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Environmental impact of backup generators

A backup power source for a data centre is essential. On-site emergency back-up power generation provides a short-term solution to cover the grid during brief fluctuations or prolonged outages.Ìý

Typically, backup generators will be fuelled by diesel stored on-site and need to be tested regularly throughout the year. And when they are, they emit potentially harmful pollutants into the air.ÌýThe installation of a backup generator therefore triggers the need for an air quality impact assessment to accompany a planning application, or environmental permit.Ìý

Technical Director, Fiona Prismall, talks about the importance of planning ahead for a data centre emergency, and the role a robustÌýAir Quality Management Plan (AQMP) will play.

Why is there a need for Air Quality Management Plans?

Regulators require operators to prepare an Air Quality Management Plan outlining the response measures they will take during a grid failure. The response measures in the plan will need to be tailored to reflect the likely air quality impact for surrounding land users. The plan must also include details of the local conditions during a grid failure that might influence the response required. For example—weather conditions or time of day.

The assessment results provide valuable information to help estimate the weather conditions that are most likely to affect certain nearby land users. Pollutant concentrations at nearby locations are predicted using an atmospheric dispersion model for five years of hourly meteorological measurements (over 43,800 hours).

From that, operators can be advised of the likely wind direction that may lead to a potentially significant air quality effect for each of the nearby land users. This can be used within the Air Quality Management Plan to allow nearby land users to take appropriate action which might include:

• Move and/or stay indoors
• Close windows and doors
• Reduce physical exertions as far as practicable
• For a prolonged emergency, relocate

What if there's an emergency?

The short-term impacts are usually much greater during an emergency as all the generators may need to be deployed simultaneously, with testing and maintenance carried out on only one generator at a time.

However, assessing the air quality when the generators are used in an emergency is more difficult, as it's unknown when this might happen, or for how long backup power will be needed.

What can be done is assessing the probability of a significant effect by predicting pollutant concentrations at nearby locations for a wide range of weather conditions. That gives a good indication of the types of weather conditions that could affect land users surrounding any particular data centre. This will allow the operator to take focused action to warn the community at the most critical times.

Why plan ahead?

Early consideration of the likely air quality impacts allows appropriate mitigation to be built into the design of a data centre. This can be a key factor in a successful planning application or an environmental permit.

If permission is granted, the predictions in the assessment, undertaken to accompany the application, can provide valuable information to assist in the development of an AQMP. Its content will be informed by the results of the air quality assessment.

How we can help

Working in partnership, we can support you right from project inception; from clarifying regulations, defining targets and steering you through the planning process, to identifying and mitigating environmental impacts such as air quality, addressing biodiversity net gain, through to cost effective and pragmatic advice for design and operation.