The path to the high performance thermal building insulation materials and solutions of tomorrow

Abstract

In todays society there is an increased focus on various energy aspects. Buildings constitute a large part of the total energy consumption in the world. In this respect it is important to have the optimum heat balance in buildings. That is, in a cold climate one wants to have as well thermally insulated building envelopes as possible. However, even in cold climates there might often be relatively long periods with overheating in the buildings, e.g. due to solar heat gains and excessive heat loads from miscellaneous indoor activities. In warm climates overheating is most often the case, e.g. in office work spaces with large window glass facades and extensive use of electrical equipment. Insulation retrofit is among the most cost-effective measures, even more cost-effective than e.g. solar photovoltaics. The traditional thermal insulation materials of today have typically thermal conductivities between 33 and 40 mW/(mK). State-of-the-art thermal insulation includes vacuum insulation panels (VIPs) with conductivities from between 3 to 4 mW/(mK) in fresh condition to typically 8 mW/(mK) after 25 years ageing due to water vapour and air diffusion into the VIP core material which has an open pore structure. Puncturing the VIP envelope causes an increase in the thermal conductivity to about 20 mW/(mK).The main emphasis of this work centers around the possibilities of inventing and developing innovative and robust highly thermal insulating materials. That is, within this work the objective is to go beyond VIPs and other current state-of-the-art technologies. New concepts are introduced, i.e. advanced insulation materials (AIMs) as vacuum insulation materials (VIMs), gas insulation materials (GIMs), nano insulation materials (NIMs) and dynamic insulation materials (DIMs). These materials may have closed pore structures (VIMs and GIMs) or either open or closed pore structures (NIMs). The DIMs aim at controlling the material insulation properties, e.g. solid state thermal conductivity, emissivity and pore gas content. Fundamental theoretical studies aimed at developing an understanding of the basics of thermal conductance in solid state matter at an elementary and atomic level have been addressed. The ultimate goal of these studies is to develop tailor-made novel high performance thermal insulation materials and dynamic insulation materials, the latter one enabling to control and regulate the thermal conductivity in the materials themselves, i.e. from highly insulating to highly conducting. Furthermore, requirements of the future high performance thermal insulation materials and solutions have been proposed. At the moment, the NIM solution seems to represent the best high performance low conductivity thermal solution for the foreseeable future. If robust and practical DIMs can be manufactured, they have great potential due to their thermal insulation regulating abilities.

Reviewing the Learning Process through Creative Puzzle Solving

“…The comments "think beyond normal borders" and "learning to think differently" should especially be noted, e.g. with regard to research on developing new thermal insulation materials, "which requires that we may have to think thoughts not yet thought of" (Jelle et al, 2010). Thus, we may also be reminded about the follow-ing quote from Albert Einstein (various versions exist): "Imagination is more important than knowledge.…”

“…In fact, it has also been used in lectures for illustrating some specific scientific research fields, where one may utilize mathematical and physical functional expressions increasing or decreasing rapidly with specific experimental parameters when attempting to manufacture and tailor-make new materials. A specific example of this is the utilization of the so-called Knudsen effect and equation when exploring the possibilities to make nano insulation materials (NIM) with very low thermal conductivity Gao et al, 2014;Gao et al, 2015;Jelle et al, 2010;Jelle, 2011;Jelle et al, 2011;Jelle et al, 2014;Jelle, 2016b;Sandberg et al, 2013). The paper sheet folding task works very nice for larger audiences, e.g.…”

“…And the more we want to know… and that's the whole fun of it, scientific research included! ", representing a modified extrapolation from a quote by Aristotle, and which in our context was written as a general idea when through research attempting to develop new thermal insulation materials (Jelle et al, 2010), and thereafter also employed for the materials science research pathways and opportunities for building integrated photovoltaics (Jelle, 2016a).…”

Small-Scale Flat Plate Collectors for Solar Thermal Scavenging in Low Conductivity Environments

“…The thermal conductivity of traditional thermal insulation materials like mineral wool, expanded polystyrene (EPS), and extruded polystyrene (XPS) is in the range of 0.033 W/mK to 0.040 W/mK, while polyurethane (PUR) has thermal conductivity ranging from 0.020 W/mK to 0.030 W/mK [1][2][3]. To achieve very low thermal transmittance, U-value (rate of heat transfer, in watts, across one square meter area divided by the temperature gradient across the surface), high insulation thickness in the range of 40 cm to 50 cm is required [3].…”

“…To achieve very low thermal transmittance, U-value (rate of heat transfer, in watts, across one square meter area divided by the temperature gradient across the surface), high insulation thickness in the range of 40 cm to 50 cm is required [3]. Hence, space and weight constraints limit the application of these materials.…”