Nikos Sakkas

Prof. Nikos Sakkas

HMU, APINTECH LTD, HULL UNI

Research Focus & Metrics

Academic Career Length

15Years (2012-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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16 April 2024 in Applied System Innovation
Verified
Journal Article
Open access
PDF file
SYSofia Yfanti
Sofia Yfanti
Nikos SakkasNikos Sakkas
Nikos Sakkas
Technology readiness levels (TRLs) is a well-established and widely used approach for defining the readiness of new technology. It assesses technology maturity against specific benchmarks, ranging from level 1 (concept) to level 9 (market solution). Although this is a useful classification service that allows us to establish a common language, there are cases where we find that this conceptual approach cannot adequately highlight the maturity of certain innovative endeavors and effectively steer their development to higher TRLs. We will present an empirical case where the TRL approach presented a critical shortcoming in highlighting the true and effective readiness of a specific technological development and could not suggest the next natural step in ascending the maturity ladder. We will seek to generalize for the case of co-creation at large, analyze why co-creation may be poorly serviced by the current TRL model, and suggest an amendment that would allow the observed shortcomings of the traditional TRL approach to be overcome and its use extended into such co-creative settings, thus allowing stakeholders to enhance the effectiveness and impact of their collaborative innovation efforts.

23 October 2023 in Energies
Verified
Journal Article
Open access
PDF file
Nikos SakkasNikos Sakkas
Nikos Sakkas
SYSofia Yfanti
Sofia Yfanti
PSPooja Shah
Pooja Shah
NSNikitas Sakkas
Nikitas Sakkas
CCChristina Chaniotakis
Christina Chaniotakis
MDMarharyta Domnich
Marharyta Domnich
Building electric energy is characterized by a significant increase in its uses (e.g., vehicle charging), a rapidly declining cost of all related data collection, and a proliferation of smart grid concepts, including diverse and flexible electricity pricing schemes. Not surprisingly, an increased number of approaches have been proposed for its modeling and forecasting. In this work, we place our emphasis on three forecasting-related issues. First, we look at the forecasting explainability, that is, the ability to understand and explain to the user what shapes the forecast. To this extent, we rely on concepts and approaches that are inherently explainable, such as the evolutionary approach of genetic programming (GP) and its associated symbolic expressions, as well as the so-called SHAP (SHapley Additive eXplanations) values, which is a well-established model agnostic approach for explainability, especially in terms of feature importance. Second, we investigate the impact of the training timeframe on the forecasting accuracy; this is driven by the realization that fast training would allow for faster deployment of forecasting in real-life solutions. And third, we explore the concept of counterfactual analysis on actionable features, that is, features that the user can really act upon and which therefore present an inherent advantage when it comes to decision support. We have found that SHAP values can provide important insights into the model explainability. In our analysis, GP models demonstrated superior performance compared to neural network-based models (with a 20–30% reduction in Root Mean Square Error (RMSE)) and time series models (with a 20–40% lower RMSE), but a rather questionable potential to produce crisp and insightful symbolic expressions, allowing a better insight into the model performance. We have also found and reported here on an important potential, especially for practical, decision support, of counterfactuals built on actionable features, and short training timeframes.

12 October 2021 in Energies
Verified
Journal Article
Open access
PDF file
Nikos SakkasNikos Sakkas
Nikos Sakkas
SYSofia Yfanti
Sofia Yfanti
CDCostas Daskalakis
Costas Daskalakis
EBEduard Barbu
Eduard Barbu
MDMarharyta Domnich
Marharyta Domnich
Energy demand forecasting is practiced in several time frames; different explanatory variables are used in each case to serve different decision support mandates. For example, in the short, daily, term building level, forecasting may serve as a performance baseline. On the other end, we have long-term, policy-oriented forecasting exercises. TIMES (an acronym for The Integrated Markal Efom System) allows us to model supply and anticipated technology shifts over a long-term horizon, often extending as far away in time as 2100. Between these two time frames, we also have a mid-term forecasting time frame, that of a few years ahead. Investigations here are aimed at policy support, although in a more mid-term horizon, we address issues such as investment planning and pricing. In this paper, we develop and evaluate statistical and neural network approaches for this mid-term forecasting of final energy and electricity for the residential sector in six EU countries (Germany, the Netherlands, Sweden, Spain, Portugal and Greece). Various possible approaches to model the explanatory variables used are presented, discussed, and assessed as to their suitability. Our end goal extends beyond model accuracy; we also include interpretability and counterfactual concepts and analysis, aiming at the development of a modelling approach that can provide decision support for strategies aimed at influencing energy demand.

