Under the sun: Understanding risk in solar energy

INTRODUCTION

Solar energy is one of the most established and widely deployed renewable energy technologies. It plays a central role in the transition to net zero by converting sunlight into electricity or heat, supporting applications ranging from domestic rooftops and commercial buildings through to large utility-scale solar farms. Deployment continues to grow, and projects are becoming larger, more complex and more frequently combined with other technologies [1], [3].

From the outside, solar projects can appear straightforward. There is no fuel supply, no combustion during normal operation, and little that visibly moves. However, the apparent simplicity can conceal important safety considerations. Solar assets generate electricity whenever there is sufficient light, which means parts of a system may remain live during daylight even when the wider electrical installation has been isolated. They also rely on electrical equipment, cabling, structures, drainage, access routes, and maintenance arrangements working together reliably over an asset life measured in decades [2], [6].

Solar is also a broader term than it first appears. A rooftop PV array, a ground mounted solar farm, a floating installation, an agrivoltaic scheme, a solar thermal system, and a concentrated solar power plant all use sunlight, but they do not work in the same way, and they do not share the same hazard profile. Where solar is co-located with battery energy storage, a further and quite distinct set of risks is introduced. Individually, these hazards are well understood; the challenge lies in recognising which apply to a given project and managing them together across the full lifecycle [11].

This article explores what solar energy is, how different solar technologies convert sunlight into useful energy, the hazards commonly associated with solar projects, and how good design and lifecycle risk management can help ensure solar energy is delivered safely and reliably.

UNDERSTANDING THE TERMINOLOGY

Solar is often used as a shorthand term, but it can refer to several different technologies and project types. A rooftop PV system, a utility-scale solar farm, a solar thermal installation and a concentrated solar power plant all use sunlight, but they do not work in the same way or introduce the same safety considerations. Understanding these differences is useful before looking at where the risks arise.

At a simple level, solar energy involves capturing energy from the sun and converting it into a useful output, usually electricity or heat.

Solar energy: the umbrella term

Solar energy refers to energy from sunlight that can be converted into electricity or heat. It can be used at different scales, from small rooftop installations to large solar farms connected directly to the electricity network [1].

Solar photovoltaic systems

Solar photovoltaic systems, commonly referred to as solar PV, convert sunlight directly into electricity using semiconductor materials within solar cells. When sunlight reaches a PV cell, it excites electrons within the semiconductor material and creates an electrical current. Individual cells are connected to form modules, and modules are then connected in strings and arrays to produce the required electrical output.

Most solar PV systems produce direct current electricity, which is then converted into alternating current using inverters so that it can be used by electrical equipment or exported to the grid [2].

Figure 1 – Solar PV system

Rooftop solar

Rooftop solar systems are installed on buildings, including homes, warehouses, commercial premises, and industrial facilities. These systems can reduce electricity demand from the grid but introduce specific design considerations relating to roof loading, fire safety, access, isolation, and maintenance [2], [8].

Figure 2 – Rooftop solar

Utility-scale solar farms

Utility-scale solar farms are large ground mounted PV installations designed to generate electricity for export to the grid. These projects typically include PV modules, mounting structures, cables, inverters, transformers, switchgear, access tracks, drainage arrangements, and grid connection infrastructure [1], [3].

Figure 3 – Utility-scale solar farm

Floating solar

Floating solar involves installing PV modules on floating structures, usually on reservoirs, lakes, or other water bodies. This can reduce land use pressure but introduces additional considerations relating to buoyancy, anchoring, access, electrical equipment near water, and emergency response [2].

Figure 4 – Floating solar

Agrivoltaics

Agrivoltaics refers to the combined use of land for both solar energy generation and agriculture. Depending on the design, this may allow grazing, crop production, or biodiversity measures to continue alongside solar generation [13].

Figure 5 – Agrivoltaics sheep grazing

Solar-plus-storage

Solar-plus-storage is a commonly used term for solar projects that are co-located or integrated with battery energy storage systems (BESS). This allows electricity generated during sunny periods to be stored and used or exported later.

