UCC School of Pharmacy implements bivalent heat pump retrofit
University College Cork (UCC) is one of Ireland’s oldest universities with a strong track record of sustainability.
Background
Like all public bodies, UCC has targets to achieve a 50% energy efficiency improvement and 51% carbon reduction by 2030. UCC has also set a target of becoming a net zero carbon campus by 2040.
In 2016, UCC introduced a “Saver Saves Scheme” to reward departments for any energy savings made by devolving the financial savings to the Department, which are then spent on environmental projects within that department.
This project involved the installation of electric air source heat pumps for space heating and extract air heat pumps for domestic hot water (DHW). These take advantage of the ongoing decarbonisation of Ireland’s electricity, backed up by gas boilers to operate during very cold conditions – referred to as a bivalent system. The project – from feasibility to commissioning – took 24 months. The project received capital funding from SEAI’s SSRH grant scheme.
This initiative is projected to deliver an 83% reduction in CO₂ emissions by 2030, contributing to a 4% decrease in UCC’s total Scope 1 and 2 emissions.
The School of Pharmacy building was opened in 2006 and is therefore relatively energy efficient. Low temperature hot water (LTHW) was provided by 2no. 865 kW gas-fired condensing boilers manufactured in 2005. These supplied heat to fan coil units (FCUs), air handling unit (AHU), underfloor heating, radiators and a 500L domestic hot water (DHW) calorifier.
The DHW demand is low, serving wash hand basins. The FCUs are in the labs and are used to preheat makeup air drawn in through the façade when a fume cupboard is on in a lab. The lecture theatre has an AHU with thermal wheel for heat recovery.
To establish its suitability for a low temperature heat pump, UCC completed a trial operating the LTHW system at 50℃ over two heating seasons. The 500L DHW cylinder was heated by direct electric immersion heaters. At that time a study was commissioned to assess the feasibility of a heat pump installation; this established the technical considerations, budgetary cost, and energy and carbon impact.
The building is relatively modern, well-maintained, and in good overall condition. Heating trials had demonstrated that occupied areas retain heat effectively, with minimal losses. Given the presence of older, less efficient buildings across the campus and the limitations on available capital funding, the Estates Office has identified other buildings as higher priorities for comprehensive fabric upgrades.
By strategically replacing the end-of-life boilers with a bivalent heating system, UCC not only addressed critical equipment renewal but also achieved a high return on investment in terms of cost per tonne of CO₂ abated, compared to a ‘fabric first’ approach.
The Project
UCC engaged PowerTherm Solutions to complete a heat pump feasibility study, using historical gas profile data and boiler efficiency to calculate the space heating load.
As the building was tested to operate at 50 ℃ flow temperature over the previous winter, this gave confidence that the building would not be cold at the relatively low operating temperatures typical of a heat pump.
As a result, a bivalent parallel system was feasible (i.e. heat pump and boilers operating together in very cold weather) as opposed to bivalent alternate (i.e. only the boiler in very cold weather and heat pump in milder weather).
Furthermore, the overall project cost of installing slightly larger heat pump was marginal; as a result the heat pump was selected to a bivalent temperature of 3℃ rather than the more typical 6℃.
The feasibility study established that by operating in bivalent parallel, up to 95% of the annual space heating demand could be satisfied by the heat pump. The balance would be provided by gas boilers working with the heat pump in very cold weather.
The final design, prepared by PowerTherm Solutions, included;
- 2no. 148kW heat pumps, with variable speed drive (VSD) controls, low Global Warming Potential (GWP) refrigerant and building automation and control network (BACnet) comms to building management system (BMS).
- 3no. 140kW wall hung boilers for peaking and backup (the existing boilers being end of life).
- Buffer vessel, and new secondary circulation pumps with BACnet comms to BMS.
- 4kW DHW exhaust air heat pump using tempered air in the plantroom as its source. It has a 450L volume with integrated 2no. 2kW electric immersions and a backup 6kW immersion.
The BMS in the building was recently upgraded to a cloud based Tridium system. This allowed for BACnet comms to the BMS and circulation pumps giving more detailed insights into how the system performed and logs metering data.
Project Cost and SEAI Support
The level of grant funding from the SEAI SSRH scheme is linked to the design system SCOP (LTHW and DHW system combined), which was calculated to be 3.71 at design stage with a resulting grant level offer of 35%. Based on eligible costs at project tender stage of €273,533, the SEAI committed €95,736.55 in funding.
The total project cost, including consultancy fees, boilers upgrades, and other non-eligible costs was €381,000. All costs exclude VAT.
Results
The main results are below and suggest the heat pump is likely to meet 95% of annual space heating needs.
| Period | Dec '24 - Feb '25 | Mar - May '25 | Dec '24 - May '25 |
| Days | 77 | 77 | 154 |
| Heat pump's seasonal performance factor | 2.5 | 2.7 | 2.6 |
| Boiler's seasonal efficiency | 88% | 88% | 88% |
| % of heat from heat pump | 80% | 100% | 88% |
The heat pump measured Seasonal Coefficient of Performance (SCOP) is 2.6, which is below the nominal SCOP of 3.7 (European regulation 813/2013; medium temperature application). The Seasonal Coefficient of Performance is a broader way of measuring the efficiency as it’s carried out over an entire heating season.
The metering plan implemented will provide detailed insights into the system’s operational performance. The UCC team will continue to refine and optimise the heating system by adjusting and developing optimal control strategies to close the gap between actual and design SCOP. Full optimisation of the heat pump integration can require approximately two heating seasons.
The CO2 savings for the DHW and space heating systems are 59% based on published 2023 electricity conversion figures. However it is expected that this will increase to 83% by 2030 due to the addition of renewable generation onto the grid.
The costs and benefits of the different options are summarised in the table below. It illustrates that the bivalent system is 27% less expensive than a heat pump only system but can achieve similar euro and carbon savings.
| Indicative | Gas Boilers | Bivalent (As Installed) | Heat Pumps |
| Heating System | 4 boilers | 2 heat pumps + 3 boilers | 3 heat pumps (Doesn’t include cost of fabric upgrades) |
| Capex (ex. VAT, incl. Fees) | €83,000 | €381,000 | €477,000 |
| Expected gas (kWh) | 628,635 | 10,114 | 0 |
| Expected elec (kWh) | 0 | 180,126 | 183,446 |
| tCO2/year (in 2030) | 116 | 33 | 32 |
| Energy Cost | €34,575 | €40,184 | €40,358 |
Insights & Learnings
Bivalent heating systems are recommended in retrofits due to their relative cost-effectiveness, reduction in overall project complexity and cost, and resilience. In particular:
- They allow the LTHW system to operate at a higher temperature on boilers in very cold weather, avoiding the need to upgrade all heat emitters or extensively upgrade the building fabric.
- They reduce the overall electrical capacity requirement, both MIC and building electrical infrastructure.
- The building LTHW system is operated at 50 °C over the course of a heating season to identify the weather conditions, at which this is inadequate and identify cold points. Outside and space temperate sensor data should be logged and stored by the BMS for future analysis. Complaints and cold points should be recorded.
- Metering data (15-minute intervals) should be obtained for the thermal, electrical and DHW cold feed to ensure accurate design.
- Time and budget should be allowed for post-commissioning review and updates to controls.
- The controls contractor should provide a detailed description of system control early in the project for review and comment by the design engineer.
Support scheme for renewable heat (SSRH)
This support scheme provides financial support to help businesses and organisations move from fossil fuels to renewable heating.
Find out more about support scheme for renewable heat (ssrh)