1 November 2012 in Energy and Buildings
Verified
Journal Article
Closed access
MKMaria Kouveletsou
Maria Kouveletsou
Nikos SakkasNikos Sakkas
Nikos Sakkas
SGStephen Garvin
Stephen Garvin
MBMarko Batic
Marko Batic
DRDaniela Reccardo
Daniela Reccardo
RSRaymond Sterling
Raymond Sterling

7 March 2025 in Energies
Verified
Journal Article
Open access
PDF file
SYSofia Yfanti
Sofia Yfanti
DKDimitris Katsaprakakis
Dimitris Katsaprakakis
Nikos SakkasNikos Sakkas
Nikos Sakkas
CCConstantinos Condaxakis
Constantinos Condaxakis
Emmanuel KarapidakisEmmanuel Karapidakis
Emmanuel Karapidakis
George S. StavrakakisGeorge S. Stavrakakis
George S. Stavrakakis
This study explores the potential of ECs as a conduit for achieving a region’s or a country’s energy goals. The study focuses on Greece, where roughly 1700 energy communities have been founded since 2018. The methodology adopted is based, initially, on an extensive literature survey, aiming to outline the general energy goals on a regional and national level. On a second stage, focused interviews were accomplished with four of the biggest energy communities in Greece, investigating essential topics, such as their motivations, their business models, the obstacles they have faced, and their achievements. Environmental, economic, and energy security reasons were revealed as the main incentives for the foundation of energy communities in Greece. The major obstacles underlined by the interviewees were the bureaucracy and the changing, often towards a less supportive direction, legal framework. The contribution to a more sustainable energy environment, the reduction of the electricity procurement cost, and the remedy of energy poverty feature as the most important achievements. In the context of the ongoing energy transition in Greece, this article concludes that even though ECs can promote energy transition and mobilise a commonly acknowledged dialogue that can aid a nation’s efforts to achieve its energy goals, further investigation is required regarding the proposed policy initiatives, focused on strategies for upscaling the impact of energy communities, thus enabling them to flourish further.

17 August 2023 in Preprints.org
Verified
Preprint
Open access
PDF file
Nikos SakkasNikos Sakkas
Nikos Sakkas
SYSofia Yfanti
Sofia Yfanti
PSPooja Shah
Pooja Shah
NSNikitas Sakkas
Nikitas Sakkas
CCChristina Chaniotaki
Christina Chaniotaki
MDMarharyta Domnich
Marharyta Domnich
Building electric energy is characterized by a significant increase of its uses (e.g. vehicle charging), a rapidly declining cost of all related data collection and a proliferation of smart grid concepts, including diverse and flexible electricity pricing schemes. Not surprisingly, an increased number of approaches have been proposed for its modeling and forecasting. In this work, we place our emphasis on three forecasting related issues. First, on the forecasting explainability, i.e. the ability to understand and explain to the user what shapes the forecast. To this extent we rely on concepts and approaches that are inherently explainable, such as the evolutionary approach of genetic programming (GP) and its associated symbolic expressions, as well as the so-called SHAP (SHapley Additive eXplanations) values, which is a well established model agnostic approach for explainability, especially in terms of feature importance. Second, we investigate the impact of the training timeframe on the forecasting accuracy; this is driven by the realization that a fast training would allow for faster deployment of forecasting in real life solutions. And third, we explore the concept of counterfactual analysis on actionable features, i.e. features that the user can really act upon and which therefore present an inherent advantage when it comes to decision support. We have found that SHAP values can provide important insights into the model explainability. As for GP models, we have found comparable and in some cases superior accuracy when compared to its neural-network and time-series counterparts but a rather questionable potential to produce crisp and insightful symbolic expressions, allowing a better insight into the model performance. We have also found, and report here on an important potential especially for practical, decision support, solutions of counterfactuals built on actionable features and short training timeframes.