However, battery storage introduces its own hazard profile, including thermal runaway, fire, toxic gas generation, and emergency response challenges. These risks should be considered separately and not treated as an inherent part of solar PV itself [5].

Figure 6 – Solar farm co-located with BESS

Solar thermal systems

Solar thermal systems use energy from the sun to produce heat rather than electricity. This heat can be used for domestic hot water, space heating or, in some industrial applications, process heat.

Solar thermal is different from solar PV. In a typical solar thermal system, sunlight heats a collector, which transfers heat to a working fluid such as water or a heat transfer fluid. This heated fluid is then circulated to a storage cylinder, heat exchanger, or process system, depending on the application. The main output is therefore thermal energy, rather than electrical power [10].

Figure 7 – Solar thermal system

Concentrated solar power

Concentrated solar power (CSP) generates electricity by using mirrors to focus sunlight onto a central receiver, producing high temperatures that are used to generate power. Unlike photovoltaic (PV) systems, which convert sunlight directly into electricity, CSP first converts solar energy into heat before using a conventional steam turbine or other heat engine to produce electricity [3].

Several CSP technologies are in commercial use, including parabolic troughs, central receiver (solar tower) systems using heliostats, and parabolic dish systems. These technologies require high levels of direct solar radiation and are therefore typically deployed in arid, desert regions. Large-scale CSP developments can be found in countries such as Spain, Morocco, the United Arab Emirates, the United States, and China, where the solar resource is sufficiently intense to make the technology commercially viable [3].

Conventional CSP plants can only generate electricity while sufficient sunlight is available. However, many modern CSP developments also incorporate thermal energy storage, most commonly using molten salts. During periods of strong sunlight, excess thermal energy is stored within insulated molten salt systems before being released later to continue generating electricity after sunset or during periods of cloud cover. This ability to decouple electricity generation from immediate solar availability provides greater operational flexibility and grid stability than conventional CSP alone [4].

From a process safety perspective, CSP presents a very different hazard profile to PV. Hazards may include high-temperature receivers, pressurised steam systems, heat transfer fluids, molten salt storage, rotating mechanical equipment. Potential consequences include fire and explosion, and serious thermal burns. Where thermal energy storage is incorporated, significant quantities of stored heat may remain within the plant long after electricity generation has ceased, requiring careful consideration during operation, maintenance, and emergency response [4].

Figure 8 – Concentrated solar

HOW SOLAR ENERGY SYSTEMS WORK

The way a solar energy system operates depends on the technology used, the scale of the project and the intended end use.

For most solar PV projects, the basic journey is relatively simple:

• Sunlight reaches the PV modules.
• The PV cells convert sunlight into direct current electricity.
• Cables collect and transfer the electricity across the site or building.
• Inverters convert direct current into alternating current.
• Transformers increase the voltage where required.
• Electricity is used locally, exported to the grid or stored in a battery system where one is installed.

Although this appears straightforward, solar projects involve a combination of electrical, structural, civil, environmental, and operational interfaces. These interfaces are often where risk can be introduced if they are not considered early in the design.

For CSP and some solar thermal systems, the energy pathway is different. Sunlight is captured as heat rather than directly converted into electricity. This may involve receivers, heat transfer fluids, thermal storage, steam generation, and rotating equipment. As a result, the safety considerations can be closer to those seen in thermal power or industrial process systems [3], [10].

Solar projects are therefore not just a collection of panels. They are engineered systems that must be designed, constructed, operated, and maintained safely across their full lifecycle.

WHERE THE RISKS ARISE

Solar energy projects vary significantly in scale, location, and design. A domestic rooftop installation, a commercial rooftop system, a ground-mounted solar farm, a floating solar project, and a CSP installation will each have different risk profiles.

Despite these differences, several recurring hazard themes are common across the sector.

Electrical shock and arc flash

Solar PV systems generate electricity whenever they are exposed to sufficient light. This means parts of the system may remain live during daylight, even when the wider electrical system has been isolated.

