Authors

Mia Ala-Juusela, VTT Technical Research Centre of Finland
Andreas Tuerk, Joanneum Research
Ismo Heimonen, VTT Technical Research Centre of Finland

(Note: opinions in the articles are of the authors only and do not necessarily reflect the opinion of the EU).

Introduction

Positive Energy Buildings (PEBs) offer a good option for improving energy efficiency and promoting distributed renewable-based energy generation. These are needed for climate change mitigation and improved resilience of the built environment. The H2020 EXCESS project (FleXible user-Centric Energy positive houseS) develops PEB solutions and demonstrates them in four European cities to prove that cost-competitive, positive-energy building solutions can be realised across different European climatic zones. This article presents the work of the EXCESS project and highlights some of the results obtained so far.

In the EXCESS project, 21 partners from eight European countries aim to showcase how nearly-zero energy buildings can be transformed into PEBs. EXCESS defines a PEB as an energy efficient building that generates more energy than it uses via renewable sources, with a high self-consumption rate, over a time span of one year. A user-centred design approach is an integral part of the EXCESS PEB concept, to provide a comfortable and healthy indoor environment for its occupants and raise their awareness on how daily practices impact their building’s energy demand and its overall performance.

The EXCESS project

EXCESS has advanced new materials, technologies, and integrated technological systems promoting a user-centric approach. This is realised by capitalising on new ICT opportunities for optimising the interplay of local generation, storage, and consumption at the building and district levels. Ensuring high replicability across Europe, the pilot cases provide examples of multi-storey residential and office buildings located in four different climate zones (Nordic, Continental, Oceanic and Mediterranean climate zones).

The demonstration activities are accompanied by co-innovation, replication, and exploitation activities to further maximise exploitation of the project’s technical, social, and economic solutions, preparing them for future market roll out and take-up. This is also supported by examining funding opportunities for energy efficiency and renewable energy solutions. In addition to the technical solutions, the latest results include a performance evaluation handbook, an analysis of cost-optimality of the technology packages used on the EXCESS demo sites, and a review of business models for rolling out PEBs.

EXCESS demo sites

The Nordic climate demo case (Finland)

The Nordic climate demo case is a multi-storey residential building in Kalasatama, Helsinki, in Finland. The aim is to demonstrate the realisation of a building that is generating as much local renewable energy as is needed for heating, ventilation, and domestic hot water annually. The Kalasatama house is demonstrating the performance of semi-deep geothermal boreholes integrated with heat pumps, PVs on facades and roof, PVT panels on the roof, ventilation cooling and high COP domestic hot water systems, within a highly energy-efficient building. Demand based ventilation has high efficiency heat recovery, and energy systems are controlled with smart control and an optimisation system. The inhabitants moved to this newly built building in late August 2023 and the monitoring of its performance has been started.

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Figure 1. The Finnish demo site in Kalasatama area, Helsinki. Plan (by Sweco) on the left and the new building in August 2023 on the right (Source: Bassotalo). 

The Oceanic climate demo case (Belgium)

The Oceanic climate demo case, in Belgium, is part of a residential area in Hasselt. The project consists of 68 apartments and 22 houses intended for social housing. The residential units are connected to a small district heating network which is heated by different thermal energy sources (geothermal heat pumps, gas-fired geothermal heat pumps, and backup gas-fired boilers). The building is being converted to a positive energy building by implementing innovative solutions developed within the EXCESS project; PVT panels for renewable heat and electricity, multi-source and direct controlled heat pump, model predictive controller (MPC) for optimisation of the energy flows onsite, and activation of thermal and electrical flexibility in the heat interface units within the apartments.

