With at least 73 GW data centre projects in the connection pipeline, the Labour government moved earlier this year to consult on proposals to curtail speculators snapping up spots in the connection queue.
But buried in the consultation document is also a proposal for embedding greater “demand flexibility” into data centre grid connection agreements.
Problem
Heatwaves are one of the triggers for electricity grid stress. Jon Saltmarsh, chief technology officer at Energy Systems Catapult told The Ecologist: “Heat affects all types of generation – it’s not specifically a renewables problem.
“Higher external temperatures result in gas generation thermal plants operating less efficiently while transformers and transmission networks have to be derated at higher temperatures.”
This makes balancing supply and demand for electricity very difficult, particularly as demand surges from consumers trying to keep cool.
The UK grid operator NESO can already pay large industrial users, including data centres, to switch off the grid and use their back-up generators through existing policies such as the Balancing Mechanism and Flexibility Services.
Saltmarsh added: “Much of the flexibility provided by industry comes from back-up diesel generation. For short periods of time, the carbon emissions are very limited. It only becomes a problem when used regularly.”
Rules
A source at the Department for Energy Security and Net Zero (DESNZ) said: “Data centres will not run from diesel powered generation at a significant scale when demand limitations are in place.
“Environmental permit requirements place limits on the operation of emergency generators, meaning they are not expected to provide a large-scale solution to data centre flexibility.”
In the US, environmental campaigners say the authorities have been trying for years to make it easier for operators to rely on data centre diesel generators to take the strain off the overloaded grid.
In 2023, Piedmont Environmental Council in Virginia warned that the local Department of Environmental Quality was trying to push through changes to strict rules about when data centres can run on diesel generators.
Slammed
As temperatures climbed to record levels across the Eastern states of the US in July this year, residents living near massive data centre clusters saw black smoke billowing from the facilities’ banks of diesel back-up generators.
Two punishing heatwaves that month prompted PJM Interconnection (PJM), the electricity grid operator serving 14 states across the region, to ask “large load” customers, including data centres, to switch over from the grid to their own power sources in order to avoid blackouts.
According to data released by PJM for 3 to 5 July and 14 to 17 July, the operator relied on generators running for 1,799 hours beyond the limits set down in their environmental permits, providing 9 GW of relief for the overloaded grid.
Environmental campaigners representing residents living in areas dominated by the region’s data centre clusters slammed the decision, which was authorised by the US Secretary of State for Energy.
See full article at theecologist.org
And how about availability of diesel:
Note also that European stress has migrated from road fuel into refined products — diesel is up roughly 40% since mid-June, with about a quarter of Russian refining capacity lost to strikes and Saudi Arabia’s Jazan refinery shut since 27 July. Forecourt availability, which is what this page measures, remains the least stressed part of the European picture.
In today’s market, EN590 diesel supply is shaped by more than refinery production capacity. Scheduled maintenance, domestic demand, export priorities, logistics constraints, and contractual obligations all affect how refineries allocate production. Consequently, buyers involved in diesel fuel procurement, bulk fuel allocation, or long-term supply agreements must understand how allocation decisions influence cargo availability before entering negotiations.
This article explains how refinery allocation works, why it matters to international buyers and suppliers, and how procurement strategies can be adapted to changing refinery operations while reducing commercial and logistical risk.
Industry Overview: Understanding Refinery Allocation EN590
Refinery Allocation Within the Petroleum Trading System
Refinery allocation is the process through which a refinery distributes its available production among contracted customers, domestic markets, export programs, and strategic inventories. Although production planning begins months before physical delivery, actual allocations are continually adjusted in response to operational performance and market conditions.
For EN590 diesel fuel, allocation decisions typically follow refinery production forecasts, contractual commitments, maintenance schedules, and export economics. A refinery with sufficient production capacity may still reduce export allocations if domestic consumption increases or if planned maintenance temporarily lowers output.
Within international petroleum trading, allocation serves as a mechanism for balancing supply with contractual obligations. Large integrated refiners often prioritize long-term customers before making additional cargoes available to traders or spot buyers. As a result, allocation influences not only physical supply but also procurement timing and commercial negotiations.
