Ashden Winners

Open Energi / A virtual power station

Area of work:

Impax Asset Management
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To keep electricity supply to the National Grid stable, gas and coal-powered stations are kept running below full power which is expensive, inefficient and increases carbon emissions.

Open Energi have created software which can automatically switch energy-hungry equipment on or off when required, without disrupting business and earns its client money from the National Grid. The overall energy use remains the same and it reduces CO2 emissions by 38,700 tonnes a year and removes a barrier to increasing renewable energy.

38,700 tonnes of CO2 emissions reduced annually.

41 clients with 382 sites.

60 MW of flexible demand.

"Open Energi has developed a truly innovative technology to provide a frequency response service, which is essential for the integration of more renewable energy into the grid."

Ashden judging panel


To keep the lights on, National Grid has to keep electricity demand and supply exactly in balance, and when faults occur a rapid response is needed – within two seconds! Traditionally this was provided by gas and coal power plants running below full power, so they can adjust output quickly, but this is inefficient, expensive and increases CO2 emissions. Open Energi has developed an alternative – cutting-edge software which can automatically switch energy-hungry equipment on or off when required, without disrupting business operations.

Large energy users like water companies identify which items of equipment are not time-sensitive in their operation and this equipment can then increase or decrease its consumption within agreed parameters to provide a rapid response service to National Grid.

Cathy McClay – Head of commercial operations for the National Grid. © Andrew Aitchison / Ashden


Open Energi has signed up 41 clients with 382 sites and 60 MW of flexible demand, enabling it to typically turn up by 12 MW and turn down by 5 MW – the exact capacity available varies over time. By reducing the need for fossil fuel power stations to run below full power, Open Energi is building a ‘virtual power plant’ and cutting CO2 emissions by an estimated 38,700 tonnes/year at the time of writing.

The best thing about being an Open Energi customer is that you really feel like you’re helping solve the bigger problem of energy demand. By controlling consumption instead of generation, you open the door for more renewable energy generation. You become an enabler of a more sustainable future.

Andy Pennick, Energy Manager, United Utilities


Open Energi was founded in 1999, and announced its first commercial Dynamic Demand customer in 2011. Dynamic Demand is aimed at commercial and industrial client sites with energy-intensive processes that are not time-sensitive, such as heating, cooling or water pumping. It monitors the grid frequency and asks the client’s equipment to reduce demand if the grid frequency is too low, and increase demand if it is too high. The overall energy use remains the same; it is simply used at a different time. National Grid pays for this service, known as Firm Frequency Response (FFR), and Open Energi shares the income with its clients.

Open Energi is currently the only demand-side business that has successfully developed the technical capability to operate in National Grid’s Dynamic FFR market, where responses to changes in grid frequency must be made automatically within two seconds. Because Dynamic Demand can respond so quickly, it is able to substitute for the spinning generators in fossil fuel power stations, enabling reductions in CO2 emissions and removing a barrier to increased renewable energy generation.

When the service was launched, the first customers were understandably wary about handing over partial control of their electrical equipment to a third party, but Open Energi worked closely with them to assess their equipment and demonstrate that their operations would be unaffected. It now has many well-known clients, including United Utilities, Sainsbury’s and Aggregate Industries, and has a total of 60 MW of electrical demand signed up.

Bolton Waterworks – aeration lanes.

What types of demand are flexible?

The first step for Open Energi when working with a new client is to identify which electrical equipment can be regarded as providing flexible demand. This requires a full understanding of the client’s processes and obligations. For example, freezers will have a maximum temperature that they must stay below, but no minimum temperature, while a waste water treatment plant has to maintain a minimum oxygen content in the waste water at some stages of the treatment.

The next step is to rule out any equipment that must run at specific times, must run continuously or does not use enough electricity for a Dynamic Demand installation to be economically viable. Processes that usually have sufficient flexibility and demand include air conditioning, space heating, industrial heating, commercial refrigeration, ventilation, water pumping and waste water treatment.

How Dynamic Demand works

Each installation is customised for the client, and is integrated into their control systems, so that it can take account of parameters that dictate whether the equipment can be turned up or down at any particular point in time. Specialist contractors are used for electrical and software work to ensure smooth operation, and a period of testing is carried out after installation to ensure the client is convinced that their business processes will not be adversely affected. The client also has a ‘cut-off switch’, to temporarily disable the system if required for operational reasons.

Dynamic Demand is fully automatic, requiring no intervention from the client. It monitors the national grid frequency, turning equipment down when the frequency drops below 50 Hz, and turning it up when it is above 50 Hz. The exact point at which equipment is turned up or down is controlled by Open Energi remotely and varies from site to site, to provide a smooth response as the frequency moves progressively away from 50 Hz.

Winning an Ashden Award is recognition that demand side flexibility is a vital part of our transition towards 100% renewable energy. Already it has provided many opportunities for us to share our story and increase our profile and it is helping to fund technology developments which will unlock flexibility from many more sources as the company scales.

David Hill, Open Energi

Open Energi works with clients to set limits on the operation of Dynamic Demand, such as the maximum duration of a frequency response event, the minimum time between events, and taking account of existing strategies to minimise costs, such as switching equipment off entirely during peak hours in the early evening. In practice, the electrical demand which can be turned up or down is less than the total demand signed up, due to clients’ restrictions and also because equipment that is already off can’t be turned down, and vice versa.

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