Hot water cylinders as a DSR solution for frequency response

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Published: 27th May 2020

Hot water cylinders as a DSR solution for frequency response

New records mean that the UK’s electricity system encounters new problems 

National Grid data shows that just 43% of 2019’s power generation came from fossil fuels – the cleanest year on recordThis year the UK’s power system went coal-free for 30 days over April and May  the longest period without coal on record, beating the previous record set in May 2019 when the country managed a fortnightOn 20th April 2020, the solar generation record was broken with peak generation reaching 9.68GW.  

This progress has been achieved thanks to the record amount of installed renewable energy capacity, year-on-year growth in renewables has seen the UK lauded as one of the most rapidly decarbonising power systems globally.  

The 30 day run without coal has also been partly enabled by an unprecedented (and unpredicted) reduction in energy demand of between 15 and 20% due to the ongoing coronavirus lockdownThis reduction coinciding with the ideal conditions for renewable generation led to renewables peaking at 60% of total generation in April.  

Whilst on the face of it, a reduction of demand and increasing renewable supply sounds ideal for the continued decarbonisation of the energy system, the conditions of the energy system in Spring 2020 have caused real challenges for the management of the electricity grid 

Renewables are intermittent and variable by nature – more or less so depending on the weather.  

These dynamic characteristics add to the technical challenge of balancing supply and demand – when these become unmatched there is a real risk that overproduction of electricity could lead to grid frequency rising outside of its safe thresholds (in the UK grid frequency must remain between 49.5hz and 50.5hz). If this happens, then National Grid must take immediate remedial action to ensure a full black-out doesn’t occur.  

There is some control that can be had over renewables to manage the oversupply – wind turbines and PV installations can systematically be turned off if necessary, although this can be expensive and costs are ultimately passed on to consumers through energy billsFurther, some decentralised assets are embedded’ in the system and operate outside of the national system, these can be challenging to instruct or monitor at all 

Demand Side Response (DSR) and hot water storage cylinders as a solution. 

The effective utilisation of DSR can reduce the requirements for remedial actions by the grid operator at the supply side, by compensating with increases in demand. DSR solutions have been in play for decades with Economy 7 perhaps the most famous example being introduced to homes in the 70s. Typically DSR has incentivised direct intervention from end-users through static/dual time-of-use pricing or peak load rebates.  

With an increasingly digitalised energy system, there is an opportunity to automate DSR activities with near-immediate response times – this offers an opportunity to see DSR solutions provide valuable grid services such as frequency response without the need for people to take an action themselvesTo this end, National Grid ESO’s firm frequency response service directly incentives energy consumers that are able to meet certain technical requirements to provide the frequency response for the grid at sub-10 or sub-30 second response times.  

Furthermore, coupling automated DSR with storage capacity can lead the way for demand-side response to have minimal impact on people’s conventional consumption patterns – which under normal circumstances are relatively predictable and inflexible – by simply storing any unused energy harvested via DSR for later in the day 

Through the USER Project, Levelise Limited in partnership with Baxi Heating are pioneering technology that demonstrates how domestic buildings can participate in the DSR markets through automated DSR combined with hot water storage cylinders. The technology on trial enables cylinders to provide DSR services by responding to price signals from the firm frequency response service and changes in wholesale electricity prices. When the grid requires balancing services the technology can flick on hot water cylinder’s electrical immersion heater to heat water for storage later in the day.   

The scale of the opportunity for using hot water storage assets to provide near-immediate frequency response is significant. Not only could it empower close to 10 million homes to participate more actively within the energy markets and secure themselves a revenue, but it also represents close to at least 100GWh latent storage availability that could be tapped into as a valuable resource for storing excess renewable power as useful heat, all whilst helping balance the electricity system. 


The technology being trialled is AI-led and simultaneously considers the demand profiles of individual homes – meaning that the response is only issued when a home is forecasted to require hot water. Thus the technology supports the optimisation of the energy system at the whole system level, whilst directly benefiting people at home by considering individual needs  

The challenges for the energy system that we have already seen in 2020 serves as a test run for what may be the norm in 10 years as renewable capacity continues to displace traditional fossil fuel generators. This will lead to more frequent events where supply and demand are mismatched, as well as an overall decline in grid inertia.  

Continued innovation of Demand Side Response technologies such as those being piloted by the USER Project is critical to ensuring the energy system has the necessary inbuilt flexibility that will be required to enable the energy transition and manage the daily challenges of a low-carbon power supply.  

The USER Project is part-funded by The Department for Business, Energy and Industrial Strategy’s (BEIS) Domestic DSR competition. The competition was launched in 2018, committing £9.78 million in funding over 3 years to support innovative applications for smart energy systems that help homes directly interact with supply-side conditions. The competition has included 20 feasibility studies (Phase 1) and 14 subsequent demonstration projects (Phase 2). 

The USER Project is being delivered via a consortium of 5 companies: LeveliseBaxi Heating, Ecuity Consulting, Energy Systems Catapult, Durham University. 

This blog was written by Alex Taylor, consultant at Ecuity.

For more information on the project, email us at:
BEIS funding for innovative smart energy systems
Phase 2 Project details