Energy Recovery & Demand Mitigation

Fuel, Co2, Water Recovery

Three businesses are engaged in the production and processing of fabrics in Newmilns. The firm Haddow Aird & Crerar Ltd specialises in the production of textiles. JS Manufacturing is a specialised textile business that provides fabric procurement, dyeing and finishing services, and theatre textiles. The textiles business Morton Young and Borland Ltd (MYB) specialises in madras (cloth), lace sheers, panels, and blankets. 

Bleaching, dyeing, printing, washing, and finishing, are used to textile products. All these procedures need a considerable amount of water and energy. With the application of different cleaner production techniques, such as the use of waste heat exchangers at process output could recover heat for heating the freshwater. The waste streams from these operations are frequently disregarded without consideration for their importance in recovering water and energy from such streams. [1]

Water is used to produce saturated steam and to cool heated machinery like electric generators. It is necessary to use hot water, up to 80-90 °C, which is then immediately disposed away as hot wastewater after use. The strategy is to reuse the hot wastewater on-site to limit waste output at the source [1].

• As illustrated in Figure 1, the heated wastewater from one step of the process might be collected, screened-filtered, and reused in the same process. The use of heat exchanger at the final output, brings the fresh feed-water into indirect contact and allows heat transfer between hot wastewater and fresh water. 

The usage of both water and energy might be decreased by using this approach to resource recovery. 

For proper functioning of equipment and plants, cooling is a standard industrial practise. Cooling water is used to withdraw heat from specific equipment by conduction. Steam boilers, equipment, and power plant exhaust emissions are the primary industrial sources of waste heat. The traditional power plant's average heat efficiency is between 35-40%, with the remaining energy being lost to the environment as exhaust emissions, conduction losses, and radiation losses. Recovered heat from such streams is important since the combustion of power turbines, power generators, and steam boilers discharged significant amounts of exhaust heat.

• The heat of cooling water is typically lost at cooling towers and recovered during cooling under a closed cycle system. Figure 2 illustrates the process of heat exchange between cooling water of a power generator and process freshwater. The heat in cooling water can be recovered by using a heat exchanger to heat the fresh water before supplying it to processes. 

• By using the waste heat recovery boiler, the exhaust emissions might be utilised to produce saturated steam. The water is first heated outside the tubes, and then saturated steam is created by pressurising the water vapour. As illustrated in figure 2, such boiler can be installed near the exhaust outlet of a power generation or turbine.

• An economizer might be used at a boiler outlet to exchange its contribution to the incoming boiler feedwater. This will recover waste heat from steam boiler emissions. By using this procedure, the thermal efficiency of the steam boiler could be raised while the amount of boiler fuel used could be decreased.

This case study found that an estimated 167,076 m3 of water was saved by reusing waste-water, the fuel was saved in the range of 85,882 MWh, and CO2 was reduced in the range of 15,561 tonnes. [1]

• As a result, Newmilns may reduce its CO2 emissions by 34%, reductions in water use by 25% and fuel use of 28% [13]

Mechanical Ventilation 

Dustacco Engineering Ltd, located in Newmilns, provides process pipework, mechanical fabrication and water-cooling services to many industries. MESH & Saxen both do commercials interior design, supply and installation. West Siphnoic supplies, installs, and repairs roofs on buildings. Vesuvius is an office space. On thing to note is that most of the gas usage in these companies is for heating the space. 

Industrial spaces often require significant amounts of energy to maintain comfortable temperatures, especially during colder months. This can result in high gas usage for heating, which not only contributes to greenhouse gas emissions but also leads to increased operational costs. However, mechanical ventilation systems can provide an effective solution to this problem. By bringing in fresh air from the outside and circulating it throughout the space, mechanical ventilation systems can help regulate temperature and reduce the need for excessive heating. In this way, they can help industries improve their energy efficiency and reduce their environmental impact while still maintaining comfortable working conditions. 

There are different types of mechanical ventilation systems that can be used for heat recovery in industrial spaces. Some of the most common mechanical ventilation systems for heat recovery include: 

• Air-to-Air Heat Pumps: Air-to-air heat pumps are devices that transfer heat from one air stream to another using a refrigerant cycle. They can be highly efficient and are often used in industrial spaces that require simultaneous heating and cooling [3].

