• Energy Research

Active building envelopes that act as energy converters—gathering on-site available renewable energy and converting it to thermal energy or electricity—is a promising technological design niche to reduce energy consumption in the building sector, cut greenhouse gas emissions, and thus tackle climate change challenges. This research adds scientific knowledge in the field of composite building envelope structures containing phase-change materials for thermal energy storage. In this study, the focus lies on the cooling phase of the diurnal gain and release of solar energy. The experimental setup imitates day and night environment. Six alterations of small-scale solar facade modules are tested in two different configurations—with and without the adjustable insulation layer on their outer surface during the discharging phase. Modules explore combinations of aerogel, air gap, and Fresnel lenses for solar energy concentration. The results allow us to compare the impact of the application of an additional insulation layer at “night” for different designs of solar facade modules. The results show that modules with an air gap provide higher heat gains but do not take full advantage of the latent heat capacity of phase-change materials.

Abstract Optimizing energy consumption in the cities might present a significant impact on decarbonization strategies approaching carbon neutral future in 2050. Positive Energy Block initiative is targeted particularly to densely build environments promoting shared on-site renewable energy production and storage, using smart grids, internet and communication technologies, Internet of Things and other highly advanced energy efficiency technologies within the neighborhoods. Research presented focuses on transition from traditional urban block to Positive Energy Block in valuable environment of historic city center exploring possibilities of waste heat regeneration and on-site renewable energy technologies. Energy consumption data is analyzed and the conception for possibilities of on – site renewable energy generation and waste heat recovery from data centers and cooling units in selected urban block is drawn. The results indicate that very ambitious targets for energy efficiency improvement are needed to achieve positive energy block – 65% and 60% for electricity and heating consumption, respectively. Possible savings of CO2 emissions are 45–50 kg/m2 per year.

In most cases, internal insulation is the only solution to improve the energy efficiency of historic buildings. However, it is one of the most challenging and complex energy efficiency measures due to changes in boundary conditions and hygrothermal behavior of the wall, particularly in cold climates. This study presents the long-term monitoring of the hygrothermal performance of an internally insulated historic stone wall building. The study aimed to assess the hygrothermal behavior of the dolomite wall if mineral wool insulation is applied internally on the north-east wall in the rooms with and without high internal moisture load. The measurements included temperature, relative humidity, water content, and heat flux. Monitoring results are compared with 1D hygrothermal simulations and a building energy consumption simulation. The in situ measurement results and hygrothermal assessment shows energy consumption decreased by 55% with relative humidity under the insulation staying belove 60% for most of the time, with short periods of increase over 80%. Energy consumption simulation shows an energy saving potential of up to 72% in the case of proper energy management.

Abstract The EU 2030 climate package calls for raising energy efficiency, increasing usage of RES and decreasing the carbon footprint. There are stringent requirements for new buildings, but the energy efficiency potential in the existing building stock is still not fully explored. The latest trend in urban energy efficiency is the Positive Energy Block (PEB) strategies for new developments. It includes raising building energy efficiency, optimizing energy flow and implementing renewable energy sources (RES). Transforming all existing blocks in a city centre to a PEB would radically change the pattern of energy supply and consumption. European cities have historic centres with great architectural and cultural value. Any urban regeneration strategies must respect and preserve historic values. This paper describes double multi-criteria analysis evaluating urban blocks from both the energy efficiency and cultural heritage perspective with the goal to select the sample block for a “Smart urban regeneration – transition to the Positive Energy Block” case study. Proposed criteria for multi-criteria analysis to evaluate cultural heritage, liveability and energy efficiency potential describes specific qualities of the urban block. The obtained results show that blocks with higher cultural value show less energy efficiency potential and vice versa. It is recommended to apply cultural value and liveability qualities in the Smart urban regeneration process to those blocks with high energy efficiency potential.

