Space requirements, foundation, and fire safety: The physical preparation work

Once a company has established that an industrial BESS (battery energy storage system) makes sense, a specific question follows: what needs to be in place physically before the excavator and the modules arrive? A battery system of industrial scale is a fixed installation that occupies space, rests on a foundation, and must be placed with regard to fire risk and to the environment it stands in. A large part of that work sits before the installation itself, and it determines whether delivery of the system can proceed without delays.

This article describes the physical preparation work: the area and space on site, the foundation and subgrade, fire conditions and access, and the containment lining against groundwater contamination that forms part of our installations. The overall assessment of whether a site is suitable, and the basic physical principles of placement, are covered separately elsewhere in this guide, so the focus here is on what must be prepared on the ground, and on who carries out what.

The area and space on the site

The first point to clarify is how much space the system occupies, and whether that space is actually available on the site. There is no single public standard size for a BESS, so the area must be fixed from the specific configuration and the placement requirements the project documents. It is a project assessment, not a fixed norm, which is also the basis of the guide's article on the installation itself.

As an illustrative starting point, the foundation for four units typically measures around 5 to 6 metres in length, with roughly one metre more per additional unit. That is an indicative figure to give a sense, not a fixed dimension, because the actual size depends on the number of modules, how they are placed, and the access and distance conditions on the individual site. Beside the system itself there must be space for cable routing, for the necessary electrical infrastructure, and for professionals and the emergency services to reach it. The space requirement is therefore not only the system's footprint, but also the area that operations and safety require around it.

Foundation and subgrade

An industrial battery system is heavy and must stand stably throughout its lifetime, and for that reason it rests on a cast foundation. The foundation is prepared by a contractor, typically as one of the first physical works on the site, so that it is cured and ready when the modules arrive.

Requirements for the construction itself follow the ordinary rules for permanent buildings. The Danish Building Regulations (Bygningsreglementet) set a minimum level for the properties of the construction, and a fixed installation of this type is in practice founded to frost-free depth on load-bearing ground, so that damage does not arise from movement in the soil. How deep the foundation must go, and how the subgrade must be prepared, is a geotechnical assessment that depends on the soil conditions on the particular site. Soft or moist soil conditions can mean extra preparatory work, and that is one of the reasons the subgrade is assessed early, while it can still be accounted for in the schedule. The foundation itself is therefore not a formality, but a piece of civil works that must be finished before the system can be installed.

Fire conditions and access

Lithium-ion batteries contain large amounts of energy, and in the event of a fault a so-called thermal runaway can occur, where a cell develops heat that spreads and can lead to fire and heavy smoke. That is the background for treating a larger BESS as a fire risk that must be assessed case by case, which the Danish Emergency Management Agency (Beredskabsstyrelsen) describes in its guidance on fire protection of larger stores of lithium-ion batteries and BESS.

In practice that means the municipal emergency service can set fire-related conditions for a larger system, and that distances, access conditions, and placement are assessed case by case based on, among other things, battery type, capacity, and whether the system stands outdoors, under cover, or in a building. There is no single fixed distance in metres to residential buildings that applies to all BESS installations. The distance to neighbours and buildings is site-specific, typically in the order of 30 to 40 metres, but the precise distance is fixed in dialogue with the authorities and depends on the specific placement. Access conditions form part of the same assessment, because the emergency service must be able to reach the system. Fire conditions are therefore something clarified before the system is built, not something adapted afterwards.

Containment lining against groundwater contamination

One of the factors that matters most for companies with environmental requirements, for neighbours close to residential areas, and for installations in groundwater-sensitive areas is what happens to liquid if the worst occurs. Our installations are based on a municipally approved solution dimensioned to prevent liquid from a fire (including extinguishing water from the fire service) from carrying battery chemistry into the groundwater. The requirements stem from an approval under particularly strict groundwater protection and typically go beyond a standard BESS foundation. It is a physical barrier and an approved design, not a green label.

The rationale behind such a barrier is well known from environmental regulation of industrial companies. Experience from soil and groundwater contamination is that preventive physical measures could have avoided or substantially reduced contamination, and that protection should be designed based on, among other things, the installation's location relative to groundwater interests and neighbouring areas. A sealed containment lining under an installation with chemical content follows exactly that principle: it collects the liquid that could otherwise seep into the ground.

