Low and zero carbon technologies – what does this mean and what are the options?

Carbon-neutral and Net-zero Carbon are two similar terms. In both cases, parties are working to reduce and balance of their carbon footprint. However, Carbon-neutral refers to balancing out the total amount of carbon emissions, while Net-zero Carbon means no Carbon emission from any activity. Most of the industries and governments become Carbon neutral through the purchase of Carbon credits. While Carbon removal is only a long-term solution, implementing technological improvements/ innovations plays a major near-term role in achieving Net-zero Carbon.

According to the 2022 UK greenhouse gas emissions report issued by the Department for Energy Security & Net Zero identifies; Transport (112.5 MtCO 2 ), Energy supply (82.2 MtCO 2 ), Business (61.9 MtCO 2 ) and residential (56.4 MtCO 2 ) as the largest Cabon emission sectors.

When it comes to buildings (for both businesses and residential), the reduction of Carbon emission needs to be targeted for embedded Carbon and Operational Carbon.

Embedded Carbon includes all the Carbon emitted in material (used for building construction) production. Actions are then required to reduce Carbon from raw materials and in production stages:

1. Increasing the recycled content of the final material.
2. Reducing energy demand for material processing e.g. Improving the total system efficiency by using highly efficient machinery and optimizing the production layout/procedure.

Greater energy efficiency and use of renewable sources play a major technical role in the efforts for decarbonisation at the operational stage as it includes Carbon emitted during the whole life of a building. Options to reduce this energy usage include:

1. Design efficient and optimised building systems by following guidelines such as Chartered Institute of Building Services Engineering (CIBSE), American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) or London Energy Transformation Initiative (LETI).

2. Use of LED lighting.

3. Purchasing of equipment with higher energy efficiency ratings (e.g.: Energy Star Rating)

4. Envelope improvement: Installation of thermal insulation (e.g.: Mineral wool, fibreglass, etc.) with adequate thickness and use of double-glazed windows will help keep the heat inside the building. This in turn will reduce heat loss from the building and will reduce the energy requirement for heating.

5. Improve the efficiency of the heating, cooling and ventilation systems
a. Air Source Heat Pumps (ASHPs): ASHPs absorb heat from ambient air and generate hot water which then either be transferred directly to radiators or to a hot water cylinder. The average heating efficiency of an ASHP, determined by the coefficient of performance (COP), is around 2.8.
b. Variable Refrigerant Flow (VRF) Systems: Commonly used to provide heating (and/or cooling) for multi-story buildings with high heating/cooling requirements. VRF systems absorb the heat from ambient air and transfer it into the building via refrigerant. The efficiency ranges mainly between 2.9-4.4.
c. Heat Recovery Ventilation (HRV): This system is used for buildings that require both exhaust and fresh air supply. The HRV unit recovers the residual heat from the exhaust gas to pre-heat (or pre-cool) the fresh air intake. This helps reduce the heating/cooling requirements while in some cases can manage the space temperature on its own.

6. Photovoltaic (PV) Solar Panels are commonly associated with buildings due to the convenience of installation. PV panels are increasingly more efficient at converting the sun’s rays into electrical energy and are best located on the building roof to avoid shading from surrounding buildings. There is no guarantee that the excess power can be sold back to the utility provider so the PV capacity should be designed for supplying base load or Lithium-ion batteries could be an option.

Using a single measure (mostly by the installation of solar PV) or a combination of the above technologies a building can reach low or zero Carbon status. However, it is best to carry out either an energy audit or an energy simulation to identify the cost-effective method for a building to meet its Carbon reduction targets.

News article prepared by BEM Services – See https://www.bem-services.co.uk/ for more information.

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