Ajeet Singh
Fig. 1. Tea Room at Penrhyn Castle, Bangor, UK serves food and drinks to visitors of the Castle.
With less than a month to go to our Launch Event at Penrhyn Castle, here is a short piece on how the system to recover heat from the wastewater flowing out of the Tea Room’s kitchen works and on how it is performing. You can take a virtual 3D tour and explore the Drain Water Heat Recovery (DWHR) system in here.
Penrhyn Castle is a popular tourist attraction in the Bangor area. On busy days, up to 1500 people visit from all over the world. The Tea Room serves food and beverages to the visitors (Fig. 1).
The pilot wastewater heat recycling system is located directly underneath the kitchen, and it is accessed via the old Coal Yard. The hot wastewater from the kitchen is discharged through vertical drains.
Fig. 2. Shell-Tube type heat exchanger arrangement having counter flow pattern for maximum heat recovery by freshwater from hot wastewater.
A portion of the vertical drain has been replaced by a ‘Shell- tube’ heat exchanger (Fig. 2) made of two copper concentric tubes in which the hot wastewater flows through the inner tube and the cold freshwater through the outer one. The outgoing hot wastewater and incoming cold freshwater flow in opposite directions to take advantage of the maximum difference in temperature, or thermal gradient, and to maximise the thermal exchange. In operation, the system has demonstrated the potential to preheat the cold fresh water beyond 15 ℃ through recovering heat from the hot wastewater. This preheated freshwater is then accumulated in an adjacent 300 liter capacity buffer tank from which freshwater is drawn to meet the ongoing hot water demands in the kitchen. Overall, the system reduces the energy required to heat the fresh water.
Demonstrating the capabilities of the system
The system was designed and developed by the engineering members of the Dwr Uisce Team located in Trinity College Dublin. Working closely with representatives of National Trust Wales, they gathered preliminary data, and facilitated the installation and commissioning of the system.
The engineers monitored the system for a period of 119 days, from 25 February to 22 June 2022: the total energy saving was almost 900kWh which consequently saved 251.63£ of electricity cost associated with water heating. In comparison, the system has saved a maximum of 5 kW of power under limited operational hours during COVID restrictions. Very soon the data for the summer monitoring period will be available, which we expect will show higher energy recovery and therefore savings due to higher number of tourists.
Overall, the installation has payback period of less than 2 and a half years due to savings of beyond 45 kW of waste energy potential daily. Reduced energy demands correspond to reduced carbon emissions: the system saves about 780.27 kg CO2e/year. If replicated in all the suitable commercial kitchens in the UK for example, the energy savings would be in the order of Tera Watts and the carbon footprint of their overall operations would shrink greatly.
The present heat recovery is an example of heat recycling from the kitchen wastewater and contributes to meet the net-zero carbon emission goals of the EU. The energy saving realised by application of waste heat recovery systems in fact would result in reduced carbon emission generated by burning fossil fuels for water heating and attenuate dependency on. Seen the current energy and climate crisis it seems that exploring the potential for wider application should be a no-brainer.
Join us online or in person on October 11 at our Launch Event to discuss with our researchers and other interested parties about opportunities and challenges in this field.