Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 72 (2015) 307 – 309
International Scientific Conference “Environmental and Climate Technologies – CONECT 2014”
First steps to develop biomimicry ideas Ruta Vanaga*, Andra Blumberga Riga Technical University, Institute of Energy Systems and Environment, Azenes iela 12/1, Riga, LV 1048, Latvia
Abstract There is urgent need for new building insulation materials or building thermal envelope concepts while it is often economically not feasible to achieve nearly zero energy level for buildings in northern climate. The purpose of this study is to research and create solution for applicable facade system or wall construction itself that has dynamic optical and dynamic properties that will adapt to external weather conditions and will be able to react to different outdoor and indoor temperature and lighting conditions using biomimetic principles avoiding the necessity for additional energy input. The goal of such solution is to gather the energy of Sun in summer for heating in winter. © Published by Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license ©2015 2015The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Riga Technical University, Institute of Energy Systems and Environment. Peer-review under responsibility of Riga Technical University, Institute of Energy Systems and Environment Keywords: thermal envelope; climate adaptive building shell; energy efficient building; biomimicry
1. Introduction One of the actions to achieve the EU goal to reduce CO2 emissions by 20 % below the 1990 level is concentrated on the building sector as it accounts for 40 % of total energy consumption in the European Union. EU Directive 2010/31/EU on the energy performance of buildings sets the target – all new buildings have to be nearly zero energy buildings (NZEB) by 31 December 2020. NZEB are defined in the Directive as buildings that have very high energy performance and nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby. Cost optimality studies prove that, in Northern climates, even with the materials with highest performances it is harder to achieve reasonable nearly zero energy building level both economically and in terms of resource
* Corresponding author. E-mail address:
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1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Riga Technical University, Institute of Energy Systems and Environment doi:10.1016/j.egypro.2015.06.044
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consumption and life cycle. In order to achieve NZEB level in a Northern climate, new solutions for the thermal envelope have to be invented. 2. Shift of a paradigm in thermal envelope As the definition mentioned above suggests, the NZEB building itself has to become an energy producer. One solution is to add additional technologies to produce energy on site, but another is to use the construction needed to make an enclosure, to be a part of the energy balance – building thermal envelope has to become „active”. Climate adaptive building shells (CABS) have been discussed in relation to energy efficiency in buildings. This concept offers a shift from static systems in thermal envelopes those that are dynamic – as Loonen et al. [1] defines: „CABS has the ability to repeatedly and reversibly change some of its functions, features or behavior over time in response to changing performance requirements and variable boundary conditions, and does this with the aim of improving overall building performance”. The new nature inspired discipline could help to find innovative approaches for building shells. Biomimicry searches for solutions of human problems in nature (from the Greek words bios, meaning “life,” and mimesis, meaning “to imitate” [2]). In the latest biomimetic studies on the building thermal envelope, it has been compared to the outer shells in nature as those face the same weather conditions and deals with the same tasks [3] – to diminish heat loses via thermal envelope (insulation, metabolism, hibernation), to store energy, to generate energy, to prevent overheating with the ability to correspond to the varying conditions. There are two design metodologies defined in biomimicry í «biology to design», when the biological principle is the source for design ideas and «challenge to biology» seeking answers in biology for human problem [4]. 