Article summary and reader response draft 2 - District heating and cooling systems

In the website "District heating and cooling systems", ENGIE(2013) emphasized its role in providing heating and cooling systems worldwide and describes how its systems utilize renewable energy to conserve the environment. The website also mentioned that the renowned urban climate control system company Tabreed, had concluded ENGIE as the biggest supplier of urban cooling networks across the globe. The website stated that from 2018, ENGIE has strived to increase the use of renewable energy to 50% in European urban networks. With renewable energy, ENGIE heating and cooling systems generate heat and chilled water and supply it to buildings through a dispensing and a returning pipeline. The website also mentioned that the ENGIE heating and cooling system has successfully reduced greenhouse gas emissions through utilizing biomass, geothermal, and marine thermal energy. And as compared to conventional air conditioning, ENGIE adopts a free cooling system to reduce CO2 emissions, electricity, water, and energy consumption.

While I agree the use of renewable energy in district cooling contributes to environmental conservation, seawater air conditioning does create adverse effects on the environment.

District cooling with seawater is a technology that is making significant strides in aiding energy conservation. Due to its lower temperature nature, seawater is an ideal source for heat exchangers in the cooling system. However, by adopting seawater for district cooling, heated water from the building will be exchanged with seawater via a heat exchanger and dispenses warm water back to the ocean. Thus, contributing to a higher ocean temperature, which may not be adaptable for marine life. According to the article "Keeping Chilled in a Warming World" by Hunt(2019), he highlighted that the return of seawater to coastal ecosystems should be handled with care to minimized the impact on marine life. In addition, the article also stated that the ocean air outlet might receive a thermal shock and increased nutrients. Therefore, environmental contamination can be contributed by these factors, posing a threat to the ocean environment.

Furthermore, utilizing metal and alloy pipes in seawater district cooling is prone to corrosion. Due to the high concentration of electrolytes in saltwater, electrons from the seawater attracts metallic ions. As a result, the contact between metal ions and seawater leads to corrosion and emits toxic substances such as sulfur dioxide and carbon dioxide into the atmosphere. A conference paper “Corrosion and Protection of Metal in Seawater Desalination” by Hou, Gao, Cui, and Yin (2017), also highlighted that the corrosion of metals and alloys in seawater could lead to environmental pollution due to the potential leakage of toxic substances. Therefore, the use of seawater for district cooling should be considered in light of its negative impact on the environment.

Despite the negative impact created using renewable energy in district cooling, it is undeniable that the system benefits are much greater than the disadvantages. An example would be Singapore. As Singapore is one of the countries with a hot climate, conventional air conditioning is heavily reliant on buildings, resulting in global warming due to heat emissions. Therefore, district cooling is used in Singapore to contribute to a sustainable environment, as demonstrated in Marina Bay Sands. According to the SP Group(n.d.) website, it stated that their district cooling system in Marina Bay saves more than 40% in energy consumption across 20 buildings in the vicinity. Energy efficiency in Marina Bay is also further explained in the article “Below the surface of Singapore lies the future of keeping cool” by McKenna(2020) that utilizing centrifugal chillers with a large cooling capacity in Marina Bay allows the chiller to produce six times the amount of energy than the norm. In addition, Singapore District Cooling's submission paper for the “Global Climate Award 2011” by Tey(2011), mentioned that chilled water production in Marina Bay reduced approximately 23,000 tonnes of CO2 emissions and 1.2 million cubic meters of water annually.

In conclusion, the use of renewable energy in district cooling systems does contribute to environmental conservation. However, a few negative impacts on the environment caused by the seawater district cooling may be overlooked when weighing the pros and cons.

Reference

ENGIE. (2013, February 21). District heating and cooling systems.  https://www.engie.com/en/businesses/district-heating-cooling-systems.

Hou, X. Y., Gao, L., Cui, Z. D., & Yin, J. H. (2017). Earth and Environmental Science 108 (2018). Corrosion and Protection of Metal in the Seawater Desalination, Tianjin, China. https://doi.org/10.1088/1755-1315/108/2/022037

Hunt, J. (2019, January 29). Keeping Chilled in a Warming World. CMarkits.  https://cmarkits.com/archives/2896

McKenna, J. (2020, July 28). Below the surface of Singapore lies the future of keeping cool. Spectra. https://spectra.mhi.com/below-the-surface-of-singapore-lies-the-future-of-keeping-cool#district-cooling-%E2%80%93-a-secret-weapon-in-the-battle-against-climate-change

SPgroup. (n.d.). Cooling & Heating 'Marina Bay District Cooling System'. https://www.spgroup.com.sg/sustainable-energy-solutions/our-low-carbon-solutions/cooling-and-heating

Tey, PK. (2011). District Cooling System at Marina Bay, Singapore[Unpublished manuscript]. Singapore District Cooling Pte Ltd. https://www.districtenergyaward.org/wp-content/uploads/2012/10/District_cooling_Singapore_2011.pdf