This can create risks for installers, operators, maintainers, and emergency responders. Direct current systems can be particularly challenging because they may be harder to interrupt safely than alternating current systems.

Electrical shocks, burns, and arc flash can arise from damaged equipment, poor installation, inadequate isolation, water ingress, cable faults, incorrect maintenance activities, or failure to follow safe systems of work [6], [7].

DC arcing

Electrical faults can lead to arcing, overheating, and fire. In solar PV systems, credible sources of fire initiation include damaged cables, loose connections, faulty connectors, inverter faults, poor-quality installation, water ingress, and equipment degradation over time.

Direct current (DC) arcing is a particular concern because, unlike alternating current (AC), DC does not naturally pass through zero volts many times each second. As a result, once established, a DC arc can be much more difficult to extinguish, allowing it to sustain higher temperatures for longer and increasing the likelihood of ignition or equipment damage if faults are not detected and isolated promptly.

The risk is further increased where installation quality is poor, cable management is inadequate, connectors from different manufacturers are mismatched, or inspection and maintenance regimes fail to identify developing faults before they escalate [6], [7].

Fire spread

Solar projects can introduce fire safety challenges, particularly where PV modules are installed on rooftops or close to other critical infrastructure.

On rooftops, PV installations can affect fire spread, firefighter access, roof ventilation, smoke movement, and the ability to isolate electrical systems. In ground mounted solar farms, fire risk may involve inverters, transformers, cable routes, vegetation, fencing, access constraints, or nearby assets.

Emergency responders may also need to consider that PV modules continue generating electricity during daylight, even after isolation of parts of the system. Clear labelling, isolation arrangements, site information, and emergency response planning are therefore important.

High temperature and thermal hazards

While most solar PV projects do not involve high temperature process systems, CSP and some solar thermal technologies can introduce significant thermal hazards.

CSP systems may involve concentrated sunlight, hot receivers, heat transfer fluids, molten salts, steam generation, and pressurised equipment. These systems can create risks associated with burns, fire, loss of containment, overpressure, equipment failure, and maintenance around hot surfaces or stored thermal energy.

Where thermal energy storage is used, hazards may remain even after the sun has set. This means isolation, cooldown, maintenance planning, and emergency response arrangements need to consider stored thermal energy as well as active generation [4].

Structural and weather-related hazards

Solar installations are exposed to environmental conditions throughout their life. Wind, snow, flooding, ground movement, corrosion, and temperature cycling can all affect long-term integrity.

For rooftop systems, the existing structure must be able to support the additional loads from PV modules, mounting systems, ballast, wind uplift, and maintenance access. Poor assessment of roof condition or loading capacity can create structural risks.

For ground mounted systems, pile design, ground conditions, drainage, erosion, and flood risk can affect the stability and reliability of the installation.

For floating solar, anchoring systems, water level changes, wave action, electrical equipment near water, and access for maintenance introduce additional considerations [2], [8].

Construction phase risks

Many of the highest risks on solar projects arise during construction rather than operation.

Construction activities may include site clearance, excavation, piling, lifting operations, temporary works, delivery traffic, electrical installation, working at height, cable pulling, commissioning, and interface work with the grid connection.

On large solar farms, construction may involve multiple contractors working across wide sites, often with simultaneous activities taking place in different areas and temporary access arrangements. This creates risks associated with vehicle movements, plant-person interface, buried services, manual handling, adverse weather, temporary excavations, and coordination between trades.

For rooftop projects, work at height, fragile roofs, lifting materials, edge protection, and safe access are major considerations.

For CSP projects, construction may also involve larger mechanical systems, elevated structures, pressure equipment, thermal storage systems, and more complex commissioning activities [8], [12].

Operations and maintenance risks

Solar assets are long-life systems. Safe performance depends not only on good design and installation, but also on inspection, maintenance, and management of change throughout operation.

Operation and maintenance (O&M) activities may include cleaning modules, inspecting mounting systems, vegetation management, inverter maintenance, thermographic (thermal imaging) surveys, electrical testing, fault finding, and repair.

