What does Electrified Heat actually mean?

Looking at the bigger picture, the climate is changing. To mitigate the impacts of this, it is apparent that we all need to reduce our demands on the planet and be more considerate to natural resources. Business as usual is not an option, but the solutions are not necessarily straightforward either.

Electrified heat is cited as a way forward, but what does that actually mean? The IET has produced the IET Guide to Implementing Electrified Heat in Domestic Properties to provide insight to the issues and guidance on the solutions from industry leaders.

We need to reduce carbon emissions, especially in buildings: electrical designs and installations can help with the right strategy. However, it is important to remember that it needs careful assessment and informed design choices before cables, equipment and controls are installed. Other considerations should include energy efficiency control measures and correctly assessing maximum demand and load diversity.

Lighting, especially in commercial and public buildings, adds to energy demands, however, the use of LED luminaires and deployment of automatic controls can alleviate that aspect. Increasing uptake of electric vehicles will add to energy consumption and may need load management, possibly coupled to smart metering. Small power loads often have relatively short term requirements with either directly monitored use or their own automated controls that limit energy consumption.

The largest persistent energy demand in buildings are space heating and water heating. There is a lot of discussion about the electrification of heat, including the deployment of heat pumps. So, what is the electrification of heat and what are the implications? What are the impacts on new building designs? What are the impacts on retrofit installations?

We have always had some forms of electrical powered heat. Point of use water heaters at sinks, back up electrodes for immersion tanks on gas heated water systems and electrical element storage space heaters run on overnight cheaper tariffs are all examples of legacy technologies that are still used. The inherent efficiency of these systems is typically less than 100 %.

Heat pump technology is hardly new and is an adaptation of refrigeration based technology. It harvests heat energy from a renewable source, for example the ground (GSHP) or air (ASHP), and either uses it immediately as space heating or stores it in a medium for later use as domestic hot water or space heating.

Refrigeration is the means to harvest the heat, but it is electricity that drives the system. There are benefits to this approach: for every unit (kWh) of electricity “invested” there can be a “return” of 3 kWh or more in heat energy. This efficiency is referred to as the ‘coefficient of performance’  (CoP).  This CoP varies throughout the year. For ASHP, in the summer months, a CoP of 4.5 is feasible, during the winter it will perhaps reduce to 2.2. The average over the whole year will typically be in the range of 2.8 to 3.0.

A word of caution though, simply swapping out an old gas or oil boiler for a heat pump system is not always advisable. There are a number of considerations and the IET Guide to Implementing Electrified Heat in Domestic Properties provides a number of insights into those areas:

• Fabric: heating is there to make us comfortable and replaces the heat loss in a building. Improving the fabric of the building reduces those losses irrespective of the fuel type used on a building. Better fabric means stable thermal comfort, less heating to maintain that comfort, less input power and therefore a lower electricity bill. IET Guide to Implementing Electrified Heat in Domestic Properties has some worked examples of heat loss calculations.
• Heat pump types: one size does not fit all. To provide a solid understanding of how to deploy heat pumps the IET Guide provides information on the refrigeration cycle, on the various components of a heat pump system, the types of heat pumps, refrigerants, operation conditions, correctly sizing the systems and associated efficiencies.
• Hot water: electrification of domestic hot water (DHW) is a proven technology. Using heat pumps for hot water production can also be very successful and offers significant energy efficiencies when compared to fossil fuel systems (gas or oil).
• Space heating: there are several types of direct electrically powered space heating. Heat pumps add to the available types of systems and the IET Guide describes the pros and cons of them all. On some systems zoning the heating will allow for specific areas to be tailored to suit different uses.
• Electrical supplies: direct electrified heat is an area that is fully understood. Implementation of heat pumps needs some additional thought to understand the implications of winter CoP and how that can affect the electrical installation’s maximum demand when there will be coincidental seasonal demands, such as increased use of lighting.

Constraints on electrical supplies are a risk but can be mitigated. Designs for new builds may have challenges, but can be resolved. Designs for retrofit installations may need additional thought, but there are solutions available in most cases.

The IET Guide provides insight into these issues and explanations on dealing with DNO applications and smart grids. Headline commentary on the integration of PVs, EVs and energy storage is also included, although there is separate IET guidance and Codes of Practice available for more in depth information in those areas.

• Business case: new technologies might be perceived as disruptive and there will be clients who need a business case to ensure the correct decisions are made, even for domestic installations. The IET Guide provides key insights on drivers for change, pros and cons, stakeholders, energy costs, capital costs, serving costs, carbon factors. There is guidance on simple financial evaluations and worked examples too.
• Future perspectives: the landscape for heating is changing. In large conurbations heat as a service is an option. The IET Guide provides some analysis of the future for electrified heat, how it may be applied and the implications that may have. Developments of multi-storey residential estates are already using central energy centres that, in turn, provide connections to heat interface units (HIU) in individual apartments. Heat pumps are now being used as the source for the energy centres in a number of new developments.

Electrified heat is here to stay and is set to be a major player in new installations of all shapes and sizes, either through communal systems or smaller individual installations. Fossil fuelled gas and oil boilers will be phased out following on from recent central government declarations.

Electrified heat has a role to play in retrofit too, provided the installation is correctly designed, sized adequately and installed where the heat pump can work effectively. The author has monitored his own retrofitted DHW ASHP for more than 6 years. The previous gas boiler required circa 6900 kWh of gas energy per annum to provide hot water. The DHW ASHP requires circa 1200 kWh per annum of electrical energy which provides around 3500 kWh of heat energy. Even with fluctuating energy prices that represents a cost saving and a significant saving on the equivalent carbon emissions too.

The IET Guide to Implementing Electrified Heat in Domestic Properties provides a holistic and practical overview of the requirements, implications and benefits of electrified heat.

https://shop.theiet.org/guide-to-implementing-electrified-heat-in-domestic-properties

Readers may also be interested in the IET’s new factfile entitled Decarbonising the built environment