The objectives of steam raising plant are straightforward: to release the energy in the input fuel as efficiently as possible, to transfer that energy to water to generate steam, and to separate the steam from the water for use in processes requiring heat energy.
In this short piece, Fulton’s UK Sales & Export Manager Dave Dolan looks at how the suitability of hybridisation with gas and electric energy sources depends greatly on the design and operational characteristics of the equipment, particularly in differentiating between steam boilers and steam generators.
Why Steam Boilers are Ideal for Hybridisation
Shell-type steam boilers, such as Fulton’s VSRT, are particularly well-suited to hybridisation with both gas and electric energy sources, in fact, the company is launching its VSRT-E hybrid steam boiler in 2025. These boilers are constructed as pressure vessels with a relatively large water volume, which provides operational flexibility and stability. The large water content allows the boiler to release flash steam to meet system demands, even when the burner is not firing.
In a hybrid gas/electric configuration, a boiler can operate with gas burners to handle high-demand scenarios, ensuring rapid and efficient steam generation. During periods of low demand or off-peak operation, electric heating elements can take over, maintaining pressure and steam output without requiring the gas burner. This dual-energy approach allows operators to switch between gas and electric energy sources based on economic or environmental considerations, emphasised when comparing the environmental impact of a Hydrogen blend ready and electric boiler against a conventional gas and oil dual-fuel option. Moreover, the boiler’s ability to store and release steam ensures a consistent supply, even when transitioning between energy sources. Its capacity to respond to varying steam loads further enhances its suitability for hybrid systems.
Why Steam Generators Cannot Be Hybridised
In contrast, steam generators are fundamentally unsuitable for hybridisation due to their design and operation. Steam generators rely on very low water content and the continuous pumping of water through tightly wound steel coils. This design, while effective for rapid start-up and compactness, presents several limitations.
Unlike shell boilers, steam generators lack a large water reserve for flash steam production. Without an active burner, they cannot generate steam, as the system depends entirely on real-time heating. Incorporating dual heating sources, such as gas and electric, would introduce significant challenges, including uneven heating, unstable operation, and potential issues with steam quality. Moreover, steam generators are less capable of adapting to fluctuating steam loads, as their continuous operation design limits flexibility, making them incompatible with the requirements of hybrid systems.
Conclusion
Shell-type steam boilers are inherently suited to hybrid gas/electric configurations because of their large water content, operational flexibility, and ability to store and release steam. These features make hybridisation both practical and advantageous. On the other hand, the low water content and real-time heating design of steam generators render hybridisation unfeasible. Thus, while hybrid gas/electric systems are a valuable option for steam boilers, they cannot be applied to steam generators.
For further information on the VSRT and VSRT-E, call Fulton on 0117 972 3322 or email