Thermal performance of a controllable pavement solar collector prototype with configuration flexibility

Solar energy harvesting as a renewable and sustainable energy source has been widely investigated in recent years across engineering fields. The use of Pavement Solar Collectors (PSC) can lead to clean energy production, an increase in road safety, prolong the service life of asphalt pavement, and can mitigate the Urban Heat Island (UHI) effect. This study describes a controllable large-scale research PSC prototype with high configuration flexibility, and full monitoring capability at the University of Antwerp, Belgium. Since small- or laboratory-scale setups do not reflect the behavior of actual projects, the present paper investigates the thermal response of a large-scale PSC in the Western European climate, including heating load, heat extraction capacity, and asphalt surface and profile temperature changes during heating and cooling experiments. The study shows that a low supply temperature compared to high (14 °C vs. 28 °C) can reduce the depletion rate of the stored thermal energy in borehole thermal energy storage up to 7 times. The sensitivity analysis indicates that an increase in flow rate from laminar to transient regime requires twice as much thermal power compared to the same flow rate changes within transient and turbulent regimes. The maximum average daily efficiency of the PSC could reach 34% with a flow rate of 4 l/min. The experimental results showed that increasing the pipe length from 50 m to 200 m reduces the cumulative power extraction capacity by up to 48%. Furthermore, the PSC system shows great potential in reducing the asphalt surface temperature (up to 12 °C) to mitigate the UHI effects. Finally, the PSC system effectively controls the temperatures of the interface zones to reduce the rutting distress in the summertime and lower the potential of cold thermal crack developments and brittle shear failure behavior in wintertime

Proof of concept of high-rate decentralized pre-composting of kitchen waste : optimizing design and operation of a novel drum reactor

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In situ spectroelectrochemistry and colour measurement of a complementary electrochromic device based on surface-confined Prussian blue and aqueous solution-phase methyl viologen

This article was published in the journal, Solar Energy Materials and Solar Cells [© Elsevier B.V.] and the definitive version is available at: http://dx.doi.org/10.1016/j.solmat.2011.11.052The fabrication, in situ spectroelectrochemistry and colour measurement of hybrid electrochromic devices (ECDs) based on a surface-confined metal hexacyanometallate – Prussian blue (PB, containing the iron(III) hexacyanoferrate(II) chromophore) – and aqueous solution-phase methyl viologen (N,N´-dimethyl-4,4´-bipyridylium) are described. In the ECDs, the initial (‘off’) bleached state is set with PB in its reduced form and the methyl viologen as the di-cation. Switching to the coloured state (‘on’), forms the mixed-valence iron(III) hexacyanoferrate(II) chromophore on oxidation of iron(II) hexacyanoferrate(II), with simultaneous reduction of the methyl viologen dication to form a mixture of the radical cation monomer/dimer. Using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, the colour stimulus of such ECDs and the changes that take place on reversibly switching between the colourless and coloured states have been calculated from in situ visible region spectra recorded under electrochemical control. The concentration of the solution-phase methyl viologen and its diffusion to the cathode controlled both the proportion of surface-confined (reduced) PB that is switched to the blue form and the overall ECD changes. For the ECDs’ ‘on’ states, the CIELAB 1976 color space coordinates for a D55 illuminant were L* = 60, a* = 3 and b* = −46, and L* = 49, a* = 9 and b* = −59, respectively for 5 and 10 mM methyl viologen solution concentrations. The low a* and high (negative) b* chromaticity coordinates quantified the overall ECD colour stimulus of the ‘on’ state as being deep blue, with a broad absorption across the visible spectral region. Combination of the methyl viologen system in the ECDs served to remove the green tint perceived in single film PB. CIELAB 1976 colour space coordinates showed that the ECDs were fully transparent and nearly colourless in the ‘off’ states, with L* = 100, a* = 1 and b* = 1. The changes in the transparency were 83.0% (5 mM methyl viologen) and 93.1% (10 mM methyl viologen) between the ‘off’ (bleached) and ‘on’ (coloured) states of the ECDs

A new test procedure to evaluate the performance of substations for collective heating systems

