by Dr Iain Staffell – Imperial College London
The cold weather in March not only affected the power system, Britain’s gas network was also stretched as demand outstripped supply.
On March 1st, National Grid forecast that the amount of gas in pipelines was going to fall below the normal operating range. This forced them to trigger the first ‘Gas Deficit Warning’ in eight years.
This helped push the spot price of gas to 11.2 p/kWh – compared to an annual average of just 1.5 p/kWh. The price increase brought more supplies of gas into the system, and persuaded gas power stations to reduce their output, to be replaced by cheaper coal. By March 2nd the warning was removed and the spot price of gas returned to normal over the next few days.
The shortage was partly due to unusually high demand for gas during the cold weather (see chart below). Five in six of Britain’s homes and offices are heated by gas1. On the coldest day (March 1st), daily gas demand spiked to 4,600 GWh, a level not seen since 2010. For a sense of scale, the extra gas demand due to the cold weather was comparable to the entire country’s electricity demand.
A further worry for the gas system was the historically low levels of gas held in storage. This was not helped by the cold weather coming unusually late into the heating season; gas in storage is likely to be at a greater level earlier in the winter months. Last year, Britain’s largest inter-seasonal gas storage site (Rough) reached the end of its economic life, and was deemed unprofitable. It discharged for the last time over winter, and was finally emptied by mid-January.
Daily demand for gas and electricity over the last four years. Non-daily metered gas demand is shown (excluding power stations and heavy industry), as a proxy for domestic heat demand.
The UK has historically worked with less gas storage than neighbouring countries, as domestic supplies from the North Sea provided a dependable source. This is being replaced by imports, including liquid natural gas (LNG) ships which provide flexibility in deliveries, at a price. France, Germany and the US typically hold 2–3 months of gas in storage. In contrast, Britain’s 64 TWh of storage could satisfy just 20 days of demand, but with the closure of Rough this has fallen to around 25 TWh, or just 8 days of storage.
The amount of stored gas is at its lowest since 2010 (see chart below). In the week surrounding the Beast from the East, 26.7 TWh of gas was consumed, 8.4 TWh of which came from storage (see the sharp dip at the start of March). In comparison, total electricity demand in that week was just 6 TWh.
The ability of the gas system to accommodate significant swings in energy demand over daily, weekly and seasonal timeframes is one of its major strengths. As coal continues to be phased out, gas becomes ever-more important for electricity generation, as well as heating. Maintaining this flexibility and the ability to cope with unusual weather is as critical as ever.
The amount of gas available as LNG and storage throughout the year. The shaded area shows the historic range, the two lines show the most recent years. For comparison, all of Britain’s pumped hydro storage facilities can hold 0.03 TWh of electricity.
1. DECC 2013
Authors: Dr Grant Wilson, Dr Iain Staffell