Electricity in Buildings and LCA

The latest LCA Forum considered key issues in research and labelling regarding the representation of electricity mix in buildings’ operational electricity consumption.

Electricity consumption is an important contributor to their environmental impacts. The forum discussed the following key questions:

• What is the current state of electricity mix modelling for construction products and buildings’ use phases?
• How do different modelling approaches reflect and/or influence the transition of the electricity sector of a country to renewables?
• Which electricity mix modelling approach(es) should be offered in LCA databases?

Introduction

The 85th LCA Forum¹ 'Electricity in buildings LCA: state of the art, challenges and ways ahead' on 9 November 2023 at the Swiss Federal Institute of Technology Zurich (ETHZ) was opened with a welcome address given by ROLF FRISCHKNECHT (treeze, CH). Electricity consumption in construction, product manufacture and in the use phase of building is an important contributor to their environmental impacts. The forum addressed electricity mix modelling issues in LCAs of buildings. Several different models to represent the electricity consumed during the use phase are applied in European countries: (1) the current national electricity consumer mix according to national statistics; (2) the electricity mix of the supplier, based on guarantees of origin (GO), (3) a (quasi dynamic) future electricity mix based on a national official energy scenario, (4) an individual electricity mix which covers the use profile of the building under assessment. Companies in the supply chain of construction products purchase ’green’ electricity products to lower the environmental footprint of their products. These green electricity products are often based on GO or similar certification schemes. Physical production of electricity and electricity quality (GO) are traded independently on different markets. This feature is a challenge for process-based LCA.

Setting the scene

ANDREAS ECKMANNS (Swiss Federal Office of Energy, CH) spoke about the latest political developments with regard to the Swiss Energy Strategy 2050. While the Energy Perspectives 2050+ (http://www.energieperspektiven.ch/) provide targeted economic and technical scenarios for Switzerland, the Energy Strategy consists of political measures to achieve the net-zero target by 2050. There have been encouraging political developments in recent months: In June 2023, the Climate Protection and Innovation Act (CIP) was approved by Swiss voters with 59% in favour. Shortly afterwards, the so-called ‘umbrella decree’ (Mantelerlass) was adopted by the Federal Assembly on 29 September with a large majority. This provides a solid legal basis for tackling the climate targets. He concluded by stating that there are still many open questions and definitions to be clarified and called for us to use the momentum together to step up our efforts in the fight against climate change, which is more urgent than ever.

ANDREA MIKSCH (Pronovo, CH) explained the concept of guarantees of origin (GOs). Switzerland is a pioneer regarding the full disclosure of electricity on production and consumption side based on GOs. Via the hub of the Association of Issuing Bodies (AIB), Switzerland is connected with 26 other European countries and able to trade GOs. Moreover, starting from 2025, Pronovo will start issuing GOs for renewable gaseous and liquid energy carriers allowing to track energy conversion and emissions. This is a further step towards a fully disclosed energy life cycle.

GERHARD EMCH (ewz², CH) presented a utility’s perspective on electricity procurement and its consumption in buildings. Swiss customers with market access can change the electricity supplier once a year and usually procure energy and guarantees of origin separately. Customers with a default supplier can choose among several full supply products. A planned legislation will require that the default product is renewable and produced in Switzerland. Switzerland has a national registry for guarantees of origin requiring a full declaration. Every renewable and non-renewable kWh of produced electricity must be recorded and for every kWh delivered to an end customer a guarantee of origin must be cancelled. The supplier mix must be published every year based on the cancellations in the national registry.

Electricity mix modelling in European buildings LCA

BRUNO PEUPORTIER (Mines Paris - PSL, FR) presented two models of the French electric system (see Table 1 below): the static model of the French building regulation, and a dynamic model (short term and long term) developed at MINES Paris (Frapin et al. 2021). Effects on the evaluation of GHG emissions are shown, as well as a comparison based on data of the French transmission system operator. Sensitivity and uncertainty analysis are finally addressed. Consequential LCA is more relevant as a decision aid, but induces higher uncertainty related to the determination of marginal processes.