Placement relative to groundwater is regulated separately. In areas with special drinking water interests, in abstraction catchments, and in borehole-near protection zones, municipalities must in their planning keep areas free of new installations that may pose a risk of groundwater contamination, and it is the municipality's task to assess that risk case by case. If a placement requires measures to avert the risk, it triggers a groundwater statement in which the municipality must account for the necessary mitigation measures. An approved containment lining is therefore not marketing, but precisely the type of specific measure that can make a placement defensible in a sensitive area. The same dialogue with the municipality on construction, fire, and groundwater is described from the authorities' angle in its own track in the guide.

Who orders and carries out what

The physical preparatory work involves several parties, and a recurring source of confusion is who orders and carries out what. The roles can be divided into three.

• The contractor handles the heavy civil works on the site: excavation, foundation, preparation of the area, and the physical containment lining under and around the system.
• The electrical installer handles the electrical side. Work on fixed electrical installations may only be carried out by an authorised electrical installation company, and that covers switchboard work, cables, and the local grid connection, where a new switchboard often has to be established.
• We at ZynexGroup handle project management: hardware, software, coordination of contractor and electrical installer, and dialogue with the grid company and the municipality, including applications for the relevant fire and building permits.

The company itself contributes requirements and preferences, input on placement, and access to the site, and must ensure that the system can be built legally at the address. A central part of the value in a turnkey process is that the company does not have to find and manage the individual links itself. The grid connection itself is a separate track: our standard offer typically assumes a connection of at least 400A, in a 400V three-phase system corresponding to a power of approximately 277 kW, and the technical clarification of that is covered in more detail in the guide's article on grid connection.

ZynexGroup's approach to site assessment

We arrange the physical preparatory work so the sequence stays intact: foundation and containment lining are prepared by the contractor, while the electrical installer makes the electrical side ready, and everything is in place when the modules arrive for installation. Our role is to coordinate the professionals who carry out the work, and to lead the dialogue with the authorities, so that fire and groundwater conditions are clarified before the system is built.

We treat groundwater protection as a real part of the physical design, not as an add-on. The containment lining is a physical barrier that has been approved in practice under strict groundwater requirements, and it forms part of the solution we prepare on the site. We cannot promise a particular outcome of a fire, and we do not name a particular municipality, but we can explain what the barrier is for, and why it matters for a company that stands in a groundwater-sensitive area or close to neighbours. Throughout the process, the company has one fixed contact person with us.

Limitations and preconditions

The physical preparatory work can encounter conditions that cannot be met. Soil conditions on the site can make the foundation more extensive, and the space the system requires with distances and access is not always available where the company wants it. Fire conditions are decided in a case-by-case assessment that we prepare but do not ourselves decide, and placement in a groundwater-sensitive area can impose requirements that affect both design and schedule.

The containment lining against groundwater contamination does not remove the risk of a fire, but is a physical measure dimensioned to hold liquid back if a fire occurs. If the system is also to function as backup power or secure critical loads, that is a separate decision with its own technical design, described from a production continuity perspective elsewhere in our material. In the physical preparation work, the point is to surface those conditions early, while they can still be accounted for in the planning.

Overall perspective

The physical preparation work is what allows a delivery to proceed smoothly. The area must be available, not only for the system, but also for cables, access, and safety. The foundation must be cast and cured on load-bearing ground before the modules arrive. Fire conditions must be assessed case by case with the emergency service, and in a groundwater-sensitive area an approved containment lining must be in place, so that a possible fire does not carry battery chemistry into the groundwater. A company that knows those conditions early can prepare the site while the rest of the process runs, and avoid the physical work becoming the bottleneck.

Have the potential for your facility assessed

If you are considering an industrial BESS, the physical preparatory work is part of the overall assessment: the space you have available, your soil conditions, the distance to neighbours and buildings, and whether the site lies in a groundwater-sensitive area. We use that type of information together with your grid connection and consumption profile for an initial assessment of whether there is a match, and for a data-based dialogue about the next steps. You are welcome to contact us here.