In today’s world, businesses rely heavily on digital infrastructure and uninterrupted operations. Power outages, even those lasting just a few seconds, can cause major financial losses, data corruption, or critical safety issues.
Two of the most common backup solutions are:
- Diesel Rotary Uninterruptible Power Supply (DRUPS) – a battery-free solution using diesel engines and kinetic energy.
- Diesel generator combined with a static UPS – the traditional setup using batteries for short-term bridging.
What is DRUPS?
A DRUPS system integrates a diesel engine, flywheel (kinetic energy module), and generator. When the utility grid fails, the flywheel instantly provides energy until the diesel engine reaches full power.
Advantages of DRUPS:
- Battery-free design – no battery replacement or disposal needed.
- Instant no-break power transition.
- Compact and modular footprint.
- Lower maintenance costs compared to battery systems.
- High short-circuit capacity and excellent power quality.
Read also: Diesel Generators: Future Prospects and Regulatory Insights
What is a Diesel Generator with UPS?
A diesel generator with UPS setup combines a static UPS system with batteries for short-term backup, while the diesel generator starts up to take over the load.
Advantages of this solution:
- Lower upfront investment compared to DRUPS.
- Flexible in terms of UPS technology and battery capacity.
- Components can be upgraded independently (generator or UPS).
Check out: Diesel generator brochure
Key Differences Between DRUPS and Diesel Generators with UPS
Response Time
One of the standout features of DRUPS is its instantaneous response time. The flywheel can provide full power immediately, ensuring there is no interruption in the power supply. This rapid response is critical for environments where even a brief power loss could have serious consequences.
In comparison, a UPS system typically has a slight delay and a longer delay before the diesel generator starts, which may not be suitable for all applications.
Sustainability
In terms of sustainability, DRUPS systems present clear environmental benefits because no batteries are required and there is therefore no need for replacement over time. Additionally, their high efficiency minimizes power loss, further reducing energy consumption. For organizations prioritizing sustainability, DRUPS offers a more eco-conscious choice, contributing to lower carbon footprints and reduced operational costs.
Space and Modularity
DRUPS systems are known for a compact design, often requiring less space than a separate diesel generator and UPS system at the same power/capacity. This can be a significant advantage in environments where space is at a premium.
Discover: Secure critical operations - DRUPS
Maintenance and Reliability
Maintenance requirements can differ significantly between the two systems. DRUPS systems are generally low-maintenance and is only carried out on the diesel engine and lubricating of bearings in flywheel and alternator. Bearings in the flywheel and alternator have a 10-year design life. The use of a flywheel instead of batteries will lead to lower overall operational costs and higher reliability over time.
On the other hand, diesel generators with UPS require regular UPS and battery maintenance and replacement, as UPS and batteries degrade over time. This additional maintenance can add to the operational costs and complexity of managing the system.
Cost Considerations
Cost is always a critical factor in choosing a backup power solution. DRUPS systems tend to have a higher initial cost due to their advanced technology and integration. However, their lower maintenance costs and longer lifespan can make them more cost-effective in the long run, especially for mission-critical applications.
Diesel generators with UPS, while potentially cheaper upfront, may incur higher operational costs due to UPS and battery maintenance and the need for more frequent component replacements.
Short circuit capabilities
The DRUPS system offers substantially higher short circuit capabilities than conventional static UPS systems, ensuring better protection for critical infrastructure. This enhanced capability reduces the risk of downtime and damage during power disturbances.
Read more: BOS Power donates generator set to provide vital power for Ukrainians
Emerging Trends and Developments
The backup power industry is evolving rapidly, driven by stricter regulations, sustainability goals, and the rising demand for resilient infrastructure. Several key developments are shaping the choice between DRUPS and diesel generator with UPS systems:
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Sustainability and regulation: The EU Battery Regulation (2023) places new requirements on battery use and disposal, strengthening the case for battery-free solutions like DRUPS.
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Alternative fuels: Modern diesel engines are increasingly compatible with renewable fuels such as HVO100, enabling up to 90% reductions in lifecycle CO₂ emissions depending on the feedstock (IEA, 2024 - World Energy Outlook 2024 and Biodiesel and HVO production overview for key global markets, 2019-2025).
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Data center expansion: Global data center capacity is forecast to grow by around 15% annually through 2030, fueling demand for highly reliable no-break power solution. (Uptime Institute, 2024).
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Hybrid systems: Operators are exploring combinations of DRUPS, diesel generators, and battery energy storage to achieve both resilience and sustainability.
How to Choose the Right Solution
When evaluating options, consider the following factors:
- Criticality: Do you require absolute no-break power?
- Budget: Can you afford higher upfront investment for lower lifetime costs?
- Space: Is physical footprint a limiting factor?
- Sustainability profile: Is reducing battery waste and CO₂ emissions a priority?
Key Takeaways
- DRUPS is ideal for mission-critical facilities demanding no-break operation, sustainability, and low lifecycle costs.
- Diesel generator with UPS is suitable where cost and flexibility matter more than instant switchover.
- New technologies such as HVO fuels and hybrid systems provide greener, future-proof alternatives.
- Industry drivers such as stricter regulations and rapid data center growth make DRUPS increasingly relevant.
Contact us to discuss which solution fits your facility.