Refinery allocation also affects petroleum logistics, as export terminals, storage operators, vessel scheduling, and inspection providers coordinate around confirmed production volumes. Therefore, allocation decisions extend well beyond refinery operations and influence every stage of the downstream supply chain.
Diesel generators for nuclear power station backup;
Russian-held Zaporizhzhia nuclear plant loses external power supply
By Reuters
August 20, 20267:26 AM GMT+1Updated August 20, 2026
MOSCOW, Aug 20 (Reuters) – The Russian-controlled Zaporizhzhia nuclear power plant in Ukraine has switched to emergency diesel generators after damage to a high-voltage line caused the facility to lose external power, the plant management said on Thursday.
“Plant personnel are monitoring the equipment’s operating parameters. All necessary measures to maintain the safe condition of the power units are being taken in full,” the Moscow-installed management said, adding that radiation levels were normal.
The plant, Europe’s largest with six reactors, produces no electricity but needs power supplied by two external links to keep nuclear fuel cool.
Russia seized the plant in the first weeks of the war that began in 2022, and both Moscow and Kyiv have since regularly accused the other of military action that compromises nuclear safety.
Reporting by Reuters; Writing by Lucy Papachristou; Editing by Kirsten Donovan
And
The Zaporizhia Nuclear Power Plant (NPP) has lost external power supply again. Backup diesel generators were used to meet the station’s own needs. This was announced on August 20 by the ZAES press service.
The 330 kV Ferroalloy-1 high-voltage power transmission line, which provided external power to the NPP, shut down automatically due to damage. After the loss of external power supply, the power units of the station were regularly switched to power from backup diesel generators.
“The radiation background at the site of the Zaporizhia NPP and in the observation area is within the natural values and does not exceed the established norms,” the Telegram channel said.
The personnel of the NPP monitors the parameters of the equipment and takes all necessary measures to maintain the safe condition of the power units. The situation at the Zaporizhia NPP is under constant control of the plant’s specialists
Attack marks first time military action has forced a fully operating nuclear power plant to rely on backup generators
Tue 19 May 2026 15.49 BSTShare
A drone strike that cut off external power to a nuclear reactor in the United Arab Emirates this week has revived concerns over the safety of nuclear plants during wartime.
Reactor no 3 at the Barakah nuclear plant lost vital off-site power for about 24 hours after the attack on Sunday, forcing it to rely on emergency diesel generators.
The UAE’s defence ministry said on Tuesday that three drones targeting the plant had originated from Iraqi territory, suggesting a pro-Iranian proxy group was most likely to have been behind the strike.
Two were intercepted, but one got through, causing a fire near a four-reactor plant that supplies the UAE with a quarter of its electricity.
The UAE said the strike hit an electrical generator “outside the inner perimeter”, raising fears it could have hit the switch yard which lies just beyond a wall around the site’s reactors.
The impact of heatwaves on nuclear power generation is welldocumented, with a plethora of headlines often accompanying record temperatures in nations that rely on the technology.
For example, around 70% of electricity is generated by nuclear power in France, leaving it vulnerable to the impacts of heatwaves.
During the July 2026 heatwave, three of France’s 57 nuclear reactors had to shut down. Generation was reduced at another seven, causing an almost 9% dip in power production.
(This is a well-known phenomenon – France has seen reductions in nuclear generation due to heatwaves in 2003, 2006, 2015, 2018, 2019, 2022 and 2025.)
Retired, living in the Scottish Borders after living most of my life in cities in England. I can now indulge my interest in all aspects of living close to nature in a wild landscape. I live on what was once the Iapetus Ocean which took millions of years to travel from the Southern Hemisphere to here in the Northern Hemisphere. That set me thinking and questioning and seeking answers.
In 1998 I co-wrote Millennium Countdown (US)/ A Business Guide to the Year 2000 (UK) see https://www.abebooks.co.uk/products/isbn/9780749427917
borderslynn 