With the small-scale energy storage market starting to take off alongside the growing levels of renewable generation in countries around the world, key questions for distribution system operators (DSOs) are how this storage can be optimally integrated and the value it can add to the distribution grid.
The right storage technology must be selected for the particular use case. In addition, the flexibility within this storage must be available to the DSOs to manage their networks and the players in that value chain appropriately rewarded.
The STORY project, which was initiated in 2015 and runs through to 2020, is set to provide some answers from the European perspective.
Supported from the Horizon 2020 research and innovation programme, the project involves 18 companies from eight countries, including Elektro Gorenjska from Slovenia as the DSO participant. It is focused on demonstrating innovative approaches for thermal and electrical energy storage systems to find affordable and reliable solutions that lead to increased electricity self-supply.
Energy storage demonstrations
The heart of the project is a series of demonstrations with different small-scale storage concepts and technologies in various residential and industrial settings.
Case studies one and two are demonstrations at residential and neighbourhood scales in a street in Oud-Heverlee, Belgium. In the first phase homes were equipped with a range of technologies to maximise the load shifting potential, including fuel cells, batteries, small scale thermal storage and seasonal thermal storage. In the second phase currently underway, these homes are being brought off-grid through the creation of a microgrid.
These demonstrations are aimed to contribute to determining the value of storage for the participants, i.e. the end user, DSO, energy provider and potential third party aggregator.
Case study three comprises demonstration of solar PV and lithium-ion battery storage in a factory in an industrial zone in Navarra, Spain. The target is to reduce dependence of the facility on the distribution network.
Storage in a residential district is demonstrated in case study four, taking place in Lecale, Northern Ireland. The focus is on compressed air storage and stored heat in order to demonstrate the ability to store and re-generate electricity with standardised technology components and to validate models that both maximise the penetration of local renewables and minimise the network reinforcement requirements.
Case study five comprises demonstration of a medium scale (800kW/660kWh) battery system in a variety of settings – behind the meter at a factory in Germany and connected to an MV/LV transformer station and an LV industrial grid respectively in Suha and Kranj, Slovenia.
Case study six is a demonstration of a multi-energy grid including a wood-fired boiler connected to an Organic Rankine Cycle, and hot water and battery storage in an old industrial area in Olen, Belgium.
Storage impact assessment
Together, these demonstrations are designed to represent a good mix of market driven and regulated, i.e. grid driven, implementation of storage, according to the project consortium.
Their outcomes will be fed into a large-scale impact assessment and further analysis on market models, policy and regulation.
Among early findings from the project is the importance of interoperability. Both the implementation and control of storage systems are key challenges, with the need to integrate and operate a plethora of devices which come with different data exchange formats and protocols.
Energy storage regulation
The project also has highlighted the importance of regulation, which in Europe is currently under indication in the Clean Energy Package.
The project consortium cites the Spanish demonstration as an example. Current self-consumption regulation in Spain establishes significant restrictions on the operation of energy storage systems in self-consumption plants connected to the grid.
A ‘grid support toll’ reduces considerably the benefits and savings of the plant. It is possible to connect such self-consumption plants with storage without energy delivery to the grid and storage charged from the grid. However, this constrained mode of operation limits the available added value of the storage and makes the system cost-ineffective.
Preliminary results from the demonstration indicate that even with the regulatory restrictions applied, both the peak power can be reduced by about 20% as well as the energy consumption from the grid during peak hours to achieve overall savings of up to 8%.
Estimates from simulations with an advanced energy management strategy allowing the battery to charge from the grid suggest that power peak reductions of up to 50% in peak hours and overall savings up to 20% are possible. However, such results could only be achievable with relaxation of the regulations.