The Eco-mc2 compressed air hydraulic energy storage system could revolutionise energy storage in South Africa. A winner at the WWF Climate Solver Awards earlier this year, a top five finalist in the Eco-Innovation category of this year’s Eco-Logic Awards and a top 10 finalist in the Global Cleantech Innovation Programme, its application is particularly relevant for renewable energy where conventional battery storage is thought to be expensive, bulky and environmentally toxic.

“The technology isn’t new. I’ve basically put together various technologies that have existed for many years, to come up with the Eco-mc2,” says Warwick Leaper, owner of Leaper Innovative Green Energies (LiGE).

The technology

Compressed air energy storage, used in the Eco-mc2, is a method of storing energy generated at a particular time for use at another time, by using air that has been compressed. In the case of the Eco-mc2, the type of air compression used for storage is referred to as isothermal compression.

Isothermal compression (compression at a constant temperature), allows air to reach high pressures without the inherent challenges of high temperatures or high thermal losses. Compressed air at near room temperature can be stored for later use with minimal heat and energy losses.

To achieve this isothermal cycling, Eco-mc² combines patented innovations with a design based on mature industrial components and principles. A hydraulic system and drive train uses an electric motor and AC generator (alternator), to provide an efficient mechanical link, which powers the compressor and heat-transfer system process into pneumatic cylinders.

During compression, the air is cooled via absorbers. The resulting air is collected in pressure cylinders. Heat is transferred from the stored “heat battery” to air during expansion or from air during compression, providing both isothermal compression and expansion, eliminating the cost of separate compressor and expander subsystems.

This patented approach achieves high round-trip efficiency, proven long lifetime, and lower cost, allowing Eco-mc² to deliver a low “cost of energy” in comparison to competing storage technologies, says Leaper.

Application of Eco-mc2

The product has a modular design, meaning capacity can easily be expanded, from units as small as 40kW, which is sufficient for a medium-sized home, to up to several MW, applicable to larger energy users such as businesses and large industries. The 40kW unit is 2m x 2m x 2m, with the 1MW unit measuring 6m x 6m x 6m.

This storage option is ideal for solar photovoltaic technology, for example, when electricity production is usually high during the day when the sun shines (and there is unused electricity) but non-existent at night, when electricity is also required. The Eco-mc2 batteries hold charge indefinitely (when compared to about 10 hours for conventional batteries), allowing users to maintain their lifestyles without having to balance the use of various appliances, Leaper says. In addition, Leaper says, the life span of the Eco-mc2 is about 30 years, which is superior to regular storage solutions.

“As time goes on, regular batteries start to lose their energy and storage capability even without being used,” he says. Designed mainly as a solution for off-grid renewable-energy systems, the Eco-mc2 also fits the application of an uninterrupted power supply environment, which allows for a greater storage period.

The value of the 40kW system has been calculated at about R300 000, which is a large up-front capital cost, (also available as a rental option) but Leaper is more concerned about the levelised cost of ownership (LCO) over the lifetime of the system, which is superior to other storage systems, he says.

Leaper says over five years, conventional battery systems cost $0.5479/kW. Over the same period a diesel generator’s LCO over the lifetime of the system is $1.1504/kW. The Eco-mc2 LCO over the life-time of the system is $0.07305/kW.

In spite of the innovative design and potentially game-changing nature of the system, LiGE has struggled to source funding for the project, and the project design costs have been entirely self-funded. “It is very difficult for entrepreneurs in South Africa and not enough financial support is provided to inventors,” notes Magriet Leaper, co-owner of LiGE.

Still a new product, Leaper has one ratified deal with a client, to provide the Eco-mc2 for five years, at three units a day. In addition, a letter of intent has been signed with a leading solar installer for 450 units a month. “This shows interest, adoption and willingness to get off the grid by many people,” says Leaper.

Deon Govender, renewable energy expert and CEO of consultancy DLink Holdings, says the technology used in the Eco-mc2 compressed air energy storage is not new, citing decades of use in the mining industry. “What seems to be new is the ability of the Eco-mc2 to be scaled to domestic or commercial applications, and secondly its claimed storage cycle,” he says.

Describing it as an “exciting innovation given our current electricity challenges and the country’s GHG emissions reduction targets”, Govender notes some of the challenges could be how the Eco-mc2 will deal with heat exchange issues in larger scale applications. Leaper concedes heat exchange is an important factor but says this is very well controlled in the Eco-mc2 and used both as energy and as heating.

Other challenges might relate to those experienced by any ground-breaking technology. “It does seem that Eco-mc2 will face the same challenge all new technologies do when first released to the local market i.e. pricing and general reluctance against early adoption,” explains Govender.

Though no large deals are yet confirmed, the Eco-mc2 continues to gain traction and has been recognised with several innovation honours. Realising the potential of uptake in the product, LiGE has signed an agreement with an agent to help market the product and facilitate deals in South Africa and Africa. On pricing, Leaper says compared to Tesla’s Power Wall, the Eco-mc2 is more economical and costs ten times less.

A large deal is on the cards, which could see the system being used to power telecommunication towers across the country. If this is realised, LiGE plans to set up an assembly factory in Atlantis, Cape Town, and hopes to provide the storage system across the country. The choice of site is based on the various incentives offered in the Atlantis development zone, particularly those offered to greener industries. Leaper cautions the tower deal is still very much in the offing but if secured will provide a massive boost for the product and a much needed leap for the energy storage sector in South Africa.

By Jonathan Ramayia

For the full article, see earthworks magazine Issue 29, December 2015/January 2016.