3. Inventing systems with dynamic parameters using biomimetic approach The purpose of this study is to research and create a solution applicable for a building’s facade or wall construction that has optical and dynamic properties that will adapt to external weather conditions and will be able to react to different outdoor and indoor temperatures and lighting conditions using biomimetic principles avoiding the necessity for additional energy input. Zogla et al. [5] have created an example how to apply phase changing material on a wall reducing energy losses in winter time in cold climate using latent energy of water – ice phase change. In this article the focus is on gathering as much energy as possible in during hot season and releasing it in cold season. In order to diminish heat loss through the thermal envelope, it is necessary in the cold season to absorb as much solar energy as possible, but in the summer – to prevent overheating of the building, solar heat gains have to be avoided or stored. Different materials can be characterized according to spectral absorption coefficient. Ones with dark color absorb more wave lengths and energy; those of light color – absorb particular narrow field of wave lengths and reflect energy. Altering the color of the material according to external conditions, thus changing its property would change or even increase its energy performance – the ability to absorb energy. Searching for an answer to the defined problem – need for color changing energy gathering or producing material – in nature as the “challenge to biology” approach suggests, the example of brittle star surface properties has been chosen for further research – it has color changing properties in the daily timescale – during the day it is dark, during the night it changes to white [6, 7]. The surface of brittle sea star is covered with protuberances that function like lenses and are arranged in fine array. Lenses capture the energy in focal point, but holes in valleys after receiving neural signal release pigment that coats the brittle star, making it black. In a graphical way the functioning principle and the surface of the brittle star is given by Chen Po-Yu et al. [8] in Fig.199). These properties will be further developed in this research in two directions: 1. to create a color-changing facade system that absorbs or reflects solar energy based on a fluidic flow covering or revealing lenses; 2. to create a facade system with lenses in order to gain more solar energy and store it using PCM, following the principles in brittle star structure - natural optical system`s ability to optimize the transmission through the lenses and combine it to the fluidic flow for energy storing.
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Developing the second idea, there should be 5 basic phases incorporated in facade system simultaneously preventing system from energy loses (Fig. 1).
Lensesgathering
HeatingupPCM
Energytransfer
energy
inthefocalpoint
inPCM
Energystorage
Energyrelease
Fig. 1. The principle of thermal envelope solution – gathering and releasing energy.
To gather energy in focal point more effectively Fresnel lenses are chosen for further research as these have higher optical strength and therefore higher temperature in focal point is easier to achieve with the same lens surface area projection. 4. Further discussion The challenge of using PCM in facade system is: 1) to make the solution highly effective operating with high temperatures, 2) it has to be cyclic, 3) and not losing PCM properties over these cycles. The next step for facade system using lenses for gathering energy will be to add the idea from brittle star surface – fluidic flow covering and revealing lenses in order to control the amount of energy gathered. References [1] Loonen R, Trcka M, Costola D, Hensen J. Climate adaptive building shells: State-of-the-art and future challenges. Renewable and Sustainable Energy Reviews 2013; 25: 483–493. [2] Benyus J. Biomimicry: Innovation inspired by nature. Perennial, New York, 2002. [3] Gosztonyi S, Brychta M, Gruber P. Challenging the engineering view: Comparative analysis of technological and biological functions for energy efficient facade systems. Design and Nature 2010 - Fifth International Conference on Comparing Design in Nature with Science and Engineering, Pisa, Italy,(29.06.2010), 28.-30.06.2010. In: Brebbia, C.A. & Carpi, A. (eds.), Design and Nature V: Comparing Design in Nature with Science and Engineering, Volume 138, WIT press, Southampton, p. 491-502. [4] Life’s Principles. Available at: http://biomimicry.net/about/biomimicry/biomimicry-designlens/biomimicry-thinking/ [Accessed: 12 Apugust 2014] [5] Zogla G, Blumberga A, Kass K. Using latent energy of water-ice phase change to reduce energy losses in buildings in cold climate. Proceedings of the 2013 International Conference on Mechanics, Fluids, Heat, Elasticity and Electromagnetic Fields, 2013. [6] Aizenberg J. New Nanofabrication Strategies: Inspired by Biomineralization. MRS Bulletin 2010; 35: 323–330. [7] Hendler G, Brittlestar color-change and phototaxis ( Echinodermata: Ophiuroidea: Ophiocomidae). Marine Ecology 1984; 5(4): 379í401. [8] Chen Po-Yu, McKittrick J, Meyers M. Biological materials: Functional adaptations and bioinspired designs. Progress in Materials Science 2012; 57(8): 1492í1704.