The overall heat demand of a single dwelling, existing out of space heating and domestic hot water production, decreases due to higher insulation rates. Because of this, investing in efficient and renewable heat generation becomes less interesting. Therefore, to incorporate renewables or residual heat on a larger scale, district heating or collective heating systems grow in importance. Within this set-up, the substation is responsible for the interaction between local demand for comfort and overall energy performance of the collective heating system. Many different configurations of substations exist, which influence both local comfort and central system performance. Next to that, also hybrids exist with additional local energy input. To evaluate performance of such substations, a new experimental-based test procedure is developed in order to evaluate these different aspects, characterized by the two roles a substation has, namely as heat generator and as heat consumer. The advantage of this approach is that an objective comparison between individual and central systems regarding performance on delivering local comfort can be executed experimentally. The lab set-up consists out of three different subsystems, namely the central system, the domestic hot water consumption and the local space heating. The central system can work with different temperature regimes and control strategies, as these aspects have proven to have the largest influence on actual performance. The domestic hot water system is able to generate similar tap profiles according to eco-design regulation for domestic hot water generation. The space heating system is able to demand a modular heat load

A new test procedure to evaluate the performance of substations for collective heating systems

The overall heat demand of a single dwelling, existing out of space heating and domestic hot water production, decreases due to higher insulation rates. Because of this, investing in efficient and renewable heat generation becomes less interesting. Therefore, to incorporate renewables or residual heat on a larger scale, district heating or collective heating systems grow in importance. Within this set-up, the substation is responsible for the interaction between local demand for comfort and overall energy performance of the collective heating system. Many different configurations of substations exist, which influence both local comfort and central system performance. Next to that, also hybrids exist with additional local energy input. To evaluate performance of such substations, a new experimental-based test procedure is developed in order to evaluate these different aspects, characterized by the two roles a substation has, namely as heat generator and as heat consumer. The advantage of this approach is that an objective comparison between individual and central systems regarding performance on delivering local comfort can be executed experimentally. The lab set-up consists out of three different subsystems, namely the central system, the domestic hot water consumption and the local space heating. The central system can work with different temperature regimes and control strategies, as these aspects have proven to have the largest influence on actual performance. The domestic hot water system is able to generate similar tap profiles according to eco-design regulation for domestic hot water generation. The space heating system is able to demand a modular heat load

Performance evaluation of different micro-CHP configurations in real life conditions and the influence of part load behaviour

Micro-cogeneration (micro-CHP) is an emerging technology to reduce the non-renewable energy demand in buildings and reduce peak loads in the grid. Within building applications internal combustion engines, Stirling engines and CHPs based on fuel cell technology are mostly used. The heat and electricity demand here is often characterized by a strong fluctuation over time. The design and control of micro-CHP in buildings is therefore often more challenging in order to achieve its nominal efficiency. In a recently ended research project, different micro-CHP-technologies were evaluated based on on-site measurement campaigns. In practice, micro-CHP is hardly ever used as single technology to deliver the necessary heat. A poor hydronic design can strongly reduce the number of operating hours of the CHP and even its performance, which is influenced by e.g. return temperature. In this paper the performance and behaviour of different technologies are discussed with a strong focus on the part load and start-stop behaviour. The necessary insights are provided with respect to system integration and control and are illustrated with a discussion on the executed measurement campaign in the region of Flanders

Thermal performance of a controllable pavement solar collector prototype with configuration flexibility

Solar energy harvesting as a renewable and sustainable energy source has been widely investigated in recent years across engineering fields. The use of Pavement Solar Collectors (PSC) can lead to clean energy production, an increase in road safety, prolong the service life of asphalt pavement, and can mitigate the Urban Heat Island (UHI) effect. This study describes a controllable large-scale research PSC prototype with high configuration flexibility, and full monitoring capability at the University of Antwerp, Belgium. Since small- or laboratory-scale setups do not reflect the behavior of actual projects, the present paper investigates the thermal response of a large-scale PSC in the Western European climate, including heating load, heat extraction capacity, and asphalt surface and profile temperature changes during heating and cooling experiments. The study shows that a low supply temperature compared to high (14 °C vs. 28 °C) can reduce the depletion rate of the stored thermal energy in borehole thermal energy storage up to 7 times. The sensitivity analysis indicates that an increase in flow rate from laminar to transient regime requires twice as much thermal power compared to the same flow rate changes within transient and turbulent regimes. The maximum average daily efficiency of the PSC could reach 34% with a flow rate of 4 l/min. The experimental results showed that increasing the pipe length from 50 m to 200 m reduces the cumulative power extraction capacity by up to 48%. Furthermore, the PSC system shows great potential in reducing the asphalt surface temperature (up to 12 °C) to mitigate the UHI effects. Finally, the PSC system effectively controls the temperatures of the interface zones to reduce the rutting distress in the summertime and lower the potential of cold thermal crack developments and brittle shear failure behavior in wintertime

The Many Faces of Time in Modern Literature

status: publishe