Tech Talk | Advancing flexibility functions in ELEXIA

The EU co-funded project ELEXIA has reported advancing flexibility functions to model not only prices as inputs but also other variables such as temperature or time of day.

With flexibility a key solution to integrating and managing the intermittency of variable renewables such as wind and solar, there nevertheless remains a series of challenges in its implementation.

In order to address some of these the ELEXIA project was formed, aiming to advance the technological readiness of this and other tools and their combination into a digital platform for the planning and operation of local energy systems.

For example, one important open question is quantifying the amount of flexible energy within an energy system, an ELEXIA report states.

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Traditionally flexibility is quantified by metrics such as activation time, peak demand reduction, shiftable load or cost savings. While such metrics were developed for power grid applications, their application to e.g. buildings is more complex, as their demand profiles are influenced by a wide variety of factors, including the difficulty to predict human activity therein.

Furthermore, the application of previous quantification methodologies requires knowledge of the available equipment, their operational characteristics and information about the underlying control algorithms.

The report continues that recent developments have aimed to combine the operational objectives, e.g. maintaining temperature in a building, together with the economic aspects, i.e. minimising electricity costs, with application of a dynamic time series model.

Part of the ELEXIA project’s aims is to extend such flexibility functions, which effectively link prices and demands with other input variables such as the temperature or time of day.

With this the methodology should be more applicable to systems where price is not the only driving factor, such as buildings.

The ELEXIA project’s approach is to model the demand via a generalised differential equation, in which the ‘latent state’ is stated as a function of the exogenous inputs including at least energy prices plus a multivariate Brownian (random) motion factor to account for the effect of other unknown variables on the flexibility.

If the latent state is close to 0, then the system is inflexible, while if it is close to 1 it is flexible. It can also be multidimensional for more complex systems.

According to the ELEXIA report this type of function has a wide number of applications within energy systems. For example, it can be used to derive commonly used flexibility characterisations such as peak demand reduction, flexible load or cost savings.

It also could be used for system identification of model-based controllers, designing orders in flexibility markets or improving coordination between TSOs and DSOs and potentially as a tool for designing dynamic pricing schemes.

Another application that is intended to be investigated within the ELEXIA project is to estimate the amount of flexible energy in energy system planning.

ELEXIA demonstrations

The ELEXIA project, which is coordinated by the Norwegian NORCE research centre, is being undertaken by a consortium of 22 partners across eight European countries.

Three demonstrations are proposed, with one in the Port of Sines in Portugal with the integration of locally generated renewable energy to support its decarbonisation.

A second is in a residential site in the Høje-Taastrup municipality in eastern Denmark, which faces the challenge of integrating local heating and cooling networks within the regional system while increasing the share of renewable sources.

The third is in a mixed industrial, residential area in the Dokken area in Bergen, Norway, to optimise the operation of an integrated energy system with tight sector coupling.

Among other recent advances is the development of an event loop that acts as an API connection to the Predicer (predictive decider) open source tool, which is being utilised in the project, enabling sending input data, executing the optimisation process and retrieving the results seamlessly.

The system also can incorporate real-time forecasts such as weather and electricity prices to enhance the optimisation process.

The project team anticipates that this integration promises to revolutionise the way local energy systems are managed and provide significant benefits to both professional and household users.

The project also intends to further develop the connectivity API to integrate it with the event loop to enhance the energy system optimisation capabilities.

ELEXIA started in October 2022 and runs to September 2026.

Jonathan Spencer Jones

Specialist writer
Smart Energy International

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