Low-Carbon, Resilient Water Heating For Post Graduate Student Accommodation
Scala is a new three-story accommodation development for the University of Bath. Co-located with the larger Courtyard Block and with a centralised plant room, the project delivers modern living for postgraduate students. Totalling 96 rooms, each household boasts five to ten ensuite bedrooms sharing kitchen facilities. There are also a small number of studio rooms, with their own kitchenette and bathroom.
The Scala project was at Stage 4 design with the developer/consultant with an initial domestic hot water (DHW) system based on air source heat pumps (ASHP) when LDM Building Services, a specialist in commercial heating, water, ventilation, and air conditioning, was contracted with authority to deliver design and build for the project. LDM felt the original specification appeared oversized, and on further investigation, there were concerns that it might not deliver on requirements with ASHP alone, a common occurrence when working with higher temperatures required for commercial-scale DHW systems. On review, it became apparent to the LDM engineering team that there was an opportunity to deliver a system within the established budget that could also offer greater reliance through the application of a hybrid system that leveraged both ASHP and electric boilers.
Aware of Adveco’s expertise in design and supply of such a hybrid system LDM worked in conjunction with Adveco’s design team, obtaining a new system design proposal, which was then overlaid by LDM’s engineer onto the original plans and adjusted to fit what was a very small plantroom space allocated for the DHW system.
LDM made use of the architecture, which created a first-floor overhang providing ground-floor space suitable for the location of an Adveco L70 ASPH. The L70 is a high-capacity air-to-water monobloc heat pump designed to provide high-temperature hybrid domestic hot water (DHW). Rated 70kW for typical UK operation at 5°C but climbing to a maximum 90 kW from a single compact unit, the L70 is perfect for larger-scale commercial applications such as student residences and can also operate as part of a cascade installation for projects demanding greater capacity.
Given the proximity to the student accommodation and consideration of noise LDM conceived and fitted a timber acoustic enclosure and ducting to direct away airflow. This improved the already relatively quiet operation of the L70 ensuring residents would not be disturbed by the daily operation, especially at night.
When as ASHP is used to generate preheat for the building’s water greater storage, greater efficiency is achieved at lower temperatures. This necessitates the use of larger water storage to avoid system undersizing that fails to meet daily demands. Given the limited plant room space, Adveco helped specify a compact system option consisting of an MSS1000 cylinder acting as a system buffer for the ASHP and a high-grade stainless steel SSB1000 storage buffer tank used to expand the dump load capacity of the water heating installation. A MB0050 Plate Heat Exchanger and pump kit, connected the preheat with the top-up heating. A GLC 750 glass-lined indirect tank that supports working temperatures of up to 85°C and 10 bar system pressure was paired with a compact wall-hung ARDENT S36 electric boiler creating an indirect water heater. The ARDENT provides additional, sustainable electric system top-up year-round ensuring consistent water temperatures that meet the safe operational demands of a commercial system, and is able to achieve temperatures as high as 80°C if faster recovery is required. Heating within the ARDENT is provided by three 12kW elements, smartly balanced to supply up to 36 kW of heating. In typical operation, balanced use of the elements extends the operational lifespan of the ARDENT, and should an element fail at any point the other two will continue to maintain operational temperatures for built-in resilience and assured hot water delivery. This versatile system lends itself perfectly to student-residential living, where demand for hot water can vary considerably over the course of a day and the week as residents exhibit a mixed work/life pattern.
The system was supplied, installed, and commissioned on schedule for handover to the University in September ready for postgraduates to move in at the beginning of the Autumn term. With students now living in the new accommodations and having had a chance to experience the system which was conceived, designed, and built by the developer, Adveco and LDM, the University of Bath is “extremely pleased with the results.”
Looking forward, the University is considering future developments across the campus over the course of the next five years with the thought of rolling out additional ASHP-based systems, based on the Scala system, that can help the University actively address decarbonisation and drive greater sustainability throughout its other campus buildings.