MARIA BALOUKTSI (AAU, DK) presented the background and characteristics of the new Danish emission factors for electricity and district heating, which were developed in mid-2023 and will become effective in 2025 (Sørensen et al. 2023). Buildings in Denmark are already required to make climate declarations, and there is a carbon limit on buildings larger than 1000 m². In this regulation, average emission factors considering future developments in the Danish energy mix are used for calculating module B6 (operational energy use). The updated factors significantly reduce the average share between operational and embodied carbon from 26/74 to 9/91 (Tozan et al. 2023). As opposed to the factors currently in place that favour heat pumps, the updated ones encourage the use of district heating, however, they incorporate political goals that may not be achieved, increasing their uncertainty.

ROLF ANDRÉ BOHNE (NTNU, NO) gave an brief introduction on the Norwegian electricity production and consumption, explaining the difference between (1) physically delivered electricity; (2) electricity certificates; (3) electricity disclosure within the Norwegian electricity grid. He also explained how these differences influenced calculation methods, and why the Norwegian standard S3720:2018 (Standards Norway 2018) operates with 2 different CO₂-factors for calculations, their origin, and how the use of these factors is used in calculations for ‘zero emission buildings’ in Norway.

Models to establish national electricity grid emission factors

MALTE SCHÄFER (TU Braunschweig, DE) highlighted the importance of methodological choices in calculating national grid emission factor (NGEF). Official data sources that publish NGEF values, which differ by a factor of up to one third from one another, were the motivation for his investigation. The presentation included nine aspects relevant for NGEF calculation, a quantification of the impact that each aspect has on the result, and a recommended configuration for calculating NGEF from the perspective of the consumer. The talk concluded with recommendations for practitioners, data publishers, and institutions publishing accounting guidelines.

MATT ROBERTS (University of California Berkeley, US) illustrated how consequential LCA (cLCA) quantifies the environmental impacts from a system response to a change in demand (Schaubroeck et al. 2021). He demonstrated how cLCA can be used to quantify the environmental impacts from changing a building’s electricity demand profile due to the use of on-site energy generation and on-site energy generation technologies. cLCA relies on marginal emissions factors (MEFs) as they represent the environmental impacts from the generation plant that changes production capacity to meet a change in demand (Hitchin & Pout 2002). Using cLCA with MEFs provides a more holistic understanding of the strains placed on the electricity grid from adding technologies into buildings.

Electricity mix modelling in Swiss buildings LCA

ROLF FRISCHKNECHT (treeze, CH) presented the electricity model used in Swiss buildings LCA to represent the electricity mix used in construction material manufacture and in building operation (KBOB et al. 2022). The electricity mix model relies hourly data on national physical production and commercial trade with neighbouring countries (Krebs & Frischknecht 2021). The volume of electricity exported in a certain hour is subtracted from the domestic production volume of that hour. The electricity imported from one country is represented by its domestic production mix and the volume imported to Switzerland is added to the net domestic production volume. Recent research (Frischknecht et al. 2020) revealed that a building’s hourly consumption profile matches fairly well the overall hourly electricity consumption profile of Switzerland. Hence, there is hardly any difference between the electricity mix of a building and the national grid mix. He pleaded to refrain from segregating the national grid mix into several electricity mixes for different applications (buildings, industry, agriculture, etc.) and highlighted the need for more transparency regarding commercial trade and transit of electricity.

ELLIOT ROMANO (Université de Genève, CH) presented HOROCARBON.CH, a website which quantifies GHG emissions embedded in electricity consumption. Based on a novel methodology (>Romano et al. 2023), it addresses the complexities arising from fluctuating generation mixes and cross-border trade. Applied to Switzerland, which heavily relies on low-carbon domestic generation but imports 12% from fossil-based sources, the method reveals an average yearly GHG emission factor of 98 g CO₂e/kWh between 2017 and 2021. The method considers classification of generation technologies by dispatch cost and cross-border trade mechanisms, emphasizing the importance of accounting for seasonal and hourly emission factor profiles for informed decision-making on electricity use.

