The launch of the Tesla Powerwall in April 2016 was the start of a rush of interest in battery storage technology.
The Powerwall is a rechargeable lithium ion battery system rated at 6.4 kWh of storage capacity with a 10 year warranty.
It retails at $3,000, with installation costs targeted at $500. A household in the UK uses around 3300 kWh per year or 9 kWh per day.
The Tesla Powerwall should be able to power it at night with its 6.4 kWh of capacity.
Battery storage itself is not new, and Germany has led the way for several years in its renewable energy transition.
As of 2015, 1.5 million photo-voltaic (PV) power plants have been installed in Germany, of which 35,000 are hybrid PV and battery system.
Using a battery increases the amount of electricity used from own-generation from 30% to 60% and 50,000 PV-battery systems could be installed a year by 2020.
Younicos, a Berlin-headquartered, private equity backed energy storage startup built the first commercial battery park in Europe for Wemar AG – the German green utility in 2014. The park has a rated power of 5 MW and a peak capacity of 5 MWh.
It is fully automated, used to stabilize grid frequency and is connected to a 110 kV substation.
The park houses 25,600 lithium-manganese oxide cells guaranteed for 20 years by Samsung SDI.
Younicos’ experience in the chemistry of batteries, the rack systems to store the batteries and on-board Battery Management System (BMS) software at its €15m, multi battery test site helped it become the only system so far to get a 20 year warranty from a major battery producer.
Younicos also has an insurance agreement where a battery will be replaced and 97% of any lost revenue will be protected.
There are 327 projects, making up 869 MW of lithium ion battery storage capacity operating worldwide as of May 2016. In total, there are 921 electro-chemical projects in various stages with a total capacity of 2,708 MW.
The main types of batteries used in energy storage are lead-acid, lithium-ion, sodium sulphur and flow batteries.
Lead-acid batteries are the most widely used rechargeable batteries. They are cheap, respond quickly, don’t lose power while not being used and are efficient.
But they use old technology and perform less well than lithium ion in cold weather. As a result, they are not used much for energy storage applications around the world.
Lithium Ion batteries respond quickly, within milliseconds, are light and efficient.
But they need on-board controls to maximise their lifetime and to operate efficiently. They can be used for grid balancing and frequency response applications.
Sodium-Sulphur batteries hold a lot of energy – they are energy dense, lose virtually no power when standing, non-toxic and recyclable and have a higher capacity than most other technologies.
They run very hot, however, at temperatures of 574 – 624k with molten electrodes which increases their operating and management costs. They can help to match power demand and supply over time.
Vanadium-redox-flow are efficient, can respond quickly, and discharge over more than 24 hours, making them good for long term storage applications.
Control software that can control every generator in a microgrid, from PV to diesel generators will be crucial to optimizing the performance of the system and extending the lifetime of the batteries.
Who is leading the market in grid connected battery solutions?
Five companies to watch, according to Chet Lyons, a consultant with over 30 years of experience in commercialising advanced energy solutions and author of Grid-Scale Energy Storage in North America 2013: Applications, Technologies and Suppliers, are:
- ABB: A global leader in power technology, with a 40MW nickel-cadmium system in operation.
- AES Energy Storage: Operates 86 MW of energy storage and has the largest fleet of battery storage assets.
- Convergent Energy Power: Small, but a contender with finance and construction capability
- EOS: An innovative company getting interest from utilities and a low cost zinc-air energy battery.
- S&C Electric: Lots pf practical experience for large scale projects and delivering turnkey solutions.
- SEEO: High energy lithium-ion batteries with backing from VCs like google.org and Khosla Ventures.
The challenge with batteries are storage capacity, cost and how long they take to recharge.
How much do batteries cost?
The cost of battery packs for electric vehicles has fallen from around $1,000 per kWh in 2007 to $410 per kWh by 2014, a reduction of nearly 60%.
The biggest manufacturers can get costs down to $300 per kWh.
Take a look here for a worked model with some of the issues that you might come across.
Examples of proposed and installed battery storage systems
The “Energy Neighbor” project at Moosham, is a 200 kWh system installed in Spring 2016.
The system has 8 racks, each of which has 13 battery modules with a battery management system and power electronics. Each battery module has 192 battery cells. Each rack has a capacity of 25 kWh, which means the capacity can be increased in 25 kWh steps by adding a rack to the system.