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Figure 2. The Belgian demo site in Hasselt. (Source: VITO)

The Mediterranean climate demo case (Spain)

The Spanish demo case, representing the Mediterranean climate, is located in the historical centre of Valladolid and it is a protected classical Renaissance palace (XVI century). The project includes a complete renovation of the interior of the building to create nine dwellings. The envelope of the building is being upgraded to minimise energy demand without any visual modifications to the protected exterior façade. In addition, high performance HVAC systems will be installed, as well as the renewable energy systems that the architectural protection allows. The planned demonstrated technology includes integration of air heat pump system, PV panels, Ion-Lithium batteries for electricity storage, and eV (electric vehicle) charging stations. The integrated controller, human-machine interface system, and building energy management system are used for deciding the strategies for energy sharing and trading.

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Figure 3. The Spanish demo site in Valladolid. (Source: Urb-Atelier) 

The Continental climate demo case (Austria)

The Austrian demo case representing the Continental climate, is part of a former commercial zone that is transformed into an area with mixed use, including offices, recreation zones as well as sports facilities and restaurants. In total, the 19 buildings in the area are being refurbished towards passive house standards while increasing the share of locally generated renewable energy (solar energy and small hydropower). Through the integration of innovative elements for load shifting, storage, user integration, interaction with the local electricity grid as well as a smart, predictive control, a maximum energy flexibility will be achieved, and the self-consumption will be increased.

The EXCESS demo building consists of ten floors, with a cafeteria in the basement and office space with temporary overnight accommodation. Several energy efficiency measures will be integrated, including a multifunctional façade (including electricity generation, heating, and cooling) that can be mounted to the exterior of an existing building to improve its energy performance. The hybrid energy system combines a cascading heat pump system, PV panels on the roofs and façades, and a small hydro power plant that will generate electricity for the building. Energy flexibility in the building is also maximised by thermal building mass activation, and decentralised buffer storage. User-centric applications will be a key innovation to facilitate the creation of an energy community. The application allows constant monitoring and verification of energy savings at the prosumer and the building levels and facilitates the transparent distribution of benefits arising from energy optimisation among prosumers based on energy measurements handled through blockchain.

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Figure 4. The Austrian demo building in Graz. (Source: AEE Intec)

Performance evaluation handbook

A key publication summarising many of the results of the EXCESS work is the Performance evaluation handbook of PEB solutions, describing principles of performance evaluation of PEB solutions. It provides an overview of commonly used key performance indicators (KPIs) used for the evaluation, first at general level and then focusing on the EXCESS demo case studies. Furthermore, the measurement plans for the demo sites are described including the goals and technical details. The main goal in each case is to implement PEB level building with high energy performance. The cases include sub-goals related to new technology solutions and their performance.

In the energy domain, the main focus of the EXCESS project team is on renewable share, self-consumption rate of local renewables, and self-sufficiency ratio describing the share of own local generation compared to demand (see Table 1). The energy flexibility and low CO₂ emissions were seen as a big value for energy positive buildings. In the economic domain, the capital costs, operational costs, life-cycle costs, and global costs were recognised as the most important key performance indicators. In the technology domain indicators, seasonal coefficient of performance is describing performance and efficiency of the technology and gives a good indicator for development of the technology. Robustness and stability were seen as basic requirements for the energy systems. Concerning the social indicators, the variety of KPIs is large, which leaves the selection for each case separate. User satisfaction, comfort and visibility of the results were recognised as the main indicators.

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Table 1: Summary of key performance indicators chosen for the four demo cases; The ones with grey background are among the most important KPIs recognised in an EXCESS workshop. (EXCESS D4.1)

Cost-optimality analysis

The cost-optimality of the different technology packages used in EXCESS for the transformation of nearly zero energy buildings (nZEBs) to Positive Energy Buildings (PEBs) have furthermore been analysed for all demo sites. The packages contain solutions that are relevant for the types of buildings similar to those in EXCESS demos: new residential buildings (Helsinki) as well as existing buildings that are renovated to PEB standard (Hasselt, Graz and Valladolid).

