10th May 2019

How can you and I use our own and each other’s energy resources to lessen our exposure to severe weather events?

Climate change is already causing destructive impacts to electricity systems in Australia as elsewhere in the world.

These impacts range from ones we know well, like fallen trees landing on power lines and sparking bushfires, to ones we haven’t experienced here yet, like masses of jellyfish clogging the water intakes of coastal power plants (yes, really).

With no serious policies in place to guarantee a safe climate, these impacts will only accelerate over time.

In response, it is now widely recognised that we need to think more about system resilience rather than just reliability.

Reliability is a systemwide concept; it doesn’t drill down to individual properties, and it doesn’t tell you what you can do to improve your own ability to bounce back after severe weather.

Here is an example.

The electricity network of Puerto Rico is being rebuilt after the devastation of Hurricane Maria in 2017 with a new emphasis on microgrids and mini grids, because its government recognises that they offer greater resilience than a system dependent on either a single transmission backbone or a fully distributed system.

What do we mean by resilience? Here’s how Energy Networks Australia defines it:

“Climate resilience is the ability of a system to absorb climate-related disturbances while retaining the same basic structure and ways of functioning.

“With respect to network assets this refers to the ability of assets to absorb climate related impacts but still retain adequate, reliable and safe functioning.”

This definition makes a lot of sense. To date, though, the concept of a climate resilient energy system has been applied mostly to network infrastructure: transmission and distribution poles, wires and substations.

The focus has been on maintaining reliability.

But the boom in home solar and batteries and interest in off-grid-capable systems is evidence that more Australians want to take control of their own energy supply and want insurance in case the main grid goes down.

I haven’t come across any way of measuring resilience. It just seems to be assumed that everyone knows what we’re talking about. As I see it, there are a few things that contribute to system resilience apart from reliability:

• Toughness — you want kit that has been engineered to withstand extreme weather (eg by undergrounding power lines).
• Flexibility — you want the ability to adapt to changing conditions (eg, by detecting and self-repairing faults).
• Redundancy — so if one source of supply goes down, another is available.
• Upstream/downstream capability — that is, backup at a different level of the system, to overcome localised problems.

Below is my first stab at constructing a metric out of the last two of these four factors.

Unlike reliability metrics, it is focused on individual customers rather than the system as a whole. The x axis is about generation and storage, and represents degrees or levels of redundancy. The y axis is about networks, and represents the level of connection.

My working hypothesis is that for more resilience, it is better to have multiple sources of supply, and to be connected at more than one level of the system. So, to give you just 3 examples…

1. Top left: Bog standard grid connection, no DER kit—one level of grid connection; no backup supply.
2. Bottom middle: Offgrid system—also one level of connection; a genset provides backup supply for periods when the sun doesn’t shine and the battery has run down.
3. Middle right: Islandable microgrid—the sweet spot is around here, where you are on a microgrid and you have both upstream and downstream connections (so you can still have power if 2 levels of connection go down); and the combination of wind, solar, battery and a genset means you still have power if one or more sources of generation or storage is unavailable.

I can envisage a time when, alongside home energy star ratings, there might be household energy resilience ratings.

This will help buyers and owners to get a handle on the ability of a property’s energy supply to withstand or bounce back from the localised impacts of a bushfire, heatwave, flash flood or storm.

Now, let’s look at how another factor, flexibility, might contribute to system resilience. There is one emerging technology that will leapfrog all these levels and stages.

If you have an electric car that can feed power back into the grid, then suddenly you not only have a backup supply source; you can potentially provide power to households that are offgrid and on a microgrid as well on the main grid—not only your own house but your neighbours, too.

That makes a full three levels of connection, and an extra layer of redundancy.

It is not surprising that vehicle to grid (V2G) technology emerged first in Japan. It was a response to the Fukushima nuclear power crisis.

Again, it was all about resilience. The new Nissan Leaf is apparently the only EV coming to Australia in the near future with V2G capability, but I am betting that in 5 to 10 years V2G will be standard kit on EVs.

For some households it might even replace the need for a separate home battery.

So, what difference would it make, having a metric like this in our toolkit?

I’m in the middle of a study on the role of DER in climate change adaptation.

We’re going to survey solar, battery and EV owners and others interested in local energy solutions about what they are doing or plan to do to reduce their exposure to current and likely climate change impacts.

We suspect that lots of them will say that they plan to get a big battery (on top of an oversized solar system) and then disconnect from the grid to improve their reliability and autonomy.

But a resilience focus will probably tell them that they would be better off staying connected to the grid while having a system that can continue to operate if either the main grid or their own system goes down. Or just get an EV with V2G capability.

It is also likely that sometime soon energy market regulations will change to recognise the public and private value of climate resilient local grids.

For instance, if your house is part of a local microgrid that can work in islanded mode when the main grid goes down, that places Iess stress on the main grid, which translates into an economic saving across the system.

You’ve done everyone a favour, in other words, by taking care of yourself—accidental altruism at work.

That is just one of the values of local energy products and services that are likely to be recognised in a more dynamic pricing regime in the near future, just as smart inverters and batteries can provide voltage and frequency services as well as energy supply and storage now.

More on that next time.

(Source)