Currently we are the only manufacturer of this technology in Bulgaria, our stack is the most efficient on the world market.
Storing electricity in battery systems is becoming increasingly necessary, not only for renewable energy producers faced with low daytime electricity prices, but also for maintaining the stability of the electricity system. While lithium batteries dominate the market, there are better alternative solutions. One Bulgarian company, Monek Bulgaria, has implemented energy storage for its own needs and has started development of a plant for the production of vanadium redox flow batteries.
- Mr. Gradev, what company is Monek Bulgaria from Kardzhali?
– This is an enterprise with a 70-year history that has traditionally served the mining sector. Currently we are the only manufacturer in Bulgaria of specialized equipment for mining and mining-processing enterprises.
- How did the project for a vanadium battery plant to store electricity from solar and wind come about?
– The idea arose during the development of a new production that turned out to be extremely energy intensive. We realised that a significant part of the value of the final product depended directly on the cost of electricity, which was a major challenge.
“Monek Bulgaria is part of the holding CSIF. We have wind and photovoltaic capacities, wind farms and we decided to implement battery storage. We started to analyse the economics of the different technologies, but the data was not promising. Despite the high-tech nature of lithium-ion batteries, their life cycle is limited by the number of charge-discharge cycles. The best manufacturers claim that they can achieve up to 8000 cycles, but under strict conditions – the battery must not be fully charged from 0% to 100%. If full capacity is used, the number of cycles is halved.
CSIF is Bulgaria’s green holding company, every company in the group has a strategy to reduce its carbon footprint, our bank considers and finances green projects with priority. We were faced with the issue of recycling these batteries, and the process is extremely complex and expensive and in itself poses a serious environmental risk.
This led us to look for alternatives. With our team of engineers, we began an exhaustive study of all available energy storage technologies. For six months we consulted with universities in the USA and Scandinavia, with companies in Australia and China. After a detailed analysis, vanadium redox float technology turned out to be the best choice.
- What are the advantages of this vanadium battery?
– They are significant in every respect. First of all, the life cycle is not measured in cycles. It can be charged and discharged an unlimited number of times, even at 15-minute intervals, without affecting capacity. Unlike lithium batteries, which lose capacity over time, the loss with vanadium technology is minimal and can be compensated for with additives to the electrolyte. If you buy a battery with certain parameters today, they will remain the same in 30 years’ time.
- How much is her life?
– In theory, with proper service it is unlimited.
The concept of the battery is fundamentally simple. It uses two vanadium electrolytes with different oxidation states stored in separate tanks. The active cells are separated by a membrane – think of them as cellophane through which the electrolytes circulate. In one mode the electrolyte changes its oxidation state, in another it returns to its original state. If the membrane fails, it can be easily replaced. The same applies to the pumps. The electrolyte is liquid and does not degrade, with 67% of its composition being water, eliminating the risk of ignition. This allows the batteries to be installed even in residential buildings.
We solved our problem, but we realized that it is common to all RES producers. So we came up with the idea to develop our own production. We formed a strategic partnership with a leading Chinese company that has the team and years of experience. We also cooperate with Chinese universities. Currently, our stack is the most efficient on the market.
- What is a stack?
– This is the heart of the battery – the facility in which energy conversion takes place by changing the oxidation rate of vanadium. We can also call it a cell. We are years ahead of the competition on this metric.
We registered the VESS (Vanadium Energy Storage System) brand, built a team and are now demonstrating a working battery in Kardzhali. The interest has exceeded our expectations – we are receiving many inquiries and orders.
- At what level is your project to produce such batteries in Kardzhali?
– We are already making sales since the beginning of the year. We have upcoming deals for 27 batteries with a total capacity of 10 MW and a capacity of 60 MWh.
Currently the main components are supplied from China and assembled in Bulgaria. Some components are manufactured locally and the electrolyte tanks are made by a partner in Turkey. We are also in the process of validating a supplier from Poland.
We are developing several parallel projects:
First stage – VESS brand registration and sales launch (completed). Second stage – start of electrolyte production by January-February 2025 (no such production in Europe yet). Third stage – start of cell production by June-July 2026.
We act step by step to ensure quality. When we are confident in the sustainability of the product, we will scale up. Our goal is to have full production in Bulgaria with a capacity of 100 MW per year for cells and 5000 m
- Is there capacity to produce everything in Bulgaria?
– Absolutely. Bulgaria is a wonderful place with many smart and good professionals and this should not be forgotten.
- What's your vision - is each project going to be about yourself or are you going to unify?
– It depends on the client. We offer three concepts:
- Classic – battery with electrolyte tanks.
- Container – modular system for quick installation.
- Scalable – large installations (e.g. a battery building for a government project in the Middle East that we developed at the beginning of the year).
We standardize on container solutions for their flexibility, as well as the 1:6 (power to capacity) model. This means that for 1 MW of power, the capacity is 6 MWh – a model that is most in demand by large PV contractors.
How the vanadium energy storage system produced by VESS works
- Electrolyte solutions containing two different oxidation states of vanadium (V2-/V3- and V4+/V5+) are stored in two separate tanks.
- The solutions are transported to the active cells via a pump system.
- In active cells, energy is stored or released through chemical reactions between electrodes. Electrons are transferred during oxidation and reduction reactions.
- Protons are transferred across the membrane into the cell, thus balancing the processes of energy storage and release.
Technical specification
- It has unlimited life;
- Charging and discharging from 0 to 100%;
- Degradation capacity - less than 1% after 30 years;
- Permissible outdoor operating temperature: -20 to 55 oC;
- Optimal humidity for operation - from 5 to 95%;
- Capacity ratio - unlimited.
