lindsay as a non-executive director of Redflow Limited. John has deep skills and experience around technology and technology related business matters. He is, to use a favourite phase (for us both), ‘smart and gets things done’.

Its worth appreciating that John has specific expertise and experience in precisely the realms that Redflow needs. I sent John over to Brisbane when I originally invested in Redflow, to help me assess the technical merit of the technology. He, like me, has been a shareholder in Redflow ever since.

In addition to being a great businessman, John is also a technology geek at heart (as am I). He has been an active member of the electric vehicle and renewable energy community for many years. His daily driver is electric (as is mine) – of course. He knows which end of a soldering iron is the hot end.

His idea of a fun weekend hobby is (literally – and recently) to have set up a D.I.Y. solar and battery offgrid system in his own garage to charge up his electric car from renewable energy because… he can (and because he knows how to).

His appointment frees me up to transition my own head space in the Redflow context totally into the technology around making our battery work in the real world. Doing that stuff is what I really love about being involved with Redflow. I love helping to make this amazing technology sing and dance smoothly for real people, solving real problems.

It was just the same at  Internode – the company I spent more than two decades running. The ideal situation is to do things in business because you’re passionate about it. In the words of Simon Sinek: People don’t buy what you do, they buy why you do it.

I care about Redflow because I believe that Redflow’s technology can genuinely help to accelerate the world’s transition to renewable energy as a replacement to burning things to make electricity. Its really that simple.

The technical lever I designed, to help Redflow to move this particular part of the world, is the Redflow Battery Management System (BMS). I am very proud of the great work done by the technical team at Redflow who have taken many good ideas and turned them into great code – and who continue to do that on an ongoing basis.

So… while there can be a natural tendency, when looking at this sort of transition, to wonder whether my leaving the board (given how influential I’ve been at board level in the last few years) is because something ‘bad’ is happening, or because I don’t like it any more, or because I don’t feel confident about things at Redflow, the reality is precisely the opposite.

My being happy to step back from board level involvement over the next few months is the best possible compliment that I can give to the current board, lead by Brett Johnson (and now including John) and to the current executive (now ably lead by Tim Harris).  

I’ve put my money where my mouth is, to a very large extent, with Redflow. I am its largest single investor – and I have also put my money down as a customer, too, in my home and in my office.

At this point, I’m happy to note that we are seeing great new batteries turning up from our new factory. We are on the verge of refreshing our training processes to show our integrators – and their customers – how far the BMS and our integration technology has come at this point (and just how easy it all is, now, to make the pieces work). We are looking forward to the integration industry installing more of our batteries into real world situations around the world again – at last.

We do this with confidence and we do this with eagerness.

I am proud to be a shareholder in Redflow and I look forward to the next chapter of this story.

The Role of Flow Batteries in Dispatchable Renewable Energy Grids

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At the Australian Energy Storage conference held in Adelaide, South Australia on May 23-24 2018, I delivered this keynote address about the role of flow batteries and other energy storage technologies in the context of building an energy grid with renewable energy in the majority and with “Baseload” generation on the wane.

The core thematic question I posed was this: Is a future grid with large amounts of renewable energy storage necessarily using Lithium-Ion (or other, otherwise conventional) battery systems for the majority of that large scale energy storage – or are there better ways?

A specific underlying aspect of that conversation is about environmental impact – around the notion of ‘environmentally friendly’ energy generation and storage being a notion that must factor in the ultimate environmental impact for each storage technology and not just its up-front cost.

The video below is a recording of my address synchronised to the slide deck that I used.

The standalone slide deck is also available here: Hackett-Keynote-Redflow-AES2018

How Redflow Batteries Work

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I often get asked to explain how Redflow ZBM2 flow batteries work – compared to conventional batteries – and how batteries fit into your life in a home situation.

An interview I did a while back with the delightful Robert Llewellyn explains those things.

So… If that’s a subject you’re curious about, and you’d like to spend 15 minutes learning the answers… this Fully Charged show about Redflow ZBM2 flow batteries explains it !

 

The Base64 Redflow Energy System

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Updated Feb 2019: System now operating at full battery capacity and with increased solar array size

The Base64 energy system has been a fantastic learning experience for us in general and me in particular.

The system is built around a large Redflow ZBM2 battery array. We call these configurations an “LSB” (Large Scale Battery). It is charged with solar energy harvested from a large solar array (most of which is ‘floating’ above the staff carpark).

