The shift from steam-based heating systems to electric alternatives marks a significant development in process engineering. Electric heating skid systems offer improved energy efficiency, reduced carbon emissions, and greater operational flexibility, write John Power and John Scott.
Recently, ESI Technologies Group completed its largest electric heating skid system to date, a project that presented unique technical challenges and opportunities for innovation. In this article, lead engineers John Power and John Scott share their insights into the design, construction, and future implications of this next-generation system.
Overcoming technical challenges
Replacing an oversized steam glycol heating skid with an electric system required addressing several critical issues. The previous system was difficult to control at low standby kilowatt values and struggled to respond quickly to peak demand.
To overcome these limitations, the team designed a system that incorporated a thermal buffer tank and electric heater, which demanded close collaboration across multiple disciplines.
Extensive engagement with client stakeholders, fabricators, and electricians during the design phase ensured that both process and mechanical requirements were met. This upfront effort resulted in the most detailed 3D models and drawings the team had ever produced, which significantly reduced issues during construction and streamlined the approval process.
Designing for efficiency and sustainability
Energy efficiency and carbon reduction were central to the design philosophy. By generating heat locally through electric heaters, the system eliminated transmission losses inherent in steam-based systems. This approach not only improved efficiency but also enabled the client to utilise renewable electricity sources, reducing reliance on fossil fuels.
To further optimise performance, the main pumps were equipped with variable frequency drives, allowing precise control of pump speed and energy consumption during low-demand periods. The inclusion of two 5000-litre thermal buffer tanks provided stored heat to meet short-term peak loads, ensuring operational stability.
Additionally, T-Fit insulation shells were selected to minimise energy loss and simplify maintenance, contributing to long-term cost and environmental savings. The system delivers 135kW of electrical heating power, and the buffer tanks can handle operational peaks of approximately 400kW for 10-15 minutes without any heat being added by the heaters themselves.
Testing and validation
Ensuring compliance and performance was a priority throughout the project. Multiple inspections were carried out during construction to confirm alignment with client specifications.
Once assembly was complete, a comprehensive four-day factory acceptance test was conducted, involving a multidisciplinary client team to verify every aspect of the system.
After installation, similar protocols were followed on-site, and the system went through several weeks of testing under various load scenarios to demonstrate its reliability and adherence to industry standards.
Looking ahead
Electric heating systems are expected to play an increasingly important role in future engineering projects. As familiarity with these systems grows, installations may become simpler, with the potential to eliminate secondary heating loops and associated utilities. This simplification could reduce installation times, lower costs, and further enhance efficiency, setting a new benchmark for sustainable process heating solutions.
ESI's project presented unique challenges and offered it opportunities to raise the bar in expertise in the field of energy-efficient and sustainable engineering. Lead engineers John Power, John Scott and Alan Venner answer some key questions about the project, offering an in-depth look into its design, construction, and the future of electric heating skid systems.
Q: What were the primary technical challenges encountered during the design and construction of this large-scale electric heating skid system?
A: “This project presented several technical hurdles, primarily driven by its larger scale and the need to replace an existing, inefficient steam glycol heating skid. The old system was significantly oversized, making it quite difficult to control at low standby kW values and react quickly to high-demand peaks.
“Our solution involved proposing a more efficient system utilising a thermal buffer tank and an electric heater. The size and complexity of this new system necessitated extensive collaboration. We engaged closely with all client stakeholders, encompassing a wide range of disciplines due to the intricate control requirements of the skid. Furthermore, we worked hand in hand with our fabricators and electricians throughout the design phase, focusing on both process and mechanical aspects.
“This intensive upfront engagement paid dividends. The resulting 3D model and subsequent general arrangement and electrical drawings were the most comprehensive we’ve ever produced. This meticulous planning significantly minimised issues during the construction phase, with very few problems arising after the drawings were signed off.”
Q: Can you elaborate on the specific design choices made to enhance energy efficiency and reduce CO₂ emissions in this system?
A: “Energy efficiency and CO₂ emission reduction were central to our design for this skid. Early on in the process design, we identified the critical need for fast-response heating. The decision to employ electric heaters was pivotal here. By generating heat locally, we dramatically reduced the transmission and distribution losses inherent in steam-based systems. This direct heating approach makes the overall skid significantly more energy efficient than using equivalent plant steam power.
“Beyond efficiency, electric heating offers a crucial advantage: it allows our client to leverage any renewably generated electricity they may have available – an option that is not feasible with the currently installed gas boilers and can also cut carbon emissions significantly.
“Further enhancing energy efficiency, the main pumps on the system are equipped with variable frequency drives (VFDs). This allows the control system to precisely regulate pump speed and, consequently, energy consumption when lower heating outputs are required.
“We also considered the entire lifecycle of the system. For instance, we opted for T-Fit insulation shells (onsite installation) which cut energy loss, save space, & simplify maintenance, contributing to both cost and environmental savings.
“The heaters deliver 135kW of heating power, but the system is designed to handle operational peak draws of approximately 400kW for short bursts (about two to five minutes). To accommodate these peaks, a 2 x 5000-litre thermal buffer tank (duty and standby) was included, providing enough stored heat to meet peak loads for about 10 minutes.”
Q: How do you see the evolution of electric skid systems influencing future engineering projects and industry trends?
A: “We anticipate a significant shift towards electric heater operation as engineers and maintenance teams become more familiar with their capabilities. This increased familiarity could lead to simpler installations in the future. Electric heaters have the potential to directly heat heating fluids, potentially eliminating the need for a complex secondary heating side and its associated support utilities and costs. This simplification could streamline designs, reduce installation times, and further enhance overall system efficiency, setting a new standard for future engineering projects and industry trends.”
Q: Can you describe the testing and validation processes undertaken to ensure the system meets industry standards and client specifications?
A: “Ensuring compliance, quality and performance is paramount. Throughout the construction phase, both the skid and the electrical panels were subject to multiple inspections to confirm alignment with client expectations.
“Upon completion of the full skid assembly, a comprehensive four-day factory acceptance test (FAT) was conducted at the fabrication workshop. This involved a multidisciplinary team from the client meticulously verifying every aspect of the system. Post-installation on site, a reduced but similar protocol was executed to ensure everything was in order.
"Once the site utilities and pipework (which were independently tested) are connected to the skid, the system will undergo several weeks of thorough testing under various load scenarios to unequivocally prove its performance and ensure it meets all industry standards and client specifications.”
Authors:
John Scott has been a product specialist sales engineer at ESI Technologies Group for 34 years, with experience in designing and specifying pump, skid, and heat exchanger systems. His career began eight years previously, in piping design for major pharmaceutical companies, encompassing both utility and process trains, then moving into engineered systems with ESI for pharma, chemical, biotech, and industrial sectors. A graduate of RTC (now MTU) in mechanical and electrical draughtsmanship.
John Power, BEng BSc MIEI, is a project engineer at ESI with more than eight years of experience in skid and heat exchanger system design, following six years in the fluid power industry. He specialises in temperature control and pumping solutions for pharmaceutical and biotech industries. A graduate of CIT (now MTU) in process plant technology and mechanical engineering, he is a member of Engineers Ireland.