Abstract Energy communities are paving the way for new cooperation opportunities related to energy consumption and energy production. Individuals unite in energy communities to reduce the costs related to energy consumption. Although previous work has mainly focused on energy exchange inside the community. This work aims to investigate the Pareto-optimal solutions to the transformation of a historical district into an energy community. For energy efficiency and production measure calculation, a system dynamics model is developed. Multiobjective differential evolution optimization method is employed for the evaluation of energy efficiency and production measures with a focus on net present value, self-sufficiency, annual emission reduction, and specific heat consumption. The optimization target functions can be increased at a cost in net present value. Replacement of household appliances and windows enables significant energy demand reductions while maintaining positive net present value. Electricity production from photovoltaic panels offers an additional pathway to increase selfsufficiency share while maintaining positive net present value.

Abstract Buildings are linked to a significant untapped energy saving potential, accounting for 40 % of European Union’s (EU) final energy and 36 % of CO2 emissions. Energy efficient building envelopes plays the key role to achieve decarbonization of the EU’s building stock by 2050. Active building envelopes are emerging and novel trend offering the paradigm shift in perception of building enclosures. Paper presents study of active solar façade containing phase change material for energy storage. Study seeks for optimisation of solar façade module by introducing dynamic component and variating in the composition of module itself to ensure faster energy harvesting and minimise the heat losses at discharging phase. Comparative tests were carried out in laboratory, in controlled heating and cooling conditions to evaluate impact of dynamic component. The dynamic component has reflective inner coating that focuses solar radiation on the element in heating phase and aerogel insulation filling in the blades that decreases heat loss in the cooling phase. Varying components in the design were used– thickness of aerogel insulation, Fresnel lens and width of concentrating cone diameter. Wide range of phase change material average temperature was observed 24 °C in setups with full aerogel filling to 50 °C in setup Fresnel lens. Average temperature in phase change material was reached higher in all setups with dynamic component compared to identical setups without dynamic component. Temperature differences were in the range from 1 °C in aerogel filled setups till 6 °C in setups with Fresnel lens.

Abstract In recent years, the demand for energy-efficient technological solutions in the building sector has risen significantly worldwide. The exploitation of phase change material as a medium for thermal energy storage in building envelopes has increased due to its superior properties. There is still a knowledge gap to cover in the way to the effective solar thermal energy storage in the building envelope – to enhance the heat transfer, to reduce the heat loss, etc. This paper deals with the optimisation of heat transfer using a solar concentrator (Fresnel lens). This study examines the effect of Fresnel lens focal point location on heat transfer in a dynamic solar facade prototype that stores thermal energy in phase change material. Nine different setups (solar façade compositions) were tested in the laboratory – two parameters with three alternatives each. Testing conditions simulate the relevant Northern Europe climate. By changing the air gap configuration and location of the Fresnel lens focal point, the heat transfer to phase change material was observed by measuring temperatures in the phase change material container using five thermocouples. The results show the improved thermal performance in test modules with larger cone diameter by 7.2 % and Fresnel lens focal point positioning closer to the back of the phase change material container by 5.4 %.

Abstract The study presented in this paper is a continuation of small-scale passive solar wall module testing to evaluate: 1) the impact of phase change material embedded in building envelope on indoor air temperature in comparison to reference wall insulated with mineral wool 2) the impact of Fresnel lens on heat transfer processes in designed module compared to PMMA acrylic glass. Six different solar wall modules and a reference wall module were built and tested in a laboratory under controlled conditions. Compared to previous studies, changes in the experimental setup were made - solar radiation intensified, simulated outdoor temperature adjusted. The study shows explicitly the phase change melting processes in different modules tested, describing the differences between modules and impact of Fresnel lenses and insulation solutions. Room temperature with solar wall modules after the full cycle of charging and discharging latent and sensible energy (24 h) is higher than in the reference wall. Two of 3 of the proposed solar wall modules with Fresnel lens are more effective than modules with PMMA.