Phelas: The Flexible Liquid Air Energy Storage Container Backing Up Renewable Power

© Phelas
Phelas' prototype miniaturises a liquid air energy storage system into a single shipping container.

Renewable energy is better for the environment than fossil fuel alternatives, but is it always best for business? One German startup hopes to make it a more robust option, with the help of an innovative and reliable renewable energy storage solution.

Author Mark Newton, 05.12.21

Translation Mark Newton:

Environmental issues, civil society movements and concerns about energy security have all prompted heavy investment in renewable energy in recent decades. For example, in 2004, around 50 billion USD were invested annually. By 2015, that figure had increased to over 250 billion – with China in particular seeing the largest expansion.

However, renewables – from a business perspective – still present challenges to investors and energy producers. Firstly, they often feature higher startup costs and a longer period before they start to become profitable. Secondly, the intermittent nature of some renewables – such as wind and solar – means being able to store power is of critical importance. Currently, this is largely achieved through the use of lithium-ion batteries, which come with environmental concerns of their own. And lastly, the effectiveness of renewables may be hindered by their geographic location.

To address some of these concerns, a new Germany-based energy startup, Phelas, is looking at new and innovative ways of reinforcing the renewable energy market through Liquid Air Energy Storage (LAES) solutions. Established in 2020, Phelas has developed a prototype – the Aurora thermodynamic storage device – a simple and resource unintensive energy storage solution that can fit into a standard 12 by 4 metre shipping container.

What is Liquid Air Energy Storage?

Liquid air energy storage – also known as cryogenic energy storage – has actually been around for some time. In fact, a liquid air car had originally been patented as far back as 1899. However, both governments and electricity producers are looking at the technology as a way of reinforcing power stations.

The process works like this: During times where electricity is abundant, surplus power can be used to cool air from the atmosphere to around -195 degrees celsius. Once at this temperature, the air becomes liquid, vastly reducing its volume to around one-thousandth of that of the gas.

This liquified gas can then be saved until it’s stored potential energy is needed. When this is the case, the liquified air is evaporated into a gas through the use of the ambient air temperature, or industrial waste heat. The resulting expansion of the liquid into a gas builds up pressure and drives a turbine. The efficiency of the process can be greatly increased through the use of a cold store, such as a large gravel bed, which can capture the cold generated by the evaporation process and reuse it.

Phelas founder Justin Scholz spoke to RESET and explained some of the advantages that LAES has over traditional batteries:

“Phelas’ Liquid Air Energy Storage (LAES) offers many features that cannot be covered by conventional technologies. We use air and gravel as the main storage medium – both materials are universally available and, unlike lithium-ions, less hazardous and less resource-geographically dependent. The technology offers a decisive cost advantage for large amounts of energy, with, at the same time no cyclic degradation and excellent environmental compatibility.”

Currently, experiments with LAES in countries such as the UK and US are mostly concerned with building large, expensive facilities attached to existing power stations. With Aurora, Phelas hopes to provide more flexibility and simplicity to the technology:

“The distinctive feature of Phelas is the modular, containerised approach, which fundamentally differentiates it from existing LAES approaches on the market, as conventional LAES plants are based on large air liquefaction plants. The modular approach allows a greater flexibility in the application. This way we are able to address smaller applications, e.g. for small industries or renewable energy plants.”

Primarily, Aurora is aimed at renewable energy developers and operators who may be facing several issues, such as declining market revenues due to dropping energy prices during times of high output – known as “price cannibalisation”. By cheaply storing some of their power, it can be retained for later periods when power is in high demand. Additionally, it can also prevent energy congestion by filtering some into storage and preventing power bottlenecks, as well as generally increasing industry confidence in volatile electricity markets.

Technology such as Aurora could also have applications for off-grid power generation, especially in areas where building a larger power plant or storage device is not feasible, aiming to replace diesel generators, which are typically used to provide reliable off-grid power supply.

Overall, a single Aurora LAES system consisting of at least one power module has an electrical charge/discharge capacity of 1.5 or 1.2 MW, and an electrical storage capacity of 2 MWh.

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