There has been a large increase in gas-to-grid biogas plants and many experts regard this as a big opportunity for farmers.
How is the gas network structured?
Gas is transported around the UK via a pipe network of varying sizes and pressures. The 4,000-mile National Transmission System (NTS) is the main supply route from gas terminals, operating at the highest pressure up to 85 bar.
From this most consumers receive supplies via much lower-pressure steel pipes connected to the NTS and operated by one of eight distribution networks.
Who manages the grid?
National Grid owns and operates the NTS. It also owns four of the eight regional distributors, covering the South East, London, East and West Midlands, and North West England.
The other four distribution network operators are Southern Gas Networks, Northern Gas Networks, Wales & West Utilities, and Scotland Gas Networks.
Bord Gais is responsible for Ireland.
How does the process work for new connections?
Commercial arrangements vary across network operators but the principles are broadly similar, says National Grid stakeholder implementation manager (R&E) Nicky Kirk, who outlines the company’s process for new gas grid connections:
- Initial inquiry: Anyone looking to connect a biomethane plant to the gas grid should first contact their local network operator outlining the project, including its location and amount of biogas to be supplied (eg. cubic metres/hr). National Grid aims to respond within 15 days (maximum), although it often takes less than this to decide in principle whether the proposed supply can be accepted, or whether capacity constraints need to be imposed. This is not a formal connection offer.
- Detailed analysis: Next is a feasibility study examining the project in detail, focusing on areas such as pipeline routes, connection points, potential engineering issues, pipe capacity and supply profiling through the year. Studies typically cost about £700 (paid upfront) and take around 30 working days. Straightforward projects – such as a short pipe from mains to AD plant with no capacity issues – may not need detailed analysis prior to a connection offer.
- Connection offer: Once details are agreed a connection offer is issued. This commits the network operator to accept the requested gas flow by a set date. A grid offer is needed for Renewable Heat Incentive applications. There is no cost for the connection offer, but it must be accepted within 45 calendar days and to avoid speculative developers “sitting on” spare capacity evidence of planning permission must be supplied within two months of acceptance, otherwise the offer is terminated. Projects are also expected to be operational within 12 months.
- Payment: Although AD developers can choose between employing contractors or the network operator to carry out connection work, network operators retain control of some technical elements, notably gas monitoring and safety equipment (eg. remote operating valves to shut off supplies in the event of a problem in the grid entry unit. Costs vary considerably depending on the size and complexity of the project and must be paid upfront.
- Network Entry Agreement (NEA): Once the AD plant is constructed and commissioned, the NEA comes into play, setting obligations for daily plant operation and sampling to ensure gas meets strict quality and safety criteria.
How long does it all take?
Total connection time depends on a large number of factors, including pipe size, paperwork, engineering assessments and workload of the grid operating company, says Les Gornall process consultant at Capita.
Experience suggests timescales range from three months to two years, with an average of six to nine months.
Is gas-to-grid for me?
Connecting to the gas grid is far from straightforward and can incur significant costs.
Dr Gornall says low pressure lines are generally easier to connect to as there are more of them and cost is lower, but there may be capacity restrictions.
Cleaning gas to grid-quality standards is expensive, requiring projects to be scaled accordingly and in many cases feedstock availability becomes the limiting factor, he continues.
“During the design of a typical gas-to-grid system we start with the feedstock and the capacity of the proposed gas line connection and fill in the engineering black box between these two constraints.
Proximity to pipelines is another consideration.
Pipelines are efficient to operate, so gas can be transported up to several kilometres to the grid connection point, but installation is expensive, he says.
“It helps if distances are kept below 1km and trenching is done on your own land.”
Are there the same capacity issues as electricity?
Mrs Kirk says there are many opportunities for new gas grid connections and no capacity issues.
However, much depends on the local pipeline and gas demand, so it may be easier to connect in more densely populated or industrialised areas where demand is higher than remote rural areas.
Low pressure pipes feed small areas with steady gas consumption patterns so may have limited capacity, adds Dr Gornall.
Higher-pressure lines are more likely to be able to take a continuous flow (typically 500-1000cu m/hr) of grid-quality biomethane, but are more costly to connect into, he says.