Skip to main content
SLU publication database (SLUpub)
Doctoral thesis, 2023

Chemical and physical incorporation of bio-molecules into wood materials for energy storage

Nazari, Meysam

Abstract

The environmental impact of fossil-based materials in the building industry and significant energy consumption in residential buildings have urged new research areas in using bio-based, renewable and sustainable materials for production of energy smart bio-based envelopes for building applications. This can be achieved by incorporation of bio-based phase change materials (BPCMs) in wood materials for energy storage in residential buildings. In this thesis, an attempt was made to develop a new BPCM based on coconut oil (CO). The oil was converted into free fatty acids (CoFA) by alkaline saponification and mixed with oleic (OA) and linoleic (LA) acid in various proportions to obtain stable compositions with desirable working temperatures. The prepared mixtures were visually, chemically and thermally studied confirming that the combination of CoFA/LA 20:80 was the most suitable combination and used further as BPCM (xLA= 0.2). The new system melts uniformly at 24.8 ºC, and freezes at two points 18 and 22 ºC, with latent heat of fusion of 100 J/g, heat capacity of around 5 J/g K, thermal conductivity of 0.2 W/m K, in liquid and 0.35 W/m K in solid phase and a good thermal stability after 700 intensive cooling/heating cycles. BPCM (xLA= 0.2) was incorporated by impregnation in solid untreated Scots pine and beech and thermally modified pine (TMP), beech (TMB) and spruce (TMS) wood. The impregnability and intensive leakage tests revealed the positive effect of thermal modification on improving permeability and decreasing leakage. A microscopy study showed that rays in both pine and beech were the main pathway for impregnation. The specific heat capacity of unmodified and thermally modified samples before impregnation were similar at around 2 J/g K, which after impregnation, increased to 4-5 J/g K. The introduction of BPCM (xLA= 0.2) led to improved thermal mass and thermal conductivity of the impregnated samples. The latent heat of fusion for impregnated samples was proportional to the amount of BPCM (xLA= 0.2) in the samples. Mold tests showed that BPCM (xLA= 0.2) encapsulated in Chemical and physical incorporation of bio-molecules into wood materials for energy storage studied thermally modified wood species is less susceptible to mold discoloration compared to unmodified samples. A bio-composite consisting of wood particles impregnated with ethyl palmitate ester (EP) as BPCM and a bio-binder was studied. An optimal proportion of 25 % EP was used in the composite to minimize leakage. The composite was thermally stable to a temperature of 200 ºC. The composite thermal characteristics are similar to solid wood impregnated with BPCM. A benefit of the bio-composite was the added-value to less-valuable industrial bi-products involved in the production of energy smart bio-composite for building application, as well as possibility to produce different profiles.

Keywords

bio-based PCMs; bio-based composites; building applications; coconut oil fatty acids; energy storage; ethyl palmitate; impregnation; thermal characterization; wood materials

Published in

Acta Universitatis Agriculturae Sueciae
2023, number: 2023:7
ISBN: 978-91-8046-066-8, eISBN: 978-91-8046-067-5
Publisher: Swedish University of Agricultural Sciences