With increasing deployment of variable, non-synchronous generation and the closure of conventional dispatchable generation, the GB electricity system is becoming more inflexible. Additional sources of flexibility are required to help operate the system.
National Grid Electricity System Operator (ESO) is exploring new ways to procure additional flexibility, including exploring the potential for flexibility from the demand side. The Power Responsive programme, which brings together stakeholders from a range of UK sectors, identified potential for additional demand-side flexibility from the water sector.
Water systems are built with headroom to protect against rare weather events such as storms, floods and droughts, and it is this ‘system headroom’ which could be used to provide additional flexibility services. However, it is unclear how large these system-wide opportunities from the water sector are, where they are, how to access them and whether there is a sufficiently strong business case to justify the necessary investment in new technology and processes. The research hypothesis of this project is that providing demand side flexibility through controlling a whole water system is more cost-effective than focussing on a single asset or process.
Objectives
The objectives of this project are:
- to assess the technical potential for demand-side flexibility within a single waste water catchment area when operating all assets as part of a wider system
- to identify technical enhancements needed to operate individual assets as part of a wider system
- to assess the business case for providing flexibility services via this systemic method of operating assets within a waste water catchment area
- to support dissemination of any learning to water utilities, as well as other networks, to encourage deployment of this technology across GB if the project demonstrates technical and commercial feasibility
Learnings
Outcomes
There still remains uncertainty over the potential for flexibility provision from wastewater networks. Improved monitoring of wastewater assets, including flow to pumping stations and storage levels in wet wells would improve understanding of when assets could be flexible, and enhanced power monitoring on pumps would identify where opportunities exist, all of which bring wider business benefits.
This project looked to explore if controlling a wastewater catchment provided greater benefit than controlling single sites, and identified that it depends on the specific network configuration and storage available across the network to do this. The 5 sites investigated in Preston could be turned down as an aggregated set for 2-3 hours without negative impact to the network, and this report makes assumptions to aggregate this flexible capacity and availability across Great Britain, however hydraulic network models would need to be assessed across all network configurations across GB to state this is possible in all areas with certainty. This level of effort could not be justified for the limited benefit available.
Forecasting when the flexibility is available relies on confidence in rainfall forecasts. The forecast energy model demonstrated good results at predicting one hour ahead, with diminishing accuracy out to 12 hours and unsuitable accuracy as far as for day ahead. From an operational perspective, submitting availability for the day ahead with the ability to reforecast closer to real time could provide the best opportunity.
It is clear that installing technical enhancements to access flexibility markets is too expensive on smaller network sites, but also that greater certainty in market revenue is essential for installations even on larger sites.
The more static approach to responding to peak tariff avoidance, Capacity Market savings, and triad management show more current certainty of value, and are much cheaper to access, however changes to charging methodologies are removing some of these opportunities.
Although the need for increased demand side response is clearly set out within the ESO’s Future Energy Scenarios, the opportunities to participate are currently to be developed so it is not clear where the business case for such assets could sit. Further work on developing a holistic approach to flexibility markets is essential to increase I&C participation in DSR.
With increased certainty of value and optionality to reforecast in line with operational constraints, there is appetite to be flexible, but the primary purpose of the asset must be respected in order to protect the environment in the case of wastewater networks.
Lessons Learnt
Review of benefits case
The further modelling identified efficiencies can be made by bundling projects together and considering a ‘whole systems’ approach. Unfortunately these are not significant enough to reduce capital expenditure to a point where there is an acceptable return on investment. The benefit of controlling at one site with the knock on effect at others is highly dependent on the network configuration, which varies within a catchment, and so is not possible to state this with certainty.
Next steps
The project is now complete and learnings will be shared with other water companies.
Thoughts for further work consider that this project only focused on one area of the industrial water cycle, and wastewater networks account for 5% of total UU energy consumption. It is believed that there is further potential flexibility within other business areas not covered in this report. Further work for defining wider opportunities would be to investigate potential for flexibility on other operational activities. Water networks operate by a similar principle of pumping and storage, but there are much fewer sites, however each one with greater energy capacity and fewer environmental inputs, managed by a Water Production Planning team.