• Exhaust Air Heat Pumps: Exhaust air heat pumps are devices that extract heat from the exhaust air stream and transfer it to the incoming air stream. [10]

• Ground-Source Heat Pumps: Ground-source heat pumps are devices that extract heat from the ground and transfer it to the air stream using a refrigerant cycle. [4]

• Indirect Evaporative Cooling Systems: Indirect evaporative cooling systems use a heat exchanger to transfer heat from the incoming air stream to the outgoing air stream. [5]

• Heat Recovery Ventilation (HRV) Systems: use a heat exchanger to recover heat from the outgoing air and transfer it to the incoming air. They can help maintain good air quality by removing stale air and replacing it with fresh, filtered air. [6]

• Plate Heat Exchangers: are devices that use a series of thin metal plates to transfer heat from one fluid to another. In the context of mechanical ventilation systems, they can be used to recover heat from the outgoing air and transfer it to the incoming air. [7]

• Rotary Heat Exchangers: are devices that use a rotating wheel to transfer heat from one fluid to another. [8]

• Run-Around Coils: Run-around coils are devices that use two separate coils to transfer heat from one fluid to another. In the context of mechanical ventilation systems, they can be used to recover heat from the outgoing air and transfer it to the incoming air. Run-around coils are often used in applications where there is limited space for other types of heat exchangers. [9]

The dimensions of the space, the heating and cooling loads, and the desired level of energy efficiency will all be important considerations when choosing a mechanical ventilation system for heat recovery. Which system is best for a certain location and sector may be determined with the assistance of a trained HVAC expert. However, mechanical ventilation using heat recovery such as air-to-air heat pump will have a reduction of around 25% of thermal energy [3]. 

Approximately 80% of the Thermal Gas consumption by the Newmilns Industrial users is suitable for mitigation or conversion to supply via Heat Pumps

As illustrated in figure 4, an Esp-r [14] model generated by the team shows a 37% reduction in energy consumption for sauce heating if building envelope is brought in line with 2012 UK building regulations [15].

Insulation alone would produce a significant reduction in energy consumption and associated cost reduction; this would be a recommendation regardless of the viability of any renewable power installation.  Moreover, a reduction in Thermal Demand is a prerequisite to transitioning to an electrified system via heat pumps.

Conversion to heat pumps with a mean Coefficient of Performance of 2.75 is recommended to keep post electrification costs to a minimum. 

Impact of Energy recovery on the Energy required from the grid

Figures 5 & 6  above show the estimated combined effect of Energy Recovery, Envelope Modification and transition to Heat Pump thermal generation on both peak electrified demand and yearly energy consumption form the grid.

The team estimates this will result in a likely 50% reduction in load to grid, as shown in figures 5 and 6. This broadly agrees with results form D. Katunsky et al.,  Building and Environment, 2013 [16] who estimate that a  "10% to 60% reduction in energy consumption is possible depending upon the building and HVAC performance qualities".  

While this reduction may seem dramatic it is important to note that the positive coefficient of performance of heat pumps allows a significant reduction in the load to grid per unit of thermal energy supplied to any given building. 

Waste Energy Recovery 

Anaerobic digestion can be used to treat a wide range of organic materials, including agricultural wastes, food waste, sewage sludge, and industrial organic wastes. It is an attractive option for waste management because it can reduce the volume of waste, produce a renewable energy source, and reduce greenhouse gas emissions [12]. 

• The population in Newmilns is around 3000​

• 399 kilograms of waste per person in 2020 in UK ​ [11]

• 399 X 3000 ≈  1,197,000 kg of waste  in Newlmins​

• ≈ 1197 tonnes of food waste​

• Digesting 1 tonne of food waste can generate about 300 kWh of energy​ [12]

• Can produce around 359,100 kWh of energy per year. 

A place like Newmilns could benefit from making a contract with a nearby anaerobic digestion company to manage their waste and provide renewable electricity. By providing the waste to the anaerobic digestion company, Newmilns could reduce the amount of waste sent to landfills, which can produce harmful greenhouse gases. In return, the anaerobic digestion company could use the waste to produce biogas and generate renewable electricity, which can be sold back to the town. This would create a circular economy that is beneficial to both parties, as Newmilns would have a reliable source of renewable electricity and the anaerobic digestion company would have a steady supply of organic waste. Overall, this contract would promote sustainability, reduce waste, and provide a reliable source of renewable energy for the community. 

