Learnings

Outcomes

Phase 1 Outcomes

• Passiv UK controls successfully integrated with the Sime CHHS, achieving good results controlling the system making extensive use of the heat pump and maintaining stable room temperatures and improved condensing performance from the gas boiler.
• Integration of Passiv UK controls into the CHHS unit presented some minor issues, all of which were resolved through further testing and continued development of the control algorithms.
• Passiv UK controls were able to optimise for improved gas boiler efficiency at lower flow temperatures by increasing the time the gas boiler ran in condensing mode.
• CoP of the heat pump is slightly lower than a standalone ASHP.
• Optimisation against a simulated ‘Agile’ tariff was demonstrated.
• An initial demonstration of “marginal carbon optimisation” was successfully completed.
• Live demonstrations of DNO flexibility services.
• Successful predictions of the outcome of DNO interventions were demonstrated.

Phase 2 Outcomes

Heat Pump Performance.

• CHHS were shown to achieve heat pump utilisation in the range 40%-58% when installed in suitably sized houses.
• Utilisation figure was lower (28-36%) in larger homes.
• CHHS units capable of delivering carbon savings of 30% - 48% when compared with equivalent heat from a gas boiler. Larger homes achieved carbon savings of 20-30%
• Use of the heat pump would not deliver savings on fuel costs under current pricing; heat pump can only deliver less than 5% of the homes heat demand before adding to the running costs.
• One exception site could provide 26% of the home’s heat demand, delivering 22% carbon savings and 4% running cost savings.

Marginal Carbon Optimisation

• Successful demonstration of optimisation against marginal carbon intensity with 13%-53% reduction in carbon emissions compared to control periods. The heat pump only operated when marginal carbon intensity was lower than the gas boiler.

Benefits of large-scale deployment.

• When compared with all heat delivered through heat pumps, deploying CHHS can deliver significant benefits:
  • reduces the requirements for distribution network reinforcement
  • reducing the requirement for peak supply
  • enabling installation of smaller HPs at lower costs.
• Benefits of CHHS systems partially offset by higher system cost due to lower CoP achieved by CHHS.
• Smart CHHS control has distinct benefits:
  • ability to co-optimise the operation of heat pump and boiler components maximising boiler efficiency
  • responsiveness to system conditions (e.g. reducing electricity usage when electricity is scarce on the system despite being able to achieve a relatively higher CoP).
  • Network needs less peak capacity in supply and network infrastructure and a lower volume of flexible options such as energy storage or interconnection.
• Benefit of Smart vs. default control is about £100 annually per CHHS, which can be attributed to savings in:
  • distribution networks,
  • energy storage
  • generation and transmission.

There could be a further £100 of annual savings per customer due to lower investment cost.

Little sensitivity of the system benefits to the price of gas. Increasing the gas price three times reduces the system benefit per CHHS installation to about £80 per year, given that smart CHHS control requires slightly more gas than the default control.
 

The TRL of the project moved from 6 to 7

Lessons Learnt

Pre-installation

A number of factors were identified that are relevant when planning future installations of the Sime Compact Hybrid unit.

Customer Experience 

The market research and participant interviews carried out as part of the HyCompact project have illustrated that there is a strong interest in hybrid heating technologies, however many of the issues and concerns expressed by the participants during the project could have been mitigated through clear and concise communication in advance of the installations.

Key details that need to be clearly communicated and discussed in advance of a ‘sale’ include:

• Size and appearance of the Compact Hybrid boiler.
• Unit location and system design
• Installation process
• Sound levels
• Controls, operation and optimisation
• Running costs 

Design & Installation

Being a compact integrated hybrid unit, with no requirement to accommodate an external condenser unit, the unit can be installed in the place of a gas boiler. However the following factors were identified as requiring consideration before proceeding with an installation:

• The CHHS boiler weighs approximately 100kg, so needs to be mounted on a suitably strong wall;
• The CHHS boiler requires additional wall space to accommodate air ducts and it’s not possible to conceal the unit within a standard UK kitchen cupboard;
• Size and weight of the unit means that a second person and additional access and work space is required to safely complete the installation;
• A suitably qualified electrician is required to install / upgrade the power supply to the unit;
• Controls can be installed by a Gas Safe engineer with minimal training from the manufacturers.
• The current industry wide shortage of suitable skilled and experienced installation engineers is an issue. 

Post-installation

Noise and vibration:

One issue that was common to all installations was that of the sound output by the units, created by vibrations when the heat pump was operating. Although largely mitigated across the seven sites; the issue was found to be very subjective to the home, the participants occupancy and use patterns along with the overall context of the installation, all factors that will need to be taken into account when considering future installations.

Control experience:

The Passiv UK controls manage the heating of the home in a different way than may normally be expected with traditional gas boiler controls; this requires that the household understands the difference between space heating from the heat pump and the instant heat and hot water delivery from a traditional gas boiler. Education and communication are key to managing expectations, to help adapt behaviours and to avoid dissatisfaction.

Servicing and Maintenance.

Sime do not currently support an organised and trained network of service engineers. One of the findings of the consumer research carried out by Delta EE was that most consumers are inclined to trust well known and established brands; this lack of support network for CHHS could create a delay in the deployment of the technology.

Installation context

Analysis of field trial data and evidence from participants helped to develop guidance for the design and installation of the CHHS. This suggested that this particular CHHS will not always be a suitable option.

The following points were identified as potential improvements / extensions to the work completed on the HyCompact project     

• A programme of survey work would help gain an understanding of the “target market”, i.e. homes of the right size which have a suitable installation location for a boiler where the low-level noise is not an issue)
• A larger field trial with systematic deployment of compact hybrids in carefully selected suitable homes (criteria above) would have a more representative and robust indication of the system benefits (carbon savings etc).
• Understanding why the performance of one home in particular was so much better than the others, for example looking at detailed heat loss calculations for each home and radiator sizing.  Improved radiator sizing may also be the key towards making compact hybrids cost-effective at current prices, and this is also a cumulative retrofit improvement benefit for full heat pump systems.
• Extending Passiv’s capabilities to provide more accurate predictions for compact hybrid systems, enabling more detailed estimates of operation in different house types and different scenarios (such as time-of-use tariffs and multi-asset deployments with a battery and/or solar PV) and annual cost and carbon figures compared with the capital cost of deployment.