We deployed it first some time ago now, prior to having got so deeply experienced with using Victron Energy inverter/charger systems. At the time we (Base64) purchased a big custom industrial AC inverter that didn’t come with any sort of monitoring or logging system and no control system to drive it to interact properly with on-site solar.

All of the necessary energy system control, management and data logging technology comes ‘out of the box’ with the Victron Energy CCGX controller unit in a Victron installation,  so I imagined ‘everyone’ provided such things. Well, I was wrong about that.

The big industrial unit we bought came with nothing but a MODBUS programming manual and created a lot of head-scratching along the lines of… ‘now what?’. For some reason industrial scale systems are in the dark ages in terms of the stuff that Victron Energy have ‘nailed’ for the residential/SOHO battery market – they supply great, easy to use, easy to understand, effective and powerful out-of-the-box energy system control software and hardware (entered around their CCGX/Venus system). It also comes with an excellent (no extra cost) web-accessible portal for remote data logging, analysis and remote site system control.

Meantime, we were exercising our large battery ‘manually’ – charging and discharging it happily on a timed basis to prove it worked – but we were unable to run it in a manner that properly integrated it with the building energy use, for the lack of that control system in the inverter we had at the time. We didn’t want to write one from scratch just for us – that’d be a bit mad. We also didn’t want to pay someone else thousands of dollars to set up a third party control system and make it work – a major consulting project – just to do what the Victron Energy CCGX does on a plug-and-play basis at very low cost.

In parallel, and importantly – it also took ages to get substantial on-site solar operating at Base64 – and there wasn’t much point in driving the LSB in production until we did have a decent amount of on-site solar to sustainably charge it with.

To the latter point – we are in an massively renovated and reworked heritage listed building and I was unable to get permission to mount solar on the massive north-facing roof of the main building.

Instead we commissioned a rather innovative mounting system that has (at last) let us complete the installation of a 50kWp solar array that literally ‘floats’ above our staff car park on four big mount poles supporting what we call ‘trees’ – suspended metal arrays holding the solar panels up.

That system was commissioned and imported from a company called P2P Perpetual Power in California to suit our site. There are lower cost systems – but (by comparison) they’re ugly. We wanted it to be beautiful, as well as functional – because Base64 in all other respects is…both of those things.

It was worth the wait.

The result is (in my humble opinion) quite spectacular.

Including that ‘floating’ 50kWp array, we have a total of 99kWp of solar on the site, though some of the rest of it is on ‘non-optimal’ roof directions, and so on a good day what we see around 80kW generated at peak in the high (solar) season.

That said, the advantage of some other parts of the solar system being on east and west facing rooftops is that our solar generation curve runs for more hours of the day. We get power made from earlier in the day (from the eastern array) and later into the evening (from the western one) – and that’s quite helpful in terms of providing a solar energy generation offset to local demand patterns.

In parallel, we pulled the LSB apart and rebuilt it using Victron Energy products and control systems, so that we could get a fantastic operational result and have optimal use of the solar energy to drive the building, charge the batteries, and support the building load at night – the very same stuff we do in houses with our batteries, just on a bigger scale – without facing a one-off software development exercise for the old proprietary inverter system we had been using.

Swapping the Victron Energy gear in has turned out cheaper and far better than the bespoke software exercise would have ever been. It has also created a signature example of a large scale Victron Energy deployment running a decently sized multiple building site. I hope that this, in turn, may inspire more of the global Victron Energy installation community to consider the use Redflow battery technology at this sort of scale.

The battery array is built with 45 x ZBM2 = 450kWh of Redflow energy storage.

We have 72kWp of Victron inverters installed right into the container as well. We could have gone larger (in terms of peak inverter power), but these have been ‘right-sized’ to the building demand at Base64, with summer peaks normally around 60kW (75-80kW worst case) and typical draw around the 30-40kW level when the building complex is in daytime operation.

It is all linked to that 99kW distributed solar array using via multiple Fronius AC solar inverters.

I’m thrilled with how well the system is working – its a monument to all of our Redflow BMS development work that the whole thing – at this scale – really is ‘plug and play’ with the Victron CCGX energy system controller and the associated inverter/charger equipment.

It is very satisfying to run an office in the middle of a major city that typically uses very little grid energy, that is resilient to grid faults, and that even still exports solar energy to the grid as well.

