Title: The urgent need of Zero Net Carbon commercial buildings to reduce carbon dioxide emission and to limit global warming

Significance:

Global warming imposes as an immediate threat in progression and development of human civilisation. The majority of global carbon dioxide contribution to the climate change is primarily spawned from built environment. With the vest increase in energy consumption, carbon dioxide (CO2), which make up three-quarter of global greenhouse gas (GHG), emission needs to be cut down by 45% by 2030 to avoid the depletion of habitable ecosystem [1]. Hence, the need for buildings with improved building energy performance and reduced building carbon emission is thereby ever-growing. In recent years, zero net carbon buildings (ZNCB) have become a worldwide phenomenon in efforts to lower the carbon footprint worldwide. There are 3 runner-up renewable energy technologies such as photovoltaics (PV) solar cell, heat pump (HP), a device that extract low-grade heat from one source and transfer the heat to another, and Green System (GS), inclusion of plants as the main design element to decrease energy consumption and carbon emission, used to bring down carbon emission from commercial building to zero level [2, 3].

Literature Review:

The most well-known form of renewable energy technologies in ZNCB is photovoltaics (PV), which is the conversion of solar energy to electrical power [4]. Typical light trapping method in the first generation thin-film silicon (SI) based solar cells are by the usage of metallic nanostructures to support surface plasmons which increases light concentration into a think semiconductor layer hence enhancing in light absorption [5]. On the other hand, in the latest generation of PV system, lead halide perovskite solar cells (PSC) have become a large attraction and better alternative in recent time due to efficient average power conversion with tunable bandgaps to complement the absorption by varying the halide ions attributing to strong light absorption and a long large diffusion length [6]. However, limitation of metal halide perovskite solar cells is degradation when exposed to extreme moisture content, oxygen, mechanical stress, temperature increment, sunlight, and reverse bias [7].

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Although PV systems were made to provide electrical energy to a large scale, heat pump (HP) were made to further minimise the usage of renewable energy in energy-intensive operations such as district cooling/heating to reduce net energy consumption hence carbon emission [8]. Amongst the variation of HP systems that had been invented, the most well-known one is ground source heat pump (GSHP) which utilities the natural heat stored in the ground then discharges to the building during winter and releases the heat out of the building during summer [9]. While GSHP is a good renewable energy technology, the suitability and energy efficiency reduces as temperature decreases below 6–7ºC [10].  Therefore GSHP is solely constraint by weather conditions hence problems arise when unanticipated climatic changes happen.

Another form of existing renewable technologies to achieve ZNCB is greenery system (GS). Within GSs, green roof (GR) are popular in passive design aspect to offer insulation, improve thermal performance, and drainage system respectively [11]. Typical green roof system layers consist of vegetation layer, growing medium, filter, drainage (moisture retention), root barrier and finally waterproofing membrane on top of a structural deck [12]. However, green roof experiences structural limitation such as slope of the roof and requires high level of maintenance as the climate conditions on high elevation creates difficult environment for growth and survival of the plants [13]. Nowadays green facades have attracted attention since vertical surface area of the building being larger than the roofs.

Gaps in literature:

–          Noticeable gap is that SI and PSC solar cell still struggle in extreme weather condition. SI based solar cell becomes susceptible to temperature increase and PSC becomes unstable as it experiences degradation.

–          GSHP is highly dependent on the ground temperature thus GSHP requires specific ground source system and local geology to work normally and efficiently.

–          Due to lack in erosion control techniques steep slopes on GS are prohibited

References:

[1] P. Nejat, F. Jomehzadeh, M. M. Taheri, M. Gohari, and M. Z. Abd. Majid, “A global review of energy consumption, CO 2 emissions and policy in the residential sector (with an overview of the top ten CO 2 emitting countries),” Renewable and Sustainable Energy Reviews, vol. 43, pp. 843-862, 2015, doi: 10.1016/j.rser.2014.11.066.

[2] A. Neave, “41 – Heat pumps and their applications,” in Plant Engineer’s Reference Book (Second Edition), D. A. Snow Ed. Oxford: Butterworth-Heinemann, 2002, pp. 41-1-41-9.

[3] E. Cuce, A. B. Besir, and P. M. Cuce, “Low/Zero-Carbon Buildings for a Sustainable Future,” in Low Carbon Transition – Technical, Economic and Policy Assessment, 2018, ch. Chapter 3.

[4] G. Li et al., “High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends,” Nature Materials, vol. 4, no. 11, pp. 864-868, 2005/11/01 2005, doi: 10.1038/nmat1500.

[5] H. A. Atwater and A. Polman, “Plasmonics for improved photovoltaic devices,” Nature Materials, Review Article vol. 9, p. 205, 02/19/online 2010, doi: 10.1038/nmat2629.

[6] M. Saliba et al., “Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency,” (in English), Energy Environ. Sci., Article vol. 9, no. 6, pp. 1989-1997, 2016, doi: 10.1039/c5ee03874j.

[7] C. C. Boyd, R. Cheacharoen, T. Leijtens, and M. D. McGehee, “Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics,” (in English), Chem. Rev., Review vol. 119, no. 5, pp. 3418-3451, Mar 2019, doi: 10.1021/acs.chemrev.8b00336.

[8] K. J. Chua, S. K. Chou, and W. M. Yang, “Advances in heat pump systems: A review,” Applied Energy, vol. 87, no. 12, pp. 3611-3624, 2010, doi: 10.1016/j.apenergy.2010.06.014.

[9] A. M. Omer, “Ground-source heat pumps systems and applications,” (in English), Renew. Sust. Energ. Rev., Review vol. 12, no. 2, pp. 344-371, Feb 2008, doi: 10.1016/j.rser.2006.10.003.

[10] M. Kharseh, L. Altorkmany, M. Al-Khawaja, and F. Hassani, “Analysis of the effect of global climate change on ground source heat pump systems in different climate categories,” (in English), Renew. Energy, Article vol. 78, pp. 219-225, Jun 2015, doi: 10.1016/j.renene.2015.01.017.

[11] K. Vijayaraghavan, “Green roofs: A critical review on the role of components, benefits, limitations and trends,” (in English), Renew. Sust. Energ. Rev., Review vol. 57, pp. 740-752, May 2016, doi: 10.1016/j.rser.2015.12.119.

[12] A. B. Besir and E. Cuce, “Green roofs and facades: A comprehensive review,” (in English), Renew. Sust. Energ. Rev., Review vol. 82, pp. 915-939, Feb 2018, doi: 10.1016/j.rser.2017.09.106.

[13] B. Raji, M. J. Tenpierik, and A. van den Dobbelsteen, “The impact of greening systems on building energy performance: A literature review,” (in English), Renew. Sust. Energ. Rev., Review vol. 45, pp. 610-623, May 2015, doi: 10.1016/j.rser.2015.02.011.