SÉBASTIEN LASVAUX (Institute of Energies - HEIG-VD, CH) presented the EcoDynElec model. It is an electricity model developed in Switzerland as an Open Python package to calculate historical profiles of environmental impacts of European electricity mixes (Lédée et al. 2023). EcoDynElec tracks the origin of electricity across European countries based on physical flows of generation and cross-border exchanges. It has been applied for Swiss buildings to analyse the time step influence (hourly, daily, monthly, annual) of the GHG emissions related to the electricity used in buildings (Padey et al. 2020).

MARTIN JAKOB (TEP Energy, CH) argued that GHG emissions related to buildings need to be reduced to nearly zero for Switzerland to meet the goals of its climate strategy. A substantial part of these emissions currently is caused by electricity consumption. Referring to an ongoing Swiss research project, he discussed a series of methodological issues to assess emissions directly or indirectly attributed to the buildings domain: (1) should the allocation be based on certificates of origin or on physical or commercial cross-border electricity flows? (2) Which trade balance model should be used? (3) Should the future development of the electricity mix be considered or not? (4) Should average effects or marginal effects be used?

Breakout group discussions

The discussions in the three breakout groups resulted in the following main messages, conclusions and recommendations:

The group discussing location-based or market-based electricity recommended modeling electricity with both approaches as they together are able to play their advantages. The group called for strict criteria for market-based electricity mixes based on GOs: (1) bundling purchase: obligation to purchase production and quality together, i.e. from the same power plants; (2) geographical proximity: introduce a limitation for the geographical distance of the power plant from the production site or building consuming the electricity; (3) limit trade of GOs: limit GO trade volume corresponding to the maximum transport capacity of power lines between countries; (4) additionality: create incentives for investments in new renewable power generation capacities (5) temporal correlation: create an obligation to cancel GOs in the very same hour they were issued.

The group discussing the advantages and disadvantages of static and dynamic electricity mix models proposed a differentiation between short-term and long-term perspectives. The choice of the appropriate approach depends on the goal and scope (e.g. individual building versus building stock), whether the focus is on regulation versus design and management of a single building, the strategy for construction, refurbishment or deconstruction of an individual building versus national energy or building stock strategies. The advantages of dynamic approaches are: (1) demand side management (e.g. when to best charge the electric cars or use the washing machine); (2) informing environmentally sound decisions (e.g. fitting an individual building with a heat pump or connecting to an existing district heating system); (3) scenario-based decisions (e.g. renewable energies available in a region/country are able to cover the future demand). Static approaches show the advantages of being much easier to model and relying on much less data and assumptions overall resulting in a higher user friendliness. The group also said that the need for dynamic approaches may depend on the country. In some countries dynamic approaches may not be required like for instance Norway with 88 % hydroelectric power production.

The third group discussed two questions: The first one was about how to model PV systems integrated or attached to buildings and particularly their operation (production, self consumption and export to the grid). The group agreed that models suggesting PV systems being a negative emission technology (NET) shall be discouraged. Instead, an ex ante or year-by-year allocation of the emissions caused by manufacturing and end of life treatment of the PV system between the shares consumed by the building and exported to the grid shall be performed. The second question was about whether attributional or consequential approach should be used to model the production and supply of electricity during the use stage of buildings. The group agreed that scenario-based approaches should be practiced more as compared to today. Average effects quantified with such approaches are important for macro-policy advising whereas marginal effects may more be suitable for technology subsidy fostering. The group acknowledged the usefulness of the attributional approach.

** Depending on use/production pattern (heating, cooling, domestic hot water, specific electricity consumption, PV electricity production) see Frapin et al. 2021.

Conclusions

ROLF FRISCHKNECHT summarised the main insights highlighting the following five points:

• GO systems are useful in motivating companies to lower their environmental impacts and carbon footprints, if improved substantially with strict requirements. The requirements identified are about additionality of renewable power production capacities, bundling the purchase of physical power and power quality, more closeness in terms of geography and time, limitation of GO trade to physical trade capacities. Models based on physical power production and commercial or physical trade should be used for the time being until improvements mentioned above are implemented in the European GO system.
• Dynamic modelling of electricity production and supply can be either long-term or short-term, depending on whether to tackle questions about national energy strategies or demand-side management, respectively.
• A lack of data was identified regarding electricity trade, in particular regarding the share of pure electricity transit.
• PV systems on buildings shall not be modelled as if they were negative emission technologies. Instead their environmental impacts are allocated to the shares of self-consumed electricity and those exported to the grid, respectively. Other approaches account for the contribution of buildings to the transition of power supply companies (with an export of PV electricity).
• More scenario-based LCAs should be carried out in particular when it is about future large shifts in national energy systems or future large shifts in other economic sectors.

