By Mike Stone
The aggregation of domestic battery units to provide large-scale energy storage is making headlines in the industry.
But pooling the storage potential of humble electric heaters, heat pumps and other pre-existing thermal units could also have a big role to play.
What’s vital for such a combined system are adequate control systems that optimise all aspects of energy management in the home, according to Michael Koller, energy storage specialist at Swiss utility and grid operator EKZ.
His presentation at the 4th Residential Energy Storage Forum on May 9 in Berlin, titled How to Use the Flexibility of Residential Systems Inside a Virtual Power Plant, will tackle the technical challenges in obtaining such control faces.
It’s a timely subject, as amalgamating domestic energy storage into virtual power plants (VPPs) is rapidly gaining interest as a way of providing ancillary services to the grid.
It also has big, energy-saving advantages for domestic solar prosumers. As an example, in Germany battery storage manufacturer Sonnen has effectively become an electricity retailer with its sonnenCommunity scheme.
In this model, thousands of households which already possess batteries and solar are linked up.
Sonnen soon hopes to provide lucrative primary frequency response services to the grid, whilst allowing domestic solar prosumers to trade excess energy and thus cut their energy costs.
Utilities such as E.ON in Germany and AGL Energy in Australia and other players elsewhere are also getting involved with pilot schemes and actual functioning VPP models currently in operation.
In fact, despite its currently marginal status in the energy ecosystem, research from Bloomberg New Energy Finance predicts that 66% of all storage will be behind the meter by 2030, compared to just 16% at present.
Battery energy storage only
These figures account for battery energy storage only. Yet despite the falling costs of domestic battery storage as mass production of units ramps up, batteries are still an expensive option for most households.
And despite a lot of interest and some uptake, the case for battery storage is still quite a tough one to make in most territories.
More is needed, according to a report published last year with the support of the German Federal Ministry for Economic Affairs and Energy.
The Merit Order for Energy Storage Systems 2030 study ranks various storage technologies.
It states: “Power to heat in public and industrial district heating systems as well as flexibilisation [sic] of load in industrial processes offer the largest benefit on the transmission level from a system perspective.”
Untapped potential storage capacity
In other words, the untapped potential storage capacity of water heaters rather than domestic batteries is the future of energy storage in Germany.
The report is not without its critics, but it does indicate that thermal storage is a potential force to be reckoned with.
Koller agreed that everyday equipment such as heaters and heat pumps will have an important role to play in behind-the-meter storage.
He told Energy Storage Report that EKZ has already amalgamated industrial thermal units to provide VPPs, and was interested in looking at domestic storage that incorporates heating elements.
To do so effectively would present several challenges, he said: “What’s needed is a holistic approach within homes which accounts for all aspects of the household energy production, storage and consumption.”
“You need a PhD to do it”
Such a system can be built from existing devices, but “you need a PhD to do it,” Koller pointed out. EKZ itself is “too small” to spend the amount of money required on research and development, and is looking for suppliers.
In his presentation at the Residential Energy Storage Forum, Koller is expected to explore what these suppliers would need to achieve to manage everything from solar to storage and heating, and maximise the return on investment.