The development of an environmentally sustainable hydrogen economy requires addressing environmental impacts along the entire hydrogen value chain. In order to support this transition, the present work aims at paving the way for the development of the first Product Environmental Footprint Category Rules (PEFCRs) for hydrogen devices. To that end, this work presents two main outputs: (i) a categorisation of hydrogen devices, and (ii) a set of recommendations for selected product categories and subcategories for PEFCR development. The categorisation procedure considers five stages of the hydrogen value chain referred to as product families: devices for hydrogen production, conditioning, storage, transport, and use. Under each family, an overview of the available hydrogen technologies is provided and common technical and environmental aspects of the involved devices are identified according to the rules provided by the European Commission Recommendation 2021/2279 on the use of the Environmental Footprint methods to measure and communicate the life cycle environmental performance of products and organisations. This led to the definition of 11 product categories, for five of which a further subdivision into subcategories is proposed. Furthermore, recommendations for drafting hydrogen-related PEFCRs are provided for a selection of product categories and subcategories in line with the aforementioned Commission Recommendation, additionally drawing on hydrogen-specific environmental life cycle assessment guidelines and existing PEFCRs not related to hydrogen. This serves as a cornerstone for the development of the first PEFCRs specific to hydrogen devices.
Is flexibility just a form of energy?” This paper argues no, quantifying regulatory barriers blocking multi-energy systems from Italian flexibility markets amid post-COVID and Russia-Ukraine war volatility, with the Italian day-ahead uniform prices, peaking above € 500 per MWh. Renewables drive intra-day spreads and congestion favoring sector-coupled multienergy systems, yet Italy’s market for dispatching services organized by the Italian TSO, 1 MW bids, downward charges, and symmetry exclude small-scale assets. Milan SENERGY NETS data feeds mixed-integer optimization modeling dayahead, intra-day, and flexibility market participation across 7 cases: baselines versus reforms with 0.1 MW bids, asymmetric provision, and no downward fees. Reforms unlock around 20 percent winter cost savings via asymmetric flexibility aligning with physical ramp limits. Daily emissions optimizations yield modest carbon dioxide cuts via timing shifts; yearly analysis reveals sharp winter trade-offs with full combined heat and power curtailment for heat pumps despite costlier electricity. Italian rules must evolve per EU Electricity Market Design Reform to harness multi-energy systems for decarbonization and stability.
This paper reviews the current research on aquifer thermal energy storage (ATES) and mine thermal energy storage (MTES) in Germany providing descriptions of 3 low-temperature ATES (LT-ATES), 8 high-temperature ATES (HT-ATES), and 2 MTES research sites. While the overview reveals a diverse field of investigations spanning various spatial scales, research objectives, and methodologies, the predominant focus is limited to early-stage research with low technology readiness levels (TRL). The high number of HT-ATES research sites suggests greater research interest compared to LT-ATES. The integration of ATES into district heating (DH) grids in particular is a prominent research focus, yet almost none of the projects are specifically intended for practical implementation. Future research should therefore prioritize real-world demonstration projects and identify key locations, which is crucial for showcasing the benefits of ATES. The need for a streamlined regulatory framework that addresses environmental risks and ensures installation quality and efficient permit procedures is also discussed.
Triassic sandstones of the Middle and Upper Buntsandstein are highly suitable for ground source heat pump (GSHP) systems. Thus, knowledge of their thermal properties, which can be measured or estimated by theoretical models, is crucial. However, the transferability of estimated thermal conductivities to the field scale has not yet been thoroughly examined. Therefore, in this study, the thermal and lithological properties of 156 core samples from a borehole in the Buntsandstein are analysed in the laboratory. Various theoretical models are applied and compared to the laboratory-derived thermal conductivities. The best agreement is achieved with the Voigt-Reuss-Hill model with an average thermal conductivity of 4.5 W m−1 K−1 and an RMSE of 0.7 W m−1 K−1 (T = 20 °C). The results of this model are compared to depth-specific, effective thermal conductivities from an enhanced thermal response test (ETRT). These effective thermal conductivities range between 2.3 and 6.1 W m−1 K−1 with an average of 4.7 W m−1 K−1. We demonstrate that some theoretical models can provide an initial estimation of the effective thermal conductivity of sandstones when groundwater flow is negligible. However, the accuracy of the estimation is limited by sample quantity and model assumptions.
The thermal properties of grouting materials characterise the heat transfer around borehole heat exchangers (BHE). However, these properties are typically determined in the laboratory. Thus, this study aims to assess the properties of grouting materials in the field. Two BHE grouted with two different grouting materials within unsaturated loess and limestone were excavated up to a depth of 15 m. Collected field samples show higher thermal conductivities by 13% ( W / S = 0.3) and 35% ( W / S = 0.8) than laboratory samples of the same material. These differences in thermal properties are mainly related to the filtration of the grouting suspension. In addition, with a short-time enhanced thermal response test (ETRT), 17% lower in-situ thermal conductivities are determined than in comparison with the field samples. The deviations are attributed to the geometry of the borehole, the trajectory of the BHE pipes and the heating cable. Thereby, this study shows the limitations when transferring laboratory-derived properties to a field site and emphasises the importance of considering site conditions, such as geology and hydrogeology.
