This project will carry out laboratory-based testing of a novel hybrid boiler/heat pump system, combined with a smart control system to provide a view of potential network impacts of large scale roll out of the technology.
An understanding of the network impacts and value to the decarbonisation pathway will be essential to both inform policy decisions on support of smart hybrid technology and ensuring the network is able to efficiently accept the technology roll out if this is to occur.
Benefits
This project will carry out laboratory-based testing of a novel hybrid boiler/heat pump system, combined with a smart control system to provide a view of potential network impacts of large scale roll out of the technology
An understanding of the network impacts and value to the decarbonisation pathway will be essential to both inform policy decisions on support of smart hybrid technology and ensuring the network is able to efficiently accept the technology roll out if this is to occur.
Learnings
Outcomes
The outcomes of the laboratory testing of the compact hybrid boiler / heat pump system are set out below:
The tests were carried out using Kiwa Energy’s Dynamic Heat Loss Test Rig (DHLTR). Two sets of tests were carried out:
- Using the Sime hybrid unit’s standard manufacturer controls;
- Using an advanced smart controller from PassivUK.
The hybrid unit was connected to the DHLTR, which simulates the heating load and ambient conditions on a wide range of property sizes. Tests are normally run for 24 hours with specified property size, radiator configuration and external temperature conditions. Since the Passiv control system ‘learns’ the property’s thermal characteristics, the tests were run for longer to ensure the property was fully characterised. Tests with the Passiv controller were performed over 4 days using the first 2 days to allow the controller to ‘learn’ the thermal characteristics of the property. The final 2 days represented the actual system performance. With the standard manufacturers controller, tests were conducted over 2 to 4 days, again using the last 2 days to represent the actual performance. Two property sizes were simulated under three different weather conditions, and the system performance was measured.
The Sime room thermostat / controller switched at about 1 to 1.5 K lower than the room thermostat set point. Two separate units were tested with both showing the same issue; therefore, it was decided that no correction was to be made during the tests to allow for this. The Passiv system controlled the temperature very accurately.
Direct energy to heat efficiencies ranging from 79% to 181% were observed, with the highest efficiencies found for the smaller property using the Passiv controller during the April test conditions. The average efficiency across all external temperature profiles for the Passiv controls in the smaller property equated to 132%.
For the larger property, the Passiv controlled system used more energy in the appliance than the Sime controlled system. However, the temperatures achieved were much closer to the required target of 21 °C and the Sime controlled system required significant additional supplementary heating to achieve the same comfort levels. When corrections were made to adjust heating to the target temperature, the Passiv controlled system used between 47 and 95% of the direct energy used by the Sime controlled system. The efficiency of the Passiv controlled system in the larger property ranged from 84% in winter to 149% in the April scenario. The average efficiency across all external temperature profiles equated to 110%.
Network Impact Modelling
The behaviour of the compact hybrid system and the results of the laboratory testing were then incorporated into DNV’s Real Time Networks (RTN) model. This provides insight into the impact that a wide scale rollout of the technology would have on gas demand throughout SGN’s Strood network. It also allows for comparison between the compact hybrid appliance and other technologies, such as a traditional hybrid heat pump.
The model contains a breakdown of property types present in the network area. As the laboratory testing focused on smaller properties, it was only appropriate to model a rollout to one- and two-bedroom flats and two bed terraced and semi-detached houses. Although the appliance is suitable for larger properties, its behaviour would be significantly different compared to those tested in the lab and therefore is not appropriate to include these property types in the modelling.
Two scenarios of 50 and 100% penetration rates of the technology were modelled with the impacts on network flows described below:
- A reduction in the peak morning and evening flows, compared to a standard boiler, are present for both a 50% and 100% penetration rate of the Sime unit. A larger reduction was observed for the 100% rate, as expected.
- Outwith the times of peak demand, there are slightly increased network flows observed for the compact hybrid compared to a standard boiler. This may be due to the Passiv controls ensuring the set temperature of 21 °C is constantly met, whereas the standard boiler was operating in a bimodal fashion.
- Across the 24-hour period there is an overall reduction in flow when the Sime unit is widely rolled out:
- 50% Penetration Rate Flow Reduction = 391 scm
- 100% Penetration Rate Flow Reduction = 1548 scm
- The number of properties that the appliance was applied to in the model represents ≈15% of the domestic properties in the Strood network, with their annual gas consumption (AQ) representing ≈10% of the total for domestic properties. In order to get a more accurate representation of the network impacts, lab testing for larger property sizes would be required. This would capture a higher percentage of properties in the Strood network area and therefore a greater understanding of the impacts of a widescale rollout. Additionally, the scale of the RTN model could be expanded to cover larger network areas such as whole cities, LDZs or even all of GB. Again, providing insight into the impacts on the network that a significant rollout of new heating technologies could have.
Lessons Learnt
The testing regime experienced a delay due to a faulty appliance and the time it took to source a replacement from the manufacturer. In the future, for any similar laboratory testing of an appliance discussions will be had with a manufacturer up front to determine the process for sourcing a replacement should any faults occur.