References:

[1] Gadhi, Tanveer Ahmed, et al. “Waste Heat and Wastewater Recovery in Textile Processing Industry: A Case Study of Adopted Practices.” July 2021, vol. 40, no. 3, 2021, pp. 606–616., https://doi.org/10.22581/muet1982.2103.14 [Accessed 1 May 2023]. 

[2] Google My Maps, Google, https://www.google.com/maps/d/u/2/embed?mid=1K0_uu6wy5rpst7GtlqV39QUO_7jJvDNt&ehbc=2E312F&ll=55.77529526624846%2C-4.181918161158415&z=10  [Accessed 13 April 2023]. 

[3] Gram-Hanssen., et al. “Air-to-Air Heat Pumps in Real-Life Use: Are Potential Savings Achieved or Are They Transformed into Increased Comfort?” Energy and Buildings, Elsevier, 10 July 2012, https://www.sciencedirect.com/science/article/pii/S0378778812003118 [Accessed 7 May 2023]. 

[4] “Ground Source Heat Pumps.” Energy Saving Trust, 19 Jan. 2023, https://energysavingtrust.org.uk/advice/ground-source-heat-pumps/ [Accessed 1 May 2023]. 

[5] Cosaf. “Indirect Evaporative Cooling: 80% Energy Usage Reduction.” Cosaf, https://www.cosaf.co.uk/evaporative-cooling/indirect-evaporative-cooling#:~:text=With%20indirect%20evaporative%20cooling%2C%20a,is%20circulated%20by%20a%20fan [Accessed 1 May 2023]. 

[6] “MVHR: Mechanical Ventilation with Heat Recovery: Envirovent.” EnviroVent Ltd, https://www.envirovent.com/products/heat-recovery-ventilation-mvhr/#:~:text=A%20heat%20recovery%20ventilation%20system,warmth%20of%20the%20extracted%20heat [Accessed 1 May 2023]. 

[7] Evans, Paul. “How Plate Heat Exchangers Work.” The Engineering Mindset, 31 May 2020, https://theengineeringmindset.com/how-plate-heat-exchangers-work/ [Accessed 1 May 2023]. 

[8] “Rotary Heat Exchangers.” Swegon, https://www.swegon.com/uk/knowledge-hub/technical-guides/different-types-of-heat-exchangers/rotary-heat-exchangers/ [Accessed 1 May 2023]. 

[9] Run Around Coil. https://www.eceuk.com/our-products/rac/#:~:text=A%20run%2Daround%20coil%20system,air%20coil%20before%20returning%20again [Accessed 1 May 2023]. 

[10] “Exhaust Air Heat Pumps.” Energy Saving Trust, 9 Mar. 2022, https://energysavingtrust.org.uk/advice/exhaust-air-heat-pumps/ [Accessed 1 May 2023]. 

[11] Alves, Bruna. “England: Household Waste Collected per Person.” Statista, 17 Apr. 2023, https://www.statista.com/statistics/322535/total-household-waste-volumes-in-england-uk-per-person/ [Accessed 7 May 2023]. 

[12] “The Official Information Portal on Anaerobic Digestion.” Anaerobic Digestion, https://www.biogas-info.co.uk/. [Accessed 7 May 2023]. 

[13] Ozturk, Emrah, et al. “Improving Energy Efficiency Using the Most Appropriate Techniques in an Integrated Woolen Textile Facility.” 16 Jan. 2020 [Accessed 7 May 2023]. 

[14] A Tour of ESP, www.esru.strath.ac.uk/Courseware/ESP-r/tour/  [Accessed 8 May 2023].

[15] Ministry of Housing, Communities & Local Government. “The Building (Amendment) Regulations 2012.” GOV.UK, 13 Mar. 2012, www.gov.uk/government/publications/the-building-amendment-regulations-2012  [Accessed 8 May 2023].

[16] Katunsky, Dusan, et al. “Analysis of Thermal Energy Demand and Saving in Industrial Buildings: A Case Study in Slovakia.” Building and Environment, 25 May 2013, www.sciencedirect.com/science/article/pii/S0360132313001595  [Accessed 8 May 2023].