Feature: Electric/gas hybrid heating offers major demand-side resource

London (Platts)--20 Apr 2018 755 am EDT/1155 GMT

Demand side response (DSR) may spread to residential households if a new hybrid heating system catches on. Interim results published in April from the Freedom Project in the UK, a pound5.2m ($7.3 million) innovation project designed to trial hybrid heating systems, suggests automated switching between gas and electricity may deliver flexible DSR in a domestic setting.

  • Electric/gas hybrid heating has heat decarbonization potential
  • Taps large residential DSR resource
  • UK energy system over-reliant on gas

At present, DSR is largely restricted to large electricity consumers, such as industrial users, which have interruptible contracts. An extension of DSR into residential homes could massively extend the DSR resource, potentially reducing the need for investment in additional generating capacity and grid reinforcement.

The UK's residential sector accounts for about 100 TWh/year of electricity, just under a third of the total, while gas-fired generation provided 42.4% of electricity generated in the UK in 2016, according to government statistics.

The system combines efficient gas boilers with external air source heat pumps, allowing automated switching between gas and power loads to meet consumer demand for heat. The flexible approach is designed to allow consumers to participate in DSR programs.

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During 2017, UK company PassivSystems installed 75 hybrid heating systems as part of the Freedom Project in private and social housing in Bridgend, South Wales.

The air source heat pump introduced electrified heating to homes, but is used only when electricity prices are low, for example, when there is a lot of wind and/or solar generation on the system, providing some decarbonisation of heat provision.

At times of peak electricity demand, the system switches to gas. The ability to switch could allow residential consumers to participate in DSR with UK TSO National Grid paying aggregators to reduce demand, which would enable grid balancing without the need to generate more power to meet peak loads.

According to PassiveSystems, hybrid systems in domestic settings will allow better management of grid constraints and reduce investment in network reinforcement, providing overall system benefits and savings.

However, a problem common to such innovations is that the benefits are rarely aligned with those that bear the cost.

Consumers, generally reluctant to invest in high capital cost energy systems unless the payback is relatively short and certain, would in this case need to invest in two heating systems.

As the air source heat pump is external, it would be a relatively undisruptive form of retrofit.

A further problem at a system level is whether electricity to gas is a sensible switch to make in the UK setting. The UK is heavily dependent on gas to provide heat.

However, with new nuclear capacity still uncertain and coal plants being phased out, the electricity system is becoming increasingly dependent on gas for power generation.

During the harsh 'Beast from the East' winter weather of late February, demand for heat resulted in a shortage of gas for power generation. According to the UK's Department for Business, Energy and Industrial Strategy, space and water heating account for about 80% of final energy consumption in the residential sector.

The majority of this energy is provided by gas, "resulting in gas consumption in the domestic sector being the most responsive to temperature variations."

Colin Calder, PassivSystems' CEO, said "homes equipped with hybrid heating can play a major part in decarbonizing heat, while providing the flexibility we need to balance the electricity grid Hybrid heating systems can move as much demand to gas as they like - they have complete load flexibility."

The Freedom Project is funded through the Network Innovation Allowance by Western Power Distribution, the electricity distribution network operator and Wales & West Utilities, the gas distribution network operator.

--Ross McCracken,
--Edited by Jonathan Fox,

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