The analysis encompasses a comparison of global costs and net primary energy demand of the different technology packages. Global costs contain the net present value of all investment costs and all operation, maintenance, and energy costs for a defined calculation period. Net primary energy demand contains the building’s energy demand for heating, cooling, ventilation, DHW and lighting in terms of net primary energy. Out of this analysis, general conclusions on the cost-effectiveness of PEB technology packages are derived. Furthermore, the analysis reveals the payback period of PEB technologies and compares global costs of PEB technology packages with technology packages required for the current nZEB legislative standard.

The analysis showed that most energy efficiency or renovation measures that are required for a PEB are not cost-effective with the cost assumptions used for the analysis. This means that the overall global cost increase (calculation period 30 years) for energy efficiency or renovation measures compared to the reference case without measures. However, results are very sensitive to changes in electricity prices and technology cost. High energy prices increase the profitability of energy efficiency measures whereas low energy prices increase global cost and thereby decrease profitability of technology packages. Furthermore, results indicate that the use of renewable energy sources is more cost-effective than the further upgrade of the envelope. The profitability of a change in the heating system strongly depends on the costs of gas and electricity.

The analysis reveals that it is necessary to have a system view on costs. Even if individual technologies may not be cost efficient, they can be enabling technologies that make the entire system more cost efficient. Subsidies or additional research efforts to reduce the costs of PEB technologies could further improve the profitability of the analysed PEB solutions. The cost issue could also be addressed with new, well developed business models.

Business models

Whereas a good variety of technologies exist for realising the PEB, and integrated PEB concepts are emerging, there is a lack of business models to realise and support PEBs. Well-designed business models are recognised as a crucial element needed for a wider roll-out of PEBs. As part of the work on the EXCESS project, potential business models for PEBs were searched for and their contribution to the different PEB elements was studied, also pointing out some aspects that need to be considered when setting up the business model. A selection of interesting or emerging business models are described in the resulting article (Ala-Juusela and Tuerk 2022), concentrating on the typical customer segments, typical value propositions, potential life-cycle phases, benefits and challenges.

The analysis focused on the customer segments and value propositions, looking briefly at the revenue streams for some specific business models. Figure 5 (Rehman et al 2022) presents an overview of the emerging business models based on material from Laffont-Eloire and Peraudeau 2019 & RenovationHub 2022, The Smart Cities Information System (SCIS) 2022, Hughes and Kabiri 2013, Boza- Kiss and Bertoldi 2018 and; Okur, Heijnen and Lukszo2021.

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Figure 5. Business model approaches for energy efficiency, renewable integration and buildings flexibilisation: typical customers and main elements of the value proposition. (Rehman et al 2022)

PEBs have a larger range of possible revenue streams than NZEBs, however most of them cannot yet be fully valorised due to limitations in the regulatory frameworks. Next to new revenue streams, the cost for PEBs still needs to decrease, and in particular technology integration and installation should not pose prohibitive costs. The ongoing change in the market towards service or outcome-based business models could pave the way for models that support the wider roll-out of PEBs, which is a complex system requiring a lot of knowledge on different fields and companies with new skills. The change is based on the insight that the value is not always in the product, but instead related to the outcome; the certainty of the renewable source of the energy that is used in the building, the security or price level of the energy provision or even the comfort and well-being of the building users.

There is still a lot of work ahead in understanding the real needs of the customers, or their willingness to pay for the services, as well as creating affordable structures and contractual arrangements for the provision of the service. It is also worth studying if the enlargement of the scope on district or neighbourhood level (e.g. energy communities) could bring some additional benefits, increasing the viability of the business model. A deeper analysis and further development of the business models will be part of the upcoming work in the EXCESS project.

Conclusion

The work in the EXCESS project is progressing, with new results indicating the possibilities and potential challenges in promoting PEBs. Well-chosen KPIs will help in showing the benefits of PEBs from a technical, environmental, social and economic point of view. The profitability of PEB solutions will depend highly on the investment and energy costs, but this can be affected by subsidies and further development of the technologies. The need for new business models is evident, and there is still some work to do to make them feasible. Keep updated on the further developments at our website: EXCESS | Home (positive-energy-buildings.eu)