Risks can arise where access is poor, isolation points are unclear, documentation is incomplete, equipment is difficult to maintain, or degradation mechanisms are not understood. Over time, weathering, corrosion, cable damage, loose connections, vegetation growth, and unauthorised access can all affect safety and reliability.

For CSP and solar thermal systems, maintenance may also involve hot equipment, pressurised systems, heat transfer fluids, rotating equipment, and stored thermal energy [2], [10].

Environmental and community impacts

Solar projects can also create environmental and community impacts if they are not designed and managed properly.

These may include drainage changes, surface water run-off, soil disturbance, glint and glare, visual impact, biodiversity impacts, noise from electrical equipment, construction traffic, and waste from damaged or end-of-life components.

Although these issues may not present an immediate safety risk, they can affect planning, regulatory compliance, stakeholder confidence, and long-term community acceptance [9].

DESIGN AND LIFECYCLE SAFETY CHALLENGE

Solar energy is a mature technology, but maturity should not lead to complacency.

The main safety challenge is not usually that the hazards are unfamiliar. Electrical safety, fire safety, structural integrity, construction risk, safe access, and emergency response are all well-established disciplines. For CSP and solar thermal systems, thermal, and pressure system safety are also well understood.

The challenge is making sure these risks are considered together and managed across the full project lifecycle. For solar projects, this means applying a proportionate safety assurance approach that focuses attention on the most significant risks and on the design decisions that are difficult to change later.

A practical lifecycle approach should ask three simple questions:

• What can go wrong?
• What systems, safeguards or design measures are in place to prevent this or reduce the consequences?
• How will confidence be maintained that these safeguards remain effective through construction, operation and maintenance?

This approach supports the early identification of hazards, the elimination or reduction of foreseeable risks through design, and the clear communication of residual risks to those who will construct, operate, maintain, and respond to the asset.

It is particularly important where solar projects involve multiple interfaces, such as landowners, developers, designers, EPC contractors, grid connection contractors, operators, local authorities, and emergency responders. If these interfaces are not actively managed, risks can fall between design packages or be inherited later by construction and operations teams.

For solar projects, safe design is therefore not just about selecting compliant equipment. It is about ensuring the overall system can be safely constructed, operated, maintained, and eventually decommissioned [11], [12].

REGULATORY AND GOOD PRACTICE EXPECTATIONS

Solar projects sit within a wider framework of health, safety, fire, electrical, construction, planning, and environmental requirements.

Depending on the project type, scale and location, this may include duties relating to construction safety, electrical safety, work at height, fire risk, environmental protection, planning conditions, grid connection requirements, and occupational health and safety.

For larger projects in the UK, the Construction (Design and Management) Regulations 2015 are particularly relevant in ensuring that risks are considered during design and that information is passed between clients, designers, contractors, and operators [12].

Electrical safety requirements, fire safety guidance, grid connection standards, manufacturer instructions, and industry good practice also play an important role in shaping how solar projects are designed, installed, commissioned, and operated.

For CSP and some solar thermal systems, additional expectations may apply depending on the design, including requirements relating to pressure systems, heat transfer fluids, thermal storage, machinery safety, and control of hazardous energy.

However, meeting individual requirements does not automatically mean a project is safe by design. A solar project can appear compliant on paper while still being difficult to construct, operate, maintain, or respond to safely because of poor layout, weak access arrangements, unclear isolation philosophy, poor installation quality, or inadequate emergency response planning.

CONCLUSION

Solar energy has an essential role to play in the transition to net zero. It is a mature and widely understood technology, but it is not risk free.

The main hazards are generally foreseeable: electrical shock, arc flash, fire initiation, structural failure, construction risks, access challenges, environmental impacts, and emergency response constraints. For CSP and some solar thermal systems, high temperatures, pressurised systems, and stored thermal energy will also need to be considered.

Solar projects can be delivered safely when these risks are considered early and managed throughout the asset lifecycle. This means looking beyond the panels themselves and considering the full system: the site, the structure, the electrical design, the people who build and maintain it, and the emergency responders who may need to intervene.

References

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