Notes

1.     This conference report was jointly authored by: Rolf Frischknecht, Maria Balouktsi, Rolf André Bohne, Andreas Eckmanns, Gerhard Emch, Martin Jakob, Sébastien Lasvaux, Andrea Miksch, Bruno Peuportier, Matt Roberts, ,Elliot Romano, Malte Schäfer. Special thanks to Rolf Frischknecht for coordinating and editing the individual contributions. Conference presentations and videos are available for download from the LCA forum’s website: https://bit.ly/4adl65I

2.     ewz is the electricity utility serving the city of Zürich. It is one of the top five energy service providers in Switzerland and has an annual electricity production of 4.9 TWh and delivers electricity to more than 200,000 customers.

References

ADEME. (2020). Fiche technique. Positionnement de l’ADEME sur le calcul du contenu CO2 de l’électricité, cas du chauffage électrique, July 2020.

Frapin M., Roux C., Assoumou E. & Peuportier B. (2021). Modelling long-term and short-term temporal variation and uncertainty of electricity production in the life cycle assessment of buildings. Applied Energy, 307(118141). https://doi.org/10.1016/j.apenergy.2021.118141

Frischknecht R., Alig M. & Stolz P. (2020). Electricity Mixes in Life Cycle Assessments of Buildings. Uster: treeze Ltd.

Hitchin E.R. & Pout C.H. (2002). The carbon intensity of electricity: How many kgC per kWhe? Building Services Engineering Research and Technology, 23, 215-222.

KBOB, ecobau & IPB (2022) Regeln für die Ökobilanzierung von Baustoffen und Bauprodukten in der Schweiz, Version 6.0. Plattform "Ökobilanzdaten im Baubereich". Bern: KBOB, eco-bau & IPB.

Krebs L. & Frischknecht R. (2021). Umweltbilanz Strommixe Schweiz 2018. Uster: treeze Ltd.

Lédée F., Padey P., Goulouti K., Lasvaux S. & Beloin Saint-Pierre D. (2023). EcoDynElec: Open Python package to create historical profiles of environmental impacts from regional electricity mixes.  SoftwareX, 23(July 2023, 101485). https://doi.org/10.1016/j.softx.2023.101485

Padey P., Goulouti K., Beloin Saint-Pierre D., Lasvaux S., Capezzali M., Medici V., Maayan Tardif J. & Citherlet S. (2020). Dynamic life cycle assesment of the building electricity demand. Proceedings from: 21. Status-Seminar Erneuern! Sanierungsstrategien für den Gebäudepark, 2-4 September 2020, Aarau.

Romano E., Patel M. & Hollmuller P. (2023). Applying trade mechanisms to quantify GHG emissions of electricity consumption in an open economy - the case of Switzerland. SSRN. https://doi.org/10.2139/ssrn.4660632

Schaubroeck T., Schaubroeck S., Heijungs R., Zamagni A., Brandão M. & Benetto E. (2021). Attributional & consequential life cycle assessment: Definitions, conceptual characteristics and modelling restrictions. Sustainability, 13(13). https://doi.org/10.3390/su13137386

Sørensen M. N., Høibye L. & Enersen Maagaard S. (2023). Emissionsfaktorer for el, fjernvarme og ledningsgas for 2025-2075. Copenhagen: Artelia A/S.

Standards Norway. (2018). Method for greenhouse gas calculations for buildings, Vol. NS 3720:2018. Oslo: Commission SN/K 356.

Tozan B., Olsen C. O., Birgisdottir H., Kragh J. & Rose J. (2023). Klimapåvirkning fra nybyggeri: Analytisk grundlag til fastlæggelse af ny LCA baseret grænseværdi for bygningers klimapåvirkning fra 2025. Copenhagen: Aalborg Universitet.

Share:

Previous article

World Sustainable Built Environment Conference 2024

Next article

2023 Reviewers