Second-Life Batteries to power the electrical grid 

Expert opinion

Salim EL HOUAT, President at Mob-Energy
Published on:
Updated on:
visuel principal article blog MobEnergy

A decarbonized world = a 100% electric world

When we talk about "decarbonizing our world," we often forget to mention the massive electrification that lies ahead. The end of fossil fuels and thermal engines inevitably leads us towards a "100% electric" world.

Take mobility for example: 31% responsible for greenhouse gas emissions in France, there is an urgent need for an immediate and strong response. The electric vehicle is a possible first step. But we don't talk much about the behind the scenes linked to the hundreds of thousands of very short-term terminals in France to be able to adopt it.

And a charging station consumes a lot. A lot of copper, but also a lot of power.

This electrical power is provided by operators of the electrical grid: first, between energy production facilities and cities (broadly speaking), thanks to RTE in France, and then to each building, thanks to Enedis in France.

But charging stations are not just a "simple plug": each one requires heavy construction work and significant connections. Even though we are only at the beginning of this "electrification" (barely over 1 million electric and hybrid vehicles, less than 5% of electrified vehicles), power shortages are already becoming apparent in many parking lots. And here's why:

Did you know : A city apartment traditionally has a subscribed power of 6 kW. 6 kW is the power of a so-called "normal" charging station: you get about 40 km of range in an hour of charging. So, plugging in a "normal" charging station in a parking spot is like "creating" a new apartment from the network's point of view.

To complete the assessment, it is important to note that there are actually two phenomena that add up in the electrification imposed by our decarbonization efforts:

  • New electrical consumption: such as electric vehicles, and their charging stations… 
  • But also, new electricity production: linked to the production of renewable energies, which must also be connected to the electricity network.

Both create very significant pressure on the electricity network. And sometimes pulling the cables isn't enough. This is where the Lithium-Ion battery comes in.

The Lithium-Ion battery serving the electrical grid

Since its industrialization in the 1990s, and despite its complexity – linked to the electrochemistry inherent in each battery – the Lithium-Ion battery has established itself as a reliable and efficient technology.

Beyond its usefulness for on-board systems (computers, telephones, electric cars, etc.), the electrochemical battery has found itself, for around fifteen years, in a very particular universe: that of supporting the electrical network.

In the universe of batteries serving the grid, we distinguish two sectors:

  • Behind-The-Meter (BTM) Batteries: “relatively” small batteries, installed directly within a building, “after the meter”.
  • “In-Front-of-the-Meter” (FTM) Batteries, or “Utility-Scale”: industrial batteries, installed upstream of the meters, directly connected to electricity transmission lines (managed by RTE, for example).

FTM Batteries

For around twenty years, huge “FTM” energy storage units have been deployed on renewable energy production sites. Their usefulness is multiple:

  1. Maximize the efficiency of renewable production units, often intermittent;
  2. Participating in grid regulation services, in frequency for example;
  3. Provide “connection” facilities to the electricity network: by acting as a virtual High Voltage line (“Virtual Power Lines”)

Source: Energy Central

With the emergence of these solutions, new professions have also appeared: aggregators. For around ten years, these players have been “aggregating” batteries to make “Virtual Power Plans” (VPP, always and again acronyms…). These aggregators develop algorithms capable of participating in several services, several markets, etc. Like Tesla's Autobidder.

Did you know : THE Utility-Scale Batteries intervene in the context of phenomena often unknown to the general public. For example, they make it possible to reduce the negative effect of daily production peaks from solar power plants. We call this phenomenon the “Duck Curve”, and rather than explaining it in writing, I invite you to watch this content, much more descrptive. Another phenomenon: “Black Start”, the name given to the procedure aimed at getting an electricity network back on its feet after a complete breakdown. You can find out more about a project led by Enedis .

“BTM” Batteries

In parallel with these large industrial batteries, smaller batteries more integrated into the urban environment are developing directly in cities. They are installed "after the electrical meter" and play essentially the same role as the large batteries, but in a distributed/decentralized manner.

