Heat pumps alone are no magic bullets for schools

Rob Smelt
Rob Smelt of BReng

Rob Smelt, of low carbon consultancy BREng, discusses the complexity of sustainability requirements in education establishments and why each will need a different approach.

The scale of energy consumption across the education sector is significant. Total annual energy consumption by education buildings is estimated to be a staggering 11,378 million kWh of energy, equivalent to 25% of total public sector energy use.

The national education estate amounts to a substantial and diverse network of multi-use buildings, with complex HVAC requirements.

There are 32,226 schools in the UK, including around 4,000 secondary schools, 142 universities (in themselves effectively small towns) and around 400 further education colleges. The requirement to decarbonise school buildings poses a major challenge for the sector and will require every establishment to come up with a plan to achieve net zero carbon emissions within a defined timetable.

The national UK target of 2050 mandated in law is somewhat misleading, as some local authorities have adopted much faster net zero deadlines for public buildings in their areas. For example, major cities such as London, Birmingham and Bristol have set a target to be net zero by 2030 while Manchester has a target of 2038. 

In practice, therefore, education estate managers should be putting plans in place now to map out their route to net zero. Unfortunately, the diversity of school building types, usage patterns and existing energy systems make it impossible to apply a single template to deliver net zero. No single model could possibly cover the complex reality on the ground.

It requires a school-by-school approach. This starts with a detailed survey of existing HVAC infrastructure, taking into account the specifics of building fabric, insulation, glazing, orientation, design and lay-out – down to heating provision and occupancy levels of individual spaces at the classroom level.

‘Fundamental efficiency’

Heat pumps have been held up as a major technology solution in the effort to decarbonise heating, and rightly so. From a thermodynamic perspective, the fundamental efficiency of heat pumps is impossible to ignore.

“Unfortunately, the diversity of school building types, usage patterns and existing energy systems make it impossible to apply a single template to deliver net zero.”

Their ability to harvest low grade heat energy from the environment and upgrade it into a useful form to heat and cool buildings gives them a big advantage over alternatives.

While the most efficient forms of gas heating approach Coefficients of Performance (COPs) of less than one, modern heat pumps can achieve COPs many times this. As a result, heat pumps can generate several times more energy than they consume, far outstripping rival approaches.

This, coupled with the fact that they are proven technology, sets heat pumps apart among competing low carbon solutions, and means they will have a huge role to play in helping schools on the journey to net zero.

As well as helping to reduce carbon emissions for individual buildings, heat pumps have an important part to play in reducing emissions through their use in distributed heat networks.

This is particularly relevant for larger education estates, such as universities and colleges, where the combined heating requirements are greater and economies of scale deliver the highest savings.

In terms of public buildings, schools are unusual in being occupied for only part of the year. In term time, usage is very intense, with high occupancy density.

During holidays, occupancy falls dramatically, in many cases to zero. This presents schools with both challenges and opportunities for achieving net zero carbon.

Mix of solutions

High occupancy and intense usage during term time requires suitably-powered HVAC systems to cater for heating, cooling and ventilation requirements.

Adequate heating capacity is particularly important to ensure comfortable conditions at the start of the day. However, the high- density occupancy, particularly in classrooms and high-use corridors, means heating demand can fall rapidly as a result of the thermal contribution of pupils to the space.

This requires careful control of individual rooms to ensure the natural heat gain that occurs throughout the day in classrooms is taken account of, and heating inputs managed accordingly.

As efficient as heat pumps are, the reality is that they are not sufficient on their own to deliver Net Zero for most schools. They must be used in combination with other technologies.

Having carried out detailed HVAC and energy surveys of scores of schools, for the reasons outlined above, it is clear that the precise solution will be different in almost every case. It is likely to involve a mix of heat pumps, solar PV, LED lighting, upgraded heat emitters, insulation and high efficiency ventilation.

Additional source of energy

Energy use in the average school
Energy Use in the average school

Use of photovoltaic panels is particularly attractive in combination with heat pumps. Firstly, they provide an additional source of renewable energy to supplement that generated by heat pumps, helping to further reduce use of primary high-carbon electricity.

Secondly, as schools are not occupied for significant periods of time, particularly during the summer when solar energy is greatest, the surplus power produced can be returned to the grid to offset primary electricity used when the school is occupied.

“With 30,000 plus schools requiring decarbonisation, this is going to require a huge national effort.”

Thirdly, PV systems contribute helpful additional electrical power, which can be valuable for schools with limited power headroom, stretched by the higher power demand from installing heat pumps. This may help overcome the need to invest in upgrading power supplies, which can be a significant additional capital cost.

Gains through lighting

Lighting is another area where worthwhile gains can be made. Lighting represents around 8% of schools’ energy use, and 20% of their energy costs. Upgrading to modern LED lighting reduces electricity use by around 80%, compared with traditional technology, contributing a useful saving in the overall energy budget.

Heat pumps, in combination with PV systems and LED lighting, can deliver significant reductions in school carbon emissions. To fully optimise buildings, however, it often requires fine tuning HVAC systems with upgraded heat emitters, improved insulation and the use of modern monitoring and control systems.

While this is the main palette of technology options, it is important to stress that there isn’t a single magic bullet to deliver net zero.

Schools are complex estates, with diverse designs, legacy technologies and usage patterns.

This requires each site to be approached afresh, and the challenges and opportunities for achieving net zero assessed with an open mind in the light of the specifics, in each case.

Once a solution has been designed, installed and commissioned, the process doesn’t stop there. Experience shows that there are often significant additional gains that can be made by optimising the system in the light of how it operates in practice.

Fine tuning

Following the completion of a number of school decarbonisation projects over the past couple of years, schools are now working with consultants on fine-tuning systems to further reduce energy bills, cut carbon, and ensure pupils and staff benefit from the most comfortable and productive environment possible.

With 30,000 plus schools requiring decarbonisation, this is going to require a huge national effort. When considered alongside the wider challenge of decarbonising all public and private sector buildings, it is a truly epic undertaking.

The key is starting now and making use of the valuable lessons learned by the early adopters pioneering on the net zero frontier.

Learning by example

BREng has identified key lessons from recent pioneering school projects, to help education estate managers plan their path to net zero, the findings of it recently presented in a webinar entitled ‘Meeting Heat Demand in Schools’, part of a series on Decarbonising Education Buildings organised by elemental.

The key findings drew on BREng’s experience with decarbonisation projects in schools and academies, funded by the UK government’s Public Sector Decarbonisation Scheme (PSDS) and Condition Improvement Fund (CIF).

One example is a phased approach at Kepier School in North East England, which installed seven new gas boilers four years ago. Project partners BReng Hull, CIAT UK, consultant AA Projects, installer Quora Group and equipment supplier Cool Designs, helped develop a long-term decarbonisation plan for the school, with funding under the Condition Improvement Fund (CIF).

The project sought to upgrade heat-emitting systems, so the move to low-carbon heat pumps could be made seamlessly when the timcame to replace end-of-life gas-boilers.

The project included removal of conventional radiators and replacement with 31 CIAT COADIS and seven MajorLine FCUs.

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