A subsequent step will be to interface with a grid energy ‘virtual power plant’ operator in the future, so that we can sell battery energy back to the grid during times of high grid demand.

Every battery system on an energy grid has the potential to also become a programmable grid-supporting energy source during peak load periods. The missing links are software, regulation, and attitude – with the software part being the easiest of the three.

We can easily set up to proactively control over when the battery charges and discharges in response to, for instance, wholesale market price. The Victron control system makes that easy.  What need to give that project legs is an innovative retailer who will work with us on that and a small amount of software ‘glue’ to make it happen on our local site.

Here is a little gallery of photos of the system that we’ve installed – click through them for a little more information about the system.

 

Image from the Victron VRM portal for our site
Test run of a 15 x ZBM2 array in the Base64 LSB
72kW peak over three phases using 6 x 12kW Victron Quattro 48/15000 units.
The primary solar array ‘floating’ over the Base64 staff carpark
Main 50kWp solar array over carpark with additional arrays on other rooftops. Further solar has subsequently been added.

 

Redflow ZBM2 deployment at Bosco Printed Circuits

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A case study in complex energy system optimisation

Bosco Printed Circuits is the largest maker of Printed Circuit Boards (PCB’s) in South Africa. The production line at Bosco needs a lot of energy. The direct and indirect consequences of losing energy supply to the line are substantial.

Johannesburg, where Bosco are based, has significant issues with energy supply – both in terms of reliability and also (as a consequence) in terms of energy cost.

Like most businesses, Bosco already had an extensive solar array installation, which certainly helps with the economics of energy supply. The solar array is not sufficiently effective, is isolation, to address the complex challenges for the business in terms of supply cost and supply security.

Energy supply to Bosco from the grid utility is time-of-day based. The energy supply cost is very high during distinct morning and evening peak periods, to discourage energy use in those times. These peak time bands are periods of high energy requirement for Bosco. The are the times when the potential for grid failure is greatest and are also the periods when the consequences of grid failure for Bosco are the most severe.

Of course, these times (early morning, late afternoon) are also exactly the periods when the solar arrays can’t help, as they are outside of the solar peak generation periods.

Grid outages are expensive for Bosco. Not only do they result in lost productivity, but they also have further economic consequences in terms of partially produced PCB’s having to be scrapped when the production machines are halted without warning.

The Challenge

Bosco had a variety of business aims and objectives across their daily operating cycle that their energy system had to address:

  • To ride over transient periods of grid loss seamlessly using battery energy
  • To support the operation of the production line for an extended period (hours, not merely minutes) in the face of longer periods of grid outage, so that the company can keep working, using battery energy augmented with any available solar energy, for as long as possible.
  • In cases of a very extended grid outage (several hours), to allow the production line to be closed down with plenty of warning (at least an hour) from the point at which the shutdown decision is made.
  • To time-shift energy obtained from the low cost overnight off-peak period into the morning peak period (0600-0800), prioritising battery energy usage at this time in order to minimise the use of very expensive grid energy.
  • To also minimise afternoon peak-period grid usage by again prioritising the use of battery energy in this second daily period
  • To use the residual battery energy, harvested from overnight off-peak charging and from any excess of daytime solar power, to supply the background energy needs of the building into the evening.
  • To recharge the battery array again using off-peak power from midnight to 6am ready to commence the next daily cycle.

This need set required a battery energy system capable of consistent hard work and capable of daily 100% energy discharge, working in a hot environment, and without loss of output capacity over time.

The Solution

The solution uses 14 x Redflow ZBM2 batteries (140kWh) interfaced to a large array of Victron Energy inverter/chargers and a large solar array.

The system orchestrates this complex daily cycle of energy optimisation using the Victron CCGX and the Redflow BMS, to achieve the aims and objectives noted above.

Here’s a typical day in the life of this system, in terms of the sources of energy to run the plant:

Bosco Daily Cycle Example

Bosco Printed Circuits Energy Consumption

You can see the periods where the battery system energy (blue) is prioritised in order to minimise the use of grid energy during peak times. You can see the battery being fully utilised to supply energy during the afternoon and evening as the solar consumption falls away, and you can see the system recharging using off-peak energy again from midnight, ready for the following day.

You can use this Bosco Printed Circuits VRM Portal Link to see the live system running.

Bosco ZBM storage array

Bosco ZBM storage array (12 batteries shown – a further 2 were added later)