Initially, “BTM” batteries were mainly deployed for energy back-up services: batteries capable of activating very quickly to take over in the event of a blackout, particularly on critical installations (data center, telecommunications antenna, etc.) . We talk, wrongly, of “inverters” in the industry.

But with the massive advent of solar panels (x5 in 10 years, see graph below), the BTM battery has developed with the economic logic of reducing energy bills:

  1. “Buffer” storage solution for solar panels: a battery capable of storing (then releasing) surplus energy production, and therefore benefiting from it;
  2. Storing energy during off-peak hours, to reuse it during the day.

Source: France Territoire Solaire (based on figures from Enedis and RTE)

But in a context where power is lacking, the usefulness of using batteries to strengthen the electricity network locally (microgrids). The notion of “Virtual Power Lines” then takes on its full meaning.

Let's take an example : a company wants to install 20 charging stations in its parking lot. It needs to allocate 20 x 7 kW: 140 kW[1]. The problem is that the building no longer has available power and must release some. Rather than embarking on new power creation work, the company can deploy a storage unit which, in addition to storing possibly cheaper energy, can also provide additional power to the network.

Source: Mob-Energy

It is this utility that we find in the Eiko power cube : a solution that we designed. The Eiko cube is a “BTM Battery” type system: it contains up to 150kWh of battery and interconnects to charging points. It can deliver up to 60kW of power thanks to the energy it stores when the vehicles are not there. The battery therefore serves as power capacity.

Source: Mob-Energy

With the Eiko cube, it is possible to deploy more quickly, with 3 times less copper, almost no civil engineering, and 10 times less power allocated on the building's grid. Eiko thus constitutes a true "Battery Behind-The-Meter," based on three pillars:

  1. A redesigned local electrical architecture, with interconnected charging points in series and advanced load distribution per point, to minimize the power allocated to the building.
  2. Energy storage, to store energy when vehicles are not present (often cheaper, with off-peak tariffs, for example).
  3. Knowledge of the energy needs of each user, as well as their parking times, to be able to seriously manage the two energy sources: the network on the one hand and the battery on the other.

Batteries: yes. But of Second-Life Batteries.

Lithium-ion batteries, whether of significant size (FTM) or smaller, integrated into buildings and urban installations (BTM), are a key to accelerating the electrification of our activities.

But, batteries have a cost: financial and environmental.

While the ores are extracted mainly in Australia, Argentina and the Democratic Republic of Congo, the cells (batteries) are almost all manufactured in China and South Korea. 75% of the carbon footprint of a freshly produced automobile battery is built on these phases, to reach around 70kg of eCO2 / kWh.

With the advent of electric vehicles, a phenomenal quantity of used batteries is found on the market: batteries too old to continue their automotive life, either damaged, or ultimately unsuitable (defect, recalls, tests, etc.). However, they can be perfectly adapted to network support applications.

It is in this context that it becomes urgent to recondition them on an industrial scale.

This is particularly the case of Mob-Energy, which decided to manufacture its Eiko power cubes based exclusively on the reuse of used batteries.

Source: Mob-Energy

In conclusion

  • A carbon-free world is a much more electric world than today. And developing the electricity network to meet new needs (1) and new production (2) is not trivial.
  • Batteries, notably lithium-ion, can be used to reinforce the grid. They can notably play the role of "Virtual Power Lines" and avoid the need to deploy new high-voltage lines.
  • They are classified into two categories: industrial batteries "Utility-Scale", located before the meters and directly connected to RTE's network, and more urban batteries, "Behind-the-Meter", installed directly at the individual's or company's premises.
  • When it comes to deploying charging stations for example, solutions like Eiko are a key example: a 150kWh battery connected to a cluster of charging points in series, capable of operating 20 charging points with 10 times less power and 3 times less copper.
  • Finally, the reconditioning of second-life batteries is an absolutely vital aspect of the widespread use of batteries in the grid: in addition to lowering costs, this circular approach significantly reduces their carbon footprint.

[1] In reality, the charging stations never operate at the same time, nor at maximum power. But this subject will have to be discussed in another article…

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